Photocatalytic air-cleaning using TiO2 nanoparticles in porous silica substrate

For air-cleaning, TiO₂ photocatalysis represents one of the very efficient advanced oxidation processes (AOPs) that can decompose chemically and microbiologically stable volatile organic compounds (VOCs). However, the photocatalytic activity of nanocrystalline TiO₂ powders can be significantly suppressed due to TiO₂’s poor adsorption characteristics for organic compounds and its relatively low surface area. The present study sought to solve this problem by immobilising nanocrystalline TiO₂ in the porous silicate substrate. Two titania sources were used in an aqueous solution form: a suspension from a TiO₂ producer in Slovenia, Cinkarna Celje (CC-40) and a TiO₂ sol, prepared by a low-temperature synthesis developed at the University of Nova Gorica (TiO₂-UNG). Two different types of mesoporous silica were used: SBA-15 with an ordered hexagonal pore arrangement and KIL-2 with disordered inter-particle mesoporosity. The structural characteristics, adsorption properties and photocatalytic activity of catalysts deposited on aluminium plates as thin films were investigated. CC-40 exhibited higher adsorption and photocatalytic activity than TiO₂-UNG due to the greater quantity of Ti-OH groups on its surface. The addition of mesoporous silica led to higher adsorption and catalytic activity for both TiO₂ sources. SBA-15 was more efficient than KIL-2.