Unraveling the Synergistic Activity‐Stability Enhancement of a High‐Entropy Perovskite Air Electrode for Dual Ceramic Electrochemical Cells

ABSTRACT Regulating the activity and stability of high‐entropy perovskite air electrodes is essential for their application in ceramic electrochemical cells, yet the underlying mechanisms remain unclear. In this work, a novel high‐entropy perovskite, Gd _0.2 Pr _0.2 Ba _0.2 Sr _0.2 Ca _0.2 FeO _3−δ (GPBSCF), is developed as a highly active and stable air electrode for both oxygen‐ion conducting solid oxide fuel cells (O‐SOFCs) and reversible protonic ceramic cells (R‐PCCs). It is demonstrated that high‐entropy doping increases Fe ⁴⁺ content and structural symmetry, thereby elevating oxygen vacancy/hole concentration and enhancing catalytic activity. Concurrently, the induced lattice distortion improves structural stability and inhibits Ba/Sr surface segregation. Furthermore, the increased Fe ⁴⁺ content, combined with the pinning effect induced by lattice distortion, synergistically reduces the thermal expansion coefficient. In O‐SOFCs, a symmetric cell with GPBSCF exhibits a low polarization resistance of 0.08 Ω cm ² at 650°C and operates stably for 1000 h. In R‐PCCs, a single cell demonstrates excellent durability over 680 h. This work provides fundamental insights into high‐entropy optimization mechanisms, guiding the rational design of advanced Fe‐based perovskite air electrodes for durable ceramic electrochemical cells.