Search

VS4 has a unique layered atomic chain structure and has the potential to become a high-performance cathode material of magnesium-ion batteries with a high capacity and long cycle life. However, low conductivity and sluggish Mg2+ diffusivity during cycling limit its practical application in large-scale energy storage. Herein, a cooperative assembly-directed strategy is adopted to synthesize VS4 nanorods grown in situ on carbon nanotubes (CNTs/VS4). VS4 nanorods are tightly anchored to CNTs through V–O–C interface covalent bonds, and CNTs can enhance the electronic conductivity of the nanocomposite. In addition, the ion insertion reaction using Mg2+ and MgCl+ as carriers reduces the polar barrier for divalent Mg2+ ion transport. This rationally designed architecture promotes ion diffusion and electron transfer, thus facilitating reaction kinetics. The cooperative assembly-oriented strategy can endow CNTs/VS4 with excellent magnesium storage properties, including a high reversible capacity of 223.2 mAh g−1 at a current density of 50 mA g−1, a remarkable discharge capacity of 91.8 mAh g−1 even at 2,000 mA g−1, and an impressive capacity retention of 85.2% after 1,000 cycles at 500 mA g−1. Moreover, this strategy can serve as a general synthetic method for the complexation of VS4 with other carbon nanostructures. [ABSTRACT FROM AUTHOR]

Electrodeposition, a binder-free technique, enables the formation of uniform and well-defined structures on the electrode surface. Herein, the material has directly grown on nickel foam by deposition through cyclic voltammetry at a fixed scan rate. The surface morphology of as-synthesized electrodes is observed with SEM and the electrochemical examination has been performed in three-electrode assembly. The highest specific capacitance attained from GCD analysis for MnS is 1453 F/g, CoS has 2476 F/g and CuS exhibits 1908 F/g at 6 A/g current density. The quantitative investigation of the inherent charge storage mechanism of an individual electrode is achieved by implementing different mathematical models on experimental data sets. The electrodes displayed a more diffusive contribution which uncovered our findings that each electrode illustrates the battery-grade properties. The results suggested that the fabricated electrode consumes an excellent potential as a high energy source for hybrid energy storage devices. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction (ECR) to value-added products is regarded as a sustainable strategy to mitigate global warming and energy crisis, and designing highly efficient and robust catalysts is essential. In this work, transition metal sulfides (TMS)-decorated CuS microflower-like structures were prepared via the one-pot hydrothermal synthesis method for ECR to CO, and the influence of TMS doping on ECR performance was demonstrated. Characterization of the catalysts was performed using XRD, FESEM-EDS, N2 physisorption, and XPS, revealing the successful loading of TMS, the formation of microflower-like architectures and the generation of sulfur vacancies. Electrochemical tests demonstrated that doping ZnS, Bi2S3, CdS and MoS2 improved the intrinsic CO2 reduction activity of the CuS catalyst. Particularly, the MoS2-CuS composite catalyst with imperfect petal-like structure showed uniform distribution of edge Mo sites, which worked synergistically with the formed grain boundaries (GBs) and undercoordinated S vacancy sites in promoting CO2 activation, stabilizing *COOH adsorption, facilitating *CO desorption, and lowering the energy barrier of the potential-limiting step for improved CO selectivity. The MoS2-CuS catalyst achieved a maximum CO selectivity of 83.2% at –0.6 V versus the reversible hydrogen electrode (RHE) and a high CO cathodic energetic efficiency of 100%. At this potential, the catalyst maintained stable catalytic activity and CO selectivity during a 333-min electrolysis process. The findings will offer a promising avenue for the development of efficient and stable catalysts for CO production from ECR. [ABSTRACT FROM AUTHOR]

Supercapattery is an ideal energy storage device combining the features of supercapacitors and batteries, offers a high‐energy density as well as high‐power density with extended operational lifespan. In this work, zinc sulfide (ZnS) and zinc sulfide/nickel oxide (ZnS/NiO) nanocomposite was synthesized via chemical coprecipitation method and characterized using state‐of‐the‐art analytical tools. The ZnS/NiO electrode exhibited remarkable electrochemical performance as an electrode material than pure ZnS. The ZnS/NiO nanocomposite exhibited high crystallinity, and spherical nanoparticles with an average grain size of 20–40 nm having a homogeneous dispersion. The ZnS/NiO electrode exhibited an ultrahigh specific capacity of 1803.87 Cg−1 at a relatively low scan rate of 10 mVs−1 in a 1 M KOH solution from cyclic voltammetry and 393 Cg−1 at 16 Ag−1 from charge discharge measurements, and it showed exceptional cycling stability (98 % capacity retention after 1000 cycles). Furthermore, the ZnS/NiO symmetric supercapattery device exhibited 44.43 Fg−1 specific capacitance, 5.52 Wh kg−1 energy density, and 1600 Wkg−1 power density at current density of 0.8 Ag−1 in 1 M KOH solution from galvanostatic charge discharge. After 3000 cycles, the ZnS/NiO nanomaterial demonstrated promising cyclic stability of 95 %. The ZnS/NiO supercapattery nanocomposite might be considered as a potential hybrid electrode material for the future development of electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

It is of great significance to use biomass resources to prepare electrocatalysts for hydrogen evolution reaction (HER) during water splitting. Herein, using egg white as S source (adding Na2MoO4 only), we fabricate amorphous N/P-doped molybdenum oxygen sulfide grown on Ni foam (NF) via a facile one-pot hydrothermal method. N and P elements in egg white can be partially doped into MoOxSy to produce the electrocatalyst used for HER. Under different reaction temperature of m °C (m = 160, 170, 180) and mole number of n (n = 6, 10, 12 mmol) of the Mo salt (Na2MoO4) added, series of N/P-MoOxSy/NF-m–n materials are obtained. The loose and porous morphology of the MoOxSy/NF-m–n is conducive to full contact with the electrolyte, and N/P doping can optimize the electronic structure, together improving the HER performance. The optimized electrocatalyst of N/P-MoOxSy/NF-170–10 (m = 170, n = 10) shows the best HER activity and stability, requiring a much low overpotential of 122 mV to achieve the current density of 10 mA cm−2 (η10 = 122 mV), and operating long-term (≥ 40 h) electrolysis at a constant potential of − 130 mV (vs. RHE) in acidic media (0.5 M H2SO4). The electrocatalytic property is comparable to or even beyond the known HER electrocatalysts derived from biomass. This work provides a new strategy for the design of non-metal-doped catalysts using biomass as raw materials. [ABSTRACT FROM AUTHOR]

Developing a reasonable design of a lithiophilic artificial solid electrolyte interphase (SEI) to induce the uniform deposition of Li+ ions and improve the Coulombic efficiency and energy density of batteries is a key task for the development of high-performance lithium metal anodes. Herein, a high-performance separator for lithium metal anodes was designed by the in situ growth of a metal–organic framework (MOF)-derived transition metal sulfide array as an artificial SEI on polypropylene separators (denoted as Co9S8-PP). The high ionic conductivity and excellent morphology provided a convenient transport path and fast charge transfer kinetics for lithium ions. The experimental data illustrate that, compared with commercial polypropylene separators, the Li//Cu half-cell with a Co9S8-PP separator can be cycled stably for 2000 h at 1 mA cm−2 and 1 mAh cm−2. Meanwhile, a Li//LiFePO4 full cell with a Co9S8-PP separator exhibits ultra-long cycle stability at 0.2 C with an initial capacity of 148 mAh g−1 and maintains 74% capacity after 1000 cycles. This work provides some new strategies for using transition metal sulfides to induce the uniform deposition of lithium ions to create high-performance lithium metal batteries. [ABSTRACT FROM AUTHOR]

Supercapacitor (SC) devices holds an important position between traditional capacitors and ion batteries in terms of energy density and power density values. In particular, SC′s greater power density values than Li‐ion batteries make them useful for some specific applications, such as storing energy in hybrid cars while the car slows down. Increasing energy density values is one of the key challenges for the SC community. Transition metal dichalcogenides (TMDCs), are one of the new developing important material systems to have this potential, compared to their counterparts' transition metal oxides and conductive polymers. This review is about giving insight into the electrochemical performances of two‐dimensional (2D) layered transition metal sulfides (TMS) such as MoS2, WS2, TaS2, NbS2, VS2, TiS2 and ZrS2 materials. On the other hand, the methods mostly used in synthesizing these materials are presented. [ABSTRACT FROM AUTHOR]

Amino acids are one of the most important building blocks of life. During the biochemical process of translation, cells sequentially connect amino acids via amide bonds to synthesize proteins, using the genetic information in messenger RNA (mRNA) as a template. From a prebiotic perspective (i.e., without enzymatic catalysis), joining amino acids to peptides via amide bonds is difficult due to the highly endergonic nature of the condensation reaction. We show here that amides can be formed in reactions catalyzed by the transition metal sulfides from acetylene, carbon monoxide and ammonia under aqueous conditions. Some α- and β-amino acids were also formed under the same conditions, demonstrating an alternative cyanide-free path for the formation of amino acids in prebiotic environments. Experiments performed with stable isotope labeled precursors, like 15NH4Cl and 13C-acetylene, enabled the accurate mass spectroscopic identification of the products formed from the starting materials and their composition. Reactions catalyzed using the transition metal sulfides seem to offer a promising alternative pathway for the formation of amides and amino acids in prebiotic environments, bypassing the challenges posed by the highly endergonic condensation reaction. These findings shed light on the potential mechanisms by which the building blocks of life could have originated on early Earth. [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs) still confront the challenges of capacity fading and inferior fast‐charging capability for sodium storage. The rational design of heterostructures enables a new approach to conquer these drawbacks. In this work, a hierarchical structure consisting of SnS2 nanosheets and FeS2 microrods with triphasic heterostructures is proposed by the facile secondary growth and sulfidation process. The introduction of tin sources regulates the proportion of pyrite and marcasite phases, thereby achieving the triphasic heterostructures comprising pyrite, marcasite FeS2, and SnS2. When served as anode material for sodium‐ion batteries, the optimized sample exhibits a high reversible capacity (901 mAh g−1) and durable cycling performances (827 mAh g−1 after 200 cycles at 1 A g−1 and 742 mAh g−1 after 700 cycles at 5 A g−1). Paring with the commercial Na3V2(PO3)3 cathodes, the full‐cell also delivers extraordinary cyclic stability with a high capacity of 618 mAh g−1 (based on the weight of anode material) after 200 cycles at 1 A g−1 (98.7% capacity retention). The hierarchical structure with adjustably triphasic heterogeneous interfaces alleviates the volumetric expansion and interfacial passivation of active material, while modulating the energy band structure and inducing the build‐in electric fields to boost Na+/electrons transport rate. [ABSTRACT FROM AUTHOR]

The commercialization of Li−S batteries is seriously hindered by polysulfides with severe shuttle effect, and the inherent insulating properties and slow reaction kinetics of insoluble Li2S products. Transition metal sulfides (TMSs) have a high adsorption capacity for polysulfides and have been shown to have a strong catalytic effect on polysulfide conversion reactions. This paper reviews the research on the application of Unary TMSs, heterostructures, etc. in Li−S batteries, and gives some research methods for TMD catalysts in Li−S batteries. Finally, it points out the main focuses and direction of future Li−S battery research and development. It aims to provide some insights into the design and manufacture of advanced Li−S batteries for commercial use. [ABSTRACT FROM AUTHOR]

In this study, we synthesized a transition metal sulfide (TMS) with a spinel structure, i.e., MnIn2S4 (MIS), using a two-step hydrothermal and sintering process. In the context of lithium-ion battery (LIB) applications, ternary TMSs are being considered as interesting options for anode materials. This consideration arises from their notable attributes, including high theoretical capacity, excellent cycle stability, and cost-effectiveness. However, dramatic volume changes result in the electrochemical performance being severely limited, so we introduced single-walled carbon nanotubes (SWCNTs) and prepared an MIS/SWCNT composite to enhance the structural stability and electronic conductivity. The synthesized MIS/SWCNT composite exhibits better cycle performance than bare MIS. Undergoing 100 cycles, MIS only yields a reversible capacity of 117 mAh/g at 0.1 A/g. However, the MIS/SWCNT composite exhibits a reversible capacity as high as 536 mAh/g after 100 cycles. Moreover, the MIS/SWCNT composite shows a better rate capability. The current density increases with cycling, and the SWCNT composite exhibits high reversible capacities of 232 and 102 mAh/g at 2 A/g and 5 A/g, respectively. Under the same conditions, pristine MIS can only deliver reversible capacities of 21 and 4 mAh/g. The results indicate that MIS/SWCNT composites are promising anode materials for LIBs. [ABSTRACT FROM AUTHOR]

Although in‐plane heterostructure with high ion transport pathway and unique interfacial atomic structure offers endless possibilities in the catalysis field, it is still challenging to directly synthesize MXene‐based in‐plane heterostructure due to the differences in crystal structures and growth conditions. Here, Mo2C–MoS2 in‐plane multi‐heterostructures are synthesized by topological conversion of sandwich‐like mesoporous Mo2C–SiO2 layers in sulfur vapor and subsequent removal of SiO2. During the conversion process, the exposed Mo2C will efficiently converted to 2H phase MoS2, meanwhile, the covered Mo2C remained stable, affording metallic Mo2C MXene and semiconducting MoS2 in‐plane multi‐heterostructures compatible in one layer. The resultant Mo2C–MoS2 layer has multiple heterointerfaces, build‐in electric fields as well as abundant defects. Such structural features enable to improve of the electrochemical active surface area (16.4 mF cm−2), which not only facilitates the bidirectional sulfur electrochemistry between solid Li2S and soluble lithium polysulfides, but also enhances the transfer kinetics of electrons and ions, giving rise to a high‐rate performance (642 mAh g−1 at 5 C) and a long‐term cycle life (1000 cycles at 5 C) in lithium–sulfur batteries. [ABSTRACT FROM AUTHOR]

Lithium‐sulfur (Li−S) batteries show advantage of high theoretical capacity. However, the shuttle effect of polysulfides and sluggish sulfur redox kinetics seriously reduce their service life. Inspired by the porous structural features of biomass materials, herein, a functional interlayer is fabricated by silkworm excrement‐derived three‐dimensional porous carbon accommodating nano sized CoS2 particles (SC@CoS2). The porous carbon delivers a high specific surface area, which provides adequate adsorption sites, being responsible for suppressing the shuttle effect of polysulfides. Meanwhile, the porous carbon is favorable for hindering the aggregation of CoS2 and maintaining its high activity during extended cycles, which effectively accelerates the polysulfides conversion kinetics. Moreover, the SC@CoS2 functional interlayer effectively limits the formation of Li dendrites and promotes the uniform deposition of Li on the Li electrode surface. As a result, the CMK‐3/S cathode achieves a high initial capacity of 1599.1 mAh g−1 at 0.2 C rate assisted by the polypropylene separator coated with the functional interlayer and 1208.3 mAh g−1 is maintained after the long cycling test. This work provides an insight into the designing of long‐lasting catalysts for stable functional interlayer, which encourages the application of biomass‐derived porous carbon in high‐energy Li−S batteries. [ABSTRACT FROM AUTHOR]

In this paper, we report the use of femtosecond radially polarized vortex laser with MHz repetition rate for direct writing of cladding waveguides (WGs) and realization of waveguide laser oscillations in ytterbium-doped calcium fluoride crystal. The negative refractive index modification in Yb:CaF2 crystal is fabricated by the homemade all-fiber laser amplifier. At 976 nm pump wavelength, these Yb:CaF2 WGs can achieve continuous-wave (CW) laser oscillation. The length of resonant cavity is 4 mm, and the minimum laser threshold is 116 mW, corresponding to the propagation loss of 0.85 dB/cm, the center wavelength of 1045.2 nm, and the maximum output power of 91 mW. In addition, a saturable absorber mirror (SAM) was prepared by depositing ReS0.8Se1.2 on the reflective surface of a dichroic mirror to realize Q-switched waveguide laser output. The output Q-switched pulses with a tunable repetition rate in the range of 125–692.5 kHz, and the shortest pulse duration is 513 ns. [ABSTRACT FROM AUTHOR]

In this work, CuCo@C and CuCoS@C derived from an in-situ synthesis bi-metallic MOF HKUST-1/ZIF-67 (CuCo-MOF) were successfully fabricated by calcination and hydrothermal sulfide strategies. Morphology characterization results indicated that ZIF-67 grew uniformly on the surface of HKUST-1 to form CuCo-MOF. And, benefiting from bi-metallic MOFs precursors, the formed derivatives inherited and possessed good textural properties and dispersing well metal sites, which facilitated diffusions of molecules and enhancements of catalytic performances. In addition, carbon matrix produced in the materials further accelerated electron transporting properties, boosting HER and OER activities. Accordingly, in electrolytic water evaluations, CuCo@C and CuCoS@C showed good HER and OER performance, achieving 97 mV and 180 mV of overpotential at 10 mA cm−2 in an alkaline medium, respectively. Additionally, the catalysts exhibit long-term stabilities. Thus, this study provides a rational way for designing and constructing of high-efficient catalysts for H2 and O2 generations from electrolytic water processes. [ABSTRACT FROM AUTHOR]

The tetracarbonyl complexes of transition metal chalcogenides M2X2(CO)4, where M = Fe, Co, Ni, Cu and X = S, Se, are examined by density functional theory (DFT). The M2X2 core is cyclic with either planar or non-planar geometry. As a sulfide, it is present in natural enzymes and has a selective redox capacity. The reduced forms of the selenide and sulfide complexes are relevant to the hydrogen evolution reaction (HER) and they provide different positions of hydride ligand binding: (i) at a chalcogenide site, (ii) at a particular cation site and (iii) in a midway position forming equal bonds to both cation sites. The full pathway of water decomposition to molecular hydrogen and oxygen is traced by transition state theory. The iron and cobalt complexes, cobalt selenide, in particular, provide lower energy barriers in HER as compared to the nickel and copper complexes. In the oxygen evolution reaction (OER), cobalt and iron selenide tetracarbonyls provide a low energy barrier via OOH* intermediate. All of the intermediate species possess favorable excitation transitions in the visible light spectrum, as evidenced by TD-DFT calculations and they allow photoactivation. In conclusion, cobalt and iron selenide tetracarbonyl complexes emerge as promising photocatalysts in water splitting. [ABSTRACT FROM AUTHOR]

Layered guest carbon materials could induce interlayer engineering, especially in regulating the interlayer structure and electronic properties of the hosts, leading to high performance in Li‐ion batteries (LIBs). Here, crystalline graphdiyne oxide (GDYO) is successfully inserted into MoS2 gallery via electrostatic self‐assembly. Experimental and theoretical data show that GDYO‐embedding induces interlayer engineering of MoS2 causing (i) enlarged MoS2 interlayer distance (supplying additional Li‐ion diffusion channels and storage sites and mitigating volume change), (ii) creating interfacial electric fields (significantly improving Li‐ion transport kinetics), (iii) limiting the electrochemical products of Mo and soluble lithium polysulfide (MoS2 structure regeneration), and (iv) regulation of the interfacial current density distribution during the electrochemical reaction (uniform Li plating). Moreover, through systematic ex situ and in situ investigations, the triple‐mechanism of Li‐ion storage is thoroughly elucidated in the heterostructure, emphasizing the positive effects of GDYO intercalation on the interfacial and interlayer storage as well as the phase conversion processes. Such a MoS2/GDYO anode exhibits high reversible capacity (≈652.6 mAh g−1 at 2.0 A g−1) and superior cyclic stability of 655.1 mAh g−1 after 1000 cycles. GDYO‐induced interlayer engineering based on host–guest chemistry can provide new ideas for designing effective heterostructures for high‐performance energy storage and conversion systems. [ABSTRACT FROM AUTHOR]

With the rapid improvement of compact smart devices, fabricating anode materials with high volumetric capacity has gained substantial interest for future sodium‐ion batteries (SIBs) applications. Herein, a novel bimetal sulfide CuCo5S8 material is proposed with enhanced volumetric capacity due to the intrinsic metallic electronic conductivity of the material and multi‐electron transfer during electrochemical procedures. Due to the intrinsic metallic behavior, the conducting additive (CA) could be removed from the electrode fabrication without scarifying the high rate capability. The CA‐free CuCo5S8 electrode can achieve a high volumetric capacity of 1436.4 mA h cm−3 at a current density of 0.2 A g−1 and 100 % capacity retention over 2000 cycles in SIBs, outperforming most metal chalcogenides, owing to the enhanced electrode density. Reversible conversion reactions are revealed by combined measurements for sodium systems. The proposed new strategy offers a viable approach for developing innovative anode materials with high‐volumetric capacity. [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs) are considered to be highly promising electrode materials for supercapacitors. Optimizing the structure of the electrode materials to expose more active sites is a crucial strategy for boosting the electrochemical performance. Herein, we developed carbon/metal sulfide composite electrode materials by anchoring nickel–cobalt bimetallic sulfide nanosheets (NCS) on chitosan-derived heteroatom-doped hierarchical porous carbon (CPC). The composite materials exhibited a uniform distribution and significantly increased active sites, which led to a substantial enhancement of the electrochemical properties. The optimal sample NCS/CPC-3 exhibited a brilliant capacitive performance and great cycling stability. Also, the assembled asymmetric supercapacitor presented a robust energy output of 37.1 W h kg–1 at 800.0 W kg–1. In addition, NCS/CPC-3 also demonstrated potential in the field of small-molecule detection. Our findings supply a unique perspective on effectively boosting the electrochemical properties of TMS-based electrode materials. [ABSTRACT FROM AUTHOR]

Water electrolysis technology is considered to be one of the most promising means to produce hydrogen. Herein, aiming at the problems of high overpotential and slow kinetics in water splitting, N-doped porous carbon nanofibers-coupled CoNi2S4 nanoparticles are prepared as bifunctional electrocatalyst. In the strategy, NaCl is used as the template to prepare porous carbon nanofibers with a large surface area, and sulfur vacancies are created to modulate the electronic structure of CoNi2S4. Electron spin resonance confirms the formation of abundant sulfur vacancies, which largely reduce the bandgap of CoNi2S4 from 1.68 to 0.52 eV. The narrowed bandgap is conducive to the migration of valence electrons and decreases the charge transfer resistance for electrocatalytic reaction. Moreover, the uniform distribution of CoNi2S4 nanoparticles on carbon nanofibers can prevent the aggregation and facilitate the exposure of electrochemical active sites. Therefore, the composite catalyst exhibits low overpotentials of 340 mV@100 mA·cm−2 for oxygen evolution reaction and 380 mV@100 mA·cm−2 for hydrogen evolution reaction. The assembled electrolyzer requires 1.64 V to achieve 10 mA·cm−2 for overall water-splitting with good long-term stability. The excellent performance results from the synergistic effect of porous structures, sulfur deficiency, nitrogen doping, and the well-dispersed active component. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Functional Materials / Gongneng Cailiao is the property of Chongqing Functional Materials Periodical Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Cobalt sulfides are considered as promising candidates for lithium-ion battery (LIB) anode materials with high energy densities. Their energy storage mechanism is widely understood to involve the traditional intercalation and conversion reaction. However, these conventional mechanisms are unable to explain the storage capacities of certain materials which exceed the theoretical limit. Here, utilizing advanced in situ magnetometry to detect the magnetization evolution of Co1-x S LIBs in real time, it is demonstrated that the Co-catalytic lithium storage process and interfacial space charge storage mechanism are strongly related to the additional capacity of cobalt sulfides. During discharge, a Co/Li2 S interface is formed, wherein the Co nanoparticles and Li2 S could store a large amount of polarized electrons Li+, respectively. Subsequently, the electrons stored in Co are transferred to the polymeric film, forming radical anions and contributing extra capacity. These findings reveal the charge storage mechanisms of transition metal sulfides and highlight the critical role of magnetic testing in the investigation of energy storage mechanisms. [ABSTRACT FROM AUTHOR]

Transition metal sulfides with mixed vulcanized states (TMS‐mVs) possess tremendous potential to realize highcapacity, superior redox reactions, and structural reversibility for metal‐ion (Mn+) storage owing to their multielectron reactions caused by the simultaneous participation of transition metal (TM) cations and S22− anions as well as multifarious TM or S valence states. Here, recent advances are systematically introduced regarding the mainstream TMS‐mVs that can be applied to Mn+ storage. These TMS‐mVs can be divided into two categories of TMS, those with mixed sulfur‐valence states (TMS‐mSs) and those with mixed metal‐valence states (TMS‐mMs). It is found that TMS‐mV anodes mainly experience three reaction mechanisms, inculding insertion‐accompanied conversion, insertion, and conversion reactions. During the reversible charge process, Li2S is possibly oxidized into polysulfides or even S. TMS‐mVs have the ability to transfer more electrons than other homogeneous TMSs. TMS‐mS anodes usually present higher theoretical specific capacities than TMS‐mM anodes. In these TMS‐mV anodes, Mo‐based, V‐based, and Co‐based TMS‐mM anodes exhibit good electrochemical reversibility, Ni‐based TMS‐mM anodes exhibit moderate electrochemical reversibility, and Fe‐based TMS‐mM and TMS‐mS anodes exhibit poor electrochemical reversibility. The strategies for enhancement of their electrochemical performance are classified into composite, coating, nanostructure, heterointerface, and lattice engineering. [ABSTRACT FROM AUTHOR]

Nano-structure designs with conductive networks have been demonstrated as an efficient strategy to boost sodium storage properties for transition metal sulfides. Herein, an exquisite nanosheets self-assembled hierarchical flower-ball-like CuFeS2 embedded into the reduced graphene oxide (RGO) nanosheet matrix (F-CuFeS2@RGO) is fabricated via a concise two-step solvothermal method. Such a well-designed architecture affords increased active reaction interfaces and enhanced mixed ionic/electronic conductivity. Meanwhile, the external RGO matrix can effectively alleviate the volume expansion and create a stable structure during long cycles. As a result, the composite material exhibits a high reversible capacity of 559 mAh·g−1 at 0.1 A·g−1, a superior rate capability of 455 mAh·g−1 at 5 A·g−1 and excellent cyclic stability with 96% capacity retention after 4800 cycles at 5 A·g−1, among the best in the state-of-the-art transition metal sulfide anodes. Especially, F-CuFeS2@RGO delivers outstanding low-temperature performances with a high capacity retention of 100% and 91% at −20 and −40 °C, respectively, over 200 cycles. The proposed hierarchical structure fabrication paves a new direction in the design of high-performance electrodes for all-temperature energy storage applications. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a waxberry‐like MnS/Ni3S4 composite catalyst was designed and synthesized. In this coating structure, MnS is located inside and Ni3S4 is wrapped on the surface to form a spherical structure. This structure makes the material show excellent stability in the electrocatalytic process. The diffusion staggered region structure formed at the two‐phase interface greatly enhances the synergistic interaction between MnS and Ni3S4. At the same time, the defects and vacancies formed by the diffusion mechanism at the interface of the two phases increase the active site and improve the interfacial electron transfer kinetics. Therefore, MnS/Ni3S4 composites showed good catalytic performance for ORR/OER. At 10 mA cm−2, the overpotential of it is only 320 mV, and the half‐wave potential can reach 0.81 V. The catalyst also exhibited extraordinary cycle stability and small voltage gap when used as cathode of Zn‐air batteries. When the current density is 3 mA cm−2, the cyclic discharge can be stable for 400 h and the voltage difference between the front and back does not increase more than. When the current density increases to 5 mA cm−2, the cyclic charge and discharge can be stable for more than 300 h. [ABSTRACT FROM AUTHOR]

Oriented synthesis of transition metal sulfides (TMSs) with controlled compositions and crystal structures has long been promising for electronic devices and energy applications. Liquid‐phase cation exchange (LCE) is a well‐studied route by varying the compositions. However, achieving crystal structure selectivity is still a great challenge. Here, we demonstrate gas‐phase cation exchange (GCE), which can induce a specific topological transformation (TT), for the synthesis of versatile TMSs with identified cubic or hexagonal crystal structures. The parallel six‐sided subunit (PSS), a new descriptor, is defined to describe the substitution of cations and the transition of the anion sublattice. Under this principle, the band gap of targeted TMSs can be tailored. Using the photocatalytic hydrogen evolution as an example, the optimal hydrogen evolution rate of a zinc‐cadmium sulfide (ZCS4) is determined to be 11.59 mmol h−1 g−1, showing a 36.2‐fold improvement over CdS. [ABSTRACT FROM AUTHOR]

Oriented synthesis of transition metal sulfides (TMSs) with controlled compositions and crystal structures has long been promising for electronic devices and energy applications. Liquid‐phase cation exchange (LCE) is a well‐studied route by varying the compositions. However, achieving crystal structure selectivity is still a great challenge. Here, we demonstrate gas‐phase cation exchange (GCE), which can induce a specific topological transformation (TT), for the synthesis of versatile TMSs with identified cubic or hexagonal crystal structures. The parallel six‐sided subunit (PSS), a new descriptor, is defined to describe the substitution of cations and the transition of the anion sublattice. Under this principle, the band gap of targeted TMSs can be tailored. Using the photocatalytic hydrogen evolution as an example, the optimal hydrogen evolution rate of a zinc‐cadmium sulfide (ZCS4) is determined to be 11.59 mmol h−1 g−1, showing a 36.2‐fold improvement over CdS. [ABSTRACT FROM AUTHOR]

A quest for a low-cost and efficient alternative energy conversion/storage system has attracted much interest in the past decades. Transition metal sulfides have been proven as potential electrode materials for supercapacitor and battery technology applications. This report investigates the structure and electronic properties of ternary transition metal sulfides CuX2S4 nanomaterials (X = Ti, V, Cr, Mn, Fe, Co, Ni) by invoking Conceptual Density Functional Theory (CDFT) method. The computed energy gap of CuX2S4 species is in the range of 1.117–3.365 eV. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap of transition metal sulfide follows the order as CuCr2S4 < CuCo2S4 < CuV2S4 < CuMn2S4 < CuFe2S4 < CuTi2S4 < CuNi2S4. It specifies that the electronic stability of CuNi2S4 is superior to that of CuCr2S4. A close agreement between the computed bond lengths and the existing experimental data signifies the novelty of this work. [ABSTRACT FROM AUTHOR]

At present, binary bimetallic sulfides are widely studied in supercapacitors due to their high conductivity and excellent specific capacitance (SC). In this article, NiCo-S nanostructured hybrid electrode materials were prepared on nickel foam (NF) by using a binary metal–organic skeleton as the sacrificial template via a two-step hydrothermal method. Comparative analysis was carried out with Ni-S and Co-S in situ on NF to verify the excellent electrochemical performance of bimetallic sulfide as an electrode material for supercapacitors. NiCo-S/NF exhibited an SC of 2081 F∙g−1 at 1 A∙g−1, significantly superior to Ni-S/NF (1520.8 F∙g−1 at 1 A∙g−1) and Co-S/NF (1427 F∙g−1 at 1 A∙g−1). In addition, the material demonstrated better rate performance and cycle stability, with a specific capacity retention rate of 58% at 10 A∙g−1 than at 1 A∙g−1, and 75.7% of capacity was retained after 5000 cycles. The hybrid supercapacitor assembled by NiCo-S//AC exhibited a high energy density of 25.58 Wh∙kg−1 at a power density of 400 W∙kg−1. [ABSTRACT FROM AUTHOR]

Herein, a scalable electrodeposition strategy is proposed to achieve hierarchical CuO/nickel–cobalt–sulfide (NCS) electrodes using two-step potentiostatic deposition followed by high-temperature calcination. The introduction of CuO provides support for the further deposition of NSC to ensure a high load of active electrode materials, thus generating more abundant active electrochemical sites. Meanwhile, dense deposited NSC nanosheets are connected to each other to form many chambers. Such a hierarchical electrode prompts a smooth and orderly transmission channel for electron transport, and reserves space for possible volume expansion during the electrochemical test process. As a result, the CuO/NCS electrode exhibits superior specific capacitance (Cs) of 4.26 F cm−2 at 20 mA cm−2 and remarkable coulombic efficiency of 96.37%. Furthermore, the cycle stability of the CuO/NCS electrode remains at 83.05% within 5000 cycles. The multistep electrodeposition strategy provides a basis and reference for the rational design of hierarchical electrodes to be applied in the field of energy storage. [ABSTRACT FROM AUTHOR]

The electrocatalytic hydrogen evolution activity of transition metal sulfide heterojunctions are significantly increased when compared with that of a single component, but the mechanism behind the performance enhancement and the preparation of catalysts with specific morphologies still need to be explored. Here, we prepared a Co9S8/MoS2 heterojunction with microsphere morphology consisting of thin nanosheets using a facile two-step method. There is electron transfer between the Co9S8 and MoS2 of the heterojunction, thus realizing the redistribution of charge. After the formation of the heterojunction, the density of states near the Fermi surface increases, the d-band center of the transition metal moves downward, and the adsorption of both water molecules and hydrogen by the catalyst are optimized. As a result, the overpotential of Co9S8/MoS2 is superior to that of most relevant electrocatalysts reported in the literature. This work provides insight into the synergistic mechanisms of heterojunctions and their morphological regulation. [ABSTRACT FROM AUTHOR]

It is an effective strategy to improve the catalytic activity of materials by constructing hydroxide/sulfide hybrid structure. In this work, nickel hydroxide/CoNi sulfide (Ni(OH)2/CoNi2S4) nanoflowers supported on nickel foam (NF) were synthesized by simple hydrothermal reaction and subsequent sulfurization, used as an efficient hydrogen evolution reaction (HER) electrocatalyst in acidic medium. The results show that as-synthesized Ni(OH)2/CoNi2S4/NF catalyst exhibits good HER catalytic activity and stability in acidic electrolyte. When the current density is 10 mA cm−2, the overpotential and Tafel slope of Ni(OH)2/CoNi2S4/NF in 0.5 M H2SO4 solution is 124 mV and 84 mV dec−1, respectively, displaying better catalytic activity than Ni(OH)2/NiS/NF. The introduction of Co and synergistic effect of Co and Ni bimetallic sites promote the HER activity of the catalyst. In addition, the unique nanoflower structure of Ni(OH)2/CoNi2S4/NF catalyst increases the active area of the material, thus providing more catalytic active sites. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous zinc‐ion batteries (ZIBs) have aroused tremendous attention in energy storage system due to their high safety, eco‐friendliness, low cost, and for their good compatibility. Transition metal sulfides and selenides are considered to be promising cathodes for aqueous ZIBs owing to their unique layered structure and tunable interlayer spacing for the accelerating diffusion and reversible intercalation of hydrated Zn2+. However, their practical applications are severely impeded by some defects, such as the inferior electronic conductivity, large ion diffusion energy barrier, and bad cyclic stability. In this review, the various modification strategies including phase engineering, defect engineering, interlayer intercalation, in situ electrochemical oxidation, hybridization, doping effects, and surface modification are categorized and highlighted to improve the electrochemical properties of transition metal sulfides and selenides cathode materials, which are discussed and summarized corresponding to particular modification strategies. Finally, several key breakthrough directions such as mechanism exploration technology, electrolyte strategies, synergistic engineering, high‐capacity conversion‐type, high‐voltage cathode materials, and rocking‐chair type batteries are proposed to further push forward the development of aqueous ZIBs, to guide the design of advanced‐properties cathode materials for aqueous ZIBs. [ABSTRACT FROM AUTHOR]

Effective and inexpensive electrocatalysts are significant to improve the performance of oxygen evolution reaction. Facing the bottleneck of slow kinetics of oxygen evolution reaction, it is highly desirable to design the electrocatalyst with high activity, good conductivity, and satisfactory stability. In this work, nickel foam supported hierarchical Co9S8–Ni3S2 composite hollow microspheres were derived from in situ-generative MOF precursors and the subsequent sulfurization process by a simple two-step solvothermal method. The composite microspheres were directly grown on nickel foam without any binder, and nickel foam was used as the nickel source and support material. The morphology and constitution of the series self-supported electrodes were characterized by SEM, TEM, XRD, XPS, and Raman, respectively. The unique porous architecture enriched the electrode with sufficient active surface and helped to reactants and bubble evolved during electrochemical water oxidation. Through tuning the concentration of cobalt source and ligand, the content ratio of Co9S8 and Ni3S2 can be modulated. The heterostructures not only afford active interfaces between the phases but also allow electronic transfer between Co9S8 and Ni3S2. The optimized Co9S8-Ni3S2/NF-0.6 electrode with the highest electrochemical surface area and conductivity shows the best OER performance among the series electrodes in 1 M KOH solution. The overpotential of Co9S8-Ni3S2/NF-0.6 is only 233 mV when the current density is 10 mA cm−2, and corresponding Tafel slope is 116.75 mV dec−1. In addition, the current density of Co9S8-Ni3S2/NF-0.6 electrocatalyst hardly decreased during the 12 h stability measurement. Our approach in this work may provide the future rational design and synthesis of satisfactory OER electrocatalysts. [ABSTRACT FROM AUTHOR]

Rational designing of electrode materials is of great interest for improving the performance of battery-type supercapacitors. The bimetallic NiCo2S4 (NCS) and CoNi2S4 (CNS) electrode materials have received much attention for supercapacitors due to their rich electrochemical characteristics. However, the comparative electrochemical performances of NCS and CNS electrodes were never studied for supercapacitor application. In this work, microsphere-like bimetallic NCS and CNS structures were synthesized via a facile one-step hydrothermal method by controlling the molar ratio of Ni and Co precursors. The physico-chemical results confirmed that microsphere-like structures with cubic spinel-type NCS and CNS materials were successfully fabricated by this method. When tested as the supercapacitor electrode materials, both NCS and CNS electrodes exhibited battery-type behavior in a three-electrode configuration with outstanding electrochemical performances such as specific capacity, rate performance and cycle stability. Impressively, the CNS electrode delivered a high specific capacity of 430.1 C g−1 at 1 A g−1, which is higher than 345.9 C g−1 of the NCS electrode. Furthermore, the NCS and CNS electrodes showed a decent cycling stability with 75.70 and 84.70% capacity retention after 10,000 cycles. Benefiting from the electrochemical advantage of CNS microspheres, we fabricated a hybrid supercapacitor (HSC) device based on CNS microspheres (positive electrode) and activated carbon (AC, negative electrode), which is named as CNS//AC. The assembled CNS//AC HSC device showed a large energy density of 41.98 Wh kg−1 at a power density of 800.04 W kg−1 and displayed a remarkable cycling stability with a capacity retention of 91.79% after 15,000 cycles. These excellent electrochemical performances demonstrate that both bimetallic NCS and CNS microspheres may provide potential electrode materials for high performance battery-type supercapacitors. [ABSTRACT FROM AUTHOR]

In this study, we proposed a novel CoIn2S4/reduced graphene oxide (CoIn2S4/rGO) composite anode using a hydrothermal method. By introducing electronic-conductive reduced graphene oxide (rGO) to buffer the extreme volume expansion of CoIn2S4, we prevented its polysulfide dissolution during the lithiation/de-lithiation processes. After 100 cycles, the pristine CoIn2S4 electrode demonstrated poor cycle performance of only 120 mAh/g at a current density of 0.1 A/g. However, the composition-optimized CoIn2S4/rGO composite anode demonstrated a reversible capacity of 580 mAh/g for 100 cycles, which was an improvement of 4.83 times. In addition, the ex situ XRD measurements of the CoIn2S4/rGO electrode were conducted to determine the reaction mechanism and electrochemical behavior. These results suggest that the as-synthesized CoIn2S4/rGO composite anode is a promising anode material for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Due to the energy crisis by the excessive consumption of fossil fuels, Zinc–air batteries (ZABs) with high theoretical energy density have attracted people's attention. The overall performance of ZABs is largely determined by the air cathode catalyst. Therefore, it is necessary to develop high‐efficiency and low‐cost bifunctional catalysts to replace noble metal catalysts to promote the development of ZABs. Among a variety of cathode catalysts, TMS has become a research hotspot in recent years because of its better electrical conductivity than metal phosphides and metal oxides. In this work, we focus on the means of improving the electrocatalytic performance of transition‐metal sulfides (TMS) providing ideas for us to rationally design high‐performance catalysts. Furthermore, the performance improvement law between catalyst performance and ZABs is also discussed in this work. Finally, some challenges and opportunities faced in the research of TMS electrocatalysis are briefly proposed, and strategies for improving the performance of ZABs are prospected. [ABSTRACT FROM AUTHOR]

Transition metal chalcogenides (TMCs) are widely used as energy storage materials, however, most studies have neglected the reconstruction process that occurs during the operation. Thus, the intrinsic energy storage mechanism of TMCs and the identification and modulation of the reconstruction process are not adequately investigated. Herein, a proactive modulation strategy for reconstruction kinetics under nonoperating conditions is proposed, and a potentiostatic reconstruction method is developed. The effects of three electrochemical techniques of potentiostatic, cyclic voltammetry, and galvanostatic on reconstruction products are also revealed. Notably, under potentiostatic reconstruction, the needle‐like nickel‐cobalt sulfide precursor is transformed into columnar, polycrystalline, defect‐rich nickel‐cobalt hydroxysulfate (NCHS‐E), and the process is analyzed in detail by in situ and ex situ characterization. NCHS‐E exhibits an excellent electrochemical performance with a specific capacity of 5040 mC cm−2 at 1 mA cm−2 and capacity retention of 67.1% at 50 mA cm−2. Kinetic analysis and theoretical calculations show that NCHS‐E has fast charge transfer ability and low deprotonation energy, indicating a favorable energy storage pathway. This work proves the important potential of reconstruction kinetic modulation to optimize the structure and properties of the products and provides new insights into the mechanism of reconstruction occurrence. [ABSTRACT FROM AUTHOR]

Developing highly efficient and stable electrocatalysts for oxygen evolution reaction is of significant importance for applications in energy conversion and storage. Modulation of electronic structure of catalysts is critical for improving the performance of the resulting electrodes. Here, we report a facile way to engineer the electronic structure of Ni3FeS by coating a thin polyaniline (PANI) layer for improving electrocatalytic activity for overall water splitting. Experimental investigations unveil that the strong electronic interactions between the lone electron pairs of nitrogen in PANI and d orbitals of iron, nickel in Ni3FeS result in an electron-rich structure of Ni and Fe, and consequently optimize the adsorption and desorption processes to promote the OER activity. Remarkably, the resulting PANI/Ni3FeS electrode exhibited much enhanced OER performance with a low overpotential of 143 mV at a current density of 10 mA·cmâˆ'2 and good stability. Promisingly, coupled with the reported MoNi4/MoO2 electrode, the two-electrode electrolyzer achieved a current density of 10 mA·cmâˆ'2 with a relatively low potential of 1.55 V, and can generate oxygen and hydrogen bubbles steadily driven by a commercial dry battery, endowed the composite electrocatalyst with high potential for practical applications. [ABSTRACT FROM AUTHOR]

The MXene‐based heterostructures have recently attracted great interest as anode materials for sodium‐ion batteries (SIBs). Nonetheless, the complicated and harsh preparation process impedes their further commercialization. Herein, a novel, safe, low‐destructive, and universal strategy for rationally fabricating Ti3C2Tx MXene/transition metal sulfides (MSy) heterostructures is presented via Lewis acidic molten salts etching and subsequent in situ sulfurization treatment. Benefiting from the interfacial electronic coupling between highly conductive Ti3C2Tx MXene (Tx = O and Cl) and MSy (M = Fe, Co and Ni), the heterostructures possess remarkably improved electronic conductivity, promoted Na+ migration kinetics, and robust architectures. As a proof‐of‐concept demonstration, the Ti3C2Tx/FeS2 heterostructure demonstrates outstanding rate performance (456.6 mAh g−1 at 10 A g−1) and long‐term cyclic stability (474.9 mAh g−1 after 600 cycles at 5 A g−1) when serving as SIB anodes. Impressively, a sodium‐ion full battery with Ti3C2Tx/FeS2 anode delivers an excellent reversible capacity of 431.6 mAh g−1 after 1000 cycles at 3 A g−1. Moreover, the dual sodium storage behavior of Ti3C2Tx/FeS2 heterostructure and underlying mechanism toward exceptional electrochemical performance are revealed by comprehensive characterizations and theoretical calculations. Based on the full utilization of molten salt etching products, the present work offers new insight into the fabrication of MXene‐based heterostructures. [ABSTRACT FROM AUTHOR]

Highlights: The presence of Ti–O-Co bonds of the multi-dimensional composite frame separator (MCCoS/PP) promotes kinetics and enables bifunctional catalysis. The existence of MCCoS/PP cannot reduce the lithium-ion transference numbers. The Li–S battery with MCCoS/PP achieves super-high rate (368.6 mAh g−1 at 20C) and ultra-low capacity attenuation rate. The shuttle effect of soluble lithium polysulfides (LiPSs) between electrodes and slow reaction kinetics lead to extreme inefficiency and poor high current cycling stability, which limits the commercial application of Li–S batteries. Herein, the multi-dimensional composite frame has been proposed as the modified separator (MCCoS/PP) of Li–S battery, which is composed of CoS2 nanoparticles on alkali-treated MXene nanosheets and carbon nanotubes. Both experiments and theoretical calculations show that bifunctional catalytic activity can be achieved on the MCCoS/PP separator. It can not only promote the liquid–solid conversion in the reduction process, but also accelerate the decomposition of insoluble Li2S in the oxidation process. In addition, LiPSs shuttle effect has been inhibited without a decrease in lithium-ion transference numbers. Simultaneously, the MCCoS/PP separator with good LiPSs adsorption capability arouses redistribution and fixing of active substances, which is also beneficial to the rate performance and cycling stability. The Li–S batteries with the MCCoS/PP separator have a specific capacity of 368.6 mAh g−1 at 20C, and the capacity decay per cycle is only 0.033% in 1000 cycles at 7C. Also, high area capacity (6.34 mAh cm−2) with a high sulfur loading (7.7 mg cm−2) and a low electrolyte/sulfur ratio (7.5 μL mg−1) is achieved. [ABSTRACT FROM AUTHOR]

A study was made of the laws of transformation of the composition of high-viscosity oil under hydrothermal conditions in a porous medium of carbonate rock in the presence of transition metal sulfides formed in situ from an organically soluble precursor. It was determined that the catalysts provide a significant degree of degradation of asphaltenes. When using a catalyst containing nickel and iron in equal proportions, the viscosity becomes an order of magnitude lower than that of the initial oil and reaches a minimum value of 1360 mPa s. Owing to the presence of two different metals in the mixed catalyst makes, a wider range of carbon–heteroatom bonds in resins and asphaltenes of high-viscosity oil can be involved in in the conversion processes. Reducing the viscosity of oil under reservoir conditions makes it possible to increase oil recovery and decrease the carbon footprint of the produced oil due to an increase in the H : C atomic ratio. [ABSTRACT FROM AUTHOR]

Interfacial coupling strategy has allured extensive attention for the possibility to endow active electrode materials with superior performance. However, the design of strong coupling engineering with interfacial evolution during electrochemical processes is very challenging. Herein, inspired by the powerful robotic arms and density functional theory calculations, multiple functional groups identified with intense affinity to V atom are successfully grafted on carbon nanotubes (CNTs), thereby in situ building robust interfacial bonds (VOC and VC) to tightly anchor VS4 particles. The largely decreased band gaps and energy barriers show the fortified conductivity of VS4‐CNT heterostructure. Besides, the spacial confinement effect induced by interfacial linkages substantively enhances the mechanical properties to inhibit structural collapse, and restrains the dissolution of polysulfides as verified by molecular dynamics simulations, thus prolonging life span. Excellent energy density of 105.5 Wh kg–1 can be delivered after assembling full sodium‐ion capacitors (activated carbon//VS4‐CNT). Significantly, the reversible interfacial bonds confirmed by various ex situ characteristics during discharge/charge processes hold the key to remarkable sodium storage ability and prominent initial coulombic efficiency. More impressively, strong interfacial coupling effect can establish synergistic soft‐rigid integrated solid‐electrolyte interphase film, which is conducive to elevating the electrochemical performance of electrodes, convincingly constructing advanced sodium‐ion capacitors. [ABSTRACT FROM AUTHOR]

Summary: In this study, stimulating approach electrodeposition has been espoused to fabricate binder‐free electrodes of transition metal sulfides to achieve high electrochemical performance for energy storage devices. Here, the effect of Co and Cu with MnS has been scrutinized by gradually replacing Co with Cu concentration. The fabricated electrodes have been examined by FESEM to analyze the structural morphology of the material. Furthermore, electrochemical characterizations have been carried out for exploring the electrode performance which reveals that the S4 electrode (Cu0.75Co0.25MnS) exhibits the best performance as compared to contender electrodes. This electrode exhibits a high specific capacitance of 4800 F/g at 10 A/g current density with a smaller ESR value of 0.48 Ω. Additionally, the S4 electrode has been used as a cathode and activated carbon (AC) as an anode in assembling of supercapacitor device. Device S4//AC portrayed a maximum energy density of 118 Wh/kg with a power density of 960 W/kg at 1.2 A/g. The obtained results prophesied that the electrochemical performance of metal sulfides has been intensified by varying the concentration of material for superior electrochemical applications. [ABSTRACT FROM AUTHOR]

It is of great significance to develop highly conductive catalysts combined with bimetal sulfide hybrids for the hydrogen evolution reaction (HER). Herein, an efficient electrocatalyst with NiS2@MoS2 nanosheet arrays decorating carbon fiber paper (NiS2@MoS2/CFP nanocatalyst) is synthesized through a two-step solvothermal process. Carbon fiber paper provides great electrical conductivity and stability for NiS2@MoS2/CFP. Moreover, MoS2 nanosheets are covered on the surface of the NiS2 nanosheet via a simple two-step temperature control method in a solvothermal process. The growth of two-dimensional NiS2 nanosheets improves the loading area of MoS2, thus providing plenty of electroactive sites. The obtained NiS2@MoS2/CFP delivers a competitive overpotential of 95 mV at the benchmark current density of 10 mA cm–2 and achieves a small Tafel slope of 65 mV dec–1, indicating the great HER performance of the NiS2@MoS2/CFP nanocatalyst. Moreover, NiS2@MoS2/CFP shows robust stability after 24 h of continuous operation toward the HER in an acidic solution. This work provides a method to design high-efficient HER electrocatalysts through combining bimetal sulfide hybrids with a conductive substrate. [ABSTRACT FROM AUTHOR]

A facile two-step hydrothermal approach with post-sulfurization treatment was put forward to construct the mixed transition metal sulfide (NiCoZnS) with a high electrochemical performance. The different morphologies of NiCoZnS materials were successfully fabricated by adjusted the Ni/Co molar ratio of the NiCoZn(OH)F precursor. Moreover, the in situ phase transformation from the NiCoZn(OH)F phase to Zn0.76Co0.24S and NiCo2S4 phases and lattice defects via the S2âˆ' ion-exchange were determined by x-ray diffractometer, transmission electron microscopy and x-ray photoelectron spectroscopy techniques, which improved electric conductivity and interfacial active sites of the NiCoZnS, and so promoted the reaction kinetics. Significantly, the urchin-like NiCoZnS1/1 prepared at the Ni/Co molar ratio of 1.0 exhibited promising electrochemical performances with high capacitance and excellent cycling stability. Furthermore, the asymmetric device (NiCoZnS//AC) using NiCoZnS1/1 as the positive electrode had excellent supercapacitor performances with an energy density of 57.8 Wh·kgâ€"1 at a power density of 750 W·kgâ€"1 as well as a long cycle life (79.2% capacity retention after 10 000 cycles), indicating the potential application in high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Constructing sodium‐ion battery anodes with efficient ion/electron transport and high cycling stability is significantly promising for applications but still remains challenging. Here, "three‐in‐one" multi‐level design is performed to develop a carbon‐coated phosphorous‐doped MoS2 anchored on carbon nanotube paper (P‐MoS2@C/CNTP). The Na+ diffusion and electron transport, as well as the structural stability of the whole anode are simultaneously enhanced through the synergistically optimization of P‐MoS2@C/CNTP at atomic, nanoscopic, and macroscopic levels. Resulted from the multi‐level modification, the synergetic mechanism has been demonstrated by electrochemical measurement and theoretical calculation. As a result, the free‐standing P‐MoS2@C/CNTP anode presents a high rate performance (150 mA h g−1 at 5 A g−1) and a long cycling life (1 A g−1, 1200 cycles, 249 mA h g−1). This work provides a new approach to the design and fabrication of high‐performance conversion‐type electrode materials for rechargeable batteries application. [ABSTRACT FROM AUTHOR]

Transition metal sulfide is the most widely used cathode material for thermal batteries. The development of modern weapons requires higher quality and output of transition metal sulfide cathode materials. However, the current synthesis processes have some limitations for large‐scale industrial production due to the long production cycle and low production efficiency. Herein, by controlling the synthesis temperature and adopting a high‐temperature solid‐state method, sulfide FeS2, CoS2, and NiS2 with single‐phase and good crystalline structure are synthesized. This method with a simple production process, short production cycle, and high single output is suitable for engineering production. Hence, guidance for large‐scale industrial synthesis of pure phase FeS2, NiS2, and CoS2 is provided, embodying important scientific significance and application value. [ABSTRACT FROM AUTHOR]