Preparation of Ti-Si binary oxide thin film photocatalysts by the application of an ionized cluster beam method.

Ti-Si binary oxide thin films with various Ti contents were prepared in a dry process by using an Ionized Cluster Beam (ICB) deposition method with multi ion sources. From the results of UV-VIS measurements, the transmittance of these binary oxide thin films is very high compared to pure TiO2 thin films, indicating that the Ti-oxide exists in a highly dispersed state in the SiO2 matrices. The EXAFS spectra of these thin films with lower Ti content exhibited only a sharp preedge peak attributed to the highly dispersed Ti-oxide species which differs from the peaks of anatase TiO2 thin films. UV light irradiation of these Ti-Si binary oxide thin films in the presence of NO were found to lead to the evolution of N2 and O2 with a good linearity against the irradiation time. The lower the Ti content, the higher the reactivity and the selectivity for the formation of N2 were. These results clearly indicate that the highly dispersed Ti-oxide species plays an important role in the formation of N2 and O2 for the photocatalytic decomposition of NO under UV light irradiation.