Optimizing the Carbon Dioxide Reduction Pathway through Surface Modification by Halogenation

Facilitating the charge separation of semiconductor photocatalysts to increase the photocatalytic CO₂ reduction activity has become a great challenge for sustainable energy conversion. Herein, the surface halogen-modified defect-rich Bi₂ WO₆ 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 CO₂ molecules and charge separation. These properties have been analyzed by experimental and theoretical methods. DFT calculations revealed that the modification of the Bi₂ WO₆ surface with Br atoms can decrease the formation energy of the *COOH intermediate, which accelerates CO₂ conversion. All halogen-modified defect-rich Bi₂ WO₆ nanosheets showed an enhanced photocatalytic CO₂ reduction activity. Specifically, Br-Bi₂ WO₆ 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 Bi₂ WO₆ (1.9 μmol g^-1 h^-1 ). Moreover, in the presence of a cocatalyst (cobalt phthalocyanine) and a sacrificial agent (triethanolamine), Br-Bi₂ WO₆ exhibited an even further improved CO generation rate of 187 μmol g^-1  h^-1 . This finding provides a new approach to optimize the CO₂ reduction pathway of semiconductor photocatalysts, which is beneficial to develop highly efficient CO₂ reduction photocatalysts.