First-principles study of the co-effect of carbon doping and oxygen vacancies in ZnO photocatalyst

Although tuning band structure of optoelectronic semiconductor-based materials by means of doping single defect is an important approach for potential photocatalysis application, C-doping or oxygen vacancy (Vo) as a single defect in ZnO still has limitations for photocatalytic activity. Meanwhile, the influence of co-existence of various defects in ZnO still lacks sufficient studies. Therefore, we investigate the photocatalytic properties of ZnO_xC_0.0625 (x = 0.9375, 0.875, 0.8125), confirming that the co-effect of various defects has a greater enhancement for photocatalytic activity driven by visible-light than the single defect in ZnO. To clarify the underlying mechanism of co-existence of various defects in ZnO, we perform systematically the electronic properties calculations using density functional theory. It is found that the co-effect of C-doping and Vo in ZnO can achieve a more controllable band gap than doping solely in ZnO. Moreover, the impact of the effective masses of ZnO_xC_0.0625 (x = 0.9375, 0.875, 0.8125) is also taken into account. In comparison with heavy Vo concentrations, the light Vo concentration (x=0.875) as the optimal component together with C-doping in ZnO, can significantly improve the visible-light absorption and benefit photocatalytic activity.