Cation‐Deficiency‐Dependent CO2 Electroreduction over Copper‐Based Ruddlesden–Popper Perovskite Oxides

We report an effective strategy to enhance CO2 electroreduction (CER) properties of Cu‐based Ruddlesden–Popper (RP) perovskite oxides by engineering their A‐site cation deficiencies. With La2−xCuO4‐δ (L2−xC, x=0, 0.1, 0.2, and 0.3) as proof‐of‐concept catalysts, we demonstrate that their CER activity and selectivity (to C2+ or CH4) 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 L1.9C delivers the optimal activity (51.3 mA cm−2) and selectivity (41.5 %) for C2+, comparable to or better than those of most reported Cu‐based oxides, while the L1.7C exhibits the best activity (25.1 mA cm−2) and selectivity (22.1 %) for CH4. 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. Engineering A‐site cation deficiency of Cu‐based Ruddlesden–Popper perovskite oxides is an effective strategy to enhance their CO2 electroreduction properties. With La2−xCuO4−δ (x=0, 0.1, 0.2, and 0.3) series as proof‐of‐concept catalysts, it was demonstrated that their Faradaic efficiency ratios of C2+/CH4 featured a volcano‐type dependence on the x values, with a maximum point at x=0.1.