Photocatalytic conversion of CO2 in water over Ag-modified La2Ti2O7

• Photocatalytic conversion of CO2 to CO in pure water was achieved over Ag-modified La2Ti2O7 under UV light irradiation.
• Oxidation of water (evolution of O2) could be observed during the photocatalytic reaction.
• The amounts of CO, H2, and O2 were produced in a stoichiometric ratio.
• The isotope labeling reaction using 13CO2 was carried out to confirm the origin of evolved CO gas.

We have found that Ag-modified La2Ti2O7 with a layered perovskite structure exhibits activity for the photocatalytic conversion of CO2 to CO in pure water. The evolution of O2 proves that H2O works as an electron donor for the photocatalytic conversion of CO2. CO was generated as the main product, and CO, H2, and O2 were produced in stoichiometric amounts. The crystallite size of La2Ti2O7 increased and the surface area decreased with increasing calcination temperature and time. Maximization of the photocatalytic activity of La2Ti2O7 was accomplished by making a trade-off between the crystallite size and surface area. In addition, the loading amount and modification method of the Ag cocatalyst also influenced the amount of CO evolved. An isotope labeling experiment using 13CO2 confirmed that the origin of evolved CO was not the residual carbon species on the La2Ti2O7 surface, but was rather the CO2 gas that was introduced during the experimental process.

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