The Potential of Overlayers on Tin-based Perovskites for Water Splitting
Photoelectrochemical water splitting is a promising method of clean hydrogen production for green energy uses, but requires the surface of a semiconducting material in water to meet certain energetic and electronic criteria. In this paper, we report on a first-principles study of tin-based perovskites, based upon density functional theory, where we investigate how the formation of a surface affects the electronic properties of these materials. Of the materials considered, we show that the best candidate for water-splitting, SrSnO3, possesses hydrogen and oxygen overpotentials of 0.75 and 0.72 eV, respectively, which are reduced to 0.35 and 0.54 eV with the inclusion of a ZrO2 overlayer. Furthermore, this overlayer promotes charge extraction, stabilizes the reaction pathways, and improves the band gap such that it straddles the overpotentials between pH 0 and pH 12. This result indicates that SrSnO3 with a ZrO2 overlayer has significant potential as a highly efficient bifunctional water splitter for producing hydrogen and oxygen gas on the same surface.