Photocatalytic water oxidation on SrTiO${}_3$ [001] surfaces

Abstract

SrTiO${}_3$ is a highly efficient photocatalyst for the overall water splitting reaction under UV irradiation. However, an atomic-level understanding of the active surface sites responsible for the oxidation and reduction reactions is still lacking. Here we present a unified experimental and computational account of the photocatalytic activity at the SrO- and TiO${}_2$- terminations of aqueous-solvated [001] SrTiO${}_3$. Our experimental findings show that the overall water-splitting reaction proceeds on the SrTiO${}_3$ surface only when the two terminations are simultaneously exposed to water. Our simulations explain this, showing that the photogenerated hole-driven oxidation primarily occurs at SrO surfaces in a sequence of four single hole transfer reactions, while the TiO${}_2$ termination effects the crucial band alignment of the photocatalyst relative to the water oxidation potential. The present work elucidates the interdependence of the two chemical terminations of SrTiO${}_3$ surfaces, and has consequent implications for maximizing sustainable solar-driven water splitting.

11 + 6 pages, 6 + 8 figures, including Supplementary Information