Fe-N-C Catalysts for Proton Exchange Membrane Fuel Cells: Advances from Synthesis to Practical Applications

Abstract

Proton exchange membrane fuel cells (PEMFCs) represent a cornerstone technology for sustainable energy conversion, yet their widespread deployment remains constrained by reliance on platinum-group-metal (PGM) catalysts. This comprehensive review critically examines the development of iron-nitrogen-carbon (Fe–N–C) catalysts as a viable PGM-free alternative, addressing key challenges from atomic-scale active site engineering to full-cell integration. We present a systematic analysis of synthetic methodologies including pyrolysis, sacrificial templating, and MOF-derived approaches that enable precise control over Fe–N₄ moiety density and accessibility. Advanced characterization techniques, such as operando X-ray absorption spectroscopy and electron microscopy, reveal fundamental structure–activity–stability relationships governing oxygen reduction reaction (ORR) kinetics in acidic media. While the catalytic activity of the state-of-the-art Fe–N–C catalysts approaches promising half-wave potentials (E₁/₂ > 0.9 V vs. RHE) under specific conditions, these values can significantly vary with synthetic, testing procedures and electrode configuration. Their translation to practical membrane electrode assemblies (MEAs) necessitates innovative solutions to address durability limitations (<500 h operational stability) and mass transport constraints in thick catalyst layers (>50 μm). We further discuss emerging strategies in electrode architecture design, ionomer–catalyst interactions, and accelerated stress testing protocols. By bridging fundamental insights with engineering considerations, this review provides a roadmap for advancing Fe–N–C catalysts toward commercial viability in next-generation PEMFC systems.