Electrochemical conversion of carbon dioxide (CO2) into multi-carbon fuels and chemical feedstocks is important but remains challenging. Here, we report the stabilization of Cu(+)within a CuO-CeO(2)interface for efficient and selective electrocatalytic CO(2)reduction to ethylene under ambient conditions. Tuning the CuO/CeO(2)interfacial interaction permits dramatic suppression of proton reduction and enhancement of CO(2)reduction, with an ethylene faradaic efficiency (FE) as high as 50.0% at -1.1 V (vs.the reversible hydrogen electrode) in 0.1 M KHCO3, in stark contrast to 22.6% over pure CuO immobilized on carbon black (CB). The composite catalyst presents a 2.6-fold improvement in ethylene current compared to that of CuO/CB at similar overpotentials, which also exceeds many recently reported Cu-based materials. The FE of C(2)H(4)remained at over 48.0% even after 9 h of continuous polarization. The Cu(+)species are believed to be the adsorption as well as active sites for the activation of CO(2)molecules, which remain almost unchanged after 1 h of electrolysis. Further density functional theory calculations demonstrate the preferred formation of Cu(+)at the CuO-CeO(2)interface. This work provides a simple avenue to convert CO(2)into high-value hydrocarbons by rational stabilization of Cu(+)species.