Dynamics of oxygen species on reduced TiO₂(110) rutile

Using density functional theory calculations, we have investigated the adsorption and diffusion of oxygen species on the reduced TiO₂(110) surface. We have found that molecular O₂ strongly binds not only to O vacancies, but also to Ti(5c) neighbors, due to delocalization of unpaired electrons arising from removal of neutral bridging oxygen. Our results show that molecular O₂ can jump across an oxygen vacancy and diffuse along a Ti(5c) row with moderate barriers. On the other hand, atomic O diffusion along a Ti(5c) row is rather unlikely at low temperatures (<300 K), because of the relatively higher probability of O-O formation from interaction with an adjacent bridging O(2c) atom. Based on our calculation results, we discuss the diffusion and healing of O vacancies associated with O₂ adsorption.