Effect of the in situ addition of chromate ions on H2 evolution during the photocatalytic conversion of CO2 using H2O as the electron donor

Chromium-based cocatalysts influence H2 evolution during the overall water splitting reaction in the photocatalytic conversion of CO2 in the presence of H2O as an electron donor. To clarify the mechanism by which chromium species promote or suppress H2 evolution, the reaction was carried out in the presence of α- and β-Ga2O3, NaTaO3, ZnTa2O6, and SrTa2O6 photocatalysts with the in situ addition of chromate ions. We found that chromate ions suppress H2 evolution during the photocatalytic conversion of CO2 by H2O when the surface of the photocatalyst is highly protonated.