High selectivity toward CO evolution for the photocatalytic conversion of CO2 by H2O as an electron donor over Ag-loaded β-Ga2O3

In this work, the performances of Ag-loaded commercial Ga 2 O 3 (composite of α - and β -Ga 2 O 3 ), pure α -, and β -Ga 2 O 3 were examined for the photocatalytic conversion of CO 2 by H 2 O. Ag-loaded β -Ga 2 O 3 exhibited high selectivity for CO evolution if the proper loading methods and Ag nanoparticle contents were controlled. Using the chemical reduction method with NaH 2 PO 2 , 2 wt% Ag nanoparticles on β -Ga 2 O 3 produced CO with an activity of 201.3 μmol h −1 and selectivity of 83.5%. However, 8 wt% Ag nanoparticles were required to achieve the same selectivity when prepared using the photodeposition method. By varying the amount of Ag-loaded β -Ga 2 O 3 for the reaction, it was found that the selectivity toward CO evolution was largely dependent on the amounts of Ag-loaded β -Ga 2 O 3 . The active sites where H 2 molecules are formed are poisoned by the oxygen reduction reaction (ORR) at high amounts of Ag-loaded β -Ga 2 O 3 , resulting in a high selectivity for CO evolution. • Selectivity of CO over Ag-loaded Ga 2 O 3 depended on phase of Ga 2 O 3 very much. • Selectivity of CO over Ag-loaded Ga 2 O 3 depended on the loading method of Ag very much. • Oxygen reduction reaction (ORR) was probably critical to the selective evolution of CO over Ag-loaded Ga 2 O 3 .