Preparation and characterization of ordered $TiO_2$ photocatalysts: Films and mesoporous structures

Abstract

Two different ordered TiO2 structures were prepared as sol-gel films coatedon glass andas mesoporous structures in order to study the effect, in 2-D or in 3-D, of bulk size on photocatalytic activity. Multilayer TiO2 films were coated on glass by the sol-gel dip coating method. The UV-VIS characteristics of the films, with respect to the number of coating layers, were monitored. UV-VIS measurements implied an ordered $TiO_2$ structure grown on ITO glass. The secondapproac h involved loading TiO2 in mesoporous SBA-15 powder. Ti-SBA-15 with Ti/Si (mole/mole) ratios between 0.05 and 0.30 were prepared and characterizedb y XRD and BET. Low-angle XRD results of Ti-SBA-15 samples demonstrated long-range order, and the mesoporous structure of SBA-15 was preserved under all titanium loadings. Wide-angle XRD results of Ti-SBA-15 samples demonstrated no crystallinity for $TiO_2$ at low Ti loadings (0.05 and 0.10), andt he onset of crystal formation at the 0.15 loading. The rutile phase was observed to be the dominant phase for lower loadings (0.20), whereas the anatase phase was dominant at higher loadings (0.25 and 0.30). BET surface areas decreased slightly with the addition of $TiO_2$ in SBA-15.