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

Paper SS1-WeA4
Charge Transfer-Induced Water Splitting on the Rutile TiO@sub 2@(110) Surface

Wednesday, November 17, 2004, 3:00 pm, Room 210B

Session: Metal Oxides and Clusters II: TiO@sub 2@ and Photocatalysis
Presenter: R. Schaub, Interdisciplinary Nanoscience Center, Denmark
Authors: R. Schaub, Interdisciplinary Nanoscience Center, Denmark
E. Wahlström, Interdisciplinary Nanoscience Center, Denmark
E.K. Vestergaard, Interdisciplinary Nanoscience Center, Denmark
J. Matthiesen, Interdisciplinary Nanoscience Center, Denmark
F. Besenbacher, Interdisciplinary Nanoscience Center, Denmark
Correspondent: Click to Email
In direct contact with water, metal oxides are promising candidates in the search for renewable energy sources through direct photo-splitting of water as suggested by the seminal experiments of Fujishima and Honda@footnote 1@. TiO@sub 2@ is in particular one of the most utilized photo-chemically active systems for waste water treatment. For such photo-chemical processes, surface bound water as well as hydroxyls have been proposed to be the major species which are photo-activated to form hydroxyl radicals responsible for the photochemical activity. By means of scanning tunneling microscopy (STM) we have identified a number of different water-derived adsorbates on the TiO@sub 2@(110) surface, and the details of their formation were revealed from time-resolved STM movies. We find strong evidence that the diffusion of hydroxyls, as well as H@sub 2@O dissociation, is linked to the electronic properties of the substrate in the surface region, in a similar manner to our previous results reported for the interaction of O@sub 2@ molecules with TiO@sub 2@(110)@footnote 2@. Hence, charge transfer from the conduction band of the substrate to adsorbed molecules or reactants is identified as a key factor to understand their physical properties. In other words, chemical reactions can be promoted, not only by a localized "active" site (the traditional approach), but also by the more delocalized conduction band electrons. @FootnoteText@ @footnote 1@ A. Fujishima and K. Honda, Nature 238, 37 (1972).@footnote 2@ E. Wahlström et al., Science 303, 511 (2004).