AVS 59th Annual International Symposium and Exhibition
    Surface Science Thursday Sessions
       Session SS+EN+OX-ThM

Paper SS+EN+OX-ThM9
Site-Specific Photocatalytical Reactions of O2 on TiO2(110)

Thursday, November 1, 2012, 10:40 am, Room 21

Session: Catalysis and Photocatalysis on Oxides
Presenter: Z.-T. Wang, Pacific Northwest National Laboratory
Authors: Z.-T. Wang, Pacific Northwest National Laboratory
N.A. Deskins, Worcester Polytechnic Institute
I. Lyubinetsky, Pacific Northwest National Laboratory
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Photo-stimulated reactions on TiO2 have attracted much attention due to the variety of potential applications ranging from a hydrogen production by water splitting to environmental remediation through organic pollutant oxidation. In majority of these processes, the oxygen plays a crucial role. A better understanding of the fundamental aspects of oxygen on TiO2 can potentially lead to improvements or developments of the TiO2 applications. We present the direct observation at an atomic level with high-resolution scanning tunneling microscopy of photostimulated reactions of single O2 molecules on reduced TiO2(110) surfaces at 50 K. The critical relation between photoreactivity and adsorption sites on TiO2 is demonstrated. Two distinct reactions of O2 desorption and dissociation occur at different active sites of terminal Ti atoms and bridging O vacancies, respectively. These two reaction channels follow very different kinetics. While hole-mediated O2 desorption is promptly and fully completed, electron-mediated O2 dissociation is much slower and is quenched above some critical O2 coverage. Density functional theory calculations indicate that both coordination and charge state of an O2 molecule chemisorbed at specific site largely determine a particular reaction pathway.