Hydrothermal synthesis of TiO2/SiO2 composite nanoparticles and their photocatalytic performances

Anatase (TiO2)/silica (SiO2) composite nanoparticles over the compositional range of SiO2 = 0-70.9mol% were directly formed from acidic precursor solutions of TiOSO4 and tetraethylorthosilicate by hydrolysis under mild hydrothermal conditions at 200 C. With increasing SiO2 content, the specific surface area of the as-prepared composite nanoparticles increased from 109 (SiO2 = 0 mol%) to 277 m(2)/g (SiO2 = 70.9 mol%), which was associated with an increase in the amorphous phase content. The composite nanoparticles with a unique microstructure, i.e., anatase crystallites 14-16 nm in size that exist separately due to the presence of an amorphous silica phase in the TiO2/SiO2 interface, showed enhanced photocatalytic activities for the decomposition of methylene blue (MB) in aqueous solution and better removal of NO gas in comparison with pure anatase-type TiO2. The highest photoactivity was obtained when the SiO2 content in the composites was 25.1 mol% for MB decomposition and 48.2 mol% for NO oxidation.