Highly selective conversion of CO2 to CO at Bi defect-modified Bi2WO6 nanosheets

Abstract

Photocatalytic conversion of CO₂ into profitable chemical products is crucial to solving energy problems and reducing the greenhouse effect, but achieving effective separation of photogenerated charge pairs and favorable reaction pathway remain to be a grand challenge in designing highly photoactive materials for efficient catalysis. In this work, we successfully integrated bismuth (Bi) defects into Bi₂WO₆ nanosheets (BWO-2) utilizing an anion-exchange approach, which improved the separation of charge carriers generated by photos. Notably, the incorporation of Bi defects resulted in a notable increase in the lifetime of photogenerated charge carriers in Bi₂WO₆ nanosheets, extending from 7.03 ns to 23.68 ns as demonstrated by time-resolved photoluminescence measurement, thereby significantly improving the separation of photogenerated carriers of charge. Therefore, BWO-2 outperformed unmodified Bi₂WO₆ nanosheets by approximately 2.56 times in the photocatalytic reduction of CO₂ to CO, achieving nearly 100 % selectivity and a CO production rate of 39.76 μmol·g⁻¹·h⁻¹ upon visible light with an intensity of 280 mW·cm⁻². Furthermore, in-situ FTIR spectroscopy unambiguously tracks the dynamic formation of *COOH intermediates during photocatalytic CO₂ reduction on BWO-2 surfaces. Mechanistic analysis reveals that Bi defects function as bifunctional catalytic centers, synergistically enhancing reactant adsorption and activation through electron-deficient regions, thereby accelerating the kinetically limiting *COOH → *CO transformation. This defect-mediated conversion pathway directly promotes the highly selective photocatalytic conversion of CO₂ to CO. This study offers a practical way to create a superior active photocatalysts for the highly selective conversion of CO₂ to CO by combining metal defects.