AVS 52nd International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM2
Oxygen Adsorption, Diffusion, and Reaction on a Reduced TiO@sub 2@(110) Surface

Tuesday, November 1, 2005, 8:40 am, Room 203

Session: Defects on Oxide Surfaces
Presenter: D. Pillay, The University of Texas at Austin
Authors: D. Pillay, The University of Texas at Austin
G. Hwang, The University of Texas at Austin
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The rutile TiO@sub 2@(110) surface has been widely used as a catalyst for photochemical reactions and a support for transition metal catalysts. Molecular oxygen adsorption plays an important role in determining the activity of TiO@sub 2@ and supported metal catalysts. Surface bound oxygen species may directly influence chemical and photochemical processes occurring on TiO@sub 2@. In addition, O@sub 2@ exposure leads to significant structural changes of supported metal particles, which may in turn affect their catalytic activity. It has been found that O@sub 2@ adsorbs on TiO@sub 2@(110) only when O-vacancies are present. Despite its importance, however the chemistry and dynamics of adsorbed oxygen species on a Au-covered reduced TiO@sub 2@(110) surface are still unclear. Using density functional theory calculations, we have investigated the adsorption and diffusion of oxygen species on the reduced TiO@sub 2@(110) surface. We have found that O@sub 2@ strongly binds not only to O-vacancies, but also to Ti(5c) neighbors, due to delocalization of unpaired electrons arising from the removal of neutral bridging oxygen atoms. Our results show that O@sub 2@ can jump across an oxygen vacancy and diffuse along a Ti(5c) row, with a moderate barrier that is significantly altered by the density of O vacancies. Based on our calculation results, we will discuss the diffusion and healing of O vacancies associated with O@sub 2@ adsorption, as a function of the vacancy density. We will also present the structure and energetics of higher coverage O@sub 2@ adsorption, as well as CO oxidation mechanisms on the reduced TiO@sub 2@(110) surface.