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

Abstract

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.