Enhancement of CO Evolution by Modification of Ga 2 O 3 with Rare-Earth Elements for the Photocatalytic Conversion of CO 2 by H 2 O.

Modification of the surface of Ga2 O3 with rare-earth elements enhanced the evolution of CO as a reduction product in the photocatalytic conversion of CO2 using H2 O as an electron donor under UV irradiation in aqueous NaHCO3 as a pH buffer, with the rare-earth species functioning as a CO2 capture and storage material. Isotope experiments using 13 CO2 as a substrate clearly revealed that CO was generated from the introduced gaseous CO2 . In the presence of the NaHCO3 additive, the rare-earth (RE) species on the Ga2 O3 surface are transformed into carbonate hydrates (RE2 (CO3 )3 ·nH2 O) and/or hydroxycarbonates (RE2 (OH)2(3-x) (CO3 )x ) which are decomposed upon photoirradiation. Consequently, Ag-loaded Yb-modified Ga2 O3 exhibits much higher activity (209 μmol h-1 of CO) than the pristine Ag-loaded Ga2 O3 . The further modification of the surface of the Yb-modified Ga2 O3 with Zn afforded a selectivity toward CO evolution of 80%. Thus, we successfully achieved an efficient Ag-loaded Yb- and Zn-modified Ga2 O3 photocatalyst with high activity and controllable selectivity, suitable for use in artificial photosynthesis.