Role of Defects in Photocatalytic Water Splitting: Monodoped vs Codoped SrTiO${}_3$

Using the hybrid density functional theory and $\mathit{\text{ab}}\mathit{\text{initio}}$ atomistic thermodynamics, we report monodoping of non-metal (N) or metal (Mn) in SrTiO${}_3$ can induce visible light absorption, but none of them are suitable to ameliorate the photocatalytic activity. Therefore, in order to achieve enhanced photocatalytic activity of SrTiO${}_3$, we have employed codoped Mn and N simultaneously in SrTiO${}_3$ to modulate its electronic properties effectively. In the codoped SrTiO${}_3$, the recombination of photogenerated charge carriers is suppressed, and the diffusion and mobility are increased owing to the passivation of discrete localized states. Our results reveal that Mn${}_{\text{Sr}}{\text{N}}_{\text{O}}$ (codoping of Mn at Sr site and N at O site) is the most promising candidate for enhancing the photocatalytic activity of SrTiO${}_3$ under visible light.