Polymer films are widely used as biomaterials, electronic devices, food packaging materials and gas separation membranes. In practice, cross-linking is an effective method to enhance their stability and increase the strength of these films. However, conventional cross-linked polymer films cannot degrade under mild conditions. Herein, we fabricated two cross-linkable, yet biodegradable, polymer films of ~0.2 mm via solution casting using cinnamate-grafted polycaprolactones, namely: a poly((α-(cinnamoyloxymethyl)-1, 2, 3-triazol) caprolactone) (PCTCL₁₃₃) homopolymer and a poly(caprolactone-stat-CTCL) (P(CL₁₅₆-stat-CTCL₂₈)) copolymer. The successful syntheses of the polymers were confirmed via proton nuclear magnetic resonance (¹H NMR) spectroscopy, size exclusion chromatography (SEC), and Fourier transform infrared (FT-IR) spectroscopy. The PCTCL homopolymer appeared as a transparent film, owing to its side groups that impede its crystallinity; in contrast, the copolymer film appeared translucent, owing to its PCL segments that are easily crystallized. The cinnamate groups facilitated the cross-linking of the polymer films when irradiated by ultraviolet (UV) light; this is indicated by its insoluble character in tetrahydrofuran, which is a good solvent for both polymers. SEC analysis indicated that a fraction of the P(CL₁₅₆-stat-CTCL₂₈) film remained un-cross-linked after irradiation, owing to its crystalline structure. In contrast, UV irradiation caused the PCTCL homopolymer film to become homogeneously cross-linked, which exhibited a cross-linking density of 49% after 2 h as indicated by the ¹H NMR results. Thermogravimetric analysis (TGA) indicated that cross-linking of the PCTCL films caused a minimal change in thermal stability. Both the cross-linked polymer films were able to degrade upon the addition of a modest amount of concentrated hydrochloric acid, as confirmed by SEC and ¹H NMR. However, the degradation rate significantly decreased after cross-linking, thereby indicating its tunable character that can be altered by varying the cross-linking density. In addition, the rate of degradation can be adjusted upon varying the fraction of cross-linked PCTCL groups in the copolymer. In principle, treating the polymer films with sufficient amounts of acid could form degradation products with molecular weights less than 300 g∙mol⁻¹. To further explore the mechanical properties of such materials, we investigated the correlation between the initial concentration used for solution casting and the Young's modulus of the film by employing molecular dynamics simulations. These results indicate that tougher films are prepared when using more concentrated polymer solutions, owing to a higher degree of chain entanglement. In summary, the prepared films with tunable degradability are promising materials for biomedical applications. In principle, this platform could be utilized in hydrogels and coating materials for a broad scope of applications.

Solid oxide fuel cell (SOFC) with high energy conversion efficiency, low pollutant emission, and good fuel adaptability has witnessed rapid development in recent years. However, the commercialization of SOFC remains limited by constraints of performance and stability. Electrochemical impedance spectroscopy (EIS) can distinguish ohmic impedance caused by ion transport from polarization impedance related to electrode reaction; it has been widely used in the research of performance and stability as an efficient on-line characterization technology. The physical/chemical processes involved in EIS overlap significantly and can be decomposed by the distribution of relaxation times (DRT) method which does not depend on prior assumptions. Since industrial large-size SOFC is vulnerable to the influence of inductance and disturbance when testing EIS, its EIS analysis is rarely studied and mostly based on the research results of cells with smaller electrode active area. To further elucidate the impedance spectrum of industrial large-size SOFC under actual working conditions, the EIS of industrial-size (10 cm × 10 cm) anode-supported planar SOFC was systematically tested over a broad temperature and anode/cathode gas composition range. First, the quality of the impedance data was examined by performing a Kramers-Kronig test. The residuals of real and imaginary data were within the range of ±1%, indicating good data quality. Then, the DRT method was adopted to parse the EIS data. By comparing and analyzing the DRT results under different conditions, the corresponding relationships between each characteristic peak in the DRT results and the specific electrode process in the SOFC were revealed. The characteristic frequencies were separated into 0.5-1, 1-30, 10-30, 1 × 10²-1 × 10³, and 1 × 10⁴-3 × 10⁴ Hz regions, corresponding to gas conversion within the anode, gas diffusion within the anode, oxygen surface exchange reaction within the cathode, charge-transfer reaction within the anode, and oxygen ionic transport process, respectively. In this study, the identification of each electrode process in industrial large-size SOFC is realized, indicate that the gas conversion process in large-size SOFC with larger active area and smaller flows cannot be ignored compared with the cells with smaller electrode active area. The method followed and the results obtained have a universal quality and can be applied to the in situ characterization, online monitoring, and degradation mechanism research of SOFC, thus laying a foundation for the optimization of the performance and stability.

Surfactants are widely applied for promoting miscibility and reducing interfacial tension between oil and water phases because of their remarkable amphiphilic morphology. Along with development and popularization of tertiary oil recovery techniques, surfactants play a significant role in crude oil exploitation. Among the various tertiary oil recovery techniques, supercritical CO₂-enhanced oil recovery is a promising method for improving oil recovery. However, the establishment of CO₂-enhanced oil recovery brought new requirements and challenges to traditional surfactant research and development, especially for molecular design. In this method, the reduction of the minimum miscibility pressure between supercritical CO₂ and crude oil is required to achieve miscible flooding—an important means to enhance oil recovery. Therefore, a novel miscible flooding agent that exhibits oil-water miscibility analogous to conventional surfactants is desirable for this method. Meanwhile, a conspicuous difference of polarity matching the high polarity of H₂O molecule against low polarity of alkane molecule, which is the essential feature of traditional surfactant, won't suit this case well due to a medium polarity of CO₂ molecule. According to previous work done in our laboratory, surfactants with multiple ester groups considerably reduce the minimum miscibility pressure between supercritical CO₂ and crude oil. Therefore, inspired by the "oil-water-amphiphilic molecules" design, herein, we replaced the hydrophilic moiety with multiple ester groups and designed a new type of "oil-CO₂ amphiphilic molecule" as a miscible flooding agent, which is composed of an alkane tail and multiple ester groups as the lipophilic and CO₂-philic groups, respectively. In the strategy based on the proposed agent, the number of ester groups and the length of the alkane tail are the main parameters. In addition, we optimized the molecular structure of the proposed agent, CAA8-X, which comprises cetyl and acetyl sucrose esters as the lipophilic and CO₂-philic groups, respectively. We verified that the as-synthesized agent can remarkably reduce the minimum miscibility pressure between supercritical CO₂ and various types of oil samples, including kerosene, white oil, and crude oil from the Changqing region. The crude oil-CO₂ minimum miscibility pressure reduction ratio was 20.5% as measured by the vanishing interfacial tension method and the slim tube test. In this study, we also established a method called the rising height method to measure the minimum miscibility pressure with significantly reduced time and equipment cost. Furthermore, to demonstrate the mechanism of this miscible flooding agent for CO₂-enhanced oil recovery, the affinity between the CO₂-philic group and molecular CO₂ was investigated via molecular dynamics simulation. The results indicated that the "oil-CO₂ amphiphilic molecule" can reduce oil-CO₂ interfacial tension because of lower affinity potential energy between the CO₂-philic group and molecular CO₂.

The diameter-controlled growth of single-walled carbon nanotubes (SWNTs) is one of the key issues of SWNT synthesis and application. To guarantee that SWNTs grow with desired diameters, it is necessary to control catalyst size and modulate growth conditions. SWNTs with diameters of 0.9–1.2 nm are highly desirable for near-infrared fluorescence bioimaging and serving as effective single-photon sources for the development of quantum devices. Herein, we used an FeCo/MgO catalyst to grow bulk SWNTs with diameters in the range and studied the influence of catalysts and chemical vapor deposition (CVD) growth conditions on the diameter of SWNTs. The preparation of catalyst precursors is a key step in obtaining catalyst nanoparticles of small size. In the impregnation process, we used three different types of metal salts, namely, sulfates, acetates, and nitrates, to prepare the catalysts. The metal sulfates, which exhibit the weakest hydrolysis ability, were found to grow SWNTs with the smallest diameters. Lowering the immersion pH, which suppresses the hydrolysis of metal ions, was also favorable for growing smaller SWNTs. Moreover, the addition of complexing agent molecules such as ethylenediaminetetraacetic acid during the impregnation process, which inhibits the hydrolysis of metal ions as well, further confined the diameter distribution of the resultant SWNTs. During the solution drying process, metal salts hydrolyze into metal hydroxides and oxides. Under mild hydrolysis conditions, the produced hydroxide and oxide particles are smaller and more likely to be uniformly distributed on the surface of the supports. Therefore, it is more favorable to produce catalysts with controlled sizes under mild hydrolysis conditions, which are preferred for diameter control of the resultant SWNTs. In the CVD growth process, we used either ethanol or methane as the carbon source and found that, under our experimental conditions, the SWNTs grown from ethanol had smaller diameters than those from methane. The hydrogen content in the CVD process also affects diameter distribution of SWNTs. As the carbon-to-hydrogen ratio decreased, SWNTs with larger diameters disappeared, and the number of SWNTs with smaller diameters increased. During the CVD process, the carbon-to-hydrogen ratio determines the carbon feeding rate to the catalysts. At a low carbon feeding rate, catalysts of large sizes are underfed and unable to grow SWNTs, whereas smaller catalysts are in a favorable condition for growth. Therefore, the average diameter of the SWNTs decreased as the carbon-to-hydrogen ratio decreased.

Quantum dot light-emitting diodes (QLEDs) constitute the next-generation display technology because of their wide color gamut, narrow emission spectrum, adjustable emission wavelength, and ease of solution processability. With the development of novel material and device preparation techniques, the QLEDs not only show an external quantum efficiency (EQE) of more than 20% in red, green, and blue (primary color) devices, but also achieve 100% Rec.2020 (recommendation standard for ultrahigh-resolution display) color gamut coverage. However, the future commercialization of QLEDs is still a challenge. The T95 lifetime (defined as 95% time for the luminance to decay to the initial value L₀ = 1000 cd·m^-2) of red, green, and blue QLED devices is significantly lower than that of commercially available organic light-emitting diodes (OLEDs). This is ascribed to the lacking of understanding and argument to hypothesis of degradation mechanisms. A QLED is a sandwich structure composed of a quantum dot (QD) emitter layer, carrier transport layer, and electrode layer. The QLED works on the principle of electroluminescence: electrons and holes injected from the electrodes on both sides of the device cross multiple interfaces and reach the QD emitter layer to undergo radiation recombination. Generally, the QD emitter layer adopts the structure of a wide-band gap shell wrapped around a narrow band-gap core. Because of the deep valence band maximum, the hole injection barrier is higher, and the hole injection efficiency is reduced. This not only disturbs the injection balance but also leads to the accumulation of interfacial holes, which is one of the important factors affecting the efficiency and life of the device. Past studies have attempted to understand charge accumulation behavior in QLEDs by predicting the interfacial energy band structure, and there are very few reports on the direct measurement of charge accumulation. In this work, we built a charge extraction circuit to investigate the charge accumulation behavior before and after aging in a prototype red QLED. In the fresh red QLEDs, the number of accumulated charges gradually increased with the driving current density and tended to saturate above turn-on current density. In the aged red QLEDs, the accumulated charges increased with a decrease in luminance. Our method to investigate the charge accumulation behavior developed can be extended to various kinds of LEDs, such as OLEDs and perovskite LEDs, thus providing insight into their working mechanism.

Photocatalytic hydrogen production is an effective strategy for addressing energy shortage and converting solar energy into chemical energy. Exploring effective strategies to improve photocatalytic H₂ production is a key challenge in the field of energy conversion. There are numerous oxygen vacancies on the surface of non-stoichiometric W₁₈O₄₉ (WO), which result in suitable light absorption performance, but the hydrogen evolution effect is not ideal because the band potential does not reach the hydrogen evolution potential. A suitable heterojunction is constructed to optimize defects such as high carrier recombination rate and low photocatalytic performance in a semiconductor. Herein, 2D porous carbon nitride (PCN) is synthesized, followed by the in situ growth of 1D WO on the PCN to realize a step-scheme (S-scheme) heterojunction. When WO and PCN are composited, the difference between the Fermi levels of WO and PCN leads to electron migration, which balances the Fermi levels of WO and PCN. Electron transfer leads to the formation of an interfacial electric field and bends the energy bands of WO and PCN, thereby resulting in the recombination of unused electrons and holes while leaving used electrons and holes, which can accelerate the separation and charge transfer at the interface and endow the WO/PCN system with better redox capabilities. In addition, PCN with a porous structure provides more catalytic active sites. The photocatalytic performance of the sample can be investigated using the amount of hydrogen released. Compared to WO and PCN, 20%WO/PCN composite has a higher H₂ production rate (1700 μmol·g^-1·h^-1), which is 56 times greater than that of PCN (30 μmol·g^-1·h^-1). This study shows the possibility of the application of S-scheme heterojunction in the field of photocatalytic H₂ production.

Constructing an efficient and stable heterojunction photocatalyst system is a promising approach to achieve solar-driven water splitting to produce hydrogen. In this work, a novel Mn_0.2Cd_0.8S@CoAl LDH (MCCA) S-scheme heterojunction was successfully prepared through the efficient coupling of Mn_0.2Cd_0.8S nanorods and CoAl LDH nanosheets, employing a physical mixing method. The photoluminescence and photocurrent-time response results demonstrated that the internal electric field of the constructed MCCA S-scheme heterojunction could successfully accelerate charge separation and electron transfer between the Mn_0.2Cd_0.8S interface and the CoAl LDH. Critically, the introduction of the CoAl LDH effectively inhibited the recombination of photogenerated electrons and holes, thereby improving the photocatalytic hydrogen production activity of Mn_0.2Cd_0.8S. A maximum H₂ production of 1177.9 μmol in 5 h was obtained with MCCA-3. This represents a significant improvement compared to what can be achieved with the pure Mn_0.2Cd_0.8S nanorods and CoAl LDH nanosheets individually. This work provides a simple and effective approach for the rational design of S-scheme heterojunction photocatalysts for photocatalytic hydrogen production.

Throughout the twentieth century, temperatures climbed rapidly as the use of fossil fuels proliferated and greenhouse gas levels soared. Thus, the need to develop environmentally friendly energy sources to replace traditional fossil fuels is urgent. Clean and highly efficient, hydrogen is considered the most promising energy source to replace traditional fossil fuels. The production of hydrogen by photocatalytic water splitting is environmentally friendly, and is considered the most promising method for producing hydrogen energy. Enhancing the separation efficiency of photogenerated electron-hole pairs has been identified as a key milestone for constructing high-efficiency photocatalysts. However, the construction of efficient and stable hydrogen-evolution photocatalysts with highly dispersed cocatalysts remains a challenge. Here, we succeeded, for the first time, in fabricating P-doped CNS (PCNS) with a highly dispersed non-noble trimetallic transition metal phosphide Co_0.2Ni_1.6Fe_0.2P cocatalyst (PCNS-CoNiFeP), by a one-step in situ high-temperature phosphating method. Remarkably, the CoNiFeP in PCNS-CoNiFeP demonstrated no aggregation and high dispersibility compared with CoNiFeP prepared by the traditional hydroxide-precursor phosphating method (PCNS-CoNiFeP-OH). X-ray diffraction, X-ray photoelectron spectroscopy, element mapping images, and high-resolution transmission electron microscopy results demonstrate that PCNS-CoNiFeP was successfully synthesized. The UV-Vis absorption results indicate a slight increase in absorbance for PCNS-CoNiFeP in the 200–800 nm wavelength region compared with that of PCNS. Photoluminescence spectroscopy, electrochemical impedance spectroscopy, and photocurrent results demonstrated that CoNiFeP cocatalysts could effectively promote the separation of photogenerated electron-hole pairs and accelerate the migration of carriers. The linear sweep voltammetry results also demonstrate that the CoNiFeP cocatalyst loading could significantly decrease the overpotential of CNS. Therefore, the maximum hydrogen evolution rate of PCNS-CoNiFeP was 1200 μmol·h^-1·g^-1, which was approximately four times higher than that of pure CNS-Pt (320 μmol·h^-1·g^-1) when using TEOA solution as a sacrificial agent. The apparent quantum efficiency of PCNS-CoNiFeP was 1.4% at 420 nm. The PCNS-CoNiFeP also exhibited good stability during the photocatalytic reaction. In addition, the TEM results indicate that CoNiFeP with a size of 6–8 nm are highly dispersed on the PCNS surface. The highly dispersed CoNiFeP demonstrated better charge-separation capacity and higher intrinsic electrocatalytic hydrogen-evolution activity than the aggregated CoNiFeP. Thus, the hydrogen evolution rate of aggregated CoNiFeP-PCNs (300 μmol·h^-1·g^-1) was much lower than that of PCNS-CoNiFeP. Furthermore, P doping of CNS could improve electric conductivity and charge transport. It is expected that loading highly dispersed CoNiFeP and P doping could be extended to promote photocatalytic hydrogen production using various photocatalysts.

With rapid industrialization, issues pertaining to the environment and energy have become an alarming concern. Photocatalytic water splitting is considered one of the most promising green technologies capable of resolving these issues, as it can convert solar energy into chemical energy and have a positive impact on the realization of "carbon neutrality". Current research focuses on the development of highly efficient catalysts to improve the photocatalytic H₂-production activity. Transition metal phosphides and sulfides are often used as photocatalysts owing to their low H₂-evolution overpotential and excellent electrical conductivity. Among them, Ni₂P and NiS have generally been used independently during photocatalytic H₂ production; however, it is necessary to study the synergistic effect when they are combined as a dual cocatalyst. In this work, we successfully prepared a Ni₂P-NiS dual cocatalyst for the first time via a simple hydrothermal method using red phosphorus (RP) and thioacetamide (C₂H₅NS) as the sources of P and S. Ni₂P-NiS was then introduced to the surface of g-C₃N₄ nanosheets through solvent evaporation to create a Ni₂P-NiS/g-C₃N₄ heterojunction. Furthermore, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), ultraviolet-visible spectrophotometry (UV-Vis), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), linear sweep voltammetry (LSV), Mott-Schottky (M-S), and electrochemical impedance spectroscopy (EIS) were used to reveal the crystal structures, morphologies, element compositions, and photoelectric characteristics of the samples; thus, it was demonstrated that Ni₂P-NiS was successfully deposited on the surface of g-C₃N₄ and that together they exhibited better activity than their monomers. Moreover, the optimized 15% Ni₂P-NiS/g-C₃N₄ composite exhibits a H₂ generation rate of 6892.7 μmol·g^-1·h^-1, which is about 46.1, 7.5 and 4.4 times higher than that of g-C₃N₄ (150 μmol·g^-1·h^-1), 15% NiS/g-C₃N₄ (914.5 μmol·g^-1·h^-1), and 15% Ni₂P/g-C₃N₄ (1565.9 μmol·g^-1·h^-1), respectively. In addition, photoelectric performance tests show that Ni₂P-NiS/g-C₃N₄ has a stronger photocurrent intensity, smaller charge-transfer resistance, more positive H₂-evolution overpotential, and better charge-separation ability than the individual components (i.e., Ni₂P and NiS), suggesting that the coexistence of Ni₂P and NiS can further boost the activity of g-C₃N₄ during H₂ evolution compared with their monomers. This is mainly due to the Schottky barrier effect between Ni₂P-NiS nanoparticles and g-C₃N₄ nanosheets, which can greatly promote charge separation and charge transfer at their interface. Additionally, Ni₂P-NiS can reduce the H₂-evolution overpotential, leading to the increased surface kinetics of H₂ evolution. This work offers a promising approach to obtaining a highly active and stable noble-metal-free dual cocatalyst for photocatalytic H₂ production.

Catalytic reduction of CO₂ to CO has been considered promising for converting the greenhouse gas into chemical intermediates. Compared to other catalytic methods, photocatalytic CO₂ reduction, which uses solar energy as the energy input, has attracted significant attention because it is a clean and inexhaustible resource. Therefore, using high-performance photocatalysts for effective CO₂ reduction under mild reaction conditions is an active research hotspot. However, several current photocatalysts suffer from low solar energy conversion efficiency due to the extensive charge recombination and few active sites, leading to low CO₂ reduction efficiency. Generally, constructing an S-scheme heterojunction can not only promote charge separation but also help maintain strong redox ability. Therefore, the S-scheme heterojunction is expected to help in achieving high conversion activity and CO₂ reduction efficiency. Here, 2D tetragonal BiOBr_0.5Cl_0.5 nanosheets and hexagonal WO₃ nanorods were prepared using a simple hydrothermal synthesis method, and the 2D/1D BiOBr_0.5Cl_0.5 nanosheets/WO₃ nanorods (BiOBr_0.5Cl_0.5/WO₃) S-scheme heterojunction with near infrared (NIR) light (> 780 nm) response were prepared via the electrostatic self-assembly method for the photocatalytic CO₂ reduction. Following characterization and analysis, including diffuse reflectance spectra (DRS), Mott-Schottky plots, transient photocurrent response, time-resolution photoluminescence spectrum (TRPL), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and electron spin resonance (ESR) measurements, it can be demonstrated that an S-scheme carrier transfer route was formed between the 2D BiOBr_0.5Cl_0.5 nanosheets and 1D WO₃ nanorods. Driven by the internal electric field, which was formed between the two semiconductors, electron migration was boosted, thus inhibiting the recombination of photogenerated carriers, while the stronger redox ability was maintained, thus providing good reduction efficiency over BiOBr_0.5Cl_0.5/WO₃ composite in CO₂ reduction. In addition, the 2D/1D nanosheet/nanorod structure allowed for enhanced interface contact with abundant active sites, which favored charge separation and increased photocatalytic activity. Furthermore, the amount of WO₃ nanorods added during the preparation of the composites was altered, which led to the optimal amount of 5% (w, mass fraction) for the photocatalytic CO₂ reduction. As a result, the BiOBr_0.5Cl_0.5/WO₃ composite exhibited superior photocatalytic reduction performance with a CO yield of 16.68 μmol·g^-1·h^-1 in the presence of any precious metal cocatalyst or sacrificial agent, which was 1.7 and 9.8 times that of pure BiOBr_0.5Cl_0.5 and WO₃, respectively. In addition, the BiOBr_0.5Cl_0.5/WO₃ composite provided continuously increased CO yields with excellent selectivity under full-spectrum light irradiation, suggesting good photocatalytic stability. This work describes a novel idea for the construction of 2D/1D S-scheme heterojunction photocatalysts for efficient CO₂ reduction.

The rational interface tailoring of nanosheets on hollow spheres is a promising strategy to develop efficient photocatalysts for hydrogen production with solar energy. Among the various photocatalyst materials, metal sulfides have been extensively researched because of their relatively narrow band gap and superior visible-light response. ZnIn₂S₄ is a layered ternary chalcogenide semiconductor photocatalyst with a tunable band gap energy (approximately 2.4 eV). Among various metal sulfide photocatalysts, ZnIn₂S₄ has gained considerable attention. However, intrinsic ZnIn₂S₄ only exhibits a relatively moderate photocatalytic activity, which is mainly owing to the high recombination and low migration rate of photocarriers. Loading cocatalysts onto semiconductor photocatalysts is an effective way to improve the performance of photocatalysts, because it can not only facilitate the separation of electron-hole pairs, but also reduce the activation energy for proton reduction. As a ternary transition metal sulfide, NiCo₂S₄ features a high electrical conductivity, low electronegativity, excellent redox properties, and outstanding electrocatalytic activity. Such favorable characteristics suggest that NiCo₂S₄ can expedite charge separation and transfer, thereby promoting photocatalytic H₂ production by serving as a cocatalyst. Moreover, both NiCo₂S₄ and ZnIn₂S₄ possess the ternary spinel crystal structure, which may facilitate the construction of NiCo₂S₄/ZnIn₂S₄ hybrids with tight interfacial contact for an enhanced photocatalytic performance. Herein, ultrathin ZnIn₂S₄ nanosheets were grown in situ on a non-noble-metal cocatalyst, namely NiCo₂S₄ hollow spheres, to form hierarchical NiCo₂S₄@ZnIn₂S₄ hollow heterostructured photocatalysts with an intimately coupled interface and strong visible light absorption extending to ca. 583 nm. The optimized NiCo₂S₄@ZnIn₂S₄ hybrid with a NiCo₂S₄ content of ca. 3.1% exhibited a high hydrogen evolution rate of 78 μmol·h^-1, which was approximately 9 times higher than that of bare ZnIn₂S₄ and 3 times higher than that of 1% (w, mass fraction) Pt/ZnIn₂S₄. Additionally, the hybrid photocatalysts displayed good stability in the reaction. Photoluminescence and electrochemical analysis results indicated that NiCo₂S₄ hollow spheres served as an efficient cocatalyst for facilitating the separation and transport of light-induced charge carriers as well as reducing the hydrogen evolution reaction barrier. Finally, a possible reaction mechanism for the photocatalytic hydrogen evolution was proposed. In the NiCo₂S₄@ZnIn₂S₄ composite photocatalyst, the NiCo₂S₄ cocatalyst with high electrical conductivity favorably accepts the photoinduced electrons transferred from ZnIn₂S₄ and then employs the electrons to reduce protons for H₂ production on the reactive sites. Concurrently, the photogenerated holes are trapped by TEOA that acts as a hole scavenger to accomplish the photoredox cycle. This study provides guidance for the fabrication of hierarchical hollow heterostructures based on nanosheet semiconductor subunits as remarkable photocatalysts for hydrogen production.

With the rapid development of industrial technology, a large number of organic pollutants are routinely released into the environment, which has caused serious problems. Semiconductor photocatalysis is an environmentally-friendly and effective method to degrade and remove typical pollutants, and photocatalysts play a key role in the application of this technology. Therefore, various semiconductor materials have been tried and used in the field of pollutant removal. Graphite carbon nitride (g-C₃N₄) has attracted great interest because of its two-dimensional layered structure and good visible light response range. Owing to a narrow bandgap, adjustable band structure, and high physicochemical stability, g-C₃N₄ absorbs wavelengths up to 450 nm in the visible spectrum, leading to an opportunity for visible-light photocatalytic performance. Nevertheless, there are still some drawbacks that limit the photocatalytic efficiency of g-C₃N₄ in the removal of antibiotics and dyes under visible light, such as the rapid recombination of photoinduced charges and the weak oxidation capacity of holes. To advance this promising photocatalytic material, multiple methods have been tried to optimize the electronic band structure of g-C₃N₄, such as doping with various elements, morphology control, and functional group modification. Recently, a novel type of Step-scheme (S-scheme) heterojunction composed of two n-type semiconductor photocatalysts has been proposed, which can utilize a more positive valance band and a more negative conduction band. It was demonstrated that the formation of S-scheme heterojunctions is a valid way to increase photocatalytic activity of g-C₃N₄. Herein, novel 0D/2D Bi₄V₂O₁₁/g-C₃N₄ S-scheme heterojunctions were prepared by a simple in situ solvothermal growth method. The Bi₄V₂O₁₁/g-C₃N₄ composites displayed a high photocatalytic activity through the removal of oxytetracycline (OTC) and Reactive Red 2. In particular, the BVCN-50 composite showed the highest degradation efficiency for OTC of 74.1% and for Reactive Red 2 of 84.2% with ·O₂^- as the primary active species. This highly improved photocatalytic performance can be ascribed to the generation of S-scheme heterojunctions, which provides for a high redox capacity of the heterojunction system (strong oxidative ability of Bi₄V₂O₁₁ and strong reductive capacity of g-C₃N₄) and facilitates the space separation of photo-generated charges. Moreover, the surface plasmon resonance effect of metallic Bi⁰ broadens the light utilization range of the heterojunction system. In addition, the possible degradation pathway and intermediates throughout the degradation process of OTC based on liquid chromatograph mass spectrometer (LC-MS) analysis were also studied. This work provides a novel tactic for the design and fabrication of g-C₃N₄-based S-scheme heterojunctions with enhanced photocatalytic performance.

Photocatalytic H₂O₂ production is a sustainable and inexpensive process that requires water and gaseous O₂ as raw materials and sunlight as the energy source. However, the slow kinetics of current photocatalysts limits its practical application. ZnO is commonly used as a photocatalytic material in the solar-to-chemical conversion, owing to its high electron mobility, nontoxicity, and relatively low cost. The adsorption capacity of H₂O₂ on the ZnO surface is low, which leads to the continuous production of H₂O₂. However, its photoresponse is limited to the ultraviolet (UV) region due to its wide bandgap (3.2 eV). Polydopamine (PDA) has emerged as an effective surface functionalization material in the field of photocatalysis due to its abundant functional groups. PDA can be strongly anchored onto the surface of a semiconducting photocatalyst through covalent and noncovalent bonds. The superior properties of PDA served as a motivation for this study. Herein, we prepare an inverse opal-structured porous PDA-modified ZnO (ZnO@PDA) photocatalyst by in situ self-polymerization of dopamine hydrochloride. The crystal structure, morphology, valency, stability, and energy band structure of photocatalysts are characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), electrochemical impedance spectroscopy (EIS), Mott-Schottky curve (MS), and electron paramagnetic resonance (EPR). The experimental results showed that electrons in PDA are transferred to ZnO upon contact, which results in an electric field at their interface in the direction from PDA to ZnO. The photoexcited electrons in the ZnO conduction bands flow into PDA, driven by the electric field and bent bands, and are recombined with the holes of the highest occupied molecular orbital of PDA, thereby exhibiting an S-scheme charge transfer. This unique S-scheme mechanism ensures effective electron/hole separation and preserves the strong redox ability of used photocarriers. In addition, the inverse opal structure of ZnO@PDA promotes light-harvesting due to the supposed "slow photon" effect, as well as Bragg diffraction and scattering. Moreover, the enhanced surface area provides a high adsorption capacity and increased active sites for photocatalytic reactions. Therefore, the resulting ZnO@PDA (0.03% (atomic fraction) PDA) exhibits the optimal H₂O₂ production performance (1011.4 μmol·L^-1·h^-1), which is 4.4 and 8.9 times higher than pristine ZnO and PDA, respectively. The enhanced performance is ascribed to the improved light absorption, efficient charge separation, and strong redox capability of photocarriers in the S-scheme heterojunction. Therefore, this study provides a novel strategy for the design of inorganic/organic S-scheme heterojunctions for efficient photocatalytic H₂O₂ production.

Graphitic carbon nitride (g-C₃N₄) has been widely used as a potential photocatalytic material for the removal of tetracycline from water. However, the poor visible light absorption ability and high recombination rate of the photogenerated charge significantly inhibit the catalytic activity of g-C₃N₄. Therefore, facile methods to improve the photocatalytic efficiency of g-C₃N₄ need to be developed. Hematite (α-Fe₂O₃), which has a good visible light absorption and corrosion resistance, is often used for photocatalysis and photo-Fenton reactions. Therefore, a two-dimension/two-dimension (2D/2D) S-scheme heterojunction constructed of g-C₃N₄ and α-Fe₂O₃ nanosheets could be expected to improve the degradation efficiency of tetracycline. In this study, 2D/2D S-scheme α-Fe₂O₃/g-C₃N₄ photo-Fenton catalysts were prepared using a hydrothermal strategy. The photo-Fenton catalytic activity of α-Fe₂O₃/g-C₃N₄ (α-Fe₂O₃ 50% (w)) was significantly improved by the addition of a small amount of H₂O₂, removing 78% of tetracycline within 20 min, which was approximately 3.5 and 5.8 times the removal achieved using α-Fe₂O₃ and g-C₃N₄, respectively. The high catalytic activity was attributed to the synergy between the photocatalysis and Fenton reaction promoted by the continuous Fe³⁺/Fe²⁺ conversion over the 2D/2D S-scheme heterojunction. The 2D/2D S-scheme heterojunction was crucial in the fabrication of the α-Fe₂O₃/g-C₃N₄ photocatalyst with a large surface area, adequate active sites, and strong oxidation-reduction capability. Furthermore, the photo-Fenton reaction provided additional hydroxyl radicals for the degradation of tetracycline with the aid of H₂O₂. The excess reaction product (Fe³⁺) was reduced to Fe²⁺ by the photogenerated electrons from the conduction band of α-Fe₂O₃. The resulting Fe²⁺ could participate in the photo-Fenton reaction. The morphological structures of α-Fe₂O₃/g-C₃N₄ were analyzed using transmission electron microscopy to demonstrate the formation of a 2D/2D structure with face-to-face contact, and the optical properties of the composites were measured using ultraviolet-visible diffuse reflectance spectroscopy. α-Fe₂O₃/g-C₃N₄ possessed a significantly improved visible light absorption compared to g-C₃N₄. Five sequential cyclic degradation tests and X-ray diffraction (XRD) patterns obtained before and after the reaction showed that the α-Fe₂O₃/g-C₃N₄ composites possessed stable photo-Fenton catalytic activity and crystal structures. Transient photocurrent responses of α-Fe₂O₃/g-C₃N₄ demonstrated that the prepared composites exhibited a higher charge transfer efficiency compared to that of single α-Fe₂O₃ and g-C₃N₄. In addition, according to the photoluminescence analysis and active species trapping experiments, a possible S-scheme heterojunction charge transfer process in the photo-Fenton catalytic reaction was proposed. This study provided a promising method for the construction of a high-performance photo-Fenton catalytic system to remove antibiotics from wastewater.

In previous decades, lithium-ion batteries (LIBs) were the most commonly used energy storage systems for powering portable electronic devices because LIBs exhibit reliable cyclability. However, owing to the low specific capacity of graphite used in the anode, further increase in the energy density of LIBs was limited. The Li metal anode is promising for the construction of next-generation high-energy-density batteries because of its ultrahigh theoretical capacity (3860 mAh·g^-1) and low redox potential (-3.04 V vs. standard hydrogen electrode). However, the high activity of Li causes dendritic growth during cycling, which leads to cracking of the solid-electrolyte interphase (SEI), increase in side reactions, and formation of dead Li. Several strategies have been proposed to address these issues, including use of electrolyte additives, high-concentration electrolytes, protection of the Li metal surface with various coatings, use of solid-state electrolytes, and design of a three-dimensional (3D) "Li host" for regulating the nucleation and deposition of Li metal. Among them, the design of a 3D "Li host" has proven to be a simple and effective strategy. However, the commonly used 3D "Li hosts" include nanostructured carbons, which are lithiophobic and, thus, provide limited interaction sites with Li⁺ ions, leading to the deposition of Li metal on the "Li host" surface. Therefore, it is necessary to design a 3D "Li host" with enhanced interaction with Li⁺ ions to achieve uniform deposition. Herein, we develop a soft-hard templating route to synthesize 3D macro-/mesoporous C-TiC (denoted as 3DMM C-TiC) nanocomposites, which has been used in Li metal batteries. The as-synthesized materials possess high surface areas (~510 m²·g^-1), ordered structures, large pore volumes, and excellent conductivity. The continuous plating and stripping of Li metal and the formation of the hierarchically porous structure with sufficient volume to allow uniform Li deposition result in the alleviation of the volume change. The high specific surface area significantly decreases the local current density and suppresses dendrite growth. Consequently, ultrasmall TiC nanoparticles are uniformly distributed in the 3D macro-/mesoporous framework, which improves conductivity, enhances their interaction with Li⁺ ions, and promotes the uniform deposition of Li metal. Therefore, the fabricated 3DMM C-TiC||Li battery displays stable cycling performance with improved Coulombic efficiency (98%) over 300 cycles. Moreover, when the 3DMM C-TiC based Li metal anode is assembled with a LiFePO₄ (LFP) cathode, the resultant full cells exhibit high specific capacity and excellent cycling stability. This study provides insight for the effective design of a 3D "Li host" for dendrite-free Li metal anodes.

Owing to their advantages such as safe operation, high power density, long cycle life, and low self-discharge rate, lithium-ion batteries (LIBs) have attracted attention for applications ranging from portable electronics to electric vehicles (EVs)/hybrid EVs (HEVs). However, the striking exothermic reaction and growth of lithium dendrites during lithiation-delithiation cycles for commercial graphite anodes are hidden safety risks associated with LIBs. Titanium dioxide (TiO₂) is considered as an important material for LIBs because of its high safety and excellent cycling stability. In addition, TiO₂ anode used in lithium-ion storage system has a relatively high voltage (~1.5 V vs. Li/Li⁺), and thus, it meets the strict safety standards of commercial LIBs. However, the unsatisfactory conductivity and ion diffusion rate prevent the further application of TiO₂ in LIBs. To date, the combination of graphene, carbon nanotubes (CNTs), carbon quantum dots (QDs) and porous carbon with TiO₂ has attracted significant research attention. Nevertheless, it is still challenging to introduce a unique nanostructure design by organically compounding TiO₂ with N-doped porous carbon matrix. Herein, N-doped porous carbon incorporating fine TiO₂ nanoparticles (NPs) with a flower-like structure (denoted as FL-TiO₂/NPC) is successfully prepared using flower-like NH₂-MIL-125(Ti) as the hard template. The as-prepared Ti-based framework shows a flower-like structure, which is assembled with two-dimensional (2D) corrugated porous nanosheets. On the one hand, the corrugated carbon nanosheets incorporating fine TiO₂ particles can offer a magnifying contact area between electrode matrix and electrolyte. On the other hand, the N-doped porous carbon plays a crucial role in improving the conductivity and structural integrity of the whole matrix. Therefore, the as-prepared FL-TiO₂/NPC can deliver an excellent reversible lithium storage capacity of 384.2 mAh·g^-1 at the current density of 0.5 A·g^-1 after 300 cycles and 279.1 mAh·g^-1 at 1 A·g^-1 after 500 cycles. Furthermore, even when tested at 2 A·g^-1, FL-TiO₂/NPC can deliver a reversible capacity of 256.5 mAh·g^-1 with a coulombic efficiency of 100% after 2000 cycles. The superior electrochemical performance and the structural toughness of LIBs originate from the unique flower-like structure. We believe that the proposed synthesis strategy will provide a new idea for the preparation of metal oxides/N-doped porous carbon composites with high lithium storage performance.

Bifunctional electrocatalysts in alkaline media play an important role in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), owing to the considerable influence of water splitting in the green energy sector. Herein, we present surface-modified NiCo₂O₄ nanowires (NWs) with rich defects as a highly efficient overall water splitting electrocatalyst in alkaline media, where the surface modification is accomplished using organic ligands. X-ray photoelectron spectroscopy reveals that the increase in the Co²⁺/Co³⁺ ratio is responsible for the excellent bifunctional electrocatalytic performance of the surface-modified NiCo₂O₄ NWs. As expected, benefiting from the organic ligand-dominated surface modification, the optimized NiCo₂O₄ NWs can display an overpotential of only 83 mV for the HER and 280 mV for the OER, with a current density of 10 mA·cm^-2 in 1.0 mol·L^-1 KOH solution. More importantly, the NiCo₂O₄ NWs surface-modified using organic ligands exhibit outstanding performance for overall water splitting, with a voltage of 2.1 V and current density of 100 mA·cm^-2, and also maintain their activity for at least 15 h. The present work highlights the importance of increasing the content of Co²⁺ in the spinel structure of NiCo₂O₄ NWs for enhancing their performance in overall water splitting.

In the past decade, lithium-sulfur batteries have attracted increasing attention owing to their high energy density and are considered to be one of the key options for the next generation of commercial high energy density batteries. However, for a practical battery system, both high energy density and good safety are important. The safety shortcomings of lithium-sulfur batteries have hindered their development and commercial application. Overcharging is a common battery safety problem. In the case of lithium-sulfur batteries, overcharging triggers the rapid growth of lithium dendrites, which can break through the separator and cause internal short-circuiting, leading to dangerous accidents such as thermal runaway and explosions. In practice, an electronic control device is typically installed in a battery to monitor its charging voltage and avoid overcharging avoid overcharging. However, this method increases the cost, weight, and size of the battery system, and reduces the energy density. For the self-protection of lithium-sulfur batteries in the case of overcharging, many polymerizable aromatic compounds are used as additives to improve the overcharge tolerance of lithium batteries. When the electrode surface is covered by a polymer film formed by employing electropolymerization, the cell dies permanently; thus the overcharge protection works only once. In contrast, electroactive polymers having reversible electrochemical doping/dedoping properties can be used to inhibit the overcharging of lithium-sulfur batteries is a more attractive approach. In this study, voltage-sensitive polytriphenylamine (PTPAn) was prepared by the chemical oxidation of triphenylamine as a raw material and successfully applied to lithium-sulfur battery separator. The conductivity test results showed that the PTPAn/polypropylene (PP) separator has an ionic conductivity of 1.56 mS·cm^-1. The cyclic voltammogram (CV) test results showed that the PTPAn/PP separator has a redox peak in the range of 3.5?.2 V. At a charge/discharge rate of 0.1C, the lithium-sulfur batteries with the PTPAn/PP separator and blank PP separator had a discharge specific capacity of 424.8 and 407.2 mAh·g^-1, respectively after 200 cycles, with Coulombic efficiencies of 99.38% and 98.59%, respectively. Further, the rate (0.1C, 0.2C, 0.5C, 1C) tests showed that the lithium-sulfur batteries with PTPAn/PP separator had higher discharge specific capacities at different rates than the lithium-sulfur batteries with the blank PP separator. Moreover, when the lithium-sulfur battery with the PTPAn/PP separator was overcharged at the 4th cycle, the charge specific capacity was 843.1 mAh·g^-1 and the discharge specific capacity was 839.8 mAh·g^-1. The charging specific capacity was 690.2 mAh·g^-1 and the discharging specific capacity was 669.2 mAh·g^-1 at the 10th cycle of overcharging. At the 16th cycle of overcharging, the battery had a charge specific capacity of 538.7 mAh·g^-1 and a discharge specific capacity of 512.9 mAh·g^-1. The overcharge test showed that lithium-sulfur batteries with the PTPAn/PP separator continued to work well after different overcharge rates. At an overcharging rate of 1C, the battery voltage remained stable at 3.9 V, with a charge specific capacity of 349.8 mAh·g^-1 and a discharge specific capacity of 328.7 mAh·g^-1.

HfO₂-based ferroelectric capacitors, particularly TiN/Hf_xZr_1-xO₂/TiN metal insulator metal (MIM) capacitors, have attracted considerable attention as promising candidates in the new generation of nonvolatile memory applications, because of their excellent stability, high performance, and complementary metal oxide semiconductor (CMOS) compatibility. At the electrode interface of TiN/Hf_xZr_1-xO₂/TiN MIM ferroelectric devices, the existence of the TiO_xN_y layer, which was formed during Hf_xZr_1-xO₂ film crystallization and TiN oxidization, can affect interface/grain boundary energy, film stress, and conduction band offset at the TiN/Hf_xZr_1-xO₂ interface, thereby affecting the ferroelectric device performance. Because the electrical performance of TiN/Hf_xZr_1-xO₂/TiN capacitors depends on both the ferroelectric Hf_xZr_1-xO₂ thin films and electrode TiN/insulator Hf_xZr_1-xO₂ interface, it is essential to control the fabrication of the TiN/Hf_xZr_1-xO₂/TiN heterostructure. Herein, we report a new method for preparing Hf_xZr_1-xO₂ ferroelectric thin films, sandwiched between TiN electrodes, by atomic layer deposition (ALD) and using ultra high vacuum (UHV) sputtering equipment interconnected with an ultra-high vacuum system. The quasi in situ characterization by transmission electron microscopy (TEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and other analytical methods conducted in our study indicates that the surface of the bottom TiN electrode does not contain oxygen. Moreover, a flat signal for impurities at the interface suggests that the superior ferroelectric performance of Hf_xZr_1-xO₂-based device is mainly attributed to the pristine Hf_xZr_1-xO₂/TiN interface. Furthermore, the ferroelectric properties of TiN/Hf_xZr_1-xO₂/TiN heterostructures on silicon can be modulated by varying ZrO₂ doping concentration and rapid thermal annealing (RTA) temperature, which can be well monitored and controlled by the interconnected system. We also investigate the ferroelectric properties of TiN/Hf_xZr_1-xO₂/TiN capacitors with different ZrO₂ doping concentrations (30%–60% (x)) at room temperature by changing the ALD pulsing ratio within the vacuum interconnected system. Three identical 10 nm-thick Hf_0.5Zr_0.5O₂ samples sandwiched between TiN electrodes are annealed in N₂ ambient at 400, 450 and 600 ℃ for 5 min to investigate the effect of RTA on device performance. The evolution of P-E hysteresis at different applied voltages and RTA temperatures reveals that the saturation of P-E hysteresis and remanent polarization increase with RTA temperature. This increase is especially evident at low applied voltages such as 1.5 V. A higher remanent polarization of 21.5 μC·cm^-2 than the previously reported value and a low coercive voltage of 1.35 V were achieved for the electric field of 3 MV·cm^-1 by doping 50% (molar fraction, x) ZrO₂ in HfO₂ through RTA at 600 ℃ for film crystallization.

Rechargeable aqueous Zinc-ion batteries (ZIBs) have emerged as potential energy storage devices due to their high energy density, low cost, and safety. To date, numerous cathodes based on manganese dioxide, vanadium dioxide, and polyanionic compounds have been reported. Among them, MnO₂ cathodes are particularly desirable candidates for commercialization owing to their tunnel structure and affordability. In particular, the parasitic reaction of Mn-based cathodes in alkaline batteries can be suppressed in mild aqueous electrolytes, resulting in enthusiasm for the development of rechargeable Zn||MnO₂ batteries. Even though various MnO₂ phases have been reported as hosts for Zn²⁺/H⁺ insertion, MnO₂ crystal structures undergo significant, irreversible transformations during cycling, which is a major challenge in Zn||MnO₂ batteries. In addition, the tunnel structure can collapse under the insertion of the hydrated cation resulting in Mn²⁺ dissolution into the electrolyte and significant loss in capacity over long cycling periods. The MnO₂ cathode also has low intrinsic electronic conductivity due to the large charge transfer resistance, which limits the diffusivity of divalent ions. Despite the achievements made in the field of ZIBs so far, designing active materials and ZIBs systems to meet commercial requirements is a significant challenge. In this study, we report the preparation of polypyrrole-wrapped MnO₂/carbon nanotubes (PPy@MnO₂/CNT) as composite cathodes for aqueous ZIBs. A combination of design strategies was used to increase structural stability and improve electronic conductivity, including increased electrode/electrolyte interaction by using nano-sized structures, shortened diffusion pathways through multistage composites, and enhanced electrical conductivity with conductive composites. The three-dimensional (3D) structured PPy/CNT network can facilitate mass and charge transport during the charge and discharge processes. The structure of MnO₂ wrapped by polypyrrole effectively prevents the dissolution of MnO₂. Thus, the assembled Zn||MnO₂ batteries, using PPy@MnO₂/CNT composite cathodes, exhibit a high capacity of 210 mAh·g^-1 at 1 A·g^-1, and achieve 85.7% capacity retention after 1000 charge/discharge cycles. Moreover, a high specific capacity of 100 mAh·g^-1 could be maintained at 2 A·g^-1, exhibiting excellent kinetic performance. The assembled quasi-solid Zn//MnO₂ battery, benefiting from the xanthan gum electrolyte and flexible CNT film, possesses intrinsic safety, bending resistance, and high potential in wearable applications.

The interfacial mass transfer characteristics of the gas-oil miscibility process are important in gas flooding technology to improve oil recovery. In this study, the process of gas flooding with actual components of Jilin oilfield is investigated by using molecular dynamics simulation method. We have chosen several alkane molecules based specifically on the actual components of crucial oil as the model oil phase for our study. The pressure of the gas phase is adjusted by changing the number of gas molecules while keeping the oil phase constant in the simulation. After the simulation, we analyze the variations of density in the gas-oil phase and interfacial characteristics to obtain the minimum miscibility pressure (MMP) for different displacement gases. The results show that the density of the gas phase increases while the density of the oil phase decreases with an increase in the displacement gas pressure, resulting in efficient mixing between the gas phase and the oil phase. At higher gas pressures, the thickness of the interface between the gas and oil phases is higher while the interfacial tension is lower. At the same time, we observed that the higher the CO₂ content in the displacement phase, the thicker the oil-gas interface becomes and the better the oil-gas mixing is under the same gas pressure. In this work, the gas-oil miscibility is studied with pure CO₂, pure N₂, and the mixture of these two gases, and it is found that the minimum miscibility pressure for pure CO₂ flooding (22.3 MPa) is much lower than that for pure N₂ flooding (119.0 MPa). When these two gases are mixed in 1 : 1 ratio, the MMP (50.7 MPa) is between the MMPs of the two pure gases. Moreover, the pressure required with CO₂ is lower than that required with N₂ to achieve the same displacement effect. Finally, we explain the mechanisms of the different miscibility processes for different gas pressure and different displacement gases from the perspective of the total energy of the system and the potential of the mean force between the gas and the oil. The total energy of the system increases with the pressure of the gas phase, implying that the number of collisions between the oil and gas molecules increases and the gas-oil miscibility is enhanced. In addition, by analyzing the potential of mean force profiles, it can be concluded that the force of attraction between the oil-phase molecules and CO₂ molecules is greater than that between the oil-phase molecules and N₂ molecules; thus, the CO₂ molecules easily mix with oil, and the effect of displacement is more obvious. These results are of great significance for understanding the interfacial mass transfer characteristics of the gas-oil miscibility process and for guiding the optimization and design of enhanced oil recovery technology by gas flooding.

Black phosphorus (BP) is a promising candidate for photovoltaic and optoelectronic applications owing to its excellent electronic and optical properties. It is believed that defects generally accelerate non-radiative electron-hole recombination in BP and hinder improvement of device performance. Experiments defy this expectation. Using state-of-the-art ab initio time-dependent density functional theory combined with non-adiabatic molecular dynamics, we investigate the non-radiative electron-hole recombination in monolayer (MBP) and MBP containing nanopore defects (MBP-ND). We demonstrate that non-radiative electron-hole recombination is promoted by the P-P stretching vibrations, and the recombination time of MBP-ND is approximately 5.5 times longer than that of the MBP system. This is mainly attributed to the following three factors: First, the nanopore creates no mid-gap state when increasing the bandgap by 0.22 eV owing to the downshift of the valence band maximum, caused by the decrease in the inter-layer P-P bond length, thereby weakening the antibonding interaction. Second, the nanopore reduces the overlap of electron and hole wave functions by diminishing the charge densities near the defect. Simultaneously, the nanopore significantly inhibits the thermal-driven atomic fluctuations. The increased bandgap correlated with the decreased wave function overlap and slowed thermal motions of the nuclei in the MBP-ND system reduces the non-adiabatic coupling by a factor of approximately 2 with respect to the pristine system. Third, the slow atomic motions weaken the electron-vibrational interaction and decrease the intensity of the major vibration mode at 440 cm⁻¹, which is the main source for creating non-adiabatic coupling, leading to loss of coherence formed between a pair of electronic states via non-adiabatic coupling and causing electron-hole recombination that results in a 1.5-fold increase in the coherence time in the MBP-ND system with respect to the MBP system. Consequently, the increased bandgap and decreased non-adiabatic coupling compete successfully with the prolonged coherence time, extending the excited-state lifetime to 2.74 ns in the system containing nanopore defects, which is only 480 ps in the pristine system. These phenomena arise owing to a complex interplay of the unusual chemical, structural, electrostatic, and quantum properties of BP with and without nanopore defects. This study is of great significance for understanding the excited-state properties of BP. The detailed mechanistic understanding of the prolonged charge carriers lifetime of MBP decorated with nanopore defects provides key insights for defect engineering in BP and other 2-dimensional materials for a broad range of solar and electro-optic applications by reducing the non-radiative charge and energy losses.

High-performance rechargeable lithium ion batteries have been widely applied in electrochemical energy storage fields, such as, energy storage grids, portable electronic devices, and electric vehicles (EVs). However, the energy density of lithium ion batteries needs to be increased, and the cost of battery materials could be further reduced for wider commercial applications. An Ni-rich cathode, LiNi_xMn_yCo_1-x-yO₂ (x > 0.8), with high specific capacity is the most promising material for next-generation Li-ion batteries. LiNi_xMn_yCo_1-x-yO₂ (x > 0.8) contains three transition metal elements, Ni, Mn, and Co, respectively. The role of Ni²⁺ is to provide high capacity for recharge The role of Mn⁴⁺ is to stabilize the lattice structure during charging-discharging cycling. Crucially, the role of Co³⁺ in Ni-rich materials is to improve the electrical conductivity and inhibit cation disorder in the lattice during electrochemical cycling. However, Co is both in shortage and expensive, which limits its worldwide commercial application. This work investigates substituting Co with other abundant and cheap transition metals. Transition metal ions Cr³⁺, Cd²⁺, and Zr⁴⁺ can replace Co³⁺ in Ni-rich cathode materials. LiNi_0.8Cr_0.1Mn_0.1O₂, LiNi_0.8Cd_0.1Mn_0.1O₂, and LiNi_0.8Zr_0.1Mn_0.1O₂ were synthesized by a co-precipitation method. Zr was found to be the best candidate for replacing Co in Ni-rich cathode materials. This study investigated Zr⁴⁺-doped Co-free Ni-rich materials. Initially, a carbonate co-precipitation process was used to synthesize Ni_0.8Zr_0.1Mn_0.1CO₃. This is due to that Zr³⁺/Zr⁴⁺ ions are not precipitated in the strong alkali solution, and the pH during hydroxide co-precipitation and carbonate co-precipitation processes are approximately 11 and 8, respectively. Therefore, the carbonate co-precipitation synthesis method was chosen. Ni_0.8Zr_0.1Mn_0.1CO₃ was synthesized by carbonate co-precipitation at pH = 7.6, 7.8, 8.0, and 8.2. After electrochemical analysis, pH = 7.8 was identified as the optimal value. The next stage of the research involved completing an electrochemical performance comparison on two lithium sources. The following lithium sources were added to the precursor; LiOH·₂O, and a 1:1 mixture of LiOH·₂O and Li₂CO₃. The lithium source with the 1:1 mixture, exhibited better performance for the Ni-rich cathode, LiNi_0.8Zr_0.1Mn_0.1O₂. In this study, the ideal doping amount of Zr in Ni-rich materials was 0.05. In conclusion, by careful control of co-precipitation pH and Li source, the Zr doped cobalt free Ni-rich cathode LiNi_0.85Mn_0.1Zr_0.05O₂ delivered a discharge capacity of 179.9 mAh·g^-1 at 0.2C. This was achieved between the voltage range of 2.75-4.3 V, with an 80 cycle capacity retention of 96.52%.

With the development of photovoltaic devices, organic-inorganic hybrid perovskite solar cells (PSCs) have been promising devices that have attracted significant attention in the fields of industrial and scientific research. Currently, the photoelectric conversion efficiency (PCE) of PSCs has been improved to 25.2%, and they are considered to be the primary alternative to silicon-based solar cells. However, the environmental stability of PSCs is unsatisfactory; they are prone to degradation under exposure to moisture, oxygen, elevated temperature, or even light illumination, which restricts their wide application in industrial production. Previous studies have elucidated that understanding the ultraviolet (UV)-induced degradation mechanism of organic-inorganic PSCs is of great importance for the improvement of light stability in PSCs. However, until now, there has been almost no comprehensive investigation on the decay process of PSCs under UV light illumination nor on the corresponding evolution of their microstructure. In this study, focused ion beam scanning electron microscopy (FIB-SEM) and aberration-corrected transmission electron microscopy (TEM) were used to comprehensively study changes in the performance and the evolution of the microstructure of PSC devices. The experimental results show that a built-in electric field developed under UV light illumination, which drove the diffusion of iodide ions (I^-) from the CH₃NH₃PbI₃ (MAPbI₃) layer to the hole transfer layer (HTL, Spiro-OMeTAD). Together with the photo-excited holes in the HTL, the I^- ions reacted with the Au electrode, and the Au atoms were oxidized into Au⁺ ions. Furthermore, Au⁺ ions preferred to diffuse across the HTL and the perovskite layer into the interface between the SnO₂ and MAPbI₃ layers. SnO₂ is known to be a good electron transfer layer (ETL), which should collect the photo-excited electrons to reduce the Au⁺ ions into metallic Au clusters; this is why the Au electrode was destroyed and Au clusters aggregated at the SnO₂-MAPbI₃ interface under the UV light illumination. Meanwhile, the Au clusters would accelerate the degradation of the perovskite. In addition, as the PSC performance declined (as determined by the PCE, open-circuit voltage (V_oc), and short-circuit current (J_sc)), the decomposition of tetragonal MAPbI₃ into hexagonal PbI₂ was observed at the interface between Spiro-OMeTAD and MAPbI₃, along with a widening of the grain boundaries in the perovskite layer. All of these factors play critical roles in the UV-induced degradation of PSCs. This is the first study to elucidate the light-induced migration of Au from the metal electrode to the interface between SnO₂/MAPbI₃, which reveals that the UV-induced degradation of PSCs may be mitigated by finding new ways to restrain the interdiffusion of Au⁺ and I^- ions.

A unique mixed-dimensional van der Waals heterostructure can be formed by integrating one-dimensional (1D) and two-dimensional (2D) materials. Such a 1D/2D mixed-dimensional heterostructure will not only inherit the unique properties of 2D/2D heterostructures, but also has a variety of stacking configurations, offering a new platform to adjust its structure and properties. The combination of p-type 1D single-walled carbon nanotubes (SWCNTs) and n-type 2D molybdenum disulfide (MoS₂) is one such example, possessing tunable properties. In situ chemical vapor deposition (CVD) is one of the most effective methods to construct 1D SWCNT/2D MoS₂ mixed-dimensional heterostructures. There are several reports of successfully grown SWCNT/MoS₂ heterostructures. The reports indicate that these heterostructures exhibit strong electrical and mechanical couplings between the SWCNTs and MoS₂, making it suitable for the construction of high-performance electronic and optoelectronic devices. However, there are still several problems associated with the in situ CVD growth of SWCNT/MoS₂ heterostructures. First, the growth mechanism of the 1D SWCNT/2D MoS₂ heterostructure is unclear. We still do not know how the existence of small-diameter SWCNTs will affect the nucleation and growth process of MoS₂. It is undetermined whether MoS₂ flakes will grow above the preexisting SWCNTs or under them. Second, current studies all report the growth of MoS₂ on a substrate sparsely covered by SWCNTs, which have a wide chirality distribution. Since the chirality of SWCNTs determines their physical properties and the density of SWCNTs significantly affects its performance in electronic devices, both the low density and wide chirality distribution of SWCNTs reported in these studies impose negative impacts on the interface behavior of SWCNT/MoS₂ heterostructures and their performance in devices. Herein, we report the preparation of high-quality 1D SWCNT/2D MoS₂ heterostructures by directly growing MoS₂ on dense and narrow-chirality distributed SWCNTs on a silicon substrate. To achieve this goal, high-purity semiconducting SWCNTs with narrow chirality distributions were sorted from the raw arc-discharged SWCNTs, and then high-density SWCNT arrays or networks were formed on a silicon substrate by dip-coating. Through in-depth analyses of the surface morphology and structure of the nuclei, we found that MoS₂ may prefer to grow under the SWCNTs and will grow much faster in the grooves between the SWCNTs to form a growth front. Therefore, an interesting "absorption-diffusion-absorption" growth mechanism has been proposed to explain the nucleation and growth process of SWCNT/MoS₂ heterostructures. In addition, we confirm the presence of strong charge coupling in the mixed-dimensional heterostructure through Raman analysis. Carriers can be quickly transferred through the interface between the SWCNTs and MoS₂, paving a way for the future design and fabrication of novel electronic and optoelectronic devices based on 1D/2D heterostructures.

The molecular magnetic tunnel junction (MMTJ) with high tunnel magnetoresistance (TMR) is an important component for devices such as computers and electronic storage. With the rapid development of the modern electronics industry, the decrease of device size and the increase of area density, it is important to improve TMR technology. In addition, the computing process faces huge challenges. As the size of electronic devices decreases, small changes may cause completely different transmission characteristics, therefore the minute details of the device must be carefully controlled. In this paper, in order to find large TMR values and explore the role of symmetry on spin-polarized transport properties, γ-graphyne nanodots (γ-GYND) coupled between ferromagnetic (FM) metallic zigzag graphene nanoribbon (ZGNR) electrodes were used. Depending on the widths of the ZGNR and two types of contact positions between the ZGNR and γ-graphyne nanodots (γ-GYND), eight ZGNR/γ-GYND/ZGNR MMTJs with different symmetries were constructed. By using Keldysh non-equilibrium Green's function (NEGF) and density functional theory (DFT), the I-V curve, the spin-injection efficiency (SIE) and TMR of MMTJs were calculated. We found that the transport properties of these MMTJs differed substantially. For absolute symmetric MMTJs, due to the wave functions corresponding to the band structure near the Fermi energy having different parity, the electron transport between the wave functions with different parity is prohibited, so we can see that the spin-down current is always zero. This implies that these absolutely symmetrical structures have 100% spin injection efficiency over a wide range of bias voltages. In addition, the calculation results also show that these absolutely symmetric structures also have large TMR at low bias, up to 3.7 × 10⁵, indicating that these devices have a large magnetoresistance effect and high magnetic field sensitivity, which can be used in the read head of computer hard disks, MRAM, and various magnetic sensors. However, for these asymmetric MMTJs, since there is no limitation of the wave function parity of the left and right electrodes, the spin-up current and spin-down current fluctuated as the bias voltage increased, so perfect SIE does not appear. In addition, the calculation results showed that the TMR of asymmetric MMTJs were four orders of magnitude smaller than with symmetric MMTJs. Thus the symmetry of MMTJs has a great influence on the spin-polarized transport properties of the device. These absolutely symmetrical MMTJs have spin-polarized transport properties that are far superior to other MMTJs. This is conducive to the manufacture of spin filters, rectifiers, and various magnetic sensors. Finally, these excellent characteristics can be explained by the transmission coefficient, local density of states (LDOS) and band structure.

Corrosion protection of reinforcing steel in concrete is an urgent task in modern society. Use of corrosion inhibitors in concrete is an effective, simple, and economical method for protecting reinforcing steel from corrosion. Mixed corrosion inhibitors usually perform better than a single inhibitor in actual reinforced concrete systems because of their synergistic inhibition effects. In recent years, environmentally friendly corrosion inhibitors have attracted increasing attention from corrosion researchers. Diisooctyl sebacate and sodium D-gluconate are environmentally friendly organic corrosion inhibitors, and ZnSO₄ is an inorganic cathodic inhibitor, they may form an innovative, nontoxic, and pollution-free mixed corrosion inhibitor to control reinforcing steel corrosion. Additionally, diisooctyl sebacate and sodium D-gluconate serve as absorption-type inhibitors, and ZnSO₄ acts as a precipitation-type inhibitor. We hypothesized that their combination might show a good synergistic corrosion inhibition effect on reinforcing steel. In this study, we developed a diisooctyl sebacate-based mixed corrosion inhibitor that includes D-gluconate and ZnSO₄ and investigated its synergistic inhibition effects on reinforcing steel (Q235 steel) corrosion in a simulated polluted concrete pore solution. The reinforcing steel corrosion behavior and the properties of the mixed corrosion inhibitor were studied by polarization curve measurements, electrochemical impedance spectroscopy tests, and surface analysis methods (scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy). The results indicated that the reinforcing steel in the simulated polluted concrete pore solution (pH 11.00, 0.5 mol·L^-1 NaCl) was in an active dissolving state and that localized corrosion took place. The mixed corrosion inhibitor, consisting of diisooctyl sebacate (59 mmol·L^-1), sodium D-gluconate (0.5 mmol·L^-1), and ZnSO₄ (1.5 mmol·L^-1), had an obvious and powerful inhibition effect. Its inhibition efficiency reached 96.8% and 90.0% in the simulated polluted concrete pore solution and the cement mortar, respectively. The mixture of diisooctyl sebacate with sodium D-gluconate and ZnSO₄ acted as a mixed-type inhibitor and effectively controlled both anodic and cathodic reactions of the steel corrosion.

The acid properties of SAPO-34 molecular sieves (MSs), including the strength and density of Brönsted acids, have attracted enormous attention in past decades because of the excellent performance of SAPO-34 in industrial processes such as the methanol-to-olefins (MTO) process and the selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). Currently, pure-phase SAPO-34 MSs with different Si contents can be easily obtained by utilizing multifarious organic structure-directing agents (OSDAs). However, the resulting SAPO-34 MSs have different acid properties, which may affect their catalytic performance. Hence, correlating the acid properties with the OSDAs and Si contents is of significance to synthesize SAPO-34 MSs with the desired properties. Herein, the acid properties of four series of SAPO-34 MSs with varying Si contents synthesized using tetraethylammonium hydroxide (TEAOH), diisopropylamine (DIPA), n-butylamine (nBA), and morpholine (MOR) as the OSDAs were probed in detail by thermogravimetry (TG), Rietveld refinement, and solid-state nuclear magnetic resonance (ss-NMR) analyses. The strength and acid density were systematically investigated by exploring the host-guest interactions between the probed molecule CD₃CN and the framework using ¹H magic angle spinning (MAS) NMR spectroscopy, and the local environments of Si were studied by ²⁹Si MAS NMR spectroscopy. The results of TG and Rietveld refinement showed that the SAPO-34 MSs templated by TEAOH and DIPA have only one OSDA per cha (one of the composite building units) cage in the longitudinal configuration, while those templated by nBA and MOR possess two OSDAs occluded in the cha cage in an up-and-down arrangement. Interestingly, the acid strength of SAPO-34 templated by TEAOH increased with increasing Si content, while the acid density remained almost unchanged. In contrast, the acid density of SAPO-34 templated by DIPA decreased evidently with an increase in the Si content, while the acid strength showed only a small variation. Among the other two samples, SAPO-34 templated by MOR has the most amounts of acid densities compared to SAPO-34 templated by nBA, while the strength is not superior. Thus, we conclude that the acid density is associated with the number of OSDAs in each cha cage and their protonation ability, while the difference in acid strength is attributed to the number of Si atoms at the edges of the Si islands. The findings of this study will provide insight into the acid properties of related crystalline porous materials.

G-rich DNA sequences can transform into G-quadruplexes (G4s) in the presence of metal ions. Based on the structural switches, G4 has been recognized as an attractive signal-transducing element for constructing colorimetric, electrochemical, and fluorescent sensing platforms capable of recognizing ions, small biological molecules, proteins, and even cells. For fluorescent sensing platforms, fluorescent small molecules (FSMs) specifically binding with G4s, such as crystal violet (CV), protoporphyrin IX (PPIX), zinc protoporphyrin IX (ZnPPIX), and Thioflavin T (ThT), are usually applied as fluorescent signal readout probes. It was noticed that the binding affinity of FSM with G4 is highly dependent on G4 morphologies because G-rich DNA sequences can fold into multiple G4 conformations, such as parallel, antiparallel, or hybrid. For example, CV only binds with antiparallel G4, PPIX or ZnPPIX preferentially interacts with parallel G4, and ThT displays high affinity for hybrid G4. Furthermore, the binding affinity of FSMs with G4 is also dependent on co-existing ions and ion concentrations, especially elevated Na⁺ level (140 mmol·L^-1). It is the reason why the performance of G4-based sensors in biological and environmental samples is decreased with different extents. Therefore, how to design G-rich DNA sequences to generally achieve FSMs specifically binding with G4, which is independent of G4 morphologies and co-existing Na⁺ and Na⁺ concentrations remains a challenge. In this study, a simple G-rich DNA sequence (thrombin binding aptamer, TBA) flanked by 10-mer single-stranded DNA at the 3' and 5' termini (TBA-10 bp) is designed. In the presence of K⁺, TBA transforms into antiparallel G4 (K⁺-TBA) and TBA-10 bp transforms into antiparallel K⁺-TBA flanked by fully hybridized double-stranded DNA (ds-DNA) (K⁺-TBA-10 bp). Actually, ThT cannot effectively bind with antiparallel K⁺-TBA. Compared with K⁺-TBA, upon K⁺-TBA-10 bp binding with ThT, ThT emission fluorescence increased by 100-fold. Importantly, the binding affinity improved by 1000-fold, which is independent of co-existing Na⁺ and Na⁺ concentrations (5-140 mmol·L^-1). Integrated with UV-Vis spectroscopy, fluorescent spectroscopy, and circular dichroism spectroscopy, it is believed that ThT can specifically and efficiently imbed in the junction between K⁺-TBA and ds-DNA. To corroborate the binding mode, TBA in TBA-10 bp is substituted by other G-rich DNA sequences transforming into parallel and antiparallel G4 in the presence of K⁺, respectively. The resulting improved ThT emission fluorescence indicated that such a specific binding mode generally improved the binding affinity of FSMs with G4. Our findings provide new insights into the improvement of the binding affinity of FSMs and G4, and reveal potential biochemical and bioanalytical applications of G4.

Graphene oxide (GO) possesses a large number of oxygen-containing functional groups on its basal planes and edges, enabling it to disperse well in water and other aqueous media. This property facilitates the processing of GO by various wet-processing methods. Because of its interesting properties and useful intermediate role in preparing graphene derivatives, GO has potential applications in many fields, including composites, separators, sensors, actuators, and energy storage and conversion. At high concentrations, strong, competitive interactions occur in GO aqueous dispersions that significantly impact the rheological behavior of these dispersions. In a liquid medium, the dispersed GO nanosheets form a unique colloidal system, in which solvation, electrostatic interactions, hydrogen bonding, and the lyophilic effect play important roles. The aromatic domains preserved from precursor graphite show attractive van der Waals interaction and π–π stacking between GO sheets. In this study, the effects of pH, temperature, and different organic solvents on the rheological behavior of GO dispersions were investigated through steady and dynamic rheological tests and theoretical analysis. The results showed that enhancing acidity, increasing the temperature within a certain range, and adding organic solvents such as pyridine promote transition of the GO aqueous dispersion from a viscoelastic liquid to a gel state, which shows different rheological properties. GO sheets in dispersion interact through negative charges originating from the many ionizable groups in the nanosheets and electrical double layers. Analysis using the Deryagin-Landau-Verwey-Overbeek (DLVO) theory showed that, under the conditions described above, these interactions were remarkably altered with consequent effects on the rheological properties. Weakened electric double-layer interaction disrupted the GO colloidal dispersion state and resulted in the association of GO nanosheets to form gel. Based on the above understanding, the yield stress of the GO dispersions affected by the volume fraction was analyzed by population balance equation (PBE) modeling. Through creep and relaxation experiments, the structure and rheological properties of GO dispersions at high concentrations were found to be similar in many respects to those of polymers. Therefore, the viscoelastic behavior of GO dispersions can be well described by the Poynting-Thomson model, which can provide theoretical support and advance the study of complex GO dispersions. These results shed new light on the rheological behavior of GO dispersions and can be used to optimize the processing conditions for future applications.

Photocatalytic hydrogen evolution is a scalable pathway to generate hydrogen fuels while mitigating environmental crisis. Strategies based on modification of the host photocatalyst surface are key to improve the adsorption/activation ability of the reaction molecules and the efficiency of charge transport, so that high-efficiency photocatalytic systems can be realized. Cadmium sulfide (CdS), a visible light-responsive semiconductor material, is widely used in photocatalysis because of its simple synthesis, low cost, abundant raw materials, and appropriate bandgap structure. Many researchers have focused on improving the photocatalytic efficiency of CdS because the rapid charge recombination in this material limits its applications. Among the various strategies proposed in this regard, surface modification is an effective and simple method used to improve the photocatalytic performance of materials. In this work, polyvinyl pyrrolidone (PVP)-capped CdS (denoted as P-CdS) nanopopcorns with hexagonal wurtzite (WZ)-cubic zinc blende (ZB) homojunctions were fabricated via one-step gamma-ray radiation-induced reduction under ambient conditions. Subsequent alkaline treatment under ambient conditions led to a dramatic improvement in the activity of the alkalized PVP-capped CdS (MP-CdS) photocatalyst. The structure and properties of the photocatalyst were determined by X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) analysis, Brunauer-Emmett-Teller (BET) specific surface area measurements, and photoelectric tests. The photocatalytic performance was evaluated based on the photocatalytic H₂ evolution under visible-light irradiation. The mechanism underlying the enhancement of the photocatalytic activity is also discussed. The results showed that after the alkaline treatment, the crystal structure of CdS with WZ-ZB homojunctions was preserved, but PVP on the surface of CdS hydrolyzed to form PVP hydrolysis product (MPVP) with carboxyl and amino groups. Owing to the increased alkaline solubility, a portion of MPVP dissolved into the solution and was removed from the surface of MP-CdS, exposing a greater number of active sites of the WZ-ZB phase junctions with a larger specific surface area. On the other hand, the carboxyl groups in MPVP coordinated with CdS could affect the bandgap and valence band position of CdS to facilitate the photocatalysis. Because of the synergistic effects of the exposure of WZ-ZB phase junctions and band structure engineering, the alkalized samples at a 1 mol·L^-1 concentration of NaOH showed a H₂ evolution rate of 477 μmol·g^-1·h^-1 under visible-light illumination, which was twice that obtained for the pristine P-CdS photocatalysts. This simple and low-cost post-synthesis strategy can be extended to the preparation of diverse functional photocatalysts. The present work is expected to contribute to the practical application of sulfide photocatalysts.

Electroreduction of CO₂ is one of the most promising CO₂ conversion pathways because of its moderate reaction conditions, controllable product composition, and environment-friendliness. However, most of the current CO₂ electroreduction technologies have not reached the techno-economic threshold for a competitively profitable electrochemical process. Based on a simple two-electron transfer process, the electroreduction of CO₂ to CO, which is further processed into syngas with the reduction of H₂O to H₂, is postulated to be the most promising pathway for a profitable electrochemical process. Such a process urgently requires nonprecious electrocatalysts that can precisely control the CO/H₂ ratio. Herein, we present a tailored synthesis of bifunctional electrocatalysts with high activity, which can realize the preparation of syngas with controlled compositions via molecular engineering of a ternary nanocomposite. Specifically, a mixture of melamine, triphenylphosphine, and nickel acetate was milled and dissolved in ethanol; the ternary nanocomposite was obtained after rotary evaporation of the mixture. We prepared the catalysts by pyrolyzing the obtained composites at 850 ℃ for 2 h. The synthesis strategy was facile and easy to scale. The specific surface area and pore volume of the bifunctional electrocatalyst were both significantly enhanced upon increasing the concentration of the phosphorus source, triphenylphosphine, during the precursor preparation. The obtained bifunctional electrocatalysts had hierarchically porous structures, which had well-dispersed active sites and could promote mass transport. Raman spectra revealed higher degrees of disorder with higher P/Ni ratios in the precursor. X-ray photoelectron spectroscopy verified the presence of Ni-P_x and Ni-N_x functionalities, which were the active sites for hydrogen evolution and CO₂ reduction, respectively. Hence, the electrocatalytic performance of this series of bifunctional electrocatalysts can be tuned from CO-dominant to H₂-dominant. The electrochemical performance was evaluated using a CO₂-saturated 0.5 mol·L^-1 KHCO₃ aqueous solution at ambient temperature by linear sweep voltammetry and potentiostatic electrolysis. Through these experiments, we determined that the activity of the catalysts was influenced by the surface phosphorus/Ni-N_x site ratio. The highest CO faradaic efficiency (91%) was achieved at -0.8 V (vs a reversible hydrogen electrode, RHE) with Ni-N-C in the absence of Ni-P. The CO/H₂ molar ratio in the syngas stream was tunable from 2 : 5 to 10 : 1 in the potential range from -0.7 to -1.1 V (vs RHE) with a total faradic efficiency of 100%. The syngas composition directly links to the molar ratio of the two integrated components, nickel phosphide and Ni-N-C. Additionally, the stability of the optimized bifunctional electrocatalyst at -0.7 V for 8 h was tested, in which the CO/H₂ ratio was maintained between 1.2 and 1.3, indicating excellent stability. This study provides a new perspective for the engineering of bifunctional electrocatalysts for the conversion of abundant CO₂ and water into syngas with tailorable CO/H₂ ratios.

Inorganic perovskite materials have gained considerable attention owing to their good thermal stability, high absorption coefficient, adjustable bandgap, and simple preparation. However, most inorganic perovskites are sensitive to water and need to be prepared under inert environments in a glove box, which increases their preparation cost. In this study, we used a simple one-step spin coating anti-solvent process to prepare CsPbI₂Br, which was then annealed in humid air (relative humidity < 35%) at 300 ℃ for 5 min with isopropanol as the anti-solvent. An inorganic perovskite solar cell with fluorine-doped tin dioxide/compact TiO₂/mesoporous TiO₂/CsPbI₂Br/hole transport materials/Ag structure was prepared. By varying the concentration of the mesoporous precursor, we controlled the thickness of mesoporous TiO₂ in order to investigate its effect on the properties of the perovskite films and devices. The X-ray diffraction (XRD) results confirmed the successful synthesis of CsPbI₂Br in humid air. Moreover, the thickness of the substrate affected the crystal growth orientation. The scanning electron microscopy results revealed that the thickness of the mesoporous titanium dioxide substrate affected the crystallization processing of CsPbI₂Br, resulting in the formation of compounds with different morphologies and phases. The ultraviolet-visible (UV-Vis) and photoluminescence spectra of the perovskite materials revealed that the substrate thickness affected their optical properties. With a decrease in the thickness of the mesoporous TiO₂ substrate, the bandgap of CsPbI₂Br increased slightly. At the substrate thickness of 145 nm, the defect density of state of CsPbI₂Br increased. At the optimum mesoporous titanium dioxide substrate thickness of 732 nm, the device showed the best power conversion efficiency of 8.16%. The electrochemical impedance spectroscopy measurements revealed that the devices prepared on thicker mesoporous layers showed better carrier extraction and transmission capabilities but higher interfacial charge recombination resistance, leading to a lower open-circuit voltage but higher current density. Thus, an increase in the thickness of the mesoporous substrate improved the photovoltaic performance of the devices. The stability of the CsPbI₂Br perovskite film improved with an increase in the mesoporous substrate thickness. The stability test results along with the UV-Vis and XRD analysis results showed that the perovskite film prepared on the 732 nm-thick substrate showed no significant structure change after being placed in humid air for 144 h. The stability of the perovskite solar cells was also investigated. The device with the 732 nm-thick substrate could maintain its original efficiency of 73% after exposure to air with relative humidity less than 35% for 72 h. Thus, inorganic perovskite solar cells could be successfully prepared in the humid air environment.

Pt-based catalysts are widely used in diesel oxidation catalyst (DOC) units, primarily to oxidize the harmful HC, CO, and NO emissions. Notably, NO₂ produced from NO oxidation is beneficial for low-temperature activity in NH₃-SCR and promotes soot oxidation in diesel particulate filters (DPF). Thus, the conversion of NO is an important parameter for determining the performance of DOCs. Considering the increasingly stringent emission regulations and the economic effectiveness, preparation of low-cost and highly active Pt-based catalysts is indispensable. Generally, the Pt⁰ content is crucial as it is an active component of DOCs. Small Pt size is beneficial for improving the catalytic activity. In this study, we applied a modified alcohol reduction-impregnation (MARI) method to synthesize highly active 1% (w, mass fraction) Pt/SiO₂-Al₂O₃ (denoted as MA-Pt/SA) catalyst. Meanwhile, using the conventional impregnation method, we prepared the Pt/SiO₂-Al₂O₃ catalyst with the same Pt loading (denoted as C-Pt/SA) as a reference sample. X-ray photoelectron spectroscopy (XPS) and hydrogen temperature program reduction (H₂-TPR) analyses proved that the MARI method could produce Pt catalysts with higher Pt⁰ content. Pt⁰ content in MA-Pt/SA was ~60.3% while that in C-Pt/SA was only ~23.1%. X-ray diffraction (XRD), CO-diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS), and transmission electron microscopy (TEM) characterization confirmed that the Pt particle size is much smaller over MA-Pt/SA as compared to that over C-Pt/SA. Performance evaluation of MA-Pt/SA and C-Pt/SA was conducted in a simulated diesel atmosphere. The results showed that the maximum NO conversion into NO₂ over MA-Pt/SA is 74% and 68% in the absence and presence of H₂O, respectively, which were much higher than those over C-Pt/SA (42% and 51% NO conversion with and without H₂O, respectively). Furthermore, the temperature for 30% NO conversion over MA-Pt/SA (218 ℃) markedly decreased as compared to that over C-Pt/SA (248 ℃), indicating the excellent low temperature activity. After the aging treatment with reaction gas at high temperatures, aged MA-Pt/SA maintained 69% NO conversion while aged C-Pt/SA showed only 41% NO conversion. In addition, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of NO + O₂ co-adsorption suggested that higher Pt dispersion and higher Pt⁰ content over MA-Pt/SA could facilitate the formation of bridging nitrates as intermediate species in NO oxidation at lower temperatures and could also facilitate their rapid decomposition (or desorption) at higher temperatures, thus imparting a high catalytic activity. Furthermore, a decrease in the Pt loading to 0.5% (w) resulted in a maximum NO conversion of 64% via the MARI method, suggesting a higher catalytic activity compared to that of C-Pt/SA with 1% (w) Pt loading. This work provides a method to prepare highly active Pt-based catalysts with low noble loading.

Supercapacitors that can withstand extremely low temperatures have become desirable in applications including portable electronic devices, hybrid electric vehicles, and renewable energy conversion systems. Graphene is considered as a promising electrode material for supercapacitors owing to its high specific surface area (up to 2675 m²·g^-1) and electrical conductivity (approximately 2 × 10² S·m^-1). However, the restacking of graphene sheets decreases the accessible surface area, reduces the ion diffusion rate and prolongs the ion transport pathways, thereby limiting the energy storage performance at low temperatures (typically < 100 F·g^-1 at sub-zero temperatures). Herein, we fabricate a supercapacitor based on holey graphene and mixed-solvent organic electrolyte for ultra-low-temperature applications (e.g., -60 ℃). Reduced holey graphene oxide (rHGO) was synthesized as the electrode material via an oxidative-etching process with H₂O₂. Methyl formate was mixed with propylene carbonate to improve the electrolyte conductivity at temperatures ranging from -60 to 25 ℃. The as-fabricated supercapacitor showed a high room-temperature capacitance of 150.5 F·g^-1 at 1 A·g^-1, which was almost 1.5 times greater than that of the supercapacitor using untreated reduced graphene oxide (rGO; 101.4 F·g^-1). The improved capacitance could be attributed to the increased accessible surface rendered by the abundant mesopores and macropores on the holey surface. As the temperature decreased to -60 ℃, the rHGO supercapacitor still delivered a high capacitance of 106.2 F·g^-1 with a retention of 70.6%, which was superior to other state-of-the-art graphene-based supercapacitors. Electrochemical impedance spectra tests revealed that the ion diffusion resistance in rHGO was significantly smaller than that in rGO and less influenced by temperature with a lower activation energy. This was because the holey morphology can provide transport pathways for ions and reduce the ion diffusion length during charging/discharging, consequently diminishing the diffusion resistance at low temperatures. Specifically, at -60 ℃, the energy density of supercapacitor reached up to 26.9 Wh·kg^-1 at 1 A·g^-1 with a maximum power density of 18.7 kW·kg^-1 at 20 A·g^-1, surpassing the low-temperature performance of conventional carbon-based supercapacitors. Moreover, after 10000 cycles at -60 ℃ with a current density of 5 A·g^-1, 89.1% of capacitance was retained, suggesting the stable and reliable power output of the current supercapacitor at extremely low temperatures.

Resistive switching devices have the advantage that the resistance can be repeatedly regulated between two or more resistance states. As a new resistive switching device, a memristor has abundant resistance states that can be continuously tuned. In recent years, memristors have been extensively studied for emerging nonvolatile memories and in the construction of neuromorphic systems owing to their simple two-terminal structure, high integration, and low operating voltage compared with those of traditional metal-oxide-semiconductor field-effect transistors. However, their application is limited owing to their relatively poor reliability. Recently, several studies have shown that two-dimensional materials such as graphene oxide can optimize the memristor performance. A new two-dimensional material, MXene, also exhibits special mechanical and electrical properties that show promise for use in memristors owing to its two-dimensional layered structure similar to that of graphene. MXene is a two-dimensional transition metal carbide/nitride of the form M_n+1X_n, where M is an early transition metal and X is carbon or nitrogen. Its other characteristics such as hydrophilic surfaces and ultrahigh metal conductivity (6000–8000 S·cm^-1) have been studied, and it has been applied to energy storage devices and electronic devices such as supercapacitors and secondary batteries. However, the application of MXene in resistive devices has been rarely investigated, especially for memristors. In this study, we prepared Ti₃C₂ powder by etching layered compounds of Ti₃AlC₂ with a mixture of HCl and HF. Next, Ti₃C₂ film was introduced into the memristor structure by spin-coating. The physical characteristics of Ti₃C₂ were investigated and analyzed by X-ray diffraction and scanning electron microscopy, and a memristor with Cu/Ti₃C₂/SiO₂/W structure was fabricated. In this structure, Ti₃C₂ and SiO₂ were introduced as resistive layers, and related electrical properties were investigated. Under dual DC voltage sweeping, the typical switching characteristic curves of the memristor were measured. Moreover, the repeatability and stability of high- and low-resistance states were investigated and analyzed, respectively. The experimental results show that the device can maintain stable high- and low-resistance states for > 10⁴ s during 100 dual-voltage sweeping cycles. In addition, the device can be regulated by a pulse voltage and realize typical paired-pulse facilitation that is similar to biological synapses. This work proved that the Cu/Ti₃C₂/SiO₂/W memristor has huge potential for application in the construction of emerging memory devices and artificial neuromorphic systems.

Although there has been great progress, the commercialization of proton exchange membrane fuel cells (PEMFCs) is still hindered by high cost due to the use of Pt catalysts. Furthermore, structural improvement of the catalyst layers is limited by inadequate studies of the ultrathin perfluorosulfonic acid ionomer (e.g., Nafion ionomer) film in the catalyst layers. During the preparation of the catalyst ink, the dispersion solvent affects the morphology of Nafion ionomers, which affects the microstructure and proton conduction behavior of the Nafion thin film wrapped on the surface of the catalyst particles after the catalyst layer is formed. To simulate the aggregation of ionomers in the catalyst layer, a self-assembly technology was used to obtain nanoscale Nafion thin films with precise and controllable thickness on a SiO₂ model substrate. The proton conductivity and microstructure of the Nafion thin films were obtained through electrochemical impedance spectroscopy and a series of micro-characterization methods. Furthermore, the relationship between proton conduction behavior within ultrathin Nafion films and colloidal morphology in Nafion solution was studied using different organic solvents. The goal was to explore and establish the microstructure model of nanoscale Nafion thin films through micro-characterization technologies, such as nuclear magnetic resonance and dynamic light scattering. It was found that at the nanoscale, Nafion thin films (~40 nm) result in low proton conductivity; an order of magnitude lower than that of bulk membranes (~10–100 μm). However, replacing iso-propanol with n-butanol (which has a lower dielectric constant) as the dispersion media of the Nafion ionomer improved the proton conductivity of the Nafion thin films. This is because Nafion in solvents with a lower dielectric constant possesses higher main chain solubility and mobility. Thus, Nafion molecules more easily aggregate into large rod-shaped micelles, which is beneficial to the construction of proton conduction channels after the self-assembly process. Furthermore, the electrostatic force between Nafion aggregates and the substrate in solvents with lower dielectric constant is smaller. This means more sulfonic groups are involved in the formation of proton conduction channels that in turn improve the proton conductivity of the Nafion thin film. In general, Nafion in solvents with lower dielectric constant leads to a structure that can facilitate proton conduction. This study provides guidance for optimizing the structure of ultrathin Nafion films and improving the proton conduction in the catalyst layers of PEMFCs.

Lithium-ion batteries are the most widely used energy storage device owing to their advantages such as high energy density, high cycle life, and low self-discharge rate. Because two-dimensional (2D) materials are commonly used as anode materials, the study of their lithiation behaviors is significant for improving the energy density and cycle life of batteries. Although some spectroscopic methods have been developed for studying the intercalation/deintercalation process of lithium in graphene, a new characterization technique that can directly investigate ion diffusion pathways at a microscale level would be beneficial to provide more detailed information on the mechanism of electrochemical reactions. It is an efficient solution to utilize the high spatial resolution of microscopic characterization to study the microscale electrochemical process. For this purpose, it becomes necessary to develop special specimens and setups that can undergo electrochemical experiments and are also compatible with microscopic characterization techniques. Herein, we developed a new planar micro-battery architecture on a SiO₂-coated silicon substrate that can be used to study the lithiation behaviors of various 2D materials using the micro-Raman mapping technique. In this planar micro-battery, the mechanically exfoliated few-layer graphene was used as the positive electrode, the thermal-evaporated lithium metal was employed as the negative electrode, and the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide with lithium bis(trifluoromethane)sulfonimide was used as the electrolyte. The micro-battery was tested using the galvanostatic discharge method on a probe station in an argon glove box. The selected lab-on-chip solution makes the lithiation of graphene observable under the micro-Raman spectroscope with a high spatial resolution. Raman mapping was successfully performed and graphene G-band signals were observed. Based on the facts that a small amount of lithium intercalation in graphene induces a blueshift of its G-band, and a large amount of lithium intercalation induces the splitting of the G-band into G^- and G⁺, we can correlate the degree of lithiation in graphene with its G-band signals and thus monitor the lithium intercalation process on graphene in the planar micro-battery. The time-dependent lithium distribution in graphene at different discharge stages could be obtained by comparing the G-band Raman mapping images to the corresponding optical micrographs. On the basis of these analyses, it was found that lithium ions diffuse between the layers in graphene and terminate at the graphene fault. These results help us understand the diffusion process of lithium in the graphene electrode during discharge. Moreover, the as-developed micro-battery is compatible with more characterization methodologies, such as optical microscopy, electrical transport, and electron microscopy, providing a broad application platform.

Catalytic hydrogenation of CO₂ to methanol has attracted considerable attention due to its potential in alleviating global warming and mitigating the dependence on fossil fuels. Cu-based catalysts are widely used in industry because of their high activity for methanol production. However, the reaction still suffers from low methanol selectivity because of the generation of CO as a by-product via the reverse water gas shift reaction (RWGS). The formation of another by-product H₂O leads to inevitable Cu sintering, which decreases the methanol production rate. It is well known that CO can alter competitive molecular adsorption on the surface and the redox behavior of the active sites; hence, CO doping in feed gas might not only inhibit the RWGS but also minimize surface poisoning by the adsorbed oxygen. On the other hand, CO₂ hydrogenation to methanol over Cu-based catalysts is a structure-sensitive reaction, and a change in the precursor can have a remarkable influence on the structure and morphology of the catalyst, and ultimately, the catalytic performance. In this work, Cu/ZnO/Al₂O₃ catalysts have been prepared via a hydrotalcite-like precursor (CHT-CZA) and a complex phase precursor (CNP-CZA) using co-precipitation and ammonia evaporation methods. Subsequently, the performance of the two types of catalysts with different CO contents (CO₂: CO:H₂:N₂ = x:(24.5 - x):72.5:3) is compared at 250 ℃ and 5 MPa in order to explore the role of CO. The evaluation results show that both catalysts follow a similar trend in the conversion of CO and CO₂ as well as the space-time-yield (STY) of MeOH and H₂O. The conversions of CO₂ and STY_H2O decrease gradually with an increase in the CO volume, but STY_MeOH is positively correlated with the CO volume. Furthermore, X-ray photoelectron spectroscopy (XPS) analysis reveals that the amount of reduced Cu species on the surface increases with increasing CO content. Judging from these results, the introduction of CO inhibits the RWGS and enhances the methanol yield for both catalysts by removing the surface oxygen as the reducing agent and thereby facilitating the exposure of the active reduced Cu species. On the other hand, transmission electron microscopy (TEM) observations indicate the doped CO may cause agglomeration of particles due to over-reduction, leading to gradual catalyst deactivation. Compared with the traditional CNP-CZA, the catalyst derived from hydrotalcite-like compounds exhibits better activity and long-term stability under all atmospheres, at different CO doping levels. This is because the hydrotalcite-like layer structure helps maintain the active metal state and confine the structure by limiting the agglomeration of Cu species.

Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM), common incurable diseases caused by protein misfolding, have shown extensive correlation with each other via cross-aggregation between their related pathogenic peptide, amyloid β protein (Aβ) and human islet amyloid polypeptide (hIAPP), respectively. However, little is known about how these two peptides affect the cross-amyloid aggregation process in vivo. To better simulate the intracorporal environment, where different forms of amyloid aggregates co-exist and very few aggregates probably attach to the vessel wall as seeds, herein, we study the seeded-aggregation of Aβ and hIAPP in the presence of homogeneous or heterogeneous seeds, both in solution and on the solid surface, with different monomer and seed concentrations. In this study, Thioflavin T (ThT) fluorescence assay, atomic force microscopy (AFM), and far-UV circular dichroism (CD) were performed to investigate the aggregation process in solution. Moreover, the binding of monomers with seeds on solid surface was detected by quartz crystal microbalance with dissipation (QCM-D). The 3-(4, 5-dime-thylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assays with human neuroblastoma cells (SH-SY5Y) were finally used to test the cytotoxicity caused by the aggregates. Series of analyses confirmed that a small amount of Aβ40 or hIAPP seeds (1/50 of the monomers in solution) significantly changed the aggregation pathway, forming heterogeneous aggregates with different morphologies and increased β-sheet structures. MTT result showed that the heterogeneous aggregates obtained with Aβ40 and hIAPP seeding reduced the cell viability to 70.5% and 74.4%, respectively, both causing higher cytotoxicity than homogeneous aggregates (82.9% and 76.5%, respectively). The results in solution and on the solid surface both prove that Aβ40 and hIAPP seeds can not only induce rapid aggregation of their homogeneous monomers but also promote the heterogeneous monomers to aggregate, but monomer-heterogeneous seed binding efficiency is lower than that between homogeneous species. The differences in seeding and cross-seeding ability of Aβ40 and hIAPP indicate the barriers depended on the sequence similarity and structural compatibility between different amyloid aggregates. In the case of heterogeneous aggregation, aggregation features largely depend on the seeds. Furthermore, hIAPP seeds exhibited higher cross-seeding efficiency than Aβ40 seeds on the solid surface, which is different from the result in solution where Aβ40 seeds indicating the influence of interfacial properties on aggregation process. This finding would give a deep understanding of the cross-seeding aggregation process and we hope that this work will stimulate more research to explore all possible fundamental and practical aspects of amyloid cross-seeding.

Carbon dots (CDs), as a kind of carbon-based fluorescent nanodots (FNDs), not only retain the advantageous characteristics of carbon-based materials (e.g., low toxicity and biocompatibility) but also exhibit tunable fluorescence emission, low photobleaching, and undergo facile surface functionalization. Therefore, the prospect of applying these materials for analysis and detection, cell imaging, drug delivery, light-emitting devices, photocatalysis, biosensing, and cancer treatment is promising. Although the synthesis of carbon dots from green and renewable feedstocks as biomass carbon sources is possible, the controllability of the involved chemical reactions is poor, resulting in poor atom economy, low quantum yields, and, especially, extremely low yields of carbon dots. In addition, these disadvantages could lead to an increase in equipment requirements and could pose a safety risk because of the need for hydrothermal and solvothermal synthesis. Certain methods even require large amounts of acid/alkali, strong oxidants, or organic solvents, thereby complicating the post-processing process and generating waste and emissions. This research aimed to implement a new idea, namely to "fabricate" rather than "synthesize" carbon-based FNDs from a certain kind of natural and small unsaturated molecule with surface activity relying on a self-assembling and self-crosslinking strategy in lieu of traditional approaches that involve uncontrollable reactions with unknown mechanisms including pyrolysis, dehydrolysis, polyconcensation, and carbonization. In this context, conjugated linoleic acid (CLA) has been studied extensively in our laboratory, and was found to have the self-assembly and self-crosslink characteristics required by the above innovative strategy. This motivated us to adopt CLA as a new carbon source in this study. First, CLA self-assembles into unsaturated fatty acid liposomes (ufasomes) in an aqueous solution of pH 8.6 at ambient temperature (15-25 ℃), and then, the initiator Ammonium persulfate is added to induce self-crosslinking of the ufasomes at 80 ℃ to obtain firm and uniform nanoparticles. On this basis, the possibility of using them as FNDs is investigated. Consequently, FNDs based on self-crosslinked ufasomes (SCU-FNDs) are prepared in high FND yield of 73.9% after dialysis, with a consistent particle size (17 nm), a degree of self-crosslink (DSC) of 75%, and emission of bluish green fluorescence excited at 320 nm. Furthermore the "fabrication" route provided a clear solution of FNDs that could be applied directly without separation and purification and with no wasteful emissions, which is therefore beneficial for large-scale preparation. The experimental results showed that the fluorescence intensities of the SCU-FNDs are positively correlated with both the surface carboxyl groups and DSC results. A reasonable explanation for the former relationship is the effect of the restricted geometry of the ufasomes on the accumulation of oxygen atoms at the surface of FNDs, whereas the latter could be explained by the confinement effect of the covalent crosslink on the motion of the hydrocarbon chain of the CLA molecules. The experimental results also showed that the SCU-FNDs have temperature-sensitive fluorescence properties, which is attributed to the motion of the residual hydrocarbon chain inside the SCU-FNDs even though they have been locally polymerized. The change in the fluorescence intensity of the FNDs as a function of the temperature was good in accordance with the linear relationship I/I₀ = -0.00922T + 1.229 (R² = 0.99) in the range of 25-85 ℃, which demonstrates the potential for preparing green and safe undoped FNDs for use as biocompatible and temperature-sensitive fluorescent probes.

Perovskite solar cells (PSCs) attract much attention for their high efficiency and low processing cost. Power conversion efficiencies (PCEs) higher than 25% have been reported in literature, demonstrating the excellent application prospect of PSCs. In general, the crystallinity and the film composition of perovskite thin films are significant factors in determining device performance. Much effort has been made to control the growth process of perovskite films through the use of additives, passivation layers, special atmosphere treatments, precursor regulation etc. Among these methods, precursor solvent engineering is a simple and direct way to control the perovskite quality, but the controllability of components through solvent engineering is still difficult and has not yet been reported. Herein, we report the controlled formation of PbI₂ and PbI₂ with dimethyl sulfoxide (DMSO) nano domains through precursor solvent engineering. In particular, tuning the solvent content of the dimethyl sulfoxide: 1, 4-butyrolactone: N, N-dimethylformamide (DMSO : GBL : DMF) in the perovskite precursor solution, controlled the content of PbI₂ and PbI₂(DMSO) domains. Due to the lower boiling point and weaker coordination of DMF relative to DMSO, part of methylammonium iodide (MAI) would escape from the wet films during the evaporation process. Therefore, the PbI₂(DMSO) can't completely convert to perovskite crystals and is retained in the final films as residual PbI₂(DMSO) domains. Both UV-vis absorption spectrum and XRD spectrum confirmed the existence of PbI₂ and PbI₂(DMSO) domains. Importantly, the content of PbI₂(DMSO) was controllable by simply changing the relative proportion of DMF. With an increase in the DMF content, the residual PbI₂(DMSO) domains gradually increase. In addition, the influence of PbI₂ and PbI₂(DMSO) domains on the device performance was systematically investigated. The formation of PbI₂(DMSO) domains caused a decrease in external quantum efficiency (EQE) of the device over 300–425 nm, and consequently decreased the device performance. That was because the PbI₂(DMSO) domain has strong absorption over 300–425 nm. Therefore, the PbI₂(DMSO) domains would absorb the photons over 300–425 nm prior to the perovskite, however the photons absorbed by the PbI₂(DMSO) domains are not converted into the photocurrent. Thus, the perovskite solar cell containing PbI₂(DMSO) showed an EQE loss over 300–425 nm in the EQE spectra. This work provides a simple method to control the components, especially the content of the PbI₂(DMSO) domains, in perovskite films through regulating the precursor solvent. Additionally, this work revealed a PbI₂(DMSO) domain related EQE loss phenomenon, highlighting the importance of controlling this component.

Zirconium alloys are often used to fabricate nuclear fuel cladding and other structural materials because of their low thermal neutron absorption cross section, satisfactory corrosion resistance, and decent mechanical properties. The oxidation rate and hydrogen-absorption fraction of zirconium alloys can be reduced by adding moderate amount of Nb to them, and the corrosion resistance of zirconium alloys can be improved as well. Although the corrosion resistance of zirconium alloys has been widely recognized, the in situ study of zirconium alloys in conditions that resemble real oxidative-corrosion environments has still been a challenging subject. The initial oxidation behavior of zirconium alloys might affect the subsequent generation of oxides in the form of the element valence and type of surface oxides changes, resulting in the long-term corrosion-behavior changes. In addition, the reaction mechanism of Nb in zirconium alloys is still controversial. To investigate the influence of the alloy composition and environmental conditions on the initial oxidation behavior of zirconium alloys, in situ initial oxidation experiments were performed on two different Zr alloys in a near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) chamber. The samples were cut to the size of 12 mm × 3 mm, and the primary oxide film was removed via pickling, argon etching and annealing. Oxygen or water vapors with the pressure in the range of 1.3 × 10^-8-1.3 × 10^-1 mbar (1 mbar = 100 Pa) were gradually introduced into the NAP-XPS chamber after sample-surface cleaning. The experiment was repeated at room temperature (300 K) and 623 K. The results showed that both Nb-containing and Nb-free zirconium-alloy surfaces transitioned from a metallic state to various oxidation states during the initial oxidation process. The oxidation rates of both the alloys were lower in water vapors than those in oxygen. In the presence of water vapors or oxygen, both the alloys oxidized more slowly at room temperature than at 623 K. Compared with 1%Nb zirconium alloys, the Nb-free zirconium alloys were more easily oxidized and had a denser oxide layer, in the oxygen atmosphere at 623 K. To some extent, the presence of Nb would reduce the adsorption capacity of oxygen atoms. The oxidation rate of 1%Nb zirconium alloy was quick at room temperature and also at low water vapor pressures at 623 K; Nb promoted the formation of OH^- at the surface. Under the high pressure vapor atmosphere at 623 K, the Nb-free zirconium alloys were more prone to be oxidized; Nb diffused to the surface at high temperatures and inhibited the breaking of the OH^- bond; however, the surfaces of both the samples could not be completely oxidized in a short time.

The environmental behaviours of actinides and fission products have been highly concerned due to their potential risks to human beings after entering the body through inhalation or food chains. The chemical reactions of actinides and fission products at mineral-water interface are the most important factors influencing the sorption, diffusion, migration and other processes of actinides and fission products in natural environments. Therefore, it is of great importance to investigate the chemical behaviours of these radioactive elements or nuclides in terms of environmental safety, especially in the area of safety assessment for geological disposal of high level radioactive wastes. However, the chemical behaviours of nuclides at mineral-water interface are complex and the investigations at a molecular level are challenging. To understand the chemical behaviours of trivalent actinides An(Ⅲ) in depth, non-radioactive Eu(Ⅲ) is used as an analogue of An(Ⅲ) due to their similar ionic sizes and chemical characteristics. In this study, batch sorption experiments and spectroscopic characterization methods were used to study the surface sorption species of Eu(Ⅲ) on montmorillonite and possible sorption mechanisms. We studied the effects of solid-liquid ratio, contacting time, ionic strength, pH, carbonate and phosphate on Eu(Ⅲ) sorption on montmorillonite. Our results indicated that the sorption percentage of Eu(Ⅲ) on montmorillonite was low in the range of pH 3.0 to 6.0, and much higher in the range of pH 7.0 to 10.0. The increase of ionic strength inhibited the sorption of Eu(Ⅲ) at low pH values, suggesting that the sorption of Eu(Ⅲ) on montmorillonite was mainly outer-sphere complexation in low pH conditions. Based on the results of fluorescence analysis, we can conclude that the sorption of Eu(Ⅲ) on montmorillonite is mainly outer-sphere complexation in low pH conditions, inner-sphere complexation in neutral pH conditions and surface induced precipitations in high pH conditions. Furthermore, we studied the sorption behaviours of Eu(Ⅲ) not only in montmorillonite/Eu(Ⅲ) binary system but also in montmorillonite/Eu(Ⅲ)/anion ternary system. Our results indicated that carbonate and phosphate could also influence the sorption of Eu(Ⅲ). Carbonate did not have an obvious influence on the sorption amount of Eu(Ⅲ), but it helped to change the surface sorption species of Eu(Ⅲ) on montmorillonite in high pH conditions. As for phosphate, although the sorption of phosphate onto montmorillonite was very weak, it could significantly enhance the sorption of Eu(Ⅲ) on montmorillonite. Because there were no reference data about fluorescence lifetime of Eu(Ⅲ)-phosphate species, we did XPS measurements and phosphate sorption experiments to find out the reason for phosphate enhancing effect. Our results proved that Eu(Ⅲ) precipitated as EuPO₄ on the surface of montmorillonite resulting in the enhancement of Eu(Ⅲ) sorption. This work is expected to provide a deeper understanding of the chemical behaviours of trivalent actinides An(Ⅲ) at mineral-water interface and predict the migration of An(Ⅲ) in the environment.

Since the First Industrial Revolution, traditional fossil energy (coal, petroleum, etc.) has been the most important energy source. However, with social progress and technological development, energy consumption continues to increase. But fossil energy not only has limited reserves, it also causes serious problems (environmental pollution, the greenhouse effect). Therefore, the research and development of clean and sustainable energy are particularly important. One research focus is hydrogen energy. Hydrogen is a promising energy carrier due to its high energy density, clean-burning characteristics, and sustainability. However, the challenges of hydrogen storage and transportation seriously limit its practical application in proton exchange membrane fuel cells. A potential solution is hydrogen storage in the form of a more stable precursor. One such precursor, formic acid, decomposes easily at room temperature in the presence of a catalyst without also producing toxic gases. Effective catalysts for formic acid decomposition (FAD) are key to hydrogen production by this method. In this study, a high-performance palladium (Pd)-based catalyst boosted by thin-layered carbon nitride was prepared for formic acid decomposition. First, trimeric thiocyanate was calcined by a one-step method to obtain carbon nitride (C₃N₄-S) directly, followed by fabrication of a Pd-based FAD catalyst with C₃N₄-S as support (Pd/C₃N₄-S). During the pyrolysis of thiocyanuric acid, the overflow of -SH in the precursor had a peeling effect, so that the C₃N₄ formed as a thin, broken layer with a large specific surface area and pore volume. Because of the improved specific surface area and pore volume and the resulting large number of defect attachment sites, the C₃N₄-S support effectively dispersed Pd nanoparticles. Furthermore, owing to the electron effect between the support and the metal, the Pd²⁺ content on the catalyst surface could be adjusted effectively. Pd/C₃N₄-S showed excellent FAD performance. This catalyst decomposed formic acid into CO₂ and H₂ effectively at 30 ℃. The turnover frequency and mass activity were as high as 2083 h^-1 and 19.52 mol·g^-1·h^-1, respectively. Testing of the gas product by gas chromatography showed that it did not contain CO, indicating that the Pd/C₃N₄-S catalyst had excellent selectivity. The catalyst also had good stability: its performance decreased by less than 10% after four testing cycles. This study provides a guiding example of development of a formic acid hydrogen production catalyst with high cost performance and a simple preparation method.

The gradual increase of CO₂ concentration in the atmosphere is believed to have a profound impact on the global climate and environment. To address this issue, strategies toward effective CO₂ conversion have been developed. As one of the most available strategies, the CO₂ electrochemical reduction approach is particularly attractive because the required energy can be supplied from renewable sources such as solar energy. Electrochemical reduction of CO₂ to chemical feedstocks offers a promising strategy for mitigating CO₂ emissions from anthropogenic activities; however, a critical challenge for this approach is to develop effective electrocatalysts with ultrahigh activity and selectivity. Herein, we report the facile synthesis of a highly efficient and stable atomically isolated nickel catalyst supported by ultrathin nitrogenated carbon nanosheets (Ni-N-C) for CO₂ reduction through pyrolysis of Ni-doped metal-organic frameworks (MOFs) and dicyandiamide (DCDA). MOFs are crystalline and assembled by metal-containing nodes and organic linkers, which have a large specific surface area, tunable pore size and porosity, and highly dispersed unsaturated metal centers. Thus, Ni-doped MOFs were chosen as the precursors to endow Ni-N-C with a porous carbon structure and nickel ions. The nitrogen in Ni-N-C came from DCDA, which acts as the active site to anchor nickel ions. Because of the porous structure and numerous nitrogen sites, the Ni content of Ni-N-C was as high as 7.77% (w). There were two types of nickel ion-containing structures, including Ni⁺-N-C and Ni²⁺-N-C. The structure transformation of the Ni⁺-N-C species from the initial Ni²⁺ (Ni-MOF) was achieved by pyrolysis, and the ratio of Ni⁺ and Ni²⁺ varied with the pyrolysis temperature. Compared to other Ni-N-C prepared at other temperatures, Ni-N-C-800 contained more Ni⁺-N-C species that possessed the optimum *CO binding energy and thus boosted the CO desorption and evolution rate, thereby exhibiting higher CO Faradaic efficiency (FE) up to 94.6% at -0.9 V (vs. the reversible hydrogen electrode, RHE) in 0.1 mol·L^-1 KHCO₃. In addition, it has been found that the rate of CO formation on the Ni-N-C-800 electrode relies on the electrolyte concentration. With the optimal electrolyte concentration, the Ni-N-C-800 electrode achieved a superior Faraday efficiency of > 90% for CO over a wide potential range of -0.77 to -1.07 V (vs. RHE) and displayed a CO FE as high as 97.9% with a current density of 12.6 mA·cm^-2 at -0.77 V (vs. RHE) in 0.5 mol·L^-1 KHCO₃. After testing at -0.77 V for 12 h, the Ni-N-C-800 electrode maintained a CO FE of approximately 95%, indicating superior long-term stability. We believe that this study will contribute to the design and synthesis of highly catalytically active atomically dispersed monovalent metal sites for metal-N-C catalysts.

Graphene-wrapped natural spherical graphite (G/SG) composites were prepared using the encapsulation–carbonization approach. The morphology and structure of the composites were characterized by scanning electron microscopy and X-ray diffraction analysis. The electrochemical performance of the composites with different graphene contents as anode materials for lithium-ion batteries was investigated by various electrochemical techniques. In the absence of acetylene black (AB), the G/SG composites were found to exhibit high specific capacity with high first-cycle coulombic efficiency, good cycling stability, and high rate performance. Compared with the natural spherical graphite (SG) electrode, the G/SG composite electrode with 1% graphene exhibited higher reversible capacity after 50 cycles; this capacity performance was equal to that of the SG + 10%AB electrode. Moreover, when the addition of 2.5% graphene, the composite electrode exhibited higher initial charge capacity and reversible capacity during 50 cycles than the SG+10%AB electrode. The significant improvement of the electrochemical performance of the G/SG composite electrodes could be attributed to graphene wrapping. The graphene shell enhances the structural integrity of the natural SG particles during the lithiation and delithiation processes, further improving the cycling stability of the composites. Moreover, the bridging of adjacent SG particles allows the formation of a highly conductive network for electron transfer among SG particles. Graphene in the composites serves as not only an active material but also a conductive agent and promotes the improvement of electrochemical performance. When 5%AB was added, the reversible capacity of the 5%G/SG electrodes significantly increased from 381.1 to 404.5 mAh·g^-1 after 50 cycles at a rate of 50 mA·g^-1 and from 82.5 to 101.9 mAh·g^-1 at 1 A·g^-1, suggesting that AB addition improves the performance of the G/SG composite electrodes. AB particles connect to G/SG particles through point contact type and fill the gaps between G/SG. A more effective conductive network is synergistically formed via graphene-AB connection. Although graphene wrapping and AB addition improve the performance of natural graphite electrodes, such as through increase in electrical conductivity and enhancement of Li-storage performance, including improvement of reversible capacity, rate performance, and cycling stability, electrode density typically decreases with graphene or AB addition, which should consider the balance between the gravimetric and volumetric capacities of graphite anode materials in practical applications. These results have great significance for expanding the commercial application scope of natural graphite. Our work provides new understanding and insight into the electrochemical behavior of natural SG electrodes in lithium-ion batteries and is helpful for the fabrication of high-performance anode materials.

The intercalation of potassium in graphite provides high energy density owing to the low potential of 0.24 V vs. K/K⁺, thereby making it a promising anode material for potassium ion batteries. However, the high volume expansion (60%) of graphite after potassium intercalation induces significant stress and electrode pulverization. Additionally, the sluggish kinetics of potassium insertion undermine the rate capability of electrodes. Using few-layer exfoliated graphite (EG) as a negative electrode material effectively relieves expansion-induced stress. Unfortunately, the close stacking of ultra-thin two-dimensional EG impedes ion transport. Furthermore, EG with smooth surfaces lacks active sites to adsorb K⁺, which is unfavorable for intercalation reactions. To address these problems, in this study, we designed an rGO/EG/rGO sandwich that coats EG with reduced graphene oxide (rGO). This complex material has two main advantages: (1) its 3D network can effectively prevent EG from stacking and buffer the volumetric variation of EG to improve the cyclic stability of the electrode, and (2) the loose structure and rich functional groups of rGO can also enhance the kinetic of potassium intercalation. Through hydrothermal reduction, GO was coated onto the EG surface and cross-linked to form a 3D network, by which EG stacking could be effectively mitigated. The rGO : EG ratio was precisely controlled by modulating the amount of reactant GO and EG. Transmission electron microscopy and scanning electron microscopy images showed that the rGO was uniformly coated on the EG surface to form a sandwich structure. X-ray diffraction patterns and Raman spectra demonstrated that rGO was physically adsorbed on the EG surface without notable chemical interactions. The EG structure was retained to ensure that its characteristic electrochemical properties were unaffected. Cyclic voltammetry and galvanostatic cycling tests were performed on the complex material with various rGO : EG ratios, exhibiting that rGO : EG = 1 : 1 (w/w) was optimal with a specific capacity of 443 mAh·g^-1 at 50 mA·g^-1. Even when operated at a high current density of 800 mA·g^-1, a specific capacity of 190 mAh·g^-1 was achieved, retaining 42.9% of the low-rate capacity, far exceeding those of pristine EG (14.2%) and rGO (27.2%). These results demonstrate that the rGO coating indeed enhanced the kinetics of potassium intercalation and efficiently improved the capacity and rate capability compared to pristine EG. We hope this work sheds light on novel approaches to improving potassium intercalation mechanisms in graphite.

Owing to the continuous increase in energy consumption and the growing depletion of traditional fossil fuels, the development of renewable energy is becoming increasingly urgent. Renewable energy has come to the fore, represented by geothermal energy and solar energy. However, the application of these energy sources is highly susceptible to weather, season, location, and time. Thus, these alternative energies are unstable, random, fluctuating, intermittent, and inefficient. The development of energy storage technologies can efficiently solve these problems, storing and releasing energy when needed. Among the key materials used in various energy-storage technologies, phase-change materials (PCMs) are strong candidates for smart thermal energy management and portable thermal energy sectors. As most innate PCMs face issues of low thermal conductivity, environmental pollution, and leakage over their melting point, encapsulating PCMs into supporting materials is necessary. However, these supporting materials face significant challenges in their application. First, skeleton materials should be resistant to the PCM volume changes during melting and solidification processes to achieve suitable structural stability. Second, skeleton materials should also have high thermal conductivity and a low leakage rate. Graphene aerogel (GA) has proven to be an effective supporting skeleton to improve the shape-stability of PCMs; however, the leakage caused by the phase transition and the brittleness of the network structure is a primary problem restricting its application. Skeleton materials play a crucial role in the performance of PCMs. Herein, we propose a double-pulse plating reinforcement strategy for fabricating copper@graphene aerogel (Cu@GA) as a skeleton material for phase change energy. In this design, individual nanosheets of the GA were uniformly covered and interlinked by copper particles. The Cu@GA interlinked networks ensure suitable thermal conductivity and a robust framework, beneficial for phase change heat transfer and leak-suppression performance. In addition, we prepared a PCM composite with high structural stability and low leakage rate by encapsulating octadecylamine (ODA) in Cu@GA through vacuum impregnation to ensure homogeneous ODA dispersion in the Cu@GA porous structure. The influence of different skeletons on the PCM composite leakage rate was investigated by comparing the weight change of the PCM composite. Benefiting from these structural features, the optimized composite phase change material (CPCM) Cu@GA/ODA showed a reduced leakage rate of 19.82% (w, mass fraction) compared to 80.31% (w) of GA/ODA and 72.99% (w) of GOA/ODA after 20 heat storage and release cycles. The cycled skeleton morphology was investigated using scanning electron microscopy to determine the origin of this influence. The skeleton integrity of Cu@GA/ODA was well maintained, while the three-dimensional network structures of GOA/ODA and GA/ODA showed shrinkage or collapse. Thus, the copper coating increased the skeleton's microstructural stability, conducive to high structural stability and reducing the leakage rate of the PCM composite. This study paves the way for the construction of ideal metal-coating GA composites with an excellent comprehensive performance for future phase change energy storage, porous microwave absorption, and energy storage applications.

With the development of human society and economy, the demand for energy resources has also increased rapidly. However, the use of traditional fossil energy leads to high amounts of carbon dioxide emissions, causing severe greenhouse effects. This, in turn, triggers a series of environmental problems. Harnessing renewable energy such as solar energy, wind energy, and hydropower to replace the traditional energy sources is very urgent. Conversion CO₂ into value-added fuels and chemicals could be a useful strategy to mitigate the current energy and environmental crisis. It is well known that Cu-based materials are good electrocatalysts for the electrochemical reduction of CO₂ (ECR-CO₂). However, they suffer from some disadvantages such as high overpotential and poor selectivity and durability. Therefore, the development of copper based electrocatalysts with high activity and selectivity is essential.

Metal-organic frameworks (MOFs) materials that have the advantages of large specific surface area, tunable pore size and porosity, and highly dispersed unsaturated metal centers can be used as electrocatalysts for CO₂ reduction or as precursors for further preparation of catalysts with excellent performance. Through thermal decomposition in an inert atmosphere, metal ions in MOF can be transformed into metal clusters, metal oxides, or even metal mono-atoms. Meanwhile, organic ligands are carbonized into porous carbon materials. The addition of some heteroatoms such as B, N, P, and S to carbon materials has also been shown to be effective in changing the electron state and coordination structure of the catalysts. These heteroatoms combine with carbon atoms to form a new active site, denoted as M-X-C (M is the central metal ion and X is the mixed heteroatom) to enhance the catalytic activity of the ECR-CO₂.

Herein, pre-synthesized Cu-NBDC MOF (a Cu-based MOF synthesized by using 2-aminoterephthalic acid (NBDC) as ligand) is used as a precursor to anchor Cu₂O/Cu on nitrogen doped porous carbon (Cu₂O/Cu@NC) by annealing at different temperatures. XPS analysis shows that the Cu-N content in Cu₂O/Cu@NC decreases with increasing annealing temperature. Investigation of the ECR-CO₂ reveals that Cu₂O/Cu@NC can inhibit the HER more effectively compared to Cu₂O/Cu@C, thereby improving the overall catalytic activity and multi-electron product selectivity of the ECR-CO₂. While the Faradic efficiency of formate (FE_formate) increases with increasing temperature, those of ethylene and methane (FE_C2H4 and FE_CH4, respectively) decreases with increasing temperature. Specifically, upon annealing at 400 ℃, the CO₂ Faradic efficiency of Cu₂O/Cu@NC-400 is higher than 86% (−1.4 to −1.6 V vs. RHE), including 20.4% of FE_C2H4 (−1.4 V vs. RHE) and 23.9% of FE_CH4 (−1.6 V vs. RHE). By contrast, FE_CH4 (−1.6 V vs. RHE) in the presence of Cu₂O/Cu@C-400 without nitrogen doping is only 2.33%, and no C₂H₄ is detected. These significant differences in the catalytic behavior can be attributed to the fact that Cu-N is conducive for the stable adsorption of the *CH₂ intermediate during the ECR-CO₂, thus inhibiting the evolution of H₂. These results indicate that the pathway of the ECR-CO₂ and its performance can be effectivel regulated by complexing nitrogen with Cu motifs.

Development of clean energy is an urgent requirement because of the depletion of fossil energy sources and increasingly severe environmental pollution. However, the lack of safe and efficient hydrogen storage materials is one of the bottlenecks in the implementation of hydrogen energy. Liquid organic hydrogen carriers (LOHCs) have been recognized as potential materials for the storage and transportation of hydrogen owing to their high gravimetric and volumetric hydrogen densities, reversible hydrogen absorption and desorption ability, and ease of widespread implementation with minimal modification on the existing fueling infrastructure. While some LOHCs such as cycloalkanes and N-heterocycles have been developed for hydrogen storage, they require a high hydrogen release temperature due to the large enthalpy change of dehydrogenation. In our previous work, a metallation strategy was proposed to improve the thermodynamic properties of liquid organic hydrogen carriers for hydrogen storage, and a series of metalorganic hydrides were synthesized and investigated. Among them, sodium phenoxide-cyclohexanolate pair, lithium carbazolide-perhydrocarbazolide, and sodium anilinide-cyclohexylamide pair showed promising dehydrogenation thermodynamics and improved hydrogen storage properties. Sodium pyrrolide and sodium imidazolide were also synthesized. However, pyrrolides were not well characterized, and the structure of lithium pyrrolide was not resolved. In the present study, we synthesized sodium and lithium pyrrolides by ball milling and wet chemical methods. One equivalent of hydrogen could be released from the reaction of pyrrole and metal hydrides, indicating the replacement of H by metal. The formation of pyrrolides was confirmed by nuclear magnetic resonance (NMR), X-ray diffraction (XRD) and ultraviolet-visible spectroscopy analyses. The ¹H signals attributed to C－H in the NMR spectra of the alkali metal pyrrolides shifted upfield due to the replacement of the H of N－H with a stronger electron-donating species (Li or Na), resulting in a greater shielding environment upon metallation. The absorption peaks of lithium and sodium pyrrolides showed red shifts, and the intensities became obviously stronger in the UV-Vis spectra, suggesting an enhancement of the conjugation effect, in accordance with theoretical calculations. The structure of lithium pyrrolide was determined by the combined direct space method and first-principles calculations on XRD data and Rietveld refinement. This molecule crystallizes in the monoclinic P2₁/c (14) space group, with lattice parameters of a = 4.4364(7) Å, b = 11.969(2) Å, c = 8.192(2) Å, β = 108.789(8)°, and V = 411.8(2) ų (1 Å = 0.1 nm). Each Li⁺ cation is surrounded by three pyrrolides via cation－N σ bonding with two pyrrolides and a cation–π interaction with the third pyrrolide, where the Li⁺ is on the top of the π face. Our experimental findings are different from the theoretical prediction in the literature.

With the rapid consumption of petrochemical resources and massive exploitation of shale gas, the use of natural gas instead of petroleum to produce chemical raw materials has attracted significant attention. While converting methane to chemicals, it has long seemed impossible to avoid its oxidation into O-containing species, followed by de-oxygenation. A breakthrough in the nonoxidative conversion of methane was reported by Guo et al. (Science 2014, 344, 616), who found that Fe©SiO₂ catalysts exhibited an outstanding performance in the conversion of methane to ethylene and aromatics. However, the reaction mechanism is still not clear owing to the complex experimental reaction conditions. One view of the reaction mechanism is that methane molecules are first activated on the Fe©SiC₂ active center to form methyl radicals, which then desorb into the gas phase to form the ethylene and aromatics. In this study, ReaxFF methods are applied to five model systems to study the gas-phase reaction mechanism under near-experimental conditions. For the pure gas-phase methyl radical system, the main simulation product is ethane after 10 ns simulation, which is produced by the combination of methyl radicals. Although a small amount of ethylene produced by C₂H₆ dehydrogenation can be detected, it is difficult to explain the high selectivity for ethylene in the experiment. When the methyl radicals are mixed with hydrogen and methane molecules, ethane remains the main product, together with some methane produced by the collision of hydrogen with methyl radicals, while ethylene is still difficult to produce. With the addition of hydrogen radicals to the methane atmosphere, methane activation can be enhanced by hydrogen radical collisions, which produce some methyl radicals and hydrogen molecules, but the methyl radicals eventually combine with the hydrogen species to produce methane molecules again. If some hydrogen molecules and methyl radicals are added to the CH₄/H∙ system, the activation of methane molecules by hydrogen radicals will be weakened. Hydrogen radicals are more likely to combine with themselves or with methyl radicals to form hydrogen and methane molecules, and the high selectivity for ethylene remains difficult to achieve. Thermal cracking of C₁₀H₁₂ at high temperature can produce hydrogen radicals and ethylene at the same time, which can partially explain the enhanced methane conversion and ethylene selectivity in the experiment of Hao et al. (ACS Catal. 2019, 9, 9045). Overall, the selective production of ethylene by nonoxidative conversion of methane over Fe©SiO₂ catalyst appears hard to achieve via a gas-phase mechanism. The catalyst surface may play a key role in the entire process of methane transformation.

The increasing development of society has resulted in the ever-growing demand for energy storage devices. To satisfy this demand, both energy density and safety performance of lithium batteries must be improved, which is challenging. Solid-state lithium batteries are promising in this regard because of their safe operation and high electrochemical performance. In recent years, intense effort has been devoted toward the exploration of materials with high ionic conductivity for room-temperature solid-state batteries. Among several types of solid-state electrolytes, Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP), an inorganic NASICON-type electrolyte, has drawn considerable attention because of its high ionic conductivity, wide electrochemical window, and environmental stability. However, the formation of lithium-ion-conducting networks within the electrode and between the electrode-LAGP interface is limited because of high interfacial resistance caused by the direct contact and volume expansion between the electrode and electrolyte. Thus, the application of LAGP in the fabrication of solid-state batteries is limited. Moreover, the occurrence of the unavoidable side reaction because of the direct contact of LAGP with the lithium metal anode shortens battery life. In addition, the rigid brittle nature of the LAGP electrolyte leads to the limits the facile fabrication of solid-state batteries. To overcome these limitations, herein, a novel strategy based on in situ polymerization of a vinylene carbonate solid polymer electrolyte (PVC-SPE) was proposed. The in situ formed PVC-SPE can effectively construct ion-conducting pathways within the cathode and on the interfaces of the LAGP electrolyte and electrodes. Furthermore, the PVC-SPE can significantly inhibit the side reaction between the lithium anode and LAGP electrolyte. The electrochemical performances of Li | LAGP | Li and Li | LAGP | Li with in situ PVC-SPE modified interface symmetrical solid-state batteries were compared. The in situ modified Li | LAGP | Li symmetrical solid-state battery exhibited stability toward plating and stripping for over 2700 h and a low overpotential (34 mV) at room temperature. Moreover, a Li | LAGP | LiFePO₄ solid-state battery exhibited a capacity retention of 94% at 0.2 C after 200 cycles with a capacity of 158 mAh·g^-1. In addition, high rate capability (72.4% capacity retention at 3 C) was achieved at room temperature. Therefore, the proposed in situ modification strategy was found to resolve the interface-related problem and facilitated the construction of the ion-conducting network within the electrode; thus, it can be a promising approach for the fabrication of high-performance solid batteries.

Cancer remains a major global cause of morbidity and mortality. Diagnosis at an early stage can significantly improve the survival of cancer patients. Cancers of different origins often have vastly different genotypes and phenotypes. Therefore, it is challenging to establish a universal strategy for cancer detection. Universal cancer detection can be potentially achieved by using pH-responsive probes. An acidic microenvironment is mainly caused by lactic acid accumulation in rapidly growing tumor cells. Based on the difference in pH between tumor and normal tissues, fluorescent materials that respond to a pH of around 6.8 are ideal for tumor detection. Carbon quantum dots (CQDs) have attracted much attention in bioimaging owing to their outstanding characteristics such as stable photoluminescence, low cytotoxicity, excellent biocompatibility, and resistance to photobleaching. In this study, red fluorescent CQDs (R-CQDs) were synthesized by the solvothermal treatment of 4-(dimethylamino) phenol in the presence of potassium periodate. The UV-Vis spectrum of the R-CQDs showed a characteristic absorption peak at 545 nm. The photoluminescence spectrum revealed an emission peak at 640 nm. The brightness of this photoluminescence peak was quantified to be 12.8% in terms of the absolute quantum yield (QY). Transmission electron microscopy (TEM) images showed that the R-CQDs have uniform sizes with an average diameter of 4 nm and a lattice spacing of 0.21 nm. Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed that the R-CQDs have a large number of carboxyl groups. The Raman spectrum of the R-CQDs showed the characteristic D band at 1340 cm^-1 and G band at 1585 cm^-1. The X-ray powder diffraction (XRD) pattern showed a broad (002) peak centered at around 23°. The R-CQDs were responsive to highly acidic or alkaline conditions. The incorporation of a block copolymer (MeO-PEG-PDPA), prepared by atom transfer radical polymerization (ATRP), on the R-CQDs produced pH-responsive fluorescent CQDs (pRF-R-CQDs). Photoluminescence (PL) spectra showed that the pRF-R-CQDs were responsive at pH 6.8. At pH > 6.8, the fluorescence of the pRF-R-CQDs would be quenched because of deprotonation of the amine groups. In contrast, protonation of the amine groups would lead to a dramatic increase in fluorescence emission. TEM images showed that the pRF-R-CQDs self-assemble and disassemble at pH 6.8 because of their pH-responsive properties. Compared with most existing fluorescent materials, the pRF-R-CQDs can effectively resist photobleaching and autofluorescence. Moreover, these pRF-R-CQDs have minimal toxicity and can distinguish tumors from normal tissues. Therefore, pRF-R-CQDs have great potential for use as a universal material in tumor microenvironment diagnosis.

Dye-sensitized solar cells (DSSCs) are the most promising alternatives to traditional fossil energy because of their advantages of low production cost, facile structure, relatively low environmental impact, relatively high photoelectronic absorption efficiency, and overall high efficiency. In addition, several studies on sensitizers as vital components have been conducted over the last three decades. Compared to metal dyes, metal-free organic dyes have been considered as promising candidates because of their simple fabrication, multiple structures, high molar absorption coefficients, easily tunable properties, and environmental friendliness. In this study, we systematically investigated the optoelectronic properties of six metal-free organic donor-acceptor dyes (RD1–6) derived from the known dye R6 by using the density functional theory (DFT) and time-dependent DFT methods. Cell performance parameters were discussed, including the geometrical and electronic structures, absorption spectrum, adsorption energy, light harvesting efficiency (LHE) curve, predictive short circuit current density (J_sc^Pred.), predictive open circuit voltage (V_oc^Pred.), and theoretical power conversion efficiency (PCE). Results revealed that all the designed dyes exhibited high theoretical PCE. In particular, dyes RD1, 2, and 4–6 showed greater conjugations, and dyes RD1–3 had smaller energy gaps than those of the reference dye. In addition, dyes RD1–3, 5, and 6 exhibited better light harvesting capacities that covered the entire visible region and extended to the near-infrared region with obviously red-shift maximum absorption wavelengths (λ_max), wider LHE curves, and higher J_sc^Pred. as compared to the reference dye. It was critical that dyes RD1 and 2 not only have greater conjugations and narrow band gaps but also good light harvesting capacities with more than 56-nm red-shift maximum absorption wavelengths and broadened LHE curves than those of the reference dye. Notably, mainly because of an average increment of 12.0% of J_sc^Pred., a remarkable increment of the theoretical power conversion efficiency was observed from 12.6% for dye R6 to 14.1% for dyes RD1 and 2. Thus, dyes RD1 and 2 exhibited superior cell performances and could be promising sensitizer candidates for highly efficient DSSCs. These results could be used to guide effective synthetic efforts in the discovery of efficient metal-free organic dye sensitizers in DSSCs.

In single-molecule junctions, anchoring groups that connect the central molecule to the electrodes have profound effects on the mechanical and electrical properties of devices. The mechanical strength of the anchoring groups affects the device stability, while their electronic coupling strength influences the junction conductance and the conduction polarity. To design and fabricate high-performance single-molecule devices with graphene electrodes, it is highly desirable to explore robust anchoring groups that bond the central molecule to the graphene electrodes. Condensation of ortho-phenylenediamine terminated molecules with ortho-quinone moieties at the edges of graphene generates graphene-conjugated pyrazine units that can be employed as anchoring groups for the construction of molecular junctions with graphene electrodes. In this study, we investigated the fabrication and electrical characterization of single-molecule field-effect transistors (FETs) with graphene as the electrodes, pyrazine as the anchoring groups, and a heavily doped silicon substrate as the back-gate electrode. Graphene nano-gaps were fabricated by a high-speed feedback-controlled electro-burning method, and their edges were fully oxidized; thus, there were many ortho-quinone moieties at the edges. After the deposition of phenazine molecules with ortho-phenylenediamine terminals at both ends, a large current increase was observed, indicating that molecular junctions were formed with covalent pyrazine anchoring groups. The yield of the single-molecule devices was as high as 26%, demonstrating the feasibility of pyrazine as an effective anchoring group for graphene electrodes. Our electrical measurements show that the ten fabricated devices exhibited a distinct gating effect when a back-gate voltage was applied. However, the gate dependence of the conductance varied considerably from device to device, and three types of different gate modulation behaviors, including p-type, ambipolar, and n-type conduction, were observed. Our observations can be understood using a modified single-level model that takes into account the linear dispersion of graphene near the Dirac point; the unique band structure of graphene and the coupling strength of pyrazine with the graphene electrode both crucially affect the conduction polarity of single-molecule FETs. When the coupling strength of pyrazine with the graphene electrode is weak, the highest occupied molecular orbital (HOMO) of the central molecule dominates charge transport. Depending on the gating efficiencies of the HOMO level and the graphene states, devices can exhibit p-type or ambipolar conduction. In contrast, when the coupling is strong, the redistribution of electrons around the central molecule and the graphene electrodes leads to a realignment of the molecular levels, resulting in the lowest unoccupied molecular orbital (LUMO)-dominated n-type conduction. The high yield and versatility of the pyrazine anchoring groups are beneficial for the construction of single-molecule devices with graphene electrodes.

Fullerene molecules have nano-scale cavities in which various metal or metal clusters of different sizes can be embedded to form metallofullerenes with unique core-shell structures. The physical and chemical properties of metallofullerenes can be modified through the interaction between the encapsulated metals and the fullerene cages. As such, the investigation of metallofullerenes with novel structures has been a principal research focus in the field of fullerenes. In this study, we investigated the size matching effect between encapsulated clusters and fullerene cages for the endohedral metal carbonitride clusterfullerenes in order to discover new metallofullerenes. The stability and electronic structure of the metallofullerenes formed by encapsulating M₃NC clusters (M = Y, La, Gd) into D₂(186)-C₉₆ and D₂(35)-C₈₈ fullerenes were studied using quantum chemical calculations. It was found that the fullerene cages formed stable structures by accepting six electrons transferred from the encapsulated clusters. The change in configuration of the encapsulated clusters was clarified by a comparison with the corresponding M₃N@C_2n metal nitride clusterfullerenes; the size matching effect between M₃NC cluster and fullerene cage was elucidated on the basis of the calculated results and previous studies on Sc₃NC@I_h(7)-C₈₀. For the D₂(186)-C₉₆ fullerene, the Gd₃NC cluster was found to have smaller changes in the configuration as compared with the La₃NC cluster, proving that Gd₃NC is more suitable than La₃NC for encapsulation in the D₂(186)-C₉₆ fullerene cage. In addition, it was determined that the La₃NC cluster requires a large structural change to maintain its planar configuration. For the D₂(35)-C₈₈ fullerene cage, the Y₃NC cluster is more suitable than Gd₃NC for encapsulation owing to the smaller size of the Y₃NC cluster. The spatial distribution of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of Gd₃NC@D₂(186)-C₉₆ were found to be similar to those of Gd₃N@D₂(186)-C₉₆. However, a unique endohedral cluster-based occupied molecular orbital was found for Gd₃NC@D₂(186)-C₉₆. This orbital is derived from the interaction between the NC unit and the Gd atoms. The spatial distribution of the HOMO of Y₃NC@D₂(35)-C₈₈ is similar to that of Y₃N@D₂(35)-C₈₈, while the LUMO of Y₃NC@D₂(35)-C₈₈ has a much larger contribution from the endohedral cluster as compared to Y₃N@D₂(35)-C₈₈. Thus, the addition of a carbon atom in the cluster has a remarkable impact on the electronic structure of the metallofullerenes. With respect to structural characteristics, we found that the three fullerene cages, D₂(186)-C₉₆, D₂(35)-C₈₈, and I_h(7)-C₈₀, have a uniform distribution of five-membered carbon atom rings; these fullerenes can be greatly stabilized in the form of C_2n^6- anions. However, the formation mechanism of fullerenes and metallofullerenes, at present, is poorly understood. Based on the structural analysis, we propose a direct mechanism for the formation of fullerenes without the Stone-Wales isomerization, i.e., the rearrangement of five-membered rings through the addition of carbon atoms and the transformation into larger carbon cages while maintaining stable structural units.

Bacterial infection is a major threat to human health, and can cause several diseases including gastroenteritis, influenza, tetanus, and tuberculosis. As conventional antibiotic treatment may cause various undesirable effects such as stomach disorder and bacterial resistance, it is necessary to improve the antibacterial efficiency of antibiotics. Here, we synthesized a peptide-based copolymer, poly(ε-caprolactone)-block-poly(glutamic acid)-block-poly(lysine-stat-phenylalanine)[PCL₃₄-b-PGA₃₀-b-P(Lys₁₆-stat-Phe₁₂)] by ring-opening polymerization (ROP) of ε-caprolactone and amino acid N-carboxyanhydride (NCA). Successful synthesis of the copolymer was verified by proton nuclear magnetic resonance and size exclusion chromatography. This copolymer can self-assemble into negatively charged micelles (-26.7 mV) under alkaline conditions by solvent switch method. The micelle structure was confirmed by transmission electron microscopy and dynamic light scattering, and revealed to have a diameter of ~42 nm. Antibiotics were loaded into micelles during the self-assembly process, and cell viability assay was conducted to evaluate its cytotoxicity with and without tobramycin. No obvious cytotoxicity was observed for both micelles when the concentration was lower than 300 μg·mL^-1. The antibiotic-loaded micelles demonstrated very low minimum inhibitory concentrations (MICs) against both Gram-negative Escherichia coli (E. coli) (7.8 μg·mL^-1) and Gram-positive Staphylococcus aureus (S. aureus) (18.2 μg·mL^-1), while the MICs of free tobramycin were 3.9 and 1.0 μg·mL^-1, respectively. The drug-loading content and efficiency of the micelles were 5.2% and 24.3%, respectively. Therefore, the MICs of the loaded tobramycin against E. coli and S. aureus were 0.4 and 0.9 μg·mL^-1, respectively, suggesting that the micelle could enhance the antibacterial activity of antibiotics. Tobramycin-loaded micelles demonstrated a sustained release characteristic, with 85% of the antibiotics released after 8 h. In bacteria-induced acidic microenvironment, the coil conformation of PGA blocks transforms and PGA blocks shrink toward the micelle core. Concomitantly, the carboxyl side chains are protonated in an acidic environment, increasing the hydrophobicity of this micelle. Antibiotics will be captured when reaching the outer core to slow down the releasing process. Furthermore, the poly(lysine-stat-phenylalanine) [P(Lys-stat-Phe)] coronas with broad spectrum intrinsic antibacterial activity can penetrate the bacterial cell membrane, leading to leakage of the cellular contents of the bacteria and ultimately their death. Due to the sustained release property of micelle and the intrinsic activity of the antibacterial peptide segments, this micelle can greatly enhance the antibacterial activity of antibiotics. Overall, this antibiotic-loaded micelle provides a novel approach for significantly reducing the antibiotics dosage and avoiding the associated health risks.

The preparation of high-efficiency and low-cost adsorbents for the defluoridation of drinking water remains a huge challenge. In this study, single-layer and multi-layer boehmite were first synthesized via an organic-free method, and active alumina used for fluoride removal from water was obtained from the boehmite. The advantage of a single layer is that more aluminum is exposed to the surface, which can provide more adsorption sites for fluoride. The active alumina adsorbent derived from single-layer boehmite exhibits a high specific surface area and excellent adsorption capacity. The high surface area ensures a high adsorption capacity, and the organic-free synthesis method lowers the preparation cost. The as-prepared adsorbent was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FTIR) and nitrogen adsorption-desorption analysis. The single-layer structure of boehmite was determined from the simulated XRD diffraction pattern of single-layer boehmite. The disappearance of the (020) diffraction peak of boehmite illustrates that the dimensions in the b direction are extremely small, and according to the XRD simulation results, the single-layer structure of boehmite could be determined. Single-layer boehmite with a surface area of 789.4 m²·g^-1 was formed first. The active alumina obtained from the boehmite had a surface area of 678.4 m²·g^-1, and the pore volume was 3.20 cm³·g^-1. The fluoride adsorption of the active alumina was systematically studied as a function of the adsorbent dosage, contact time, concentration, co-existing anions, and pH. The fluoride adsorption capacity of the active alumina obtained from the single-layer boehmite reached up to 67.6 mg·g^-1, which is higher than those of most alumina adsorbents reported in the literature. The adsorption capacities of the active alumina are related to the specific surface area and the number of hydroxyl groups on the surface. Dosages of 0.6, 1.0, and 2.6 g·L^-1 of active alumina were able to lower the 10, 20, and 50 mg·L^-1 fluoride solutions, respectively, below the maximum permissible limit of fluoride in drinking water in China (1.0 mg·L^-1), suggesting that the active alumina synthesized in this work is a promising adsorbent for defluoridation of drinking water. In addition, the fluoride adsorption is applicable in a wide pH range from 4 to 9 and is mainly interfered by SO₄^2- and PO₄^3-. Further investigation suggested that the fluoride adsorption of the active alumina follows the pseudo second-order model and Langmuir isotherm model

Synthetic matrices provide powerful tools for dissecting molecular interactions involved in the organization of the extracellular matrix (ECM), establishment of cell axis polarity, and suppression of neoplasticity in pre-cancerous endothelial cells. Collagen is the most abundant protein in extracellular matrix. A de novo approach is essential for the synthesis of collagen matrices which can have a broad impact on the understanding of matrix biology and our capacity to construct safe and medically useful biomaterials. Conventionally, the ECM has been studied by an analytical "top-down" approach, where the individual components of the matrix are first isolated and then characterized to explore their biochemical and functional properties. Since native collagen is difficult to modify and can engender pathogenic and immunological side effects, its application on tissue regeneration is limited. Therefore, we attempted to synthesize artificial collagen directly through small organic molecule recognition. The collagen-like peptides possess various benefits such as being clean, programmable, and easy to modify; therefore, in recent years, they have been used as ideal substrates for the synthesis of collagen nanomaterials. The self-assembly of collagen-like peptides is mainly driven by various non-covalent interactions such as electrostatic attraction, π-π stacking, and metal coordination. This renders a difficulty in the rational design of uniform nanostructures from short synthesized peptides and demands a novel strategy. To date, small organic molecules have been rarely used for the self-assembly of collagen-like peptides. In the present study, we attempted to use the small organic molecules for the combined supramolecular self-assembly of collagen-like peptides. Initially, the collagen-like peptides, (POG)₆ and (POG)₈, synthesized by the solid-phase synthesis technique, were both modified chemically using 4, 4'-methylene bis(phenyl isocyanate) to obtain the collagen-like hybrid peptides, AP₆ and AP₈, respectively. Phenyl isocyanate contributes to the formation of potential weak forces, such as hydrogen bonds and π-π stacking at the N-terminal regions of the collagen-like hybrid peptides. The purity and molecular weight of the collagen-like hybrid peptides were analyzed using analytical high-performance liquid chromatography (HPLC) and matrix-assisted laser desorption ionization time of flight (MALDI-TOF), respectively. The stability of AP₆ and AP₈ triple helices was analyzed by circular dichroism (CD) spectroscopy. The small organic molecule 4, 4'-methylene bis(phenyl isocyanate) promoted the unfolding of (POG)₆ and increased the melting temperature (T_m) of (POG)₈ from 37.7 to 58.8 ℃to form a triple helix. The hydrodynamic radii of collagen-like hybrid peptides were measured by dynamic light scattering (DLS). Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to analyze the morphology of the aggregation states. AFM results showed that the collagen-like hybrid peptides, AP₆ and AP₈, formed nanofibers spontaneously. Consistent with the AFM results, TEM showed that the AP₆ and AP₈ collagen-like hybrid peptides also formed nanofiber structures. The formation of stable complexes was attributed to the presence of multiple weak interactions such as hydrogen bonding, π-π stacking, and hydrophobic interactions. In the present study, we demonstrated that the chemical modification of collagen-like polypeptides at the N-terminus via the small organic molecule, 4, 4'-methylene bis(phenyl isocyanate), promoted the intramolecular and intermolecular assembly of collagen-like peptides. A simple and effective strategy has been developed in this study to promote the self-assembly of collagen-like peptides.

Ethanol has great application prospects given it is an important essential chemical and a substitute for traditional energy sources. Currently, ethanol production is achieved through grain fermentation and petroleum-based ethylene hydration. However, the inefficient fermentation processes and increasingly depleted crude oil resources hinder the large-scale production of ethanol. Therefore, the development of alternative technologies for ethanol production has become an important issue. The direct production of ethanol from syngas (CO + H₂) is considered to be a new strategy to acquire high value-added products and achieve clean utilization of carbonaceous resources such as coal, natural gas, and biomass. Supported Rh-based catalysts have been extensively studied as the most promising and effective systems for the direct production of ethanol from syngas. The use of promoters and supports is generally effective in increasing the activity and ethanol selectivity of supported Rh-based catalysts. Fe is widely used in the research on Rh-based catalysts, as it is one of the most effective promoters for enhancing ethanol selectivity. In this work, with the aim of exploring the role of the support, we used the incipient wetness impregnation method to prepare Fe-promoted Rh-based catalysts supported by CeO₂, ZrO₂, and TiO₂ for the synthesis of ethanol from syngas. CO conversion of CO on the RhFe/TiO₂ catalyst was as high as 18.2% under the reaction conditions of 250 ℃ and 2 MPa, and the selectivity to ethanol in the alcohol distribution was 74.7%, which was much higher than that observed with RhFe/CeO₂ and RhFe/ZrO₂ under the same conditions. The characterization results showed that the specific surface of the catalyst followed the order RhFe/CeO₂ < RhFe/ZrO₂ < RhFe/TiO₂; the dispersion of Rh increased sequentially, and the particle size decreased in the same order. A larger specific surface area may favor the dispersion of the Rh species, and the highly dispersed Rh species would imply a greater number of active sites on the surface of the support. The results of H₂-temperature-programmed reduction indicated possible interactions between Rh and the support as well as between Rh and Fe, and partial reduction of TiO₂ under the experimental reduction conditions; however, the other supports did not undergo reduction. The results of X-ray photoelectron spectroscopy indicated that the RhFe/TiO₂ catalyst had the largest amount of Rh⁰ as well as Rh⁺ species. Thus, this catalyst has more (Rh_x⁰-Rh_y⁺)-O-Fe^δ+ active sites for the synthesis of ethanol, which greatly increases the ethanol selectivity. CO-temperature programmed desorption was used to confirm the CO adsorption capacity of different catalysts. The results showed that TiO₂ enhances the adsorption of CO due to the presence of more O vacancies and Ti³⁺ ions, which is beneficial to the improvement of the catalyst activity.

Developing novel and efficient catalysts is a significant way to break the bottleneck of low separation and transfer efficiency of charge carriers in pristine photocatalysts. Here, two fresh photocatalysts, g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ hybrids, are first synthesized by anchoring Ni₃Se₄ and CoSe₂ nanoparticles on the surface of well-dispersed g-C₃N₄ nanosheets. The resulting materials show excellent performance for photocatalytic in situ hydrogen generation. Pristine g-C₃N₄ has poor photocatalytic hydrogen evolution activity (about 1.9 μmol·h^-1) because of the rapid recombination of electron-hole pairs. However, the hydrogen generation activity is well improved after growing Ni₃Se₄ and CoSe₂ on the surface of g-C₃N₄, owing to the unique effect of these selenides in accelerating the separation and migration of charge carriers. The hydrogen production activities of G-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ are about 16.4 μmol·h^-1 and 25.6 μmol·h^-1, which are 8-fold and 13-fold that of pristine g-C₃N₄, respectively. In detail, coupling Ni₃Se₄ and CoSe₂ with g-C₃N₄ greatly improves the light absorbance density and extends the light response region. The photoluminescence intensity of the photoexcited Eosin Y dye in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is weaker than that in the presence of pure g-C₃N₄. On the other hand, the upper limit of the electron-transfer rate constants in the presence of g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ is greater than that in the presence of pure g-C₃N₄. Among the g-C₃N₄@Ni₃Se₄@FTO, g-C₃N₄@CoSe₂@FTO, and g-C₃N₄@FTO electrodes, the g-C₃N₄@FTO electrode has the lowest photocurrent density and the highest electrochemical impedance, implying that the introduction of CoSe₂ and Ni₃Se₄ onto the surface of g-C₃N₄ enhances the separation and transfer efficiency of photogenerated charge carriers. In other words, the formation of two star metals selenide based on g-C₃N₄ can efficiently inhibit the recombination of photogenerated charge carriers and accelerate photocatalytic water splitting to generate H₂. Meanwhile, the right shift of the absorption band edge effectively reduces the transition threshold of the photoexcited electrons from the valence band to the conduction band. In addition, the more negative zeta potential for the g-C₃N₄@Ni₃Se₄ and g-C₃N₄@CoSe₂ catalysts as compared with that for pure g-C₃N₄ leads to a notable enhancement in the adsorption of protons by the sample surface. Moreover, the results of density functional theory calculations indicate that the hydrogen adsorption energy of the N sites in g-C₃N₄ is -0.22 eV; further, the hydrogen atoms are preferentially adsorbed at the bridge site of two selenium atoms to form a Se―H―Se bond, and the adsorption energy is 1.53 eV. In-depth characterization has been carried out by transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, transient photocurrent measurements, and Fourier transform infrared spectroscopy; the results of these experiments are in good agreement with one another.

The stability of nanocarriers in physiological environments is of importance for biomedical applications. Among the existing crosslinking approaches for enhancing the structural integrity and stability, photocrosslinking has been considered to be an ideal crosslinking chemistry, as it is non-toxic and cost-effective, and does not require an additional crosslinker or generate by-products. Meanwhile, most current temperature-responsive nanocarriers are designed and synthesized for drug release by increasing temperature. However, heating may induce cell damage during triggered drug release. Therefore, lowering temperature-triggered nanocarriers need to be developed for drug delivery and safe drug release during therapeutic hypothermia. In this study, we prepared an amphiphilic block copolymer, poly(ethylene oxide)-block-poly[N-isopropyl acrylamide-stat-7-(2-methacryloyloxyethoxy)-4-methylcoumarin]-block-poly(acrylic acid) [PEO₄₃-b-P(NIPAM₇₁-stat-CMA₈)-b-PAA₁₃], by reversible addition fragmentation chain transfer (RAFT) polymerization. Successful synthesis of the polymer was verified by proton nuclear magnetic resonance (¹H NMR) and size exclusion chromatography (SEC). The copolymers self-assembled into vesicles in aqueous solution, with the P(NIPAM-stat-CMA) block forming an inhomogeneous membrane and the PEO chains and PAA chains forming mixed coronas. The cavity of this vesicle could be utilized to load hydrophilic drugs. The CMA groups could undergo photocrosslinking and enhance the stability of vesicles in biological applications, and the PNIPAM moiety endowed the vesicle with temperature-responsive properties. Upon decreasing the temperature, the vesicles swelled and released the loaded drugs. The size distribution and morphology of the vesicles were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) experiments. After staining with phosphotungstic acid, the hollow morphology of the vesicles with a phase-separated inhomogeneous membrane was observed by TEM and SEM. The DLS results showed that the hydrodynamic diameter of the vesicles was 208 nm and the polydispersity was 0.075. The size of the vesicles observed by TEM was between 180 and 200 nm, which was in accordance with that measured by DLS. To verify the drug loading capacity and controlled release ability of the vesicle, a water-soluble antibiotic was encapsulated in the vesicles. The experimental results showed that the drug loading content was 10.4% relative to the vesicles and the drug loading efficiency was approximately 32.7%. For vesicles containing the same amount of antibiotics, the release rate at 25 ℃ was 35% higher than that at 37 ℃ after 12 h in aqueous solution. Overall, this photocrosslinked vesicle with temperature-responsive properties facilitates lowering temperature-triggered drug release during therapeutic hypothermia.

Vibrational spectroscopy is a powerful tool for studying the microstructure of liquids, and anatomizing the nature of the vibrational spectrum (VS) is promising for investigating changes in the properties of liquid structures under external conditions. In this study, molecular dynamics (MD) simulations have been performed to explore changes in the VS of 1-ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF₆]) ionic liquid (IL) under an external electric field (EEF) ranging from 0 to 10 V·nm^-1 at 350 K. First, the vibrational spectra for [Emim][PF₆] IL as well as its cation and anion are separately obtained, and the peaks are strictly assigned. The results demonstrate that the VS calculated by MD simulation can well reproduce the main characteristic peaks in the experimentally measured spectrum. Then, the vibrational spectra of the IL under various EEFs from 0 to 10 V·nm^-1 are investigated, and the intrinsic origin of the changes in the vibrational bands (VBs) at 50, 183, 3196, and 3396 cm^-1 is analyzed. Our simulation results indicate that the intensities of the VBs at 50 and 183 cm^-1 are enhanced. In addition, the VB at 50 cm^-1 is redshifted by about 16 cm^-1 as the EEF is varied from 0 to 2 V·nm^-1, and the redshift wavenumber increases to 33 cm^-1 as the EEF is increased to 3 V·nm^-1 and beyond. However, the intensities of the VBs at 3196 and 3396 cm^-1 show an obvious decrease. Meanwhile, the VB at 3396 cm^-1 is redshifted by about 16 cm^-1 when the EEF increases to 3 V·nm^-1, and the redshift increases to 33 cm^-1 with an increase in the EEF beyond 4 V·nm^-1. The intensity of the VB at 50 cm^-1 increases because of the increase in the total dipole moment of each anion and cation (from 4.34 to 5.46 D), and the redshift is attributed to the decrease in the average interaction energy per ion pair (from -378.7 to -298.0 kJ·mol^-1) with increasing EEF. The intensity of the VB at 183 cm^-1 increases on account of the more consistent orientations for cations in the system with increasing EEF. The VB at 3196 cm^-1 weakens visibly because a greater number of hydrogen atoms appear around the carbon atoms on the methyl/ethyl side chains and the vibrations of the corresponding carbon-hydrogen bonds are suppressed under the action of the EEF. Furthermore, the intensity of the VB at 3396 cm^-1 decreases due to the decrease in the intermolecular ⁺C-H···F^- hydrogen bonds (HBs), while the relaxation effect that is beneficial for the formation of HBs simultaneously exists in the system under the varying EEF, thus causing a redshift of the VB at 3396 cm^-1.

Graphene has become a research focus in recent years owing to its excellent characteristics, and glass is a commonly used material with high transparency and low cost. Graphene glass combines the excellent properties of both graphene and glass; graphene glass has not only high thermal conductivity, high electrical conductivity, and good surface hydrophobicity but also exhibits superior electrothermal conversion and wide-spectrum high-light-transmittance characteristics. Therefore, the study of graphene glass films is of theoretical value and practical significance. In this study, a high-purity glass-based (JGS1 quartz glass) multilayer graphene film was developed based on an atmospheric-pressure chemical vapor deposition (APCVD) method, and its electrical characteristics, light transmittance, and electrical heating characteristics were experimentally investigated in detail. The results show that graphene glass with different surface resistance values obtained through direct growth on a high-purity quartz glass substrate using the APCVD method, not only has excellent uniformity and quality, but also has considerably flat and high transmittance across the entire visible light region and exhibits excellent heating performance and fast response time. For graphene glass with a surface resistance of 1500 Ω·sq^-1, the light transmittance can reach 74%, and the saturation temperature can rise to 185 ℃ by applying a bias voltage of 40 V. In addition, when the resistance value of the graphene glass is 420 Ω·sq^-1, the graphene glass reaches a high saturation temperature of 325 ℃ in 40 s, and the corresponding heating rate can exceed 18 ℃·s^-1, achieving a significantly higher heating rate than other heating films at the same voltage. Compared with the polyethylene-terephthalate- (PET-) based and silicon-based graphene films obtained by the transfer, graphene glass has a higher saturation temperature, shorter thermal response time, and faster heating rate. Furthermore, graphene glass exhibits better heating cycle stability and longer-term heating stability at a constant voltage. In addition, an experiment using the graphene glass to thermally tune the wavelength of a vertical-cavity surface-emitting laser was conducted and gave good results. The position of the laser peak controlled by the graphene glass was red-shifted by 1.78 nm by applying a voltage of 20 V, and the wavelength tuning efficiency reached 0.059 nm·℃^-1. Compared with PET-based and silicon-based graphene films, the actual electrical heating capacity of graphene glass increased by 195%. These experimental findings demonstrate that graphene glass transparent films with excellent electric heating characteristics can be used in various transparent electric heating fields and have relatively wide application prospects.

Carbon materials have become one of the research hotspots in the field of catalysis as a typical representative of non-metallic catalytic materials. Herein, a facile synthetic strategy is developed to fabricate a series of hollow carbon nanoworms (h-NCNWs) that contain nitrogen up to 9.83 wt% by employing graphitic carbon nitride (g-C₃N₄) as the sacrificing template and solid nitrogen source. The h-NCNWs catalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (HR-TEM), N₂ adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric (TG), Raman spectra, and X-ray photoelectron spectroscopies (XPS). The catalytic activities of the h-NCNWs catalysts for selective oxidation of benzyl alcohol with O₂ were also evaluated. The characterization results revealed that the h-NCNWs catalysts displayed a unique hollow worm-like nanostructure with turbostratic carbon shells. The nitrogen content and shell thickness can be tuned by varying the relative ratio of resorcinol to g-C₃N₄ during the preparation process. Furthermore, nitrogen is incorporated to the carbon network in the form of graphite (predominantly) and pyridine, which is critical for the enhancement of the catalytic activity of carbon catalysts for the selective oxidation of benzyl alcohol. At a reaction temperature of 120 ℃, a 24.9% conversion of benzyl alcohol with > 99% selectivity to benzaldehyde can be achieved on the h-NCNWs catalyst prepared with a mass ratio of resorcinol to g-C₃N₄ of 0.5. However, the catalytic activities of the h-NCNWs catalysts were dependent on the amount of N dopants, in particular graphitic nitrogen species. The conversion of benzyl alcohol markedly decreased to 13.1% on the h-NCNWs catalyst prepared with a mass ratio of resorcinol to g-C₃N₄ of 1.5. Moreover, the h-NCNWs catalyst showed excellent stability during the reaction process. The conversion of benzyl alcohol and the high selectivity to aldehyde can be kept within five catalytic runs over the h-NCNWs0.5 catalyst. These results indicate that rationally designed carbon materials have great potential as highly efficient heterogeneous catalysts for oxidation reactions.

X-rays are widely used in many fields, including medical imaging, chemical structure analysis, and nondestructive examinations. However, long-term X-ray exposure is harmful to human health. Hence, radiation protection materials, especially wearable materials with outstanding performances, are in need of development. Lead (Pb) plates are commonly used as traditional radiation protection materials but have the disadvantages of heavy mass, toxicity, and poor wearability. Cement and alloy also are used to shield the X-ray, whereas application is limited by its heavy mass. In recent years, the wearable polymer based radiation protection was developed but has the defect which is low interfacial compatibility, resulting in poor shielding properties of the material. The K or L absorption edge of an element plays a major role in the attenuation of X-ray photon energy, and has a significant attenuation effect on X-ray photons with similar energy. As an alternative, it has been reported that the K absorption edge of rare earth (RE) elements is located in the range of 40–80 keV, which corresponds to the energy range of X-rays and medical X-ray energy range. Additionally, natural leather (NL) is an abundant natural biomass that is composed of multi-layered collagen fibers and contains amino (―NH₂), carboxyl (―COOH), and hydroxyl (―OH) groups. We believe that RE nanoparticles can be uniformly immobilized and stabilized by NL. In this study, we developed a novel strategy to prepare X-ray radiation protective materials by combining RE nanoparticles with NL. NL-based protective materials have the advantages of being lightweight and wearable while providing excellent protection. NL-based RE oxide nanoparticle composites (RE-NL) were successfully prepared by a "retanning" method and verified by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and transmission electron microscopy (TEM). X-ray protection tests showed that La-NL had the best shielding performance compared to the other tested RE oxide-loaded NLs owing to the small difference between the K-edge energy of La and the incident energy. Moreover, La_7.80-NL (La₂O₃ content of 7.80 mmol·cm^-3, 0.7 mm) showed better protection performance than a Pb plate with a high-Z elemental content (54.7 mmol·cm^-3, 0.25 mm) at 40–80 keV, confirming that the uniform distribution of RE oxides in NL provides enhanced X-ray shielding performance. The RE-NL also displayed a much better tensile strength, tear strength, and softness compared with polymer-based RE oxide composites. Meanwhile, it has the foldability and character of tailor. Therefore, the reported NL-based RE protective materials show promising potential for various scenarios requiring radiation protection.

Ionic liquids (ILs) are thermally and chemically stable and have adjustable structures, which gives them the potential to be used as green, efficient biomolecular solvents. Given the critical role of ILs in dissolving biomolecules, the mechanism of interaction between them deserves further study. Herein, density functional theory (DFT) calculations, using the SMD implicit water solvent model, were employed to study the interaction and mechanism between a hydrophobic zwitterionic amino acid (Tyr) and a series of imidazolium ILs with different alkyl chain lengths and methylation sites. The contributions of hydrogen bonding (H-bonding), electrostatic effects, induction, and dispersion to the intermolecular interactions were determined by combining the symmetry-adapted perturbation theory (SAPT), the atoms in molecules (AIM) theory, and reduced density gradient (RDG) analysis. The results indicate that the H-bonding between the IL cation and Tyr is stronger than that between the IL anion and Tyr; however, the binding between either ion and Tyr is dominated by electrostatic effects. By contrast, the difference between the induction and dispersion forces is small when methylation occurs on the C2 site of the imidazolium cation; whereas, it is significantly large when methylation takes place on the N3 site. This is rationalized by the interaction patterns that vary based on the methylation site. H-bonding and π⁺-π stacking interactions between the imidazole and benzene rings are dominant during C2-methylation, while H-bonding and C_Alkyl-H…π interactions between the alkyl chain and benzene ring are dominant during N3-methylation. Increasing the side alkyl chain length has different effects on the interaction energy to cations with different methylation sites. During N3-methylation, when the side alkyl chain length increases from 4 to 12, there are significant van der Waals interactions between the Tyr benzene and the side alkyl chain. However, these van der Waals interactions are inapparent when methylation takes place on the C2 site. Finally, the synergetic effect of the H-bonding and the interaction between the benzene and the side alkyl chain for C2-methylation is greater than the H-bonding and the interaction between the imidazole and benzene rings for N3-methylation, when the side alkyl chain length n > 9. Therefore, the interaction strength and mechanism in these imidazolium-Tyr complexes can be regulated by changing the methylation site and the side alkyl chain length of the cation. Further study of ion-pair and Tyr reveals that the change tendency of the interaction energy of IL-Tyr systems is consistent with that of cation-Tyr cases, and the ion pair further stabilizes the binding with Tyr. These results illustrate the interaction mechanism of IL-Tyr systems and provide a novel strategy for the design and screening of functional ILs for amino acid extraction and separation in the future.

Direct alcohol fuel cells (DAFCs) have attracted considerable research interest because of their potential application as alternative power sources for automotive systems and portable electronics. Pd-based catalysts represent one of the most popular catalysts for DAFCs due to their excellent electrocatalytic activities in alkaline electrolytes. Thus, it is of great importance to understand the structure-activity relationship of Pd electrocatalysts for alcohol electrocatalysis. Recently, size- and shape- controlled Pd nanocrystals have been successfully synthesized and subsequently used to study the size and shape effects of Pd electrocatalysts on alcohol electrocatalysis, in which the Pd (100) facet exhibited higher electrocatalytic oxidation activity for small alcohol molecules than the Pd (111) and (110) facets. Although it is well known that capping ligands, which are widely used in wet chemistry for the size- and shape-controlled synthesis of metal nanocrystals, likely chemisorb onto the surfaces of the resulting metal nanocrystals and influence their surface structure and surface-mediated properties, such as catalysis, this issue was not considered in previous studies of Pd nanocrystal electrocatalysts for electrocatalytic oxidation of small alcohol molecules. In this study, we prepared polyvinylpyrrolidone (PVP)-capped Pd nanocrystals with different morphologies and sizes and comparatively studied their electrocatalytic activities for methanol and ethanol oxidation in alkaline solutions. The chemisorbed PVP molecules transferred charge to the Pd nanocrystals, and the finer Pd nanocrystals had a higher coverage of chemisorbed PVP, and thus exposed fewer accessible surface sites, experienced more extensive PVP-to-Pd charge transfer, and were more negatively charged. The intrinsic electrocatalytic activity, represented by the electrochemical surface area (ECSA)-normalized electrocatalytic activity, of Pd nanocubes with exposed (100) facets increases with the particle size, indicating that the more negatively-charged Pd surface is less electrocatalytically active. The Pd nanocubes with average sizes between 12 and 19 nm are intrinsically more electrocatalytically active than commercial Pd black electrocatalysts, while the activity of Pd nanocubes with an averages size of 8 nm is less. This suggests that the enhancement effect of the exposed (100) facets surpasses the deteriorative effect of the negatively charged Pd surface for the Pd nanocubes with average sizes between 12 and 19 nm, whereas the deteriorative effect of the negatively charged Pd surface surpasses the enhancement effect of the exposed (100) facets for the Pd nanocubes with average sizes of 8 nm due to the extensive PVP-to-Pd charge transfer. Moreover, the Pd nanocubes with average sizes of 8 nm exhibit similar intrinsic electrocatalytic activity to the Pd nanooctahedra with (111) facets exposed and average sizes of 7 nm, indicating that the electronic structure of Pd electrocatalysts plays a more important role in influencing the electrocatalytic activity than the exposed facet. Since the chemisorbed PVP molecules block the surface sites on Pd nanocrystals that are accessible to the reactants, all Pd nanocrystals exhibit lower mass-normalized electrocatalytic activity than the Pd black electrocatalysts, and the mass-normalized electrocatalytic activity increases with the ECSA. These results clearly demonstrate that the size- and shape-dependent electrocatalytic activity of Pd nanocrystals capped with PVP for methanol and ethanol oxidation should be attributed to both the exposed facets of the Pd nanocrystals and the size-dependent electronic structures of the Pd nanocrystals resulting from the size-dependent PVP coverage and PVP-to-Pd charge transfer. Therefore, capping ligands on capped metal nanocrystals inevitably influence their surface structures and surface-mediated properties, which must be considered for a comprehensive understanding of the structure-activity relationship of capped metal nanocrystals.

Recently, the application of ReaxFF based reactive molecular dynamics simulation (ReaxFF MD) in complex processes of pyrolysis, oxidation and catalysis has attracted considerable attention. The analysis of the simulation results of these processes is challenging owing to the complex chemical reactions involved, coupled with their dynamic physical properties. VARxMD is a leading tool for the chemical reaction analysis and visualization of ReaxFF MD simulations, which allows the automated analysis of reaction sites to get overall reaction lists, evolution trends of reactants and products, and reaction networks of specified reactants and products. The visualization of the reaction details and dynamic evolution profiles are readily available for each reactant and product. Additionally, the detailed reaction sites of bond breaking and formation are available in 2D chemical structure diagrams and 3D structure views; for specified reactions, they are categorized on the basis of the chemical structures of the bonding sites or function groups in the reacting species. However, the current VARxMD code mainly focuses on global chemical reaction information in the simulation system of the ReaxFF MD, and is incapable of locally tracking the chemical reaction and physical properties in a 3D picked zone. This work extends the VARxMD from global analysis to a focused 3D zone picked interactively from the 3D visualization modules of VARxMD, as well as physical property analysis to complement reaction analysis. The analysis of reactions and physical properties can be implemented in three steps: picking and drawing a 3D zone, identifying molecules in the picked zone, and analyzing the reactions and physical properties of the picked molecules. A 3D zone can be picked by specifying the geometric parameters or drawing on a screen using a mouse. The picking of a cuboid or sphere was implemented using the VTK 3D view libraries by specifying geometric parameters. The interactive 3D zone picking was implemented using a combination of observer and command patterns in the VTK visualization paradigm. The chemical reaction tracking and dynamic radial distribution function (RDF) of the 3D picked zone was efficiently implemented by inheriting data obtained from the global analysis of VARxMD. The reaction tracking between coal particles in coal pyrolysis simulation and dynamic structure characterization of carbon rich cluster formation in the thermal decomposition of an energetic material are presented as application examples. The obtained detailed reactions between the coal particles and comparison of the reaction between the locally and globally picked areas in the cuboid are helpful in understanding the role of micro pores in coal particles. The carbon to carbon RDF analysis and comparison of the spherical region picked for the layered molecular clusters in the pyrolysis system of the TNT crystal model with the standard RDF of the 5-layer graphene demonstrate the extended VARxMD as a chemical structure characteristic tool for detecting the dynamic formation profile of carbon rich clusters in the pyrolysis of TNT. The extended capability of VARxMD for a 3D picked zone of a ReaxFF MD simulation system can be useful for interfacial reaction analysis in a catalysis system, hot spot formation analysis in the detonation of energetic material systems, and particularly the pyrolysis or oxidation processes of coal, biomass, polymers, hydrocarbon fuels, and energetic materials.

Six ternary lanthanide complexes formulated as [Ln(2, 4, 6-TMBA)₃(5, 5'-DM-2, 2'-bipy)]₂ (Ln = Pr 1, Nd 2, Sm 3, Eu 4, Gd 5, Dy 6; 2, 4, 6-TMBA = 2, 4, 6-trimethylbenzoate; 5, 5'-DM-2, 2'-bipy = 5, 5'-dimethyl-2, 2'-bipyridine) have been synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction, elemental analysis, thermogravimetric analysis, etc. The results of crystal diffraction analysis show that complexes 1–6 are binuclear units, crystallizing in the triclinic Pī space group. Complexes 1–5 are isostructural, and each of the central metal ions has a coordination number of 9. The asymmetric unit of complexes 1–5 consists of one Ln³⁺, one 5, 5'-DM-2, 2'-bipy ligand, and three 2, 4, 6-TMBA^- moieties with three coordination modes: chelation bidentate, bridging bidentate, and bridging tridentate. The coordination geometry of Ln³⁺ is distorted monocapped square antiprismatic. The binuclear units of complexes 1–5 form a one-dimensional (1D) supramolecular chain along the c-axis via π–π stacking interactions between the 2, 4, 6-trimethylbenzoic acid rings. The 1D chains are linked to form a supramolecular two-dimensional (2D) sheet in the bc plane via π–π stacking interactions between the pyridine rings. Although the molecular formulae of complex 6 and complexes 1–5 are similar, the coordination environment of the lanthanide ions is different in the two cases. The asymmetric unit of complex 6 contains a Dy³⁺ ion coordinated by a bidentate 5, 5'-DM-2, 2'-bipy and three 2, 4, 6-TMBA^- ligands adopting bidentate and bridging bidentate coordination modes. The Dy³⁺ metal center has a coordination number of 8, with distorted square antiprismatic molecular geometry. The binuclear molecule of 6 is assembled into a six-nuclear unit by π–π weak staking interactions between two 5, 5'-DM-2, 2'-bipy ligands; then, adjacent six-nuclear units form a 1D chain via offset π–π interactions between 5, 5'-DM-2, 2'-bipy ligands on different adjacent units. The adjacent 1D chains are linked by C―H···O hydrogen bonding interactions to form a 2D supramolecular structure. The thermal stability and thermal decomposition mechanism of all the complexes are investigated by the combination of thermogravimetry and infrared spectroscopy (TG/FTIR) techniques under a simulated air atmosphere in the temperature range of 298–973 K at a heating rate of 10 K·min^-1. Thermogravimetric studies show that this series of complexes have excellent thermal stability. During the thermal decomposition of the complex, the neutral ligand is lost first, followed by the acid ligand, and finally, the complex is decomposed into rare earth oxides. The three-dimensional infrared results are consistent with the thermogravimetric results. The photoluminescence spectra of complex 4 show the strong characteristic luminescence of Eu³⁺. The five typical emission peaks at 581, 591, 621, 651, and 701 nm correspond to the ⁵D₀ → ⁷F₀, ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂, ⁵D₀ → ⁷F₃, and ⁵D₀ → ⁷F₄ electronic transitions of Eu³⁺, respectively. The emission at 621 nm is due to the electric dipole transition ⁵D₀ → ⁷F₂, while that at 591 nm is assigned to the ⁵D₀ → ⁷F₁ the magnetic dipole transition. The lifetime (τ) of complex 4 is calculated as 1.15 ms based on the equation τ = (B₁τ₁² + B₂τ₂²))/(B₁τ₁ + B₂τ₂), and the intrinsic quantum yield is calculated to be 45.1%. Further, the magnetic properties of complex 6 in the temperature range of 2–300 K are studied under an applied magnetic field of 1000 Oe.

Carbon dots (C dots) are relatively novel carbon nanomaterials that have attracted significant interest due to their unique photoluminescence, good biocompatibility, and stability. The preparation methods of C dots was usually summarized into "top-down" and "bottom-up", and mixed acid reflux is a top-down strategy that can be used to synthesize C dots, during which neutralization is a necessary step that can significantly influence the properties and potential applications of the final product. Previously, this research area mainly focused on tuning the properties of C dots by changing the starting materials and/or varying the reaction conditions; the influence of the reagents used during neutralization has been largely ignored. As the previously reported C dots prepared by mixed acid reflux were obtained from different starting materials under varied conditions, a meaningful comparison is difficult. Herein, yellow-emitting C dots were prepared by mixed acid-refluxing a carbon-rich material derived from fullerene carbon soot. For the same batch of as-prepared C dots, the influences of four reagents, i.e., NaOH, Na₂CO₃, K₂CO₃, and NH₃·H₂O, during neutralization on the structures and photoluminescence of the resulting C dots were investigated in detail. The results of thermogravimetric analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy clearly showed that the reagent used during neutralization can affect the degree of dissociation of the acidic functional groups on the C dots. This is further supported by examination of the C dot/surfactant mixtures where subtle changes in the phase behavior were observed. Structural changes of the C dots cause variations in their surface states, ultimately altering the optical characteristics, including UV-vis absorption and fluorescence. Among the treated C dots, the sample prepared with Na₂CO₃ showed the strongest emission under the same excitation wavelength, while that prepared with NH₃·H₂O exhibited a distinct red shift (~8 nm) in the emission curve. The results presented herein provide clear evidence that neutralization reagent selection is important for optimizing the properties of the resulting C dots obtained by mixed acid reflux. In addition, the photoluminescence of the C dots can be influenced by their counterions, providing a novel method for tuning the properties of C dots while explaining their behavior in saline solutions. In short, the basicity of the neutralizing reagent and the type of counterions affect the structure of the C dots surface, which brings different performances. This work reminds researchers that it is necessary to use the type of neutralizing reagent as an experimental condition when preparing C dots in the future.

This study concentrated on the production of a two-dimensional and two-dimensional (2D/2D) Ti₃C₂/Bi₄O₅Br₂ heterojunction with a large interface that applied as one of the novel visible-light-induced photocatalyst via the hydrothermal method. The obtained photocatalysts enhanced the photocatalytic efficiency of the NO removal. The crystal structure and chemical state of the composites were characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that Ti₃C₂, Bi₄O₅Br₂, and Ti₃C₂/Bi₄O₅Br₂ were successfully synthesized. The experimental results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the prepared samples had a 2D/2D nanosheet structure and large contact area. This structure facilitated the transfer of electrons and holes. The solar light absorptions of the samples were evaluated using the UV-Vis diffuse reflectance spectra (UV-Vis DRS). It was found that the absorption band of Ti₃C₂/Bi₄O₅Br₂ was wider than that of Bi₄O₅Br₂. This represents the electrons in the Ti₃C₂/Bi₄O₅Br₂ nanosheet composites were more likely to be excited. The photocatalytic experiments showed that the 2D/2D Ti₃C₂/Bi₄O₅Br₂ composite with high photocatalytic activity and stability. The photocatalytic efficiency of pure Bi₄O₅Br₂ for the NO removal was 30.5%, while for the 15%Ti₃C₂/Bi₄O₅Br₂ it was 57.6%. Moreover, the catalytic reaction happened in a short period. The concentration of NO decreased exponentially in the first 5 min, which approximately reached the final value. Furthermore, the stability of 15%Ti₃C₂/Bi₄O₅Br₂ was favorable: the catalytic rate was approximately 50.0% after five cycles of cyclic catalysis. Finally, the scavenger experiments, electron spin resonance spectroscopy (ESR), transient photocurrent response, and surface photovoltage spectrum (SPS) were applied to analyze the photocatalytic mechanism of the composite. The results indicated that the 2D/2D heterojunction Ti₃C₂/Bi₄O₅Br₂ improved the separation rate of the electrons and holes, thus enhancing the photocatalytic efficiency. In the photocatalytic reactions, the photogenerated electrons (e⁻) and superoxide radical (·O₂⁻) were critical active groups that had a significant role in the oxidative removal of NO. The in situ Fourier-transform infrared spectroscopy (in situ FTIR) showed that the photo-oxidation products were mainly NO₂⁻ and NO₃⁻. Based on the above experimental results, a possible photocatalytic mechanism was proposed. The electrons in Bi₄O₅Br₂ were excited by visible light. They jumped from the valence band (VB) of Bi₄O₅Br₂ to the conduction band (CB). Then, the photoelectrons transferred from the CB of Bi₄O₅Br₂ to the Ti₃C₂ surface, which significantly promoted the separation of the electron-hole pairs. Therefore, the photocatalytic efficiency of Ti₃C₂/Bi₄O₅Br₂ on NO was significantly improved. This study provided an effective method for preparing 2D/2D Ti₃C₂/Bi₄O₅Br₂ nanocomposites for the photocatalytic degradation of environmental pollutants, which has great potential in solving energy stress and environmental pollution.

Oxygen reduction reaction (ORR) largely governs the overall performance of fuel cells. Commercial Pt/C has long been employed as the state-of-the-art electrocatalyst for ORR. The scarcity and high price of Pt, however, have restrained the broad application of fuel cells. Thus, it is crucial to substitute commercial Pt/C with non-precious metal or metal-free electrocatalysts. Among them, heteroatom-doped metal-free electrocatalysts (DMFEs) are promising candidates. Heteroatom doping can modify the electron distribution of carbon materials, generating active sites suitable for the adsorption and reduction of oxygen. Despite significant progress in recent years, high-performance DMFEs remain rare. It is possible to obtain improved ORR activity by the introduction of more active sites to DMFEs, in combination with a large specific surface area. Since Jasinski reported cobalt phthalocyanine is active for ORR more than half a century ago (Nature 1964, 201, 1212), tremendous investigations on metallomacrocycles as ORR electrocatalysts have been carried out. Nevertheless, few studies have further enriched the active sites of DMFEs by adding metallomacrocycles. Herein, we attempt to introduce metallomacrocycles to DMFEs, and to use templates to fabricate porous nanostructures with high specific surface areas. By controlling pH, positively charged aniline monomers can be adsorbed on the negatively charged surface of SiO₂ nanospheres via electrostatic interactions. After in situ polymerization of aniline monomers, a polyaniline (PANI) coated SiO₂ (SiO₂@PANI) composite was formed. To introduce more active components, Fe^Ⅲ tetrakis(4-methoxyphenyl) porphyrin (FeP) was deposited on the surface of SiO₂@PANI by rotary evaporation method. After pyrolysis and removal of the template, FeP-modified porous PANI-based electrocatalysts were synthesized. Remarkably, the resultant 40%FeP/PANI-18-700 electrocatalysts demonstrate a high ORR activity, in terms of a half-wave potential (E_1/2) of 0.843 V (vs. reversible hydrogen electrode (RHE)) in 0.1 mol·L^-1 KOH aqueous solution, which is better than that of most DMFEs, and comparable to that of commercial Pt/C. The improvement of the ORR activity likely originates from the abundant pore structure (18 nm average pore diameter, pore volume of 1.1 cm³·g^-1), large surface area (687.5 m²·g^-1), and high N content (6.4%). Only 25 mV degradation of E_1/2 was observed for 40%FeP/PANI-18-700 during the accelerated durability test, in contrast to a 74 mV negative shift of E_1/2 for commercial Pt/C. Additionally, a hydroxide exchange membrane fuel cell (HEMFC) fabricated with 40%FeP/PANI-18-700 as the cathode approaches a peak power density of 42 mW·cm^-2. The results exhibit 40%FeP/PANI-18-700 may have potential applications in HEMFCs. Our strategy highlights a new avenue for the design and synthesis of non-precious metal electrocatalysts toward ORR in alkaline media.

Direct formic acid fuel cells involve two significant half-reactions, namely formic acid electro-oxidation and oxygen reduction reaction, and the more sluggish and complex process for anode formic acid oxide also determine the whole fuel cells energy conversion efficiency. The most efficient catalysts rely on the noble metal of Pt and Pd based catalysts and compared with Pt catalysts, Pd catalyst is more appealing because of the low CO poisoning effect during the electro-oxidation of formic acid that mainly follows the direct pathway. The Pd alloy effect and support effect should be considered for the catalyst fabrication since the resulted structure and electronic modification could largely increase the catalytic performance. Graphene emerges out as novel support while the easy agglomeration and destruction of pure graphene do not guarantee promising merits. In this work, we demonstrated the formic acid oxidation ability boosting by facile coupling PdNi alloy and 3D graphene aerogel (PdNi/GA) via a freezing-drying/thermal annealing reduction approach. The PdNi alloy crystal structure was well confirmed by the X-ray diffractions technique and the alloy nanoparticles were successfully anchored on the 3D graphene aerogel surface. The electrochemical performance was evaluated for formic acid oxidation in the acid electrolyte. The PdNi/GA catalyst displayed a larger peak current density of 136 mA·cm^-2, which was 2 and 3.45 times greater than Pd/GA (68 mA·cm^-2) and Pd/C (39.4 mA·cm^-2), respectively. The anti-CO poisoning ability was measured by CO stripping technique, and a low onset potential of 0.49 V was found on PdNi/GA catalyst, about 120 mV less than that of Pd/GA catalyst, indicating the oxophilic property of Ni to assist formic acid oxidation via the bi-functional mechanism. The oxidation peak potential of 0.67 V was observed on PdNi/GA, about 40 mV less than that of Pd/C catalyst, indicating the merits of 3D structure of graphene. Moreover, PdNi/GA catalyst had the highest mass activity of 1699 mA·mg^-1 compared to Pd/GA (851 mA·mg^-1) and Pd/C (537 mA·mg^-1) catalysts. The specific activity of PdNi/GA was 2.6 mA·cm^-2, which was 1.94 and 2.7 times of Pd/GA (1.34 mA·cm^-2) and Pd/C (0.96 mA·cm^-2) catalysts. The highly improved catalytic performance could be due to the combined alloy and support effect. The PdNi/GA was a promising catalyst for application in the direct formic acid fuel cells.

Proton exchange membrane fuel cells (PEMFCs) are considered one of the most promising technologies for efficient power generation in the 21st century. However, several challenges for the PEMFC power technology are associated with low operating temperature, such as complex water management and strict fuel purification. PEMFC operating at high temperature (HT, 100–200 ℃) has in recent years been recognized as a promising solution to meet these technical challenges. At present, HT-PEMFC based on phosphoric acid (PA)-doped polybenzimidazole (PBI) is considered to be the trend of PEMFC future development due to its good environmental tolerance and simplified water/ thermal management. In this HT-PEMFC system, the proton transfer in both catalyst layer (CL) and membrane relies on liquid PA. Thus, a proper amount of PA is required to impregnate the membrane and the CL in order to achieve good proton conductivities in an HT-PEMFC system. Therefore, reducing the loss of PA electrolyte in the membrane electrode assembly (MEA) is crucial to maintaining the good durability of HT-PEMFC. In this work, a Schiff base networks (SNW)-type covalent organic framework (COF) material is proposed as the CL additive to enhance the durability of HT-PEMFC. The well-defined porous structure and tailored functional groups endow the proposed COF network with not only excellent PA retention capacity but also good proton transfer ability, thus leading to the superior durability of the HT-PEMFC in an accelerated stress test (AST). After 100 h operation at heavy load (0.2 V) and high flow rate of air purge, the accumulative PA loss of the COF-based MEA was ~4.03 mg, which is almost an order of magnitude lower than that of the conventional MEA (~13.02 mg), consequently leading to a much lower degradation rate of current density (~0.304 mA·cm^-2·h^-1) than that of the conventional MEA (~1.01 mA·cm^-2·h^-1). Moreover, it was found that the electrode incorporating a proper amount (5%–10%, mass fraction) of the COF material possessed a higher electrochemical surface area (ECSA) and lower ohmic and charge transfer resistances, which further improved the performance of the HT-PEMFC. At the usual operating voltage of 0.6 V, the current density of the MEA containing 10% COF was up to 0.361 A·cm^-2, which is ~30% higher than that of the conventional MEA at 150 ℃, H₂/Air and ambient pressure. These results indicate that incorporating COF materials into CL is a promising strategy to enhance the performance and durability of HT-PEMFC.

In-depth understanding of the mechanisms of hydrogen sulfide (H₂S) adsorption on catalysts during desulfurization from industrial waste gas streams is important for developing effective catalysts to be used in the decomposition of H₂S. In this work, the dissociation behavior of H₂S adsorbed on a single-atom catalyst (Ti or V-decorated Ti₂CO₂ surface) was investigated by performing density functional theory (DFT) calculations. The corresponding diffusion behavior revealed that Ti or V atoms could be dispersed on the Ti₂CO₂ monolayer, without aggregation in the form of single atoms. In addition, analyses of the partial density of states (PDOS), Hirshfeld charges, and electron density difference indicated that the decorated Ti or V atoms led to charge redistribution on the Ti₂CO₂ surface and significantly improved the interaction between the H₂S gas molecules and Ti₂CO₂, thereby enhancing the catalytic activity of V/Ti₂CO₂. In order to gain a deeper understanding of the mechanism of H₂S decomposition (H₂S → HS* + H* → H₂ + S*), a comparative analysis of the results for the decomposition of H₂S on the Ti/Ti₂CO₂ and V/Ti₂CO₂ surfaces was carried out. The catalytic dissociation behavior of H₂S is explained as follows: once H₂S is adsorbed on the V/Ti₂CO₂ or Ti/Ti₂CO₂ surface, it spontaneously dissociates into HS*/H* without any energy barrier on the catalyst surface. Subsequently, the V atoms would not only promote the cleavage of the H-S bond, but also play a major role in the formation of S atoms. Moreover, the rate-limiting step for the entire process proceeded on the Ti/Ti₂CO₂ surface with an energy barrier of 0.86 eV, while that for V/Ti₂CO₂ was 0.28 eV, indicating that the H₂S molecules easily dissociated into S and H₂ on the V/Ti₂CO₂ surface at room temperature. The reaction time for H₂S decomposition on the V/Ti₂CO₂ surface at 500 K was 65.79 ns, which was almost two orders of magnitude higher than that at room temperature. Thus, the decomposition of H₂S on the V-doped Ti₂CO₂ surface is associated very fast kinetics. Furthermore, the S atoms can form elemental sulfur with aggregation on the V/Ti₂CO₂ surface to promote recycling reactions. Compared with previously reported catalytic systems, the single-atom catalyst (SAC) V/Ti₂CO₂ catalyst has greater application prospects in terms of sustainable economy or removal efficiency for H₂S treatment. Our results suggest that V-doped Ti₂CO₂ is an excellent candidate for a highly effective non-noble metal catalyst applicable to H₂S decomposition.

Metal-organic frameworks (MOFs) are of significant interest for photocatalysis using visible light, but they are typically limited by the instability and high recombination ratio of photoexcited pairs. Integrating MOFs into an inorganic semiconductor is one of the most widespread methods to promote their activity. In this study, a core-shell structured MOF@TiO₂ (NH₂-UiO-66@TiO₂) was synthesized as an efficient photocatalyst for the degradation of toluene. Pristine NH₂-UiO-66 was synthesized by a hydrothermal method as the core, which was then coated with an amorphous TiO₂ shell. Compared with pristine NH₂-UiO-66 and other samples prepared by the direct mixing of NH₂-UiO-66 and TiO₂, NH₂-UiO-66@TiO₂ exhibited a higher degradation rate of toluene. Using NH₂-UiO-66@TiO₂ as a catalyst, the degradation efficiency of toluene reached 76.7% within 3 h, which is 1.48 times higher than that of NH₂-UiO-66. The degradation performance was also stable in four repeated reuse experiments, and the slight deactivation was reactivated after washing with ethanol. A series of characterization methods were used to determine the physicochemical properties of NH₂-UiO-66@TiO₂, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Using the measured physicochemical properties, the photocatalytic mechanism of NH₂-UiO-66@TiO₂ was explored. NH₂-UiO-66 is an ideal photocatalyst, with visible-light response and a huge specific surface area (914.9 m²·g^-1), which is favorable for the utilization of sunlight as well as the absorption of pollutants in indoor air. In addition, a new interface formed between the two components (NH₂-UiO-66 and TiO₂), which efficiently broaden the light absorption area and enhanced the utilization of photogenerated species. The photogenerated holes and electrons could transfer through the interlayer as soon as they were formed. It is speculated that holes would transfer to the HOMO of NH₂-UiO-66, and then combine with H₂O molecules to form hydroxyl radicals (·OH). At the same time, more electrons tended to combine with oxygen molecules in the conduction band of TiO₂ rather than recombine with holes. Consequently, the recombination rate of electrons and holes decreased, while the quantity of oxygen radicals and hydroxyl radicals increased. Toluene was efficiently oxidized by these two types of radicals. Owing to the outstanding properties mentioned above, the strategy of constructing NH₂-UiO-66@TiO₂ is considered to be an effective approach. This work may provide new insights into the design of core-shell structured MOF@photocatalysts for the photocatalytic degradation of indoor air pollutants.

Photocatalytic oxidation is a promising technology for governing emission of environmental pollutants and managing energy crisis. Typically, the photocatalytic performance of photocatalysts is highly dependent on the type of exposed crystal surfaces. As a semiconductor oxide photocatalyst, the different exposed crystal surfaces of bismuth oxyiodide (BiOI) exhibit different photocatalytic oxidation performances. In this study, we chose BiOI as the model material and provided a novel method to improve the photocatalytic oxidation performance by regulating the main exposed crystal facets. Using boron nitride (BN) nanosheets as the templates, two-dimensional/two-dimensional (2D/2D) BiOI/BN nanocompounds were fabricated via an in situ growth method. Owing to the electrostatic interaction, the positively charged BiOI {001} facets prefer to contact the negatively charged BN {001} facet, thus inducing the exposure of BiOI {110} facets. This was identified via X-ray diffraction and transmission electron microscopy analyses. Compared with BiOI {001} facets, there were more lattice oxygen atoms in the BiOI {110} facets. Thus, the exposure of BiOI {110} facets would promote more surface lattice oxygen atoms exposed on the surface of BiOI, which was confirmed by X-ray photoelectron spectroscopy and density functional theory calculations. To evaluate the photocatalytic oxidation performance of BiOI/BN, the photocatalytic NO oxidation reaction was tested under visible light irradiation (λ > 420 nm). Among all the nanocompounds, the BiOI/BN-1.0:1.4 nanocompound exhibited the best NO oxidation ratio of 44.2%, which was almost 30 times higher than that of pristine BiOI (1.4%). The enhanced photocatalytic activity could be attributed to the following two aspects. One, the successful combination of BN effectively promoted the separation of photogenerated carriers, which was identified by steady-state and time-resolved fluorescence spectra, transient photocurrent responses, and electrochemical impedance spectra. Two, benefiting from the introduction of BN nanosheets, BiOI tends to mainly expose the oxygen-rich {110} facets. As a result, the content of O on the BiOI surface increased from 38.3% to 46.6%. Thus, NO preferred to adsorb on the {110} facets of BiOI nanosheets, which was confirmed by theoretical and experimental results. More importantly, the adsorbed NO spontaneously combined with the lattice oxygen atom of the BiOI (110) surface to form nitrogen dioxide (NO₂). These findings can provide a novel strategy to tune exposed oxygen-rich facets by constructing 2D/2D photocatalysts for ensuring efficient photocatalytic oxidation performance.

Photocatalytic oxidation has been widely acknowledged as an economical and effective technology for the treatment of low-concentration NO. Three-dimensional (3D) BiOI microspheres, which are typical visible-light responsive semiconductor photocatalysts, often suffer from quick recombination of photogenerated carriers and unsatisfactory electrical conductivity when applied in NO photocatalytic oxidation reactions. However, owing to their micro-sized structures, they are usually difficult to couple with other semiconductors and co-catalysts because of their incompact interfaces that provide insufficient contact. In this study, a rare-earth metal (La) doping strategy was first adopted to modify BiOI microspheres via a simple one-step solvothermal method; subsequently, the photocatalytic NO oxidation performance under visible light illumination was systematically investigated. Further, the La precursors and doping contents were optimized. It was found that La(NO₃)₂ was the best precursor when compared to LaCl₃ and La(AC)₃. Moreover, 0.3%La/BiOI exhibited the best NO photocatalytic conversion efficiency of up to 74%, which was significantly higher than that of the pure BiOI benchmark (44%). It also exhibited excellent stability during the continuous 5-cycle experiments. Analysis of the physicochemical properties revealed that La doping facilitated the crystallization of BiOI without altering its morphology and structure. La³⁺ may enter the BiOI lattice by substituting Bi³⁺ or forming La₂O₃ nanoclusters that homogeneously scatter in the mesopores of BiOI microspheres. The analysis of the underlying mechanism further revealed that La doping not only enhanced the light harvesting properties by decreasing the bandgaps of BiOI and accelerating the charge separation and transfer dynamics, but also introduced more oxygen vacancies and facilitated the formation of more OH radicals by dissociating the water molecules. All these factors co-contributed to the promotion of NO photocatalytic oxidation activities. Furthermore, NO was mainly oxidized to NO₂ over La/BiOI, and the formed NO₂ tended to desorb from the catalyst surface, which not only maintained the intactness of active sites and facilitated the sustainable occurrence of NO photocatalytic oxidation reactions, but also prevented the photocatalysts from frequent washing-regeneration; therefore, these factors account for the superior photocatalytic stability of La/BiOI and its long-term operation. The formed NO₂ could be easily and totally absorbed by the tail alkaline liquid, thereby effectively avoiding secondary pollution. Therefore, this study elucidates that doping is indeed a feasible and effective approach for the modification of 3D BiOI microspheres, while providing inspiration for the rational design and modification of other 3D semiconductor materials for various photocatalytic applications.

Energy crisis has become a serious global issue due to the increasing depletion of fossil fuels; therefore, it is crucial to develop environmentally friendly and renewable energy resources, such as hydrogen (H₂), to replace fossil fuels. From this viewpoint, photocatalytic H₂ production is considered as one of the most promising technologies. Noble metal platinum (Pt) can be applied as an efficient cocatalyst for improving the H₂ production performance of photocatalytic systems; however, its high cost limits its further application. Thus, the development of novel, high-activity, and low-cost cocatalysts for replacing noble metal cocatalysts is of great significance for use in photocatalytic H₂ evolution techniques. Herein, we successfully synthesized a Ni₂P/graphite-like carbonitride photocatalyst (Ni₂P/CN) using a conjugated polymer (SCN)_n as precursor for enhanced photocatalytic H₂ production under visible light illumination. Various characterization techniques, including optical and photoelectronic chemical tests, were used to investigate the structural composition, morphology, and light adsorption ability of these materials. X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy results showed that Ni₂P/CN nanocomposites with good crystal structure were obtained. Scanning electron microscopy and transmission electron microscopy results revealed that the Ni₂P/CN samples had a typical two-dimensional layered structure, and the Ni₂P nanoparticles were uniformly loaded on the surface of the CN to form a non-noble metal promoter. UV-Vis diffuse reflectance spectra results demonstrated that the loading of Ni₂P nanoparticles effectively enhances the adsorption capacity of CN to visible light. Photoluminescence spectroscopy and photocurrent (PL) results suggested that Ni₂P loading to CN is beneficial for promoting the migration and separation efficiency of photogenerated carriers. Photocatalytic H₂ production was conducted under visible light irradiation with triethanolamine as a sacrificial agent. The results suggest that the Ni₂P/CN composite photocatalysts exhibit excellent photocatalytic reduction performance. In particular, the H₂ evolution rate of the optimal Ni₂P/CN nanocomposite is 623.77 μmol·h^-1·g^-1, which is higher than that of CN modified by noble metal Pt, i.e., 524.63 μmol·h^-1·g^-1. In conclusion, Ni₂P nanoparticles are homogeneously attached to the surface of CN, and a strong interfacial effect exists between them, thereby forming an electron transfer tunnel that greatly inhibits the recombination of photoinduced carriers and promotes the migration of electrons from CN to Ni₂P. In addition, a possible photocatalytic mechanism is proposed based on the experiments and characterizations. This work has profound significance for developing non-noble metal cocatalysts for the substitution of noble metal cocatalysts for high-efficiency photocatalytic H₂ evolution.

Vacuum ultraviolet irradiation coupled with photocatalytic oxidation (VUV-PCO) is an efficient and promising method for eliminating pollutants at room temperature; it involves three processes: vacuum ultraviolet (VUV) photolysis, photocatalytic oxidation (PCO), and ozone catalytic oxidation. Herein, toluene was chosen as the representative volatile organic compound (VOC), which is one of the most important precursors to form fine particulate matter and photochemical smog, because of its high toxicity and extensive existence in industries. All experiments were performed in a fixed-bed continuous-flow reactor that contained units for VUV photolysis and PCO. Mesoporous P-Mn-TiO₂ was prepared by one-step hydrolysis and used as a catalyst for the oxidation of gaseous toluene under VUV irradiation through the VUV-PCO process. The as-prepared P-Mn-TiO₂ samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), ultraviolet-visible light (UV-Vis) spectroscopy, and X-ray diffraction (XRD) analysis to determine the physicochemical properties of the catalysts and to determine the mechanisms of Mn doping and phosphoric acid modification and the effects of these processes on photocatalytic activity, ozone catalytic activity, and adsorption performance. The results indicated that the synergistic effect of phosphoric acid modification and Mn doping can improve the ozone catalytic activity and photocatalytic performance by increasing the number of oxygen active sites, completely eliminating the outlet ozone, and simultaneously promoting the efficient degradation of toluene. Moreover, doping TiO₂ with Mn³⁺ significantly enhanced light harvesting, and numerous oxygen vacancies can be generated on the catalyst surface because of the presence of doped Mn³⁺ in the lattice, which adsorbs and transforms the oxygen species for toluene degradation. In addition, modification with an appropriate amount of phosphate groups can facilitate O₂ and O₃ adsorption on the TiO₂ surface that can favor photo-induced charge carrier separation, thereby significantly improving the photocatalytic and ozone catalytic activities. The excellent catalytic performance of mesoporous P-Mn-TiO₂ for toluene degradation and outlet ozone elimination was ascribed to the formation of highly reactive oxidizing species such as O(1D), O(3P), and ·OH via the catalytic decomposition of O₃ adsorbed on the oxygen vacancy sites containing Mn and phosphate groups on the catalyst surface. In the VUV-PCO process, toluene was first destructed via VUV photolysis and oxidized by residual O₃ generated from VUV photolysis and the active oxygen species formed in the presence of the catalyst. Finally, toluene and the generated intermediate products were oxidized and degraded to CO₂ and H₂O through VUV-PCO. In addition, the outlet ozone byproduct was simultaneously eliminated by the multifunctional catalyst.

Excessive use of ciprofloxacin (CIP) has proven to be a significant threat to the ecological environment. In this work, a novel Fe-free photo-electro-Fenton system was designed for the degradation of CIP in water. The NiO/g-C₃N₄ composites were synthesized by a simple solvothermal method. The crystalline phases and chemical compositions of the different catalysts were determined via X-ray diffraction (XRD) analysis. Fourier transform infrared (FT-IR) spectroscopy further confirmed the molecular structures of the different composites. The results proved the successful synthesis of NiO/g-C₃N₄ composites. The morphology of the material was obtained using scanning electron microscopy (SEM), which showed that the structure of the optimal NiO/g-C₃N₄-60% was two-dimensional and flower-like. The transmission electron microscopy (TEM) analysis further proved that the NiO/g-C₃N₄-60% possessed a layered structure. Owing to the layered structure, the NiO/g-C₃N₄-60% boasts of a large specific surface area and abundant active sites, which were beneficial for the transmission of electrons and oxidation of CIP. Furthermore, it was evident from the X-ray photoelectron spectroscopy (XPS) analysis that the Ni²⁺ and Ni³⁺ coexisted, and there was low coordination oxygen with defects in the NiO/g-C₃N₄-60% composite. The electron paramagnetic resonance (EPR) spectrum also proved the existence of oxygen vacancies, which not only facilitated the activation of H₂O₂, but also promoted the formation of stable mixed valence states of metal ions. UV-vis diffuse reflection spectrum (UV-Vis DRS), photoluminescence (PL), and electrochemical tests showed that NiO/g-C₃N₄-60% exhibited the strongest light absorption capacity, lowest charge transfer resistance, and fastest charge separation efficiency, which was beneficial for the generation of active species and the rapid degradation of CIP. Therefore, the flower-like NiO/g-C₃N₄-60% composites exhibited photoelectric synergy in the photo-electro-Fenton process. They not only effectively decomposed the H₂O₂ produced in the electro-Fenton process into ·OH by the conversion of Ni³⁺/Ni²⁺, but also generated photogenerated electrons and holes to promote the production of ·OH, ·O₂^–, and h⁺ under light irradiation to improve the degradation efficiency of CIP. When the optimal NiO/g-C₃N₄-60% served as a catalyst in the photo-electro-Fenton system, the degradation efficiency of CIP reached approximately 100% in 90 min and the mineralization efficiency reached 82.0% in 120 min. In addition, compared with the traditional Fenton system (the optimal pH value of which is 2.8–3.5), the novel photo-electro-Fenton system possessed a wider range of pH, with a final CIP degradation efficiency of 78.8% at a pH value of 6. The NiO/g-C₃N₄-60% also demonstrated excellent structural stability in the photo-electro-Fenton system. After five consecutive cycles, the degradation efficiency was maintained at 96.3%. Based on the results of high-performance liquid chromatography-mass spectrometry (HPLC-MS), two possible pathways for CIP degradation were proposed. This study provides a theoretical basis for the rapid degradation of antibiotics in wastewater.

Photocatalytic reduction of carbon dioxide into chemical fuels is a promising route to generate renewable energy and curtail the greenhouse effect. Therefore, various photocatalysts have been intensively studied for this purpose. Among them, g-C₃N₄, a 2D metal-free semiconductor, has been a promising photocatalyst because of its unique properties, such as high chemical stability, suitable electronic structure, and facile preparation. However, pristine g-C₃N₄ suffers from low solar energy conversion efficiency, owing to its small specific surface area and extensive charge recombination. Therefore, designing g-C₃N₄ (CN) nanosheets with a large specific surface area is an effective strategy for enhancing the CO₂ reduction performance. Unfortunately, the performance of CN nanosheets remains moderate due to the aforementioned charge recombination. To counter this issue, loading a cocatalyst (especially a two-dimensional (2D) one) can enable effective electron migration and suppress electron-hole recombination during photo-irradiation. Herein, CN nanosheets with a large specific surface area (97 m²·g^-1) were synthesized by a two-step calcination method, using urea as the precursor. Following this, a 2D/2D FeNi-LDH/g-C₃N₄ hybrid photocatalyst was obtained by loading a FeNi layered double hydroxide (FeNi-LDH) cocatalyst onto CN nanosheets by a simple hydrothermal method. It was found that the production rate of methanol from photocatalytic CO₂ reduction over the FeNi-LDH/g-C₃N₄ composite is significantly higher than that of pristine CN. Following a series of characterization and analysis, it was demonstrated that the FeNi-LDH/g-C₃N₄ composite photocatalyst exhibited enhanced photo-absorption, which was ascribed to the excellent light absorption ability of FeNi-LDH. The CO₂ adsorption capacity of the FeNi-LDH/g-C₃N₄ hybrid photocatalyst improved, owing to the large specific surface area and alkaline nature of FeNi-LDH. More importantly, the introduction of FeNi-LDH on the CN nanosheet surface led to the formation of a 2D/2D heterojunction with a large contact area at the interface, which could promote the interfacial separation of charge carriers and effectively inhibit the recombination of the photogenerated electrons and holes. This subsequently resulted in the enhancement of the CO₂ photo-reduction activity. In addition, by altering the loading amount of FeNi-LDH for photocatalytic performance evaluation, it was found that the optimal loading amount was 4% (w, mass fraction), with a methanol production rate of 1.64 μmol·h^-1·g^-1 (approximately 6 times that of pure CN). This study provides an effective strategy to improve the photocatalytic CO₂ reduction activity of g-C₃N₄ by employing 2D layered double hydroxide as the cocatalyst. It also proposes a protocol for the successful design of 2D/2D photocatalysts for solar energy conversion.

Asymmetric manganese cluster, the active center of photosystem II (PSII) in nature, is hydrogen-bonded to surrounding amino acid residues and water molecules. This phenomenon is of great inspiration significance for developing and studying artificial Mn-based oxygen evolution reaction (OER) catalysts. Herein, we prepared manganese phosphate nanosheets through intercalation of ethylenediamine ions and water molecules ((EDAI)(H₂O)MnPi) using a simple co-precipitation method. (EDAI)(H₂O)MnPi is also hydrogen-bonded to interlayer ethylenediamine ions and water molecules, forming a hydrogen-bonding network. The morphology of the (EDAI)(H₂O)MnPi sample was characterized by scanning electron microscopy (SEM) and transmission electron microscopy. The thickness of (EDAI)(H₂O)MnPi was characterized by atomic force microscopy. The composition and structure of (EDAI)(H₂O)MnPi were characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy. For control studies, manganese phosphate (EDAI)MnPi and (H₂O)MnPi samples were also synthesized. The structure and morphology of (EDAI)MnPi and (H₂O)MnPi samples were characterized by XRD and SEM. The difference between (EDAI)(H₂O)MnPi, (EDAI)MnPi, and (H₂O)MnPi were further characterized by thermal gravimetric analysis and derivative thermogravimetric analysis. Electrocatalytic properties of the (EDAI)(H₂O)MnPi, (EDAI)MnPi, and (H₂O)MnPi for OER were studied in 0.05 mol∙L⁻¹ pH = 7 phosphate buffered saline solution, through linear sweep voltammetry, electrochemical impedance spectroscopy, and controlled potential electrolysis (CPE) test. The electrochemical surface area (ECSA) analyses of (EDAI)(H₂O)MnPi, (EDAI)MnPi, and (H₂O)MnPi samples were recorded by charging currents in the non-Faradaic potential region at different scan rates. Considering the different ECSAs of different materials, the water oxidation activities of three materials were normalized by ECSA. Compared with counterparts of (EDAI)MnPi (610 mV) and (H₂O)MnPi (580 mV), manganese phosphate nanosheets (EDAI)(H₂O)MnPi exhibited a lower overpotential of 520 mV when driving a current density of 1 mA∙cm⁻² in neutral conditions. The CPE experiment revealed that (EDAI)(H₂O)MnPi remained active for at least 10 h. Manganese phosphate nanosheets containing a rich, extensive, and continuous hydrogen bond network exhibited improved OER performance in neutral conditions. The hydrogen-bonding network in manganese phosphate nanosheets has similar functions to the hydrogen-bonding network in PSII, which could accelerate the transfer rate of protons and facilitate electrocatalytic water oxidation. This study may provide guidance for the design of water oxidation catalysts with rich hydrogen bond network.

With the rapid development of human society, clean energy forms are imperative to sustain the normal operations of various mechanical and electrical facilities under a cozy environment. Hydrogen is considered among the most promising clean energy sources for the future. Recently, electrochemical water splitting has been considered as one of the most efficient approaches to harvest hydrogen energy, which generates only non-pollutant water on combustion. However, the sluggish anodic oxygen evolution reaction significantly restricts the efficiency of water splitting and requires a relatively high cell voltage to drive the electrolysis. Therefore, seeking a thermodynamically favorable anodic reaction to replace the sluggish oxygen evolution reaction by utilizing highly active bifunctional electrocatalysts for the anodic reaction and hydrogen evolution are crucial for achieving energy-efficient hydrogen production for industrial applications. Nevertheless, it is known that the oxygen evolution reaction can be replaced with other useful and thermodynamically favorable reactions to reduce the electrolysis voltage for realizing energy-efficient hydrogen production. Therefore, in this study, we present a bifunctional nickel nanoparticle-embedded carbon (Ni@C) prism-like microrod electrocatalyst synthesized via a two-step method involving the synthesis of a precursor metal-organic framework-74 and subsequent carbonization treatment for methanol oxidation and hydrogen evolution. The interfacial structure consisting of a nickel and carbon skeleton was realized via in situ carbonization. However, the dispersed nickel nanoparticles do not easily aggregate owing to the partition by the surrounding carbon as it would sufficiently expose the active Ni sites to the electrolytes, ensuring fast charge transfer between the catalyst and electrolytes by accelerating the electrochemical kinetics. In the anodic methanol oxidation, the products were detected as carbon dioxide and formate with faradaic efficiencies of 36.2% and 62.5%, respectively, at an applied potential of 1.55 V. Meanwhile, the Ni@C microrod catalyst demonstrated high activity and durability (2.7% current decay after 12 h of continuous operation) toward methanol oxidation, which demonstrates that methanol oxidation precedes oxidation under voltage forces. Notably, the bifunctional catalyst not only exhibits excellent performance toward methanol oxidation but also yields a low overpotential of 155 mV to drive 10 mA∙cm⁻² toward hydrogen evolution in 1.0 mol∙L⁻¹ KOH aqueous solution with 0.5 mol∙L⁻¹ methanol at room temperature, which guarantees the hydrogen production efficiency. More importantly, the constructed two-electrode electrolyzer produced a current density of 10 mA∙cm⁻² at a low cell voltage of 1.6 V, which decreased by 240 mV after replacing the oxygen evolution reaction with methanol oxidation.

The existing energy and environmental issues are the primary issues that restrict the continual development of the mankind. Cost-effective energy storage and conversion devices have attracted significant attention. Rechargeable zinc-air batteries (ZABs) are widely studied because they are portable, possess high power density, and are environmentally friendly. However, the slow kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) limit their practical application. It is crucial to develop dual-functional electrocatalysts with excellent electrocatalytic performance, low price, simple operation, and outstanding stability. Therefore, transition metals and carbon-based materials should be combined. Although Co₂P has been widely reported as an efficient OER catalyst, there are few studies based on the ORR activity. Herein, a facile pyrolysis of cobalt salt, phytic acid, and k-carrageenan aerogel was carried out on Co₂P nanoparticles within P-doped porous carbon (Co₂P-PCA-800), showing enhanced ORR activity. The resulting composite (Co₂P-PCA-800) with a three-dimensional (3D) hierarchical porous architecture exhibited outstanding ORR activity with a high half-wave potential (E_1/2) of approximately 0.84 V, which is comparable to that of Pt/C. Simultaneously, we fabricated phosphorus-doped porous carbon (PCA) and cobalt-doped porous carbon (Co-CA) to compare the effect of structural morphology on the catalytic performance. Studies have found that a regular interconnected porous structure can be beneficial for mass transfer and can ensure uniform distribution of ion current, thereby resulting in increased number of effective active sites. The outstanding ORR activity mainly results from the synergistic effect of the 3D honeycomb hierarchical porous structure and positively charged Co₂P nanoparticles encapsulated in P-doped carbon. In addition, the 3D honeycomb porous carbon structure not only facilitates mass transfer and accelerates electron transfer but also protects the cobalt phosphide. Finally, we assembled a rechargeable ZAB with Co₂P-PCA-800 as the air cathode catalyst. Compared with precious metal catalysts, the catalyst has considerable charge-discharge performance and energy density as well as higher specific capacity and better cycle stability. We believe that this study will provide a significant direction for solving energy and environmental issues.

In recent years, electrochemical water splitting that involves the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has attracted widespread attention because the process is clean, environmentally friendly, and the generated oxygen/hydrogen gas can be converted into electricity in a fuel cell. However, the HER and OER kinetics are sluggish and require highly efficient electrocatalysts for enhancing the reaction rate. Currently, precious metals such as Pt and RuO₂ have shown excellent HER and OER performance, respectively, but their practical applications are limited by their scarcity and high price. Therefore, the use of 3d transition metals, such as iron (Fe) and nickel (Ni), as electrocatalysts has attracted significant attention. To obtain a catalytic performance similar to that of precious metals, several methods have been explored, such as alloying 3d transition metals with precious metals, compositing a variety of transition metals, or requiring good carbon-based materials as a supporter. Metal-organic framework (MOF)-derived nanomaterials have emerged as some of the most promising non-precious metal bifunctional electrocatalysts. The MOF structure consists of metal-based units and special organic ligands, and after annealing, metal atoms can be converted into unsaturated metal-based active sites, and the organic ligands can be converted into carbon support. This could accelerate the charge transfer efficiency and can be beneficial for achieving excellent HER and OER performance. However, bifunctional electrocatalysts derived from nickel (Ni)-based MOFs have not been studied intensively, and their catalytic activity and stability remain to be improved. Herein, a Ni-MOF precursor was synthesized via a liquid-phase coordination reaction using Ni²⁺ and benzene-1, 3, 5-tricarboxylic acid. The obtained Ni-MOF samples were annealed under H₂/Ar atmosphere at 600, 700, and 800 ℃, named Ni/C-H₂-600, Ni/C-H₂-700, Ni/C-Ar-700, and Ni/C-H₂-800, respectively. During high-temperature annealing treatment, Ni nanoparticles were grown in situ on a rod-shaped carbon substrate to form novel hybrid architecture Ni/C nanoparticles used as a high-performance bifunctional electrocatalyst for overall water splitting. The HER overpotential of Ni/C-H₂-700 was 120 mV at a current density of 10 mA∙cm⁻², which is much lower than that of Ni/C-H₂-600 (250 mV), Ni/C-H₂-800 (348 mV), and Ni/C-Ar-700 (275 mV). Ni/C-H₂-700 required an OER overpotential of 350 mV to achieve a current density of 10 mA∙cm⁻², which is lower than that of Ni/C-H₂-600 (370 mV), Ni/C-H₂-800 (430 mV), and Ni/C-Ar-700 (380 mV). Furthermore, Ni/C-H₂-700 showed the idea of HER and OER durability. Presumably, good structural properties and the abundant surface area of the carbon substrate elevated HER/OER activity owing to the synergistic advantages of accessible active sites and enhanced electronic conductivity.

In the 21st century, hydrogen energy is a novel energy source. Its use is expected to mitigate the problems of environmental pollution and global warming caused by the excessive use of conventional fossil fuels. The hydrogen evolution reaction (HER) for water splitting has attracted considerable attention because of its environmental friendliness. To improve electrocatalyst performance and reduce operation cost, carbon-based metal hybrid materials exhibiting high efficiency and catalytic activity have been developed. Among them, carbon dots (CDs) have garnered significant research attention and have been widely applied in biosensing, bioimaging, and energy conversion/storage because of their facile synthesis, biocompatibility, tunable photoluminescence, excellent stability, and good electronic properties. CDs are widely used as carriers in the construction of electrocatalysts prepared from carbon-based metal hybrid materials. At present, it is believed that CDs exhibit excellent confinement effects, which can effectively inhibit the growth and agglomeration of metal nanoparticles, thereby preparing well-distributed carbon-based metal hybrid materials with a uniform and controllable size. However, the formation process of the small-molecule raw materials of CDs has not been elucidated. In this study, CDs and small-molecule raw materials from synthetic CDs were used as precursors to prepare nitrogen-doped CD-supported ruthenium nanoparticle (Ru@CDs) and small-molecule-supported ruthenium nanoparticle (Ru@Molecule) hybrid materials, respectively. The interaction between the small molecules and Ru in the process of CD formation and the effect on HER performance were explored. Moreover, we prepared different carriers such as metal organic frameworks(MOF), carbon nanotubes (CNTs), and graphene (GO)-supported ruthenium nanoparticle hybrid materials. Among them, Ru@CDs exhibited controllable size and excellent dispersibility and exhibited outstanding HER activity and good stability. Ru@CDs were found to require a low overpotential of 22 mV to reach a current density of 10 mA·cm⁻². Moreover, we observed the presence of an intermediate state between the molecules and CDs and demonstrated that the intermediate state exhibits no confinement effect. Furthermore, we found that with increasing calcination temperature, the intermediate state gradually changes to CDs. The unique spatial confinement between CDs and metal ions is key to the formation of monodisperse Ru nanoparticles. Our results confirmed that Ru@CDs serve as excellent HER catalyst supports. This work not only reveals the effect of the unique spatial confinement of CDs on the supported metals and their promoting effect on electrocatalytic activity but also provides guides the future development of CD-based metal hybrid electrocatalysts.

The continuous consumption and excessive use of fossil fuels promote the exploration of new energy conversion technologies. Meanwhile, the increase in the supply of ethane encourages the development of industrial technology for the production of ethylene chemical raw materials. Compared with traditional fossil fuel energy conversion equipment, solid oxide ethane cogeneration fuel cells are an efficient energy processing device. Through selective oxidation of fuel gas on the anode, the endothermic process of ethane dehydrogenation is converted into an exothermic oxidation reaction, which has a greater driving force for reaction thermodynamics, and simultaneously produces clean electricity and value-added chemicals without CO₂ emissions. The anode material used for the proton conductor ethane fuel cells needs to operate stably and efficiently under hydrocarbon fuel. Consequently, excellent catalytic activity, low polarization resistance, and anti-coking stability are essential. In this work, CeO₂ was uniformly impregnated into the surface of the porous cubic perovskite Pr_0.4Sr_0.6Co_0.2Fe_0.7Mo_0.1O_3−δ anode by wet impregnation, and then calcined and reduced to obtain a CeO₂/RP-PSCFM@CoFe composite anode embedded with nanoparticles, which was successfully used in electrolyte-supported proton conductor fuel cells. CeO₂ has a high ionic conductivity and transport capacity, which accelerates the transfer rate of protons on the anode and improves the catalytic reaction and transport process. Moreover, uniformly dispersed CeO₂ can effectively increase the three-phase interface of the anode reaction and increase the range of reaction activity. The peak power densities before and after wet impregnation reached 172 and 253 mW·cm⁻², respectively, at 750 ℃. When switching to ethane as the fuel, the peak power densities reached 136 and 183 mW·cm⁻², respectively. The polarization resistance of the impregnated single cell was significantly reduced, and the catalytic activity improved. Moreover, there was no attenuation for 10 h in the long-term test. Inversely, the current density increased with the continuous reduction of the composite anode. Product analysis revealed that the yield of ethylene increased from 23.52% at 650 ℃ to 34.09% at 750 ℃, and the ethylene selectivity exceeded 94%. These results clearly show that the impregnated anode exhibited excellent catalytic activity and anti-coking ability in hydrocarbon fuels at high temperatures. Combining CoFe nanoparticles with CeO₂ enhanced the electronic conductance and ionic conductance of the electrode, improved the transmission of electric energy and the efficient conversion of chemicals, thus successfully producing the cogeneration of electric energy and ethylene.

S-scheme heterojunction is a major breakthrough in the field of photocatalysis. In this study, NiS₂ and MoSe₂ were prepared by a typical solvothermal method, and compounded by an in situ growth method to construct an S-scheme heterojunction. The obtained composite showed excellent performance in photocatalytic hydrogen evolution; the hydrogen production rate was approximately 7 mmol·h^-1·g^-1, which was 2.05 times and 2.44 times those of pure NiS₂ and MoSe₂, respectively. Through a series of characterizations, it was found that NiS₂ and MoSe₂ coupling can enhance the light absorption intensity, which is vital for the light reaction system. The efficiency of electron-hole pair separation is also among the important factors restricting photocatalytic reactions. Compared with pure NiS₂ and MoSe₂, NiS₂/MoSe₂ exhibited a higher photocurrent density, lower cathode current, and lower electrochemical impedance, which proves that the NiS₂/MoSe₂ complex can effectively promote photogenerated electron transfer. Simultaneously, the lower emission intensity of fluorescence indicated effective inhibition of electron-hole recombination in the NiS₂/MoSe₂ complex, which is favorable for the photocatalytic hydrogen evolution reaction. Further, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that MoSe₂ is an amorphous sample surrounded by the NiS₂ nanomicrosphere, which greatly increased the contact area between the two, thus increasing the active site of the reaction. Secondly, as a photosensitizer, Eosin Y (EY) effectively enhanced the absorption of light by the catalyst in the photoreaction system. Meanwhile, during sensitization, electrons were provided to the catalyst, which effectively improved the photocatalytic reaction efficiency. The establishment of S-scheme heterojunctions contributed to improving the redox capacity of the reaction system and was the most important link in the photocatalytic hydrogen reduction of aquatic products. It was also the main reason for the improvement of the hydrogen evolution effect in this study. The locations of the conduction band and valence band of NiS₂ and MoSe₂ were determined by Mott-Schottky plots and photon energy curves, and further proved the establishment of the S-scheme heterojunction. This work provides a new reference for studying the S-scheme heterojunction to effectively improve the photocatalytic hydrogen production efficiency.

The use of semiconductor photocatalysts (CdS, g-C₃N₄, TiO₂, etc.) to generate hydrogen (H₂) is a prospective strategy that can convert solar energy into hydrogen energy, thereby meeting future energy demands. Among the numerous photocatalysts, TiO₂ has attracted significant attention because of its suitable reduction potential and excellent chemical stability. However, the photoexcited electrons and holes of TiO₂ are easily quenched, leading to limited photocatalytic performance. Furthermore, graphene has been used as an effective electron cocatalyst in the accelerated transport of photoinduced electrons to enhance the H₂-production performance of TiO₂, owing to its excellent conductivity and high charge carrier mobility. For an efficient graphene-based photocatalyst, the rapid transfer of photogenerated electrons is extremely important along with an effectual interfacial H₂-production reaction on the graphene surface. Therefore, it is necessary to further optimize the graphene microstructures (functionalized graphene) to improve the H₂-production performance of graphene-based TiO₂ photocatalysts. The introduction of H₂-evolution active sites onto the graphene surface is an effective strategy for the functionalization of graphene. Compared with the noncovalent functionalization of graphene (such as loading Pt, MoS_x, and CoS_x on the graphene surface), its covalent functionalization can provide a strong interaction between graphene and organic molecules in the form of H₂-evolution active sites that are produced by chemical reactions. In this study, carboxyl-functionalized graphene (rGO-COOH) was successfully modified via ring-opening and esterification reactions on the TiO₂ surface by using an ultrasound-assisted self-assembly method to prepare a high-activity TiO₂/rGO-COOH photocatalyst. The Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and thermogravimetric (TG) curves revealed the successful covalent functionalization of GO to rGO-COOH by significantly enhanced ―COOH groups in FTIR and increased peak area of carboxyl groups in XPS. A series of characterizations, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), XPS, and UV-Vis adsorption spectra, were performed to demonstrate the successful synthesis of TiO₂/rGO-COOH photocatalysts. The experimental data for the hydrogen-evolution rate showed that the TiO₂/rGO-COOH displayed an extremely high hydrogen-generation activity (254.2 μmol∙h⁻¹∙g⁻¹), which was 2.06- and 4.48-fold higher than those of TiO₂/GO and TiO₂, respectively. The enhanced photocatalytic activity of TiO₂/rGO-COOH is ascribed to the carboxyl groups of carboxyl-functionalized graphene, which act as effective hydrogen-generation active sites and enrich hydrogen ions owing to their excellent nucleophilicity that facilitates the interfacial hydrogen production reaction of TiO₂. This study provides novel insights into the development of high-activity graphene-supported photocatalysts in the hydrogen-generation field.

The growing frustration from facing energy shortages and unbalanced environmental issues has obstructed the long-term development of human society. Semiconductor-based photocatalysis, such as water splitting, transfers solar energy to storable chemical energy and is widely considered an economic and clean solution. Although regarded as a promising photocatalyst, the low specific surface area of g-C₃N₄ crucially restrains its photocatalytic performance. The macro-mesoporous architecture provides effective channels for mass transfer and full-light utilization and improved the efficiency of the photocatalytic reaction. Herein, g-C₃N₄ with an inverse opal (IO) structure was rationally fabricated using a well-packed SiO₂ template, which displayed an ultrahigh surface area (450.2 m²·g^-1) and exhibited a higher photocatalytic H₂ evolution rate (21.22 μmol·h^-1), almost six times higher than that of bulk g-C₃N₄ (3.65 μmol·h^-1). The IO g-C₃N₄ demonstrates better light absorption capacity than bulk g-C₃N₄, primarily in the visible spectra range, owing to the multiple light scattering effect of the three-dimensional (3D) porous structure. Meanwhile, a lower PL intensity, longer emission lifetime, smaller Nyquist semicircle, and stronger photocurrent response (which synergistically give rise to the suppressed recombination of charge carriers) decrease the interfacial charge transfer resistance and boost the formation of photogenerated electron-hole pairs. Moreover, the existing N vacancies intensify the local electron density, helping increase the number of photoexcitons. The N₂ adsorption-desorption test revealed the existence of ample mesopores and macropores and high specific surface area in IO g-C₃N₄, which exposes more active edges and catalytic sites. Optical behavior, electron paramagnetic resonance, and electrochemical characterization results revealed positive factors, including enhanced light utilization, improved photogenerated charge separation, prolonged lifetime, and fortified IO g-C₃N₄ with excellent photocatalytic performance. This work provides an important contribution to the structural design and property modulation of photocatalysts.

The threat and global concern of energy crises have significantly increased over the last two decades. Because solar light and water are abundant on earth, photocatalytic hydrogen evolution through water splitting has been considered as a promising route to produce green energy. Therefore, semiconductor photocatalysts play a key role in transforming sunlight and water to hydrogen energy. To date, various photocatalysts have been studied. Among them, TiO₂ has been extensively investigated because of its non-toxicity, high chemical stability, controllable morphology, and high photocatalytic activity. In particular, 1D TiO₂ nanofibers (NFs) have attracted increasing attention as effective photocatalysts because of their unique 1D electron transfer pathway, high adsorption capacity, and high photoinduced electron–hole pair transfer capability. However, TiO₂ NFs are considered as an inefficient photocatalyst for the hydrogen evolution reaction (HER) because of their disadvantages such as a large band gap (~3.2 eV) and fast recombination of photoinduced electron–hole pairs. Therefore, the development of a high-performance TiO₂ NF photocatalyst is required for efficient solar light conversion. In recent years, several strategies have been explored to improve the photocatalytic activity of TiO₂ NFs, including coupling with narrow-bandgap semiconductors (such as ZnIn₂S₄). Recently, microwave (MW)-assisted synthesis has been considered as an important strategy for the preparation of photocatalyst semiconductors because of its low cost, environment-friendliness, simplicity, and high reaction rate. Herein, to overcome the above-mentioned limiting properties of TiO₂ NFs, we report a 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction synthesized through a microwave (MW)-assisted process. Herein, the 2D/1D ZnIn₂S₄/TiO₂ S-scheme heterojunction was constructed rapidly by using in situ 2D ZnIn₂S₄nanosheets decorated on 1D TiO₂ NFs. The loading of ZnIn₂S₄ nanoplates on the TiO₂ NFs could be easily controlled by adjusting the molar ratios of ZnIn₂S₄ precursors to TiO₂ NFs. The photocatalytic activity of the as-prepared samples for water splitting under simulated solar light irradiation was assessed. The experimental results showed that the photocatalytic performance of the ZnIn₂S₄/TiO₂ composites was significantly improved, and the obtained ZnIn₂S₄/TiO₂ composites showed increased optical absorption. Under optimal conditions, the highest HER rate of the ZT-0.5 (molar ratio of ZnIn₂S₄/TiO₂= 0.5) sample was 8774 μmol·g^-1·h^-1, which is considerably higher than those of pure TiO₂ NFs (3312 μmol·g^-1·h^-1) and ZnIn₂S₄nanoplates (3114 μmol·g^-1·h^-1) by factors of 2.7 and 2.8, respectively. Based on the experimental data and Mott-Schottky analysis, a possible mechanism for the formation of the S-scheme heterojunction between ZnIn₂S₄ and TiO₂ was proposed to interpret the enhanced HER activity of the ZnIn₂S₄/TiO₂heterojunctionphotocatalysts.

Photocatalytic reduction of CO₂ to hydrocarbon compounds is a promising method for addressing energy shortages and environmental pollution. Considerable efforts have been devoted to exploring valid strategies to enhance photocatalytic efficiency. Among various modification methods, the hybridization of different photocatalysts is effective for addressing the shortcomings of a single photocatalyst and enhancing its CO₂ reduction performance. In addition, metal-free materials such as g-C₃N₄ and black phosphorus (BP) are attractive because of their unique structures and electronic properties. Many experimental results have verified the superior photocatalytic activity of a BP/g-C₃N₄ composite. However, theoretical understanding of the intrinsic mechanism of the activity enhancement is still lacking. Herein, the geometric structures, optical absorption, electronic properties, and CO₂ reduction reaction processes of 2D/2D BP/g-C₃N₄ composite models are investigated using density functional theory calculations. The composite model consists of a monolayer of BP and a tri-s-triazine-based monolayer of g-C₃N₄. Based on the calculated work function, it is inferred that electrons transfer from g-C₃N₄ to BP owing to the higher Fermi level of g-C₃N₄ compared with that of BP. Furthermore, the charge density difference suggests the formation of a built-in electric field at the interface, which is conducive to the separation of photogenerated electron-hole pairs. The optical absorption coefficient demonstrates that the light absorption of the composite is significantly higher than that of its single-component counterpart. Integrated analysis of the band edge potential and interfacial electronic interaction indicates that the migration of photogenerated charge carriers in the BP/g-C₃N₄ hybrid follows the S-scheme photocatalytic mechanism. Under visible-light irradiation, the photogenerated electrons on BP recombine with the photogenerated holes on g-C₃N₄, leaving photogenerated electrons and holes in the conduction band of g-C₃N₄ and the valence band of BP, respectively. Compared with pristine g-C₃N₄, this S-scheme heterojunction allows efficient separation of photogenerated charge carriers while effectively preserving strong redox abilities. Additionally, the possible reaction path for CO₂ reduction on g-C₃N₄ and BP/g-C₃N₄ is discussed by computing the free energy of each step. It was found that CO₂ reduction on the composite occurs most readily on the g-C₃N₄ side. The reaction path on the composite is different from that on g-C₃N₄. The heterojunction reduces the maximum energy barrier for CO₂ reduction from 1.48 to 1.22 eV, following the optimal reaction path. Consequently, the BP/g-C₃N₄ heterojunction is theoretically proven to be an excellent CO₂ reduction photocatalyst. This work is helpful for understanding the effect of BP modification on the photocatalytic activity of g-C₃N₄. It also provides a theoretical basis for the design of other high-performance CO₂ reduction photocatalysts.

Organic photocatalysts have attracted attention owing to their suitable redox band positions, low cost, high chemical stability, and good tunability of their framework and electronic structure. As a novel organic photocatalyst, PDI-Ala (N, N'-bis(propionic acid)-perylene-3, 4, 9, 10-tetracarboxylic diimide) has strong visible-light response, low valence band position, and strong oxidation ability. However, the low photogenerated charge transfer rate and high carrier recombination rate limit its application. Due to the aromatic heterocyclic structure of g-C₃N₄ and large delocalized π bond in the planar structure of PDI-Ala, g-C₃N₄ and PDI-Ala can be tightly combined through π–π interactions and N―C bond. The band structure of sulfur-doped g-C₃N₄ (S-C₃N₄) matched well with PDI-Ala than that with g-C₃N₄. The electron delocalization effect, internal electric field, and newly formed chemical bond jointly promote the separation and migration of photogenerated carriers between PDI-Ala and S-C₃N₄. To this end, a novel step-scheme (S-scheme) heterojunction photocatalyst comprising organic semiconductor PDI-Ala and S-C₃N₄ was prepared by an in situ self-assembly strategy. Meanwhile, PDI-Ala was self-assembled by transverse hydrogen bonding and longitudinal π–π stacking. The crystal structure, morphology, valency, optical properties, stability, and energy band structure of the PDI-Ala/S-C₃N₄ photocatalysts were systematically analyzed and studied by various characterization methods such as X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, ultraviolet visible diffuse reflectance spectroscopy, electrochemical impedance spectroscopy, and Mott-Schottky curve. The work functions and interface coupling characteristics were determined using density functional theory. The photocatalytic activities of the synthesized photocatalyst for H₂O₂ production and the degradation of tetracycline (TC) and p-nitrophenol (PNP) under visible-light irradiation are discussed. The PDI-Ala/S-C₃N₄ S-scheme heterojunction with band matching and tight interface bonding accelerates the intermolecular electron transfer and broadens the visible-light response range of the heterojunction. In addition, in the processes of the PDI-Ala/S-C₃N₄ photocatalytic degradation reaction, a variety of active species (h⁺, ·O₂^-, and H₂O₂) were produced and accumulated. Therefore, the PDI-Ala/S-C₃N₄ heterojunction exhibited enhanced photocatalytic performance in the degradation of TC, PNP, and H₂O₂ production. Under visible-light irradiation, the optimum 30%PDI-Ala/S-C₃N₄ removed 90% of TC within 90 min. In addition, 30%PDI-Ala/S-C₃N₄ displayed the highest H₂O₂ evolution rate of 28.3 μmol·h^-1·g^-1, which was 2.9 and 1.6 times higher than those of PDI-Ala and S-C₃N₄, respectively. These results reveal that the all organic photocatalyst comprising PDI-based supramolecular and S-C₃N₄ can be efficiently applied for the degradation of organic pollutants and production of H₂O₂. This work not only provides a novel strategy for the design of all organic S-scheme heterojunctions but also provides a new insight and reference for understanding the structure–activity relationship of heterostructure catalysts with effective interface bonding.

Sustainable photocatalytic H₂ evolution has attracted extensive attention in recent years because it can address both energy shortage and environmental pollution issues. In particular, metal sulfide solid-solution photocatalysts have been widely applied in photocatalytic hydrogen generation owing to their excellent light harvesting properties, narrow enough band gap, and suitable redox potentials of conduction and valance bands. However, it is still challenging to develop low-cost and high-efficiency sulfide solid-solution photocatalysts for practical photocatalytic hydrogen evolution. Recently, 1D Mn_xCd_1-xS nanostructures have shown superior light absorption, charge separation, and H₂-evolution activity owing to their shortened diffusion pathway of carriers and high length-to-diameter ratios. Thus, 1D Mn_xCd_1-xS nanostructures have been applied in photocatalytic H₂ evolution. However, a single Mn_xCd_1-xS photocatalyst still has some disadvantages for photocatalytic H₂ evolution, such as the rapid recombination of photogenerated electron-hole pairs and low quantum efficiency. Herein, to further boost the separation of photogenerated charge carriers and H₂-evolution kinetics, an in situ solvothermal method was used to synthesize the 1D/2D Schottky-based heterojunctions between the Mn_0.2Cd_0.8S nanorods (MCS NRs) and Ti₃C₂ MXene nanosheets (NSs). Furthermore, various characterization methods have been used to investigate the crucial roles and underlying mechanisms of metallic Ti₃C₂ MXene NSs in boosting the photocatalytic H₂ evolution over the Mn_0.2Cd_0.8S nanorods. X-ray Diffraction (XRD), Transmission Electron Microscope (TEM), High Resolution Transmission Electron Microscopy (HRTEM), element mapping images, and X-ray Photoelectron Spectroscopy (XPS) results clearly demonstrate that hybrid low-cost Schottky-based heterojunctions have been successfully constructed for practical applications in photocatalytic H₂ evolution. Additionally, the photocatalytic hydrogen evolution reaction (HER) was also carried out in a mixed solution of Na₂SO₃ and Na₂S using as the sacrificial agents. The highest hydrogen evolution rate of the optimized 1D/2D Schottky-based heterojunction is 15.73 mmol·g^-1·h^-1, which is 6.72 times higher than that of pure MCS NRs (2.34 mmol·g^-1·h^-1). An apparent quantum efficiency of 19.6% was achieved at 420 nm. The stability measurements of the binary photocatalysts confirmed their excellent photocatalytic stability for practical applications. More interestingly, the UV-Vis diffuse reflection spectra, photoluminescence (PL) spectrum, transient photocurrent responses, and Electrochemical Impedance Spectroscopy (EIS) Nyquist plots clearly confirmed the promoted charge separation between the MCS NRs and Ti₃C₂ MXene NSs. The linear sweep voltammetry also showed that the loading of MXene cocatalysts could greatly decrease the overpotential of pure MCS NRs, suggesting that the 2D Ti₃C₂ NSs could act as an electronic conductive bridge to improve the H₂-evolution kinetics. In summary, these results show that the 2D/1D hybrid Schottky-based heterojunctions between metallic Ti₃C₂ MXene NSs and MCS NRs can not only improve the separation of photogenerated electrons and holes but also decrease the H₂-evolution overpotential, thus resulting in significantly enhanced photocatalytic H₂ generation. We believe that this study will inspire new ideas for constructing low-cost Schottky-based heterojunctions for practical applications in photocatalytic H₂ evolution.

In environment remediation, photocatalytic oxidation is a promising technique for removing organic pollutants. Compared to adsorption, biodegradation, and chemical oxidation, photocatalytic oxidation can eliminate organic pollutants completely, conveniently, and cheaply in an environmentally friendly manner. Visible-light-driven photocatalytic oxidation is particularly advisable because of the high proportion of visible light energy in solar energy. Bismuth oxyiodide (BiOI) is a promising visible-light-driven photocatalyst for the oxidization of pollutants, not only because of its narrow band gap, but also for its relatively low valence band (VB), which is adequate for photogenerated holes to oxidize a variety of organic compounds. However, the shortcomings of BiOI powder, such the difficulty of recycling it, its low surface area, and fast carrier recombination, limit its practical applications. Meanwhile, the flexibility and hierarchical structure of photocatalysts are particularly advisable because these properties are beneficial for the convenient operation, recycling, and performance improvement of these materials. Herein, based on an electro-spun polyacrylonitrile (PAN) nanofiber substrate, a hierarchical BiOI/PAN fiber was prepared through an in situ reaction. In the as-prepared BiOI/PAN fibers, BiOI flakes were aligned vertically and uniformly around the PAN fibers. BiOI nuclei generated from pre-introduced Bi(Ⅲ) in the PAN fiber act as seeds for the growth of BiOI nanoplates, which is crucial for the formation of a hierarchical structure. Such a hierarchical structure can improve both the light absorption and carrier generation of the BiOI/PAN fibers, as demonstrated by UV-Vis diffuse reflectance spectra and photoluminescence emission. Therefore, the BiOI/PAN fibers exhibited higher photocatalytic activity than BiOI powder. When the BiOI/PAN fibers were decorated with pre-prepared graphene quantum dots (GQDs), a GQD-modified BiOI/PAN fibrous composite (GQD-BiOI/PAN) was fabricated. The morphology of the obtained GQD-BiOI/PAN fibers was nearly the same as that of the BiOI/PAN fibers. A step-scheme (S-scheme) heterojunction was formed between the GQDs and BiOI, which was confirmed by the fabrication method, photoluminescence emission, reactive radical tests, and XPS analysis. This kind of S-scheme heterojunction can not only effectively suppress the recombination of photogenerated holes, but can also reserve the more reductive electrons on the lowest unoccupied molecular orbital of GQDs and the more oxidative holes on the VB of BiOI, for the photocatalytic degradation of phenol. Because of the fibrous hierarchical structure and S-scheme heterojunction, GQD-BiOI/PAN outperformed BiOI nanoparticles and BiOI/PAN nanofibers in the photocatalytic oxidation of phenol under visible light. In addition, because of tight bonding, GQD-BiOI/PAN can be tailored and operated by hand, which is convenient for recycling. During recycling, no obvious loss of sample or decrease in photocatalytic activity was observed. This work provides a new pathway for the fabrication of flexible photocatalysts and a new insight into the enhancement of photocatalysts.

Cu/ZrO₂ catalysts have demonstrated effective in hydrogenation of CO₂ to methanol, during which the Cu-ZrO₂ interface plays a key role. Thus, maximizing the number of Cu-ZrO₂ interface active sites is an effective strategy to develop ideal catalysts. This can be achieved by controlling the active metal size and employing porous supports. Metal-organic frameworks (MOFs) are valid candidates because of their rich, open-framework structures and tunable compositions. UiO-66 is a rigid metal-organic skeleton material with excellent hydrothermal and chemical stability that comprises Zr as the metal center and terephthalic acid (H₂BDC) as the organic ligand. Herein, porous UiO-66 was chosen as the ZrO₂ precursor, which can confine Cu nanoparticles within its pores/defects. As a result, we constructed a Cu-ZrO₂ nanocomposite catalyst with high activity for CO₂ hydrogenation to methanol. Many active interfaces could form when the catalysts were calcined at a moderate temperature, and the active interface was optimized by adjusting the calcination temperature and active metal size. Furthermore, the Cu-ZrO₂ interface remained after CO₂ hydrogenation to methanol, as confirmed by transmission electron microscopy (TEM), demonstrating the stability of the active interface. The catalyst structure and hydrogenation activity were influenced by the content of the active component and the calcination temperature; therefore, these parameters were explored to obtain an optimized catalyst. At 280 ℃ and 4.5 MPa, the optimized CZ-0.5-400 catalyst gave the highest methanol turnover frequency (TOF) of 13.4 h^-1 with a methanol space-time yield (STY) of 587.8 g·kg^-1·h^-1 (calculated per kilogram of catalyst, the same below), a CO₂ conversion of 12.6%, and a methanol selectivity of 62.4%. In situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) of CO adsorption over the optimized catalyst revealed a predominant, unreducible Cu⁺ species that was also identified by X-ray photoelectron spectroscopy (XPS). The favorable activity observed was due to this abundant Cu⁺ species coming from the Cu⁺-ZrO₂ interface that served as the methanol synthesis active center and acted as a bridge for transporting hydrogen from the active Cu species to ZrO₂. In addition, the oxygen vacancies of ZrO₂ promoted the adsorption and activation of CO₂. These vacancies and Cu⁺ trapped in the ZrO₂ lattice are the active sites for methanol synthesis from CO₂ hydrogenation. The X-ray diffraction (XRD) patterns of the catalyst before and after reaction revealed the stability of its structure, which was further verified by time-on-stream (TOS) tests. Furthermore, in situ DRIFTS and temperature-programmed surface reaction-mass spectroscopy (TPSR-MS) revealed the reaction mechanism of CO₂ hydrogenation to methanol, which followed an HCOO-intermediated pathway.

Establishing a reliable method to predict the global mean temperature (T_e) is of great importance because CO₂ reduction activities require political and global cooperation and significant financial resources. The current climate models all seem to predict that the earth's temperature will continue to increase, mainly based on the assumption that CO₂ emissions cannot be lowered significantly in the foreseeable future. Given the earth's multifactor climate system, attributing atmospheric CO₂ as the only cause for the observed temperature anomaly is most likely an oversimplification; the presence of water (H₂O) in the atmosphere should at least be considered. As such, T_e is determined by atmospheric water content controlled by solar activity, along with anthropogenic CO₂ activities. It is possible that the anthropogenic CO₂ activities can be reduced in the future. Based on temperature measurements and thermodynamic data, a new model for predicting T_e has been developed. Using this model, past, current, and future CO₂ and H₂O data can be analyzed and the associated T_e calculated. This new, esoteric approach is more accurate than various other models, but has not been reported in the open literature. According to this model, by 2050, T_e may increase to 15.5 ℃ under "business-as-usual" emissions. By applying a reasonable green technology activity scenario, T_e may be reduced to approximately 14.2 ℃. To achieve CO₂ reductions, the scenario described herein predicts a CO₂ reduction potential of 513 gigatons in 30 years. This proposed scenario includes various CO₂ reduction activities, carbon capturing technology, mineralization, and bio-char production; the most important CO₂ reductions by 2050 are expected to be achieved mainly in the electricity, agriculture, and transportation sectors. Other more aggressive and plausible drawdown scenarios have been analyzed as well, yielding CO₂ reduction potentials of 1051 and 1747 gigatons, respectively, in 30 years, but they may reduce global food production. It is emphasized that the causes and predictions of the global warming trend should be regarded as open scientific questions because several details concerning the physical processes associated with global warming remain uncertain. For example, the role of solar activities coupled with Milankovitch cycles are not yet fully understood. In addition, other factors, such as ocean CO₂ uptake and volcanic activity, may not be negligible.