Electrolyte electroreflectance (EER) has been used as an in situ probe for
determining the distribution of energy states at the surface of naked and m
etal-modified TiO2 film in contact with aqueous solution. The surface modif
ication of polycrystalline TiO2 films by electrodeposition of fine (a few n
anometers in size) metal particles has been shown to result in the appearan
ce of surface states with an energy of approximately 2.15 eV for Cu, 2.40 e
V for Pd, 2.50 and 2.30 eV (two peaks in the EER spectrum) for Pt, and 2.65
eV for Acr (the energy values are measured versus valence band edge of TiO
2). The important role of metal-induced surface states in the enhancement o
f charge exchange between conduction band of semiconductor oxide and metal
islets has been demonstrated using the electrocatalytic oxidation of boron
hydride as a model reaction.