Synergistic Optimization of Power Output and Thermomechanical Stability Enabled by Rational Cathode Design in Protonic Ceramic Fuel Cells

Abstract Most protonic ceramic fuel cell (PCFC) cathodes rely on Co‐rich materials to achieve high electrochemical performance; however, their thermomechanical incompatibility with proton‐conducting electrolytes is the primary obstacle for the practical realization of PCFC systems. Despite significant progress over the past few years, simultaneously achieving thermomechanical stability and excellent electrochemical performance remains an unresolved challenge. Herein, a rationally designed composite cathode is presented that synergistically combines a robust Sr‐doped LaMnO 3 (LSM) backbone with infiltrated electrocatalytically active PrBa 0.5 Sr 0.5 Co 1.5 Fe 0.5 O 5+δ (PBSCF) nanoparticles (NPs). The optimized cathode delivers an outstanding peak power density of 0.80 W cm −2 at 500 °C, while also maintaining stable performance over 100 cycles between 550 and 400 °C in power generation mode at 0.5 V. This high electrochemical performance is attributed to the newly established routes for H + /O 2− transport through well‐interconnected PBSCF NPs. To elucidate the high level of thermomechanical stability, a computational thermal stress analysis is conducted, validating that the LSM backbone effectively offsets thermal expansion mismatch between the electrode and electrolyte. Additionally, this study provides practical design guidelines for optimizing material combinations and microstructural engineering to ensure reliable operation in PCFC systems.