Photocatalytic Activities for Carbon Dioxide Reduction of TiO2 Microcrystals Prepared in SiO2 Matrices Using a Sol–Gel Method

Abstract
The size of TiO2 microcrystals embedded in SiO2 matrices, which were prepared using a mixed sol of TiO2 and SiO2 in ethanol, decreased with a decrease of the mole ratio of TiO2 to SiO2 in the sol. The prepared TiO2 microcrystals showed activities for photoreduction of CO2 to formate, methane and ethylene, and the quantum efficiencies for the production of these were increased with decreasing the size of the TiO2 microcrystals.