Charge–Transfer Reversal at Cl‐Regulated Cu ₂ O/in ₂ S ₃ Interfaces Enables C─C Coupling for Selective CO ₂ Photoreduction to C ₂ H ₄

Efficient photocatalytic CO 2 reduction to C 2 H 4 is often constrained by sluggish C─C coupling kinetics and inefficient charge utilization. In this study, a Cl‐regulated reversed charge‐transfer pathway in Cu 2 O/In 2 S 3 heterojunction switches the photocatalytic CO 2 reduction product from CO to C 2 H 4 . This is attributed to Cl incorporation into the Cu 2 O lattice, which induces p‐type to n‐type conversion and reversed interfacial electric field (IEF), driving the transformation of Cu 2 O/In 2 S 3 (CIS) from a type‐II heterostructure to a Z‐scheme heterojunction in Cl‐Cu 2 O/In 2 S 3 (CCIS). The tailored charge transfer pathway enables Cl‐Cu 2 O to act as the CO 2 reduction center, and Cl‐modified electronic structure of Cu sites stabilizes *CO intermediates and lowers the C─C coupling barrier. Meanwhile, In 2 S 3 promotes H 2 O oxidation to provide sufficient protons and further accelerates the proton‐coupled electron transfer (PCET) process. Accordingly, CCIS exhibits an impressive C 2 H 4 evolution rate of 115.3 µmol g −1 h −1 and 91.4% selectivity in pure water, with an apparent quantum efficiency (AQE) of 5.4% at 420 nm. These findings highlight the significance of designing photocatalysts with favorable charge transport to tailor product selectivity in CO 2 photoreduction.