Hydrothermal Synthesis of TiO2/SiO2 Composite Nanoparticles and Their Photocatalytic Performances

Abstract

Anatase (TiO2)/silica (SiO2) composite nanoparticles over the compositional range of SiO2 = 0-70.9 mol% 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 m2/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.