High‐rate CO2‐to‐CH4 Electrosynthesis by Undercoordinated Cu Sites in Alkaline‐Earth‐Metal Perovskites with Strong Basicity

Abstract The electrochemical CO 2 reduction to CH 4 has been extensively demonstrated, but still suffers from relatively poor activity and requires high overpotentials especially at large electrolysis rates. Perovskite oxides (A x B y O) are one type of promising electrocatalyst for the CO 2 reduction due to their tunable electronic structures. In this work, a Ca 2 CuO 3 perovskite oxide catalyst is developed with alkaline‐earth A‐sites, featuring an inherently strong basic strengthand outstanding capability for CO 2 adsorption, as well as the undercoordinated Cu sites generated through partial surface Ca 2+ cation leaching. The Ca 2 CuO 3 catalyst exhibitsa high partial current density of 517 ± 23 mA cm −2 for producing CH 4 at a low applied potential of −0.30 V versus reversible hydrogen electrode, which further reached to a peak value of 1452 ± 156 mA cm −2 . Density functional calculations show that the undercoordinated Cu sites allowed to promote the hydrogenation of * CO and subsequent * CHO intermediates, thus leading to the high CH 4 activity. This work suggests an attractive design strategy for tuning the A‐sites in perovskite oxides to realize high‐rate CO 2 ‐to‐CH 4 electrosynthesis with low overpotentials.