Pt-TiO2 thin films on glass substrates as efficient photocatalysts

Photocatalytic Pt-TiO sub(2) thin films of various thicknesses (ca. 20 to 100 nm) were prepared on Vycor glass substrates by spray-coating. The photocatalytic activity of the films was examined through the dehydrogenation of methanol in aqueous solution. The plot of the activity against the thickness of the film gave a sigmoidal curve. A drastic increase in activity was observed at about 50 nm thickness. From thin-film X-ray diffraction measurements of the films it was revealed that anatase was formed at a thickness of more than 50 nm, whereas amorphous TiO sub(2) was formed at thicknesses of less than 50 nm. The increase of activity was, therefore, attributed to the formation of anatase. Compared with powder catalysts, the thin films showed a remarkable improvement in specific photocatalytic activity due to the high dispersion of the catalyst.