High temperature stable mesoporous anatase TiO2 photocatalyst achieved by silica addition

An aqueous sol-gel method was developed to synthesize a high temperature stable anatase titania photocatalyst by doping with silica. Doping was achieved in titania by the addition of silica sol prepared from tetra ethyl orthosilicate (TEOS). 1, 2, 5 and 15 mol% silica-titania mixed oxide were prepared and characterised by X-ray diffraction, Raman spectroscopy, surface area analysis and diffuse reflectance spectra. Fully anatase phase was obtained at 1000,C by the addition of 15 mol% silica. The 15Si-Ti ( 15 denotes mol% of silica) had a specific surface area of 187.3 m(2)/g at 500 degrees C and it retains a value of 93.0 m(2)/g at 800 degrees C, whereas the undoped one shows 48.7 m(2)/g at 500 degrees C and zero value at 800 degrees C. Moreover, the 15Si-Ti composition retains the pore diameter in the mesoporous range (4.6 nm) at this high temperature of 800 degrees C. The photocatalytic analysis showed that the system with silica added possessed a higher activity than pure titania. The 15Si-Ti sample calcined at 800 degrees C decolourised the methylene blue dye within 30 min (rate constant 0.084 min(-1)), whereas the undoped sample decolourised the dye after 180 min (rate constant 0.018 min(-1)). The present method of preparation offers the advantages of inexpensive precursor, homogeneous distribution of the dopant over titania at nano-level and enables control over the powder characteristics of titania. (c) 2008 Elsevier B.V. All rights reserved.