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

Abstract

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, N₂ sorption analysis at 77 K and activity evaluation. A catalyst of 7 wt% Ag on SrTiO₃ with hydrothermal synthesis at 150 °C and 22 h was found to exhibit the highest photocatalytic activity in MF formation rate of 3,006 μmol/(h g cat), which was more remarkable than that of pristine SrTiO₃.

Graphical Abstract

When the SrTiO₃ is irradiated by UV light of suitable wavelength with sufficient photonic energy (hν), 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.