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 Ga2O3 (composite of α- and β-Ga2O3), pure α-, and β-Ga2O3 were examined for the photocatalytic conversion of CO2 by H2O. Ag-loaded β-Ga2O3 exhibited high selectivity for CO evolution if the proper loading methods and Ag nanoparticle contents were controlled. Using the chemical reduction method with NaH2PO2, 2 wt% Ag nanoparticles on β-Ga2O3 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-Ga2O3 for the reaction, it was found that the selectivity toward CO evolution was largely dependent on the amounts of Ag-loaded β-Ga2O3. The active sites where H2 molecules are formed are poisoned by the oxygen reduction reaction (ORR) at high amounts of Ag-loaded β-Ga2O3, resulting in a high selectivity for CO evolution.