The Excellence of Both Worlds: Developing Effective Double Perovskite Oxide Catalyst of Oxygen Reduction Reaction for Room and Elevated Temperature Applications

The efficiencies of a number of electrochemical devices (e.g., fuel cells and metal‐air batteries) are mainly governed by the kinetics of the oxygen reduction reaction (ORR). Among all the good ORR catalysts, the partially substituted double perovskite oxide (AA′B 2 O 5+δ ) has the unique layered structure, providing a great flexibility regarding the optimization of its electronic structures and physicochemical properties. Here, it is demonstrated that the double perovskite oxide, i.e., NdBa 0.75 Ca 0.25 Co 1.5 Fe 0.5 O 5+δ , is a good ORR catalyst at both room and elevated temperatures. Under ambient condition, its half‐wave potential of ORR in alkaline media is as low as 0.74 V versus RHE; at 650 °C, the cathodic polarization resistance is merely 0.0276 Ω cm 2 according to a symmetric cell measurement, whereas the solid oxide fuel cells using this cathode exhibit a maximum power density of 1982 mW cm −2 . From various materials characterizations, it is hypothesized that its excellent ORR activity is strongly correlated with the crystallographic, electronic, and defect structures of the materials.