(Invited) Photocatalytic Conversion of CO2 By H2o As an Electron Donor over Ag/ZnGa2O4/Ga2O3

Many research groups have already made significant progress in the field of water splitting to produce pure H2 and O2; in contrast, studies on the photocatalytic conversion of CO2 using H2O as a reductant are very few. This is because in such systems, overall water splitting occurs together with the reduction of CO2, resulting in H2 being the main product. Thus, it is very important to control the reduction of protons in the presence of both CO2 and H2O in order to achieve the reduction of CO2 by H2O. In this study, we found that Ag/ZnGa2O4/Ga2O3 exhibits a higher conversion of CO2 as compared to several photocatalysts reported previously. CO was evolved as the main product during the photocatalytic conversion of CO2 over 1 wt% Ag/ZnGa2O4/Ga2O3 under UV irradiation. H2 was simultaneously generated as the reduction product similar to CO, although the amount of H2 evolved was tiny as compared to that of CO. Expectedly, the evolution of O2 was observed together with those of CO and H2. After 7 h of photoirradiation, we obtained 815 μmol of CO, 65.7 μmol of H2, and 479 μmol of O2. The reaction could be carried out stably over three times, indicating that Ag/ZnGa2O4/Ga2O3 is very stable in water and under photoirradiation.