Rationally Designed Three-Layered Cu2 S@Carbon@MoS2 Hierarchical Nanoboxes for Efficient Sodium Storage

3D Fast Sodium Transport Network of MoS2 Endowed by Coupling of Sulfur Vacancies and Sn Doping for Outstanding Sodium Storage

A sulfur vacancy-rich, Sn-doped as well as carbon-coated MoS2 composite (Vs-SMS@C) is rationally synthesized via a simple hydrothermal method combined with ball-milling reduction, which enhances the sodium storage performance. Benefiting from the 3D fast Na+ transport network composed of the defective carbon coating, Mo─S─C bonds, enlarged interlayer spacing, S-vacancies, and lattice distortion in the composite, the Na+ storage kinetics is significantly accelerated. As expected, Vs-SMS@C releases an ultrahigh reversible capacity of 1089 mAh g-1 at 0.1 A g-1, higher than the theoretical capacity. It delivers a satisfactory capacity of 463 mAh g-1 at a high current density of 10 A g-1, which is the state-of-the-art rate capability compared to other MoS2 based sodium ion battery anodes to the knowledge. Moreover, a super long-term cycle stability is achieved by Vs-SMS@C, which keeps 91.6% of the initial capacity after 3000 cycles under the current density of 5 A g-1 in the voltage of 0.3-3.0 V. The sodium storage mechanism of Vs-SMS@C is investigated by employing electrochemical methods and ex situ techniques. The synergistic effect between S-vacancies and doped-Sn is evidenced by DFT calculations. This work opens new ideas for seeking excellent metal sulfide anodes.

MoS2 Hollow Multishelled Nanospheres Doped Fe Single Atoms Capable of Fast Phase Transformation for Fast-charging Na-ion Batteries

Low Na+ and electron diffusion kinetics severely restrain the rate capability of MoS2 as anode for sodium-ion batteries (SIBs). Slow phase transitions between 2H and 1T, and from NaxMoS2 to Mo and Na2S as well as the volume change during cycling, induce a poor cycling stability. Herein, an original Fe single atom doped MoS2 hollow multishelled structure (HoMS) is designed for the first time to address the above challenges. The Fe single atom in MoS2 promotes the electron transfer, companying with shortened charge diffusion path from unique HoMS, thereby achieving excellent rate capability. The strong adsorption with Na+ and self-catalysis of Fe single atom facilitates the reversible conversion between 2H and 1T, and from NaxMoS2 to Mo and Na2S. Moreover, the buffering effect of HoMS on volume change during cycling improves the cyclic stability. Consequently, the Fe single atom doped MoS2 quadruple-shelled sphere exhibits a high specific capacity of 213.3 mAh g-1 at an ultrahigh current density of 30 A g-1, which is superior to previously-reported results. Even at 5 A g-1, 259.4 mAh g-1 (83.68 %) was reserved after 500 cycles. Such elaborate catalytic site decorated HoMS is also promising to realize other "fast-charging" high-energy-density rechargeable batteries.

Electron Configuration Modulation Induced Stabilized 1T-MoS2 for Enhanced Sodium Ion Storage

1T-MoS2 has become an ideal anode for sodium-ion batteries (SIBs). However, the metastable feature of 1T-MoS2 makes it difficult to directly synthesize under normal conditions. In addition, it easily transforms into 2H phase via restacking, resulting in inferior electrochemical performance. Herein, the electron configuration of Mo 4d orbitals is modulated and the stable 1T-MoS2 is constructed by nickel (Ni) introduction (1T-Ni-MoS2). The original electron configuration of Mo 4d orbitals is changed via the electron injection by Ni, which triggers the phase transition from 2H to 1T phase, thus improving the electrical conductivity and accelerating the redox kinetics of the material. Consequently, 1T-Ni-MoS2 exhibits superior rate capability (266.8 mAh g-1 at 10 A g-1) and excellent cycle life (358.7 mAh g-1 at 1 A g-1 after 350 cycles). In addition, the assembled Na3V2(PO4)3/C||1T-Ni-MoS2 full cells deliver excellent electrochemical properties and show great prospects in energy storage devices.

Pioneering Piezoelectric-Driven Atomic Hydrogen for Efficient Dehalogenation of Halogenated Organic Pollutants

The electrocatalytic hydrodehalogenation (EHDH) process mediated by atomic hydrogen (H*) is recognized as an efficient method for degrading halogenated organic pollutants (HOPs). However, a significant challenge is the excessive energy consumption resulting from the recombination of H* to H2 production in the EHDH process. In this study, a promising strategy was proposed to generate piezo-induced atomic H*, without external energy input or chemical consumption, for the degradation and dehalogenation of HOPs. Specifically, sub-5 nm Ni nanoparticles were subtly dotted on an N-doped carbon layer coating on BaTiO3 cube, and the resulted hybrid nanocomposite (Ni-NC@BTO) can effectively break C-X (X = Cl and F) bonds under ultrasonic vibration or mechanical stirring, demonstrating high piezoelectric driven dehalogenation efficiencies toward various HOPs. Mechanistic studies revealed that the dotted Ni nanoparticles can efficiently capture H* to form Ni-H* (Habs) and drive the dehalogenation process to lower the toxicity of intermediates. COMSOL simulations confirmed a "chimney effect" on the interface of Ni nanoparticle, which facilitated the accumulation of H+ and enhanced electron transfer for H* formation by improving the surface charge of the piezocatalyst and strengthening the interfacial electric field. Our work introduces an environmentally friendly dehalogenation method for HOPs using the piezoelectric process independent of the external energy input and chemical consumption.

Buffer solution induced highly crystalline sodium-rich Prussian blue for sodium storage

In this work, we have developed an efficient method to synthesize Prussian blue by self-decomposition of sodium ferrocyanide in acetic acid-sodium acetate buffer solution. This buffer solution-based proton pool provides a relatively low and stable concentration of protons for the slow decomposition of sodium ferrocyanide to get highly crystalline and sodium rich Prussian blue, which can be used as the cathode for high-performance sodium-ion batteries.

Synthesis and Electrocatalytic Applications of Layer-Structured Metal Chalcogenides Composites

Featured with the attractive properties such as large surface area, unique atomic layer thickness, excellent electronic conductivity, and superior catalytic activity, layered metal chalcogenides (LMCs) have received considerable research attention in electrocatalytic applications. In this review, the approaches developed to synthesize LMCs-based electrocatalysts are summarized. Recent progress in LMCs-based composites for electrochemical energy conversion applications including oxygen reduction reaction, carbon dioxide reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, overall water splitting, and nitrogen reduction reaction is reviewed, and the potential opportunities and practical obstacles for the development of LMCs-based composites as high-performing active substances for electrocatalytic applications are also discussed. This review may provide an inspiring guidance for developing high-performance LMCs for electrochemical energy conversion applications.

ZnSe/SnSe Heterostructure Incorporated with Selenium/Nitrogen Co-Doped Carbon Nanofiber Skeleton for Sodium-Ion Batteries

Effective strategies toward building exquisite nanostructures with enhanced structural integrity and improved reaction kinetics will carry forward the practical application of alloy-based materials as anodes in batteries. Herein, a free-standing 3D carbon nanofiber (CNF) skeleton incorporated with heterostructured binary metal selenides (ZnSe/SnSe) nanoboxes is developed for Na-ion storage anodes, which can facilitate Na+ ion migration, improve structure integrity, and enhance the electrochemical reaction kinetics. During the carbonization and selenization process, selenium/nitrogen (Se/N) is co-doped into the 3D CNF skeleton, which can improve the conductivity and wettability of the CNF matrices. More importantly, the ZnSe/SnSe heterostructures and the Se/N co-doping CNFs can have a synergistic interfacial coupling effect and built-in electric field in the heterogeneous interfaces of ZnSe/SnSe hetero-boundaries as well as the interfaces between the CNF matrix and the selenide heterostructures, which can enable fast ion/electron transport and accelerate surface/internal reaction kinetics for Na-ion storage. The ZnSe/SnSe@Se,N-CNFs exhibit superior Na-ion storage performance than the comparative ZnSe/SnSe, ZnSe and SnSe powders, which deliver an excellent rate performance (882.0, 773.6, 695.7, 634.2, and 559.0 mAh g-1 at current rates of 0.1, 0.2, 0.5, 1, and 2 A g-1 ) and long-life cycling stability of 587.5 mAh g-1 for 3500 cycles at 2 A g-1 .

Synergetic Sn Incorporation-Zn Substitution in Copper-Based Sulfides Enabling Superior Na-Ion Storage

Transition-metal sulfides have been regarded as perspective anode candidates for high-energy Na-ion batteries. Their application, however, is precluded severely by either low charge storage or huge volumetric change along with sluggish reaction kinetics. Herein, an effective synergetic Sn incorporation-Zn substitution strategy is proposed based on copper-based sulfides. First, Na-ion storage capability of copper sulfide is significantly improved via incorporating an alloy-based Sn element. However, this process is accompanied by sacrifice of structural stability due to the high Na-ion uptake. Subsequently, to maintain the high Na-ion storage capacity, and concurrently improve cycling and rate capabilities, a Zn substitution strategy (taking partial Sn sites) is carried out, which could significantly promote Na-ion diffusion/reaction kinetics and relieve mechanical strain-stress within the crystal framework. The synergetic Sn incorporation and Zn substitution endow copper-based sulfides with high specific capacity (≈560 mAh g-1 at 0.5 A g-1 ), ultrastable cyclability (80 k cycles with ≈100% capacity retention), superior rate capability up to 200 A g-1 , and ultrafast charging feature (≈4 s per charging with ≈190 mAh g-1 input). This work provides in-depth insights for developing superior anode materials via synergetic multi-cation incorporation/substitution, aiming at solving their intrinsic issues of either low specific capacity or poor cyclability.

Hollow Plasmonic P-Metal-N S-Scheme Heterojunction Photoreactor with Spatially Separated Dual Cocatalysts toward Artificial Photosynthesis

Semiconductor-based step-scheme (S-scheme) heterojunctions possess many merits toward mimicking natural photosynthesis. However, their applications for solar-to-chemical energy conversion are hindered by inefficient charge utilization and unsatisfactory surface reactivity. Herein, two synergistic protocols are demonstrated to overcome these limitations based on the construction of a hollow plasmonic p-metal-n S-scheme heterojunction photoreactor with spatially separated dual noble-metal-free cocatalysts. On one side, plasmonic Au, inserted into the heterointerfaces of CuS@ZnIn2 S4 core-shell nanoboxes, not only accelerates the transfer and recombination of useless charges, enabling a more thorough separation of useful ones for CO2 reduction and H2 O oxidation but also generates hot electrons and holes, respectively injects them into ZnIn2 S4 and CuS, further increasing the number of active carriers participating in redox reactions. On the other side, Fe(OH)x and Ti3 C2 cocatalysts, separately located on the CuS and ZnIn2 S4 surface, enrich the redox sites, adjust the reduction potential and pathway for selective CO2 -to-CH4 transformation, and balance the transfer and consumption of photocarriers. As expected, significantly enhanced activity and selectivity in CH4 production are achieved by the smart design along with nearly stoichiometric ratios of reduction and oxidation products. This study paves the way for optimizing artificial photosynthetic systems via rational interfacial channel introduction and surface cocatalyst modification.

Cobalt Oxide 2D Nanosheets Formed at a Polarized Liquid|Liquid Interface toward High-Performance Li-Ion and Na-Ion Battery Anodes

Cobalt oxide (Co3O4)-based nanostructures have the potential as low-cost materials for lithium-ion (Li-ion) and sodium-ion (Na-ion) battery anodes with a theoretical capacity of 890 mAh/g. Here, we demonstrate a novel method for the production of Co3O4 nanoplatelets. This involves the growth of flower-like cobalt oxyhydroxide (CoOOH) nanostructures at a polarized liquid|liquid interface, followed by conversion to flower-like Co3O4 via calcination. Finally, sonication is used to break up the flower-like Co3O4 nanostructures into two-dimensional (2D) nanoplatelets with lateral sizes of 20-100 nm. Nanoplatelets of Co3O4 can be easily mixed with carbon nanotubes to create nanocomposite anodes, which can be used for Li-ion and Na-ion battery anodes without any additional binder or conductive additive. The resultant electrodes display impressive low-rate capacities (at 125 mA/g) of 1108 and 1083 mAh/g, for Li-ion and Na-ion anodes, respectively, and stable cycling ability over >200 cycles. Detailed quantitative rate analysis clearly shows that Li-ion-storing anodes charge roughly five times faster than Na-ion-storing anodes.

A metal organic framework-derived octahedral Cu1.95S@CoS2 for secondary batteries displaying long cycle life and stable temperature tolerance

Low-cost and safe batteries are considered to be promising energy-storage systems. Here, a metal organic framework (MOF)-derived octahedral Cu1.95S@CoS2 composite is developed as a high-performance cathode of aluminium-ion (Al-ion) batteries. CoS2 nanoparticles on Cu1.95S provide active sites, making AlCl4- intercalation/deintercalation highly reversible, and reducing polarization. Cycling at 0.5 A g-1, Cu1.95S@CoS2 maintains stable capacities of 136.6 and 122.4 mA h g-1 after 200 cycles at room temperature and -10 °C, respectively. Stable rate-performance is also achieved. These findings will accelerate the application of Al-ion batteries and MOF-derived energy-storage composites.

Fabrication of NiMn2O4/C hollow spheres with a trilaminar shell structure as an anode material for sodium-ion batteries

NiMn2O4/C hollow spheres with sandwich-structured shells were fabricated by a hydrothermal method. Leveraging the mesoporous design of the carbon hollow spheres, NiMn2O4 nanosheets were evenly dispersed on both the inner and outer surfaces of the carbon shells. NiMn2O4/C demonstrated excellent rate capability and prolonged cycling durability for sodium ion storage.

3D flower-like hollow MXene@MoS2 heterostructure for fast sodium storage

Constructing an anode with fast electron transport and high cycling stability is important but challenging for large-scale applications of sodium-ion batteries (SIB). In this study, hierarchical flower-like MXene structures were synthesized using poly (methyl methacrylate) (PMMA) microsphere as templates. Subsequently, a straightforward hydrothermal reaction was utilized to anchor small-sized MoS2 nanosheets. The resulting MXene@MoS2 heterostructure exhibits a distinctive three-dimensional (3D) porous hollow architecture. This structure effectively addresses challenges related to self-aggregation of MoS2 nanosheets and volume expansion of the electrode material during Na+ insertion/extraction processes. Furthermore, the robust hetero-interface supports fast and stable electron transfer, thereby enhancing electrochemical reaction kinetics. The prepared MXene@MoS2 electrode demonstrates the specific capacity of 682.1 mA h g-1 at 0.2 A/g and the reversible capacity of 494.4 mA h g-1 after 1000 cycles at 5 A/g. It is noteworthy that the full battery assembled with the composite material as the anode can still maintain the capacity of 456.2 mA h g-1 after 80 cycles at 0.5 A/g. This outstanding reversible capacity and sustained stability over numerous cycles highlights its potential for a wide range of applications.

Ni-derived electronic/ionic engineering on NiSe/Ni@C for ultrafast and stable sodium storage

Atomic-level structure engineering has proven indispensable for fast ion transport kinetics. Herein, a unique framework of NiSe/Ni heterostructure with abundant heterointerface encapsulated hollow carbon spheres, namely NiSe/Ni@C, is synthesized as an anode for SIBs. The NiSe/Ni@C electrode delivers enhanced Na+ storage performance in terms of high specific capacity (490 mA h g-1) and excellent rate capability (546 mA h g-1) at a current of 5.0 A g-1 over 2000 cycles. This study can provide in-depth insights into the interface effect in hybrid structures and shed light on designing energy storage materials.

Nanozyme-assisted ratiometric photoelectrochemical aptasensor over Cu2O nanocubes mediated photocurrent-polarity-switching based on S-scheme FeCdS@FeIn2S4 heterostructure

The controllable modulation of the response mode is highly attractive for the construction of photoelectrochemical (PEC) sensors with improved sensitivity and anti-interference ability in complex real samples matrix. Here, we present a charming proof-of-concept ratiometric PEC aptasensor of enrofloxacin (ENR) analysis via the controllable signal transduction. Different with the traditional sensing mechanism, this ratiometric PEC aptasensor integrates the anodic PEC signal induced by PtCuCo nanozyme-catalyzed precipitation reaction and the polarity-switching cathodic PEC response mediated by Cu2O nanocubes on S-scheme FeCdS@FeIn2S4 heterostructure. Taking advantages of the photocurrent-polarity-switching signal response model and the superior performance of the photoactive substrate material, the proposed ratiometric PEC aptasensor displays a good detection linear range for ENR analysis from 0.01 pg mL-1 to 10 ng mL-1, with a detection limit of 3.3 fg mL-1. This study provides a general platform for detecting interested trace analytes in real samples and expands the diversity of sensing strategy design.

Design of High-Capacity MoS3 Decorated Nitrogen Doped Carbon Coated Cu2 S Electrode Structures with Dual Heterogenous Interfaces for Outstanding Sodium-Ion Storage

The hierarchical Cu2 S@NC@MoS3 heterostructures have been firstly constructed by the high-capacity MoS3 and high-conductive N-doped carbon to co-decorate the Cu2 S hollow nanospheres. During the heterostructure, the middle N-doped carbon layer as the linker facilitates the uniform deposition of MoS3 and enhances the structural stability and electronic conductivity. The popular hollow/porous structures largely restrain the big volume changes of active materials. Due to the cooperative effect of three components, the new Cu2 S@NC@MoS3 heterostructures with dual heterogenous interfaces and small voltage hysteresis for sodium ion storage display a high charge capacity (545 mAh g-1 for 200 cycles at 0.5 A g-1 ), excellent rate capability (424 mAh g-1 at 15 A g-1 ) and ultra-long cyclic life (491 mAh g-1 for 2000 cycles at 3 A g-1 ). Except for the performance test, the reaction mechanism, kinetics analysis, and theoretical calculation have been performed to explain the reason of excellent electrochemical performance of Cu2 S@NC@MoS3 . The rich active sites and rapid Na+ diffusion kinetics of this ternary heterostructure is beneficial to the high efficient sodium storage. The assembled full cell matched with Na3 V2 (PO4 )3 @rGO cathode likewise displays remarkable electrochemical properties. The outstanding sodium storage performances of Cu2 S@NC@MoS3 heterostructures indicate the potential applications in energy storage fields.

Hybrid CuSn nanosphere-functionalized Cu/Sn co-doped hollow carbon nanofibers as anode materials for sodium-ion batteries

To strengthen the electrochemical performance of anode materials for sodium-ion batteries, Cu/Sn co-doped hollow carbon nanofibers functionalized by hybrid CuSn nanospheres (CuSn/C@MCNF) were prepared by a simple electrospinning method. The microstructural characteristics of CuSn/C@MCNF confirmed the same doped elements and strong interactions in hybrid CuSn nanospheres and the hollow carbon nanofiber substrate. CuSn/C@MCNF has superior specific capacity, excellent conductivity and high cycling stability. In particular, the doped hollow carbon nanofiber substrate can facilitate Na+ transport and alleviate volume expansion during the process of sodium storage. When applied as an anode material for sodium-ion batteries, CuSn/C@MCNF can deliver a reversible capacity of 340.1 mA h g-1 at a large current density of 1 A g-1 for 1000 cycles and a high-rate capacity of 202.5 mA h g-1 at 4.0 A g-1, all superior to the corresponding Sn-SnOx@MCNF- and MCNF-based electrodes. This work provides a basic idea for future anode materials in high-performance sodium-ion batteries.

Polysulfide induced synthesis of a MoS2 self-supporting electrode with wide-layer-spacing for efficient electrocatalytic water splitting

Efficient non-noble metal bifunctional electrocatalysts can increase the conversion rate of electric energy in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, a ball & sheet MoS2/Ni3S2 composite with wide-layer-spacing and high 1T-rich MoS2 is assembled on nickel foam (NF) via a two-step solvothermal method with polymeric sulfur (S-r-DIB) as the sulfur source. The obtained material serves as both the cathode and the anode toward overall water splitting in an alkaline electrolyte. The results proved that the interpenetration of MoS2/Ni3S2-p with a ball and sheet structure increased the material active surface area and exposed more catalytic active sites, which contributed to the penetration of solution and the transfer of charge/hydrion. Meanwhile, two different semiconductors of MoS2 and Ni3S2 along with the presence of ample active sulfur edge sites and few-layer, wide-layer-spacing structures of MoS2 lead to an outstanding electrocatalytic activity. In particular, the electrodes of MoS2/Ni3S2-p only need a battery voltage of 1.55 V at 10 mA cm-2. The bifunctional electrocatalyst MoS2/Ni3S2-p also shows excellent stability at large current densities during the electrochemical test.

3D Porous Oxygen-Doped and Nitrogen-Doped Graphitic Carbons Derived from Metal Azolate Frameworks as Cathode and Anode Materials for High-Performance Dual-Carbon Sodium-Ion Hybrid Capacitors

Sodium-ion hybrid capacitors (SIHCs) in principle can utilize the advantages of batteries and supercapacitors and satisfy the cost demand of large-scale energy storage systems, but the sluggish kinetics and low capacities of its anode and cathode are yet to be overcome. Here, a strategy is reported to realize high-performance dual-carbon SIHCs using 3D porous graphitic carbon cathode and anode materials derived from metal-azolate framework-6s (MAF-6s). First, MAF-6s, with or without urea loading, are pyrolyzed to synthesize MAF-derived carbons (MDCs). Then, cathode materials are synthesized via the controlled KOH-assisted pyrolysis of MDCs (K-MDCs). K-MDCs, 3D graphitic carbons, resulting in a record-high surface area (5214 m2  g-1 ) being ≈four-fold higher than pristine MAF-6, oxygen-doped sites for high capacity, rich mesopores affording fast ion transport, and high capacity retention over 5000 charge/discharge cycles. Moreover, 3D porous MDC anode materials are synthesized from N-containing MAF-6 and exhibited to allow cycle stability over 5000 cycles. Furthermore, dual-carbon MDC//K-MDC SIHCs with different loadings (3 to 6 mg cm-2 ) are demonstrated to achieve high energy densities exceeding those of sodium-ion batteries and supercapacitors. Additionally, it allows an ultrafast-chargeable high power density of 20000 W kg-1 and robust cycle stability overcoming those of a typical battery.

Shape-controlled hollow Cu2O@CuS nanocubes with enhanced photocatalytic activities towards degradation of tetracycline

In view of recent advances in photodegradation of antibiotics, low cost and stable photocatalyst remain rare. In this article, shape-controlled Cu2O@CuS nanocubes with the larger specific surface area were successfully prepared via a simple template-engaged strategy. Cu2O nanocubes were synthesized through a reduction method as original templates, the core-shelled Cu2O@CuS nanocubes were formed by sulphuration with Na2S as sulphur source, and the Cu2O core can be incompletely removed by Na2S2O3 to generate the Cu2O@CuS nanoboxes. Herein, hierarchical nanoboxes with two-layered Cu2O@CuS were used as photocatalyst materials for photocatalytic degradation of tetracycline (TC). The obtained nanocubes manifested high specific surface area (39.65 m2 g-1) and large pore volume (12.3 cm3 g-1). The degradation performance for TC was investigated in detail, including the effect of parameters such as photocatalyst, pH and catalyst dosage. The results indicated that degradation efficiencies were higher than 90% under visible light. Moreover, the degradation efficiency was 71% after six times.

Preparation of Cu7.2S4@N, S co-doped carbon honeycomb-like composite structure for high-rate and high-stability sodium-ion storage

Sodium ion batteries (SIBs) attract most of the attention as alterative secondary battery systems for future large-scale energy storage and power batteries due to abundance resource and low cost. However, the lack of anode materials with high-rate performance and high cycling-stability has limited the commercial application of SIBs. In this paper, Cu_7.2S₄@N, S co-doped carbon (Cu_7.2S₄@NSC) honeycomb-like composite structure was designed and prepared by a one-step high-temperature chemical blowing process. As an anode material for SIBs, Cu_7.2S₄@NSC electrode exhibited an ultra-high initial Coulomb efficiency (94.9%) and an excellent electrochemical property including a high reversible capacity of 441.3 mAh g^-1 after 100 cycles at 0.2 A g^-1, an excellent rate performance of 380.4 mAh g^-1 even at 5 A g^-1, and a superior long-cycle stability with a capacity retention rate of approximately 100% after 700 cycles at 1A g^-1.

Dual Mechanism for Sodium based Energy Storage

A dual-mechanism energy storage strategy is proposed, involving the electrochemical process of sodium ion battery (SIB) and sodium metal battery (SMB). This strategy is expected to achieve a higher capacity than SIB, and obtain dendrite-free growth of SMB with a well-designed anode. Here, self-constructed bismuth with "sodiophilic" framework and rapid ion transmission characteristics is employed as the sodium host (anode) integrating alloy/de-alloy and plating/stripping process that suppresses the dendrite growth and overcomes the limited capacity of traditional anode. Benefited from this, the capacity (capacity contributed by alloy and plating of sodium in total) of 2000 mAh g^-1 can be reached, which can retain up to 800 h at 1 A g^-1 . Also, the capacity of 3100 mAh g^-1 can be achieved that is ≈7.7 times than that of alloyed-bismuth (Bi). This work proposes a dual-mechanism strategy to tackle the dilemma of high-performance sodium (Na) storage devices, which opens a new avenue for the development of next-generation energy storage device.

Synergistically Designed Dual Interfaces to Enhance the Electrochemical Performance of MoO2 /MoS2 in Na- and Li-Ion Batteries

It is indispensable to develop and design high capacity, high rate performance, long cycling life, and low-cost electrodes materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Herein, MoO₂ /MoS₂ /C, with dual heterogeneous interfaces, is designed to induce a built-in electric field, which has been proved by experiments and theoretical calculation can accelerate electrochemical reaction kinetics and generate interfacial interactions to strengthen structural stability. The carbon foam serves as a conductive frame to assist the movement of electrons/ions, as well as forms heterogeneous interfaces with MoO₂ /MoS₂ through CS and CO bonds, maintaining structural integrity and enhancing electronic transport. Thanks to these unique characteristics, the MoO₂ /MoS₂ /C renders a significantly enhanced electrochemical performance (324 mAh g^-1 at 1 A g^-1 after 1000 cycles for SIB and 500 mAh g^-1 at 1 A g^-1 after 500 cycles for LIBs). The current work presents a simple, useful and cost-effective route to design high-quality electrodes via interfacial engineering.

Improving the Reaction Kinetics by Annealing MoS2/PVP Nanoflowers for Sodium-Ion Storage

Under the ever-growing demand for electrochemical energy storage devices, developing anode materials with low cost and high performance is crucial. This study established a multiscale design of MoS2/carbon composites with a hollow nanoflower structure (MoS2/C NFs) for use in sodium-ion batteries as anode materials. The NF structure consists of several MoS2 nanosheets embedded with carbon layers, considerably increasing the interlayer distance. Compared with pristine MoS2 crystals, the carbon matrix and hollow-hierarchical structure of MoS2/C exhibit higher electronic conductivity and optimized thermodynamic/kinetic potential for the migration of sodium ions. Hence, the synthesized MoS2/C NFs exhibited an excellent capacity of 1300 mA h g−1 after 50 cycles at a current density of 0.1 A g−1 and 630 mA h g−1 at 2 A g−1 and high-capacity retention at large charge/discharge current density (80% after 600 cycles 2 A g−1). The suggested approach can be adopted to optimize layered materials by embedding layered carbon matrixes. Such optimized materials can be used as electrodes in sodium-ion batteries, among other electrochemical applications.

Anisotropic Heavy-Metal-Free Semiconductor Nanocrystals: Synthesis, Properties, and Applications

Heavy-metal (Cd, Hg, and Pb)-containing semiconductor nanocrystals (NCs) have been explored widely due to their unique optical and electrical properties. However, the toxicity risks of heavy metals can be a drawback of heavy-metal-containing NCs in some applications. Anisotropic heavy-metal-free semiconductor NCs are desirable replacements and can be realized following the establishment of anisotropic growth mechanisms. These anisotropic heavy-metal-free semiconductor NCs can possess lower toxicity risks, while still exhibiting unique optical and electrical properties originating from both the morphological and compositional anisotropy. As a result, they are promising light-emitting materials in use various applications. In this review, we provide an overview on the syntheses, properties, and applications of anisotropic heavy-metal-free semiconductor NCs. In the first section, we discuss hazards of heavy metals and introduce the typical heavy-metal-containing and heavy-metal-free NCs. In the next section, we discuss anisotropic growth mechanisms, including solution-liquid-solid (SLS), oriented attachment, ripening, templated-assisted growth, and others. We discuss mechanisms leading both to morphological anisotropy and to compositional anisotropy. Examples of morphological anisotropy include growth of nanorods (NRs)/nanowires (NWs), nanotubes, nanoplatelets (NPLs)/nanosheets, nanocubes, and branched structures. Examples of compositional anisotropy, including heterostructures and core/shell structures, are summarized. Third, we provide insights into the properties of anisotropic heavy-metal-free NCs including optical polarization, fast electron transfer, localized surface plasmon resonances (LSPR), and so on, which originate from the NCs' anisotropic morphologies and compositions. Finally, we summarize some applications of anisotropic heavy-metal-free NCs including catalysis, solar cells, photodetectors, lighting-emitting diodes (LEDs), and biological applications. Despite the huge progress on the syntheses and applications of anisotropic heavy-metal-free NCs, some issues still exist in the novel anisotropic heavy-metal-free NCs and the corresponding energy conversion applications. Therefore, we also discuss the challenges of this field and provide possible solutions to tackle these challenges in the future.

Interface Density Engineering on Heterogeneous Molybdenum Dichalcogenides Enabling Highly Efficient Hydrogen Evolution Catalysis and Sodium Ion Storage

Constructing active heterointerfaces is powerful to enhance the electrochemical performances of transition metal dichalcogenides, but the interface density regulation remains a huge challenge. Herein, MoO₂ /MoS₂ heterogeneous nanorods are encapsulated in nitrogen and sulfur co-doped carbon matrix (MoO₂ /MoS₂ @NSC) by controllable sulfidation. MoO₂ and MoS₂ are coupled intimately at atomic level, forming the MoO₂ /MoS₂ heterointerfaces with different distribution density. Strong electronic interactions are triggered at these MoO₂ /MoS₂ heterointerfaces for enhancing electron transfer. In alkaline media, the optimal material exhibits outstanding hydrogen evolution reaction (HER) performances that significantly surpass carbon-covered MoS₂ nanorods counterpart (η₁₀ : 156 mV vs 232 mV) and most of the MoS₂ -based heterostructures reported recently. First-principles calculation deciphers that MoO₂ /MoS₂ heterointerfaces greatly promote water dissociation and hydrogen atom adsorption via the O-Mo-S electronic bridges during HER process. Moreover, benefited from the high pseudocapacitance contribution, abundant "ion reservoir"-like channels, and low Na⁺ diffusion barrier appended by high-density MoO₂ /MoS₂ heterointerfaces, the material delivers high specific capacity of 888 mAh g^-1 , remarkable rate capability and cycling stability of 390 cycles at 0.1 A g^-1 as the anode of sodium ion battery. This work will undoubtedly light the way of interface density engineering for high-performance electrochemical energy conversion and storage systems.

Enhanced Kinetic Behaviors of Hollow MoO2/MoS2 Nanospheres for Sodium-Ion-Based Energy Storage

Mo-based heterostructures offer a new strategy to improve the electronics/ion transport and diffusion kinetics of the anode materials for sodium-ion batteries (SIBs). MoO₂/MoS₂ hollow nanospheres have been successfully designed via in-situ ion exchange technology with the spherical coordination compound Mo-glycerates (MoG). The structural evolution processes of pure MoO₂, MoO₂/MoS₂, and pure MoS₂ materials have been investigated, illustrating that the structureofthenanospherecan be maintained by introducing the S-Mo-S bond. Based on the high conductivity of MoO₂, the layered structure of MoS₂ and the synergistic effect between components, as-obtained MoO₂/MoS₂ hollow nanospheres display enhanced electrochemical kinetic behaviors for SIBs. The MoO₂/MoS₂ hollow nanospheres achieve a rate performance with 72% capacity retention at a current of 3200 mA g^-1 compared to 100 mA g^-1. The capacity can be restored to the initial capacity after a current returns to 100 mA g^-1, while the capacity fading of pure MoS₂ is up to 24%. Moreover, the MoO₂/MoS₂ hollow nanospheres also exhibit cycling stability, maintaining a stable capacity of 455.4 mAh g^-1 after 100 cycles at a current of 100 mA g^-1. In this work, the design strategy for the hollow composite structure provides insight into the preparation of energy storage materials.

Confined WS2 Nanosheets Tubular Nanohybrid as High-Kinetic and Durable Anode for Sodium-Based Dual Ion Batteries

Sodium based dual-ion battery (SDIB) has been regarded as one of the promising batteries technologies thanks to its high working voltage and natural abundance of sodium source, its practical application yet faces critical issues of low capacity and sluggish kinetics of intercalation-type graphite anode. Here, a tubular nanohybrid composed of building blocks of carbon-film wrapped WS₂ nanosheets on carbon nanotube (WS₂ /C@CNTs) was reported. The expanded (002) interlayer and dual-carbon confined structure endowed WS₂ nanosheets with fast charge transportation and excellent structural stability, and thus WS₂ /C@CNTs showed highly attractive electrochemical properties for Na⁺ storage with high reversible capacity, fast kinetic, and robust durability. The full sodium-based dual ion batteries by coupling WS₂ /C@CNTs anode with graphite cathode full cell presented a high reversible capacity (210 mAh g^-1 at 0.1 A g^-1 ), and excellent rate performance with a high capacity of 137 mAh g^-1 at 5.0 A g^-1 .

Doping Regulation in Polyanionic Compounds for Advanced Sodium-Ion Batteries

It has long been the goal to develop rechargeable batteries with low cost and long cycling life. Polyanionic compounds offer attractive advantages of robust frameworks, long-term stability, and cost-effectiveness, making them ideal candidates as electrode materials for grid-scale energy storage systems. In the past few years, various polyanionic electrodes have been synthesized and developed for sodium storage. Specifically, doping regulation including cation and anion doping has shown a great effect in tailoring the structures of polyanionic electrodes to achieve extraordinary electrochemical performance. In this review, recent progress in doping regulation in polyanionic compounds as electrode materials for sodium-ion batteries (SIBs) is summarized, and their underlying mechanisms in improving electrochemical properties are discussed. Moreover, challenges and prospects for the design of advanced polyanionic compounds for SIBs are put forward. It is anticipated that further versatile strategies in developing high-performance electrode materials for advanced energy storage devices can be inspired.

Hard Carbons as Anodes in Sodium-Ion Batteries: Sodium Storage Mechanism and Optimization Strategies

Sodium-ion batteries (SIBs) are regarded as promising alternatives to lithium-ion batteries (LIBs) in the field of energy, especially in large-scale energy storage systems. Tremendous effort has been put into the electrode research of SIBs, and hard carbon (HC) stands out among the anode materials due to its advantages in cost, resource, industrial processes, and safety. However, different from the application of graphite in LIBs, HC, as a disordered carbon material, leaves more to be completely comprehended about its sodium storage mechanism, and there is still plenty of room for improvement in its capacity, rate performance and cycling performance. This paper reviews the research reports on HC materials in recent years, especially the research process of the sodium storage mechanism and the modification and optimization of HC materials. Finally, the review summarizes the sterling achievements and the challenges on the basis of recent progress, as well as the prospects on the development of HC anode materials in SIBs.

Phase Conversion Accelerating "Zn-Escape" Effect in ZnSe-CFs Heterostructure for High Performance Sodium-Ion Half/Full Batteries

Sodium-ion batteries (SIBs) are considered as a promising large-scale energy storage system owing to the abundant and low-cost sodium resources. However, their practical application still needs to overcome some problems like slow redox kinetics and poor capacity retention rate. Here, a high-performance ZnSe/carbon fibers (ZnSe-CFs) anode is demonstrated with high electrons/Na⁺ transport efficiency for sodium-ion half/full batteries by engineering ZnSe/C heterostructure. The electrochemical behavior of the ZnSe-CFs heterostructure anode is deeply studied via in situ characterizations and theoretical calculations. Phase conversion is revealed to accelerate the "Zn-escape" effect for the formation of robust solid electrolyte interphase (SEI). This leads to the ZnSe-CFs delivering a superior rate performance of 206 mAh g^-1 at 1500 mA g^-1 for half battery and an initial discharge capacity of 197.4 mAh g^-1 at a current density of 1 A g^-1 for full battery. The work here heralds a promising strategy to synthesize advanced heterostructured anodes for SIBs, and provides the guidance for a better understanding of phase conversion anodes.

Halogenated Carboxylates as Organic Anodes for Stable and Sustainable Sodium-Ion Batteries

Organic materials are competitive as anodes for Na-ion batteries (NIBs) due to the low cost, abundance, environmental benignity, and high sustainability. Herein, we synthesized three halogenated carboxylate-based organic anode materials to exploit the impact of halogen atoms (F, Cl, and Br) on the electrochemical performance of carboxylate anodes in NIBs. The fluorinated carboxylate anode, disodium 2, 5-difluoroterephthalate (DFTP-Na), outperforms the other carboxylate anodes with H, Cl, and Br, in terms of high specific capacity (212 mA h g^-1), long cycle life (300 cycles), and high rate capability (up to 5 A g^-1). As evidenced by the experimental and computational results, the two F atoms in DFTP reduce the solubility, enhance the cyclic stability, and interact with Na⁺ during the redox reaction, resulting in a high-capacity and stable organic anode material in NIBs. Therefore, this work proves that fluorinating carboxylate compounds is an effective approach to developing high-performance organic anodes for stable and sustainable NIBs.

Intercalation Reaction in Amorphous Layer-Wrapped Ni0.2Mo0.8N/Ni3N Heterostructure Toward Efficient Lithium-Ion Storage

Transition metal nitrides (TMNs) with high specific capacity and electric conductivity have drawn considerable attention as electrode materials of lithium-ion batteries (LIBs). However, the cycling stability of most TMNs is not satisfactory, which was caused by the large volume variation during cycles due to their intrinsic conversion reaction mechanism. Herein, by rational design, a much stable tremella-like Ni_0.2Mo_0.8N/Ni₃N heterostructure with amorphous Ni_0.2Mo_0.8N wrapped layer has been fabricated. The Ni₃N particles worked as pillars to support the Ni_0.2Mo_0.8N material as well as conductive medium to facilitate ionic and electronic transport. The amorphous layer can relieve the structural stress of Ni_0.2Mo_0.8N during cycles. Moreover, an exotic intercalation-type reaction mechanism in the ternary nitride Ni_0.2Mo_0.8N was revealed by a series ex situ and in situ characterization. Profiting from these advantages, the Ni_0.2Mo_0.8N/Ni₃N heterostructure anode displays an outstanding electrochemical performance with a high initial reversible discharge capacity of 1001.6 mA h g^-1 at 0.1 A g^-1, excellent cycle stability of 695.5 mA h g^-1 at 2 A g^-1 after 600 cycles, and superior rate capability of 595.3 mA h g^-1 at a high current density of 5 A g^-1. This work provides a new insight for designing high efficiency LIBs based on intercalation reaction for practical applications.

Electron-Injection and Atomic-Interface Engineering toward Stabilized Defected 1T-Rich MoS2 as High Rate Anode for Sodium Storage

1T-phase MoS₂ is a promising electrode material for electrochemical energy storage due to its metallic conductivity, abundant active sites, and high theoretical capacity. However, because of the habitual conversion of metastable 1T to stable 2H phase via restacking, the poor rate capacity and cycling stability at high current densities hamper their applications. Herein, a synergetic effect of electron-injection engineering and atomic-interface engineering is employed for the formation and stabilization of defected 1T-rich MoS₂ nanoflowers. The 1T-rich MoS₂ and carbon monolayers are alternately intercalated with each other in the nanohybrids. The metallic 1T-phase MoS₂ and conductive carbon monolayers are favorable for charge transport. The expanded interlayer spacing ensures fast electrolyte diffusion and the decrease of the ion diffusion barrier. The obtained defected 1T-rich MoS₂/m-C nanoflowers exhibit high Na-storage capacity (557 mAh g^-1 after 80 cycles at 0.1 A g^-1), excellent rate capacity (411 mAh g^-1 at 10 A g^-1), and long-term cycling performance (364 mAh g^-1 after 1000 cycles at 2 A g^-1). Furthermore, a Na-ion full cell composed of the 1T-rich MoS₂/m-C anode and Na₃V₂(PO₄)₃/C cathode maintains excellent cycling stability at 0.5 A g^-1 during 400 cycles. Theoretical calculations are also performed to evaluate the phase stability, electronic conductivity, and Na⁺ diffusion behavior of 1T-rich MoS₂/m-C. The energy storage performance demonstrates its excellent application prospects.

Facile and Controllable Synthesis of CuS@Ni-Co Layered Double Hydroxide Nanocages for Hybrid Supercapacitors

The synthesis of battery-type electrode materials with hollow nanostructures for high-performance hybrid supercapacitors (HSCs) remains challenging. In this study, hollow CuS@Ni-Co layered double hydroxide (CuS-LDH) composites with distinguished compositions and structures are successfully synthesized by co-precipitation and the subsequent etching/ion-exchange reaction. CuS-LDH-10 with uniformly dispersed CuS prepared with the addition of 10 mg of CuS shows a unique hollow polyhedral structure constituted by loose nanosphere units, and these nanospheres are composed of interlaced fine nanosheets. The composite prepared with 30 mg of CuS addition (CuS-LDH-30) is composed of a hollow cubic morphology with vertically aligned nanosheets on the CuS shell. The CuS-LDH-10 and CuS-LDH-30 electrodes exhibit high specific capacity (765.1 and 659.6 C g^-1 at 1 A g^-1, respectively) and superior cycling performance. Additionally, the fabricated HSC delivers a prominent energy density of 52.7 Wh kg^-1 at 804.5 W kg^-1 and superior cycling performance of 87.9% capacity retention after 5000 cycles. Such work offers a practical and effortless route for synthesizing unique metal sulfide/hydroxide composite electrode materials with hollow structures for high-performance HSCs.

Hollow nanospheres constructed by ultrafine few-layered MoS2 partially with amorphous fragments homogeneously incorporated in N-doped amorphous carbon for enhanced lithium storage performance

The rational design of ultrathin and few-layered structures for three-dimensional MoS₂ nanospheres is crucial for achieving attractive lithium-ion batteries (LIBs). Herein, hollow nanospheres constructed by ultrafine and few-layered MoS₂ homogeneously incorporated in N-doped amorphous carbon (HUF-MoS₂/NC) have been successfully synthesized as high-performance anode for LIBs. Using Mo-glycerol spheres as templates and dopamine hydrochloride as coordination ligands, hollow Mo-glycerol-polydopamine precursors are formed with Mo-containing groups which are surrounded by organic carbon species. Consequently, the MoS₂ is confined to the nanoscale and grows partially amorphous fragments while being uniformly embedded in NC. This unique architecture can not only hinder the substantial restacking between MoS₂ interlayers, offering more active sites, but also vastly enhance the electrical conductivity and relieve the mechanical stress ascribed to volume changes. As a result, the HUF-MoS₂/NC composite anode exhibits excellent cyclic stability (980mAhg^-1 after 300 cycles at 0.2Ag^-1) and superior rate performance (498mAhg^-1 at 5.0Ag^-1) for LIBs.

A graphene oxide scaffold-encapsulated microcapsule for polysulfide-immobilized long life lithium-sulfur batteries

Engineering high-performance cathodes for high energy-density lithium-sulfur (Li-S) batteries is quite significant to achieve commercialization. Here, we develop a graphene oxide scaffold/sulfur composite-encapsulated microcapsule (GSM) for high-performance Li-S batteries, which is prepared through the co-flow focusing (CFF) approach. The GSM-based cathode displays a high capacity of 1004 mA h g^-1 at 0.2C after cycling 200 times, a long-term cycling stability after 1000 cycles at 2C, and a good rate-performance. At temperatures of -5 °C and 45 °C, the electrochemical performance is also excellent. The computational calculations based on density functional theory (DFT) verify the high adsorption energies of the microcapsules towards polysulfides, suppressing the shuttle effect efficiently. It is expected that the GSM system developed based on the CFF method here and its high electrochemical performance will enable it to be applicable for preparing many other emerging energy-storage materials and secondary batteries.

Chemical Vapor Deposition Growth of MoS2 on g-C3N4 Nanosheets for Efficient Removal of Tetracycline Hydrochloride

MoS₂ was vertically grown on g-C₃N₄ nanosheets by chemical vapor deposition to prepare nanocomposites named MS-CN samples. Because of a large-surface area of 545.2 m²·g^-1 and a total pore volume of 1.7 cm³·g^-1, the sample MS-CN revealed fast and large adsorption capacity for tetracycline hydrochloride (TCH). The adsorption kinetics model proved that TCH could be rapidly adsorbed within 5 min, and chemical adsorption was dominant. For single-component adsorption of TCH, the maximum adsorption capacity was ∼154 mg/g. The monolayer adsorption was carried out on the surface of MS-CN. Both of the film and intra-particle diffusion were considered as significant processes to facilitate adsorption. Thermodynamic parameters indicate that the adsorption of TCH is a spontaneous endothermic process. The adsorption of TCH was highly pH-dependent. The maximum adsorption capacity of TCH was obtained in the case of pH ∼ 7. After four adsorption and desorption cycles, MS-CN still maintained well-adsorption performance. Multiple adsorption mechanism, pore filling, electrostatic force, π-π conjugation, and hydrogen bonding interactions were studied. Because of fast adsorption, large adsorption capacity, and high stability, it is a promising adsorbent for antibiotics.

Nitrogen-Doped Carbon Fibers Embedded with Zincophilic Cu Nanoboxes for Stable Zn-Metal Anodes

The practical application of Zn-metal anodes (ZMAs) is mainly impeded by the limited lifespan and low Coulombic efficiency (CE) resulting from the Zn dendrite growth and side reactions. Herein, a 3D multifunctional host consisting of N-doped carbon fibers embedded with Cu nanoboxes (denoted as Cu NBs@NCFs) is rationally designed and developed for stable ZMAs. The 3D macroporous configuration and hollow structure can lower the local current density and alleviate the large volume change during the repeated cycling processes. Furthermore, zincophilic Cu and in-situ-formed Cu-Zn alloy can act as homogeneous nucleation sites to minimize the Zn nucleation overpotential, further guiding uniform and dense Zn deposition. As a result, this Cu NBs@NCFs host exhibits high CE of Zn plating/stripping for 1000 cycles. The Cu NBs@NCFs-Zn electrode shows low voltage hysteresis and prolonged cycling life (450 h) with dendrite-free behaviors. As a proof-of-concept demonstration, a Zn-ion full cell is fabricated based on this Cu NBs@NCFs-Zn anode, which demonstrates decent rate capability and improved cycling performance.

In-Situ growing tungsten Sulfide/Carbon nanosheets on sodium titanate nanorods to stabilize Surface-Structure for enhanced Sodium-ion storage

Sodium-ions hybrid capacitors (SIHCs) have been recognized as one of the most potential energy storage devices, which can deliver high power and energy densities simultaneously. However, the sluggish kinetics of electrode materials severely restricts the performance of SIHCs. Herein, N, P-codoped carbon and WS₂ nanosheets coating on sodium titanate nanorods (NTO@WS₂/N, PC) were first designed by in-situ growing process and sulfuration treatment for boosting sodium-ion storage. Specifically, NTO@WS₂/N, PC electrodes displayed a satisfactory specific capacity of 274.7 mAh g^-1 at 3.0 A g^-1 after 1200 cycles. Furthermore, as-assembled SIHCs delivered high-energy density of 112.1 Wh kg^-1 and high-power density of 4334.4 W kg^-1. Besides, long-term cycling test revealed that a remarkable capacity retention rate of 89.7% was obtained at 8.0 A g^-1 after 2000 cycles. The excellent cycling stability and rate property could be ascribed to following aspects. On the one hand, N, P-codoped carbon could enhance the electrical conductivity and strengthen the structural integrality of the composites. On the other hand, ultrathin WS₂ nanosheets and one-dimensional (1D) NTO nanorods structure were conducive to the rapid diffusion of Na⁺. This work provides a convenient technique to stabilize the structure of electrode materials, which can promote the practical application of SIHCs.

Trimetallic Sulfide Hollow Superstructures with Engineered d-Band Center for Oxygen Reduction to Hydrogen Peroxide in Alkaline Solution

High-performance transition metal chalcogenides (TMCs) as electrocatalysts for two-electron oxygen reduction reaction (2e-ORR) in alkaline medium are promising for hydrogen peroxide (H₂ O₂ ) production, but their synthesis remains challenging. In this work, a titanium-doped zinc-cobalt sulfide hollow superstructure (Ti-ZnCoS HSS) is rationally designed as an efficient electrocatalyst for H₂ O₂ electrosynthesis. Synthesized by using hybrid metal-organic frameworks (MOFs) as precursors after sulfidation treatment, the resultant Ti-ZnCoS HSS exhibits a hollow-on-hollow superstructure with small nanocages assembled around a large cake-like cavity. Both experimental and simulation results demonstrate that the polymetallic composition tailors the d-band center and binding energy with oxygen species. Moreover, the hollow superstructure provides abundant active sites and promotes mass and electron transfer. The synergistic d-band center and superstructure engineering at both atomic and nanoscale levels lead to the remarkable 2e-ORR performance of Ti-ZnCoS HSS with a high selectivity of 98%, activity (potential at 1 mA cm^-2 of 0.774 V vs reversible hydrogen electrode (RHE)), a H₂ O₂ production rate of 675 mmol h^-1 g_cat ^-1 , and long-term stability in alkaline condition, among the best 2e-ORR electrocatalysts reported to date. This strategy paves the way toward the rational design of polymetallic TMCs as advanced 2e-ORR catalysts.

Sulfide with Oxygen-Rich Carbon Network for Good Lithium-Storage Kinetics

Transition metal sulfides are of great interest as electrode material for alkali metal-ion batteries due to their high theoretical capacity. However, sluggish ion migration and electron transfer kinetics lead to poor cycling stability and rate performance, which hinders their practical applications. Herein, we develop a two-step localized carbonization and sulfurization method to construct a CoS₂ composite material (CoS₂@CNTs@C) from an in situ integrated zeolitic imidazolate framework (ZIF-67) and multiwalled carbon nanotube precursor (ZIF-67@CNTs). The as-prepared CoS₂@CNTs@C composites with a nanoscale carbon skeleton inherit a large specific surface area and suitable nanopore size distribution from ZIF-67 and incredibly abundant oxygenated functional groups from CNTs. The theoretical calculation and material characterization demonstrate that the oxygenated functional groups on the porous carbon networks accelerate lithium-ion diffusion and electron transfer and especially electrocatalyze the progressive conversion of Li₂S₆ to the final product Li₂S. Meanwhile, the three-dimensional conductive network guarantees the conductive and structural stability of CoS₂@CNTs@C during the repeated lithium-storage process. Therefore, the CoS₂@CNTs@C electrode material can deliver an initial discharge capacity of 1282.3 mA h g^-1 at 200 mA g^-1 with a high Coulombic efficiency of 93.5% and a reversible capacity of 558.8 mA h g^-1 at 2000 mA g^-1 in 600 cycles with a high capacity retention of 96.1%.