The Regulation Of Composition And Structure Over Tungsten Sulfide Electrocatalysts And Their Performances In Hydrogen Evolution Reaction

With the development of human society,the consumption of traditional fossil fuels is rapidly increasing,and their limited reserves are bound to constrain significant use in the long term.In addition,the consumption of fossil fuel produces a large number of harmful substances,leading to serious problems of environmental pollution and deterioration of the ecological environment around the earth.Therefore,the development and application of sustainable clean energy become important and urgent.As a green and pollution-free clean energy,hydrogen has a broad prospect in the application with the advantages of abundant reserves,high combustion value,and is not constrained by region and natural environment.At present,hydrogen evolution reaction（HER）is the most environmentally friendly and potential method for hydrogen production.In order to improve the energy conversion efficiency of HER,catalysts with high catalytic activity are essential.Recently,due to Pt-like electronic structures,tungsten sulfide（WS₂）has attracted the attention of many scientists.In this thesis,a series of tungsten sulfide-based catalysts with enhanced HER activity are synthetized via different methods and a variety of characterization methods are used to analyze the phase composition,structure morphology and electrochemical performance.Results of the research are listed as follows:（1）Tungsten sulfide electrocatalysts with sulfur-rich vacancy defect were prepared by stripping sulfur atoms from WS₂ with hydrogen at high temperature.The results show that the proper reduction temperature and holding time are favorable for the formation of sulfur vacancies,which provide more active sites and improve the hydrogen evolution performance of tungsten sulfide significantly.The optimal sample has good hydrogen evolution performance and stability with a Tafel slope of 85 m V dec^-1 in acid solution.（2）Using tungsten trioxide and thiourea as raw materials,Ketjenblack carbon as support and silica nanospheres as template,carbon-supported tungsten sulfide was synthesized by the high temperature calcination.The results show that Ketjenblack carbon can effectively improve the overall conductivity of the catalyst and accelerate the charge transfer rate during the reaction process.Moreover,the template can help WS₂ to increase the specific surface area,distribute carbon black evenly,increase the number of active sites for hydrogen evolution,and improve the activity of the catalyst.（3）Using WS₂ spheres,Na₂Mo O₄·2H₂O and C₅H₁₀NNa S₂·3H₂O as raw materials,the Mo S₂/WS₂ heterostructures were synthesized by a facile hydrothermal method.The results show that spherical WS₂ can increase the specific surface area of the material,and Mo S₂ with fine edges can provide more active sites for HER.Actually,a reasonable W/Mo ratio can improve the microstructure of the sample,which is conducive to the optimal hydrogen evolution performance of the catalyst.