Theoretical study on cation codoped SrTiO₃ photocatalysts for water splitting

The large band gap of SrTiO₃ is disadvantageous for photocatalytic applications. We therefore study cation codoping to modify the size of the band gap and extend the absorption to visible light. We identify efficient codoping schemes that guarantee charge compensation to avoid creation of localized states. Using the Heyd-Scuseria-Ernzerhof hybrid functional, we analyze the crystal and electronic structures as well as the optical properties. It is found that (Nb/Ta, Ga/In) codoping does not reduce the band gap, in contrast to (Mo/W, Zn/Cd) codoping. The position of the conduction band edge after (Mo, Cd) codoping impedes a high photocatalytic efficiency, whereas (Mo/W, Zn) and (W, Cd) codoping are found to be favorable.