Bifunctional Bi-OOH Motifs for Oxygen-Promoted CO2 Photoreduction via Inhibition of Oxygen Reduction

Abstract Photocatalytic CO2 reduction reaction from practical gas sources is often severely compromised by the competitive O2 reduction reaction. Herein, we report an approach to switch O2 from a competitor into a promoter by arresting the oxygen reduction reaction pathway at the *OOH intermediate stage on BiOBr photocatalysts. The introduction of oxygen vacancies (VO) facilitates O2 reduction to *OOH, which is robustly anchored by VO-induced Lewis acidic Bi sites to form stable Bi-OOH motifs. The Bi-OOH motifs arrest further oxygen reduction pathways and preferentially adsorb CO2 to stabilize *COOH intermediates. A clear linear correlation between the VO concentration and the activity further verifies the vital role of these sites. The BiOBr-VO-0.7 photocatalyst with an optimized VO concentration achieves a 3.4-fold enhancement under 20% O2 (69.2 μmol g–1 h–1) and a 2.9-fold enhancement under simulated flue gas compared to anaerobic conditions for CO2 reduction to CO. Isotope-labeling experiments with 13C confirmed that the CO originated from CO2 reduction. Its practical viability is further demonstrated under natural sunlight and ambient air with a CO generation rate of 5.6 μmol g–1 h–1. This work provides a paradigm shift in the design of catalysts that can use real CO2 sources.