Preparation and Characterization of Ordered TiO_2 Photocatalysts: Films and Mesoporous Structures


Abstract: Two different ordered TiO_2 structures were prepared as sol-gel films coated on glass and as mesoporous structures in order to study the effect, in 2-D or in 3-D, of bulk size on photocatalytic activity. Multilayer TiO_2 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 second approach involved loading TiO_2 in mesoporous SBA-15 powder. Ti-SBA-15 with Ti/Si (mole/mole) ratios between 0.05 and 0.30 were prepared and characterized by 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), and the 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


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