Mesoporous TiO2 microspheres with improved efficiency for photooxidation of volatile organic compounds

Abstract

Mesoporous hierarchical TiO2 microspheres have been prepared using titanium alkoxide and crown ether as a structure-directing agent in combination with a small amount of surfactant by sol–gel synthesis with or without hydrothermal treatment and characterized by SEM, TEM, XRD and BET measurements. Microspheres with a size range from 0.6 to 3.0 μm have been formed by agglomeration of primary anatase nanoparticles with crystallite size of ca. 10 nm. Almost all TiO2 microspheres have shown superior activity in photooxidation of volatile organic compounds to CO2 significantly higher than that of TiO2 Evonik P-25. Hydrothermal treatment of particles has increased photocatalytic activity of titania microspheres. It has been established that the introduction of small amounts of additives to the reacting system, in particular palmitic acid, during the synthesis of TiO2 microspheres not only significantly affects the texture characteristics of the obtained materials, but also significantly increases their photocatalytic activity. The outstanding photocatalytic activity of microspheres is a consequence of the dominant contribution of the developed mesopore system (large pore volume and diameter) in their hierarchical structural organization, which is formed by aggregation and agglomeration of anatase nanoparticles. Photoactivity of TiO2 microspheres is not always determined by the specific surface area of the sample.