Study of adsorption-assisted photocatalytic oxidation of benzene with TiO2/SiO2 nanocomposites

TiO2/SiO2 composite photocatalysts were prepared via a simple reflux-stir process. These composites exhibit a highly distributed state between TiO2 (P25) and fumed silica (SiO2) nanoparticles, and the SiO2 nanoparticles surround the TiO2 crystalline grains closely. The photoactivity of the composites was investigated by photocatalytic oxidation of gaseous benzene. By adjusting the Ti/Si mole ratio from 50:1 to 1:1, the photocatalytic efficiency of the TiO2/SiO2 composites ascends firstly and then decreases. The optimum Ti/Si mole ratio is 30:1, and the photocatalytic efficiency reaches 92.3% within 120 min, which is 6.8 times higher than that of P25. Additionally, recycled tests which performed ten times demonstrate the nanocomposites possess a pretty good recyclability. The excellent photocatalytic performances can be chiefly attributed to the good dispersion state between TiO2 and SiO2. The special structure helps the formation of a high population of hydroxyl groups on the catalysts surface, and these hydroxyl groups greatly improve the charge separation efficiency and the reaction rate. In addition, the enhanced adsorption powers to water vapor and benzene also contribute to the high photoactivity.

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► Highly distributed TiO2/SiO2 composites were prepared via a simple reflux-stir process.
► The composites show superior photocatalytic oxidation efficiency and recyclability.
► Different Ti/Si molar ratios of TiO2/SiO2 influence the photocatalytic activity greatly.
► Enhanced adsorptive power to water vapor and benzene accelerate the reaction rate.
► A high population of surface hydroxyl groups leads to the notable photoactivity.