How does the B,F-monodoping and B/F-codoping affect the photocatalytic water-splitting performance of g-C3N4?

Abstract

By means of density functional theory (DFT) computations, we investigated the electronic and optical properties of B,F-monodoped and B/F-codoped graphitic carbon nitride (g-C₃N₄) to explore the doping effects on the photocatalytic performance of g-C₃N₄. It is found that F atom addition plays a key role in stabilizing the surface of g-C₃N₄ and facilitating B atom substitution into g-C₃N₄. Among the different doping strategies, only B/F-codoping does not have localized states in the midgap, which act as recombination centers for the photogenerated electron–hole pairs. All the doping strategies in this study can improve the utilization ratio of visible light for the g-C₃N₄ photocatalyst. Considering the relationship of overpotential of water redox reaction over g-C₃N₄ and band edge positions with respect to the water redox potentials, only the F-doped and B/F-codoped g-C₃N₄ satisfy the criterion for overall water splitting. In other words, the B/F-codoping strategy not only meets the demands of no recombination centers and enhances the visible light utilization ratio, but also satisfies the need of overpotential. Thus, B/F-codoped g-C₃N₄ is expected to be a promising photocatalyst for overall water splitting under visible light.