Electrolyte electroreflectance study of TiO2 films modified with metal nanoparticles

Electrolyte electroreflectance (EER) has been used as an in situ probe for determining the distribution of energy states at the surface of naked and metal-modified TiO2 film in contact with aqueous solution. The surface modification of polycrystalline TiO2films by electrodeposition of fine (a few nanometers in size) metal particles has been shown to result in the appearance of surface states with an energy of approximately 2.15 eV for Cu, 2.40 eV for Pd, 2.50 and 2.30 eV (two peaks in the EER spectrum) for Pt, and 2.65 eV for Ag (the energy values are measured versus valence band edge of TiO2). The important role of metal-induced surface states in the enhancement of 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.