| AVS 56th International Symposium & Exhibition | |
| Surface Science | Monday Sessions |
| Session SS2-MoM |
| Session: | TiO2 Surfaces and Interfaces |
| Presenter: | N.G. Petrik, Pacific Northwest National Laboratory |
| Authors: | N.G. Petrik, Pacific Northwest National Laboratory G.A. Kimmel, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
The interaction of oxygen with TiO2 is critical for a variety of applications including the photooxidation of organic materials, purification of water and air, and (potentially) photocatalytic water splitting. In this paper, the thermal and non-thermal (photon- and electron-stimulated) reactions of molecular oxygen are studied versus oxygen coverage on reduced TiO2(110). At low temperatures, two O2 can chemisorb per oxygen vacancy (VO).1 Hydroxylation of the vacancies (via dissociative water adsorption) does not affect the amount of chemisorbed O2. Most of the chemisorbed molecules do not desorb upon annealing to 700 K, but react. The thermal reactions of the chemisorbed O2 depend strongly on the oxygen coverage. When 1 O2 is adsorbed in an oxygen vacancy, the molecule dissociates upon annealing above ~200 K, healing the vacancy and depositing an oxygen adatom on the Ti row. At an oxygen coverage of 2 O2 per oxygen vacancy, the oxygen converts to another species (perhaps tetraoxygen or ozonide) in temperature range of 200 K < T < 400 K. This species subsequently decomposes at higher temperatures. The photon- (and electron-) stimulated desorption of chemisorbed oxygen are also very sensitive to the oxygen coverage. The results demonstrate that the reactivity of TiO2(110) with O2 is primarily controlled by the amount of electron-donating surface species on the surface (VO’s and/or hydroxyls).2
1 G.A. Kimmel and N.G. Petrik, Phys. Rev. Lett. 100, 196102 (2008).
2 N.G. Petrik, Z. Zhang, Y. Du, Z. Dohnalek, I. Lyubinetsky, G.A. Kimmel, JCP submitted