Facile synthesis of SiO2@TiO2 crystallite photocatalysts with enhanced interaction level and high light absorption efficiency

Abstract

SiO2@TiO2 crystallite photocatalysts with TiO2 crystallite core and porous amorphous SiO2/TiO2 shell were synthesized as photocatalyst by one-pot hydrothermal process using tetrabutyl titanate (TBOT) complex and ethyl orthosilicate (TEOS) as Ti and Si sources, respectively. The synthesized SiO2@TiO2 crystallite photocatalysts were characterized by transmission electron microscopy, X-ray diffraction pattern, UV–Vis diffuse reflectance spectrum and N2 adsorption–desorption isotherm. The interaction between TiO2 and SiO2, which is associated with photocatalytically active centers, is significantly improved through an enlargement in the interfacial area and the optimization of SiO2 fraction. The SiO2 modification does not lower the light absorption efficiency of TiO2 crystallite core owning to the low reflectivity of porous SiO2/TiO2 shell but endows the photocatalyst with easy separation behavior from aqueous solution. Furthermore, the reciprocal inhibition in volume shrinkage of TBOT complex- and TEOS-derived gel networks, as a consequence of mineralization asynchronism, increases the specific surface area and pore volume of the formed SiO2/TiO2 shell. The enhanced photocatalytic activity of SiO2@TiO2 crystallite photocatalysts by SiO2 modification is mainly ascribed to an increase in the interaction level, the high light absorption efficiency of SiO2@TiO2 crystallite photocatalysts and an enlargement in specific surface area of SiO2/TiO2 shell.