Silica-modified anatase titanium dioxide was prepared by the hydrothermal method, with large surface area and high photocatalytic activity. Photocatalytic reduction of CO₂ was carried out to synthesize methanol in the aqueous suspension system of nano TiO₂. The catalyst was characterized by XRD, TEM, BET, UV-Vis diffuse reflectance and FTIR spectroscopy methods. The results showed formation of Si—O—Ti bond on the silica-modified titanium dioxide surfaces. The addition of silica to TiO₂ could restrain the growth of TiO₂ crystalline grain and enhance the surface area. The silica-modified titanium dioxides had significant blue shift in UV absorption compared to the bulk TiO₂. The reductive results of CO₂ showed that the nano SiO₂/TiO₂ already obtained obvious photocatalytic reduction activity. When the addition of silica to TiO₂ reached w(silica)＝3.5%, it gave the highest activity, producing 21.0 mg/L of methanol during 5 h reaction under the irradiation of 365 nm UV light.

Key words: titanium dioxide, hydrothermal, photocatalytic reduction, carbon dioxide