Gallium Oxide Assisting Ag-Loaded Calcium Titanate Photocatalyst for Carbon Dioxide Reduction with Water
Hongxuan Qiu, Akira Yamamoto, Hisao Yoshida
Abstract
An efficient and highly selective photocatalytic conversion of carbon dioxide (CO 2 ) into valuable chemicals such as carbon monoxide (CO) using water (H 2 O) 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 (CaTiO 3, CTO) photocatalyst showed a high selectivity to CO 2 reduction in aqueous solution and the Ag-loaded gallium oxide (Ga 2 O 3 ) photocatalyst showed a higher activity for both H 2 O splitting and CO 2 reduction, herein, a series of composite photocatalyst samples consisting of Ga 2 O 3 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/Ga 2 O 3 ) and a high selectivity of 95.0% (comparable to Ag/CTO) in the photocatalytic CO 2 reduction with H 2 O. In this composite photocatalyst, most of the electrons generated in the photoexcited Ga 2 O 3 part migrated to the minor CTO particles to contribute to the selective CO 2 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 Ga 2 O 3 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 CO 2 reduction with high efficiency.