Interaction of O2 with reduced rutile TiO2(110) surface

The interaction of O2 with a reduced rutile TiO2(110) surface is investigated using density functional theory calculations. We report new insights on the distribution of bridge-bonded oxygen vacancies (BBOVs), the adsorption geometry, formation energy, reaction barrier, and diffusion pathway of O2 on the surface. Our calculations confirm that the BBOVs tend to form single point defects because of repulsion between neighboring BBOVs. Converged DFT results indicate that an O2 landing on a reduced r-TiO2(110) surface will adsorb molecularly at low temperatures in good agreement with experimental observations below 100 K. At room temperature, oxygen adsorbs dissociatively, after climbing over an energy barrier. The calculations further show that oxygen in dissociative configuration forms an OO complex on the surface, sitting between in-plane oxygen and Ti atoms. These are intrinsic properties of reduced r-TiO2(110) and we have neglected the effect of bulk Ti-interstitials. Finally, the calculations show that two O2 molecules reacting with a bridge-bonded oxygen vacancy can form an ozone molecule at low temperatures.