Transition Metal Sulfides Research Articles

Recent advances in heteroatom doped transition metal sulfides for high-performance supercapacitors

Supercapacitors have been well focused on, due to the advantages of fast charging/discharging, high power density, long service time and safety. Electrode materials determine the performance of supercapacitors. Serving as a kind of battery-type materials, transition metal sulfides have been received more attentions for high redox activity and high specific capacity. Controllable synthesis of metal sulfides determines their microstructure and composition, which is the basis for developing new materials. Therefore, this review firstly introduces existing synthetic methods of transition metal sulfides, including hydrothermal/solvothermal method, template method, electrodeposition method, sol-gel method, co-precipitation method, exfoliation/intercalation method and solid state method. The preparation process, principle, advantages/shortages of each method and related examples are highlighted. Taking controllable synthesis as the main line, recent advances of heteroatom doped metal sulfides and their application in supercapacitors are introduced in the second section. According to the type of dopants, all doped metal sulfides are divided into two parts: nonmetal doped metal sulfides, including B, N, F, O, P and Se, and metal doped sulfides, including alkali metal, precious metal, rare earth metal and transition metal. The research progresses about materials preparation, structure feature and supercapacitance performance are summarized. At last, current issues and future prospects in the field of heteroatom doped metal sulfides are proposed. It is anticipated that the review will provide guiding ideas or strategies for developing high-performance metal sulfides electrode materials.

Three-dimensional allium flower-like iron-cobalt sulfide nanomaterials for high-performance supercapacitors

Supercapacitors with their improved performance in high energy density and long-term cycling stability have been the growing trend in recent years for fulfilling the demand of efficient energy storage systems. Herein, we report morphology-controlled three-dimensional (3D) Allium flower-like bimetallic iron-cobalt sulfide (3D-FeCoS AF) nanomaterials on nickel foam (NF) electrodes using a single-step electrochemical deposition strategy. The self-standing bimetallic 3D-FeCoS AF nanostructures show good performance towards the supercapacitance applications. The 3D-FeCoS AF nanostructures delivered a specific capacitance of ∼375.7 F g−1 at a current density of 1.0 A/g. The possible electron cloud delocalization among the FeS nanostructures through d-bands leads to the lower charge transport resistance at the 3D-FeCoS AF electrode–electrolyte interfaces and improved conductivity. The 3D-FeCoS AF electrode demonstrated excellent specific capacity and rate performance in a 2.0 M KOH electrolyte. Owing to their enormous electrochemical active surface area (ECSA) and distinctive 3D nanosheet morphology, the present 3D-FeCoS electrode holds great potential for the fabrication of additional transition metal sulfide materials for excellent supercapacitor performances. The findings of this study suggest promising prospects for the utilization of these materials in practical supercapacitance applications.

Embedment of Molybdenum Disulfide in Electrospun Fibers as an Integrated Cathode for Lithium-Ion Batteries

As an important component of LIBs, the electrode material plays a crucial role in determining the lithium (Li) storage performance in LIBs. In this study, MoS2 nano-flowers were synthesized using a one-pot hydrothermal method. The resulting MoS2 nano-flower, along with PAN, were used as raw materials for electrospinning. After annealing treatment, MoS2/(carbon nanofibers) CNFs nano-composites coated with carbon fibers were formed. The CNFs coating exhibited electrical conductivity and enhanced structural stability of the MoS2 due to the stabilizing effect of the carbon fibers. Additionally, electrochemical tests, including CV and GCD, indicated that the optimal capacity and cycling stability were achieved when the MoS2 content was 10%. The results indicated that the charge/discharge capacity of MoS2/CNFs-10% at a current density of 100 mA/g was ~650 mAh/g. After the cycling current returned to 100 mA/g, the current recovery was ~600 mAh/g, thereby indicating outstanding cycling stability. Accordingly, our fabrication technique and new insight could both widen design strategy of multicomponent composite electrode materials and promote the practical applications of the latest emerging transition metal sulfides in next-generation high-performance lithium-ion batteries.

Two-Dimensional ABS4 (A and B = Zr, Hf, and Ti) as Promising Anode for Li and Na-Ion Batteries.

Metal ion intercalation into van der Waals gaps of layered materials is vital for large-scale electrochemical energy storage. Transition-metal sulfides, ABS4 (where A and B represent Zr, Hf, and Ti as monolayers as anodes), are examined as lithium and sodium ion storage. Our study reveals that these monolayers offer exceptional performance for ion storage. The low diffusion barriers enable efficient lithium bonding and rapid separation while all ABS4 phases remain semiconducting before lithiation and transition to metallic states, ensuring excellent electrical conductivity. Notably, the monolayers demonstrate impressive ion capacities: 1639, 1202, and 1119 mAh/g for Li-ions, and 1093, 801, and 671 mAh/g for Na-ions in ZrTiS4, HfTiS4, and HfZrS4, respectively. Average voltages are 1.16 V, 0.9 V, and 0.94 V for Li-ions and 1.17 V, 1.02 V, and 0.94 V for Na-ions across these materials. Additionally, low migration energy barriers of 0.231 eV, 0.233 eV, and 0.238 eV for Li and 0.135 eV, 0.136 eV, and 0.147 eV for Na make ABS4 monolayers highly attractive for battery applications. These findings underscore the potential of monolayer ABS4 as a superior electrode material, combining high adsorption energy, low diffusion barriers, low voltage, high specific capacity, and outstanding electrical conductivity.

Investigations of Mechanisms Leading to Capacity Differences in Li/Na/K-Ion Batteries with Conversion-Type Transition-Metal Sulfides Anodes.

Conversion-type transition-metal sulfides (CT-TMSs) have been extensively studied as the anode of Li/Na/K-ion batteries due to their high theoretical capacity. An issue with the use of the material in the battery is that a large capacity difference is commonly observed. However, the underlying mechanism leading to the problem is still unknown. Here, the large capacity difference mechanisms of CT-TMSs anodes in the Li/Na/K-ion storage are elucidated, which arises from the difference in conversion degree and size of conversion products. Specifically, the increase in ionic radius will cause the increase in insertion-reaction ion diffuse energy barrier and conversion-reaction Gibbs free energies of phase transformation to decrease reaction kinetics, which causes a decrease in conversion degree and an increase in size of conversion products, thus leading to reduction in capacity. The increase in size and the decrease in the amount of conversion products inevitably reduce the amount of spin-polarized electrons injection into Fe and corresponding ions storage amount into sulfides during the ion-electron decoupling storage, thus reducing the capacity. The research clarifies the capacity difference mechanisms of CT-TMSs anodes in Li/Na/K storage, providing valuable insights for designing Li/Na/K storage high-capacity anodes.

Nanocubic transition metal sulfides (FeMn)S2@NC synthesised by MOFs facily for supercapacitors

Transition metal sulfides have attracted considerable attention as supercapacitor materials due to their favorable electrochemical properties and low cost. However, challenges such as slow electrochemical kinetics and significant volume changes still persist. In this study, (FeMn)S2@NC nanocubes were synthesized by utilizing MOFs as precursors, employing a solution method to encapsulate Ppy around the periphery, followed by a one-step annealing process. The electrode prepared from (FeMn)S2@NC exhibits a high specific capacitance of 1154 F/g at 1 A/g and retains a specific capacitance of 777 F/g even at a high current density of 5 A/g. After 8000 charge-discharge cycles at 10 A/g, it still maintains a high capacity retention of 94% and close to 100% Coulombic efficiency. The (FeMn)S2@NC//AC capacitor exhibite excellent electrochemical performance with good rate capability and practical value 39.73F/g at 1A/g, 38.26F/g at 2A/g, 26.67F/g at 5A/g, 20.53F/g at 7A/g and 14F/g at 10A/g. Electrochemical testing at 5A/g show 93.3% high capacity retention after 180,000 cycles.

Super-hybrid transition metal sulfide nanoarrays of NiS nanoparticle/WS2 nanosheet/Ni3S4 nanoparticle with abundant plane- and edge-type active interfaces for robust all-pH hydrogen evolution

Transition metal sulfides (TMSs) are primitive composition of biocatalysts that are active for molecular hydrogen production. The development of non-precious TMSs with appropriate spatial ordering has great potentials to contribute high-level hydrogen generation. Herein, super-hybrid transition metal sulfide nanoarrays of NiS nanoparticle/WS2 nanosheet/Ni3S4 nanoparticle (Super-NiS/WS2/Ni3S4) with high spatial ordering and abundant plane- and edge-type WS2-NiS and WS2-Ni3S4 heterointerfaces were elaborately constructed though manipulating the sequential dissociation of phosphotungstic acid (PW12) as W precursor and nickel foam as Ni precursor in one pot. When evaluated for the electrocatalytic hydrogen evolution reaction (HER), the Super-NiS/WS2/Ni3S4 only required overpotentials of 57, 95, and 151 mV to drive HER in alkaline, acid, and neutral media, respectively, and presented favorable reaction kinetics and test stability. The theoretical and experimental results verify the adsorption and dissociation of water molecules are preferential on WS2-plane-related heterointerfaces. The Gibbs free energy (ΔGH*) analysis indicated the WS2-plane-NiS interface is thermodynamically optimal for HER. Moreover, the collaborations of the abundant plane- and edge-type active interfaces, the open nanosheet-based vertical array, and the phosphorus doping in Super-NiS/WS2/Ni3S4 strengthen mass transport and electron transfer in electrocatalysis. The polyoxometalates-based synthetic strategy will inspire the new vision for the rational design and construction of advanced functional materials.

Al2O3-induced phase conversion regulation from hexagonal FeS to orthorhombic FeS for enhancing the Li-ion accommodation ability

Cycling lifespan/stability is one of the most important limitations for multivalent transition metal sulfides (TMSs) used in secondary batteries. However, the chaos reaction of TMSs is an important obstacle that restricts their electrochemical stability in all-enclosed batteries. Herein, taking FeS anode and lithium-ion batteries as the example, the phase-lithiation correlation is studied through TEM and DFT analysis. It's found that the pristine hexagonal FeS converts to tetragonal FeS phase accompanied by severe and rapid capacity decay. However, it converts to orthorhombic FeS with enhanced capacity and nice lifespan when introducing trace amount amorphous Al2O3 upon FeS power's surface. DFT calculations further reveal that Al2O3 induces the phase conversion from low-acitve tetragonal FeS to high-active orthorhombic FeS, which promotes the lithiation-delithiation reversibility and stability. Based on the above result, it is expected to provide useful guidelines for the in-situ structure engineering of TMSs-based anodes in all-enclosed secondary batteries.

Synthesis of α‐NiS Decorated Fe3S4 Nanohybrid Composite and Its Heterogeneous Fenton Catalysis for Dye Degradation

AbstractGreigite (Fe3S4) and millerite (NiS) are important transition metal sulfides that exhibit light‐driven Fenton catalytic activity. In absence of light, they show limited activity. To utilize these properties without relying on light, we synergized these sulfides to prepare a composite Fe3S4–NiS (FSNS). Under fixed reaction conditions, the composite demonstrated excellent Fenton activity, degrading 93% of fast green dye (FG) and 98.1% of eriochrome black T dye (EBT) within a short reaction time. The mechanism involves electron transfer from the reduced sulfur state (S2−) in both NiS and Fe3S4 to the higher oxidation states of the metal ions viz. Fe3+and Ni3+ to facilitate the redox cyclization in the Fenton process. The catalyst showed high stability for five cyclical tests by recovering it from solution with an external magnet.

Efficient H2 evolution over MoS2-NiS2/g-C3N4 S-scheme photocatalyst with NiS2 as electron mediator

Low-cost transition metal sulfides are commonly utilized as photocatalysts for H2 production owing to their exceptional conductivity and superior specific surface area. In this study, MoS2-NiS2 nanoflowers with multidimensional space structure was obtained through the sulphuration reaction between S2- and NiMoO4 under Kirkendall effect during hydrothermal reaction. Subsequently, MoS2-NiS2 was loaded on the surface of g-C3N4 nanosheets using a solvent self-assembly strategy to form 3D MoS2-NiS2/g-C3N4 heterojunctions. The experimental results demonstrate that the H2 production rate of 20 wt% MoS2-NiS2/g-C3N4 reaches 22153 μmol·g-1·h-1 under a 300 W Xe lamp irradiation, which is 59.5 and 201.4-folds than MoS2-NiS2 and g-C3N4, and surpasses 20 wt% MoS2/g-C3N4 (211 μmol·g-1·h-1) and 20 wt% NiS2/g-C3N4 (6183 μmol·g-1·h-1). The XPS and Superoxide radical capture experiments demonstrate that the charge transfer between MoS2-NiS2 and g-C3N4 follows the S-scheme route, and NiS2 functions as an electron mediator, facilitating the transfer of electrons from MoS2 to g-C3N4 to consume the holes, which enhances the efficiency of H2 evolution reaction on g-C3N4. Furthermore, the S-scheme heterojunction of MoS2-NiS2/g-C3N4 with the multidimensional geometric structure can provide abundant active sites for catalytic reactions, this presents a promising approach for the development of cost-effective and high-performance g-C3N4-based heterojunctions. This work offers distinctive perspectives on the trajectory of renewable H2 energy development.

A novel method for engineering active sites through in-situ and chemical deposition: Robust Ni3S2/MoS2/WS2 heterostructures for efficient water splitting in an alkaline medium

To develop compact and efficient electrolysers, use a bi-functional electrocatalysts capable of performing both the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER) at the same temperature, pressure, and pH. To develop ternary transition metal sulphides for OER and HER with superior performance. Herein, reported a sheet-like heterostructures electrode made of was fabricated on nickel foam using a simple hydrothermal method. The surface morphology and electrochemical active sites of the binder-free NMWS(1:1) heterostructures bi-functional catalyst were analysed in a 1.0 M KOH electrolyte medium to attain a lower overpotential for both OER (290 mV @ 10 mA cm−2) and HER (165 mV @ 10 mA cm−2). Electrochemical NMWS (1:1) studies show that the purported efficiencies are due to increased oxygen vacancies, interfacial bonds, and surface sulfur sites in the heterostructures were analysed through XPS, and HR-TEM. Furthermore, a dual-electrode in an electrolyser cell, the proposed heterostructures electrode achieved a current density of 10 mA cm−2 yet retained a remarkably low cell voltage of 1.73 V. The Ni3S2/MoS2/WS2 heterostructures stabilizes, which helps maintain LSV's low current degradation rate (CDR). The efficient water splitting has been calculated using turnover frequency and Tafel plot.

Photodual-Responsive Anthracene-Based 2D Covalent Organic Framework for Optoelectronic Synaptic Devices.

To facilitate the development of efficient neuromorphic perception and computation, it is crucial to explore optoelectronic synaptic devices that integrate perceptual and computational capabilities. Various materials such as oxide semiconductors, conjugated organic polymers, transition metal sulfides, perovskite materials, and metal nanoparticles, along with their composites, are utilized in constructing these devices. However, optoelectronic synaptic devices based on 2D covalent organic frameworks (COFs) is rarely reported. In this study, an anthracene-based 2D COF (COF-DaTp) film is prepared using a room-temperature interface-confined strategy and utilized it as the active layer in an optoelectronic synaptic device with an Al/COF-DaTp/ITO configuration. The device demonstrated dual optoelectronic modulation, exhibiting significant optoelectronic resistive switching in response to light pulses, achieving 32 photoconductive states. Moreover, it exhibited history-dependent memristive behavior in voltage scans and electrical pulses, with a comparable diversity of 32 conductive states. The photodual-responsive properties of the COF-DaTp-based synaptic device enable it to simultaneously perform optical sensing and basic image denoising and recognition tasks, significantly enhancing recognition accuracy and reducing the number of training epochs compared to datasets without noise mitigation. This work opens the door for the application of 2D COF-based optoelectronic synaptic devices in visual computational processing.

Recent Research Advancements in Carbon Fiber‐Based Anode Materials for Lithium‐Ion Batteries

Energy consumption is a critical element in human evolution, and rapid advances in science and technology necessitate adequate energy. As human society evades, the advancement of energy storage components has become critical in addressing societal challenges. Lithium‐ion batteries (LIBs) are promising candidates for future extensive use as optimal energy storage devices. However, the current limitations of LIBs pose a challenge to their continued dominance. Researchers are constantly exploring new materials to enhance the performance of LIBs, and carbon fiber (CF) is a dominant contender in this pursuit. The high electrical conductivity of carbon‐based materials benefits the battery system by facilitating efficient electron transfer and improving overall performance. CF‐based materials provide enhanced energy storage capacity and cycling stability in LIBs. Progress in carbon‐based materials has resulted in electrodes with increased surface areas, enabling greater rates of charging and discharging. In addition, the exceptional corrosion resistance of CF ensures the durability and robustness of LIBs. A comprehensive review is carried out on the correlation between the material's structure and its electrochemical performance, with a special emphasis on the uses of pure carbon fibers, transition metal oxides, sulfides, and MXene carbon‐based transition metal compounds in LIBs.

Design and Synthesis of Sb-Doped CuS@C Hollow Nanocubes as Efficient Anode Materials for Sodium-Ion Battery.

Copper sulfide has received widespread attention for application as anode materials in sodium-ion batteries due to their potent capabilitiess and eco-friendly properties. However, it is a challenge to achieve a high rate capability and long cycle stability owing to the heterogeneous transfer of sodium ions during charge-discharge, the interior poor electron conductivity and repeated volumetric expansion of copper sulfide. In this study, Sb-doped copper sulfide hollow nanocubes coated with carbon shells (Sb-CuS@C) was designed and constructed as anode nanomaterials in sodium-ion batteries. Thanks to the intrinsic good electron conductivity and chemical stability of carbon shells, Sb-CuS@C possesses a higher overall electron transfer as anode material, avoids agglomeration and structural destruction during the cycling. As a result, the synthesized Sb-CuS@C achieved an excellent reversible capacity of 595 mA h g-1 after 100 cycles at 0.5 A g-1 and a good rate capability of 340 mA h g-1 at a higher 10 A g-1. DFT calculations clarify that the uniformly doped Sb would act as active sodiophilic nucleation sites to help adsorbing sodium-ion during discharging and leading uniform sodium deposition. This work provides a new insight into the structural and componential modification for common transition-metal sulfides towards application as anode materials in sodium-ion battery.

Efficient synthesis of FeVO4 cathode materials in high specific energy thermal batteries

Thermal batteries, which are essential for applications in extreme environments, require cathode materials with high specific energy and thermal stability. In this study, metal vanadates were synthesized via a chemical precipitation method followed by high-temperature sintering, offering a promising alternative for conventional transition metal sulfides. The synthesized FeVO4 exhibits phase purity, while copper and nickel vanadates show secondary phases, indicating challenges in achieving pure-phase synthesis of metal vanadates. Electrochemical evaluations reveal that FeVO4 cathode delivers an initial discharge voltage of 2.65 V and a specific capacity of 190 mAh/g. Whereas the FeVO4/CNTs composite cathode demonstrates an enhanced specific capacity of 253.66 mAh/g, which is attributed to prolonged discharge plateaus. Phase evolution studies indicated that FeVO4 reacts with molten salts during high-temperature discharge, leading to the formation of Fe2O3 and Li0.3V2O5, which contribute to the observed stepwise discharge behavior. These results emphasize the importance of optimizing the interactions between cathode materials and molten salts to improve the performance of high-temperature thermal batteries.

Spherical NiS2/Ni17S18–C accelerates ion transport and enhances kinetics for lithium-sulfur battery host material

Transition metal sulfides exhibit notable catalytic activity and possess a high theoretical specific capacity as host materials in lithium-sulfur batteries. However, their restricted conductivity and sluggish Li+ transport hinder their broader application. In this research, we developed a Ni-based metal-organic framework (Ni-MOF) using nitrogen-containing benzimidazole and coupled it with a highly conductive carbon nanotube (CNT) to form NixSy (NiS2–Ni17S18)–C/CNT. The N-doped carbon skeleton derived from the MOF enhances the adsorption and chemical anchoring of polysulfides, while the even distribution of NiS2 and Ni17S18 enhances the redox reaction kinetics. Additionally, the conductive CNT networks aid in rapid electron transport, resulting in improved sulfur utilization. Consequently, the NixSy-C/CNT@S electrode demonstrates an impressive initial specific capacity of 1468 mAh g−1 at 0.2C and maintains 904.4 mAh g−1 after 200 cycles. Moreover, NixSy-C/CNT@S displays exceptional cycle stability, with a capacity retention of 76.20 % and a decay rate of only 0.05 % per cycle after 500 cycles at 0.5C. This study paves the way for the development and synthesis of cathode materials with outstanding electrochemical performance in LSBs.

Zinc cobalt sulfide with carbon (graphene oxide and CNT) based nanocomposite as positive electrode for asymmetric coin cell supercapacitors

Abstract The world dependence on portable electronic devices has increased the demand for high-performance energy storage devices. The use of transition metal sulfides as faradaic electrode materials for electrochemical energy storage is rapidly increasing due to their high energy density. Herein Zinc Cobalt Sulfide (ZCS) with graphene oxide (GO) and carbon nanotubes (CNT) were used to create an interconnected ZCS composite network using a solvothermal technique. The materials were characterized by utilizing XRD, FT-Raman, TGA, FESEM/EDX, XPS, and BET. The electrochemical performance of the materials was examined using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). The prepared electrodes exhibited both pseudocapacitor behavior and double-layer capacitor behavior, indicating the hybrid nature. Furthermore, All the electrode ZCS, ZCS/GO, ZCS/CNT, and ZCS/GO/CNT electrodes demonstrated higher capacitance behavior, with values of 420, 551, 585 and 811 F g−1 at 1 A/g. Among these ZCS/GO/CNT electrode exhibits outstanding electrochemical properties, with a notable retention of 81.08% at 10 Ag−1 because Combining ZCS nanoparticles with interconnected GO and CNT provides excellent electronic conductivity and stability. The assembled ZCS/GO/CNT//graphene oxide asymmetric coin cell (ACC) supercapacitor showed a high energy density of 33.3 Wh kg–1 at a power density of 624 W kg–1. The 3D nanostructure of ZCS/GO/CNT/Graphene oxide has great potential for developing foldable energy storage devices.

Enhanced Structural VS4 Grown onto Hollow Carbon Mesoporous Spheres via Surficial Bonding for High Cycling Stability in Sodium-Ion Batteries.

Transition metal sulfides are recognized as an excellent alternative to sodium ion anodes ascribed to the outstanding theoretical capacity. The unique crystal arrangement of VS4 gives it exceptional theoretical capacity, despite challenges like insufficient electrical conductivity and undesirable volume expansion. Herein, a novel stabilized anode featuring a distinctive 3D hollow spherical structure is proposed, providing a simple strategy to synthesize such anodes for VS4-HCMSs bonded via C-O-S and V-O-C interfaces. The kinetic investigations and density functional theory reveal that the unique structure connected by interfacial bonds enhances Na+ transport rate and charge transfer efficiency, while carbon greatly mitigates the volume expansion. Unsurprisingly, the VS4-HCMSs exhibit an impressive first-cycle Coulombic efficiency of 91.31% and an ultrahigh reversible capacity of 612 mAh g-1 after 300 cycles at 0.5 A g-1, even exhibit the reversible capacity of 498.8 mAh g-1 after 1000 cycles at 5 A g-1. Additionally, the NaFePO4//VS4-HCMSs full cell is cycled for 200 cycles at 0.2 C and powered the light-emitting diodes for up to 30 minutes afterward. Overall, this work enhances the conductivity and stability of the material by combining VS4 with hollow carbon mesoporous spheres through interfacial bonding, offering an efficient strategy to anode materials in sodium-ion batteries.

Hydrothermal synthesis of rGO and MnCoS composite for enhanced supercapacitor application

Nanostructured materials incorporating transition metal sulfides have demonstrated considerable potential across various applications, particularly in the realms of energy production and storage. Sulfide-based material preparation is a challenging and costly procedure that requires a high temperature and reducing atmosphere. This work reports that manganese cobalt sulfide (MCS) and reduced graphene oxide composite manganese cobalt sulfide (rMCS) were successfully prepared through a hydrothermal method. Various characterization techniques were employed to analyze the prepared materials, including X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, and X-ray photoelectron spectroscopy. In a three-electrode system, MCS and rMCS electrodes exhibit an excellent specific capacitance of 1695 and 1925 F g−1 at 1 A g−1 current density respectively. MCS delivers the capacitance retention of 99% and rMCS exhibits the capacitance retention of 100% capacitance retention over 5000 consecutive cycles. The constructed asymmetric supercapacitor electrode (rMCS//rGO) exhibits the energy and power density of 64 Wh kg−1 at 799 W kg−1, respectively with outstanding cyclic stability of 97.4% even after 10,000 cycles. The exceptional electrochemical properties of MCS with rGO composite electrode indicate that they would make an outstanding electrode material for cutting-edge energy storage devices.

Ultrathin Copper Monosulfide Films for an Optically Semitransparent, Highly Selective Ammonia Chemosensor.

Transition-metal sulfides are emerging as promising materials for chemiresistive gas sensors─a field still dominated by semiconducting metal oxides. Despite the availability of materials with tunable electronic, optical, physical, and chemical properties, few studies have moved beyond synthesis to provide strategies for enhancing gas sensing performance through material modification. Here, we present a simple, scalable synthetic strategy for developing an optically semitransparent, flexible NH3 gas sensor with a highly uniform, ultrathin CuS (covellite) active sensing layer. The optical and chemical properties of the CuS were precisely controlled near the percolation threshold of thin-film formation by varying key experimental parameters such as the Cu film thickness (<10 nm) and the sulfurization time (∼90 s) under ambient conditions. Experimental and computational studies of CuS and its NH3 sensing characteristics identify key physicochemical properties. The controlled surface chemistry and morphology of the ultrathin CuS layer demonstrate its effectiveness in functional NH3 sensing devices, which achieve a calculated detection limit of 1.38 ppm for NH3 gas at 150 °C, along with exceptional mechanical robustness and optical semitransparency in the visible-light spectrum.