Water Splitting on Ti-Oxide-Terminated SrTiO3(001)

Abstract

Combining X-ray photoelectron spectroscopy with the standing wave technique, we investigated adsorption of a monolayer of water on Ti-oxide-terminated SrTiO3(001) in ultra-high vacuum (UHV). At room temperature, the surface is water-free but hydroxylated. A quarter monolayer of hydroxyl is tightly bound 1.85 ± 0.06 Å above the TiO2 surface. Deposited at a low temperature, a monolayer of water adsorbs with the oxygen located 2.55 ± 0.2 Å above the surface, apparently close to atop Ti, but H2O is unstable at 200 K. A fraction desorbs, in part under the X-ray beam, but a major fraction of H2O dissociates immediately, with the liberated hydrogen most likely attaching to a surface oxygen. The produced hydroxyls bind only loosely to the surface, are unstable at 200 K, and rapidly desorb once the surface is water-free. Although our study was conducted in UHV, the presented results suggest that Ti-oxide-terminated SrTiO3(001) may possess a high catalytic activity toward hydrolysis under realistic conditions.