Surface photovoltage spectra and photoelectrochemical properties of semiconductor-sensitized nanostructured TiO2 electrodes

Three kinds of TiO2 nanostructured thin films and their CdS-sensitized film s, consisting of different sizes of TiO2 nanoparticles prepared with differ ent methods, have been investigated. The surface photovoltage spectra (SPS) measurements indicate that the density of surface states on TiO2 is likely dependent upon the details of prepared methods. TiO2 particles prepared fr om basic sol have more surface states than that prepared from acidic sol. W hen the TiO2 thin films prepared using the TiO2 sols were sensitized by CdS particles, the SPS responses relative to the surface states on TiO2 from 3 50 to 800 nm were decreased. The photoelectrochemical properties of nanostr uctured TiO2 electrodes suggest that the fewer the surface states and the s maller the particle sizes of TiO2, the larger the photocurrent response. Fo r CdS sensitized TiO2 thin film electrode, it is shown that the semiconduct or sensitization is an efficient way to decrease the influence of surface s tates on the charge separation, and can improve the intensity of photocurre nt response. (C) 2001 Elsevier Science B.V. All rights reserved.