The Roles of Reduced Ti Cations and Oxygen Vacancies in Water Adsorption and Dissociation on SrTiO3(110)

The interaction of water with SrTiO3(110) surfaces has been investigated by using low-energy electron diffraction and X-ray photoelectron spectroscopy in ultrahigh vacuum. Three different types of surfaces are compared: (n X 1)-reconstructed surfaces consisting of Ti4+ sites, the sputtered surface with a high concentration of oxygen vacancies (V-O), and the (1 x 10) surface containing ordered Ti3+-rich structures on SrTiO3(110). Water molecules can be adsorbed on all the surfaces below similar to 200 K. At high temperatures, remarkable dissociation of water was observed on the sputtered surfaces, whereas a relatively strong molecular adsorption was detected on the (1 X 10) surface. Both kinds of the high-temperature adsorption are accompanied by the decrease of surface Ti3+ concentration and more stable than that on the (n X 1) surface. Our results indicate that the high concentration of Ti3+ sites is involved in the interaction with water molecules, and Ti3+-V-O complexes facilitate the dissociation of water.