The effect of Ag doping and point defects on the electronic structure and photocatalytic properties of ZnO using first-principles

Abstract

At present, the photocatalytic properties of Ag-doped ZnO have been extensively studied, but the mechanism of Ag-doped ZnO photocatalysis is not fully understood. The effect of intrinsic point defects on the performance and mechanism of Ag-doped ZnO photocatalysis has rarely been studied by theoretical calculations. To solve such problems, first-principle calculations were performed to systematically investigate the effect of Ag doping (Ag_Zn/Ag_i) and point vacancy (V_Zn/V_O) on the photocatalytic performance and mechanism of ZnO. It was found that the ZnO:Ag_i+V_Zn showed the strongest structural stability compared to the three doping methods, ZnO:Ag_Zn+V_Zn, ZnO:Ag_Zn+V_O, and ZnO:Ag_i+V_O. In addition, the doping of interstitial Ag with Zn vacancy shrank the ZnO bandgap to the smallest bandgap width (2.46 eV), thereby broadening the ZnO absorption spectrum into the visible range. The study of the dipole moment, static dielectric constant, and carrier effective mass showed that the ZnO:Ag_i+V_Zn exhibited excellent photocatalytic polarization and activity in the visible range. In particular, along the [001] direction, electrons and holes showed stronger mobility, resulting in effective separation and transfer of electron-hole pairs and a reduction in the electron-hole complex rate. The results provided a theoretical reference for in-depth understanding and designing of novel ZnO photocatalysts.