Defect-engineered two-dimensional transition metal dichalcogenides towards electrocatalytic hydrogen evolution reaction

Recently,two-dimensional transition metal dichalcogenides(TMDs)demonstrated their great potential as cost-effective catalysts in hydrogen evolution reaction.Herein,we systematically summarize the existing defect engineering strategies,including intrinsic defects(atomic vacancy and active edges)and extrinsic defects(metal doping,nonmetal doping,and hybrid doping),which have been utilized to obtain advanced TMD-based electrocatalysts.Based on theoretical simulations and experimental results,the electronic structure,intermediate adsorption/desorption energies and possible catalytic mechanisms are thoroughly discussed.Particular emphasis is given to the intrinsic relationship between various types of defects and electrocatalytic properties.Furthermore,current opportunities and challenges for mechanical investigations and applications of defective TMD-based catalysts are presented.The aim herein is to reveal the respective properties of various defective TMD catalysts and provide valuable insights for fabricating high-efficiency TMD-based electrocatalysts.