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

It is highly desired yet challenging to strategically steer carbon dioxide (CO2) electroreduction reaction (CO2ER) 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 Cu2-xSe 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 angstrom in V-Se-Cu2-xSe sample can catalyze CO2ER 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.