Surface-halogenation-induced atomic-site activation and local charge separation for superb CO₂ photoreduction

Solar-energy-driven CO₂ conversion into value-added chemical fuels holds great potential in renewable energy generation. However, the rapid recombination of charge carriers and deficient reactive sites, as two major obstacles, severely hampers the photocatalytic CO₂ reduction activity. Herein, a desirable surface halogenation strategy to address the aforementioned concerns over a Sillén-related layer-structured photocatalyst Bi₂O₂(OH)(NO₃) (BON) is demonstrated. The surface halogen ions that are anchored on the Bi atoms by replacing surface hydroxyls on the one hand facilitate the local charge separation, and, on the other hand, activate the hydroxyls that profoundly boost the adsorption of CO₂ molecules and protons and facilitate the CO₂ conversion process, as evidenced by experimental and theoretical results collectively. Among the three series of BON-X (X = Cl, Br, and I) catalysts, BON-Br shows the most substantially enhanced CO production rate (8.12 µmol g⁻¹ h⁻¹) without any sacrificial agents or cocatalysts, ≈73 times higher than that of pristine Bi₂O₂(OH)(NO₃), also exceeding that of the state-of-the-art photocatalysts reported to date. This work presents a surface polarization protocol for engineering charge behavior and reactive sites to promote photocatalysis, which shows great promise to the future design of high-performance materials for clean energy production.