Preparation And Hydrogen Evolution Property Research Of VS₂@MoS₂

In this paper,based on a thorough understanding of the properties and synthetic methods of transition metal sulfide nanocomposites,the characteristics,common preparation methods and electrocatalytic hydrogen evolution properties of molybdenum disulfide and vanadium disulfide were studied in detail.Pure molybdenum disulfide and vanadium disulfide with ideal morphology were prepared and selected using a simple one-step hydrothermal method.On the basis of the synthesis of vanadium disulfide nanoflowers,a two-step hydrothermal method was adopted with adjusting the amount of molybdenum disulfide reactants to grow the molybdenum disulfide nanosheet on the nanometer surface of vanadium disulfide.The constituent,morphology and electronic structure of the VS₂@MoS₂ composite,were characterised by XRD,XPS and other methods.In terms of performance testing experiments,we conducted performance tests and comparisons on electrochemical hydrogen evolution of MoS₂ nanosheets,VS₂ nanoflowers,and VS₂@MoS₂composites.The experimental results show that the composites own the better properties as cathode catalysts of electric hydrogen evolution.Both the overpotential and Tafel slope were smaller than the two pure materials,and the performance decayed little after 1000 cycles.After that,we conducted a comprehensive analysis and interpretation of the differences arising from the morphology,conductivity,electronic structure and theoretical calculations.The composite material has better catalytic activity and stability as a cathode catalyst for hydrogen production from electrolysis of water.We can foresee that the VS₂@MoS₂ heterostructure will be an excellent alternative of precious metal Pt in the field of clean energy.The innovation of this article mainly has several aspects:1.The VS₂@MoS₂ composite material was successfully synthesized for the first time using a simple two-step hydrothermal method.No catalyst or surfactant was added during the process.At the same time,the use of toxic gases is avoided during the synthesis of VS₂,ensuring the safety of the experiment.2.Comprehensive characterization and analysis of synthetic samples.The components and the valence states of elements were characterized by XRD and XPS.The morphology and crystal growth direction were characterized by SEM and TEM.The electronic structures were characterized by Raman,UPS and XAFS.3.The synthesized sample was used as a cathode catalyst to test its electrochemical hydrogen evolution performance by a three-electrode system.Compare to various hydrogen evolution reaction parameters such as overpotential and Tafel slope of VS₂@MoS₂ composites with pure materials and summarized the results of the experiment.4.Based on the experimental results,the reasons for the increase in hydrogen evolution performance of the composites were analyzed.Firstly,the composite process inhibits the occurrence of curl clustering of the molybdenum disulfide nanosheets so that more hydrogen evolution active sites can be exposed;secondly,metallic VS₂ as the conductive substrate makes the composite material better conductivity and the substrate itself also has hydrogen evolution activity.In addition,the outer layer of molybdenum disulfide has a good stability,to ensure the stability of the overall hydrogen evolution properties of composite materials.5.The energy band structure and Gibbs free energy of the material were calculated by simulating two different layer stacking models.The reasons for the improvement of the hydrogen evolution performance were explained theoretically.