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Developing advanced electrocatalysts to convert CO2 into liquid fuels such as ethanol is critical for utilizing intermittent renewable energy. The formation of ethanol, however, is generally less f...

The sluggish electrochemical kinetics of sulfur species has impeded the wide adoption of lithium-sulfur battery, which is one of the most promising candidates for next-generation energy storage system. Here, we present the electronic and geometric structures of all possible sulfur species and construct an electronic energy diagram to unveil their reaction pathways in batteries, as well as the molecular origin of their sluggish kinetics. By decoupling the contradictory requirements of accelerating charging and discharging processes, we select two pseudocapacitive oxides as electron-ion source and drain to enable the efficient transport of electron/Li+ to and from sulfur intermediates respectively. After incorporating dual oxides, the electrochemical kinetics of sulfur cathode is significantly accelerated. This strategy, which couples a fast-electrochemical reaction with a spontaneous chemical reaction to bypass a slow-electrochemical reaction pathway, offers a solution to accelerate an electrochemical reaction, providing new perspectives for the development of high-energy battery systems., The sluggish electrochemical kinetics of sulfur species remains a major hurdle for the broad adoption of lithium-sulfur batteries. Here, the authors construct an energy diagram of sulfur species to unveil their reaction pathways and propose a general strategy to accelerate electrochemical reactions.

Silicon is one of the most promising anode materials for lithium-ion batteries due to its high theoretical capacity and low cost. However, significant capacity fading caused by severe structural degradation during cycling limits its practical implication. To overcome this barrier, we design a covalently bonded nanocomposite of silicon and poly(vinyl alcohol) (Si-PVA) by high-energy ball-milling of a mixture of micron-sized Si and PVA. The obtained Si nanoparticles are wrapped by resilient PVA coatings that covalently bond to the Si particles. In such nanostructures, the soft PVA coatings can accommodate the volume change of the Si particles during repeated lithiation and delithiation. Simultaneously, as formed covalent bonds enhance the mechanical strength of the coatings. Due to the significantly improved structural stability, the Si-PVA composite delivers a lifespan of 100 cycles with a high capacity of 1526 mAh g-1. In addition, a high initial Coulombic efficiency of over 86% and an average value of 99.2% in subsequent cycles can be achieved. This reactive ball-milling strategy provides a low-cost and scalable route to fabricate high-performance anode materials.

Owing to its abundance and high theoretical capacity, phosphorus has attracted intense research interest as anode material for lithium-ion batteries. However, the adaption of phosphorus for batteries is still limited by its poor electrochemical performance, which is associated with its poor electronic conductivity and large volume change during charging and discharging. We herein report a facile and cost-effective method, which is based on high-energy mechanical milling, for the synthesis of phosphorus nanoparticles within carbon matrix as high-performance anode materials. Red phosphorus was readily transformed into orthorhombic black phosphorus at ambient temperature and pressure, forming phosphorus nanocrystals homogenously dispersed in carbon matrix. Such composites provide superior electrochemical performance, exhibiting reversible capacity of 1000 mA h g−1 after 300 cycles. Full cells based on such phosphorus-carbon composites against LiNi1/3Co1/3Mn1/3O2 cathode offer a capacity retention of 92% after 200 cycles at 0.5 C.

Conventional liquid electrolytes for lithium batteries usually suffer from irreversible decomposition and safety concerns. Solid state electrolytes (SSEs) have been considered as the key for advanced lithium batteries with improved energy density and safety, whereas challenges remain for polymer and inorganic SSEs. Recently, hybrid solid-state electrolytes (HSSEs) that integrate the merits of different electrolyte systems have been under intensive study. Herein, we summarize the recent progress of HSSEs with different compositions and structures. The design principle of each type of HSSEs are discussed, as well as their ionic conducting mechanism, electrochemical performance and effects of compositional/structural control. Finally, challenges and perspectives are provided for the future development of HSSEs and solid-state lithium batteries.

Lithium ion capacitors (LICs) hold potentials to bridge the gap between lithium ion batteries and supercapacitors ; however, the imbalance of electrochemical kinetic and stability between Li + storage anode and capacitive cathode has been the key bottleneck. Herein, we report a high-rate and ultrastable anode for this issue, consisting of boron-doped nanoporous carbon spheres which are synthesized by a continuous spraying-assisted co-assembly process. Experimental and computational investigations as well as the comparison with a nitrogen-rich carbon indicate that boron species enhances ion-surface interactions, electron/ion conductivity and carbon framework cycling firmness, leading to dramatically improved rate and cycling performances, which outperform the extensively explored nitrogen doped carbons and most reported high-rate anode materials . By pairing a coal-derived microporous graphene cathode, we constructed a full-carbon LIC device exhibiting high energy and power densities (207 Wh kg −1 at 511 W kg−1 and still 136 Wh kg−1 at 17.06 kW kg−1), as well as an unprecedented cycling stability with no capacity decay after 15,000 cycles at 2 A g−1. This work not only offers a fundamental basis to understand the enhanced anode performance by doping boron into carbon framework but also provides an effective strategy to circumvent the kinetic and stability discrepancies between anode and cathode for high-performance LICs.

To circumvent the imbalances of electrochemical kinetics and capacity between Li+ storage anodes and capacitive cathodes for lithium-ion capacitors (LICs), we herein demonstrate an efficient solution by boosting the capacitive charge-storage contributions of carbon electrodes to construct a high-performance LIC. Such a strategy is achieved by the in situ and high-level doping of nitrogen atoms into carbon nanospheres (ANCS), which increases the carbon defects and active sites, inducing more rapidly capacitive charge-storage contributions for both Li+ storage anodes and PF6– storage cathodes. High-level nitrogen-doping-induced capacitive enhancement is successfully evidenced by the construction of a symmetric supercapacitor using commercial organic electrolytes. Coupling a pre-lithiated ANCS anode with a fresh ANCS cathode enables a full-carbon LIC with a high operating voltage of 4.5 V and high energy and power densities thereof. The assembled LIC device delivers high energy densities of 206.7 and 115.4 W...

Electrochemical reduction of carbon dioxide to value-added fuels offers a promising method to solve increasingly serious environmental problems and alleviate energy crisis. Herein, we report a facile method by coating Cu electrode with CeO2 nanoparticles to largely enhance the C2+ products selectivity during CO2 electroreduction. The Faradaic efficiency of C2+ products for optimal CeO2-coated Cu electrode reached a high value of 61 % at -1.05 V vs RHE, and exhibited good stability for over 9 h of CO2 electrolysis. The CeO2 nanoparticles were found to induce oxidative corrosion of the Cu foil, leading to a CuOx layer in contact with the CeO2 nanoparticles. The interface between CeO2 nanoparticles and oxide-derived Cu might be attributed to the enhanced catalytic activity for C2+ products by promoting the C C coupling process.

Electrochemical reduction of carbon dioxide provides a feasible solution to the energy and climate crisis. Bi-based catalysts are promising candidates to electrochemically convert carbon dioxide (CO2) into formic acid or formate. Herein, ligand-stabilized Bi nanosheets are obtained from in-situ electrochemical reduction of a Bi-based metal-organic framework, which exhibit remarkable electrocatalytic performance for CO2 reduction. A high Faradic efficiency of 98 % for formate is achieved at a potential of -0.80 V vs. reversible hydrogen electrode (RHE) with an improved durability over 40 h. The remarkable electrocatalytic activity and stability could be attributed to the in-situ generated catalyst with abundant under-coordinated Bi active sites, which are effectively stabilized by residual ligands adsorbed on surface. This study demonstrates that ligand-stabilized under-coordinated surface sites would be facilely generated from in-situ transformation of metal-organic precursors for highly efficient CO2 conversion.

Construction of metal–organic frameworks with sophisticated nanostructures remains a considerable challenge. Herein, we report the rational design and synthesis of ZIF-67 nanoscaffolds and defected nanocubes co-mediated by dopamine and polyoxometalate. The formation of these sophisticated ZIF-67 nanostructures is achieved through the protection of dopamine and etching of polyoxometalate. As a demonstration, we have converted the ZIF-67 nanoscaffolds incorporated with molybdenum into carbon-coated cobalt–molybdenum mixed selenides (denoted as CoMoSe@C nanoscaffolds) with little alteration in the structure by reacting the ZIF-67 nanoscaffolds with selenium powder at high temperature. Benefiting from their unique structural merits, the CoMoSe@C nanoscaffolds exhibit enhanced lithium storage properties in terms of good cycling performance and superior rate capability.

By virtue of high theoretical sodium storage capacities and low cost, FeP is a prospective anode material for sodium-ion batteries (SIBs). Nevertheless, poor cycling and rate performance greatly limit the application of FeP in practice. Herein, a facile template-engaged method is employed to synthesize copper and carbon-incorporated yolk-shelled FeP (denoted as YS-Cu-FeP@C) spheres. The copper is doped into FeP, while the carbon layer with N-doping is coated on the surface of yolk-shelled FeP spheres. Aided by the unique compositional and structural advantages, the as-synthesized YS-Cu-FeP@C spheres exhibit enhanced electrochemical performance for SIBs, including excellent rate capability (145 mAh g−1 at 10 A g−1) and remarkable long-term cycle performance (up to 900 cycles at 1 A g−1). This work provides a rational design and synthetic strategy to boost the sodium storage properties of metal phosphide-based electrode materials.

Supercapacitors have high power densities, high efficiencies, and long cycling lifetimes; however, to enable their wider use, their energy densities must be significantly improved. The design and synthesis of improved carbon materials with better capacitance, rate performance, and cycling stability has emerged as the main theme of supercapacitor research. Herein, we report a facile synthetic method to prepare nitrogen-rich carbon particles based on a continuous aerosol-spraying process. The method yields particles that have high surface areas, a uniform microporous structure, and are highly N-doped, resulting in a synergism that enables the construction of supercapacitors with high energy and power density for use in both aqueous and commercial organic electrolytes. Furthermore, we have used density functional theory calculations to show that the improved performance is due to the enhanced wettability and ion adsorption interactions at the carbon/electrolyte interface that result from nitrogen doping. These findings provide new insights into the role of heteroatom doping in the capacitance enhancement of carbon materials; in addition, our method offers an efficient route for large-scale production of doped carbon.

Fluorine-rich nanoporous carbons with tunable porosity and F content have been successfully synthesized from a silane precursor using a solution-based F doping method. The F-rich carbon surface with higher polarity provides stronger affinity and wettability for the organic electrolyte, which is for the first time demonstrated though Gauss computational calculation between F-carbon surface and organic electrolytes. The optimized F-rich nanoporous carbon manifests a high specific capacitance of 168 F g −1 in a symmetric cell with excellent retention at high rates and upon prolonged 10,000 cycles.

Proton exchange membrane fuel cells have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime. By integrating a thin layer of tungsten oxide within the anode, which serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, we herein report proton exchange membrane fuel cells with significantly enhanced power performance for transient operation and low humidified conditions, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs. Scale fabrication of such devices can be readily achieved based on the current fabrication techniques with negligible extra expense. This work provides proton exchange membrane fuel cells with enhanced power performance, improved durability, prolonged lifetime, and reduced cost for automotive and other applications., Proton exchange membrane fuel cells often suffer from low lifetimes and high cost. Here, the authors enhance the transient power performance and durability of these fuel cells by integrating a thin layer of tungsten oxide within the anode, which acts as a hydrogen reservoir, oxygen scavenger, and a regulator for the hydrogen-disassociation reaction.

A low-cost and scalable method has been developed to synthesize Fe-decorated N-rich carbon electrocatalysts for the oxygen reduction reaction (ORR) based on pyrolysis of metal carbonyls containing metal–organic frameworks (MOFs). Such a method simultaneously optimizes the Fe-related active sites and the porous structure of the catalysts. Accordingly, the best-performing Fe-NC-900-M catalyst shows excellent ORR activity with a half-wave potential of 0.91 V vs. RHE, exceeding that of the 40% Pt/C catalyst in alkaline media. Furthermore, the zinc–air batteries constructed with Fe-NC-900-M as the cathode catalyst exhibit high open-circuit voltage (1.5 V) and peak power density (271 mW cm−2), and outperform most zinc–air batteries with noble-metal free ORR catalysts.

Silicon holds great promise as an anode material for lithium-ion batteries with higher energy density; its implication, however, is limited by rapid capacity fading. A catalytic growth of graphene cages on composite particles of magnesium oxide and silicon, which are made by magnesiothermic reduction reaction of silica particles, is reported herein. Catalyzed by the magnesium oxide, graphene cages can be conformally grown onto the composite particles, leading to the formation of hollow graphene-encapsulated Si particles. Such materials exhibit excellent lithium storage properties in terms of high specific capacity, remarkable rate capability (890 mAh g-1 at 5 A g-1 ), and good cycling retention over 200 cycles with consistently high coulombic efficiency at a current density of 1 A g-1 . A full battery test using LiCoO2 as the cathode demonstrates a high energy density of 329 Wh kg-1 .

Lithium–sulfur (Li–S) batteries have attracted much attention in the field of electrochemical energy storage and conversion. As a vital part of the cathode electrode, the host materials of sulfur usually have a strong impact on the capacity, energy density, cycle life and Coulombic efficiency of Li–S batteries. With their unique physical and chemical properties, the rationally designed hollow nanostructures show conspicuous advantages as sulfur hosts, and have significantly improved the overall performance of Li–S cells. The scope of this review considers the unique structural advantages of hollow host materials for high-performance Li–S batteries, together with a summary of recent advances in the design and synthesis of various hollow micro-/nanostructures with controlled shapes, tailored shell structures and designed chemical compositions. Finally, we propose some emerging requirements of sulfur hosts which we hope will shed some light on the future development trend of hollow structures for advanced Li–S batteries.

Hollow structures of rutile TiO2 , and especially with non-spherical shape, have rarely been reported. Herein, high-quality rutile TiO2 submicroboxes have been synthesized by a facile templating method using Fe2 O3 submicrocubes as removable templates. Compared to other rutile TiO2 nanomaterials, the as-prepared rutile TiO2 submicroboxes manifest superior lithium storage properties in terms of high specific capacity, long-term cycling stability, and excellent rate capability.

Three-dimensional (3D) Pt-based alloy nanostructures composed of one-dimensional (1D) nanowires/nanorods have recently attracted significant interest as electrocatalysts. In this work, we report an effective solvothermal method for the direct preparation of 3D Pt–Co nanowire assemblies (NWAs) with tunable composition. The composition- and structure-dependent electrocatalytic performance is thoroughly investigated. Because of the bimetallic synergetic effect and unique structural advantage, the as-prepared 3D Pt3Co NWA outperforms commercial Pt/carbon and Pt black catalysts and even 3D Pt NWA. The electrochemical results demonstrate that the 3D Pt3Co NWA is indeed a promising electrocatalyst with enhanced catalytic activity and improved durability for practical electrocatalytic applications.

Solid-state electrolytes are the key to the development of lithium-based batteries with dramatically improved energy density and safety. Inspired by ionic channels in biological systems, a novel class of pseudo solid-state electrolytes with biomimetic ionic channels is reported herein. This is achieved by complexing the anions of an electrolyte to the open metal sites of metal-organic frameworks (MOFs), which transforms the MOF scaffolds into ionic-channel analogs with lithium-ion conduction and low activation energy. This work suggests the emergence of a new class of pseudo solid-state lithium-ion conducting electrolytes.

Lithium–sulfur batteries, notable for high theoretical energy density, environmental benignity, and low cost, hold great potential for next-generation energy storage. Polysulfides, the intermediates generated during cycling, may shuttle between electrodes, compromising the energy density and cycling life. We report herein a class of regenerative polysulfide-scavenging layers (RSL), which effectively immobilize and regenerate polysulfides, especially for electrodes with high sulfur loadings (e.g., 6 mg cm–2). The resulting cells exhibit high gravimetric energy density of 365 Wh kg–1, initial areal capacity of 7.94 mAh cm–2, low self-discharge rate of 2.45% after resting for 3 days, and dramatically prolonged cycling life. Such blocking effects have been thoroughly investigated and correlated with the work functions of the oxides as well as their bond energies with polysulfides. This work offers not only a class of RSL to mitigate shuttling effect but also a quantified design framework for advanced lithium–...

Despite the great advantages of hollow structures as electrodes for lithium-ion batteries, one apparent common drawback which is often criticized is their compromised volumetric energy density due to the introduced hollow interior. Here, we design and synthesize bowl-like SnO2 @carbon hollow particles to reduce the excessive hollow interior space while retaining the general advantages of hollow structures. As a result, the tap density can be increased about 30 %. The as-prepared bowl-like SnO2 @carbon hollow particles with conformal carbon support exhibit excellent lithium storage properties in terms of high capacity, stable cyclability and excellent rate capability.

Hierarchical MoS2 microboxes constructed by ultrathin nanosheets are synthesized by a facile template-assisted strategy. The first step involves the L-cysteine assisted uniform growth of hierarchical MoS2 nanosheets on MnCO3 microcube templates which are at the same time converted to MnS. Hierarchical MoS2 microboxes can be obtained by selectively dissolving MnS through acid washing. When evaluated as an anode material for lithium-ion batteries, the hierarchical MoS2 microboxes manifest high specific capacity and excellent cycling performance. The hierarchical MoS2 microboxes also show enhanced electrocatalytic activity for electrochemical hydrogen evolution from water.

Hollow nanostructures are of great interest for a wide variety of applications. Despite the great advances, synthesis of anisotropic hollow structures is still very challenging. In this work, we have developed a simple sacrificial template method to synthesize uniform Ni(x)Co(3-x)S4 hollow nanoprisms with tunable composition. Tetragonal nanoprisms of nickel-cobalt acetate hydroxide precursors with controllable Ni/Co molar ratios are first synthesized and used as the sacrificial templates. After a sulfidation process with thioacetamide (TAA) in ethanol, the solid precursor prisms can be transformed into the corresponding Ni(x)Co(3-x)S4 hollow nanoprisms with a well-defined hollow interior. The intriguing structural and compositional features are beneficial for electrochemical applications. Impressively, the resultant Ni(x)Co(3-x)S4 hollow prisms manifest a high specific capacitance with enhanced cycling stability, making them potential electrode materials for supercapacitors.

CoSe2 is a potential anode material for sodium-ion batteries in terms of their high sodium storage capacity and tunable properties. However, structural degradation and unstable interphase during the reversible sodiation and de-sodiation lead to fast capacity decay. In this work, we develop a nanocomposite architecture based on CoSe2 nanoparticles embedded in N-doped carbon matrix with conformal TiO2 coating (CoSe2@NC@TiO2) by using a metal-organic framework-assisted strategy. The small CoSe2 nanoparticles and N-doped carbon matrix facilitate charge transport and suppress the structural degradation, while the redox-active TiO2 shell further strengthens the structural and interfacial stability without decreasing the capacity. The as-prepared CoSe2@NC@TiO2 nanocomposite particles deliver a reversible sodium storage capacity of 520 mAh g−1 at 0.1 A g−1 with a capacity retention of 78% after 200 cycles, in contrast to the rapid capacity fading after 50 cycles of the pristine CoSe2@NC particles without TiO2 shell.

A facile two-step strategy involving a polyol method and subsequent thermal annealing treatment is successfully developed for the general synthesis of metal oxide/carbon coaxial nanocables. Benefitting from the strong coupling effect, these hybrid nanocables exhibit remarkable lithium storage properties with high capacity, long cycle life and excellent rate capability.

In this work, rattle-type ball-in-ball V2O5 hollow microspheres are controllably synthesized with the assistance of carbon colloidal spheres as hard templates. Carbon spheres@vanadium-precursor (CS@V) core–shell composite microspheres are first prepared through a one-step solvothermal method. The composition of solvent for the solvothermal synthesis has great influence on the morphology and structure of the vanadium-precursor shells. V2O5 hollow microspheres with various shell architectures can be obtained after removing the carbon microspheres by calcination in air. Moreover, the interior hollow shell can be tailored by varying the temperature ramping rate and calcination temperature. The rattle-type V2O5 hollow microspheres are evaluated as a cathode material for lithium-ion batteries, which manifest high specific discharge capacity, good cycling stability and rate capability.

Owing to their unique structural features, hollow micro-/ nanostructures have aroused intense research interest in a wide range of areas such as energy storage, catalysis, chemical sensors, and biomedical applications. [ 1–10 ] The templating method is considered the most representative and straightforward route to fabricate hollow structures with well-defi ned morphologies and high uniformity. [ 11 ] This versatile method generally involves the growth of a shell of designed materials against various templates (e.g., monodisperse colloidal polymer/silica spheres) to form a core–shell structure, and the subsequent removal of the interior materials, which conceptually facilitates the manipulation of the size, shape, and local chemical environment of the resultant hollow structures. [ 2 , 12 , 13 ] Nevertheless, practically, templating methods face quite a few challenges, such as the diffi culty to achieve uniform coating due to compatibility issues between the template and desired shell materials. [ 14 ] Moreover, removal of the interior templates, which is usually through tedious etching/calcination treatments and likely causes collapse and deformation of the exterior shell, holds another key to obtain well-defi ned hollow structures. Very recently, a few works have reported the syntheses of hollow structures by modifi ed templating strategies, which simultaneously realize the functionalization of the exterior shell and the elimination of the internal template. Zhao and coworkers reported the fabrication of Fe 3 O 4 @titanate yolk–shell microspheres from TiO 2 @SiO 2 @ Fe 3 O 4 core–shell structures. [ 15 ] The outmost TiO 2 shell was converted into titanate nanosheets during the removal of the SiO 2 layer through a facile hydrothermal approach in a NaOH solution. Our group has previously reported the synthesis of NiS hollow spheres from SiO 2 @nickel silicate core–shell structures by a one-step hydrothermal reaction in a Na 2 S solution, during which the sulfi dation of nickel silicate and dissolution of silica take place at the same time. [ 16 ] However, such modifi ed templating strategies have not been widely practiced yet. Spinel Li 4 Ti 5 O 12 has been extensively investigated as one of the most promising anode materials for high-rate lithium-ion batteries (LIBs) because of the zero volume change during lithiation and improved safety in operation. [ 17–19 ] Typically, Li 4 Ti 5 O 12 can accommodate three Li + ions during the intercalation process to form Li 7 Ti 5 O 12 , resulting in a theoretical specifi c capacity of 175 mA h g − 1 . [ 18 , 20 ] It has been demonstrated that Li 4 Ti 5 O 12 anodes with high performance can be achieved by proper nanostructuring. [ 19 , 21–25 ] Inspired by the successful use of many

The one-step synthesis method of nitrogen doped microporous carbon monoliths derived from biomass with high-efficiency is developed using a novel ammonia (NH3)-assisted activation process, where NH3 serves as both activating agent and nitrogen source. Both pore forming and nitrogen doping simultaneously proceed during the process, obviously superior to conventional chemical activation. The as-prepared nitrogen-doped active carbons exhibit rich micropores with high surface area and high nitrogen content. Synergetic effects of its high surface area, microporous structure and high nitrogen content, especially rich nitrogen-containing groups for effective CO2 capture (i.e., phenyl amine and pyridine-nitrogen) lead to superior CO2/N2 selectivity up to 82, which is the highest among known nanoporous carbons. In addition, the resulting nitrogen-doped active carbons can be easily regenerated under mild conditions. Considering the outstanding CO2 capture performance, low production cost, simple synthesis procedure and easy scalability, the resulting nitrogen-doped microporous carbon monoliths are promising candidates for selective capture of CO2 in industrial applications.

One-dimensional (1D) hierarchical structures composed of Ni3S2 nanosheets grown on carbon nanotube (CNT) backbone (denoted as CNT@Ni3S2) are fabricated by a rational multi-step transformation route. The first step involves coating the CNT backbone with a layer of silica to form CNT@SiO2, which serves as the substrate for the growth of nickel silicate (NiSilicate) nanosheets in the second step to form CNT@SiO2@NiSilicate core-double shell 1D structures. Finally the as-formed CNT@SiO2@NiSilicate 1D structures are converted into CNT-supported Ni3S2 nanosheets via hydrothermal treatment in the presence of Na2S. Simultaneously the intermediate silica layer is eliminated during the hydrothermal treatment, leading to the formation of CNT@Ni3S2 nanostructures. Because of the unique hybrid nano-architecture, the as-prepared 1D hierarchical structure is shown to exhibit excellent performance in both supercapacitors and photocatalytic H2 production.

Hierarchical three-dimensional (3D) vanadium oxide microstructures, including urchin-like microflowers, nanohorn-structured microspheres, nanosheet-assembled microflowers, and nanosheets bundles, are successfully synthesized by a versatile template-free solvothermal method. It is found that the concentration of the precursor (VOC(2)O(4)) solution has a significant effect on the morphologies of the products. As an example, the time-dependent phase and morphology evolution for the urchin-like vanadium oxide microflowers has been investigated in detail. Urchin-like VO(2) microflowers can be self-assembled within 2 h without using any surfactants. After calcination, the VO(2) microflowers can be easily transformed to urchin-like V(2)O(5) microstructures. The as-obtained V(2)O(5) microflowers are highly porous with a specific surface area of 33.64 m(2) g(-1). When evaluated as a cathode material for lithium-ion batteries, the V(2)O(5) sample delivers very high specific discharge capacity of 267 mA h g(-1) at a current density of 300 mA g(-1). Further, it also exhibits improved cycling stability. The excellent electrochemical performance is attributed to multiple advantageous structural features, including the nanosized building blocks, high porosity, and the 3D hierarchical microstructures.

In this work, we report a facile approach to mass produce carbon-coated MoS2 (C-MoS2) nanorods with high uniformity. The C-MoS2 nanorods are prepared using MoO3 nanorods as the precursor via a sulfidation and subsequent chemical vapor deposition (CVD) of an amorphous carbon layer. When evaluated as an anode material for lithium-ion batteries, the C-MoS2 nanorods exhibit improved reversibility and cycling performance compared with the bare MoS2 nanorods. A high capacity of 621 mA h g−1 can be retained after 80 cycles at a current density of 200 mA g−1. The rate capability of the C-MoS2 nanorods is also improved. The carbon layer is believed to better retain the structure upon prolonged cycling and to improve the conductivity of the material. This simple strategy using gas-phase sulfidation and CVD carbon coating could also be applied to prepare other nanostructured carbon-coated metal sulfides. Keywords: MoS2, Nanorods, Carbon coating, Lithium-ion batteries, Anode

Layered protonated titanates (LPTs), a class of interesting inorganic layered materials, have been widely studied because of their many unique properties and their use as precursors to many important TiO(2)-based functional materials. In this work, we have developed a facile solvothermal method to synthesize hierarchical spheres (HSs) assembled from ultrathin LPT nanosheets. These LPT hierarchical spheres possess a porous structure with a large specific surface area and high stability. Importantly, the size and morphology of the LPT hierarchical spheres are easily tunable by varying the synthesis conditions. These LPT HSs can be easily converted to anatase TiO(2) HSs without significant structural alteration. Depending on the calcination atmosphere of air or N(2), pure anatase TiO(2) HSs or carbon-supported TiO(2) HSs, respectively, can be obtained. Remarkably, both types of TiO(2) HSs manifest excellent cyclability and rate capability when evaluated as anode materials for high-power lithium-ion batteries.

In this work, we have developed a facile hydrothermal method to synthesize various 3D hierarchical structures assembled from 2D SnO2 nanosheets. The samples were thoroughly characterized by FESEM/TEM/XRD/BET techniques. Through in-depth investigation of experimental conditions, it is discovered that the oxidation process is crucial for the formation of the nanosheet structure. The electrochemical properties of the sample were subsequently studied by cyclic voltammetry and charge–discharge cycling. When compared to SnO2 nanoparticles from a commercial source, the result shows that the as-prepared hierarchical SnO2 nanostructure exhibits much better lithium storage properties with higher reversible capacities and improved cyclic capacity retention for extended cycling.

A facile one-pot hydrothermal method has been developed for the preparation of carbon-coated MoO(2) nanocrystals. The annealed MoO(2)-C nanocomposite consists of interconnected MoO(2)@C nanocrystals. When evaluated for lithium storage capabilities, these MoO(2)@C nanocrystals exhibit high specific capacities (~640 mA h g(-1) at 200 mA g(-1) and ~575 mA h g(-1) at 400 mA g(-1)) and excellent cycling stability. In view of the excellent lithium storage properties and the ease in large-scale preparation, the as-synthesized MoO(2)-C nanocomposite might be used as promising anode materials for high-performance lithium-ion batteries.

Production of hydrogen by electrochemical water splitting has been hindered by the high cost of precious metal catalysts, such as Pt, for the hydrogen evolution reaction (HER). In this work, novel hierarchical β-Mo2 C nanotubes constructed from porous nanosheets have been fabricated and investigated as a high-performance and low-cost electrocatalyst for HER. An unusual template-engaged strategy has been utilized to controllably synthesize Mo-polydopamine nanotubes, which are further converted into hierarchical β-Mo2 C nanotubes by direct carburization at high temperature. Benefitting from several structural advantages including ultrafine primary nanocrystallites, large exposed surface, fast charge transfer, and unique tubular structure, the as-prepared hierarchical β-Mo2 C nanotubes exhibit excellent electrocatalytic performance for HER with small overpotential in both acidic and basic conditions, as well as remarkable stability.

Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts., There is extensive research into non-platinum electrocatalysts for hydrogen evolution. Here, the authors report a molybdenum carbide catalyst, prepared via the carburization of a copper metal-organic framework host/molybdenum-based polyoxometalates guest system, and demonstrate its catalytic activity.

Titanium niobium oxide (TiNb2O7) has been recognized as a promising anode material for lithium-ion batteries (LIBs) in view of its potential to operate at high rates with improved safety and high theoretical capacity of 387 mAh g−1. However, it suffers from poor Li+ ion diffusivity and low electronic conductivity originated from its wide band gap energy (Eg > 2 eV). Here, porous TiNb2O7 microspheres (PTNO MSs) are prepared via a facile solvothermal reaction. PTNO MSs have a particle size of ≈1.2 μm and controllable pore sizes in the range of 5–35 nm. Ammonia gas nitridation treatment is conducted on PTNO MSs to introduce conducting Ti1−xNbxN layer on the surface and form nitridated PTNO (NPTNO) MSs. The porous structure and conducting Ti1−xNbxN layer enhance the transport kinetics associated with Li+ ions and electrons, which leads to significant improvement in electrochemical performance. As a result, the NPTNO electrode shows a high discharge capacity of ≈265 mAh g−1, remarkable rate capability (≈143 mAh g−1 at 100 C) and durable long-term cyclability (≈91% capacity retention over 1000 cycles at 5 C). These results demonstrate the great potential of TiNb2O7 as a practical high-rate anode material for LIBs.

Hierarchical Fe3 O4 hollow spheres constructed by nanosheets are obtained from solvothermally synthesized Fe-glycerate hollow spheres. With the unique structural features, these hierarchical Fe3 O4 hollow spheres exhibit excellent electrochemical lithium-storage performance.

Iron–nitrogen–carbon (Fe–N–C) catalysts are considered as the most promising nonprecious metal catalysts for oxygen reduction reactions (ORRs). Their synthesis generally involves complex pyrolysis reactions at high temperature, making it difficult to optimize their composition, pore structure, and active sites. This study reports a simple synthesis strategy by reacting preformed nitrogen-doped carbon scaffolds with iron pentacarbonyl, a liquid precursor that can effectively form active sites with the nitrogen sites, enabling more effective control of the catalyst. The resultant catalyst possesses a well-defined mesoporous structure, a high surface area, and optimized active sites. The catalysts exhibit high ORR activity comparable to that of Pt/C catalyst (40% Pt loading) in alkaline media, with excellent stability and methanol tolerance. The synthetic strategy can be extended to synthesize other metal–N–C catalysts.

While the synthesis of hollow structures of transition metal oxides is well established, it is extremely challenging to fabricate complex hollow structures for mixed transition metal sulfides. Here we report an anion exchange method to synthesize a complex ternary metal sulfides hollow structure, namely nickel cobalt sulfide ball-in-ball hollow spheres. Uniform nickel cobalt glycerate solid spheres are first synthesized as the precursor and subsequently chemically transformed into nickel cobalt sulfide ball-in-ball hollow spheres. When used as electrode materials for electrochemical capacitors, these nickel cobalt sulfide hollow spheres deliver a specific capacitance of 1,036 F g(-1) at a current density of 1.0 A g(-1). An asymmetric supercapacitor based on these ball-in-ball structures shows long-term cycling performance with a high energy density of 42.3 Wh kg(-1) at a power density of 476 W kg(-1), suggesting their potential application in high-performance electrochemical capacitors.

While the synthesis of TiO2 hollow structures is well-established, in most cases it is particularly difficult to control the crystallization of TiO2 in solution or by calcination. As a result, TiO2 hollow structures do not really exhibit enhanced lithium storage properties. Herein, we report a simple and cost-effective template-assisted method to synthesize anatase TiO2 hollow spheres composed of highly crystalline nanocrystals, in which carbonaceous (C) spheres are chosen as the removable template. The release of gaseous species from the combustion of C spheres may inhibit the growth of TiO2 crystallites so that instead small TiO2 nanocrystals are generated. The small size and high crystallinity of primary TiO2 nanoparticles and the high structural integrity of the hollow spheres gives rise to significant improvements in the cycling stability and rate performance of the TiO2 hollow spheres.

Pt nanocubes/rGO in one pot: Pt nanocubes/rGO hybrids are successfully ­synthesized via a facile one-pot approach. The resultant Pt nanocubes/rGO hybrid exhibits enhanced catalytic activity and excellent electrochemical stability in comparison with commercial Pt/CB electrocatalysts, which can be ascribed to the abundant Pt(100) ­surface and its uniform distribution on rGO.

Carbon-coated NiCo2 O4 @SnO2 core-shell hetero-nanostructures are synthesized by a facile hydrothermal process and subsequent carbon nano-coating. When evaluated as anode materials for lithium-ion batteries, the 3D hetero-nanostructures exhibit enhanced lithium storage properties due to advantageous structural features.

Deeply excavated: Platinum nanoframes with highly concave {740} facets are synthesized directly by a facile oleylamine-assisted solvothermal method. Because of the unique structure and exposed high-index facets, the as-prepared Pt nanoframes exhibit very high electrocatalytic activity and remarkable stability for the oxygen reduction reaction and the oxidation of methanol and formic acid.

As a promising rechargeable battery system, lithium– sulfur (Li–S) batteries can deliver an exceptionally high theoretical specific capacity of 1672 mAhg 1 and an energy density of 2500 Whkg 1 with the low-cost and environmentfriendly sulfur as the cathode material. Although the potential use of sulfur as a cathode material has long been discovered, several severe drawbacks have hindered the realization of Li–S batteries. One limitation is the insulating nature of sulfur with a very low conductivity of 5 10 30 Scm , which results in low utilization of sulfur. Another well-known problem is associated with the easy dissolution of polysulfides, the intermediate products formed during the electrochemical reaction, in organic electrolytes. The dissolved polysulfides “shuttle” between the electrodes, leading to the low Coulombic efficiency and deposition of a highly resistive layer on the surface of electrodes. These detrimental issues result in unsatisfactory electrochemical performance with rapid fading of capacity. Several approaches have been proposed to overcome the above-mentioned challenges in Li–S batteries, such as developing novel electrolytes and electrode materials. Among these efforts, using sulfur-containing composites instead of pure sulfur as the cathode materials has been demonstrated as an effective way towards high-performance Li–S batteries. Polymers and porous carbons are the common candidates to form composites with sulfur, which immobilize the loaded sulfur, and probably also the derived polysulfides via physical and/or chemical interactions. In addition, the electrical conductivity of composite materials is also better than that obtained with pristine sulfur. In particular, porous carbon materials have attracted intensive attention due to their good compatibility with sulfur, easy accessibility, and the abundance of candidates with diverse porosity and structures. Mesoporous carbon materials have been widely studied as the host materials to confine sulfur. For example, nanocomposites consisting of sulfur and ordered mesoporous carbon or mesoporous hollow carbon spheres have shown improved sulfur utilization and cycling stability. Nonetheless, continuous capacity fading upon prolonged cycling is still commonly observed, and the use of optimized ether-based electrolytes seems to be indispensable. Recent reports on carbon materials with rich micropores have revealed distinct characteristics. 25] Sulfur embedded in microporous carbon shows a pronounced discharge plateau at a lower potential of about 1.8 V versus Li/Li, which is different from the two plateaus of a typical sulfur cathode. More importantly, these microporous carbon/sulfur nanocomposites generally show outstanding capacity retention upon cycling and good compatibility with conventional carbonate-based electrolytes. However, the origins of the unusual characteristics of microporous carbon are not fully understood yet. In recently years, syntheses of porous carbon materials from metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) have attracted growing attention due to the facile preparation procedures, high carbon yield, and unique porous structures. For example, carbonization of MOF-5 with furfuryl alcohol results in nanoporous carbon, which shows excellent supercapacitive performance. The carbon materials with fiber-like morphology prepared from Al-based PCPs exhibit remarkably high porosity. In particular, MOFs and PCPs are very attractive as both the template and the precursor for the fabrication of microporous carbon. Compared with many other highly porous carbon materials, such as those prepared by post-activation processes, the porous carbon derived from MOFs and PCPs exhibits highly uniform porosity, largely originating from the ordered crystalline structures of the MOFs and PCPs. However, the interesting application of these carbon materials derived from MOFs and PCPs for Li–S batteries needs to be further explored. Herein, we report the facile synthesis of microporous carbon polyhedrons (MPCPs) using unique MOF polyhedrons as both the template and precursor, and their use as carbon host to incorporate sulfur for Li–S batteries. The asprepared MPCPs with abundant and uniform micropores serve as an ideal model system for investigating the electrochemical behaviors of sulfur embedded in microporous [a] H. B. Wu, S. Wei, Dr. L. Zhang, Prof. R. Xu, Prof. X. W. Lou School of Chemical and Biomedical Engineering Nanyang Technological University 62 Nanyang Drive, Singapore 637459 (Singapore) E-mail : rxu@ntu.edu.sg xwlou@ntu.edu.sg Homepage: http://www.ntu.edu.sg/home/xwlou [b] H. B. Wu, Prof. H. H. Hng School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue, Singapore 639798 (Singapore) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201301689.