Understanding photocatalytic water oxidation in SrTiO₃ [001] surfaces

Perovskite oxides such as SrTiO₃ have garnered considerable interest due to their high photocatalytic efficiency under UV irradiation as well as favorable interfacial interactions with water, two important features that drive solar water splitting. In this work, we present a unified computational and experimental account of the photocatalytic activity at the SrO- and TiO₂- terminations of aqueous-solvated [001] SrTiO₃. Our experimental investigations show that the overall water splitting proceeds only when both SrO- and TiO₂- terminations are exposed to water. Using density functional theory-based simulations, we verify this observation and elucidate the underlying mechanism driving this process using a sequence of four hole transfers. We conclude that while the water-oxidation reaction is favorably catalyzed only at the SrO-surface, the TiO₂-surface provides the necessary band alignment for the redox reaction to proceed, thus proving that both terminations are crucial for photocatalytic water splitting.