Boosting charge migration kinetics using an Fe-S bridge for efficacious photocatalytic CO₂ reduction

Solar photocatalytic CO₂ reduction is a promising sustainable technology that can convert the most significant greenhouse gas into green fuel. However, the sluggish migration of electron-hole pairs hinders its wider practical applications. This study investigates the use of charge bridge and internal electric field mechanisms to accelerate charge transfer and separation, thus enhancing photocatalytic CO₂ reduction. We fabricated an Fe₂O₃/defective Bi₁₉Br₃S₂₇ (FO/DBBS) S-scheme heterojunction using an in situ hydrothermal method. The charge transfer via the Fe-S bond and its kinetics were studied. The FO/DBBS photocatalysts demonstrated robust visible-light-driven photocatalytic CO₂ reduction, achieving a high CO formation rate of 365.1 μmol g⁻¹ h⁻¹ with a selectivity of 93.9%. This performance significantly surpasses the yields from FO and DBBS alone. The improved photocatalytic CO₂ conversion is attributed to the Fe-S bond acting as a charge bridge and the built-in electric field within the S-scheme heterojunction, facilitating effective charge separation. Moreover, the photogenerated carriers on FO/DBBS showed a remarkably longer lifetime and decay time, surpassing those of FO. The surface potential of FO/DBBS also increased significantly under illumination. These findings reveal the critical role of the Fe-S bridge in promoting charge separation within the FO/DBBS S-scheme heterojunction, leading to efficacious photocatalytic CO₂ reduction. © 2025 The Royal Society of Chemistry.