Abstract: TiO₂ nanoparticle film catalysts have been prepared in acid and basic conditions respectively, by method of the hydrolysis of TiCl₄. Their surface microstructures and surface energy levels were tested by infrared (IR) spectra and electrical field induced surface photovoltage spectra (EFISPS). The results demonstrate that surface properties of the two kinds of TiO₂ films are different. A new peak at 1350 cm^-1 due to superoxide radical appears in the IR spectrum of TiO₂ powder prepared by basic condition, while it is not found in the one prepared by acidic condition. Furthermore, a new peak at 390nm attributed to Ti³⁺ surface state is also found in EFISPS of the film obtained from basic colloid, whereas the peak disappears in EFISPS of the film obtained from acidic colloid. Photodegradation of phenol shows that photocatalytic activity is affected by surface properties of the film. Photocatalytic activity of the latter is better than that of the former confirms that Ti³⁺ reduces photocatalytic activity of catalyst.

Key words: TiO₂ nanoparticle film, surface state, photocatalytic activity