Efficient Electrocatalytic Reduction of CO2 to Ethanol Enhanced by Spacing Effect of CuCu in Cu2‐xSe Nanosheets

Abstract It is highly desired yet challenging to strategically steer carbon dioxide (CO 2 ) electroreduction reaction (CO 2 ER) toward ethanol (EtOH) with high activity, which provides a promising way for intermittent renewable energy reservation. Controlling spatial distance between the adjoining active centers and promoting the CC coupling progress are crucial to realize this purpose. Herein, ultrathin 2D Cu 2‐x Se is prepared with abundant Se vacancies, where the spatial distance between the CuCu around the Se vacancies is effectively shortened because of the lattice stress. Besides, the moderate spatial distance induced by Se vacancies can significantly decrease the Gibbs free energy of asymmetric *CO*CHO coupling progress, effectively change the local charge distribution, decrease the valence state of Cu atoms and increase the electron‐donating capacity of the dual active sites. Combining experimental observations and density functional theory simulations, the CuCu dual sites with spatial distance of 2.51 Å in V Se ‐Cu 2‐x Se sample can catalyze CO 2 ER to EtOH with high selectivity in a potential range from −0.4 to −1.6 V, and reach the highest faradaic efficiency of 68.1% at −0.8 V. This work reveals the influence of spacing effect on ethanol selectivity, and provides a new idea for future design of catalysts with chain elongation reaction, which can bring extensive attention.