Mitigating the decomposition phenomenon at the cathode–electrolyte interface of protonic ceramic fuel cells

Abstract Protonic ceramic fuel cells (PCFCs) are promising for efficient, clean energy conversion at low to intermediate temperatures, but the widely used BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3− δ (BZCYYb) electrolyte has poor chemical stability in humid environments. Herein, we show that under oxygen reduction reaction (ORR) conditions, water accumulates at the BaGd 0.8 La 0.2 Co 2 O 6− δ (BGLC) cathode–BZCYYb electrolyte interface, causing selective loss of Ba cations and decomposition of BZCYYb electrolyte. The introduction of triply ion–electron conducting La 2 Ce 2 O 7− δ (LCeO) into the BGLC cathode expands its active reaction area, accelerates ORR kinetics, and suppresses water accumulation at the cathode–electrolyte interface and electrolyte decomposition. A single cell with the BGLC‐LCeO composite cathode achieves a peak power density of 1.07 W cm −2 at 700 °C, with no profound degradation at 0.5 A cm −2 over 100 h. These findings provide guidance for the development of high‐performance, durable PCFCs.