Study On Electronic Structure Of Doped Monolayer MoS₂ Based On Density Functional Theory And Photocatalytic Hydrogen Production By Hydrolysis

As the backbone of energy,fossil energy is not only a non-renewable resource,but also causing a series of environmental problems,such as thermal pollution,greenhouse effect,acid rain and so on.At this time,the development of new energy is particularly important.Solar energy as one of the most easily accessible,clean and pollution-free new energy,has been paid more and more attention.There are many ways to use solar energy,which include heat utilization,light utilization and photochemical utilization.One of the most environmentally and potentially way is making hydrogen from H2 O by using solar energy.This thesis studied the electronic structure of doped monolayer MoS2 and its ability of hydrogen production by hydrolysis,which based on the first-principles of density functional theory.It provided the mechanism data for photocatalytic hydrogen production by hydrolysis.The contents of the study consist of two parts.In the first part,the structure parameters,band structure,redox potential,density of states,optical absorption properties and photocatalytic potential of intrinsic and O,Se,Te doped monolayer MoS2 were calculated.The results show that the cell parameters and bond length of intrinsic and doped monolayer MoS2 increase with the increase of atomic radius,the bond angle decreases with the increase of atomic radius,the band gap width decreases successively before and after doping,the conductivity increases,the red shift of doped monolayer MoS2 occurs,and the absorption efficiency of visible light increases.The conduction bottom potential of O,Se,Te doped monolayer MoS2 is negative to the reduction potential of hydrolysis hydrogen production reaction,and its valence top potential is positive to the oxidation potential of hydrolysis hydrogen production reaction,so it has potential as a photocatalyst.Among them,Se doping balanced the electron hole demand of valence band and conduction band,balanced the reduction and oxidation ability of hydrogen production by hydrolysis,and further improved the performance of monolayer MoS2 as photocatalyst.In the second part,on the basis of the first part,the MoS2(1-x)Se2x with different x values(x = 0.125,0.25,0.375,0.5)was calculated,and the adsorption of water molecules at four adsorption sites,H,B,TM and TS,was studied.The results show that water molecules can form adsorption on the surface of single MoS2,and the best adsorption structure is the B site adsorption at x = 0.25,which has better adsorption energy and balance distance.In addition,TM adsorption configuration also has better adsorption energy and equilibrium distance.These study help to discover suitable single-layer MoS2 doping elements and obtaining suitable adsorption of water molecules.It provides theoretical support for further study of doped single-layer MoS2 to improve its hydrogen production performance by hydrolysis.