AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeA

Paper SS1-WeA3
The Oxygen Chemistry on Rutile Titanium Dioxide

Wednesday, November 17, 2004, 2:40 pm, Room 210B

Session: Metal Oxides and Clusters II: TiO@sub 2@ and Photocatalysis
Presenter: E.K. Vestergaard, Interdisciplinary Nanoscience Center, Denmark
Authors: E.K. Vestergaard, Interdisciplinary Nanoscience Center, Denmark
E. Wahlström, Interdisciplinary Nanoscience Center, Denmark
R. Schaub, Interdisciplinary Nanoscience Center, Denmark
J. Matthiesen, Interdisciplinary Nanoscience Center, Denmark
F. Besenbacher, Interdisciplinary Nanoscience Center, Denmark
Correspondent: Click to Email
The detailed understanding of the oxygen chemistry on titanium dioxide is an important issue for chemical and photo-chemical processes on this material. In particular, the detailed route for oxygen vacancy filling through oxygen exposure is important to understand the change of surface reactivity upon re-stoichiometrization. We present STM investigations resolving the atomic-scale details of adsorption, diffusion and reaction of oxygen molecules on the TiO@sub 2@(110) surface. By following the dynamical processes in real time with STM movies, we find that both the diffusion and the reaction between oxygen molecules have activation energies of approximately 0.35 eV and exhibit extremely low attempt frequencies of ~10@super 6@ s@super -1@. These findings are interpreted in a model where charge transfer processes from the TiO@sub 2@ conduction band to the adsorbed oxygen molecules govern the dynamics: Surface oxygen vacancies pin the chemical potential at 0.35 eV from the conduction band, in good agreement with the observed activation energy for diffusion of oxygen molecules.@footnote 1@ The same activation energy is also found for the dynamics of larger oxygen clusters containing three or more atoms. The interaction between such clusters and the bridging oxygen rows on the TiO@sub 2@(110) surface are found to be essential for the understanding of the ability of oxygen to heal the bridging oxygen vacancies. Finally, the presented STM results are discussed in the context of active support materials for Au catalysts. @FootnoteText@ @footnote 1@E. Wahlström et al., Science 303, 511 (2004).