pH-dependent stability of Fe-N-C catalysts for fuel cells = pH-dependent stability of Fe-N-C catalysts for fuel cells

다국어 초록 (Multilingual Abstract)

For catalyzing dioxygen reduction, Fe-N-C materials are today the best candidates to replace platinum in fuel cell cathodes. Despite tremendous progress in their activity and site-structure understanding, improved durability is critically needed but challenged by insufficient understanding of their degradation mechanisms. Here, we show that FeNxCy moieties in Fe-N-C catalyst are structurally stable but electrochemically unstable when exposed to H₂O₂, the main oxygen reduction reaction (ORR) byproduct. Chemical deactivation of Fe-N-C catalyst is highly alleviated due to minimal production of reactive oxygen species in alkaline medium as confirmed by electron paramagnetic resonance study. Observed in acidic but not in alkaline electrolyte, these insights suggest that durable Fe-N-C catalysts are within reach for low-temperature fuel cells if either rational strategies minimizing the amount of H₂O₂ produced during ORR in acidic medium or high-performing alkaline membranes are developed.