Theoretical Study On The Regulation Of Electrochemical Hydrogen Evolution Performance Of Transition Metal Dichalcogenides

Due to the increasing prominence of energy problems,how to electrocatalytic decomposition of aquatic hydrogen with lower cost and high efficiency has become a hot research in the world today.Despite decades of efforts,no catalyst has yet been able to meet the needs of commercial applications.Two-dimensional transition metal dichalcogenides have been widely concerned because of their advantages such as low price,large comparative area,strong electrical conductivity,diverse electronic structure and easy modulation.At the same time,with the continuous improvement of computer performance,the rapid development of numerical algorithms and related theories,the theoretical calculation based on first principles is widely used in material prediction.In this thesis,first-principles calculation has been adopted to study and design electrocatalyst for electrochemical hydrogen evolution based on transition metal sulfides.The main research contents include the following aspects:1.Charge-modulated VS2 Monolayer for Effective Hydrogen Evolution Reaction.In this work,we engineer the surface structure of VS2 by doping 3d transition metal(TM=Ti-Ni)atoms aiming to improve its catalytic activity.Our results indicate that the HER performances of these TM@VS2s are much better than pristine VS2 due to the charges modulation in S sites.Particularly,three systems of TM@VS2s(TM=Ti,Mn,Co)are found to be perfect catalysts for HER with ideal ΔGH～0 eV,even superior to that of Pt.Moreover,the HER performances of TM@VS2s are revealed to depend strongly on the choice of TM elements as well as their doping concentrations.Our study provides a promising way to design an effective electrocatalysts for the conversion and storage of energy in the future.2.High Electrocatalytic Activity of Defected MX2/Graphene Heterostructures(M=Mo,W;X=S,Se)for Hydrogen Evolution Reaction.T wo-dimensional transition metal dichalcogenides have been regarded as cheap and abundant catalysts for driving electrolysis of water.Using density functional theory methods,we systematically investigate the hydrogen evolution reduction of metal dichalcogenides/graphene heterostructures(MX2/Gs,M=Mo,W;X=S,Se)with various defects,MX2/G_Vx,MX2/G_VM MX2/G_V(M+X).We find that such defect MX2/Gs show better hydrogen evolution reactive activities than pure MX2/Gs as well as freestanding MX2 monolayers,due to the metallic states induced by the defects.Particularly,the MX2/G_VXs with S(Se)vacancy display catalytic performance is comparable to that of Pt.Moreover,the catalytic performance of most defected MX2/G_VMs and MX2/G_V(M+X)s varies with H coverage and M vacancy concentration.Our results provide a feasible way applying to water electrolysis for hydrogen production.3.Designed Borophene/MS2 Hybrid Catalysts for Enhanced Hydrogen Evolution Reaction.Using density functional theory,we systematically calculated the structural stability and electrocatalytic HER properties of the heterostructures formed by α,β and β12 borene with VS2(MoS2).The results show that the heterojunction has strong structural stability and its metallic property is enhanced.Heterojunction can effectively improve the HER performance of monolayer VS2 or MoS2,while maintaining the excellent HER performance of monolayer boronene.Especially in Br/VS2s,HER activity on borene layer and VS2 layer is similar,indicating that they can be used as bilateral efficient HER catalysts.Through the interaction within the layers and the synergistic effect of the strain regulation of each layer,the heterostructures can improve the HER properties of VS2 or MoS2,while maintaining the excellent HER properties of the monolayer borene.