Na-ion batteries are currently an emerging and low-cost energy storage technology, which have attracted enormous attention and research due to its promising potentiality for large-scale energy storage applications. As the key electrode materials for Na-ion batteries, non-graphite carbonaceous materials have been regarded as the best choice for practical application due to its high sodium storage activity, low-cost and non-toxicity. According to the current research, graphite materials are not suitable to be anode materials of Na-ion batteries for practical application due to its low sodium storage capacity in carbonate electrolytes. Hard carbons have a high capacity of ~300 mAh·g^-1 with low sodium storage potential and thus are suitable for practical applications. Soft carbons have a sodium storage capacity about 200 mAh·g^-1 with sodium storage potential below 1 V vs. Na⁺/Na. Soft carbons usually exhibit excellent rate performances and thus are suitable to be used as anode materials for power Na-ion batteries. Reduced graphene oxide (rGO) has a sodium storage capacity of about 220 mAh·g^-1 and excellent rate performances. A high sodium storage capacity can be obtained by doping heteroatoms and introducing defect sites in rGO. However, the low material density, high sodium storage potential and large irreversible capacity of rGO will restrict its practical application. Porous carbons have high capacities of 300-450 mAh·g^-1 with excellent rate performances because their developed porous structure can provide more defects as the active sites for sodium storage and shorten the diffusion path of Na⁺ to improve rate performances. Carbon nanowires/fibers have good flexibility due to their unique one-dimensional feature and stable sodium storage reversible capacity with good rate performance. These materials have advantages to be flexible electrodes for sodium-based flexible energy storage devices. By introducing N, S and other heteroatoms, heteroatom-doped carbons have more active sites for sodium storage and thus achieve higher sodium storage capacity. In summary, carbon materials with low graphitization degree are important development directions for anode materials of low cost Na-ion batteries. New carbon materials with unique microstructure and morphology have higher sodium storage capacity and rate capability, so they can be used as high power anode materials for sodium storage. Considering many factors, such as cycle life, energy density, power density and manufacturing cost, of practical application, hard carbon anodes is currently the best choice for practical application of Na-ion batteries. In the future, improving SEI stability, increasing Coulombic efficiency and improving electrical conductivity of hard carbon are urgent problems to be solved for practical application. Herein, the recent progress of carbonaceous anode materials is reviewed. The sodium storage mechanism and characteristics of carbon materials are summarized and discussed. Furthermore, the relationship between micro-structures and electrochemical performances, and remained problems of carbon anodes are discussed. This review will promote the development and understanding of carbon anode materials for sodium storage.

The discoveries about the functions of biomolecular liquid-liquid phase separation in cell have been increased rapidly in the past decade. Condensates produced by phase separation play key roles in many cellular curial events. These biological functions are based on the physicochemical properties of phase separation. This review discusses the recent progress in understanding the physical and chemical mechanisms of biological liquid-liquid phase separation. (1) We summarized the basic properties and experimental characterization methods of phase separation droplets, including the morphology, fusion, and wetting, along with the dynamic properties of molecules in droplets, which are usually described by diffusion coefficients or viscosity and permeability. (2) We discussed the conditions affecting the liquid-liquid phase separation of biological molecules, including concentration, temperature, ionic strength, pH, and crowding effects. A database for liquid-liquid phase separation, LLPSDB, was introduced, and three types of nucleic acid concentration effects on the phase separation of protein molecules are discussed. These effects depend on the relative interaction strengths of protein-nucleic acid and protein-protein interactions. The major driving force of phase separation is multivalent interactions, and molecular flexibility is necessary for the dynamic properties. We summarized the diverse sources of multivalence, including multiple tandem repetitive domains, regular oligomerization, low-complexity domains (usually intrinsically disordered with repeat motifs for binding), and nucleic acid molecules via the main chain phosphates or repeat sequences. (3) We reviewed the statistical thermodynamics theories for describing the macromolecular liquid-liquid separation, including the Flory-Huggins theory, Overbeek-Voorn correction, random phase approximation method, and field theory simulation method. We discussed the experimental and simulation methods for studying the physiochemical mechanism of liquid-liquid phase separation. Model systems with simplified sequences for experimental studies were listed, including systems for studying the effects of charge properties, residue types, sequence length, and other properties. Molecular simulation methods can provide detailed information regarding the liquid-liquid phase separation process. We introduced two coarse-grain methods, the slab molecular dynamic simulation and Monte Carlo simulation using the lattice model. (4) The physiochemical properties of liquid-liquid phase separation govern the diverse functions of reversible phase transitions in a cell. We collected and analyzed important cases of biomolecular phase separation in cell activities. These biological functions were classified into five categories, including enrichment, sequestration, biological switching cooperation, localization, and mechanical force generation. We linked these functions with the physiochemical properties of liquid-liquid phase separation. To understand the specific phase-separation processes in biological activities, three types of related molecules must be studied: scaffold molecules mainly contributing to aggregate formation, recruited functional client molecules, and molecules that regulate the formation and disassembly of aggregates. We reviewed four regulation methods for the phase separation process, including changing the charge distribution by post-translational modification, changing the molecular concentration by gene expression or degradation regulation, changing the oligomerization state, and changing the cell solution environment (such as pH). Designing compounds for phase separation regulation has attracted significant attention for treating related diseases. Methods for discovering molecules that can regulate post-translational modifications or inhibit interactions in the droplets are emerging. The recently discovered phase separation phenomena and molecules in living organisms represent only the tip of the iceberg. In the future, it will be necessary to systematically examine liquid-liquid phase separation events and related molecules in all phases of biological processes.

The photocatalytic hydrogen evolution reaction (PHER) has gained much attention as a promising strategy for the generation of clean energy. As opposed to conventional hydrogen evolution strategies (steam methane reforming, electrocatalytic hydrogen evolution, etc.), the PHER is an environmentally friendly and sustainable method for converting solar energy into H₂ energy. However, the PHER remains unsuitable for industrial applications because of efficiency losses in three critical steps: light absorption, carrier separation, and surface reaction. In the past four decades, the processes responsible for these efficiency losses have been extensively studied. First, light absorption is the principal factor deciding the performance of most photocatalysts, and it is closely related to band-gap structure of photocatalysts. However, most of the existing photocatalysts have a wide bandgap, indicating a narrow light absorption range, which restricts the photocatalytic efficiency. Therefore, searching for novel semiconductors with a narrow bandgap and broadening the light absorption range of known photocatalysts is an important research direction. Second, only the photogenerated electrons and holes that migrate to the photocatalyst surface can participate in the reaction with H₂O, whereas most of the photogenerated electrons and holes readily recombine with one another in the bulk phase of the photocatalysts. Hence, tremendous effort has been undertaken to shorten the charge transfer distance and enhance the electric conductivity of photocatalysts for improving the separation and transfer efficiency of photogenerated carriers. Third, the surface redox reaction is also an important process. Because water oxidation is a four-electron process, sluggish O₂ evolution is the bottleneck in photocatalytic water splitting. The unreacted holes can easily recombine with electrons. Sacrificial agents are widely used in most catalytic systems to suppress charge carrier recombination by scavenging the photogenerated holes. Moreover, the low H₂ evolution efficiency of most photocatalysts has encouraged researchers to introduce highly active sites on the photocatalyst surface. Based on the abovementioned three steps, multifarious strategies have been applied to modulate the physicochemical properties of semiconductor photocatalysts with the aim of improving the light absorption efficiency, suppressing carrier recombination, and accelerating the kinetics of surface reactions. The strategies include defect generation, localized surface plasmon resonance (LSPR), element doping, heterojunction fabrication, and cocatalyst loading. An in-depth study of these strategies provides guidance for the design of efficient photocatalysts. In this review, we focus on the mechanism and application of these strategies for optimizing light absorption, carrier separation and transport, and surface reactions. Furthermore, we provide a critical view on the promising trends toward the construction of advanced catalysts for H₂ evolution.

Carbon dioxide is the most common compound. As a potential source of carbon, it can be used to prepare a variety of high value-added chemicals, such as carbon monoxide, methane, methanol, and formic acid. The traditional method of thermal catalytic conversion of CO₂ requires high energy consumption and harsh reaction conditions. Therefore, the efficient conversion of CO₂ to value-added chemicals under mild conditions has long been an area of great interest in the field of catalysis. Photocatalysis usually takes place under mild reaction conditions and is environmentally friendly. However, pure photocatalytic reactions generally have a limited solar energy utilization efficiency and low separation efficiency of photogenerated charge carriers. In view of the above problems, the introduction of electrocatalysis on the basis of photocatalysis can improve the charge separation efficiency. At a lower overpotential, multi-electrons and protons can be transferred to CO₂, thus improving the catalytic reaction efficiency. Photoelectrochemical catalysis combines the advantages of photocatalysis and electrocatalysis to improve the efficiency of the catalytic reduction of CO₂, offering a new method for the clean utilization of CO₂. According to the principle of photocatalysis, the absorption capacity of a semiconductor is governed by its band structure. Optimization of the band structure is a major strategy to enhance the absorptivity of photocatalysts. In addition, the loading of light-absorbent materials on photocatalysts is an effective way to enhance the photocatalytic absorption of a photocatalytic system. During photoelectrocatalytic CO₂ reduction, numerous photogenerated charge carriers recombine in bulk and on the surface of the catalyst, greatly reducing the efficiency of the catalytic reaction. Therefore, increasing the separation efficiency of charge carriers is an important means to improve the photoelectrocatalytic efficiency. In photoelectrocatalytic CO₂ reduction, heterojunction construction and electric field formation often lead to the efficient separation of charge carriers. The interfacial reaction is a crucial step in the photoelectrocatalytic process. After generation, the photogenerated charge carriers need to migrate to the surface of the catalyst to participate in the redox reaction. In photoelectrocatalytic CO₂ reduction, electrons participate in the reduction of CO₂, while holes participate in the oxidation of water. Studies show that acceleration of the interfacial reaction process is of paramount importance for improving the efficiency of the photoelectrocatalytic reduction of CO₂. This review summarizes the basic enhancement strategies of photoelectrocatalytic CO₂ reduction from three aspects: light absorption, charge separation, and surface reaction, based on the basic mechanism of the reduction. The future prospects and research areas are also proposed.

Supercapacitors have attracted considerable attention as new-generation energy storage devices because of their high charge-discharge rate, ultralong lifetime, and high power density. However, the performance of supercapacitors is severely restricted by either the low intrinsic capacitance of porous carbons or the poor conductivity and sluggish electrochemical kinetics of pseudocapacitive components. Therefore, high-performance electrode materials integrated with high gravimetric and volumetric capacitances, high rate capability, and superb cycling stability are urgently needed. As emerging carbon nanomaterials, carbon-/graphene quantum dots (CDs/GQDs) have uniquely small particle sizes, abundant edge sites, and various functional groups, thus endowing them with great potential for developing high-performance electrode materials for supercapacitors. With the purpose of identifying the application advantages and critical problems of CDs/GQDs for supercapacitor electrodes, this review summarizes the development of CDs/GQDs, quantum dots (QDs)/conductive carbon, QDs/metal oxides, QDs/conductive polymer composites, and QD-derived carbon materials in recent years. In each section of this paper, we introduce the typical and updated studies from corresponding fields in terms of novel preparation routes, the crucial roles of CDs/GQDs in composite materials, and the electrochemical performance of electrode materials and assembled devices. Finally, the advantages and limitations of CD/GQD electrode materials are described, and the future development of QD-based materials is discussed. In general, the previous studies have shown that when directly used as electrode materials for micro-supercapacitors, CDs/GQDs performed at an ultrahigh charge-discharge rate of up to 1000 V∙s⁻¹. However, because of the discontinuous conductive network and good dispersibility in electrolytes, they are not suitable for use in common devices because of poor cycle stability. One of the most promising means for fully realizing active ion storage sites for portable devices is to strongly anchor CDs/GQDs onto conductive carbon scaffolds such as activated carbon, graphene nanosheets, and carbon nanofibers. QDs simultaneously improve the capacitive and rate performance owing to the active sites and improved surface wettability of the composite materials. To further improve the capacitance and cycle stability of electrode materials, different types of QDs/pseudocapacitive material composites (metal oxides or conductive polymers) have been developed. QDs have been shown to increase entire conductivity, accelerate ion transport, and depress the volume expansion of metal oxides and conductive polymers. Benefiting from their small-sized structure and outstanding reactivity, CDs/GQDs can also be used as emerging precursors for constructing advanced carbon electrode materials. Several forward-looking studies have shown that QDs can be converted to carbon nanosheets, heteroatom-doped carbon, and dense and porous carbon blocks with high gravimetric/volumetric capacitances and remarkable rate performance for fast and compact energy storage. Although related fields have rapidly developed in recent years, several critical problems including those related to green and effective methods to prepare CDs/GQDs, construction of entire conductive networks without active sites being sacrificed, the synergistic effect, and the underlying mechanism of QDs in composite materials still must be solved. We hope that this review can provide inspiration and references for further investigation in this promising field.

Supercapacitors have been widely used in various fields because of their high power density, long cycle life, and cost-effectiveness. Plant-based porous carbon continues to be the most suitable alternative for manufacturing the commercial electrode materials of supercapacitors because of its good electrochemical performance, simple preparation process, high availability, and low cost. Although plant-based porous carbon prepared using physical activation has been widely used in commercial supercapacitors, its performance is severely restricted because of its low value of specific surface area and highly microporous structure. With a view to achieving high values of specific gravimetric/volumetric capacitances and outstanding rate performance in supercapacitors, this review summarizes the recently developed methods for preparing plant-based ultrahigh specific surface area porous carbon materials, mesoporous carbon materials, hierarchical porous carbon materials, and nitrogen-doped porous carbon materials. The factors affecting the electrochemical performance of plant-based porous carbon are also discussed. We also summarize some novel strategies to improve the volumetric electrochemical performance of plant-based porous carbon materials, such as preparing dense and porous carbon materials, performing heteroatom doping, and combining the carbon with pseudocapacitive materials (conductive polymers or metal oxides). Finally, the challenges and perspectives of using plant-based porous carbon in supercapacitors are also proposed. In brief, when used as the electrode material for supercapacitors, the ultrahigh surface area porous carbon prepared by KOH activation shows high value of specific capacitance at low current densities. However, the tortuous and deep micropores in the plant-based porous carbon result in its sluggish ion-transport kinetics and high value of equivalent series resistance, which, in turn, result in poor rate performance. To improve the rate performance, tremendous efforts have been made to introduce mesopores in the carbon as ion-transport channels. However, this strategy usually involves the coalescence of a large number of micropores, resulting in the reduced surface area as well as energy storage ability of the carbon. Hence, many researchers have utilized the inherent porous structure and inorganic templates of plants to prepare hierarchical porous carbon both with high specific surface area and high mesopore volume for use in devices with high capacitance and power. In addition to altering the surface area and pore structure of the carbon, doping with nitrogen is another promising approach to enhance the capacitance and electronic conductivity of the plant-based porous carbon. Surface nitrogen can be introduced by the direct carbonization/activation of nitrogen-rich plant precursors or by the reaction of the carbon with nitrogen-containing reagents. Porous carbon with large specific area and with developed mesoporous structure may exhibit superior gravimetric capacitance but inferior volumetric capacitance because of the trade-off between its well-developed microporous structure and packing density. To improve the volume performance, some methods, such as preparing dense and porous carbon with reasonably porous structure, using heteroatom-doped carbon, and incorporating the carbon with pseudocapacitive materials, have been developed. Although the electrochemical performance of plant-based porous carbon has been significantly improved using the aforementioned methods, yet issues such as the lack of green methods and low-cost activation methods to prepare large surface area porous carbon, the design and controlled modulation of carbon micro-structures, the influence of heteroatom doping on pseudocapacitance, and weak interaction between pseudocapacitive components and plant-based porous carbon still need to be resolved. We hope that this review may provide the necessary background and ideas to develop more effective preparation methods for high-performance plant-based porous carbon.

Owing to their high power density, excellent rate performance, and good cycle performance, supercapacitors are widely used for energy storage applications. Two-dimensional (2D) layered materials are structural compounds having a layered host structure with a layer thickness of nanometers and a lateral dimension of several micrometers. Their layer spacing can be controlled by changing the interaction between the layers. 2D layered materials can be delaminated into nanosheets. Exfoliated nanosheet materials provide a new strategy for improving the performance of supercapacitors. Unlike bulk layered materials, the exfoliated nanosheets not only provide a unique nano-scale reaction space for electrochemical reactions, but also offer the possibility for improving the specific capacitance and storage rate of the supercapacitor. However, in 2D layered materials, the ion or electron transport in the vertical direction is obstructed, despite their fast ion and electron transport in the horizontal direction. As a result, the occurrence of electrode reactions, and hence the realization of rapid storage become difficult. It is detrimental to the power and energy densities and rapid energy storage of supercapacitors. Therefore, it is imperative to develop novel electrode materials in order to fabricate supercapacitors showinghigh energy densities at high power densities.

Porous 2D layered electrode materials offer two major advantages. First, the porous structure can alleviate the problems caused by the stacking of nanosheets during the assembly process. Second, the porous structure can effectively promote the electrolyte penetration of the electrode, which alleviates the volume changes of the electrode material during the charging-discharging process and releases the structural strain. Hence, such materials facilitate ion or electron transport, thus increasing the specific capacitance of the supercapacitor. Over the past few years, 2D nanosheet holeization has evolved as a promising approach to improve the energy density of supercapacitors at high power densities. Various porous 2D layered supercapacitor electrode materials have been developed. This paper reviews the exfoliation of 2D layered materials, nanosheet holeization strategy, and the application of assembled porous layered electrode materials in supercapacitors. In this paper, we have reviewed the exfoliation of 2D layered materials with different electric properties and the performance of 2D nanosheets. Different methods used for the preparation of holey 2D nanosheets have also been discussed. We prepared holey MnO₂ nanosheets and reduced graphite oxide via redox holeization mechanism, and 2D porous nanomaterials were also prepared by using suitable templates such as hard or self-sustaining templates. These holey 2D nanosheets were used to prepare porous 2D layered electrode materials such as holey graphene/manganese dioxide composite fibers and holey graphene/polypyrrole hybrid aerogels. The capacitance of these electrode materials was investigated systematically. Finally, the prospects for the development of porous 2D layered electrode materials such as the optimization of theirrate performance, flexibility, and energy density were discussed. Novel holeization methods should be developed in order to prepare metal oxide nanosheets with controllable hole sizes. In addition, other 2D materials such as MXene should be explored.

Converting solar light into chemical energy is currently a hot topic for addressing the worldwide energy and environmental crises. However, the utilization of solar energy greatly suffers from its low energy flow density and discontinuous space-time distribution, which are essential for a reasonable energy conversion strategy toward effective storage and utilization. To this end, photocatalytic water splitting is a promising method for utilizing solar light to produce environmentally friendly hydrogen energy; yet, the efficiency needs to be improved. Generally, such processes can be divided into three elementary steps: light absorption, charge separation and migration, and surface redox reaction. The overall performance is determined by the cumulative efficiencies of the above three steps. The construction of cocatalysts is among the extensive efforts taken to improve the solar conversion efficiency. First, the cocatalysts possess higher work function than the semiconductors, and the photogenerated electrons migrate from semiconductor to cocatalysts, thereby promoting the charge separation. Second, cocatalysts usually lower the activation energy and provide abundant surface reactive sites. Particularly, the addition of cocatalysts can remarkably accelerate the four-electron transfer O₂ evolution kinetics, which usually requires much higher overpotential and is often considered as the bottleneck for water splitting. Third, cocatalysts can timely remove the photogenerated charges from the surface of the semiconductor and subsequently inhibit the photocorrosion and improve the stability of the photocatalysts. Moreover, the cocatalysts also retard the backward recombination of H₂ and O₂. In general, cocatalysts for water splitting can be classified into three categories: H₂ evolution cocatalysts, O₂ evolution cocatalysts, and dual cocatalysts. The H₂ evolution cocatalysts mainly contain noble metals such as Pt, Au, and other transition metals such as Co, Ni, and Cu and their phosphides or sulfides, which are capable of trapping electrons and promoting proton reduction. The O₂ evolution cocatalysts are often noble metal oxides and transition metal (hydro)oxides and corresponding phosphates, which are always efficient in adsorbing and dissociating water molecules. To realize the overall water splitting, H₂ evolution cocatalysts and O₂ evolution cocatalysts are often integrated on one photocatalyst, which results in the so-called dual cocatalyst system. Furthermore, the performance of cocatalysts can be improved by modulating the loading amount, morphology, particle size, etc. In addition, composites such as Pt/Ni(OH)₂ cocatalyst can not only provide both H₂ and O₂ evolution sites but also accelerate the intrinsic surface redox kinetics by promoting H₂O activation, thus being much more active than the conventional dual cocatalyst system. This review summarizes the important role and design principle of cocatalysts in photocatalytic systems. The construction and functional mechanism of H₂ evolution cocatalyst, O₂ evolution cocatalyst, and dual cocatalysts in overall water splitting photocatalysts are discussed in detail, and the design strategy of new cocatalysts toward water activation is proposed.

The world is currently facing a series of energy-related problems and challenges. In response, scientists are committed to seeking green high-performance energy storage devices to meet the demands of long-term, sustainable, and innovative development in the future. As a new type of green energy storage device, the supercapacitor has the advantages of high power density, high theoretical specific capacitance, fast charge and discharge speed, long cycle life, high safety, environmental friendliness, and economy to help people cope with the energy crisis. In addition, energy storage devices including Li-ion batteries and supercapacitors are being transformed from heavy, rigid, and bulky devices into light, flexible, and small units to fulfill the needs of the next generation. Among these energy storage systems, the electrode material is an important factor affecting the performance of supercapacitors. In recent years, supercapacitors based on manganese dioxide have been widely studied owing to their high theoretical specific capacitance, good chemical stability, and environmental friendliness. At the same time, a variety of two-dimensional materials are also used as supercapacitor electrode materials after graphene. Two-dimensional structural features play an important role in improving the energy density of electric double-layer capacitors and improving the pseudocapacitance of capacitors. To achieve high specific capacitance and high rate of performance, combining manganese dioxide with two-dimensional materials is a promising option. In this paper, we systematically introduce the application of composites that combine two-dimensional materials represented by graphene and manganese dioxide in supercapacitors, and considers the electrochemical properties of these composites. However, there is still a long way to go in order to fabricate a suitable hierarchical structure consisting of two-dimensional materials and manganese dioxide. For example, a suitable two-dimensional material must be chosen and combined with manganese dioxide to form composites that possess excellent electrochemical properties. In addition, the fabrication methods for these composites are a principal factor that affects their performance. Thus, there are reasons for us to strongly believe that if these key issues are resolved, the properties of these composites consisting of manganese dioxide and two-dimensional materials will make great progress. Overall, this paper only points out some general directions for these kinds of composites in the future, such as principles for choosing the two-dimensional materials to combine with manganese dioxide, and the composite methods which have been reported previously. We are pleased that other researchers are being inspired by our work, and we are looking forward to seeing better studies in this field.

Carbon materials can offer various micro- and nanostructures as well as bulk and surface functionalities; hence, they remain the most popular for manufacturing supercapacitors. This article critically reviews recent developments in the preparation of carbon materials from new precursors for supercapacitors. Typical examples are activated carbon (AC) and graphene, which can be prepared from various conventional and new precursors such as biomass, polymers, graphite oxide, CH₄, and even CO₂ via innovative processes to achieve low-cost and/or high specific capacitance. Specifically, when producing AC from natural biomasses or synthetic polymers, either new, spent, or waste, popular activation agents, such as KOH and ZnCl₂, are often used to process the ACs derived from these new precursors while the respective activation mechanisms always attract interest. The traditional two-step calcination process at high temperatures is widely employed to achieve high performance, with or without retaining the morphology of the precursors. The three-step calcination, including a post-vacuum treatment, is also the preferred choice in many cases, but it can increase the cost per capacity (kWh∙g⁻¹). More recently, one-step molecular activation promises a better and more economical approach to the commercial application of AC, although further increase of the yield is necessary. In addition to activation, graphitization, N doping, and template control can further improve ACs in terms of the charging and discharging rates, or pseudocapacitance, or both. Considerations are also given to material structure design, and carbon regeneration during activation. Metal-organic frameworks, which were initially used as templates, have been found to be good direct carbon precursors. Various graphene structures, including powders, films, aerogels, foams, and fibers, can be produced from graphite oxide, CO₂, and CH₄. Similar to AC, graphene can possess micropores by activation. Self-propagating high-temperature synthesis and molten salt processing are newly-reported methods for fabrication of mesoporous graphene. Macroporous graphene hydrogels can be produced by hydrothermal treatment of graphite oxide suspension, which can also be transferred into films. Hierarchically porous structures can be achieved by H₂O₂ etching or ZnCl₂ activation of the macroporous graphene precursor. Sponges as templates combined with KOH activation are applied to create both micro- and macropores in graphene foams. Graphene can grow on fibers and textiles by electrodeposition, dip-coating, or filtration, which can be woven into clothes with a large area or thick loading, illuminating the potential application in flexible and wearable supercapacitors. The key obstacles in AC and graphene production are high cost, low yield, low packing density, and low working potential range. Most Carbon materials derived from new precursors work very well with aqueous electrolytes. Charge storage occurs not only in the electric double layer (i.e., the "carbon | electrolyte" interface), but also via redox activity in association with the bulk and surface functionalities, and the resulting partial delocalization of valence electrons. The analysis of the capacitive electrode has shown a design defect that prevents the working voltage of a symmetrical supercapacitor from reaching the full potential window of the carbon material. This defect can be avoided in AC-based supercapacitors with unequal electrode capacitances, leading to higher cell voltages and hence higher specific energy than their symmetrical counterparts. There are also emerging ways to raise the energy capacity of AC supercapacitors, such as the use of redox electrolytes to enable the Nernstian charge storage mechanism, and of the three dimensional printing method for a desirable electrode structure. All these developments are promising carbon materials from various precursors of new and waste sources for a more affordable and sustainable supercapacitor technology.

The increased demand for high-performance supercapacitors has fueled the development of electrode materials. As an important part of supercapacitors, the electrochemical performance of the supercapacitor is directly affected by the specific surface area, conductivity, electrochemical activity, and stability of electrode materials. In the traditional manufacturing method, a binder must be added to powdered electrode materials to enhance their combination with the current collector, which could lead to morphology damage, pore blockage, and reduced conductivity of active materials that will adversely affect their electrochemical behavior. Thus, research on binder-free electrode materials has attracted significant interest. Recently, electrospun nanofibers have been widely used as supercapacitor electrode materials because of their advantages such as large specific surface area, high porosity, and easy preparation. The attainable continuity and flexibility endow electrospun nanofiber membranes outstanding performance among large numbers of binder-free materials. This review considers recent studies on electrospun nanofiber-based binder-free electrode materials for supercapacitors, including carbon nanofibers, carbon-based composite nanofibers, conductive polymer-based composite nanofibers, and metal oxide nanofibers. These studies demonstrate that pore structure construction, activation treatment, and nitrogen doping can improve the specific surface area, electrochemical activity, wettability, and graphitization degree of carbon nanofibers to enhance their electrochemical properties. Moreover, combining carbon nanofibers with metal oxides, metal sulfides, metal carbides, and conductive polymers by methods such as blending, chemical deposition, electrochemical deposition, etc., can improve their capacitance, rate performance, and cycling stabilities, which complement the advantages of different materials and proves that the performance of multicomponent materials is better than that of single-component materials. In particular, conductive polymers based on composite nanofibers and metal oxide nanofibers can be used as binder-free materials by electrospinning technology, but their dependence on other substances as well as fragile fiber membrane limit their widespread application. Therefore, in order to ensure the continuity or flexibility of fiber membranes, carbon-based composite nanofibers with multicomponent and hierarchical structure could potentially be used/constructed as binder-free electrode materials. Combinations with new types of electrode materials such as metal-organic frameworks (MOF), covalent organic frameworks (COF), MXenes, metal nitride, metal phosphide, etc., and the preparation of materials with novel structures have also been attempted. In order to realize the practical application of eletrospun nanofiber-based binder-free electrode materials, more attention should be given to improving their mechanical properties, production efficiency, and research on the application of flexible devices. We hope that this review can broaden ideas for improving the development and application of electrospun nanofiber-based binder-free electrode materials for high-performance supercapacitors.

The National Natural Science Foundation of China (NSFC) is a vital government agency supporting basic research and people to create knowledge and meet major national needs, where a rigorous and objective merit-based peer review mechanism is the key to funding the most promising research proposals. This invited comment overviews some recent attempts aimed at bettering the academic evaluation environment at the Department of Chemical Science in 2019, through measures such as grouped panel committee meetings, standardized panel committee meeting procedures, and review process refinement to improve the project review at panel committee meeting levels.

Nuclear magnetic resonance (NMR) is an effective and widely adapted technique that can be used for medical diagnosis and chemical analysis. However, its application has been limited by low sensitivity originating from the extremely low polarization of nuclear spins that follow a typical Boltzmann distribution. In principal, it is possible to break this Boltzmann distribution using different physical or chemical mechanisms to generate hyperpolarization and increase NMR sensitivity by several orders of magnitude. The crucial point of hyperpolarization is to transfer the polarization from highly polarized systems to nuclear spins. For example, the unpaired electrons in organic radicals or other systems exhibit much higher polarization than that of nuclear spins (~660 times higher than ¹H) under the same magnetic field. The high polarization of electrons at thermal equilibrium can be transferred to nuclear spins via microwave irradiation and hyperfine coupling. This hyperpolarization method is called dynamic nuclear polarization (DNP) and has been successfully and widely applied for the evaluation of the protein structure and the examination of nanomaterial surface chemistry. Electron spins can also be hyperpolarized using circularly polarized light (CPL) or nonpolarized light in some systems, and this polarization can be transferred to nuclear spins as well. These hyperpolarization methods are referred to as optical pumping (OP) and optical nuclear polarization (ONP), respectively. A common application of OP is the production of hyperpolarized noble gases, including hyperpolarized xenon-129, which can be used in magnetic resonance imaging of lungs or evaluation of porous structures. For ONP, the nitrogen-vacancy center in diamond is the most promising system that has demonstrated the ability to track the precession of a single spin. In addition, electrons can be polarized by certain chemical reactions as used in chemically induced dynamic nuclear polarization (CIDNP). CIDNP can be used to study the active sites of proteins and identify low-concentration intermediates that are formed during chemical processes. In addition to electrons, hydrogen molecules with unique spin state, i.e., parahydrogen, can be converted to hyperpolarized NMR signals via hydrogen addition reactions, which is known as parahydrogen induced polarization (PHIP). PHIP was originally used to understand the mechanisms of hydrogenation processes, but has recently become a promising hyperpolarization technique via the protocols of signal amplification by reversible exchange (SABRE). Herein, the basic mechanisms and potential applications of DNP, OP, CIDNP, and PHIP techniques are reviewed. These emerging hyperpolarization techniques have the potential to push the limits of NMR beyond current conceptions.

Project proposal review is the core of science foundation management. This article systematically overviews existing key issues in panel committee meetings in final reviews of scientific research grants, which are becoming an increasing concern in the science community. Moreover, it reassesses the importance and functionality of panel committee meetings, and accordingly provides suggestions and measures based on the "verification-rectification-and-selection" principle for further installation and improvement of the panel committee meeting mechanism.

Sodium batteries have drawn increasing attention from multiple researchers owing to the abundant reserves and low cost of sodium resources. However, traditional sodium batteries based on organic solvent electrolyte systems have safety risks. Thus, the utilization of solid electrolyte materials instead of organic electrolytes could effectively resolve safety issues and ensure the safe performance of the battery. Solid sodium-ion battery is a promising energy storage device. The sodium ion solid-state electrolytes mainly includes Na-β-Al₂O₃, Na super ionic conductor (NASICON), sulfide, polymer, and borohydride. Inorganic solid electrolytes have the advantage of ionic conductivity compared with polymer solid electrolyte. This paper summarizes the research progress on three common inorganic sodium ion solid electrolytes: Na-β-Al₂O₃, NASICON, and sulfide. Research efforts have mainly focused on increasing ionic conductivity and interface stability. Na-β-Al₂O₃ has been successfully commercialized in high-temperature Na-S and ZEBRA batteries with molten electrodes. Pure β″-Al₂O₃ is difficult to prepare owing to its low thermodynamic stability. The synthesized β″-Al₂O₃ based on traditional solid-state reaction generally contains impurities such as β-Al₂O₃ and NaAlO₂ (around the boundaries). Further improvements are required to develop favorable methods for fabricating pure β″-Al₂O₃ with high production yield, low cost, and well-controlled microstructure. NASICON, one of the most promising ionic conductors for solid sodium-ion batteries, has attracted considerable attention for its high ionic conductivity at room temperature. The general method to enhance ionic conductivity is to increase the bottleneck size by introducing proper substituents. However, the substitution of synthetic elements could result in different optimal calcination temperatures, which would lead to a change in the density of ceramic sintering. β″-Al₂O₃ and NASICON have higher ionic conductivity at room temperature but cannot achieve good performance in the field of high power densities and long-term cycling owing to the poor interface contact with electrode materials. Because the high polarizability and large ionic radius of sulfur atoms weaken the interaction between skeleton and sodium ions, sulfide solid electrolytes often provide higher ionic conductivity at room temperature than analogous oxides. At the same time, sulfide solid electrolytes can be easily pressed into a mold at room temperature. However, sulfide electrolytes have low chemical stability in air because of hydrolysis by water molecules with the generation of H₂S gas, which should be handled in inert gas atmosphere. In conclusion, this review discusses the recent progress in different aspects of ionic conductivity and interface stability.

Since Fujishima and Honda demonstrated the photoelectrochemical water splitting on TiO₂ photoanode and Pt counter electrode, photocatalysis has been considered as one of the most promising technologies for solving both the problems of environmental pollution and energy shortage. This process can effectively use solar energy, the most abundant energy resource on the earth, to drive various catalytic reactions, such as water splitting, CO₂ reduction, organic pollutant degradation, and organic synthesis, for energy generation and environmental purification. Except for the various metal-based semiconductors, such as metal oxides, metal sulfides, and metal oxynitrides, developed for photocatalysis, graphitic carbon nitride (g-C₃N₄) has attracted significant attention in the recent years because of its earth abundancy, non-toxicity, good stability, and relatively narrow band gap (2.7 eV) for visible light response. However, g-C₃N₄ suffers from insufficient absorption of visible light in the solar spectrum and rapid recombination of photogenerated electrons and holes, thus resulting in low photocatalytic activity. Until now, various strategies have been developed to enhance the photocatalytic activity of g-C₃N₄, including element doping, nanostructure and heterostructure design, and co-catalyst decoration. Among these methods, element doping has been found to be very effective for adjusting the unique electronic and molecular structures of g-C₃N₄, which could significantly expand the range of photoresponse under visible light and improve the charge separation. Especially, non-metal doping has been well investigated frequently to improve the photocatalytic activity of g-C₃N₄. The non-metal dopants commonly used for the doping of g-C₃N₄ include oxygen (O), phosphorus (P), sulfur (S), boron (B), and halogen (F, Cl, Br, I) and also carbon (C) and nitrogen (N) (for self-doping), as they are easily accessible and can be introduced into the g-C₃N₄ framework through different physical and chemical synthetic methods. In this review article, the structural and optical properties of g-C₃N₄ is introduced first, followed by a brief introduction to the modification of g-C₃N₄ as photocatalysts. Then, the progress in the non-metal doped g-C₃N₄ with improved photocatalytic activity is reviewed in detail, with the photocatalytic mechanisms presented for easy understanding of the fundamentals of photocatalysis and for guiding in the design of novel g-C₃N₄ photocatalysts. Finally, the prospects of the modification of g-C₃N₄ for further advances in photocatalysis is presented.

Lithium-ion batteries have been widely used in portable electronic devices and electric vehicles because of their high energy density and long cycle life. Sodium-ion batteries have broad application prospects in the areas of large-scale electrochemical energy storage systems and low-speed electric vehicles because of their abundant raw materials, low resource cost, safety, and environmental friendliness. However, the development of sodium-ion batteries has been hindered by the low reversibility, sluggish ion diffusion, and large volume variations of the host materials. Suitable electrode materials with decent electrochemical performance must be primarily explored for the successful use of sodium-ion batteries. Since the electrochemical potential and specific capacities of cathode materials have a major impact on the energy densities of sodium-ion batteries, the development of cathode materials is critical. To date, various Na-insertable frameworks have been proposed, and some cathode materials have been reported to deliver reversible capacities approaching their theoretical values. Among them, transition metal oxides show a high reversible capacity and high working potential, but most of them still possess problems such as irreversible phase transition, air instability, and insufficient battery performance. Another type is the Prussian blue analogs. These materials exhibit a favorable operating voltage, cycling stability, and rate capability; however, the main obstacles to their practical application are the control of lattice defects, thermal instability, and low tap density. Polyanionic phosphates are the most promising cathode materials for sodium-ion batteries and have great research value and application prospects because of their stable framework structure, suitable operating voltage, and fast ion diffusion channels. However, their inherent defects, such as poor electronic conductivity and low theoretical energy density, considerably limit their practical applications. Researchers have conducted modification studies through bulk structure adjustment and micro-nano structural control with the goal of improving the performance of phosphate cathode materials and promoting the research and development of sodium-ion energy storage systems. This study reviews the recent advances in phosphate cathode materials for sodium-ion batteries, including orthophosphates, pyrophosphates, fluorophosphates, and mixed phosphate compounds. In this study, the intrinsic relationships among material composition, structure, and electrochemical properties are identified through analyses of the crystal structures, sodium storage mechanisms, and modification strategies of phosphate materials, thereby providing a reference for the continuous modification of polyanion phosphate cathode materials and exploration of high-voltage phosphate cathode materials. Some directions for future research and possible strategies for building advanced sodium-ion batteries are also proposed.

With the ongoing depletion of fossil fuels, the exploration of sustainable energy resources and advanced energy technologies is necessary and the development of clean and sustainable energy storage devices has become an important topic worldwide. In this regard, rechargeable batteries and supercapacitors (SCs) are currently considered to be promising electrochemical energy storage systems for widespread applications in electronic devices, electric vehicles, and smart-grid energy storage stations. Batteries typically exhibit high energy densities but are limited by their low power density and relatively poor cycling performance. In contrast, SCs exhibit high power density, stable cyclability, and good safety, but the energy densities of SCs are generally inferior to those of batteries, which hinders their widespread application. A reliable approach to addressing this issue is to fabricate hybrid supercapacitors (HSCs) composed of battery-type and capacitive electrodes. This device configuration enables the direct integration of the high energy densities of batteries and high power densities of SCs, making HSCs a promising class of energy storage devices. However, the mismatch of capacity and rate performance between the battery-type and capacitive electrodes hinders the widespread applications of HSCs. A key challenge for the development of high-performance HSCs is to optimize the balance between both electrodes. Recently, tremendous efforts have been focused on the search for suitable electrodes and considerable progress has been achieved. Nevertheless, in traditional electrodes, binders are commonly used to combine individual active materials with conductive additives. Unfortunately, these binders are generally electrochemically inactive and insulating, reducing the overall specific capacity/capacitance and deteriorating the charge/mass transport. Recently, binder-free nanoarray electrodes have provided a promising opportunity for designing effective HSCs owing to the merits of their direct electron transport pathway, short ion diffusion length, and ordered-structure-enabled abundant reaction sites. This review briefly addresses the energy storage mechanism of HSCs and the advantages of array electrodes, and subsequently reviews the recent advances in emerging HSCs developed by our group. The performance-electrode structure relationship is discussed from the perspective of devices featuring different electrolytes, including organic, aqueous neutral and aqueous alkaline electrolytes. Moreover, some solutions are put forward to solve the existing issues of HSCs, and the potential applications of array electrode-based HSCs in flexible/wearable electronics are envisioned. Finally, the challenges and future development trends of HSCs are proposed.

The rapid development of electronic products has increased the demand for safe, low-cost, and high-performance energy storage devices. Lithium-ion batteries have been commercialized owing to their high energy density. However, the limited lithium resources and their uneven distribution have triggered the search for alternative energy storage systems. In this context, rechargeable aqueous zinc-ion batteries have gained immense attention owing to their low cost and environmental friendliness. Nevertheless, it is highly challenging to develop zinc-ion battery cathode materials with both high capacity and long cycle life. Hence, in this study, we prepared three-dimensional porous activated carbon (3DAC) with high specific surface area by using ethylenediaminetetraacetic acid (EDTA) tetrasodium salt hydrate as the raw material. We developed a zinc-ion hybrid capacitor (ZIHC) in 1 mol∙L⁻¹ ZnSO₄ using 3DAC as the cathode and a zinc foil as the anode. The ZIHC stored charge by the reversible deposition/dissolution of Zn²⁺ on the zinc anode and rapid reversible adsorption/desorption of ions on the 3DAC cathode. Owing to the large specific surface area and highly porous structure of the 3DAC cathode, the assembled ZIHC exhibited excellent electrochemical performance. It worked well over the voltage range of 0.1–1.7 V, providing a high specific capacitance of 213 mAh·g⁻¹ at the current density of 0.5 A·g⁻¹ (the highest value reported till date). The ZIHC showed specific capacities of 182, 160, 139, 130, 127, 122, and 116 mAh·g⁻¹ at the current densities of 1, 2, 4, 6, 8, 10, and 20 A·g⁻¹, respectively. Meanwhile, it exhibited the highest energy density of 164 Wh·kg⁻¹ (at a power density of 390 W·kg⁻¹) and still delivered the highest power density of 9.3 kW·kg⁻¹ with a high energy density of 74 Wh·kg⁻¹. In addition, our ZIHC also exhibited excellent cycling stability. After 20000 cycles at 10 A·g⁻¹, it retained 90% of its initial capacity and exhibited high Coulombic efficiency (≈100%). In order to investigate the causes of capacity decay, we examined the cycled zinc foil by scanning electron microscopy and X-ray diffraction. The results showed that a large number of Zn₄SO₄(OH)₆⋅3H₂O disordered dendrites were formed on the surface of the zinc foil. These dendrites inhibited the reversible deposition/dissolution of zinc ions, resulting in the capacity decay of the ZIHC during the cycling process. This study will be helpful for developing next-generation high-performance energy storage devices.

Methane is a promising energy source with vast reserves, and is considered one of the promising alternatives to nonrenewable petroleum resources because it can be converted into valuable hydrocarbon feedstocks and hydrogen through appropriate reactions. Recently, the conversion of CH₄ into other high-value-added products has received increasing attention because of their sustainability for energy and the environment. However, methane has a tetrahedral geometry with four equivalent C―H bonds due to the sp³ hybridization of the central carbon atom, with a C―H bond length of 0.1087 nm and an H-C―H bond angle of 109.5°. The absence of a dipole moment and the small polarizability (2.84 × 10⁻⁴⁰ C²·m²·J⁻¹) imply that methane requires a high local electric field for polarization and for nucleophilic or electrophilic attack. Nevertheless, it is believed that an effective method to activate CH₄ would be available, so that not only methanol, formaldehyde, and ethylene but also other industrially valuable raw materials can be obtained. On the other hand, the conversion of this combustible gas into the corresponding liquid fossil fuel proceeds via secondary chemical conversion, and it can greatly reduce transportation costs. From the economic viewpoint, this can still provide considerable benefits. Homogeneous catalysts have been reported to catalyze methane, but most of them operate at high pressures (2–7 MPa), or in strongly acidic media and at high temperatures (up to 500 K). Heterogeneous catalysts reported in the literature are also active only at high temperatures. Therefore, finding an efficient method to active methane has become a hot research topic. Photocatalysis technology is recognized as the optimal solution for the conversion of CH₄ since solar energy is by far the largest exploitable resource of energy. In the past years, much effort has been undertaken for the conversion of CH₄ under light at low temperature. In this regard, several photocatalysts, including silica-alumina-titania, silica-supported oxides, and ceria- and zeolite-based materials, have been developed. In photocatalytic methane conversion, the C―H bond can be selectively activated by adjusting the wavelength and intensity of the incident light and the oxidation capacity of the photocatalysts, thereby avoiding the formation of byproducts. This review summarizes a series of photocatalytic direct methane conversion systems developed in recent years, including methane oxidation and coupling processes. The effects of the catalyst composition and structure, oxidant, and electron transfer on the activation of the C―H bond of methane are detailed. Finally, future perspectives and challenges for the photocatalytic conversion of methane are discussed.

All-solid-state sodium ion batteries (ASIBs) are important for future large-scale energy storage applications. ASIBs have come to occupy an important position in research on advanced secondary batteries in recent years owing to their advantages of abundance in resources, low cost, long lifetime, and high safety. As the key to the success of ASIBs, solid-state electrolytes such as polymers, oxide ceramics, and sulfide glass-ceramics have always attracted immense interest. Chalcogenide electrolytes for ASIBs have high room-temperature conductivity, high elastic modulus, and can be easily pressed into a mold at room temperature; hence, they are the research focus in ASIBs. This paper summarized recent studies on the structure and properties of chalcogenide electrolytes for ASIBs. These studies demonstrate the relationship between the phase structure and ionic conductivity of sulfide-based electrolytes and selenide-based electrolytes. Besides, arguments that the sodium vacancy in the crystal structure dominates ionic conduction, and creating a sodium vacancy via cation substitution is the principal strategy to increasing ionic conduction, are discussed. Further, the intrinsic chemical stability and interface stability between the electrode and electrolyte are highlighted. Based on the soft and hard acid and base theory, some studies adopted various anion/cation ion substitution strategies to improve the chemical stability of chalcogenide electrolytes in humid air. Particularly, the inconsistency in the electrochemical stability window of a representative chalcogenide electrode, Na₃PS₄, as measured by a semi-blocking electrode and calculated by first-principles, is compared. Additionally, to develop all-solid-state Na-S and Na-O₂ batteries with high capacity, the nonnegligible interface instability of the sulfide electrode against the sodium metal anode and feasible solutions are summarized. Next, the research progress on ASIBs using chalcogenide electrolytes is reviewed. Chalcogenide electrolytes are restricted by the electrochemical stability window and chemical compatibility with electrode materials; hence, they are expected to only be applicable to ASIBs using sulfur, sulfide, and organic matter as the cathode and Na-Sn alloy as the anode. However, these ASIBs have long cycling life (> 500 cycles), illustrating their potential applications in large-scale energy storage power stations. Finally, we comprehensively evaluate the ionic conductivity, stability against humid air, stability of the interface, electrochemical stability window, and ease of preparation of typical chalcogenide electrolytes, including Na₃PS₄, Na₃PSe₄, Na₃SbS₄, Na₃SbSe₄, Na₁₀SnPS₁₂, and Na₁₁Sn₂PS₁₂. Moreover, we highlight the challenges and propose possible solutions toward the development of chalcogenide electrolytes in future. Advanced technologies in fine synthesis, in situ characterization, and surface/interface modification are essential to overcome existing challenges and promote the development of chalcogenide-electrolyte-based ASIBs.

Lithium-ion batteries (LIBs) are widely used in cellphones, laptops, and electric cars owing to their high energy density and long operational lifetime. However, their further deployment in large-scale energy storage systems is restricted by the uneven distribution of lithium resources (~0.0017% (mass fraction, w) in the Earth's crust). Therefore, alternative energy storage systems composed of abundant elements are of urgent need. Recently, sodium-ion batteries (SIBs) have attracted significant attention and are considered to be a potential alternative for next-generation batteries owing to abundant sodium resources (~2.64% (w) of the Earth's crust), suitable potential (−2.71 V), and low cost. SIBs are similar to LIBs in terms of their physical and electrochemical properties. Previous studies have mainly focused on SIB storage materials, including hard carbon, alloys, and hexacyanoferrate, while the safety of SIBs remains largely unexplored. Similar to LIBs, the current electrolytes used in SIBs are mainly composed of flammable organic carbonate solvents (or ether solvents), sodium salts, and functional additives, which pose possible safety issues. Moreover, the chemical activity of sodium is much higher than that of lithium, leading to a higher risk of fire, thermal runaway, and explosion. To overcome this problem, herein we propose a fluorinated non-flammable electrolyte composed of 0.9 mol∙L⁻¹ NaPF₆ (sodium hexafluorophosphate) in an intermixture of di-(2, 2, 2 trifluoroethyl) carbonate (TFEC) and fluoroethylene carbonate (FEC) in a 7 : 3 ratio by volume. Its physical and electrochemical properties were studied by ionic conductivity, direct ignition, cyclic voltammetry, and charge/discharge measurements, demonstrating excellent flame-retarding ability and outstanding compatibility with sodium electrodes. The electrochemical tests showed that the Prussian blue cathode retained a capacity of 84 mAh∙g⁻¹ over 50 cycles in the prepared electrolyte, in contrast to the rapid capacity degradation in a flammable conventional carbonate electrolyte (74 mAh∙g⁻¹ with 57% capacity retention after 50 cycles). To test the practical application of the proposed electrolyte, a hard carbon anode was used and exhibited exceptional performance in this system. The enhancement mechanism was further verified by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning emission microscopy (SEM) investigations. Polycarbonate on the surface of the cathode played an important role for the studied electrolyte system. The polycarbonate may originate from FEC decomposition, which can enhance the ionic conductivity of the solid electrolyte interface (SEI) layer and reduce impedance. Hence, we believe that this proposed electrolyte may provide new opportunities for the design of robust and safe SIBs for next-generation applications.

Sodium-ion batteries (SIBs) are promising candidates to replace lithium-ion batteries (LIBs) to meet the emergent requirements of various commercial applications. SIBs and LIBs are similar in many aspects, including their reduction potentials, approximate energy densities, and ionic semidiameters. Analogously, safety issues, including liquid leakage, high flammability, and explosiveness limit the usage of SIBs. All-solid-state batteries have the potential to solve the aforementioned problems. However, polycarbonates as promising solid electrolytes have been rarely exploited in all-solid-state SIBs. In addition, organic electrode materials, including non-conjugated redox polymers, carbonyl compounds, organosulfur compounds, and layered compounds, have been intensively investigated as part of various energy storage systems owing to their low cost, environmental friendliness, high energy density, and structural diversity. Nevertheless, the dissolution of small organic compounds in organic-liquid electrolytes has hindered its further applications. Fortunately, the utilization of solid polymer electrolytes combined with organic electrode materials is a promising method to prevent dissolution into the electrolyte and improve the cycling performance of SIBs. Thus, we proposed the utilization of a poly(propylene carbonate) (PPC)-based solid polymer electrolyte and cellulose nonwoven with a 3, 4, 9, 10-perylene-tetracarboxylicacid-dianhydride (PTCDA) cathode in an all-solid-state sodium battery (ASSS). The solid electrolyte significantly enhanced the safety of the SIB and was successfully synthesized via a facile method. The morphology of the as-prepared solid electrolyte was examined by electron scanning microscopy (SEM). Furthermore, the electrochemical performances of the PTCDA/Na battery with organic-liquid and solid electrolytes at room temperature were compared. The SEM results demonstrated that the solid polymer electrolyte and sodium bis(fluorosulfonyl)imide (NaFSI) were evenly distributed inside the pores of the nonwoven cellulose. The ionic conductivity of the composite solid polymer electrolyte (CSPE) at room temperature was 3.01 × 10^-5 S·cm^-1, suggesting that the CSPE was a promising candidate for commercial applications. In addition, the ASSS showed significantly improved cycling performance at a current density of 50 mAh·g^-1 with a high capacity retention of 99.1%, whereas the discharge capacity of the liquid PTCDA/Na battery was only 24.6mAh·g^-1 after 50 cycles. This indicated that the cycling performance of the PTCDA cathode in the SIB was largely improved by preventing the dissolution of the PTCDA cathode material in the electrolyte. Electrochemical impedance spectroscopy results demonstrated that the CSPE was compatible with the organic cathode electrode.

In this study, a novel silicon carbide/platinum/cadmium sulfide (SiC/Pt/CdS) Z-scheme heterojunction nanorod is constructed using a simple chemical reduction-assisted hydrothermal method, in which Pt nanoparticles are anchored at the interface of SiC nanorods and CdS nanoparticles to induce an electron-hole pair transfer along the Z-scheme transport path. Multiple characterization techniques are used to analyze the structure, morphology, and properties of these materials. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results show that the SiC/Pt/CdS materials with good crystal structure are successfully synthesized. Transmission electron microscopy reveals that Pt nanoparticles grow between the interfaces of SiC nanorods and CdS nanoparticles. UV-Vis diffuse reflectance spectroscopy shows that the as-prepared Z-scheme heterojunction samples have a wider light absorption range in comparison with pristine CdS materials. Photoluminescence spectroscopy and the transient photocurrent response further demonstrate that the SiC/Pt/CdS nanorod sample with an optimal molar ratio possesses the highest electron-hole pair separation efficiency. The loading amount of CdS on the surface of SiC/Pt nanorods is effectively adjusted by controlling the molar ratio of SiC and CdS to achieve the optimal performance of the SiC/Pt/CdS nanorod photocatalysts. The optimal H₂ evolution capacity is achieved at SiC : CdS = 5 : 1 (molar ratio) and the maximum H₂ evolution rate reaches a high value of 122.3 µmol·h⁻¹. In addition, scanning electron microscopy, XRD, and XPS analyses show that the morphology and crystal structure of the SiC/Pt/CdS photocatalyst remain unchanged after three cycles of activity testing, indicating that the SiC/Pt/CdS nanocomposite has a stable structure for H₂ evolution under visible light. To prove the Z-scheme transfer mechanism of electron-hole pairs, selective photo-deposition technology is used to simultaneously carry out the photo-reduction deposition of Au nanoparticles and photo-oxidation deposition of Mn₃O₄ nanoparticles in the photoreaction. The experimental results indicate that during photocatalysis, the electrons in the conduction band of CdS participate mainly in the reduction reaction, and the holes in the valence band of SiC are more likely to undergo the oxidation reaction. The electrons in the conduction band of SiC combine with the holes in the valence band of CdS to form a Z-scheme transport path. Therefore, a possible Z-scheme charge migration path in SiC/Pt/CdS nanorods during photocatalytic H₂ production is proposed to explain the enhancement in the activity. This study provides a new strategy for synthesizing a Z-scheme photocatalytic system based on SiC nanorods. Based on the characterization results, it is determined that SiC/Pt/CdS nanocomposites are highly efficient, inexpensive, easy to prepare, and are stable structures for H₂ evolution under visible light with outstanding commercial application prospects.

完善评审机制是国家自然科学基金委新时代基金改革的重要任务之一。为切实落实该项改革任务，建立符合新时代科学基金资助导向的科学、公正、高效的评审机制，基金委化学部努力探索新的学科基金管理模式，尝试了在通信评审阶段由科学家与学科管理人员共同参与项目的分组、指派，共同完成同行评议专家遴选工作的新模式。本文分析了科学家参与同行评议专家遴选工作的利弊，探讨了如何更好的发挥科学家在同行评议专家遴选工作中的作用，建立学术共同体互信的基金评审机制。

Because of their high energy density and long cycle life, lithium-ion batteries (LIBs) have dominated the portable electronics market for over 20 years. However, with the increasing demand for large-scale energy storage systems for grid applications, the price of Li resources has increased owing to the low abundance of Li in Earth's crust and non-uniform distribution on the planet. Because Na has similar physical and chemical properties as Li and is an abundant natural resource, room-temperature sodium-ion batteries (SIBs) are expected to be among the most promising next-generation large grid energy storage devices. It is known that the cathode, anode, separator and electrolyte materials are the main components of batteries. Among these, Na-containing cathode materials are of critical importance. As a cathode material for SIBs, polyanion-type compounds have become a hot research topic owing to their versatile structural frameworks, high thermal stabilities, high ambient stabilities even in the charging state, small volume changes, tunable operating voltage by tuning the chemical environment of the polyanions, and high operating voltages owing to the inductive effects of the polyanionic groups (PO₄³⁻, SO₄²⁻, SiO₄⁴⁻, etc.). In particular, for Earth's abundant resources and inherent stability, polyanion-based compounds are suitable for large-scale stationary energy storage. Taking grid balancing into account, batteries with fast charge rates are in demand, which requires cathodes having high rate capability. However, despite the presence of ion diffusion channels in polyanion compounds, the electronic transport channels are blocked owing to the separation of the metal polyhedral and the strong electronegativity of the anions, leading to poor electron conductivity, which largely limits the rate capability of polyanion compounds. Therefore, it is crucial to understand the inherent limitation of the kinetics in terms of the structural aspects and to determine strategies for improving the rate capability. This review discusses the intrinsic reasons for the factors impacting ion diffusion based on the different structures of polyanion-type cathodes. From the perspectives of surface modification and morphology, strategies for enhancing the transport of sodium ions and electrons at the surface and interface are summarized and discussed. Then, from the standpoint of the hierarchical structures of materials to the design of a structural framework, which have been rarely reported, this review proposes schemes that intrinsically enhance the rate capability of polyanion compounds and provides a perspective on developments that can further improve the rate capability of cathode materials. This review provides suggestions for designing and optimizing high-rate polyanion-type and other kinds of cathodes from both academic and practical viewpoints.

The rapid economic development has necessitated increased environmental protection and tremendous efforts have been devoted to designing and preparing environmentally friendly energy storage and conversion devices, including batteries, supercapacitors (SCs), and solar cells. As useful energy storage and conversion devices, SCs have received significant attention due to their high power density, long cycle stability, and rapid charging rate. The performance of SCs largely depends on the electrode materials, which can be composed of metal oxides, conducting polymers, carbon materials, and their composites. Carbon materials, including carbon nanotubes, carbon fibers, porous carbons, template carbons, and graphene-like carbon nanosheets (GCNSs), have attracted significant attention owing to their tailorable pore size and excellent physiochemical stability. GCNSs are considered to be outstanding carbon materials for use in high-performance SC because of their large specific surface area and high electrical conductivity. To date, many carbon precursors have been used to synthesize GCNSs for SCs such as coal, biomass, and chemical by-products. In particular, cheap and abundant chemical by-products for the synthesis of carbon materials can reduce preparation costs and environmental pollution as well as achieve high value-added chemicals. Coal tar, a by-product of the coal coking process, is rich in aromatic polycyclic hydrocarbon molecules, which can be polymerized, carbonized, and activated to synthesize GCNSs for SCs. In addition, MgO particles can be used as templates due to their stable properties and low-cost compared with other metal oxide templates (e.g. Fe₂O₃, NiO, or CuO), imparting space confinement and structure guidance during the preparation of GCNSs. Herein, we report a facile method for the preparation of interconnected graphene-like nanosheets (IGNSs) from coal tar by MgO templating combined with in-situ KOH activation. The IGNSs were obtained after the impurity removal by repeated washing with dilute acid. The as-synthesized IGNSs feature high specific surface area of up to 2887 m²∙g⁻¹ and abundant hierarchical short pores, which provide abundant active sites for ion adsorption, supply plentiful channels for fast ion transport and boost electrical conductivity. As electrodes for SCs, IGNSs manifest high specific capacitance value of up to 313 F∙g⁻¹ at 0.05 A∙g⁻¹, good rate capability of 261 F∙g⁻¹ at 20 A∙g⁻¹, and excellent cycle stability with 92.7% of initial capacitance retained after 10000 cycles in 6 mol∙L⁻¹ KOH aqueous electrolyte. This study provides a facile method for large-scale production of IGNSs from aromatic hydrocarbon molecules for use in high-performance energy storage devices.

Sodium has the advantages of being an abundant resource and having a low cost; thus, sodium ion batteries are considered as one of the best candidates for replacing lithium ion batteries in the future. However, the radius of the sodium ion is larger than that of the lithium ion, and the de-intercalation of the sodium ion will seriously damage the crystal structure of most electrode materials during the charging and discharging process, which considerably limits its charge-discharge specific capacity, cycle performance, and rate performance. However, finding appropriate electrode materials is one of the difficulties in fabricating high-performance sodium ion batteries. Among the many candidate materials, vanadate materials can improve the stability of material structures by introducing cations to increase the coordination numbers of vanadium, thus improving the electrochemical performance of sodium ion batteries. In this paper, an in situ phase separation method to fabricate V₂O₅/Fe₂V₄O₁₃ nanocomposite materials is reported. First, we synthesized hydrated crystalline Fe₅V₁₅O₃₉(OH)₉·9H₂O nanomaterials using a water bath heating method; then, we in situ constructed two-phase nanocomposite V₂O₅ and Fe₂V₄O₁₃ from the single phase by further high-temperature treatment. The morphology, composition, and structure of the electrode materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy(FTIR), as well as other methods. The V₂O₅/Fe₂V₄O₁₃ nanocomposite materials were found to have a more stable structure, higher initial discharge capacity (342 mAh·g^-1 at a current density of 0.1 A·g^-1), longer cycle life, and better rate performance than V₂O₅ nanowires. Therefore, this research on V₂O₅/Fe₂V₄O₁₃ nanocomposite materials has broadened ability to develop new high-performance anode materials for sodium ion batteries.

The photocatalytic reduction of CO₂ has attracted considerable attention owing to the dual suppression of environmental pollution and energy shortage. The technology uses solar energy to convert carbon dioxide into hydrocarbon fuel, which is of great significance for achieving the carbon cycle. The development of low-cost photocatalytic materials is critical to achieving efficient solar energy to fuels conversion. One of the most commonly employed photocatalysts is TiO₂. However, it suffers from broad band gap as well as the recombination of photo-excited holes and electron. Hence, in this work, we report the photochemical reduction of CO₂ using rod-like PCN-222(Cu)/TiO₂ composites as photocatalyst through a simple hydrothermal method, in which TiO₂ nanoparticles are anchored at the interface of the SiC rod PCN-222(Cu). Multiple characterization techniques were used to analyze the structure, morphology, and properties of the PCN-222(Cu)/TiO₂ composite. A series of characterizations including X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy, photo-electrochemical, and photoluminescence (PL) confirm the successful preparation of PCN-222(Cu)/TiO₂ composites. SEM reveals that the TiO₂ nanoparticles are uniformly distributed on the surface of the rod-shaped PCN-222(Cu)/TiO₂. XRD results show that PCN-222(Cu) and PCN-222(Cu)/TiO₂ composite photocatalysts with good crystal structure were successfully synthesized. According to the DRS results, the prepared PCN-222(Cu)/TiO₂ composite samples exhibit characteristic absorption peaks of metalloporphyrins in the visible region. PL spectroscopy, transient photocurrent response, and electrochemical impedance spectroscopy further confirm that the rod-like PCN-222(Cu)/TiO₂ samples have high electron-hole pair separation efficiency. By controlling the mass ratio of PCN-222(Cu) and TiO₂, the photocatalytic CO₂ reduction performance test shows that the 10% PCN-222(Cu)/TiO₂ composite achieves optimal catalytic performance, yielding 13.24 μmol·g⁻¹·h⁻¹ CO and 1.73 μmol·g⁻¹·h⁻¹ CH₄, respectively. All the rod-like PCN-222(Cu)/TiO₂ composites exhibit better photocatalytic CO₂ activity than that of TiO₂ nanoparticles or PCN-222(Cu) under the illumination of xenon lamps, which is attributed to charge transport and electron-hole separation capabilities. After three test cycles, the catalytic activity of PCN-222(Cu)/TiO₂ photocatalyst was virtually unchanged. The reduction yield of the catalyst increased for 8 h under continuous illumination, indicating that PCN-222(Cu)/TiO₂ composites have acceptable stability. The estimation of the band gap curve and the Mote-Schottky curve test show that the lowest unoccupied molecular orbital position of PCN-222(Cu) is more negative than the TiO₂ of the conduction band; hence, a possible photocatalytic reaction mechanism of the PCN-222(Cu)/TiO₂ composite is proposed. This study provides a new strategy for the integration of metal-organic frameworks and oxide semiconductors to construct efficient photocatalytic systems.

Hydrogen (H₂), a clean and sustainable energy carrier, is regarded as one of the most promising alternatives to carbon-based fuels. Hydrogen can be generated in a more sustainable way from renewable energy sources via electrocatalytic water splitting. However, the high cost and low abundance of the benchmarking platinum-based hydrogen evolution reaction (HER) catalysts hinder their widespread applications. Thus, developing highly efficient, stable, and low-cost electrocatalysts to replace platinum for HER is imperative, but remains a challenging task. Recently, efforts have been devoted to developing non-noble HER electrocatalysts, including transition metal carbides, oxides, phosphides, and sulfides. However, traditional synthetic strategies cannot effectively control active sites and the catalysts tend to aggregate under high temperature. Recently, polyoxometalates (POMs) have been applied as precursors for the preparation of non-noble HER electrocatalysts as they contain discrete metal-oxygen clusters with well-defined structures. POMs are typically composed of oxygen ligands and high-valent metal ions such as Ⅴ(Ⅴ), Mo(Ⅵ), and W(Ⅵ), which can serve as Ⅴ, Mo, and W sources to produce the corresponding metal carbides, oxides, phosphides, and sulfides by pyrolysis at high temperature. Some POMs may also contain a series of redox-active heteroatoms, which are usually named hetero-polyoxometalates. These can serve as precursors to electrocatalysts with uniform heteroatom doping. Moreover, direct applications of POMs as molecular catalysts in HER have, in recent years, received rapidly growing attention. This is because POMs not only serve as mediators or molecular catalysts to facilitate the HER, but can also be deposited on the electrode surface to catalyze the HER. However, the interpretation that HER catalytic activity enhancement is due to the intrinsic catalytic properties of the electrodeposited polyoxometalate or the deposition of small amounts of platinum has been highly debated. Reviewing these studies may help us understand the intrinsic active sites as well the intrinsic HER mechanism of POMs and POMs-derived catalysts, and thus design more efficient HER catalysts. This review, therefore, focuses on recent progress in the applications of POMs and their derivatives in electrocatalytic HER. Firstly, basic HER mechanisms for common metal catalysts and POMs molecular catalysts are discussed along with challenges in the field of HER. Next, applications of POMs molecular catalysts and POMs-derived catalysts in HER are summarized. Finally, some perspectives of POMs-based catalysts/pre-catalysts for electrocatalytic HER are proposed.

In the past few decades, new energy industries have developed rapidly due to the threat of the depletion of non-renewable resources. Among them, the lithium-ion battery has attracted significant attention of various researchers. However, lithium-ion batteries are limited by the uneven distribution of lithium resources and high cost. Sodium, which is in the same periodic group as Lithium, can help alleviate the problems related to the limited development of lithium ion batteries owing to the shortage of lithium resources. Sodium ion batteries are cheap, with varying choice of electrolytes, and have relatively stable electrochemical performances. However, the radius of a sodium ion is larger than that of a lithium ion, leading to slow ion transportation as well as changes in the volume of the host material during the charging and discharging processes. Therefore, compared with existing lithium ion batteries, sodium ion battery anode materials are very limited. Moreover, most sodium ion battery electrode materials have low specific capacities and poor cycle retention rates. Among these, ternary metal oxides, which have two different cations and can reversibly react with sodium ions are promising high-capacity anode materials for sodium ion batteries. In this study, Ti₂Nb₂O₉ nanosheets are obtained by ion-exchange and chemical-delaminate methods. The carbon-coated Ti₂Nb₂O₉ nanosheets are obtained after hydrothermal coating with sucrose and calcination. From the thermogravimetric analysis (TG) curve, the carbon content in the composites is calculated to be approximately 8.0%. Owing to the rich reactive sites and a short ion transport pathway, the Ti₂Nb₂O₉/C electrode delivers a high reversible capacity of 265.2 mAh·g^-1 at a current density of 50 mA·g^-1. Even at a high current density of 500 mA·g^-1, the electrode exhibits an excellent electrochemical performance with a reversible capacity of 160.9 mAh·g^-1 after 200 cycles (capacity retention of 75.3%). Additionally, the Ti₂Nb₂O₉/C nanosheets exhibit high reversible capacities of 251.3, 224.6, 197.4, 176.3, and 156.5 mAh·g^-1 at the current densities of 100, 200, 500, 1000, and 2000 mA·g^-1, respectively. It is demonstrated through the use X-ray photoelectron spectroscopy (XPS) that the following process involving the transfer of four electrons occurs: Ti⁴⁺/Ti³⁺, Nb⁵⁺/Nb⁴⁺, during the charging and discharging process of the Ti₂Nb₂O₉ electrode in the voltage range of 0.01–3.0 V. The theoretical specific capacity of Ti₂Nb₂O₉ in this process is calculated to be 252 mAh·g^-1, corresponding to the electrochemical data. Overall, this study demonstrates that the Ti₂Nb₂O₉/C anode nanosheets have an excellent charge-discharge performance, cycle stability, and rate performance in sodium ion batteries, thereby providing a feasible choice for sodium ion battery anode materials.

Thermal analysis (TA) is a technology that can be applied to evaluate the relationship between the physical properties of substances and temperature changes under programmed temperature control. It has been widely used in many fields and is particularly useful for determining the thermal stability and service life of polymers and other materials, the stability of drugs, and the danger of flammable and explosive materials. Simultaneously, the mechanism of dehydration, decomposition, and degradation of inorganic materials or dissociation of complexes can be studied and the decomposition rates of environmental pollutants can be estimated. Recently, TA kinetics has become the most extensively studied topic in TA research. The main purpose of kinetic analysis is to obtain the three kinetic triplets of a reaction process, namely, activation energy E_a, pre-exponential factors A, and and mechanism function f(a). For a solid-state reaction, many mathematical models and corresponding data processing methods can be used for the study of TA kinetics. These methods can be classified as either isothermal or non-isothermal methods and further divided into integral and differential methods in the form of the kinetic equation. These equations can be divided into a single scanning rate and multiple scanning rate methods (isoconversion method) by the operation method. The isoconversion method can calculate activation energies without the mechanism function, and the complexity of the reaction can be determined by the change in activation energy as a function of conversion rate. Therefore, the International Confederation for Thermal Analysis and Calorimetry (ICTAC) recommends the isoconversion method for processing TA data. Because of the limitation of traditional isoconversion methods, novel isoconversion methods have been proposed over the past 10 years. The relationship among the existing dynamic analysis methods must be complementary, instead of competitive, because the reliability of the analysis results can be improved only through complementarity. Further efforts to popularize modern integral and differential methods with equal conversion rates are essential. Herein, the progress in isoconversion method development is briefly introduced. A novel kinetic equation and seven new isoconversion methods are reviewed, and the characteristics and limitations of these methods are discussed. In addition, the development trends and prospects of TA kinetics research methods are highlighted. We suggest that the Arrhenius formula should be modified on the basis of the relationship between the rate constant and temperature. The rate equation that is more suitable for non-isothermal and heterogeneous reactions should be used. The mechanism of multi-step solid-state reactions should be studied in depth, and unified standards must be adopted for the study of thermal decomposition kinetics. This represents imminent and important progress in the study of TA kinetics.

The fast-growing demand for safe energy storages with high power and energy density drives the continuous improvement of rechargeable Li-ion batteries (LIBs). In situ characterization is a potential way to understand the mechanism (metaphases, diffusion, kinetics, inhomogeneity etc.) of battery under operation conditions. Solid-state nuclear magnetic resonance (SS-NMR) is very sensitive to the local environment of ¹H, ^{6, 7}Li, ¹¹B, ¹³C, ¹⁷O, ¹⁹F, ²³Na, and ³¹P isotopes, which are widely used in battery materials, regardless of their ordering degree. In addition to providing well-resolved spectra obtained under fast magic angle spinning (MAS), NMR can effectively serve as a non-invasive tool to capture the evolution of electrodes/electrolyte upon charge/discharge electrochemical cycling. Subsequently, in situ NMR and imaging (MRI) have been developed for extending toward temporal and spatial dimensions in working batteries. Complementarily, highly sensitive electron paramagnetic resonance (EPR) and imaging (EPRI) have been employed to track and map the redox of transition metals and oxygen species (O₂ⁿ⁻) within electrodes. The insights gained from in situ NMR/EPR and their imaging can serve as a guide for the structural design of energy storage materials and the fabrication of batteries with optimized performance. As such, this review summarizes the applications of both NMR and EPR in the field of battery community. In particular, we first introduce the combination of fast magic angle spinning and phase-adjusted sideband separation (pjMATPASS) to obtain highly resolved spectra for extreme broad signal mediated by unpaired electrons, which is usually found in battery materials, as well as isotope-oriented NMR to determine the Li pathway in the composite electrolyte by the aid of ⁶Li replacing ⁷Li in their transport pathway. Secondly, we introduce the combination of NMR/MRI measurement while battery under electrochemical cycling by (1) briefly summarizing the advantages and disadvantages of home-made cells (coin cell, bag cell, and cylindrical cell) developed for in situ NMR study; (2) using different isotopes for conducting in situ NMR on batteries: ⁷Li, ²³Na, and ³¹P spectra; and (3) performing in situ MRI on electrolytes and electrodes with and without chemical shift information (CSI, S-ISIS, and stray-field MRI). Furthermore, in situ EPR determines and quantifies the evolution of active Li microstructure, transition metals, and oxygen species together with in situ EPRI mapping of the concentration of the paramagnetic center within a functioning battery. Finally, we point out the limitations and perspective of in situ NMR and EPR for cycling batteries in real-time. This review will provide illuminating insights on the magnetic technologies in the battery community and pave a way for carrying out NMR/EPR on functional materials.