Lanthanum bismuth oxide photocatalysts for CO2 reduction to CO with high selectivity

Abstract

Developing suitable photocatalysts is critical for CO₂ photoreduction processes using solar energy. Here, three kinds of lanthanum bismuth oxide semiconductors (La_0.225Bi_0.775O_1.5, La_0.6Bi_0.4O_1.5, and La_1.08Bi_0.92O_3.03) were found to exhibit activity for photocatalytic CO₂ reduction without any sacrificial agent. These photocatalysts showed 98% selectivity for CO₂ conversion to CO. Among these photocatalysts, La_0.225Bi_0.775O_1.5 exhibited the best performance (33.2 μmol g⁻¹) for CO₂ photoreduction, which was approximately twice that of La_0.6Bi_0.4O_1.5 and La_1.08Bi_0.92O_3.03. La_0.225Bi_0.775O_1.5 had a higher CO₂ adsorption capacity and more negative conduction band position than the other two photocatalysts. Furthermore, time-resolved fluorescence decay spectroscopy showed that La_0.225Bi_0.775O_1.5 had a much longer emission lifetime than La_0.6Bi_0.4O_1.5 and La_1.08Bi_0.92O_3.03, indicating the reduced recombination of photogenerated electrons and holes in La_0.225Bi_0.775O_1.5. We proposed a lattice oxygen-mediated mechanism for CO₂ photoreduction over La_0.225Bi_0.775O_1.5 in this study.