Pt-based electrocatalysts have received extensive attention owing to their wide applications in various fields, including fuel cells, hydrogen production, degradation of organic pollutants, electrochemical sensors, and oxidation of small molecules. Therefore, the efficient synthesis and screening of high-performance Pt-based electrocatalysts is necessary for accelerating their further development and application in these fields. The conventional method for developing the advanced materials and optimizing their synthesis parameters is time-consuming, inefficient, and costly. Microfluidic high-throughput techniques have the great potential for optimizing the synthesis parameters of Pt-based electrocatalysts. However, microfluidic high-throughput synthesis without performance evaluation cannot maximize its advantages. Therefore, it is highly desirable to develop a platform that combines the high-throughput synthesis of materials and the evaluation of their properties in a high-throughput fashion to improve the overall screening efficiency of the novel materials. In this study, a versatile microfluidic high-throughput platform, combining the high-throughput synthesis and screening of materials, was constructed. The microfluidic chip generated 20-level concentration gradients of the three different precursors. Microreactor arrays with 100 microchannels were used for the material synthesis and electrochemical characterization. A wide range of concentration combinations of the three different precursor solutions was achieved using the microfluidic chip. Five groups of Pt-based ternary electrocatalysts (100 different components in total) were synthesized and electrochemically characterized using the designed platform. The obtained Pt-based electrocatalysts exhibited a loose particle morphology, and were composed of small nanoparticles. The efficient preparation of Pt-based electrocatalysts with controllable compositions was also achieved through the high-throughput synthesis platform. The catalytic performance of the Pt-based catalysts towards oxygen evolution reaction (OER) was characterized by chronoamperometry. The optimal composition of Pt-based ternary electrocatalysts for OER was directly determined using the designed platform. For NiPtCu, the samples with a relatively high atomic percentage (approximately 50%) of Pt (i.e., Ni_0.30Pt_0.56Cu_0.14, Ni_0.17Pt_0.52Cu_0.31 and Ni_0.12Pt_0.48Cu_0.40) exhibited higher electrocatalytic activity and stability, whereas the samples with a relatively high atomic percentage (> 50%) of Cu possessed lower activity and stability. For AuPtNi and AuPtCu, the samples wherein Au and Pt accounted for a large proportion of the sample (i.e., Ni or Cu < 10%) and the atomic ratios of Au : Pt were (3–4) : 1, e.g., Au_0.71Pt_0.25Ni_0.04 and Au_0.77Pt_0.18Cu_0.05, displayed high electrocatalytic activity and stability. As the atomic fraction of Au decreased, the atomic ratio of Pt and Ni in AuPtNi approached 3 : 1 or that of Pt and Cu in AuPtCu reached to 1 : 1, the samples (Au_0.54Pt_0.35Ni_0.11, Au_0.35Pt_0.42Cu_0.23, Au_0.27Pt_0.41Cu_0.32 and Au_0.12Pt_0.32Cu_0.56) all demonstrated high electrocatalytic activity and stability. The samples (Pt_0.06Cu_0.94) wherein the atomic percentages of Au and Pt were all less than 10%, exhibited poor electrocatalytic activity and stability. For RhPtNi and RhPtCu, when the atomic percentage of Rh in RhPtNi and RhPtCu was high (50%–90%) and almost no Ni or Cu was present, the samples (Rh_0.91Pt_0.09 and Rh_0.82Pt_0.18 for RhPtNi, as well as Rh_0.88Pt_0.12 and Rh_0.75Pt_0.21Cu_0.04 for RhPtCu) all had high electrocatalytic activity and stability. As the atomic percentage of Rh decreased and that of Pt increased, the atomic percentages of Rh and Pt were relatively close, Rh_0.54Pt_0.32Ni_0.14 and Rh_0.51Pt_0.36Cu_0.14 showing high electrocatalytic activity and stability. When the atomic percentages of Ni and Cu were high (> 50%), the RhPtNi and RhPtCu samples all showed the relatively poor electrocatalytic activity and stability. These results demonstrate the high efficiency and flexibility of the constructed microfluidic high-throughput platform, which significantly shortens the cycle for the development cycle of new materials and the optimization of their properties.

Fenton-like activity of iron sulfides for the generation of reactive oxygen species and degradation of various organic pollutants has been extensively investigated due to its abundance in the natural environment. However, their Fenton-like activity is usually unsatisfactory due to the limited exposure of surface ferrous reactive sites. In this work, a new strategy to enhance the Fenton-like activity of iron sulfides, using pyrite (FeS₂) as a model, was developed based on the heat treatment of FeS₂ by water steam. It was found that the FeS₂ heat-treated by water steam (Heat-FeS₂) exhibited much higher heterogeneous Fenton activity in the degradation of alachlor (ACL) than its parent FeS₂ prepared from hydrothermal reaction (Fresh-FeS₂). At an initial pH of 6.3, the rate of degradation of ACL by Heat-FeS₂ Fenton system was 0.48 min^?1, which is ~23 times higher than that of Fresh-FeS₂ Fenton system. Electron spin resonance analysis and benzoic acid probe experiments confirmed the production of more hydroxyl (•OH) and superoxide radicals (•O₂^?) in Heat-FeS₂ Fenton system than Fresh-FeS₂ Fenton system. The increased Fenton-like activity of Heat-FeS₂ can be attributed to the increased content of highly reactive surface bonded Fe²⁺/Fe³⁺ species, higher amount of leached Fe²⁺, and optimal reaction pH due to stronger acidification of Heat-FeS₂. Characterization studies by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy showed that heat treatment remarkably promoted the transformation of lattice Fe²⁺ to surface reactive Fe²⁺, allowing the exposure of more surface reactive Fe²⁺ and leaching of Fe²⁺; simultaneously, heat treatment enhanced the generation of surface SO₄^2?, creating a highly acidic surface. The surface Fe²⁺ percentage in the surface total iron was raised from 13% in Fresh-FeS₂ to 29% in Heat-FeS₂. Fe²⁺ leaching from Heat-FeS₂ was 0.23 mmol·L^?1, much higher than that (< 0.02 mmol·L^?1) for Fresh-FeS₂. The change in the surface Fe and S species in the Heat-FeS₂ system during the Fenton-like reaction was monitored by XPS to elucidate the enhanced Fenton oxidation mechanism. The characterization results showed that after Fenton reaction with H₂O₂, the surface contents of Fe²⁺ and Fe³⁺ species on Fresh-FeS₂ and Heat-FeS₂ were remarkably raised, while the surface content of S₂^2? species was reduced, confirming the crucial role of S₂^2? in the reductive cycle of Fe³⁺ to Fe²⁺. These findings increase understanding of the oxidative transformation and corrosion of iron sulfides and its relevant transformation and degradation of toxic organics in natural environments. The results of this work also provide an efficient Fenton-like oxidation method based on iron sulfides for highly efficient degradation of organic pollutants (e.g. ACL) in aqueous solution.

Colloidal quantum dots (CQDs) are extremely promising infrared optoelectronic materials for efficient solar cells owing to their strong infrared absorption with tunable spectra. However, the liquid-state ligand exchange of CQDs using ammonium acetate (AA) as an additive generally resulted in intensive charge-transport barriers within the CQD solids. This is induced by the high-bandgap PbI₂ matrix, which considerably affects the charge-carrier extraction of CQD solar cells (CQDSCs), and thus their photovoltaic performance. Herein, dimethylammonium iodide (DMAI) was used as an additive instead for the liquid-state ligand exchange, substantially eliminating the PbI₂ matrix capping the CQDs and simultaneously restraining CQD fusion during the ligand exchange, thereby reducing the barriers for the charge-carrier transport within the CQD solids. Extensive experimental studies and theoretical calculations were performed to link the surface chemistry of the CQDs with the charge-carrier dynamics within the CQD solids and full solar cell devices. The theoretical calculation results reveal that DMAI which possess small dissociation energy could finely regulate the ligand exchange of CQDs, resulting in the suppressed energetic disorder and diminished charge-transport barriers in the CQD solids compared to those of the CQD solids prepared using AA. The DMAI-treated quantum dots were characterized and analyzed by transmission electron microscopy, X-ray photoelectron spectroscopy, and 2D grazing-incidence wide-and small-angle X-ray scattering spectrometry. The results show PbI₂-related Bragg peaks in the AA-treated CQD solid films, indicating a thick layer of PbI₂ crystal matrix being formed in the CQD solids, whereas there was no obvious PbI₂ signal observed in DMAI-treated CQD solids. These results also demonstrate that DMAI provides additional I^?, improving the surface passivation of the CQDs and reducing trap-assisted recombination. For the infrared photovoltaic applications, the CQDSC devices were fabricated, which shows that the photovoltaic performance of CQDSCs was significantly improved. The power conversion efficiency of DMAI-based CQDSCs was improved by 17.8% compared with that of the AA-based CQDSC. The charge-carrier dynamics in both CQD solids and full solar cell devices were analyzed in detail, revealing that the improved photovoltaic performance in DMAI-based CQDSCs was attributed to the facilitated charge-carrier transport within the CQD solids and suppressed trap-assisted recombination, resulting from eliminated charge-transport barriers and improved surface passivation of CQDs, respectively. This work provides a new avenue to controlling the surface chemistry of infrared CQDs and a feasible approach to substantially diminishing the charge transfer barriers of CQD solids for infrared solar cells.

MOF-derived metal selenides are promising candidates as effective anode materials in sodium-ion batteries (SIBs) owing to their ordered carbon skeleton structure and the high conductivity of selenides. They can be imparted with rapid electron/ion transport channels for the insertion/de-insertion of Na⁺. In this study, MOF-derived In₂Se₃ was prepared as an anode material for SIBs. However, the large volume expansion during cycling leads to structural collapse, which affects the charging and discharging circulation life of the battery. To address this, a two-dimensional rGO network was introduced on the MOF-derived In₂Se₃ surface by surface modification. Field-emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) results confirmed the successful synthesis of the In₂Se₃@C/rGO composite. The structures with two types of carbon enhanced the charge transfer kinetics and provided two stress-buffering layers. Thus, the volume change could be accommodated and simultaneously, electron transfer was accelerated. This technique was effective, as proved by the enhanced capacity retention of 95.2% at 1 A·g^?1 after 500 cycles. In contrast, the capacity retention of the MOF-derived material without rGO was only 74.2%. Additionally, due to the synergistic effect of the rGO network and the MOF-derived In₂Se₃, the anode showed a superior capacity of 468 mAh·g^?1 at 0.1 A·g^?1. Conversely, at the same current density, the uncoated material delivered only a capacity of 393 mAh·g^?1. To study the electrochemical process of the electrode, the In₂Se₃@C/rGO electrode was subjected to cyclic voltammetry (CV) measurements; the results showed that the In₂Se₃@C/rGO electrode had notable electrochemical reactivity. In addition, in situ X-ray diffraction (XRD) was performed to explore the sodium storage mechanism of In₂Se₃, demonstrating that In₂Se₃ had a dual Na⁺ storage mechanism involving conversion and alloying reactions, and revealing the origin of its high theoretical specific capacity. This study is expected to serve as a reference for preparing optimized rGO-based materials for use as SIB anodes.

Fuel cells are essential energy conversion devices for future renewable energy structures. Mainstream proton exchange membrane fuel cells (PEMFCs) generally exhibit satisfactory performance despite requiring noble metal catalysts to be stable in acidic environments. Alkaline polymer electrolyte fuel cells (APEFCs), in contrast, offer the benefit of employing non-noble metal catalysts in fuel cells, but their overall performance and especially their long-term stability require further improvement. A critical component within APEFCs is the membrane electrode assembly (MEA), which comprises a hydroxide ion conductive polymer membrane, a cathode, and an anode (including a catalyst layer and a gas diffusion layer). MEA is where electrochemical reactions occur; thus, it plays a crucial role in determining fuel cell performance. Herein, the fabrication of a cone-shaped array on the surface of an alkaline polymer electrolyte membrane for improving the overall device performance is presented. The cone array was prepared using a sacrificial anodic aluminum oxide (AAO) template, and the array side of the polymer electrolyte was used as the cathode to construct the MEA, denoted as A-MEA. The control sample with no cone arrays on the polymer electrolyte surface is denoted as P-MEA. The Pt loadings on both the anode and cathode sides were approximately 0.2 mg∙cm⁻². APEFCs with A-MEA and P-MEA were separately assembled and tested in an 850e Fuel Cell Test System at a cell temperature of 80 ℃. Fully humidified hydrogen and oxygen were both supplied at a flow rate of 1000 mL·min⁻¹. The back pressure for both the anode and the cathode was 0.2 MPa. As a result, the APEFC with A-MEA exhibited a higher peak power density than that of the APEFC with P-MEA (1.48 vs. 1.04 W∙cm⁻²). The enhanced electrochemical performance of the APEFC with A-MEA was ascribed to the array-structured cathode, which improved the hydrophilicity of the polymer electrolyte membrane and increased the utilization efficiency of the catalyst. The hydrophilicity of the polymer electrolyte membrane with cone arrays was confirmed using contact angle measurements. The contact angles of the membranes with and without cone arrays were ~0° and 70.8°, respectively. The hydrophilic membrane promotes the electrode reaction at the cathode side. The electrochemically active surface area (ECSA) was also measured using cyclic voltammetry (CV) between 0.08 and 1 V (vs. reversible hydrogen electrode, RHE) at a scan rate of 20 mV∙s^-1, using fully humidified H₂ and N₂. A flow rate of 1000 mL∙min⁻¹ and back pressure of 0 MPa were employed. Results revealed that the ECSA of the cathode without the array was smaller than that of the array-structured cathode (21.17 vs. 24.89 m²∙g⁻¹), indicating that the array structure improved the catalyst utilization efficiency compared to that of the control sample. This study provides an effective strategy for the structural design and optimization of the MEAs in APEFCs.

The use of high-capacity ternary cathode materials for high-energy batteries can cause thermal runaway of lithium-ion batteries (LIBs), hindering their safe use and further development. Therefore, improving the energy density of LIBs while maintaining their safety is essential. Current collectors (CCs), which serve as the electron carrier during the electrochemical process, do not contribute to capacity and are regarded as "dead weight" to the cells. The use of composite CCs, which have a sandwich structure where a thin metal (e.g., Al and Cu) layer is deposited on both sides of polymer films, can reduce the weight of CCs owing to the use of the low-density insulating substrate and improve the safety of LIBs (evaluated by the nail penetration test). However, due to the weak interfacial adhesion between the substrate and metal coating layer, the composite CCs may easily delaminate in electrolytes during high-temperature immersion, which could not meet the requirement for the long-term stability. Herein, we introduced an oxide strengthening layer between the substrate (polyethylene terephthalate, PET) and Al layer. The objective of strengthening layer is to increase the interface binding force between the metal and polymer substrate by enhancing the mechanical interlocking effect between the layers and forming a stable chemical bond at the interface. This increased interface binding force effectively improved the electrolyte compatibility of composite CCs even at a high temperature of 85 ℃. Based on the results of atomic force microscopy and X-ray photoelectron spectroscopy, we proposed a mechanism for the enhancement of both mechanical interlocking and chemical bonding. Additionally, the composite CCs possessed good mechanical properties that ensure their compatibility with conventional battery fabrication technologies. LIBs using composite CCs exhibited a comparable electrochemical performance to that of aluminum-CC-based (Al CCs) cells, but better performance in nail penetration test. After 280 cycles at 0.2 C, the cell showed high-capacity retention. Al-CC-based cells and PET-AlO_x-Al-CC based cells remain 80.55% and 80.9% capacity retention respectively, which indicates the comparable performance. This shows that the composite CCs technology is fully adapted to the existing battery manufacturing technology, and has little influence on the electrochemical performance of LIBs. Specifically, cells with PET-AlO_x-Al CCs easily passed the nail penetration test under 100% state of charge without an obvious temperature rise. Furthermore, the voltage of the punctured batteries remained at ~4 V and could still be charged and discharged. The composite CCs successfully prevented the internal short circuit and markedly improved the safety of LIBs during the nail penetration test. Our findings provide theoretical guidance and solutions for the industrialization of composite CCs.

Solar cells, which are excellent alternatives to traditional fossil fuels, can efficiently convert sunlight into electricity. The intensive development of high-performance photovoltaic materials plays an important role in environmental protection and the utilization of renewable energy. Organic–inorganic hybrid perovskite materials, with a formula of ABX₃ (A = methylammonium (MA) or formamidinium (FA); B = Pb or Sn; X = Cl, I, or Br), have exhibited remarkable commercial prospects in high-performance photovoltaic devices owing to their long carrier diffusion length, excellent light absorption properties, high charge carrier mobility, and weak exciton binding energy. Recently, perovskite solar cells, fabricated using halide perovskite materials as light-absorbing layers, have achieved remarkable results; their certified power conversion efficiency has continuously improved and reached 25.7%. However, high-performance devices are usually fabricated using spin-coating methods with active areas below 0.1 cm². Hence, long-term research goals include achieving a large-scale uniform preparation of high-quality photoactive layers. The current one-step preparation of perovskite films involves the nucleation-crystalline growth process of perovskite. Auxiliary processes, such as using an anti-solvent, are often required to increase the nucleation rate and density of the film, which is not suitable for industrial large-area preparation. Additionally, the large-area preparation of perovskite films by spin-coating will result in different film thicknesses in the center and edge regions of the film due to an uneven centrifugal force. This will cause intense carrier recombination in the thicker area of the film and weak light absorption in the thinner area, which will reduce the performance of the device. To address these problems, the development of a large-area fabrication method for high-performance perovskite light-absorbing layers is essential. In this study, a two-step sequential blade-coating strategy was developed to prepare the FA-based perovskite layer. In general, PbI₂ easily forms a dense film; therefore, formamidinium iodide (FAI) cannot deeply penetrate to completely react with PbI₂. The PbI₂ residue is therefore detrimental to charge transportation. To fabricate the desired porous PbI₂ film, tetrahydrothiophene 1-oxide (THTO) was introduced into the PbI₂ precursor solution. By forming PbI₂·THTO complexes, PbI₂ crystallization is controlled, resulting in the formation of vertically packed PbI₂ flaky crystals. These crystals provide nanochannels for easy FAI penetration. The 5 cm × 5 cm modules fabricated through this strategy achieved a high efficiency of 18.65% with excellent stability. This indicates that the two-step sequential blade-coating strategy has considerable potential for scaling up the production of perovskite solar cells.

The ever-increasing carbon dioxide (CO₂) emissions caused by excessive fossil fuel consumption induce environmental issues such as global warming. To overcome this, the electrocatalytic CO₂ reduction (ECR) under ambient conditions offers an appealing approach for converting CO₂ to value-added chemicals and realizing a closed carbon loop. Among the ECR products, ethylene (C₂H₄), an important building block for plastics and other chemicals, has attracted considerable attention owing to its compatibility with existing infrastructure and the promising substitution of industrial steam cracking. In recent years, numerous efforts have been devoted to developing highly active and selective catalysts for converting CO₂ to C₂H₄, with most studies having focused on Cu-based materials. Despite the significant advancements made to date, the development of the ECR-to-C₂H₄ process is still hindered by the lack of suitable catalysts that can effectively activate CO₂ and strengthen the surface binding of *CO and *COH species. In this study, an amorphous copper oxide (CuO_x) nanofilm that is rich in oxygen vacancies was prepared via a facile vacuum evaporation method for the efficient electrocatalytic conversion of CO₂ to C₂H₄. It was expected that the nano-scale electrode thickness would greatly accelerate charge- and mass-transfer during CO₂ electrolysis. Moreover, the introduction of oxygen vacancies favored the adsorption of CO₂ and intermediates. As a result, in a typical H-cell, the synthesized defective catalyst delivered a maximum Faradaic efficiency of 85 ± 3% at −1.3 V versus the reversible hydrogen electrode and maintained a stable C₂H₄ selectivity over 48 h in a 0.1 M potassium bicarbonate solution. Interestingly, the performance observed with the synthesized electrocatalyst in this study is comparable with that of state-of-the-art Cu-based ECR catalysts. Additional structural and chemical characterizations confirmed the robust nature of the as-prepared catalyst. Moreover, when the catalyst was utilized in a membrane electrode assembly cell, it achieved a maximum C₂H₄ partial current density of approximately 115.4 mA∙cm⁻² at a cell voltage of −1.95 V and Faradaic efficiency of 78 ± 2% at a cell voltage of −1.75 V. Furthermore, theoretical and experimental analyses revealed that oxygen defects not only favored CO₂ adsorption but also enabled strong affinities for *CO and *COH intermediates, which synergistically contributed to a high selectivity for C₂H₄ formation. We believe that our present work will motivate the exploration of amorphous Cu-based materials for achieving efficient CO₂-to-C₂H₄ electrolysis and be a guide towards fundamentally understanding the mechanism of catalytic CO₂ reduction.

Operando spectroscopic characterization is effective for examining electrocatalytic reaction mechanisms. However, most operando characterization techniques currently used are based on (quasi-)steady-state spectroscopy, which often cannot directly measure transient changes occurring on the micro-millisecond time scale. Herein, an operando electrochemical UV-Vis absorption spectroscopy with 3 μs time resolution was realized by introducing bias pulses and synchronizing the bias pulse and spectral signals. Comparing the time-dependence curves of the bias pulse, collected spectral curve, and controlling voltage, a good time consistence for the three signals was observed, demonstrating the time-resolved ability of the novel apparatus. More importantly, two oxidation reactions, water oxidation reaction and hole sacrifice reagent oxidation reaction, showed distinct dynamics, verifying the reliability of the time-resolved kinetics. The water oxidation kinetics on a ferrihydrite (Fh) electrocatalyst were studied by this novel operando spectroscopic system. Different water oxidation steps were decoupled by analyzing the accumulation and decay dynamics of the operando time-resolved UV-Vis absorption data with various pulse widths and magnitudes of applied bias. A long bias pulse with width above 1s enabled the continuous accumulation of reaction intermediates in Fh electrocatalyst to reach a quasi-equilibrium state with electron extraction into the external circuit. In addition, a fast decay for water oxidation was observed after the applied bias was turned off. Importantly, when a short bias pulse with tens of ms width was applied, an abnormal intermediate accumulation process was observed after the applied bias was shut off, revealing a spontaneous species transformation process. These results confirm the validity of this novel method for examining species transformation kinetics at a fast timescale. The formation, transformation, and reaction kinetics of water oxidation reaction intermediates were directly studied on a µs to s time scale. Therefore, operando electrochemical UV-Vis absorption spectroscopy with µs time resolution can promote the understanding of various electrocatalytic reaction mechanisms and be used to guide the design and synthesis of novel high-efficiency electrocatalysts.

High-energy rechargeable lithium metal batteries (LMBs) have attracted significant attention recently. These batteries can be bulit using high areal-capacity (> 4 mAh∙cm⁻²) layered oxide cathodes and thin lithium (Li) metal anodes (< 50 μm in thickness), whose cycle performance are severely limited by the unregulated growth of Li particles having high surface areas, including dendrites and mossy Li. To improve the cycle performance of LMBs, many approaches have been developed in recent years to promote dendrite-free and dense Li electrodeposition, such as electrolyte engineering (for liquid cells), Li anode surface modification, three-dimensional current collector design, and using solid-state electrolytes. In addition to these heavily researched chemical-based approaches, applying external pressure to LMBs can also strongly impact the morphology of the electrochemically deposited Li particles due to the malleable nature of metallic Li and has been shown to improve the cycle performance. However, the relationship between the applied pressure, morphological evolution of the Li anode and the cycle performance has not been fully understood, especially in coin cells, which are widely used for LMB research. Here we report a custom-designed pressure applying/measurement device based on thin-film pressure sensors to realize real-time tracking of the pressure evolution in LMB coin cells. Our results show that moderate pressure is conducive to dense Li deposition and increases the cycle life, whereas excessive pressure causes Li inward-growth and the deformation of Li anode, which will impare the electrochemical performance of LMBs. Although these observations are made in coin cells, they could have important implications for pouch cells and solid-state batteries, both of which are commonly tested under pressure. The cycle performance of LMBs is significantly improved in both coin cells (under actual relevant conditions) and large pouch cells. A 5 Ah pouch-type LMB with a high energy density exceeding 380 Wh∙kg⁻¹ could achieve stable cycling over 50 cycles under a stack pressure of ~1.2 MPa. It was also confirmed that the cell holders or clamps commonly used for coin cells can only exert a small amount of pressure, which is unlikely to exaggerate the cycle performance of the LMB coin cells. However, we do suggest that the electrochemical performance of LMBs should be reported along with the information on the applied pressure. This research practice will improve the consistency and quality of the reported data in the LMB research community and help unite the efforts to further improve the high energy density LMBs.

In this study, new lanthanide complexes were synthesized via the volatilization method in solution at room temperature. The general molecular formulas for the lanthanide complexes are as follows: [Ln(2, 4-DFBA)₃(phen)]₂ (Ln = Sm 1, Eu 2, and Er 3; 2, 4-DFBA = 2, 4-difluorobenzoate; and phen = 1, 10-phenanthroline), as well as [Ln(2-Cl-6-FBA)₂(terpy)(NO₃)(H₂O)]₂ (Ln = Tb 4 and Dy 5; 2-Cl-6-FBA = 2-chloro-6-fluorobenzoate; and terpy = 2, 2': 6'2''-tripyridine). Based on single-crystal X-ray analysis, the five complexes exhibited a monoclinic crystal structure belonging to the space group P2₁/n. Even though complexes 1, 2 (I), and 3 (II) share a general molecular formula, their coordination modes were different. For example, complexes 1 and 2 formed a muffin-like structure with nine coordinated atoms, while complex 3 formed a double hat triangular geometry with eight coordinated atoms. The two-dimensional (2D) polyhedral structures of complexes 1 and 2 were formed via weak π-π stacking interactions, whereas complex 3 exhibited a 2D faceted supramolecular structure through C―H∙∙∙F hydrogen bonds. Complexes 4 and 5 were isostructural, with the presence of nitrate ions in their structure. This occurred through the C―H∙∙∙F hydrogen bonds and π-π stacking of the molecules to form a faceted supramolecular crystal structure. A series of characterizations, such as elemental analysis, infrared and Raman spectroscopy, as well as powder X-ray diffraction, were performed on the five complexes. Thermogravimetry-derivative thermogravimetry-differential scanning calorimetry were performed between 299.25 and 1073.15 K to investigate the mechanism for the thermal decomposition of complexes 1–5. The analysis of the escaping gas stacking maps of the five complexes using thermogravimetric and 3D infrared coupling techniques further confirmed the correctness of the thermal decomposition mechanism of each complex. The results obtained revealed that similar structured complexes follow a similar thermal decomposition mechanism, and the end solid products for all complexes were their corresponding metal oxides. During the irradiation of the Xe lamp, the solid fluorescence of complexes 1, 2, 4, and 5 were measured. The characteristic transition peaks were located at ⁴G_5/2 → ⁶H_5/2, ⁴G_5/2 → ⁶H_7/2, and ⁴G_5/2 → ⁶H_9/2 (1); ⁵D₀ → ⁷F₀, ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂, ⁵D₀ → ⁷F₃, and ⁵D₀ → ⁷F₄ (2); ⁵D₄ → ⁷F₆, ⁵D₄ → ⁷F₅, ⁵D₄ → ⁷F₄, and ⁵D₄ →⁷F₃ (4); and ⁴F_9/2 → ⁶H_15/2, ⁴F_9/2 → ⁶H_13/2 (5). The peaks observed indicated the characteristic transitions of Ln(III). The lanthanide complexes exhibited characteristic fluorescence due to this fact, which also explained their characteristic color. Furthermore, the fluorescence lifetimes of complexes 2 and 4 were measured, and their fluorescence decay curves indicated fluorescence lifetimes of 1.288 and 0.648 ms, respectively.

Understanding the origin of the active site activity in the oxygen evolution reaction (OER) electrocatalysts is key for developing efficient electrocatalysts. However, crucial challenges remain due to the complexity of catalyst structure-activity relationships. Herein, various Co-N-C configurations, including single atoms, diatoms, and clusters, were designed to establish structure-activity relationships by first-principles calculations. It was revealed that the Co-N₄ exhibited the best reactivity due to the high coordination number of the metal center and moderate adsorption energies for all reaction intermediates. The diatom and cluster activities originate from the highly coordinated structures formed with reaction intermediates, which serve as coordination ligands. Furthermore, other factors influencing the OER activity based on the Co-N₄ configuration are discussed. For example, the weak metal-metal interaction can further optimize the adsorption of oxygen-containing intermediates by tuning antibonding energy levels of Co-O. Subsequently, an ultralow overpotential of 0.23 V for the OER in CoNi-type4 systems can be obtained by extrapolation of the volcano plot derived from the established structure-adsorption-activity relationships. This work uncovers the underlying OER activity mechanisms of Co-N-C catalysts, which helps to further understanding of high-performance of M-N-C base catalysts and will aid in the future design of high-efficiency OER catalysts.

Luminescent materials have attracted considerable attention because of their extensive applications, for example, in lighting, display, and imaging. As one of the emerging luminescent materials, perovskites have been widely studied and reported. Among them, Pb-based perovskites have shown great promise as their photoluminescence quantum yield (PLQY) is almost 100%. However, the high chemical toxicity and low stability of Pb-based perovskites increase their production costs and limit their practical applications. Sn-based perovskites are also widely studied and their PLQY can reach approximately 90%; however, Sn²⁺ easily oxidizes to Sn⁴⁺ especially upon air exposure. When compared with Pb- and Sn-based perovskites, Sb-based perovskites have the advantages of low chemical toxicity and high thermal stability. Furthermore, the optical properties of Sb-based perovskites have been improved in recent years and are expected to surpass those of Pb- and Sn-based perovskites. Herein, we report a novel series of (4-HBA)SbX₅∙H₂O single crystals (where 4-HBA is short for 4-hydroxybenzylamine, and X is Cl or Br). High quality single crystals of (4-HBA)SbBr₅∙H₂O, (4-HBA)SbBr₃Cl₂∙H₂O, and (4-HBA)SbCl₅∙H₂O with Sb⁵⁺ can be prepared via the solvothermal method. The abovementioned three materials belong to the P-1 space group. The halide and hydroxyl ions surrounded by Sb⁵⁺ ions in 4-hydroxybenzylamine formed distorted octahedral structures. Based on the results of steady-state fluorescence spectroscopy, excitation spectroscopy, transient fluorescence spectroscopy, fluorescence lifetime imaging, and density functional theory, it was found that the (4-HBA)SbBr₅∙H₂O single crystal has a direct band gap, whereas the single crystals of (4-HBA)SbBr₃Cl₂∙H₂O and (4-HBA)SbCl₅∙H₂O have an indirect band gap. When the concentration of Cl⁻ in (4-HBA)SbX₅∙H₂O increased, the band gap increased from 2.99 to 3.58 eV and the photoluminescence wavelength decreased from 618 to 595 nm. The obtained results also showed that the emission of the (4-HBA)SbX₅∙H₂O single crystal originated from the self-trapping exciton effect. With the introduction of Cl⁻, the size of the [SbX₅O]²⁻ octahedron decreased, the exciton shielding reduced, and the exciton absorption was enhanced. Additionally, after replacing Br⁻ with Cl⁻, the radiation recombination process of the excited electrons from the Sb⁵⁺ ions surrounding the halide ions gradually replaced the electron recombination of the hydroxyl ions, which extended the fluorescence lifetime from 12 to 22 ns and improved the PLQY by a factor of approximately 40.

Compared to traditional sensor device arrays, optical fiber systems capable of wide-range detection are gradually emerging as strong candidates for distributed monitoring owing to their simplified structure. However, the working mechanism of optical fiber sensors limits their use to the detection of physical parameters such as refractive index and is an obstacle for the detection of small doses of molecules by optical fiber systems. Several researchers have focused on this aspect to endow sensitivity to these optical fibers for gas or liquid molecules. By deliberately destroying the fiber structure, strong interactions between the evanescent field of optical fibers and the target materials, such as microfibers, D-shaped fiber, etc. can be achieved. Assisted by the surface plasmon resonance techniques, such configurations can exhibit highly enhanced sensitivity to a change in the refractive index caused by gas or liquid molecules. Two-dimensional materials are an excellent candidate as coating materials due to their high specific surface area, which also guarantees a large sensing response and simultaneously minimizes any side effects by suppressing the propagating mode of optical fibers. However, owing to the obstacles in optical fiber engineering and device fabrication, the abovementioned functional 2D sensors are still limited to sample-scale fabrication, and their mass-production has not yet been realized. An all-fiber distributed sensing system with high single-spot sensitivity is still difficult to fabricate. Here, we propose a new configuration of a grid-distributed environmental optical fiber sensing by introducing low-pressure chemical vapor deposition (LPCVD)-grown graphene photonic crystal fiber (PCF) into the optical fiber sensing system. We successfully synthesized monolayer and/or bilayer graphene in the air holes of PCF. By fusing the graphene PCF (Gr-PCF) to a single mode optical fiber, we fabricated an all-optical-fiber sensing system. Preliminary experiments suggest that Gr-PCF can selectively detect NO₂ gas at ppb-level and exhibit ionic sensitivity in liquids. The ability to detect NO₂ gas is attributed to the graphene layer's interaction among light-mode and adsorbed molecules: adsorption-induced additional hole-doping caused a shift in the Fermi level of graphene and eventually modulated its light absorption, leading to changes in the light intensity signals. We believe that the sensor can be extended to other kinds of gases and liquids, considering the affinity of graphene toward various molecules. In view of practical optical sensors, our design is compatible with the time domain or wavelength domain multiplexing techniques of optical fiber communication systems. Because CVD-based synthesis can be used to realize mass production, the design proposed herein shall be one of the answers to the distributed optical fiber environmental sensors.

Carbon quantum dots (CQDs) have attracted extensive interest due to their strong fluorescence as well as inexpensive and plentiful resources for manufacture. There are numerous published reports on the preparation of CQDs and direct applications based on their photoluminescence. Successive chemical modification of CQDs in an appropriate manner might expand the application scope of CQDs and transform them into practical fine chemicals. The various functional groups on the surface of CQDs allow for efficient chemical modification while imparting them with hydrophilicity. Covalent linking of hydrophobic hydrocarbon chains to CQDs would lead to the formation of novel surfactants. Here, a technique for preparing CQD-based cationic surfactants is depicted in detail. This was rare to be reported according to recent publishes. First, a mixture of ethylenediamine tetraacetic acid and ethylenediamine in the presence of hydrogen peroxide in an aqueous medium was pyrolyzed at 180 ℃ for 60 min. The resulting CQDs are represented as OX-CQDs. Then, the OX-CQDs were subjected to quaternization with 1-chlorododecane for obtaining the cationic surfactant (OX-CQDs-C₁₂H₂₅). The OX-CQDs-C₁₂H₂₅ surfactant effectively decreased the surface tension of water from 72.0 to 26.7 mN∙m⁻¹ at the critical micelle concentration of 5.0 mg∙mL⁻¹, thus demonstrating superior performance over several new Gemini cationic surfactants. The OX-CQDs-C₁₂H₂₅ surfactant also decreased the contact angles of water considerably. However, when longer alkyl chains such as －C₁₄H₂₉ or －C₁₆H₃₃ were attached to the CQDs, the corresponding surfactant was less effective in decreasing the surface tension of water. Calculations based on the Gibbs absorption isothermal equation revealed that two more －C₁₂H₂₅ chains were bonded with a carbon quantum dot averagely, implying that the as-prepared CQD-cationic surfactant belonged to the category of Gemini surfactants. Quaternization with 1-chlorododecane also led to a notable enhancement in the antibacterial activity for Escherichia coli as compared with that of unmodified CQDs. The antibacterial percentage approached 100% even the solution was diluted to 0.41 mg∙mL⁻¹, which was much lower than the critical micelle concentration. The fluorescence quantum yield of OX-CQDs-C₁₂H₂₅ reached 6.44%. Experimental results revealed that hydrogen peroxide played a positive role in improving the surface activity and fluorescence quantum yield of OX-CQDs-C₁₂H₂₅. The surface activity, antibiosis, and fluorescence endowed the versatilities of OX-CQDs-C₁₂H₂₅. This novel, economical technique for synthesizing cationic surfactants eliminates the need for introducing hydrophilic groups. The hydrothermal approach for preparing CQDs satisfies the demand for green chemical synthesis. From this aspect, our technique provides efficient access to synthesizing cationic surfactants.

Morphology regulation and the improvement of carrier separation efficiency are important strategies for the preparation of photocatalysts with excellent performance. MoS_x with a three-dimensional (3D) nanoflower morphology formed by nanosheet stacking was prepared by a simple hydrothermal method, and MoS_x/In₂O₃ with good hydrogen evolution activity was obtained by coupling with In₂O₃. The preparation of the three-dimensional nanoflower morphology combined with the construction of an S-scheme heterojunction improves the electron accumulation at the active site for hydrogen evolution reaction. The UV diffuse reflection test showed that the issue of poor light absorption of In₂O₃ was improved. The rapid separation and transfer of electrons were effectively confirmed by characterization methods such as fluorescence spectroscopy and electrochemical tests. The most intuitively manifestation of the performance improvement of the composite material is that the optimal hydrogen evolution rate reached 6704.2 μmol∙g⁻¹∙h⁻¹, which is 1.8 times that of pure MoS_x. Therefore, in this study, a new idea for the development of molybdenum-based sulfides for photocatalytic hydrogen production is provided.

Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) is considered one of the most environment friendly, economical, and efficient methods for synthesizing 2,5-furandicarboxylic acid (FDCA), which is a promising bio-based precursor of polyethylene 2,5-furandicarboxylate. In this study, we synthesized PtRuAgCoNi high-entropy alloy nanoparticles, with an average diameter of approximately 9 nm, using a solvothermal method. The synthesized nanoparticles displayed a core-shell microstructure, in which Co, Ru, Ag, and Ni were distributed over the entire core-shell microstructure of each nanoparticle, while Pt was mainly concentrated in the shell structure. A two-step method, including small-molecule substitution and low-temperature calcination, was used to remove the surfactant from the synthesized nanoparticles without changing the structure and composition of the nanoparticles. After being deposited on a carbon support, the high-entropy alloy nanoparticles, with or without surfactants, exhibited better catalytic performance in the electrocatalytic oxidation of HMF to FDCA than the commercial Pt/C catalyst. The removal of surfactants after calcination at 185 ℃ can further improve electrocatalytic performance, suggesting promising application prospects of high-entropy alloy nanoparticles in electrocatalysis and green chemistry.

The excessive and unreasonable use of synthetic bactericides in the agricultural field has caused many serious problems, including toxic effects on human health and environmental pollution. Therefore, searching for low toxicity, highly efficient, and no-residue natural bactericides is urgently needed. Plant essential oil has become an emerging and hot topic in the agricultural field because of its excellent bactericidal activity, good biocompatibility, and abundant sources. Citronella oil is a natural plant essential oil with insect repellent, insecticidal, and antibacterial activities, which mainly includes citronellal, geraniol, and citronellol. At present, the major of research on citronella oil focuses on the repellency and control of sanitary pests, but there are relatively few reports on the control of agricultural pathogenic bacteria. In addition, the hydrophobicity and volatility of citronella oil lead to its low bioavailability and hinder its full biological activity. Therefore, constructing a delivery system for improving the hydrophobicity and reducing the volatility of citronella oil is urgently needed. Nanoemulsions have the advantages of fine and uniform droplets, better physical stability, efficient permeation ability, and enhanced bioavailability. Therefore, nanoemulsions are important drug delivery systems for hydrophobic pesticides. In this study, the influences of emulsifier type (hydrophilic-lipophilic balance (HLB)), dosage, and emulsifying time on the formation and stability of citronella oil nanoemulsions were investigated by observing the appearances and microstructures of samples and measuring droplet size, thereby the optimized formula of the citronella oil nanoemulsions was determined. Furthermore, the bioactivity and biosafety of citronella oil nanoemulsions were also investigated. The results showed that nanoemulsions using castor oil polyoxyethylene ethers EL-40 (hydrophilic-lipophilic balance = 13.5) as an emulsifier had the best performance, and the stability of nanoemulsions improved as the emulsifier dosage increased from 3% to 7% (w, mass fraction). In addition, the nanoemulsion prepared through high speed shearing for 3 min was the most stable. The optimal formula for citronella oil nanoemulsions was determined to contain 5% (w) citronella oil, 6% (w) emulsifier (EL-40), and 89% (w) deionized water, upon high speed shearing for 3 min. Then, the inhibitory effect of citronella oil nanoemulsions against the growth of Pantoea ananatis was studied. The concentration for 50% of maximal effect (EC₅₀) of citronella oil nanoemulsions against Pantoea ananatis was 74.85 mg·L⁻¹. The cell viability of L02 cells treated with the citronella oil nanoemulsions (below 100 mg·L⁻¹) was above 83% after 24 h, and the apoptosis rate was 6.93%, indicating that the citronella oil nanoemulsions had low cytotoxicity. This research facilitated the design and fabrication of stable, efficient, and safe agricultural nanoemulsions, and it provides a practical solution for using plant essential oils as agricultural bactericides.

Pesticide droplet deposition on targeted plant leaf surfaces is of great importance but remains a significant challenge, especially on leaf surfaces of superhydrophobic plants. The loss of sprayed pesticide droplets leads to the overuse of pesticides and environmental pollution. Therefore, in this study, we aimed at developing a system that was capable of enhancing droplet deposition on the surfaces of superhydrophobic plant leaves via hydrogen bonding between a bio-based surfactant and glycerol at low concentration (0.25%). The system based on the sorbitol-alkylamine surfactant (denoted as SSAS-C₁₂) with a small amount of glycerol (0.001%) could efficiently inhibit droplet bouncing and splashing on different superhydrophobic/hydrophobic plant leaf surfaces. The results obtained indicated that the addition of glycerol did not change the surface tension, viscosity, contact angles on the plant leaf surfaces, and aggregate morphology of the SSAS-C₁₂ solutions. Diffusion-ordered nuclear magnetic resonance spectroscopy revealed that glycerol accelerated the diffusion of SSAS-C₁₂ molecules. More specifically, SSAS-C₁₂ molecules could diffuse and adsorb on plant leaf surfaces within a short period of time. Other surfactants (denoted as DSSAS-C₁₂ and BAPO-C₁₂) with varying numbers of hydroxyl groups were used to verify the enhancement of the deposition on superhydrophobic plant leaf surfaces caused by hydrogen bonding. It was revealed that a decrease in the number of hydroxyl groups in the surfactant molecules led to a decrease in the number of hydrogen bonds between the glycerol and surfactant molecules. Moreover, the diffusion rates of the DSSAS-C₁₂ and BAPO-C₁₂ molecules in solution were low, causing the surfactant molecules to not reach the solid-liquid interface in time. Consequently, the droplets containing surfactant molecules (of DSSAS-C₁₂ or BAPO-C₁₂) bounced and broke up on the surfaces of plant leaves. Finally, we used molecular dynamics (MD) simulations to explore the energy and molecular distribution of different surfactant-glycerol mixtures. The energy evolution of the SSAS-C₁₂-glycerol system and the distribution of surfactant molecules relative to the distance from the solid surface in the MD simulations showed that the addition of glycerol twisted the headgroup in SSAS-C₁₂ via hydrogen bonding with glycerol. In this case, SSAS-C₁₂ molecules experienced rapid diffusion and adsorption on the solid interface. Therefore, this study not only provided a constructive way to overcome the bouncing behavior of droplets but also prompted us to verify whether all hydrogen bonding interactions among different molecules could display similar control efficiencies through the rational selection of additives.

From the industrial perspective, poly(3-hexylthiophene) (P3HT) is one of the most attractive donor materials in organic photovoltaics. The large bandgap in P3HT makes it particularly promising for efficient indoor light harvesting, a unique advantage of organic photovoltaic (PV) devices, and this has started to gain considerable attention in the field of PV technology. In addition, the up-scalability and long material stability associated with the simple chemical structure make P3HT one of the most promising materials for the mass production of organic solar cells. However, the solar cells based on P3HT has a low power conversion efficiency (PCE), which is less than 11%, mainly due to significant voltage losses. In this study, we identified the origin of the high quantum efficiency and voltage losses in the P3HT: non-fullerene based solar cells, and we proposed a strategy to reduce the losses. More specifically, we observed that: 1) the non-radiative decay rate of the charge transfer (CT) states formed at the donor–acceptor interfaces was much higher for the P3HT: non-fullerene solar cells than that for the P3HT: fullerene solar cells, which was the main reason for the more severely limited photovoltage; 2) the origin of the high non-radiative decay rate in the P3HT: non-fullerene solar cell could be ascribed to the short packing distance between the P3HT and non-fullerene acceptor molecules at the donor–acceptor interfaces (DA distance), which is a rarely studied interfacial structural property, highly important in determining the decay rate of CT states; 3) the lower voltage loss in the state-of-the-art P3HT solar cell based on the 2, 2'-((12, 13-bis(2-butyldecyl)-3, 9-diundecyl-12, 13-dihydro-[1, 2, 5]-thiadiazolo[3, 4-e]thieno[2'', 3'': 4', 5']thieno[2', 3': 4, 5]p-yrolo[3, 2-g]thieno[2', 3': 4, 5]thieno[3, 2-b]indole-2, 10-diyl)bis(methanelylidene))bis(5, 6-dichloro-1H-indene-1, 3(2H)-dion-e) (ZY-4Cl) acceptor could be associated with the better alignment of the energy levels of the active materials and the longer DA distance, compared to those based on the commonly used acceptors. However, the DA distance was still very short, limiting the device voltage. Thus, improving the performance of the P3HT based solar cells requires a further increase in the DA distance. Our findings are expected to pave the way for breaking the performance bottleneck of the P3HT based solar cells.

In view of the continuously worsening environmental problems, fossil fuels will not be able to support the development of human life in the future. Hence, it is of great importance to work on the efficient utilization of cleaner energy resources. In this case, cheap, reliable, and eco-friendly grid-scale energy storage systems can play a key role in optimizing our energy usage. When compared with lithium-ion and lead-acid batteries, the excellent safety, environmental benignity, and low toxicity of aqueous Zn-based batteries make them competitive in the context of large-scale energy storage. Among the various Zn-based batteries, due to a high open-circuit voltage and excellent rate performance, Zn-Ni batteries have great potential in practical applications. Nevertheless, the intrinsic obstacles associated with the use of Zn anodes in alkaline electrolytes, such as dendrite, shape change, passivation, and corrosion, limit their commercial application. Hence, we have focused our current efforts on inhibiting the corrosion and dissolution of Zn species. Based on a previous study from our research group, the failure of the Zn-Ni battery was caused by the shape change of the Zn anode, which stemmed from the dissolution of Zn and uneven current distribution on the anode. Therefore, for the current study, we selected K₃[Fe(CN)₆] as an electrolyte additive that would help minimize the corrosion and dissolution of the Zn anode. In the alkaline electrolyte, [Fe(CN)₆]^3– was reduced to [Fe(CN)₆]^4– by the metallic Zn present in the Zn-Ni battery. Owing to its low solubility in the electrolyte, K₄[Fe(CN)₆] adhered to the active Zn anode, thereby inhibiting the aggregation and corrosion of Zn. Ultimately, the shape change of the anode was effectively eliminated, which improved the cycling life of the Zn-Ni battery by more than three times (i.e., from 124 cycles to more than 423 cycles). As for capacity retention, the Zn-Ni battery with the pristine electrolyte only exhibited 40% capacity retention after 85 cycles, while the Zn-Ni battery with the modified electrolyte (i.e., containing K₃[Fe(CN)₆]) showed 72% capacity retention. Moreover, unlike conventional organic additives that increase electrode polarization, the addition of K₃[Fe(CN)₆] not only significantly reduced the charge-transfer resistance in a simplified three-electrode system, but also improved the discharge capacity and rate performance of the Zn-Ni battery. Importantly, considering that this strategy was easy to achieve and minimized additional costs, K₃[Fe(CN)₆], as an electrolyte additive with almost no negative effect, has tremendous potential in commercial Zn-Ni batteries.

Dimethyl furan-2, 5-dicarboxylate (DMFDCA) is a valuable biomass-derived chemical that is an ideal alternative to fossil-derived terephthalic acid as a monomer for polymers. The one-step oxidation of 5-hydroxymethylfurfural (HMF) to DMFDCA is of practical significance. It not only shortens the reaction pathway but also avoids the separation process of intermediates; thus, reducing cost. In this work, non-noble bimetallic catalysts supported on N-doped porous carbon (CoMn@NC) were synthesized via a one-step co-pyrolysis procedure using different pyrolysis temperatures and proportions of metal precursors and additives. We employed the prepared CoMn@NC catalysts in the aerobic oxidation of HMF under mild reaction conditions to obtain DMFDCA. High-yield DMFDCA was obtained by screening the prepared catalysts and optimizing the reaction conditions, including the strength and amount of the base, as well as the reaction temperature. The optimized yield of DMFDCA was 85% over the Co₃Mn₂@NC-800 catalyst after 12 h at 50 ℃ using ambient-pressure oxygen. The physicochemical properties of the catalysts were determined using a variety of characterization techniques, the factors affecting the performance of each catalyst were investigated, and the relationship between the physicochemical properties and performance of the prepared catalysts was elucidated. A porous structure with a high surface area had a positive effect on mass transfer efficiency. Cobalt nanoparticles (NPs) and atomically dispersed Mn were coordinated to N-doped carbon to form M―N_x (where M = Co or Mn). Based on the Mott-Schottky effect, there was significant electron transfer between each metal and the N-doped carbon, additionally, the metal NPs supplied electrons to the carbon atoms. The electron-deficient metal site in the pyridinic N-rich carbon was beneficial for the activation of HMF and oxygen. The activation of oxygen produced reactive oxygen species (such as superoxide radical anions) to ensure high selectivity to DMFDCA through dehydrogenative oxidation of the hemiacetal intermediate and hydroxymethyl group of 5-hydroxymethyl-2-methyl-furoate. The existence of disordered and defective carbons increased the number of active sites. Subsequently, we performed a series of control experiments. Based on our current experimental results and previous studies, we propose a simple mechanism for the aerobic oxidation of HMF to DMFDCA. The catalyst was stable, its performance decreased slightly after two cycles, and it was tolerant to SCN⁻ ions and resistant against N or S poisoning. Furthermore, the use of this catalytic system can be expanded to various substituted aromatic alcohols, such as benzyl alcohols with different substituents, furfuryl alcohol, and heterocyclic alcohols. Simultaneously, the product type was further extended from methyl esters to ethyl esters with a high yield when the substrate reacted with ethanol. In conclusion, this catalytic system can be applied in the production of carboxylic esters for polymers.

Lignin is a natural aromatic polymer that accounts for nearly 30% of lignocellulose and is considered the only renewable aromatic (re)source for producing aromatic chemicals or liquid fuels via the cleavage of C―O ether bonds and C―C bonds. Thus far, the majority of investigations involving the production of valuable compounds via lignin hydrogenolysis have focused on the cleavage of relatively labile C―O bonds only, which restricts the efficiency of hydrogenolysis. Therefore, in this work, a bifunctional Pt/NbPWO catalyst was synthesized using hydrothermal and wet impregnation methods. It was found that aromatic monomers with a yield of 18.02% could be obtained by breaking the C―O and C―C bonds in alkali lignin. This reaction was applicable to breaking the key C―C bonds when the C―O ether bonds were broken in lignin polymers. The hydrogenolysis mechanism most likely involves the abundant Brønsted acid and Lewis acid sites on the catalyst that facilitate C―C bond activation. Additionally, the synergy between the support and Pt species in the Pt/NbPWO catalyst was primarily emphasized.

Because fossil fuels are continuously depleted, valorization of biomass into valuable liquid products and chemicals is of great significance yet it remains challenging. Among many biomass-derived products, lactic acid is one of the most important renewable monomers for preparing the degradable polymer polylactic acid. The use of raw biomass to produce lactic acid through catalytic conversion is an attractive approach. In this work, the catalytic reaction performance and mechanism of different Lewis acids (Y³⁺, Sc³⁺, and Al³⁺) for the production of lactic acid from cellulose were investigated in detail by isotopic nuclear magnetic resonance (NMR) and mass spectrometry. The production of lactic acid from cellulose includes tandem and competing reactions. The order of catalytic activity for the one-pot conversion of cellulose into lactic acid is as follows: Y³⁺ > Al³⁺ > Sc³⁺. The main tandem reactions involve the hydrolysis of cellulose into glucose, the isomerization of glucose into fructose (the order of catalytic activity, the same below: Y³⁺ > Al³⁺, Y³⁺ > Sc³⁺), the cleavage of fructose via a retro-aldol reaction to glyceraldehyde (GLY) and 1, 3-dihydroxyacetone (DHA) (Sc³⁺ > Y³⁺ > Al³⁺), and the conversion of DHA or GLY to the final product lactic acid (Al³⁺ > Y³⁺ > Sc³⁺). It was found that the process of glucose isomerization to fructose was the key step to the final selectivity of the tandem reaction of cellulose conversion to lactic acid, and it was clarified that the production of lactic acid from DHA underwent a keto-enol (K-E) tautomerization process rather than a classical 1, 2-shift process. First, DHA was transformed into GLY via the isomerization process, then the adjacent hydroxyl group of GLY was removed in the form of water to produce an α, β-unsaturated species. After that, the α, β-unsaturated species underwent K-E tautomerization to generate unsaturated aldehyde-ketone intermediates. Meanwhile, a molecule of water was added to aldehyde-ketone intermediates to obtain a diol product, the hydrogen atom at the methine position was transferred and the lactic acid was finally obtained through the K-E tautomerization process. The in-depth understanding of the reaction mechanism presented in this work will help to design more selective catalysts for cellulose conversion into value-added oxygen-containing small molecule chemicals.

Selective hydrogenation is a vital class of reaction. Various unsaturated functional groups in organic compounds, such as aromatic rings, alkynyl (C≡C), carbonyl (C＝O), nitro (-NO₂), and alkenyl (C＝C) groups, are typical targets in selective hydrogenation. Therefore, selectivity is a key indicator of the efficiency of a designed hydrogenation reaction. 5-(Hydroxymethyl)furfural (HMF) is an important platform compound in the context of biomass conversion, and recently, the hydrogenation of HMF to produce fuels and other valuable chemicals has received significant attention. Controlling the selectivity of HMF hydrogenation is paramount because of the different reducible functional groups (C＝O, C-OH, and C＝C) in HMF. Moreover, the exploration of new routes for hydrogenating HMF to valuable chemicals is becoming attractive. 5-Methylfurfural (MF) is also an important organic compound; thus, the selective hydrogenation of HMF to MF is an essential synthetic route. However, this reaction has challenging thermodynamic and kinetic aspects, making it difficult to realize. Herein, we propose a strategy to design a highly efficient catalytic system for selective hydrogenation by exploiting the synergy between steric hindrance and hydrogen spillover. The design and preparation of the Pt@PVP/Nb₂O₅ catalyst (PVP = polyvinyl pyrrolidone; Nb₂O₅ = niobium(V) oxide) were also conducted. Surprisingly, HMF could be converted to MF with 92% selectivity at 100% HMF conversion. The reaction pathway was revealed through the combination of control experiments and density functional theory calculations. Although PVP blocked HMF from accessing the surface of Pt, hydrogen (H₂) could be activated on the surface of Pt due to its small molecular size, and the activated H₂ could migrate to the surface of Nb₂O₅ through a phenomenon called H₂ spillover. The Lewis acidic surface of Nb₂O₅ could not adsorb the C＝O group but could adsorb and activate the C-OH group of HMF; therefore, when HMF was adsorbed on Nb₂O₅, the C-OH groups were hydrogenated by the spilled over H₂ to form MF. The high selectivity of this reaction was realized because of the unique combination of steric effects, hydrogen spillover, and tuning of the electronic states of the Pt and Nb₂O₅ surfaces. This new route for producing MF has great potential for practical application owing to its discovered advantages. We believe that this novel strategy can be used to design catalysts for other selective hydrogenation reactions. Furthermore, this study demonstrates a significant breakthrough in selective hydrogenation, which will be of interest to researchers working on the utilization of biomass, organic synthesis, catalysis, and other related fields.

Glycerol is a versatile platform compound that is formed in considerable amounts as a by-product of biodiesel production. The catalytic selective hydrogenolysis of glycerol to 1, 3-propanediol (1, 3-PDO) provides a sustainable route for the synthesis of this important diol. In this study, a series of platinum-tungsten oxide (Pt-WO_x) catalysts with different WO_x surface densities dispersed on titanium(Ⅳ) oxide, zirconium(Ⅳ) oxide, and aluminum oxide supports were prepared and evaluated for the glycerol hydrogenolysis to 1, 3-PDO. The highest reaction activity and 1, 3-PDO selectivity were achieved at a WO_x density of approximately 1.5–2.0 W·nm⁻², with all three support materials. Such a strong dependence on the surface density of WO_x revealed the critical role of the dispersed WO_x domains in the hydrogenolysis of glycerol to 1, 3-PDO. The infrared spectra for carbon monoxide adsorption confirmed the electron transfer and strong interaction between the Pt particles and WO_x domains. These phenomena were hypothesized to contribute to the superior selectivity to 1, 3-PDO over 1, 2-PDO of the supported Pt-WO_x catalysts when compared with the corresponding supported Pt catalysts. The realized superior 1, 3-PDO selectivity was consistent with its higher stability on the Pt-WO_x catalysts, as reflected by the lower reaction rate constant of 1, 3-PDO than those of 1, 2-PDO and glycerol obtained in their hydrogenolysis reactions. There existed a volcano-type dependence of the glycerol reaction activity on the hydrogen partial pressure. Such a dependence, together with the measured ratio (1 : 2) of the secondary to the primary C−H bonds in 1, 3-PDO in the presence of deuterium and deuterium oxide (replacing hydrogen and water, respectively), indicated that the glycerol hydrogenolysis proceeds by the kinetically relevant dehydrogenation of glycerol to the glyceraldehyde intermediate, followed by the dehydration and hydrogenation of glyceraldehyde to 1, 3-PDO over the Pt-WO_x catalysts.

Natural spider silk is composed of spun spidroin protein containing beta-sheet crosslinking sites drawn from an S-shaped spinning duct. It exhibits an excellent combination of strength (1150 ± 200 MPa) and toughness (165 ± 30 MJ·m^–3) that originates from its hierarchical structure, including crosslinking sites, highly aligned nano-aggregates, and a sheath-core structure. In this work, we prepared a hydrogel fiber that contains crosslinking sites, highly aligned nano-aggregates, and a sheath-core structure, by draw-spinning a bulk hydrogel composed of polyacrylic acid crosslinked with vinyl-functionalized silica nanoparticles (SNVs). The core-sheath structure was prepared by the water-evaporation-controlled self-assembly of the polyacrylic hydrogel, while nanometer-sized aggregates were formed by the self-assembly of polyacrylic acid chains. The addition of a tiny amount of graphene oxide (GO: 0.01%), a 2D nanomaterial, enhanced the mechanical properties of the fiber (breaking strength: 560 MPa; fracture toughness: 200 MJ·m^–3; damping capacity: 94%). In addition, we investigated the factors responsible for the mechanical properties of the gel fibers, including fiber diameter, drying time in air, relative air humidity, and stretching speed. A higher breaking strength and a lower fracture strain was obtained by decreasing the fiber diameter, increasing the drying time, or increasing the stretching speed, while a lower fracture strain and higher breaking strength were obtained by increasing the relative air humidity. Polarized optical and SEM images revealed that the GO-seeded material is better aligned and contains smaller nano-aggregates, with GO seeding found to play a key role in the formation of nano-aggregates and polymer-chain alignment. The prepared fiber exhibited excellent mechanical properties compared to gel fibers prepared by other methods (e.g., electro-, wet, dry, and microfluidic spinning, as well as templating, and 3D printing, etc.). Repeated mechanical testing involving stretch-release cycles to 70% strain at 20% relative humidity revealed that the fibers have an energy-damping capacity of 93.6%, which exceeds that of natural spider silk and many types of artificial fiber. The relaxed stretched fiber recovered its initial length when exposed to 80% relative humidity, while the fiber recovered its initial mechanical properties when stored for 2 h at room temperature. A yarn composed of three hundred of the prepared gel fibers was shown to lift a 3 kg object without breaking; the prepared fiber was also shown to absorb dynamic energy and lower the impact force of a falling object.

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.

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 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.

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.