Photocatalytically Reducing CO2 to Methyl Formate in Methanol Over Ag Loaded SrTiO3 Nanocrystal Catalysts

Ag-SrTiO3 nanocrystal photocatalysts were prepared by hydrothermal synthesis method for reducing CO2 to methyl formate (MF) in methanol via ultraviolet irradiation. CO2 was reduced to MF by electrons on conduction band of the photocatalyst. In order to obtain a high rate of MF evolution, we researched and optimized the preparation procedure of Ag-SrTiO3 by changing the Ag dosage, hydrothermal temperature and time. The as synthesized photocatalysts were characterized with X-ray diffraction, UV-Vis absorption spectra, transmission electron microscope, N-2 sorption analysis at 77 K and activity evaluation. A catalyst of 7 wt% Ag on SrTiO3 with hydrothermal synthesis at 150 A degrees C and 22 h was found to exhibit the highest photocatalytic activity in MF formation rate of 3,006 mu mol/(h g cat), which was more remarkable than that of pristine SrTiO3. When the SrTiO3 is irradiated by UV light of suitable wavelength with sufficient photonic energy (h nu), photo-generated electron-hole pairs were created, part of the excited electrons and holes recombined together and radiated out heat, while rest part would react with the reactants near the SrTiO3 surface. It was certain electrons transmitting to the surface of Ag particle that avoided their recombination with holes, resulting in effective extension of the life-span of the electron-hole pairs.