Cation‐Deficiency‐Dependent CO 2 Electroreduction over Copper‐Based Ruddlesden–Popper Perovskite Oxides

We report an effective strategy to enhance CO 2 electroreduction (CER) properties of Cu‐based Ruddlesden–Popper (RP) perovskite oxides by engineering their A‐site cation deficiencies. With La 2− x CuO 4‐δ (L 2− x C, x =0, 0.1, 0.2, and 0.3) as proof‐of‐concept catalysts, we demonstrate that their CER activity and selectivity (to C 2+ or CH 4 ) show either a volcano‐type or an inverted volcano‐type dependence on the x values, with the extreme point at x =0.1. Among them, at −1.4 V, the L 1.9 C delivers the optimal activity (51.3 mA cm −2 ) and selectivity (41.5 %) for C 2+ , comparable to or better than those of most reported Cu‐based oxides, while the L 1.7 C exhibits the best activity (25.1 mA cm −2 ) and selectivity (22.1 %) for CH 4 . Such optimized CER properties could be ascribed to the favorable merits brought by the cation‐deficiency‐induced oxygen vacancies and/or CuO/RP hybrids, including the facilitated adsorption/activation of key reaction species and thus the manipulated reaction pathways.