Interfacial C−S Bonds of g‐C3N4/Bi19Br3S27 S‐Scheme Heterojunction for Enhanced Photocatalytic CO2 Reduction**

Step-scheme (S-scheme) heterojunctions have been extensively studied in photocatalytic carbon dioxide (CO₂ ) reduction due to their excellent charge separation and high redox ability. The built-in electric field at the interface of a S-scheme heterojunction serves as the driving force for charge transfer, however, the poor interfacial contact greatly restricts the carrier migration rate. Herein, we synthesized the g-C₃ N₄ /Bi₁₉ Br₃ S₂₇ S-scheme heterostructure through in situ deposition of Bi₁₉ Br₃ S₂₇ (BBS) on porous g-C₃ N₄ (P-CN) nanosheets. The C-S bonds formed at the interface help to enhance the built-in electric field, thereby promoting the charge transfer and separation. As a result, the CO₂ reduction reaction performance of 10 %Bi₁₉ Br₃ S₂₇ /g-C₃ N₄ (BBS/P-CN) reaches 32.78 μmol g^-1 h^-1 , which is 341.4 and 18.7 times higher than that of pure BBS and P-CN, respectively. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) prove the presence of chemical bonds (C-S) between the P-CN and BBS. The S-scheme charge-transfer mechanism was analyzed via XPS and density functional theory (DFT) calculations. This work provides a new idea for designing heterojunction photocatalysts with interfacial chemical bonds to achieve high charge-transfer and catalytic activity.