Sustained Direct Electro-epoxidation of Ethylene via a Strain-Gradient CuO-Ag Interface.

Direct electrochemical ethylene epoxidation using water as the oxygen source offers a sustainable alternative to conventional thermal processes, but practical implementation is constrained by insufficient ethylene adsorption and the inherent instability of the critical OO* intermediate. Here we show that a CuO/Ag catalyst engineered with coupled strain and electronic properties promotes exposure of metastable Ag(111) facets to strengthen ethylene adsorption and establishes a dual-reagent confinement system that enriches H2O and C2H4 at respective interfacial domains. Characterization and simulation reveal that dynamic charge oscillations at the interface induce an electron flow from Ag to CuO, which facilitates C=C bond activation and stabilizes the OO* intermediate by suppressing O-O bond cleavage. In a membrane electrode assembly reactor, a stable ethylene oxide production rate of 345 μmol·cm-2·h-1 is achieved at 50 mA·cm-2 over 60 hours, with a Faradaic efficiency of 45.6% and a selectivity of 92.8%. This work validates interfacial strain and electronic properties as a viable strategy for sustainable electrified synthesis, as exemplified by the continuous direct epoxidation of ethylene.