AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS3-TuM

Paper SS3-TuM7
Oxygen Vacancies as Active Sites for Water Dissociation on Rutile TiO@sub 2@(110)

Tuesday, November 5, 2002, 10:20 am, Room C-112C

Session: Metals, Adsorbates, and Defects on TiO@sub 2@
Presenter: P. Thostrup, University of Aarhus, Denmark
Authors: P. Thostrup, University of Aarhus, Denmark
R. Schaub, University of Aarhus, Denmark
N. Lopez, Technical University of Denmark
E. Laegsgaard, University of Aarhus, Denmark
I. Stensgaard, University of Aarhus, Denmark
J.K. Norskov, Technical University of Denmark
F. Besenbacher, University of Aarhus, Denmark
Correspondent: Click to Email
Water dissociation on TiO@SUB 2@ is of fundamental interest as an example of a simple surface chemical process with significant applications. In addition, TiO@SUB 2@ is the material of choice for photochemical hydrogen production from water and for biocompatible implants. Earlier experimental studies report a minor degree of water dissociation on TiO@SUB 2@(110) while theoretical studies predict the dissociated state, or mixed dissociated-molecular states, to be most energetically favorable. Thus, even for this simple process we do not have a clear picture of the dissociation energetics and the active site for dissociation. Through an interplay between scanning tunneling microscopy experiments and density functional theory calculations, we determine unambiguously the active surface site responsible for the dissociation of water molecules adsorbed on rutile TiO@SUB 2@(110). Oxygen vacancies in the surface layer are shown to dissociate H@SUB 2@O through the transfer of one proton to a nearby oxygen atom, forming two hydroxyl groups for every vacancy. The amount of water dissociation is limited by the density of oxygen vacancies present on the clean surface exclusively. The dissociation process sets in as soon as molecular water is able to diffuse to the active site.@footnote 1@ @FootnoteText@ @footnote 1@ R. Schaub, P. Thostrup et al., Phys. Rev. Lett. 87, 266104 (2001).