Coordination modulation of iodide at the CuI-Cu₂O interface to stabilize Cu⁺ and promote carbon dioxide-to-ethylene...

Electrochemical conversion of CO₂ to value-added chemicals is a promising carbon recycling strategy for mitigating CO₂ emissions from fossil fuels and addressing associated environmental challenges. In copper-based catalysts, Cu⁺ species promote the reduction of CO₂ to multi‑carbon products, such as ethylene (C₂H₄). However, under typical electroreduction, Cu⁺ is prone to reduction to Cu⁰, leading to degradation of catalytic performance and poor stability. Herein, we present an interfacial engineering strategy to design a CuI-Cu₂O composite catalyst with densely packed Cu₂O nanoparticles on tetrahedral CuI substrates and self-stabilizing Cu⁺ ability for selective CO₂ electroreduction to C₂H₄. Density functional theory (DFT) calculations and spectroscopic characterizations demonstrated that the CuI-Cu₂O catalyst combined the efficient generation of *CO intermediates by Cu₂O with the efficient CC coupling functionality of CuI, and the iodide ions within the catalyst autonomously modulated the copper oxidation state to stabilize Cu⁺, collectively enhancing CO₂-to-C₂H₄ selectivity. Consequently, the CuI-Cu₂O catalyst achieved a C₂H₄ Faradaic efficiency of 62.98 ± 1.05% along with a high current density of 275.16 mA·cm^-2 at -0.97 V vs. the reversible hydrogen electrode (RHE). In the stability test, the CuI-Cu₂O catalyst operated stably for over 16 h at a current density of approximately 279.95 mA·cm^-2. This study provides a catalyst design strategy that simultaneously enhances *CO supply and CC coupling while autonomously modulating the active Cu⁺ state, offering an effective approach for achieving stable and highly selective CO₂-to-C₂H₄ conversion.