Fabrication of zero to three dimensional nanostructured molybdenum sulfides and their electrochemical and photocatalytic applications

Recent advances in catalytic oxidation of VOCs by two-dimensional ultra-thin nanomaterials

Catalytic oxidation, an end-of-pipe treatment technology for effectively purifying volatile organic compounds (VOCs), has received widespread attention. The crux of catalytic oxidation lies in the development of efficient catalysts, with their optimization necessitating a comprehensive analysis of the catalytic reaction mechanism. Two-dimensional (2D) ultra-thin nanomaterials offer significant advantages in exploring the catalytic oxidation mechanism of VOCs due to their unique structure and properties. This review classifies strategies for regulating catalytic properties and typical applications of 2D materials in VOCs catalytic oxidation, in addition to their characteristics and typical characterization techniques. Furthermore, the possible reaction mechanism of 2D Co-based and Mn-based oxides in the catalytic oxidation of VOCs is analyzed, with a special focus on the synergistic effect between oxygen and metal vacancies. The objective of this review is to provide valuable references for scholars in the field.

Recent Advances of Transition Metal Dichalcogenides-Based Materials for Energy Storage Devices, in View of Monovalent to Divalent Ions

The fast growth of electrochemical energy storage (EES) systems necessitates using innovative, high-performance electrode materials. Among the various EES devices, rechargeable batteries (RBs) with potential features like high energy density and extensive lifetime are well suited to meet rapidly increasing energy demands. Layered transition metal dichalcogenides (TMDs), typical two dimensional (2D) nanomaterial, are considered auspicious materials for RBs because of their layered structures and large specific surface areas (SSA) that benefit quick ion transportation. This review summarizes and highlights recent advances in TMDs with improved performance for various RBs. Through novel engineering and functionalization used for high-performance RBs, we briefly discuss the properties, characterizations, and electrochemistry phenomena of TMDs. We summarised that engineering with multiple techniques, like nanocomposites used for TMDs receives special attention. In conclusion, the recent issues and promising upcoming research openings for developing TMDs-based electrodes for RBs are discussed.

Research Progress of Hydrogen Production Technology and Related Catalysts by Electrolysis of Water

As a clean and renewable energy source for sustainable development, hydrogen energy has gained a lot of attention from the general public and researchers. Hydrogen production by electrolysis of water is the most important approach to producing hydrogen, and it is also the main way to realize carbon neutrality. In this paper, the main technologies of hydrogen production by electrolysis of water are discussed in detail; their characteristics, advantages, and disadvantages are analyzed; and the selection criteria and design criteria of catalysts are presented. The catalysts used in various hydrogen production technologies and their characteristics are emphatically expounded, aiming at optimizing the existing catalyst system and developing new high-performance, high-stability, and low-cost catalysts. Finally, the problems and solutions in the practical design of catalysts are discussed and explored.

Roadmap and Direction toward High-Performance MoS2 Hydrogen Evolution Catalysts

MoS₂ intrinsically show Pt-like hydrogen evolution reaction (HER) performance. Pristine MoS₂ displayed low HER activity, which was caused by low quantities of catalytic sites and unsatisfactory conductivity. Then, phase engineering and S vacancy were developed as effective strategies to elevate the intrinsic HER performance. Heterojunctions and dopants were successful strategies to improve HER performance significantly. A couple of state-of-the-art MoS₂ catalysts showed HER performance comparable to Pt. Applying multiple strategies in the same electrocatalyst was the key to furnish Pt-like HER performance. In this review, we summarize the available strategies to fabricate superior MoS₂ HER catalysts and tag the important works. We analyze the well-defined strategies for fabricating a superior MoS₂ electrocatalyst, propose complementary strategies which could help meet practical requirements, and help people design highly efficient MoS₂ electrocatalysts. We also provide a brief perspective on assembling practical electrochemical systems by high-performance MoS₂ electrocatalysts, apply MoS₂ in other important electrocatalysis reactions, and develop high-performance two-dimensional (2D) dichalcogenide HER catalysts not limited to MoS₂. This review will help researchers to obtain a better understanding of development of superior MoS₂ HER electrocatalysts, providing directions for next-generation catalyst development.

Sulfurization of MoO3 in the Chemical Vapor Deposition Synthesis of MoS2 Enhanced by an H2S/H2 Mixture

The typical layered transition metal dichalcogenide (TMDC) material, MoS₂, is considered a promising candidate for the next-generation electronic device due to its exceptional physical and chemical properties. In chemical vapor deposition synthesis, the sulfurization of MoO₃ powders is an essential reaction step in which the MoO₃ reactants are converted into MoS₂ products. Recent studies have suggested using an H₂S/H₂ mixture to reduce MoO₃ powders in an effective way. However, reaction mechanisms associated with the sulfurization of MoO₃ by the H₂S/H₂ mixture are yet to be fully understood. Here, we perform quantum molecular dynamics (QMD) simulations to investigate the sulfurization of MoO₃ flakes using two different gaseous environments: pure H₂S precursors and a H₂S/H₂ mixture. Our QMD results reveal that the H₂S/H₂ mixture could effectively reduce and sulfurize the MoO₃ reactants through additional reactions of H₂ and MoO₃, thereby providing valuable input for experimental synthesis of higher-quality TMDC materials.

A review of the α-Fe2O3 (hematite) nanotube structure: recent advances in synthesis, characterization, and applications

α-Fe2O3 nanotubes are exceptional one-dimensional transition metal oxide materials with low density, large surface area, promising electrochemical and photoelectrochemical properties, which are widely investigated in lithium-ion batteries, photoelectrochemical devices, gas sensors, and catalysis. They have drawn significant attention to the fields of energy storage and conversion, and environmental sensing and remediation due to the increase in the global energy crisis and environmental pollution. Many efforts have been made toward controlling the morphology or impurity doping to improve the intrinsic properties of α-Fe2O3 nanotubes. In this review, we introduce the synthesis methods and physicochemical properties of α-Fe2O3 nanotubes. The fabrication conditions, which are important for the physicochemical properties of materials, are also listed to describe the synthesis processes. Furthermore, the development and breakthrough of various applications in batteries, supercapacitors, photoelectrochemical devices, environmental remediation, and sensors are systematically reviewed. Finally, some of the current challenges and future perspectives for α-Fe2O3 nanotubes are discussed. We believe that this timely and critical mini-review will stimulate extensive studies and attract more attention, further improving the development of the α-Fe2O3 (hematite) nanotube structure.

Ni-modified MoS2 nanoflake arrays with stepped sites on carbon nanotubes for efficient hydrodesulfurization of coal-to-liquid fuel

Carbon nanotube (CNT)-supported Ni-modified MoS₂ catalysts with ultra-high loading were synthesized with the assistance of citric acid. The morphology of the nanoflake arrays could be controlled to give abundant stepped sites, which favored the hydrogenation desulfurization pathway of dibenzothiophene. The catalyst exhibited excellent performance and stability for hydrodesulfurization of model oil and coal-to-liquid fuel.

Electronic properties and low lattice thermal conductivity (κl) of mono-layer (ML) MoS2: FP-LAPW incorporated with spin–orbit coupling (SOC)

This paper focuses on the electronic and thermoelectric properties of monolayer MoS₂.

Hydrogen evolution reaction from bare and surface-functionalized few-layered MoS2 nanosheets in acidic and alkaline electrolytes

Hydrogen is considered as an ideal and sustainable energy carrier because of its high energy density and carbon-free combustion. Electrochemical water splitting is the only solution for uninterrupted, scalable, and sustainable production of hydrogen without carbon emission. However, a large-scale hydrogen production through electrochemical water splitting depends on the availability of earth-abundant electrocatalysts and a suitable electrolyte medium. In this article, we demonstrate that hydrogen evolution reaction (HER) performance of electrocatalytic materials can be controlled by their surface functionalization and selection of a suitable electrolyte solution. Here, we report syntheses of few-layered MoS₂ nanosheets, NiO nanoparticles (NPs), and multiwalled carbon nanotubes (MWCNTs) using scalable production methods from earth-abundant materials. Magnetic measurements of as-produced electrocatalyst materials demonstrate that MoS₂ nanoflakes are diamagnetic, whereas surface-functionalized MoS₂ and its composite with carbon nanotubes have strong ferromagnetism. The HER performance of the few-layered pristine MoS₂ nanoflakes, MoS₂/NiO NPs, and MoS₂/NiO NPs/MWCNT nanocomposite electrocatalysts are studied in acidic and alkaline media. For bare MoS₂, the values of overpotential (η₁₀) in alkaline and acidic media are 0.45 and 0.54 V, respectively. Similarly, the values of current density at 0.5 V overpotential are 27 and 6.2 mA/cm² in alkaline and acidic media, respectively. The surface functionalization acts adversely in the both alkaline and acidic media. MoS₂ nanosheets functionalized with NiO NPs also demonstrated excellent performance for oxygen evolution reaction with anodic current of ~60 mA/cm² and Tafel slope of 78 mVdec^-1 in alkaline medium.

Fabricating ferromagnetic MoS2-based composite exposed to simulated sunlight for sodium storage

A light- and magnetic stimuli-responsive MoS₂ composite electrode material is designed and evaluated as an anode material of sodium ion batteries. Through the assistance of simulated sunlight, suppressed dendritic sodium growth, buffered volume deformation, promoted electrochemical reaction kinetics, and improved structural stability are simultaneously achieved. Meanwhile, ferroelectric polarization enhances the separation efficiency of photogenerated carriers. The collisions among electrons are dramatically decreased; in turn, the thermal stability of the battery is improved via the tailored orientation of active materials. A stable protective solid-state electrolyte interface film is formed via the photogenerated electrons and the magnetohydrodynamics effect, depressing the growth of sodium dendrites. The porous three-dimensional heterostructure is conducive for promoting transmission of charges and the diffusion of ions, effectively reducing the local current density of metals, further inhibiting the growth of sodium dendrites during deposition and peeling processes. Density functional theoretical calculations also verify that the fabricated MoS₂ composite possesses intensified electron density, and exhibits fast reaction kinetics in repeated cycles and lowered sodium adsorption energy. The optical field and the rational magnetic fabrication technology can fundamentally solve the bottleneck problems restricting the development of batteries, mitigating the energy crisis.

MoS2 nanotubes loaded with TiO2 nanoparticles for enhanced electrocatalytic hydrogen evolution

Efficient and stable non-precious metal catalysts composed of earth-abundant elements are crucial to the hydrogen evolution reaction (HER) in high-energy conversion efficiency. Herein, TiO₂/MoS₂-NTs catalyst, in which the MoS₂ nanotubes were loaded with TiO₂ nanoparticles, have been synthesized via a facile solvothermal and hydrothermal method. The as-prepared TiO₂/MoS₂-NTs electrocatalyst demonstrated enhanced electrocatalytic hydrogen evolution performance compared with MoS₂-NTs. Electrochemical measurements reveal the overpotential and Tafel slope of as-prepared TiO₂/MoS₂-NTs are −0.21 V and 42 mV dec⁻¹. The HER improvement is proposed to be attributed to the increased edge sites results from the interfaces and synergic effect between TiO₂ nanoparticles and MoS₂ nanotubes.

Polarization curves of TiO₂, MoS₂-NTs and TiO₂/MoS₂-NTs in 0.5 M H₂SO₄ solution.

Defect Healing in Layered Materials: A Machine Learning-Assisted Characterization of MoS2 Crystal Phases

Monolayer MoS₂ is an outstanding candidate for a next-generation semiconducting material because of its exceptional physical, chemical, and mechanical properties. To make this promising layered material applicable to nanostructured electronic applications, synthesis of a highly crystalline MoS₂ monolayer is vitally important. Among different types of synthesis methods, chemical vapor deposition (CVD) is the most practical way to synthesize few- or mono-layer MoS₂ on the target substrate owing to its simplicity and scalability. However, synthesis of a highly crystalline MoS₂ layer remains elusive. This is because of the number of grains and defects unavoidably generated during CVD synthesis. Here, we perform multimillion-atom reactive molecular dynamics (RMD) simulations to identify an origin of the grain growth, migration, and defect healing process on a CVD-grown MoS₂ monolayer. RMD results reveal that grain boundaries could be successfully repaired by multiple heat treatments. Our work proposes a new way of controlling the grain growth and migration on a CVD-grown MoS₂ monolayer.

Facile synthesis of few-layer MoS2 in MgAl-LDH layers for enhanced visible-light photocatalytic activity

A new photocatalyst, few-layer MoS₂ grown in MgAl-LDH interlayers (MoS₂/MgAl-LDH), was prepared by a facile two-step hydrothermal synthesis. The structural and photocatalytic properties of the obtained material were characterized by several techniques including powder X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL) and UV-vis absorption spectroscopy. The MoS₂/MgAl-LDH composite showed excellent photocatalytic performance for methyl orange (MO) degradation at low concentrations (50 mg L⁻¹ and 100 mg L⁻¹). Furthermore, even for a MO solution concentration as high as 200 mg L⁻¹, this composite also presented high degradation efficiency (>84%) and mineralization efficiency (>73%) at 120 min. The results show that the MoS₂/MgAl-LDH composite has great potential for application in wastewater treatment.

Few-layer MoS₂ was successfully grown in MgAl-LDH layers, utilizing the “space-confining” effect. The composite completed degraded 50 mg L⁻¹ and 100 mg L⁻¹ methyl orange (MO) solutions in 45 min and 105 min, respectively.

Unveiling the Structure of MoS x Nanocrystals Produced upon Laser Fragmentation of MoS2 Platelets

Transition-metal dichalcogenide MoS₂ nanostructures have attracted tremendous attention due to their unique properties, which render them efficient nanoscale functional components for multiple applications ranging from sensors and biomedical probes to energy conversion and storage devices. However, despite the wide application range, the possibility to tune their size, shape, and composition is still a challenge. At the same time, the correlation of the structure with the optoelectronic properties is still unresolved. Here, we propose a new method to synthesize various morphologies of molybdenum sulfide nanocrystals, on the basis of ultrashort-pulsed laser fragmentation of MoS₂ platelets. Depending on the irradiation conditions, multiple MoS _x morphologies in the form of nanoribbons, nanospheres, and photoluminescent quantum dots are obtained. Besides the detailed structural analysis of the various crystals formed, the structure-property relation is investigated and discussed.

Graphene/transition metal dichalcogenides hybrid supercapacitor electrode: status, challenges, and perspectives

Supercapacitors, based on fast ion transportation, are among the most promising energy storage solutions that can deliver fast charging-discharging within seconds and exhibit excellent cycling stability. The development of a good electrode material is one of the key factors in enhancing supercapacitor performance. Graphene (G), an allotrope of carbon that consists of a single layer of carbon atoms arranged in a hexagonal lattice, elicits research attention among scientists in the field of energy storage due to its remarkable properties, such as outstanding electrical conductivity, good chemical stability, and excellent mechanical behavior. Furthermore, numerous studies focus on 2D materials that are analogous to graphene as electrode supercapacitors, including transition metal dichalcogenides (TMDs). Recently, scientists and researchers are exploring TMDs because of the distinct features that make 2D TMDs highly attractive for capacitive energy storage. This study provides an overview of the structure, properties, synthesis methods, and electrochemical performance of G/TMD supercapacitors. Furthermore, the combination of G and TMDs to develop a hybrid structure may increase their energy density by introducing an asymmetric supercapacitor system. We will also discuss the future prospect of this system in the energy field.

Synergistic effect of MoS2 and diamond nanoparticles in electrochemical sensors: determination of the anticonvulsant drug valproic acid

The authors describe an electrochemical sensor based on the use of diamond nanoparticles (DNPs) and molybdenum disulfide (MoS₂) platelets. The sensor was applied to the voltammetric determination of the anticonvulsant valproic acid which was previously derivatized with ferrocene. The MoS₂ platelets were obtained by an exfoliation method, and the DNPs were directly dispersed in water and subsequently deposited on a glassy carbon electrode (GCE). The sensor response was optimized in terms of the solvent employed for dispersing the MoS₂ nanomaterial and the method for modifying the GCE. Sensors consisting of a first layer of MoS₂ dispersed in ethanol/water and a second layer of DNPs give better response. The single steps of sensor construction were characterized by atomic force microscopy and electrochemical impedance spectroscopy. The differential pulse voltammetric response of the GCE (measured at +0.18 V vs. Ag/AgCl) was compared to that of sensors incorporating only one of the nanomateriales (DNPs or MoS₂). The formation of a hybrid MoS₂-DNP structure clearly improves performance. The GCE containing both nanomaterials exhibits high sensitivity (740 µA ⋅ mM^-1 ⋅ cm^-2), a 0.27 μM detection limit, and an 8% reproducibility (RSD). The sensor retained 99% of its initial response after 45 days of storage. Graphical abstract Electrochemical sensor by co-immobilization of MoS₂ and diamond nanoparticles (DNP). The formation of a hybrid MoS₂-DNP structure enhances the performance of the sensor towards valproic acid derivatized with a ferrocene group, when compared with sensors incorporating only DNP or MoS₂.

Electrocatalysts for Hydrogen Evolution in Alkaline Electrolytes: Mechanisms, Challenges, and Prospective Solutions

Hydrogen evolution reaction (HER) in alkaline medium is currently a point of focus for sustainable development of hydrogen as an alternative clean fuel for various energy systems, but suffers from sluggish reaction kinetics due to additional water dissociation step. So, the state-of-the-art catalysts performing well in acidic media lose considerable catalytic performance in alkaline media. This review summarizes the recent developments to overcome the kinetics issues of alkaline HER, synthesis of materials with modified morphologies, and electronic structures to tune the active sites and their applications as efficient catalysts for HER. It first explains the fundamentals and electrochemistry of HER and then outlines the requirements for an efficient and stable catalyst in alkaline medium. The challenges with alkaline HER and limitation with the electrocatalysts along with prospective solutions are then highlighted. It further describes the synthesis methods of advanced nanostructures based on carbon, noble, and inexpensive metals and their heterogeneous structures. These heterogeneous structures provide some ideal systems for analyzing the role of structure and synergy on alkaline HER catalysis. At the end, it provides the concluding remarks and future perspectives that can be helpful for tuning the catalysts active-sites with improved electrochemical efficiencies in future.

Enhanced sunlight-driven photocatalytic property of Mg-doped ZnO nanocomposites with three-dimensional graphene oxide/MoS2 nanosheet composites

Graphene oxide (GO) has been the focus of attention as it can enhance the photocatalytic activity of semiconductors due to its large specific surface area and remarkable optical and electronic properties. However, the enhancing effect is not ideal because of its easy self-agglomeration and low electronic conductivity. To improve the enhancing effect of GO for ZnO, three-dimensional GO/MoS₂ composite carriers (3D GOM) were prepared by electrostatic interactions and then, Mg-doped ZnO nanoparticles (MZ) were supported on the surface of 3D GOM by utilizing the layer-by-layer assembly method. Compared with GO/Mg-ZnO composite (GOMZ), the resultant three-dimensional GO/MoS₂/Mg-ZnO composite (GOMMZ) exhibited excellent photocatalytic performance due to the effective synergistic effect between GO and MoS₂ sheet, and its degradation rate was nearly 100% within 120 min of exposure to visible light; this degradation rate was nearly 8 times higher than that of the GOMZ composite. Moreover, the introduction of the MoS₂ sheet intensified the photocurrent density of the GOMZ composite and endowed it with optical memory ability.

Graphene oxide (GO) has been the focus of attention as it can enhance the photocatalytic activity of semiconductors due to its large specific surface area and remarkable optical and electronic properties.

One-step synthesis of MnS/MoS2/C through the calcination and sulfurization of a bi-metal–organic framework for a high-performance supercapacitor and its photocurrent investigation

Using a bi-metallic Mn/Mo-MOF as a precursor, a MnS/MoS₂/C hybrid material was synthesized with a high specific capacitance of 1162 F g⁻¹ at 0.5 A g⁻¹ in 2 M KOH solution due to the synergetic effects of the individual components and their exposed active sites.

Pseudocapacitive-battery-like behavior of cobalt manganese nickel sulfide (CoMnNiS) nanosheets grown on Ni-foam by electrodeposition for realizing high capacity

Hierarchical interconnected nanosheets (HIN) of cobalt manganese nickel sulfide (CoMnNiS) were synthesized on Ni foam by a simple and economical electrodeposition technique for energy storage application. Sulfonated thin nanosheets of Co, Mn and Ni provide stability of chemical activity, surface functionalization and surface reactivity to the electrode. The fabricated electrode shows a specific capacity of 257.4 mA h g⁻¹ (at 2.5 A g⁻¹), measured by galvanostatic charging–discharging (GCD). Both diffusion and capacitive mechanisms in the sulfide layer contribute to the high electrical conductivity. Asymmetric devices CoMnNiS/NiCuO and CoMnNiS/CNT (CNT = carbon nanotubes) were fabricated, providing a maximum operating voltage of 1.7 V and 1 V, specific capacity of 20.8 and 50.8 mA h g⁻¹, and energy density of 8.4 and 6.3 W h kg⁻¹ corresponding to a power density of 985 and 211 W kg⁻¹, respectively, at a current density of 0.5 and 0.63 A g⁻¹. These results demonstrate a novel material for application in energy storage devices as an electrode.

Hierarchical interconnected nanosheets (HIN) of cobalt manganese nickel sulfide (CoMnNiS) were synthesized on Ni foam by a simple and economical electrodeposition technique for energy storage application.

Reactivity of Sulfur Molecules on MoO3 (010) Surface

Two-dimensional and layered MoS₂ is a promising candidate for next-generation electric devices due to its unique electronic, optical, and chemical properties. Chemical vapor deposition (CVD) is the most effective way to synthesize MoS₂ monolayer on a target substrate. During CVD synthesis, sulfidation of MoO₃ surface is a critical reaction step, which converts MoO₃ to MoS₂. However, initial reaction steps for the sulfidation of MoO₃ remain to be fully understood. Here, we report first-principles quantum molecular dynamics (QMD) simulations for the initiation dynamics of sulfidation of MoO₃ (010) surface using S₂ and S₈ molecules. We found that S₂ molecule is much more reactive on the MoO₃ surface than S₈ molecule. Furthermore, our QMD simulations revealed that a surface O-vacancy on the MoO₃ surface makes the sulfidation process preferable kinetically and thermodynamically. Our work clarifies an essential role of surface defects to initiate and accelerate the reaction of MoO₃ and gas-phase sulfur precursors for CVD synthesis of MoS₂ layers.

Highly Active 2D Layered MoS 2 -rGO Hybrids for Energy Conversion and Storage Applications

The development of efficient materials for the generation and storage of renewable energy is now an urgent task for future energy demand. In this report, molybdenum disulphide hollow sphere (MoS₂-HS) and its reduced graphene oxide hybrid (rGO/MoS₂-S) have been synthesized and explored for energy generation and storage applications. The surface morphology, crystallinity and elemental composition of the as-synthesized materials have been thoroughly analysed. Inspired by the fascinating morphology of the MoS₂-HS and rGO/MoS₂-S materials, the electrochemical performance towards hydrogen evolution and supercapacitor has been demonstrated. The rGO/MoS₂-S shows enhanced gravimetric capacitance values (318 ± 14 Fg⁻¹) with higher specific energy/power outputs (44.1 ± 2.1 Whkg⁻¹ and 159.16 ± 7.0 Wkg⁻¹) and better cyclic performances (82 ± 0.95% even after 5000 cycles). Further, a prototype of the supercapacitor in a coin cell configuration has been fabricated and demonstrated towards powering a LED. The unique balance of exposed edge site and electrical conductivity of rGO/MoS₂-S shows remarkably superior HER performances with lower onset over potential (0.16 ± 0.05 V), lower Tafel slope (75 ± 4 mVdec⁻¹), higher exchange current density (0.072 ± 0.023 mAcm⁻²) and higher TOF (1.47 ± 0.085 s⁻¹) values. The dual performance of the rGO/MoS₂-S substantiates the promising application for hydrogen generation and supercapacitor application of interest.

Hierarchical oxygen-implanted MoS2 nanoparticle decorated graphene for the non-enzymatic electrochemical sensing of hydrogen peroxide in alkaline media

Owing to the extensive applications of hydrogen peroxide (H₂O₂) in biological, environmental and chemical engineering, it is of great importance to investigate sensitive and selective sensing platform towards the detection of H₂O₂. Herein, oxygen-implanted MoS₂ nanoparticles decorated graphene nanocomposite is synthesized via a facile one-pot solvothermal method for the sensitive detection of H₂O₂ in alkaline media. The structure and morphology of the MoS₂/graphene nanocomposites were systematically characterized, showing that Mo-O bonds are formed and oxygen is implanted into the crystal structure in the nanocomposite. As a result, the MoS₂/graphene composite exhibited enhanced electron transfer kinetics and excellent electro-reduction performance towards H₂O₂ in alkaline media. Under optimum conditions, the fabricated sensor demonstrated a wide linear response towards H₂O₂ in the range of 0.25-16mM with a low detection limit of 0.12μM and high sensitivity of 269.7μAmM^-1cm^-2. Besides, the constructed sensor presented a good selectivity to H₂O₂ with the presence of other interfering species. Therefore, the proposed sensor was successfully applied for the detection and determination of H₂O₂ in real sample, indicating great potential for the practical applications.

Computational Synthesis of MoS2 Layers by Reactive Molecular Dynamics Simulations: Initial Sulfidation of MoO3 Surfaces

Transition metal dichalcogenides (TMDC) like MoS₂ are promising candidates for next-generation electric and optoelectronic devices. These TMDC monolayers are typically synthesized by chemical vapor deposition (CVD). However, despite significant amount of empirical work on this CVD growth of monolayered crystals, neither experiment nor theory has been able to decipher mechanisms of selection rules for different growth scenarios, or make predictions of optimized environmental parameters and growth factors. Here, we present an atomic-scale mechanistic analysis of the initial sulfidation process on MoO₃ surfaces using first-principles-informed ReaxFF reactive molecular dynamics (RMD) simulations. We identify a three-step reaction process associated with synthesis of the MoS₂ samples from MoO₃ and S₂ precursors: O₂ evolution and self-reduction of the MoO₃ surface; SO/SO₂ formation and S₂-assisted reduction; and sulfidation of the reduced surface and Mo-S bond formation. These atomic processes occurring during early stage MoS₂ synthesis, which are consistent with experimental observations and existing theoretical literature, provide valuable input for guided rational synthesis of MoS₂ and other TMDC crystals by the CVD process.

Liquid exfoliation of 2D MoS2 nanosheets and their utilization as a label-free electrochemical immunoassay for subclinical ketosis

We report the step-by-step fabrication of a 2D MoS₂ nanostructure-based disposable electrochemical immunosensor to detect β-hydroxybutyrate (βHBA), a novel subclinical ketosis biomarker. The MoS₂ nanosheets were exfoliated in the liquid phase by ultrasonication, and then followed by deposition on gold colloid modified screen-printed electrodes (Au-SPE). The MoS₂-modified electrodes were thoroughly characterized by physical, electrochemical as well as spectroscopic techniques, and the obtained results indicate the successful and irreversible electrodeposition of MoS₂ nanosheets. These MoS₂-modified disposable electrodes were subsequently bioconjugated with anti-βHBA antibodies and then employed for the label-free immunosensing of the βHBA biomarker to detect subclinical ketosis. A simple electrochemical Differential Pulse Voltammetry (DPV) technique based immunodetection was realized for the sensing of varying concentrations of βHBA antigen. The bioassay demonstrated remarkable sensitivity and specificity having a dynamic linear response range of 0.7 mM to 10 mM for βHBA in standard antigen solutions, spiked serum, blood, milk and clinical samples, with linear results being obtained with R² ∼ 0.9923. The sensor electrodes were also studied with other relative interferents to investigate cross reactivity and non-specificity. These electrodes showed a linear, specific, reproducible and stable response towards the βHBA antigen over a wide range of concentrations.

3D ordered porous MoxC (x = 1 or 2) for advanced hydrogen evolution and Li storage

3D ordered porous structures of Mo_xC are prepared with different Mo to C ratios and tested for two possible promising applications: hydrogen evolution reaction (HER) through water splitting and lithium ion batteries (LIBs). Mo₂C and MoC with 3D periodic ordered structures are prepared with a similar process but different precursors. The 3D ordered porous MoC exhibits excellent cycling stability and rate performance as an anode material for LIBs. A discharge capacity of 450.9 mA h g^-1 is maintained up to 3000 cycles at 10.0 A g^-1. The Mo₂C with a similar ordered porous structure shows impressive electrocatalytic activity for the HER in neutral, alkaline and acidic pH solutions. In particular, Mo₂C shows an onset potential of only 33 mV versus a reversible hydrogen electrode (RHE) and a Tafel slope of 42.5 mV dec^-1 in a neutral aqueous solution (1.0 M phosphate buffer solution), which is approaching that of the commercial Pt/C catalyst.

Electronic and optical properties of nanostructured MoS2 materials: influence of reduced spatial dimensions and edge effects

Theoretical prediction of how the electronic and optical properties of nanostructured MoS₂ materials are influenced by reducing spatial dimensions and edge effects is presented. We open pathways for further experimental studies and potential optoelectronic applications.

Modified chemical synthesis of MnS nanoclusters on nickel foam for high performance all-solid-state asymmetric supercapacitors

Novel MnS nanoclusters were synthesized on nickel foam (NF) using a successive ionic layer adsorption and reaction (SILAR) method.