Scalable ampere-level CO₂ electroreduction to ethylene enabled by descriptor-guided oxygen affinity engineering

The electroreduction of CO₂ to ethylene using renewable electricity offers a sustainable approach for greenhouse gas mitigation. However, the efficient ethylene production is challenged by sluggish C-C coupling and wide product distribution. Guided the energy changes associated with C-C coupling and C-O cleavage as descriptors for ethylene electrosynthesis, we predict and synthesize unsaturated MgO_1-x anchored on Cu via an electrochemical-induced phase separation method. Electrochemical evaluation of this catalyst achieves an ethylene Faradaic efficiency of 78.2% at 300 mA cm^-2 in a flow cell. Mechanism studies reveal the bifunctionality of MgO_1-x. On one side, chemical interaction of MgO_1-x with Cu domain stabilizes Cu⁺ and gives asymmetric Cu⁺···Cu⁰ pairs, facilitating the *CO-CHO coupling. On another side, the MgO_1-x with high oxygen affinity strengthens the binding with dual-carbon intermediate and promotes the C-O bond dissociation, accelerating ethylene formation. Ultimately, this catalyst delivers 60.7% ethylene selectivity at 25 A in membrane electrode assembly of 100 cm², equivalent to a C₂H₄ production rate of 1.1 L h^-1.