Gallium Oxide Assisting Ag-Loaded Calcium Titanate Photocatalyst for Carbon Dioxide Reduction with Water

An efficient and highly selective photocatalytic conversion of carbon dioxide (CO2) into valuable chemicals such as carbon monoxide (CO) using water (H2O) as an electron donor has been much attractive and deeply desired, which requires the development of advanced photocatalysts based on a functional design. As the Ag-loaded calcium titanate (CaTiO3, CTO) photocatalyst showed a high selectivity to CO2 reduction in aqueous solution and the Ag-loaded gallium oxide (Ga2O3) photocatalyst showed a higher activity for both H2O splitting and CO2 reduction, herein, a series of composite photocatalyst samples consisting of Ga2O3 and CTO were simply fabricated by calcination of the physical mixtures, followed by loading of a Ag cocatalyst with a photodeposition method. The optimized sample with the Ag cocatalyst exhibited both a high CO formation rate of 56.9 μmol h–1 (higher than that of Ag/Ga2O3) and a high selectivity of 95.0% (comparable to Ag/CTO) in the photocatalytic CO2 reduction with H2O. In this composite photocatalyst, most of the electrons generated in the photoexcited Ga2O3 part migrated to the minor CTO particles to contribute to the selective CO2 reduction reaction, which was evidenced by the selective photodeposition of Ag species on the CTO part. The selective CO formation originates from the property of Ag-loaded CTO photocatalyst as the active part in the composite photocatalyst. The Ga2O3 part functions as an antenna to receive the light and donate the photoexcited electrons to the much decorated Ag/CTO part, where the concentrated electrons would promote CO2 reduction with high efficiency.