Synthesis Of Te-doped WS₂ Nanosheets Catalyst And Study Of Hydrogen Evolution Reaction In Electrocatalysis

Hydrogen has been considered as the ideal substitute for traditional fossil fuel because of the high energy density and environmental friendliness.At present,it is generally accepted that the important method for preparing hydrogen is to electrolyze water.The catalytic performance of noble metal catalysts is optimal,but its high price and low reserves limit its wide application in industrial production.Therefore,exploring non-noble metal catalysts with high catalytic activity is an inevitable trend for the development of electrolytic water for hydrogen production.In recent years,the layered transition metal dichalcogenides(TMDs)with graphene-like structure as hydrogen evolution reaction(HER)catalysts have attracted numerous attentions,especially WS₂.However,the HER active sites of WS₂ are mainly distributed on the boundary of material,its basel plane is almost inert and the semiconductor properties are not conducive to electron transfer,which limit the application of WS₂ as a HER catalyst in the industrial field.Considering Te can tune the bandgap with a wide range and the electronegativity between S atom and Te atom is significantly different,so we prepared Te-doped WS₂ nanosheets and studied the mechanism of the electronic structure of the material on its electrochemical performance.The main research contents are as follows:The Te-doped WS₂ nanosheets were fabricated on the surface of W foil via a two-step chemical vapor deposition(CVD)-assisted strategy.The influences of raw material ratio,temperature,time and atmosphere on the morphology and structure of Te-doped WS₂ nanosheets were studied.The effect of Te doping on the HER properties of WS₂nanosheets was investigated as well.The results show that the Te-doped WS₂nanosheets growing vertically on the surface of W foil have a large specific surface area,which is benificial to the H atoms adsorption.At the same time,the doped Te atoms activate the WS₂ basel plane and improves the HER activity.In 0.5 M H₂SO₄ solution,the overpotential of Te-doped WS₂ nanosheets with superior stability is 213 m V for 10m A/cm² and the Tafel slope of 94 m V/dec.Futhermore,the Gibbs free energy of hydrogen adsorption(?G_H),bandstructure,electron density of state and charge density difference of the low-index surface of Te-doped WS₂ were simulated by first principles calculation.It was shown that the?G_H of the basal plane around Te atom and hollow site of Te-doped WS₂ nanosheets are 2.08e V and 1.85 e V,respectively.Te atoms with relatively lower electronegativity than S increase the electron density of the adjacent region,so the S sites on the basal plane of WS₂ nanosheets were activated and the HER activity is increased.Meanwhile,the bandgap of WS₂ nanosheets was reduced from 1.92 e V to 1.47 e V after Te doping,which enhancing the charge transfer to improve the electrochemical catalytic reaction.In addition,when the relative content of Te is 0.79,the Te-doped WS₂ is in a critical phase(2H?1T').At this time,the material has a higher hydrogen adsorption energy and facilitates the adsorption of hydrogen in the reaction,which providing a strong theoretical reference for the rational design of HER catalysts.