Highly selective photocatalytic reduction of carbon dioxide with water over silver-loaded calcium titanate

The once reported Ag-modified CaTiO₃ photocatalyst was reexamined by optimizing the Ag loading amount and using a conventional photochemical reactor. This revealed that the Ag-modified CaTiO₃ photocatalyst actually showed both high production rate of CO (54 μmol h⁻¹) and excellent selectivity towards CO formation (94%) by suppressing the H₂ production via water splitting. It is suggested that the high photocatalytic performance originates from not only the optimized amount of cocatalyst and the high irradiation light intensity but also the high concentration of dissolved CO₂ that was achieved by a bubbling flow of CO₂ at the lower reaction temperature. These reaction conditions provided ca. 40 times higher CO formation rate. It was proposed that the deposited small Ag nanoparticles are the selective active sites for CO formation and the CaTiO₃ crystal surface produces H₂ preferably.