Hybrid density functional study of band gap engineering of SrTi O 3 photocatalyst via doping for water splitting

Perovskite $\mathrm{SrTi}{\mathrm{O}}_{3}$ (STO) is an attractive photocatalyst for solar water splitting but suffers from a limited photoresponse in the visible spectral range due to its wide band gap. By means of hybrid density functional theory calculations, we systematically study engineering its band gap via doping $4d$ and $5d$ transition-metals $M$ ($M=\mathrm{Zr}$, Nb, Mo, Tc, Ru, Rh, Pd, Hf, Ta, W, Re, Os, Ir, and Pt) and chalcogen elements $Y$ ($Y=\mathrm{S}$ and Se). We find that transition-metal dopant $M$ either has no effect on the STO band gap or introduces detrimental midgap states except for Pd and Pt that are able to reduce the STO band gap. In contrast, doping S and Se significantly reduces STO's direct band gap, thus, leading to appreciable optical absorption transitions in the visible spectral range. Our findings provide that Pd-, S-, and Se-doped STO are potential promising photocatalysts for water splitting under visible light irradiation thereby providing insightful theoretical guides for experiments to improve the photocatalytic activity of STO.