Photocatalytic decomposition of 2-propanol and acetone in air by nanocomposites of pre-formed TiO2 particles and mesoporous silica

The photocatalytic efficiency in the degradations of gaseous 2-propanol and acetone has been studied on nanocomposite materials prepared by embedding well-crystallized titanium dioxide (TiO2) particles (Degussa P25) into surfactant-templated mesoporous silica. The composite materials adsorbed the organic substances considerably in dark conditions and decomposed them completely to CO2 under photoirradiation. The efficiency was influenced remarkably by the surface modification of TiO2 particles. According to the transmission electron microscope observations, using carbon-coated TiO2 particles gave a composite MCT-C with well-ordered channels of the mesoporous silica, but not all the TiO2 particles were embedded in silica. MCT-C showed a high CO2 production rate comparable to that of pristine TiO2 (P25) when the concentrations of gaseous 2-propanol and acetone were as low as several ppm. On the other hand, using n-octadecyl-grafted TiO2 particles resulted in a composite MCT-S in which most of the TiO2 particles were well embedded in mesoporous silica, but the degree of channel-ordering was comparatively lower than that in MCT-C. The CO2 production rate for MCT-S was lower than that for P25. This is probably due to the deactivation of TiO2 surface by the silane-coupling reagent and/or the disorder of the mesopore channels. These composite photocatalysts could suppress the emission of unhealthy degradation products by adsorptive capacity of mesoporous silica.