La2O3-Modified LaTiO2N Photocatalyst with Spatially Separated Active Sites Achieving Enhanced CO2 Reduction

Activating CO2 molecule and promoting proton release from kinetically sluggish water oxidation are two important half-reaction processes for achieving efficient solar-driven conversion of CO2 to fuels. Here, an effective route is proposed that uses a solid base to modify photocatalyst with defects, aiming to simultaneously accelerate the two reaction processes. To verify this hypothesis, the La2O3 is decorated on surface of LaTiO2N with oxygen vacancies, achieving a twofold increase in CH4 yield rate for CO2 reduction. The prominent activity results from the following two effects: (1) The O2- in La2O3 as basic sites favors CO2 chemisorption in the form of CO32- species, greatly contributing to both the bending of O-C-O bond and the decrease of the lowest unoccupied molecule orbit energy of CO2 molecule. (2) The oxygen vacancies on LaTiO2N are beneficial in activating H2O to adsorbed OH, thus effectively decreasing the reaction barriers of water oxidation to release protons. The design concept of simultaneously activating the CO2 and H2O at different spatial sites may offer a new strategy to suppress the reverse reactions for efficient solar energy conversion.