Non-Band-Gap Photoexcitation of Hydroxylated TiO2.
The photochemistry of TiO2 has been studied intensively since it was discovered that TiO2 can act as a photocatalyst. Nevertheless, it has proven difficult to establish the detailed charge-transfer processes involved, partly because the excited states involved are difficult to study. Here we present evidence of the existence of hydroxyl-induced excited states in the conduction band region. Using two-photon photoemission, we show that stepwise photoexcitation from filled band gap states lying 0.8 eV below the Fermi level of rutile TiO2(110) excites hydroxyl-induced states 2.73 eV above the Fermi level that has an onset energy of ∼3.1 eV. The onset is shifted to lower energy by the coadsorption of molecular water, which suggests a means of tuning the energy of the excited state.
Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, United Kingdom.|London Centre for Nanotechnology, University College London , 17-19 Gordon Street, London WC1H 0AH, United Kingdom.
Yu
Y
Zhang
Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, United Kingdom.|London Centre for Nanotechnology, University College London , 17-19 Gordon Street, London WC1H 0AH, United Kingdom.
Daniel T
DT
Payne
Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, United Kingdom.|London Centre for Nanotechnology, University College London , 17-19 Gordon Street, London WC1H 0AH, United Kingdom.
Chi L
CL
Pang
Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, United Kingdom.
Helen H
HH
Fielding
Department of Chemistry, University College London , 20 Gordon Street, London WC1H 0AJ, United Kingdom.|London Centre for Nanotechnology, University College London , 17-19 Gordon Street, London WC1H 0AH, United Kingdom.
Geoff
G
Thornton
D002384:Catalysis; D006900:Hydroxylation; D008027:Light; D014025:Titanium / Q000737:chemistry*
C009495:titanium dioxide; D014025:Titanium
2PPE; TiO2; charge transfer; electron dynamics; hydroxyls; photocatalysis