Design of TiO₂-mesoporous silica composite photocatalysts and their application to water purification under irradiation of UV and visible light

Design of TiO₂ photocatalyst and mesoporous silica composites were carried out for application to water purification. Two different types of precursors (titanium ammonium oxalate and ammonium hexafluorotitanate) for anchoring of TiO₂ on mesoporous silica were adopted for comparative studies to show the roles of chemical constituents in both precursors. In the utilization of ammonium hexafluorotitanate, hydrophobic nature on the surface of mesoporous silica as well as the high crystallinity and visible light absorption performance of TiO₂ were achieved by the co-existence of fluorine and nitrogen during the decomposition of precursors to TiO₂ at elevated temperature. Based on these fascinating functions of composite photocatalyst, good photocatalytic activity was realized in the degradation of phenol in water under UV light (λ > 290 nm) irradiation. This composite photocatalyst also exhibited photocatalytic activity even under visible light (λ > 420 nm) irradiation.