Density functional theory was employed to investigate the formation and properties of the O vacancies on the rutile TiO2(110) surface. It was found that the formation of the positively charged bridging-O vacancy (BOV+, 4.2eV) was the most favored one, followed by the positively charged in-plane-O vacancy (POV+, 4.5eV). In contrast, the formation of the neutral bridging-O and in-plane-O vacancies, and their O vacancies (BOV2+ and POV2+) required much higher energies (7.9 and 8.3 vs. 8.1 and 8.6eV), respectively.

Formation of Oxygen Vacancies on TiO2(110) Surfaces. S.G.Wang, X.D.Wen, D.B.Cao, Y.W.Li, J.Wang, H.Jiao: Surface Science, 2005, 577[1], 69-76