Electrocatalytic Reduction of CO 2 to Ethanol at Close to Theoretical Potential via Engineering Abundant Electron‐Donating Cu δ + Species

Abstract Electrochemical CO 2 reduction to liquid multi‐carbon alcohols provides a promising way for intermittent renewable energy reservation and greenhouse effect mitigation. Cu δ + (0< δ <1) species on Cu‐based electrocatalysts can produce ethanol, but the in situ formed Cu δ + is insufficient and easily reduced to Cu 0 . Here a Cu 2 S 1− x catalyst with abundant Cu δ + (0< δ <1) species is designedly synthesized and exhibited an ultralow overpotential of 0.19 V for ethanol production. The catalyst not only delivers an outstanding ethanol selectivity of 86.9 % and a Faradaic efficiency of 73.3 % but also provides a long‐term stability of Cu δ + , gaining an economic profit based on techno‐economic analysis. The calculation and in situ spectroscopic results reveal that the abundant Cu δ + sites display electron‐donating ability, leading to the decrease of the reaction barrier in the potential‐determining C−C coupling step and eventually making the applied potential close to the theoretical value.