S4 Nanosheets Research Articles

Entropy enhancement drived high initial Coulombic efficiency and capacity integrated SnS2 nanosheets for lithium-ion batteries

Layer SnS2 has been garnered significant attention for next-generation lithium-ion batteries (LIBs), due to its abundant resources and high theoretical capacity. However, the low initial Coulombic efficiency, large volume expansion and structural degradation have significantly hindered its application in LIBs. Herein, the layer Sn0.7(MoFeCoNiV)0.3S2 nanosheets (HE3-SnS2) grown on the conductive substrate carbon cloth (CC) is synthesized by one-step hydrothermal method. Multiple elements doping strategy not only increases the conformational entropy which will improve the structural stability of during cycling, but also enlarges the interlayer spacing which benefits for lithium-ion transfer. As a result, the additive-free integrated CC@HE3-SnS2 electrode achieves a high reversible specific capacity of 1204.9 mAh g−1 with a high initial Coulombic efficiency of 94.7 % at 1C, and maintains 1011.4 mAh g−1 after 100 cycles. Specifically, the CC@HE3-SnS2 anode exhibits excellent rate capability of 670.8 mAh g−1 at 10C. Moreover, the full cell based on CC@HE3-SnS2 anode and commercial LiCoO2 cathode displays a stable capacity retention of 862.7 mAh g−1 after 100 cycles at 1C. The entropy-stabilized SnS2-based anode with high initial Coulombic efficiency and rate capability has a competitive candidate for LIBs.

High average power passively Q-switched 2-μm laser with Mo0.5W0.5S2 as a saturable absorber

Two-dimensional transition metal dichalcogenides (TMDs) with remarkable nonlinear properties, like MoS2/WS2 and the ternary compound Mo0.5W0.5S2, have attracted a lot of attention. The field has made use of the nonlinear characteristics of all-solid-state lasers. The liquid-phase exfoliation method was used in this work to create Mo0.5W0.5S2 nanosheets. At 2 μm, the nonlinear absorption characteristics of Mo0.5W0.5S2 were examined and the results showed a saturation intensity of 1.56 MW/cm2 and a modulation depth of 5.2%. A high-power passively Q-switched Tm:YAP laser with an average output power of 3.20 W and a brief pulse width of 633 ns was produced using the Mo0.5W0.5S2 nanosheet as a saturable absorber. According to the results, Mo0.5W0.5S2 has the potential to produce pulsed lasers with high peak and average powers that operate at about 2 μm.

Bifunctional Ni Foam Supported TiO2 @Ni3 S2 core@shell Nanorod Arrays for Boosting Electrocatalytic Biomass Upgrading and H2 Production Reactions.

Replacing traditional oxygen evoltion reaction(OER) with biomass oxidation reaction (BOR) is an advantageous alternative choice to obtain green hydrogen energy from electrocatalytic water splitting. Herein, a novel of extremely homogeneous Ni3 S2 nanosheets covered TiO2 nanorod arrays are in situ growth on conductive Ni foam (Ni/TiO2 @Ni3 S2 ). The Ni/TiO2 @Ni3 S2 electrode exhibits excellent electrocatalytic activity and long-term stability for both BOR and hydrogen evolution reaction (HER). Especially, taking glucose as a typical biomass, the average hydrogen production rate of the HER-glucose oxidation reaction (GOR) two-electrode system reached 984.74µmol h-1 , about 2.7 times higher than that of in a common HER//OER two-electrode water splitting system (365.50µmol h-1 ). The calculated power energy saving efficiency of the GOR//HER system is about 13% less than that of the OER//HER system. Meanwhile, the corresponding selectivity of the value-added formic acid produced by GORreaches about 80%. Moreover, the Ni/TiO2 @Ni3 S2 electrode also exhibits excellent electrocatalytic activity on a diverse range of typical biomass intermediates, such as urea, sucrose, fructose, furfuryl alcohol (FFA), 5-hydroxymethylfurfural (HMF), and alcohol (EtOH). These results show that Ni/TiO2 @Ni3 S2 has great potential in electrocatalysis, especially in replacing OER reaction with BOR reaction and promoting the sustainable development of hydrogen production.

A Low-Temperature Synthetic Route Toward a High-Entropy 2D Hexernary Transition Metal Dichalcogenide for Hydrogen Evolution Electrocatalysis.

High-entropy (HE) metal chalcogenides are a class of materials that have great potential in applications such as thermoelectrics and electrocatalysis. Layered 2D transition-metal dichalcogenides (TMDCs) are a sub-class of high entropy metal chalcogenides that have received little attention to date as their preparation currently involves complicated, energy-intensive, or hazardous synthetic steps. To address this, a low-temperature (500 °C) and rapid (1h) single source precursor approach is successfully adopted to synthesize the hexernary high-entropy metal disulfide (MoWReMnCr)S2 . (MoWReMnCr)S2 powders are characterized by powder X-ray diffraction (pXRD) and Raman spectroscopy, which confirmed that the material is comprised predominantly of a hexagonal phase. The surfaceoxidation states and elemental compositions are studied by X-ray photoelectron spectroscopy (XPS) whilst the bulk morphology and elemental stoichiometry with spatial distribution is determined by scanning electron microscopy (SEM) with elemental mapping information acquired fromenergy-dispersive X-ray (EDX) spectroscopy. The bulk, layered material is subsequently exfoliated to ultra-thin, several-layer 2D nanosheets by liquid-phase exfoliation (LPE). The resultingfew-layer HE (MoWReMnCr)S2 nanosheets are found to contain a homogeneous elemental distribution of metals at the nanoscale by high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) with EDX mapping. Finally, (MoWReMnCr)S2 is demonstrated as a hydrogen evolution electrocatalyst and compared to 2H-MoS2 synthesized using the molecular precursor approach. (MoWReMnCr)S2 with 20% w/w of high-conductivity carbon black displays a low overpotential of 229mV in 0.5 M H2 SO4 to reach a current density of 10mA cm-2 , which is much lower than the overpotential of 362mV for MoS2 . From density functional theory calculations, it is hypothesised that the enhanced catalytic activity is due to activation of the basal plane upon incorporation of other elements into the 2H-MoS2 structure, in particular, the first row TMs Cr and Mn.

Z-Scheme Modulated Charge Transfer on InVO4 @ZnIn2 S4 for Durable Overall Water Splitting.

The charge transfer within heterojunction is crucial for the efficiency and stability of photocatalyst for overall water splitting (OWS). Herein, InVO4 nanosheets have been employed as a support for the lateral epitaxial growth of ZnIn2 S4 nanosheets to produce hierarchical InVO4 @ZnIn2 S4 (InVZ) heterojunctions. The distinct branching heterostructure facilitates active site exposure and mass transfer, further boosting the participation of ZnIn2 S4 and InVO4 for proton reduction and water oxidation, respectively. The unique Z-scheme modulated charge transfer, visualized by simulation and in situ analysis, has been proved to promote the spatial separation of photoexcited charges and strengthen the anti-photocorrosion capability of InVZ. The optimized InVZ heterojunction presents improved OWS (153.3µmolh-1 g-1 for H2 and 76.9µmolh-1 g-1 for O2 ) and competitive H2 production (21090µmolh-1 g-1 ). Even after 20 times (100h) of cycle experiment, it still holds more than 88% OWS activity and a complete structure.

Surface Spin Enhanced High Stable NiCo2 S4 for Energy-Saving Production of H2 from Water/Methanol Coelectrolysis at High Current Density.

Nickel based materials are promising electrocatalysts to produce hydrogen from water in alkaline media. However, the stability is of great challenge, limiting its practical material functions. Herein, a new technique for electro-deposition flower-like NiCo2 S4 nanosheets on carbon-cloth (CC@NiCo2 S4 ) is proposed for energy-saving production of H2 from water/methanol coelectrolysis at high current density by constructing array architectures and regulating surface magnetism. The optimized and fine-tuned magnetism on the surface of the electrochemical in situ grown CC@NiCo2 S4 nanosheet array result in (0 1 -1) surface universally exposed, high catalytic activity for methanol electrooxidation, and long-term stability at high current density. X-ray photoelectron spectroscopy in combination of density functional theory calculations confirm the valence electron states and spin of d electrons for the surface of NiCo2 S4 , which enhance the surface stability of catalysts. This technology may be utilized to alter the surface magnetism and increase the stability of Ni-based electrocatalytic materials in general.

Enhanced photoresponse of InxMo1-xS2 (X = 0.05 and 0.1) nanosheets for PEC type photodetector

Transition metal chalcogenides (TMDCs) have great potential in the field of solid state photodetectors and photoelectrochemical (PEC) type photodetector owing to high carrier mobility and suitable energy band gap. Two dimensional MoS2, most intensively investigated member of TMDCs, has shown excellent photoresponsivity in the visible range owing to excitonic transition and suitable electronic structure. Herein, we demonstrate the PEC photodetector based on InxMo1-xS2 nanosheets. High yield liquid phase exfoliation techniques have been employed for the synthesis of InxMo1-xS2 nanosheets. InxMo1-xS2 nanosheets have hexagonal lattice structure with highly crystalline behavior and X-ray diffraction confirms the doping of indium in 2H–MoS2. PEC type detectors show 582 μA/W and 107 μA/W photoresponsivity for In0.05Mo0.95S2 and In0.1Mo0.9S2 nanosheets by optimized concentration of indium. Present investigation advocates the significant development in the field of opto-electronics and photoelectrochemical cells for generation clean energy.

Low-Coordination Single Au Atoms on Ultrathin ZnIn2 S4 Nanosheets for Selective Photocatalytic CO2 Reduction towards CH4.

Selective CO2 photoreduction to hydrocarbon fuels such as CH4 is promising and sustainable for carbon-neutral future. However, lack of proper binding strengths with reaction intermediates makes it still a challenge for photocatalytic CO2 methanation with both high activity and selectivity. Here, low-coordination single Au atoms (Au1 -S2 ) on ultrathin ZnIn2 S4 nanosheets was synthesized by a complex-exchange route, enabling exceptional photocatalytic CO2 reduction performance. Under visible light irradiation, Au1 /ZnIn2 S4 catalyst exhibits a CH4 yield of 275 μmol g-1 h-1 with a selectivity as high as 77 %. As revealed by detailed characterizations and density functional theory calculations, Au1 /ZnIn2 S4 with Au1 -S2 structure not only display fast carrier transfer to underpin its superior activity, but also greatly reduce the energy barrier for protonation of *CO and stabilize the *CH3 intermediate, thereby leading to the selective CH4 generation from CO2 photoreduction.

Mo‐Doped Sulfur‐Vacancy‐Rich V1.11S2 Nanosheets for Efficient Hydrogen Evolution

AbstractHigh‐performance low‐cost hydrogen evolution electrocatalysts are urgently demanded for hydrogen production by water splitting. Herein, we report that an efficient defect engineering strategy, NaBH4 treatment, was employed to promote the HER activity of pre‐synthesized Mo‐doped V1.11S2 nanosheets. The abundant sulfur vacancies enable Mo‐doped V1.11S2 petaloid nanosheets with a low overpotential of 160 mV and a small Tafel slope of 46.2 mV dec−1 at 10 mA cm−2 to drive the HER, as well as excellent long‐term stability in 0.5 mol L−1 H2SO4. The outstanding electrocatalytic performance can be attributed to the large electrochemical surface area and low charge transfer resistance.

Cation/Anion Dual-Vacancy Pair Modulated Atomically-Thin Sex -Co3 S4 Nanosheets with Extremely High Water Oxidation Performance in Ultralow-Concentration Alkaline Solutions.

The density functional theory calculation results reveal that the adjacent defect concentration and electronic spin state can effectively activate the CoIII sites in the atomically thin nanosheets, facilitating the thermodynamic transformation of *O to *OOH, thus offering ultrahigh charge transfer properties and efficiently stabilizing the phase. This undoubtedly evidences that, for metal sulfides, the atom-scale cation/anion vacancy pair and surface electronic spin state can play a great role in enhancing the oxygen evolution reaction. Inspired by the theoretical prediction, interconnected selenium (Se) wired ultrathin Co3 S4 (Sex -Co3 S4 ) nanosheets with Co/S (Se) dual-vacancies (Se1.0 -Co3 S4 -VS/Se -VCo ) pairs are constructed by a simple approach. As an efficient sulfur host material, in an ultralow-concentration KOH solution (0.1 m), Se1.0 -Co3 S4 -VS/Se -VCo presents outstanding durability up to 165 h and a low overpotential of 289.5mV at 10mA cm-2 , which outperform the commercial Co3 S4 nanosheets (NSs) and RuO2 . Moreover, the turnover frequency of Se1.0 -Co3 S4 -VS/Se -VCo is 0.00965 s-1 at an overpotential of 0.39V, which is 5.7 times that of Co3 S4 NSs, and 5.8 times that of commercial RuO2 . The finding offers a rational design strategy to create the multi-defect structure in catalysts toward high-efficiency water electrolysis.

Bimetallic Multi-Level Layered Co-NiOOH/Ni3 S2 @NF Nanosheet for Hydrogen Evolution Reaction in Alkaline Medium.

Development of efficient non-noble metal catalysts for water splitting is of great significance but challenging due to the sluggish kinetics of the hydrogen evolution reaction (HER) in alkaline medium. Herein, a bimetallic multi-level layered catalytic electrode composed of Ni3 S2 nanosheets with secondary Co-NiOOH layer of 3D porous and free-standing cathode in alkaline medium is reported. This integrated synergistic catalytic electrode exhibits excellent HER electrocatalytic performance. The resultant Ni0.67 Co0.33 /Ni3 S2 @NF electrode displays the highest HER activity with only overpotentials of 87 and 203mV to afford current densities of 10 and 100 mA·cm-2 , respectively, and its Tafel slope is 80 mV·dec-1 . The chronopotentiometry operated at high current density of 50 mA·cm-2 shows negligible deterioration, indicating better stability of Ni0.67 Co0.33 /Ni3 S2 @NF electrode than Pt/C (20wt.%). Such a desirable catalytic performance is attributed to the modification of physical and electronic structure that exposes abundant active sites and improves the intrinsic catalytic activity toward HER, which is also confirmed by electrochemically active surface area and X-ray photoelectron spectroscopy analysis. This work provides a strong support for the rational design of high-performance bimetallic electrodes for industrial water splitting.

Ternary Transition Metal Dichalcogenides for High Power Vector Dissipative Soliton Ultrafast Fiber Laser

Abstract2D ternary transition metal dichalcogenides (TMDCs) have been studied widely by researchers from the fields of nanotechnology to materials science because of the extraordinary chemical/physical characteristics, and significant potential in nanoscale device applications. Here, the application of NbxRe(1−x)S2 nanosheets in ultrafast photonics is studied. The few‐layer NbxRe(1−x)S2 nanosheets are fabricated through liquid phase exfoliation method and a NbxRe(1−x)S2‐microfiber device is constructed by depositing these nanosheets onto the tapered region of a microfiber. After incorporating the NbxRe(1−x)S2‐microfiber saturable absorber (SA) into a net positive dispersion Er‐doped fiber (EDF) laser cavity, the generation of stable dissipative soliton pulses with a pulse duration of 1.03 ps proved as polarization‐locked vector solitons upon further study. With pump power growing to 900 mW, the average output power increases to 116.9 mW without pulse splitting. Besides, the pulse width can be compressed to 149.6 fs outside the cavity by using a single‐mode fiber. Compared with previous works based on 2D materials‐based saturable absorbers, the NbxRe(1−x)S2‐based mode‐locked fiber laser proposed herein, reveals superior comprehensive performance.

Scalable Synthesis of Tungsten Disulfide Nanosheets for Alkali‐Acid Electrocatalytic Sulfion Recycling and H2 Generation

AbstractWS2 nanosheets hold great promise for a variety of applications yet faces a grand challenge in terms of large‐scale synthesis. We report a reliable, scalable, and high‐yield (>93 %) synthetic strategy to fabricate WS2 nanosheets, which exhibit highly desirable electrocatalytic properties toward both the alkaline sulfion (S2−) oxidation reaction (SOR) and the acidic hydrogen evolution reaction (HER). The findings prompted us to develop a hybrid alkali‐acid electrochemical cell with the WS2 nanosheets as bifunctional electrode catalysts of alkaline anodic SOR and acidic cathodic HER. The proof‐of‐concept device holds promise for self‐power or low‐electricity electrolytic H2 generation and environmentally friendly recycling of sulfion with enhanced electron utilization efficiency.

Scalable Synthesis of Tungsten Disulfide Nanosheets for Alkali-Acid Electrocatalytic Sulfion Recycling and H2 Generation.

WS2 nanosheets hold great promise for a variety of applications yet faces a grand challenge in terms of large-scale synthesis. We report a reliable, scalable, and high-yield (>93 %) synthetic strategy to fabricate WS2 nanosheets, which exhibit highly desirable electrocatalytic properties toward both the alkaline sulfion (S2- ) oxidation reaction (SOR) and the acidic hydrogen evolution reaction (HER). The findings prompted us to develop a hybrid alkali-acid electrochemical cell with the WS2 nanosheets as bifunctional electrode catalysts of alkaline anodic SOR and acidic cathodic HER. The proof-of-concept device holds promise for self-power or low-electricity electrolytic H2 generation and environmentally friendly recycling of sulfion with enhanced electron utilization efficiency.

Spatially Controlled Preparation of Layered Metallic-Semiconducting Metal Chalcogenide Heterostructures.

Spatially controlled preparation of heterostructures composed of layered materials is important in achieving interesting properties. Although vapor-phased deposition methods can prepare vertical and lateral heterostructures, liquid-phased methods, which can enable scalable production and further solution processes, have shown limited controllability. Herein, we demonstrate by using wet chemical methods that metallic Sn0.5Mo0.5S2 nanosheets can be deposited epitaxially on the edges of semiconducting SnS2 nanoplates to form SnS2/Sn0.5Mo0.5S2 lateral heterostructures or coated on both the edges and basal surfaces of SnS2 to give SnS2@Sn0.5Mo0.5S2 core@shell heterostructures. They also showed good light-to-heat conversion ability due to the metallic property of Sn0.5Mo0.5S2. In particular, the core@shell heterostructure showed a higher photothermal conversion efficiency than the lateral counterpart, largely due to its randomly oriented and polycrystalline Sn0.5Mo0.5S2 layers with larger interfacing area for multiple internal light scattering.

Ni(OH)2 Templated Synthesis of Ultrathin Ni3 S2 Nanosheets as Bifunctional Electrocatalyst for Overall Water Splitting.

Ultrathin nickel (Ni)-based sulfide nanosheets have been reported as excellent electrocatalysts for overall water splitting; however, the uncontrollability over thickness due to the nonlayered structure still hampers its practical application. Herein, a simple topochemical conversion strategy is employed to synthesize cobalt-doped Ni3 S2 (Co-Ni3 S2 ) ultrathin nanosheets on Ni foam. The Co-Ni3 S2 nanosheets are controlled synthesized by using Co-Ni(OH)2 ultrathin nanosheets as templates with anneal and sulfurization treatment, showing exceptional electrocatalytic activity. This template-assisted method can also be applied to obtain Ni, NiO, and NiPx nanosheets, providing a universal strategy to synthesize ultrathin nanosheets of nonlayered materials. The overall water splitting of this Co-Ni3 S2 ultrathin nanosheets achieves a low voltage of 1.54V at a current density of 10mA cm-2 and high durability in 1 m KOH, comparable to the best performance of electrochemical water splitting ever reported. The detailed structural transformation of Ni-based sulfides in the catalytic process and its mechanism are further explored both experimentally and theoretically.

3D-Stretched Film Ni3 S2 Nanosheet/Macromolecule Anthraquinone Derivative Polymers for Electrocatalytic Overall Water Splitting.

For the first time, anew polymer electrode AQS/S is prepared by compositing Ni3 S2 nanosheets and macromolecular anthraquinone derivative (AQD) supported on nickel foam with flying colors. The AQS/S exhibits high crystalline structure and abundant S defects. Density of state calculation shows that AQD has stable internal bonding and easy external bonding with metals, conducive to the dispersion of metal reaction sites, ensuring excellent activity and high stability.Under 1.0 m KOH solution, ultralow overpotentials of 62 and 133 mV at 10 mA cm-2 on AQS/S for hydrogen evolution reaction and on activated AQS/S (A-AQS/S) for oxygen evolution reaction, respectively, are achieved. 100 h chronopotentiometry and the cyclic voltammetry tests show that catalysts have high durability. The AQS/S‖A-AQS/S two-electrode system is also found to have good electrocatalytic activity for 1.43V to get 10mA cm-2 in overall water splitting, better than the state-of-the-art 20% Pt/C‖RuO2 combination.

Ultrafast Photonics of Ternary RexNb(1-x)S2 in Fiber Lasers.

Two-dimensional (2D) transition metal chalcogenides (TMCs) become more attractive upon addition of a third element owing to their unique structure and remarkable physical and chemical properties, which endow these materials with considerable potential for applications in nanoscale devices. In this work, a RexNb(1-x)S2-based saturable absorber (SA) device for ultrafast photonics applications is studied. The device is assembled by placing RexNb(1-x)S2 nanosheets with a thickness of 1-3 nm onto a microfiber to increase their compatibility with an all-fiber laser cavity. The prepared RexNb(1-x)S2-based device exhibits a modulation depth of 24.3%, a saturation intensity of 10.1 MW/cm2, and a nonsaturable loss of 28.5%. Furthermore, the RexNb(1-x)S2-based device is used to generate ultrashort pulses in an erbium-doped fiber (EDF) laser cavity. At a pump power of 260 mW, the EDF laser operates in a conventional soliton mode-locked region. The pulse width is 285 fs, and the repetition frequency is 61.993 MHz. In particular, the bound-state soliton mode-locking operation is successfully obtained in a pump power range of 300-900 mW. The bound-state pulses are formed by doubling identical solitons with a temporal interval of 0.8 ps. The output power is as high as 47.9 mW, and the repetition frequency is 123.61 MHz. These results indicate that the proposed RexNb(1-x)S2-based SAs have comparable properties to currently used 2D SAs and provide a basis for their application in the field of ultrafast photonics.

Spatially Separating Redox Centers and Photothermal Effect Synergistically Boosting the Photocatalytic Hydrogen Evolution of ZnIn2 S4 Nanosheets.

Spatially separated loading of reductive and oxidative cocatalysts is a useful strategy for expediting charge separation and surface reaction kinetics, which are two key factors for determining the photocatalytic efficiency. However, loading the spatial separation of dual cocatalysts on a 2D photocatalyst is still a great challenge. Herein, decorating the spatial separation of oxidative and reductive cocatalysts on ZnIn2 S4 nanosheets is realized by designing a ternary Co9 S8 @ZnIn2 S4 @PdS (CS@ZIS@PS) hollow tubular core-shell structure. Particularly, Co9 S8 and PdS functionally serve as the reduction and oxidation cocatalysts, respectively. Experimental results confirm that the spatial separation of Co9 S8 and PdS cocatalysts not only efficiently improve charge separation and accelerate surface reduction-oxidation kinetics, but also generate a photothermal effect to further enhance charge transfer and surface reaction kinetics. As a result, the optimized CS@ZIS@PS yields a remarkable H2 evolution rate of 11407µmol g-1 h-1 , and the apparent quantum efficiency reaches 71.2% at 420nm, which is one of the highest values among ZnIn2 S4 so far. The synergistic effect of spatially separated dual cocatalysts and photothermal effect may be applied to other 2D materials for efficient solar energy conversion.

Preparation and characterization of Sn-doped In2.77S4 nanosheets as a visible-light-induced photocatalyst for tetracycline degradation

Semiconductor photocatalysis technology is a promising method to solve the antibiotics pollution in water. Herein, a series of Sn-doped In2.77S4 (Sn-In2.77S4) hybrid photocatalysts for tetracycline degradation have been fabricated via a one-step hydrothermal process. The analytic results exhibit that doping Sn can improve the photocatalytic performance of In2.77S4 nanosheets under the visible light illumination and the doping amount obviously affects the photocatalytic performance of the samples. When the theoretical molar ratio of Sn4+ to In3+ is 0.04:1 (4%), the photocatalytic efficiency of the Sn-In2.77S4 photocatalyst exhibits the highest of 87.4% in comparison with 39.2% of pure In2.77S4 in 20 min. Moreover, its band gap energy has been reduced to 1.56 eV from 1.75 eV and the light absorption range has been broadened. The transfer rate and separation efficiency of photo-generated electron and hole pairs of the samples have also been enhanced. In addition, the holes play a leading role in the photocatalytic degradation process.