Charge-Transfer Reversal at Cl-Regulated Cu₂O/in₂S₃ Interfaces Enables C─C Coupling for Selective CO₂ Photoreduction to C₂H₄.

Abstract

Efficient photocatalytic CO₂ reduction to C₂H₄ is often constrained by sluggish C─C coupling kinetics and inefficient charge utilization. In this study, a Cl-regulated reversed charge-transfer pathway in Cu₂O/In₂S₃ heterojunction switches the photocatalytic CO₂ reduction product from CO to C₂H₄. This is attributed to Cl incorporation into the Cu₂O lattice, which induces p-type to n-type conversion and reversed interfacial electric field (IEF), driving the transformation of Cu₂O/In₂S₃ (CIS) from a type-II heterostructure to a Z-scheme heterojunction in Cl-Cu₂O/In₂S₃ (CCIS). The tailored charge transfer pathway enables Cl-Cu₂O to act as the CO₂ reduction center, and Cl-modified electronic structure of Cu sites stabilizes *CO intermediates and lowers the C─C coupling barrier. Meanwhile, In₂S₃ promotes H₂O oxidation to provide sufficient protons and further accelerates the proton-coupled electron transfer (PCET) process. Accordingly, CCIS exhibits an impressive C₂H₄ 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 CO₂ photoreduction.