Preparation, crystal structure, and photocatalytic activity of TiO2 films by chemical vapor deposition

Photocatalytic activities of TiO₂ films were experimentally studied. TiO₂ films with different crystal structures (amorphous, anatase, rutile) were prepared by a Low Pressure Metal Organic Chemical Vapor Deposition (LPMOCVD) at different reaction temperatures and also by a Sol-Gel method using TTIP (Titanium Tetra Iso-Pro-poxyde). The Effect of CVD preparation method, CVD reaction conditions, crystal structure and wave-length of UV light on the photocatalytic decomposition rate of methylene blue in aqueous solution were studied. First, the characteristics of CVD preparation of TiO₂ films, such as the CVD film growth rate, crystal structure and morphology of the grown TiO₂ films, were experimentally studied as a function of CVD reaction temperature. Secondly, photocatalytic activities of TiO₂ films were evaluated by using two types of photo-reactors. The results indicated that TiO₂ films prepared by CVD exhibit higher photocatalytic activity than a catalyst prepared by the Sol-Gel method. Among the CVD grown TiO₂ films, anatase and rutile showed high photocatalytic activities. However, amorphous TiO₂ films showed lower activities. The activity of the photocatalysts of anatase films was excellent under all types of UV-lamps. The activity of CVD-prepared anatase films was four to seven times higher than that of photocatalyst films prepared by the Sol-Gel method.