AbstractRenewable electricity-powered CO evolution from CO₂ emissions is a promising first step in the sustainable production of commodity chemicals, but performing electrochemical CO₂ reduction economically at scale is challenging since only noble metals, for example, gold and silver, have shown high performance for CO₂-to-CO. Cu is a potential catalyst to achieve CO₂ reduction to CO at the industrial scale, but the C-C coupling process on Cu significantly depletes CO* intermediates, thus limiting the CO evolution rate and producing many hydrocarbon and oxygenate mixtures. Herein, we tune the CO selectivity of Cu by alloying a second metal Sb into Cu, and report an antimony-copper single-atom alloy catalyst (Sb₁Cu) of isolated Sb-Cu interfaces that catalyzes the efficient conversion of CO₂-to-CO with a Faradaic efficiency over 95%. The partial current density reaches 452 mA cm⁻² with approximately 91% CO Faradaic efficiency, and negligible C₂₊ products are observed. In situ spectroscopic measurements and theoretical simulations reason that the atomic Sb-Cu interface in Cu promotes CO₂ adsorption/activation and weakens the binding strength of CO*, which ends up with enhanced CO selectivity and production rates.