Formation of titania-silica mixed oxides in solvent mixtures and their influences for the photocatalytic CO₂ conversion to hydrocarbon

TiO₂-SiO₂ mixed oxide photocatalyst materials responsive to simulated solar light illumination have been synthesized by sol-gel method in various polar and nonpolar organic solvent mixtures. The photocatalysts were characterized by numerous experimental techniques and investigated for the photocatalytic conversion of CO₂ to CH₄. The TiO₂-SiO₂ mixed oxide photocatalysts prepared in the presence of nonpolar aromatic solvents such as xylene, toluene or benzene along with ethanol show high surface area, huge mesoporosity and enormous pore volume compared to the materials conventionally synthesized in a mixture of ethanol and hexane. The TiO₂-SiO₂ mixed oxide photocatalyst prepared in benzene along with ethanol yields 21.0 ppm g^-1 h^-1 of methane production; however the material synthesized in hexane shows negligible amount of methane production under simulated solar light irradiation. These results indicate that aromatic nonpolar solvents can tune the textural properties of photocatalysts compared to non-polar aliphatic solvents.