Optimizing the Carbon Dioxide Reduction Pathway through Surface Modification by Halogenation

Facilitating the charge separation of semiconductor photocatalysts to increase the photocatalytic CO 2 reduction activity has become a great challenge for sustainable energy conversion. Herein, the surface halogen‐modified defect‐rich Bi 2 WO 6 nanosheets have been successfully prepared to address the aforementioned challenge. Importantly, the modification of surface with halogen atoms is beneficial for the adsorption and activation for CO 2 molecules and charge separation. These properties have been analyzed by experimental and theoretical methods. DFT calculations revealed that the modification of the Bi 2 WO 6 surface with Br atoms can decrease the formation energy of the *COOH intermediate, which accelerates CO 2 conversion. All halogen‐modified defect‐rich Bi 2 WO 6 nanosheets showed an enhanced photocatalytic CO 2 reduction activity. Specifically, Br−Bi 2 WO 6 exhibited the best CO generation rate of 13.8 μmol g −1 h −1 , which is roughly 7.3 times as high as the unmodified defect‐rich Bi 2 WO 6 (1.9 μmol g −1 h −1 ). Moreover, in the presence of a cocatalyst (cobalt phthalocyanine) and a sacrificial agent (triethanolamine), Br−Bi 2 WO 6 exhibited an even further improved CO generation rate of 187 μmol g −1  h −1 . This finding provides a new approach to optimize the CO 2 reduction pathway of semiconductor photocatalysts, which is beneficial to develop highly efficient CO 2 reduction photocatalysts.