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

Abstract

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.