Improving the Electrocatalytic Activity of a High‐Entropy Ruddlesden–Popper Perovskite Air Electrode for Solid Oxide Cells Through Composition Regulation

One major challenge to the application of solid oxide cell technology is the poor catalytic activity and stability of air electrodes. High‐entropy engineering has been considered as a promising strategy to improve the activity and durability of perovskite‐derived air electrodes. However, the understanding of the individual contributions of configurational entropy and specific elemental composition to the performance improvement is still insufficient. Herein, the effects of A‐site elements and configurational entropy on the performance of Ruddlesden–Popper‐structured (La/Sr/Pr/Ba/Ca) 2 Ni 0.5 Fe 0.5 O 4±δ electrodes are investigated. The results demonstrate that the electrocatalytic activity of the electrode is highly related to the reactivity of lattice oxygen. The polarization resistance of the electrode is negatively correlated with the content of Sr and the configurational entropy, and a Sr‐rich Sr 0.8 La 0.3 Pr 0.3 Ba 0.3 Ca 0.3 Ni 0.5 Fe 0.5 O 4±δ electrode with a sub‐high entropy exhibits the lowest polarization resistance of 0.044 Ω cm 2 at 700°C. A protonic ceramic cell with that air electrode achieves a peak power density of 2.15 W cm −2 in the fuel cell mode and a current density of 2.88 A cm −2 for H 2 O electrolysis under 1.3 V at 700°C. Meanwhile, the air electrode exhibits high stability in CO 2 and H 2 O atmospheres.