Highly Selective CO ₂ Electroreduction to Ethylene on Stable Cu ⁰ /Cu ⁺ Interfaces by Local Microenvironment Modulation

ABSTRACT Electrochemical CO 2 reduction to multicarbon (C 2+ ) products with high selectivity at industrial current densities using a membrane electrode assembly (MEA) electrolyzer in neutral electrolytes holds a great promise for carbon neutrality. However, the complex reaction pathways and low selectivity for C 2+ products have hindered further development. Herein, an oxygen vacancy‐engineered CuO nanoflower catalyst was designed to construct stable Cu 0 /Cu + active interfaces and induce a localized alkaline microenvironment, effectively suppressing the competing hydrogen evolution reaction (HER) while enhancing ethylene (C 2 H 4 ) selectivity. In situ spectroscopic characterization confirmed the stability of the Cu 0 /Cu + active sites and their high *CO surface coverage. Multiphysics simulations combined with density functional theory (DFT) calculations revealed that the stable Cu 0 /Cu + interface coupled with the localized alkaline microenvironment reduces the energy barrier for asymmetric C─C coupling, thereby boosting C 2 H 4 selectivity. The optimized catalyst achieved remarkable C 2 H 4 Faradaic efficiencies of 66.8% in alkaline and 66.1% in neutral electrolyte at a current density of 200 mA cm – 2 . This strategy of stabilizing Cu 0 /Cu + interfaces coupled with microenvironment modulation offers novel insights for enabling highly selective CO 2 ‐to‐C 2 H 4 electrosynthesis at high current densities.