The Investigation On Adsorption And Photocatalytic Properties Of ZnO Monolayer

ZnO monolayer(ZnO-ML)has good application potential in the fields of gas sensors and photocatalysis because of its excellent electrical properties and large specific surface area,so it has aroused great interests from researchers.In this work,the study about the adsorption between HF gas and Al-doped ZnO-ML and Cd-Ag co-doped ZnO-ML is carried out by first principle calculation,the researches are as follows:1.Based on the GGA method,the first principle method is used to study the adsorption of HF molecule on both intrinsic ZnO-ML and Al-doped ZnO-ML(Al-ZnO-ML).The calculation results show that when HF is adsorbed on the surface of intrinsic ZnO-ML,HF tends to be vertically or obliquely adsorbed at T_O site(the top of oxygen atom)on the surface of ZnO-ML.The adsorption configuration between HF and ZnO-ML is molecular adsorption,and there is weak interaction between HF and intrinsic ZnO-ML.However,when HF is adsorbed on Al-ZnO-ML,HF tends to be obliquely adsorbed at the T_O site on the surface of Al-ZnO-ML,the H-F bond is broken,the adsorption configuration between HF and Al-ZnO-ML is dissociative adsorption,and the interaction between Al-ZnO-ML and HF is enhanced.The analysis of Mulliken population and electronic density differences shows that the adsorption of HF molecule on intrinsic ZnO-ML is by weak physisorption,while the adsorption of HF molecule on Al-ZnO-ML is by chemisorption.Therefore,Al-ZnO-ML could be one of the good sensor materials to detect HF gas.2.Based on the GGA+U correction,the first principle calculation about the electrical and optical properties of Cd-Ag co-doping ZnO-ML system with different Ag and Cd doping concentrations is performed.And the properties of Cd or Ag single-doping ZnO-ML are calculated for comparison.The research shows that with the increase of Cd or Ag concentration,the lattice parameters of Cd-Ag co-doping system increase,the formation energy increases,but the structural stability decreases.For Cd-Ag co-doping systems,with the increase of Ag doping concentration,the forbidden band width decreases firstly and then increases,more impurity levels are introduced into the forbidden band,the peak of the imaginary part of the dielectric function is red-shifted and the light absorption coefficient increases compared with the Cd single-doping ZnO-ML.Besides,for the co-doping systems,with the increase of Cd doping concentration,the forbidden bandgap decreases,the peak of the imaginary part of the dielectric function increases,and compared with Ag single-doping ZnO-ML,the absorption edge is red-shifted,and the light absorption coefficient is enhanced in the 0～1.5 e V region,it shows that the photocatalytic property of ZnO-ML is improved.The research could provide some theoretical references for the study of ZnO-ML in gas sensors and photocatalysis.