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

Invited Paper SS1-WeA7
Photoexcitation of TiO@sub 2@ and the Chemistry of Electrons and Holes

Wednesday, November 17, 2004, 4:00 pm, Room 210B

Session: Metal Oxides and Clusters II: TiO@sub 2@ and Photocatalysis
Presenter: J.T. Yates, Jr., University of Pittsburgh
Authors: J.T. Yates, Jr., University of Pittsburgh
O. Diwald, Technical University of Vienna, Austria
D. Panayotov, University of Pittsburgh
T.L. Thompson, University of Pittsburgh
S.D. Walck, PPG Industries
T. Berger, Technical University of Vienna, Austria
E. Knözinger, Technical University of Vienna, Austria
M. Sterrer, Technical University of Vienna, Austria
Correspondent: Click to Email
TiO@sub 2@ is a useful photocatalyst for the destruction of trace quantities of organic molecules in the environment. Photoexcitation of TiO@sub 2@ occurs as a result of electron-hole pair excitation by UV radiation with energy above the bandgap (3.0 eV). It has been found that N doping from NH@sub 3@ may be used to lower the photothreshold for TiO@sub 2@ by 0.6 eV, whereas N doping by ion implantation using N@sub 2@@super +@ leads to an increase in the photothreshold energy. Excited electrons in TiO@sub 2@ may be detected by EPR or IR spectroscopy, and hole formation in the valence band region may be detected by EPR as O@super -@ species. Excited electrons are observed to transfer to adsorbed O@sub 2@ to produce the O@sub 2@@super -@ species (superoxide). An adsorbed organic molecule, containing both S and Cl moieties has been shown to accept excited electrons when it is bonded to the surface by the Cl moiety, but not when bound by the S moiety, indicating that charge transfer occurs preferentially into the polyfunctional molecule by means of the more electronegative attachment group.