AVS 51st International Symposium
    Surface Science Tuesday Sessions
       Session SS-TuP

Paper SS-TuP39
O2-covered Reduced TiO2(110) Rutile: Dynamics and Chemistry

Tuesday, November 16, 2004, 4:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: Y. Wang, The University of Texas at Austin
Authors: Y. Wang, The University of Texas at Austin
G.S. Hwang, The University of Texas at Austin
Correspondent: Click to Email
The rutile TiO2(110) surface has been widely used as a catalyst for photochemical reactions and a support for transition metal catalysts. Molecular O2 adsorption plays an important role in determining the activity of TiO2 and supported metal catalysts. Surface bound oxygen species may directly influence chemical and photochemical processes occurring on TiO2. In addition, O2 exposure leads to significant structural changes of supported metal particles, which may in turn affect their catalytic activity. It has been found that molecular O2 adsorbs on TiO2(110) only when O-vacancies are present. Despite its importance, however the exact chemistry and dynamics of adsorbed O2 molecules on reduced TiO2(110) are still unclear. Using density functional theory calculations, we have investigated the adsorption and diffusion of oxygen species on the reduced TiO2 (110) surface. We have found that molecular O2 strongly binds not only to O-vacancies, but also to Ti(5c) neighbors, due to delocalization of unpaired electrons arising from removal of neutral bridging oxygen. Our results show that molecular O2 can jump across an oxygen vacancy and diffuse along a Ti(5c) row with moderate barriers. On the other hand, atomic O diffusion along a Ti(5c) row is rather unlikely at low temperatures (< 300K), because of the relatively higher probability of O-O formation by interaction with an adjacent bridging O(2c) atom. Based on our calculation results, we will discuss the diffusion and healing of O vacancies associated with O2 adsorption. We will also present the structure and energetics of higher coverage O2 adsorption and the chemistry of O2-covered reduced TiO2(110) surfaces.