Study of interface charge transfer and visible light response of graphene/BiVO 4 heterojunctions with different concentrations of oxygen vacancies using the GGA + U method

Constructing oxygen vacancy defects is a promising strategy to augment the photocatalytic performance of materials. In this study, we utilized the Generalized Gradient Approximation (GGA) with the Hubbard-U correction method (GGA + U) to investigate the interface charge transfer and visible light response of graphene/BiVO4 heterojunctions with oxygen vacancy concentrations of 0%, 2.08%, 4.17%, and 6.25% in order to understand their photocatalytic mechanism. The DFT analysis demonstrated that the introduction of oxygen vacancies can transform the bandgap type of graphene/BVO from indirect to direct. When the oxygen vacancy concentration reaches 2.08%, the bandgap width of the graphene/BVO-1 structure is significantly reduced, and the range of visible light response is notably expanded, providing the optimal light response range. This work not only further confirms that oxygen vacancies can significantly enhance the photocatalytic properties of graphene/BiVO4 heterojunctions but also investigates the influence of different concentrations of oxygen vacancies on their photocatalytic properties. This provides further mechanistic insights into the synergistic effect of defect engineering and heterojunctions.