Résumé
Proton exchange membrane fuel cell (PEMFC) has been widely developed throughout the last decades for wide application of hydrogen, especially for portable or transportation applications. Platinum is currently used to accelerate the electrochemical kinetics. However, this expensive and precious metal catalysts for oxygen reduction reaction (ORR) constrains the commercialization of PEMFCs. To reduce the total costof these devices, non-precious-metal catalysts (NPMCs) have been investigated to replace platinum-based catalysts. Among them, iron-nitrogen-carbon (Fe-N-C) catalysts subclass is the most mature. Numerous studies have focused on promoting their catalytic performance and exploring their mechanism. Despite being less performant than Pt/C, the activity difference can be offset by ca. 3-10 times thicker cathodes. Nevertheless, in such configuration, mass transfer limitations become predominant and need to be optimized.Carbon aerogels are an ideal candidate to synthesize Fe-N-C catalysts with excellent mass transfer properties due to their tridimensional open texture, tailored pore size distribution and good electrical conductivity. Herein, we synthesized Fe-N-C aerogel catalysts from resorcinol (R)-formaldehyde (F)-melamine (M) hydrogel and iron precursors using “one pot” sol-gel method following with CO2 supercritical drying and post heat treatments (N2 and NH3 atmospheres). The catalysts exhibit high specific surface areas (more than 1000 m²/g) and large pore volumes. The micropores are mainlygenerated from ammonia treatment where the active sites are located. The mesopores are formed during the gelation of RMF gel which decide the mass transfer property of the catalysts. We demonstrate that chemical parameters of the hydrogels, especially melamine content, can greatly change the morphology of Fe-N-C aerogels and affect their mass transport properties. Nitrogen sorption and X-ray photoelectron spectroscopy reveal that melamine content controls the mesoporous structure during the pyrolysis and theactivity which is linked to the nitrogen content in the catalysts. Besides, the iron precursor impacts the polymerization, which lead to different morphology. The catalysts are characterized ex situ by XANES and EXAFS, their electrochemical activities are investigated both in rotating disk electrode (RDE) and in PEMFC and relationships are established between synthesis parameters and electrochemical performance.