Interfacial *Oh-Driven *OCCO Shielding Stabilizes Cu+ for Durable CO2-to-ethylene Electrocatalysis

Electrochemical CO2 reduction to ethylene (C2H4) offers a promising route for carbon upcycling, but the instability of Cu+ sites caused by *H attack remains a major barrier to durable selectivity. Here, we aim to stabilize Cu+ and enhance C-C coupling by regulating interfacial *OH-derived intermediate chemistry. Eu-doped Cu2O was designed to promote the formation of interfacial *OH species, which in turn form hydrogen bonds with *OCCO intermediates and amplify their dipole moment. This dynamic *OH-*OCCO interaction creates a physical shielding layer that suppresses *H adsorption on Cu+ sites while favoring *OCCO accumulation. As a result, the Eu-Cu2O catalyst delivers a C2H4 Faradaic efficiency of 40.3% at −1.2 V vs. RHE, 2.3 times higher than pristine Cu2O, and maintains stable C2H4 production for over 50 h. Combined experimental and theoretical analyses confirm that interfacial *OH-driven *OCCO engineering simultaneously promotes C-C coupling and preserves Cu+ integrity. This work provides a general strategy for constructing robust and selective copper-based electrocatalysts for durable CO2-to-C2H4 conversion.