Photoinduced Dissociation of O2 on Rutile TiO2(110)

The adsorption and photon-stimulated reactions of O2 adsorbed on reduced, rutile TiO2(110) are investigated. After adsorption at 28 K and annealing to 100 K, at least 85% of the adsorbed oxygen has not dissociated. Typically less than 50% of this molecularly adsorbed O2 desorbs via hole-mediated reactions during irradiation with ultraviolet (UV) photons. However, UV irradiation dissociates ∼20-45% of the chemisorbed O2, which we propose to occur through electron attachment reactions. In addition, weakly bound (physisorbed) O2 readily reacts with chemisorbed O2 during UV irradiation. These results show that the photochemistry of oxygen on TiO2(110) is both diverse and more complicated than previously appreciated.