Theoretical Study On The Structure-activity Relationship Of MoS₂ And TiO₂ Nanocomposites

In recent years,nanocomposites include Molybdenum Disulfide(MoS2)and Titanium Dioxide(TiO2)could produce a clean energy and degradate the pollutants through the absorption and utilization of solar energy.These semiconductor materials could create a green and environmentally way of using solar energy in the future social for the human.In this paper,the density functional theory(DFT)is used as the main research method.The photocatalytic performance of MoS2-CdS heterojunction and TiO2-CdS heterojunction are systematically studied.And the mechanism of MoS2(100)-Pt material as the catalyst which replaced Platinum(Pt)in Photoelectric conversion is studied.The main conclusions of this paper as follow:(1)The photocatalytic activity of MoS2-CdS heterojunction was calculated by density functional theory and hybrid density functional(HSE06).MoS2 acts as a photosensitizer in MoS2-CdS heterojunction,and it makes the electron-hole pair occurs easily.At the same time,the electron-hole pair could be effectively separated.The electrons can be injected from MoS2 into CdS easily in visible light.Our results show that the energy gap of MoS2-CdS is 2.11 eV,and the electrons of heterojunction can transfer from valence band maximum(VBM)to conduction band minimum(CBM)under light irradiation.In addition,the light absorption edge of the MoS2-CdS heterojunction shows a longer wavelength region than the monolayer CdS.We reckon that MoS2-CdS heterojunction exhibits great photocatalytic activity in visible light.(2)We used the density functional theory(DFT)and HSE06 hybrid density functional method to calculate and study the electronic structure of TiO2-CdS heterojunction materials.The electronic structure include the energy band,density of states(DOS),effective mass and light absorption.Our results show that the electronic structure of TiO2-CdS heterojunction material shows good metal property.In addition,the light absorption edge of of TiO2-CdS heterojunction materials are far more than that of TiO2.We propose that this TiO2-CdS heterojunction material is a new type of TiO2-based photoelectric conversion material.Our simulation study also provides a part of theoretical research on the future application of heterojunctions in the photoelectric conversion material.(3)Hydrogen evolution reaction(HER)is a basic process in electrocatalysis.At the same time,hydrogen evolution reaction plays an important role in the energy conversion of hydrogen production by water decomposition.In order to find a excellent catalyst which could replace the metal platinum,we chose MoS2 material,cleaved the(10 0)orientation and made 4×4 supercell.We doped a metal platinum atom on the MoS2(100),and we called it MoS2(100)-Pt.We used the density functional theory(DFT)to calculate and study the electronic property for MoS2(100)-Pt.Based on the calculation and study of the surface energy and the adsorption energy of MoS2(100)-Pt material,it is found that the Volmer-Heyrovsky reaction path in MoS2(1 0 0)-Pt material is considered the main mechanism of this model.We obtained that the Volmer is the rate-determining step(rds).At the same time,the S-hollow structure is considered as a more suitable structure because the over-potential of S-hollow structure is the lowest of all structures in the hydrogen evolution reaction.