A combination of high-resolution scanning tunnelling microscopy and density functional theory was used to study the interaction of water with the reduced TiO2(110)-(1x1) surface. As the direct product of water dissociation into oxygen vacancies, paired hydroxyl groups were formed. These pairs were immobile and stable unless they interacted with adsorbed water molecules. As a result of these interactions, protons were transferred to adjacent oxygen rows, thereby forming single hydroxyl groups. Additionally, it was shown that hydroxyl groups facilitated the diffusion of water molecules over the oxygen rows.

Formation and Splitting of Paired Hydroxyl Groups on Reduced TiO2(110). Wendt, S., Matthiesen, J., Schaub, R., Vestergaard, E.K., Lægsgaard, E., Besenbacher, F., Hammer, B.: Physical Review Letters, 2006, 96[6], Physical Review Letters, 2006, 96[6], 066107