Catastrophic Degradation in Solid Oxide Fuel Cells Caused by Air Supply Interruption in Real‐World Operations: Fundamental Mechanisms and Mitigation Strategies

Abstract With the rapid market expansion of solid oxide fuel cells (SOFCs), real‐world operational incidents have unveiled various critical challenges. Malfunction of the gas supply system is among the most frequent and critical issues, severely damaging cells and stacks. However, the actual cause of this degradation remains completely unknown; existing explanations have been mostly speculative, and simple engineering‐based solutions have proven ineffective. The study reveals that air supply interruption induces irreversible chemical degradation of perovskite‐based electrode materials. Upon air stoppage, the continued electric current rapidly depletes oxygen, decreasing the oxygen partial pressure below the stability threshold of the state‐of‐the‐art (La,Sr)CoO _3–δ cathode. This triggers structural breakdown of the perovskite phase and initiates a cascade of harmful reactions with adjacent components and externally introduced impurities. Among the constituent elements, Sr is identified as a key driver of degradation, suggesting its elimination as a mitigation strategy. Then, by systematically tailoring the catalytic and electrical properties,a high‐performance Sr‐free cathode incorporating highly active nanocatalysts is developed. It outperformed the most advanced benchmark cathode, and more importantly, it demonstrated excellent durability upon severe air supply interruption with extreme oxygen depletion, offering a practically viable solution to a critical reliability challenge in commercial SOFC systems.