Iodine-Modified Cu Heterointerface Enables Efficient CO ₂ -to-C ₂ H ₄ Conversion

Electrochemical CO 2 reduction to multicarbon (C 2+ ) products offers a promising route for chemical production. However, uncontrollable catalyst reconstruction and active site loss often limit selectivity and durability. Here, CuI/Cu 2 (OH) 3 NO 3 heterointerfaces undergo in situ electrochemical reduction to form Cu/Cu 2 O(I) structures, in which interfacial engineering generates low-coordination Cu δ+ sites and stabilizes iodine species under reaction conditions. The catalyst achieves 80% C 2+ Faradaic efficiency at –250 mA cm –2, including 61% for ethylene. In situ spectroscopic studies combined with theoretical calculations reveal that iodine stabilization at the Cu/Cu 2 O interfaces preserves Cu δ+ centers, enhances *CO adsorption, and lowers the energy barrier for C–C bond formation, thereby facilitating C 2+ production. This work establishes an interfacial strategy that couples active-site generation with iodine-assisted stabilization, providing mechanistic insights into selective CO 2 -to-C 2+ electroconversion.