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

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_0.2Pr_0.2Ba_0.2Sr_0.2Ca_0.2FeO_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 Fe⁴⁺ 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 Fe⁴⁺ 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 cm² 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.