Résumé
Iron-based catalysts are intensely investigated for application at the cathode of proton exchange membrane (PEM) and, more recently, of anion exchange membrane fuel cells (AEMFC). Besides optimising their kinetic activity toward the oxygen reduction reaction (ORR), the design and control of their pore structure plays a key role in achieving the highest possible performance in fuel cell. Fe-N-C catalysts derived from the metal-organic framework ZIF-8 are highly active but also mainly microporous, which can lead to mass-transport issues. The silica templating approach typically leads to slightly less active Fe-N-C catalysts, but featuring a combination of micropores and mesopores, which can facilitate mass-transport. Aerogel methods for the synthesis of Fe-N-C catalysts with a hierarchical pore size distribution has been hitherto under-investigated. In contrast to the silica templating method, it is more environmental friendly since no dissolution of a template is needed (no HF). However, highly active Fe-N-C catalysts prepared by aerogel method have not yet been reported in PEM system (even if promising results were recently obtained in rotating disk electrode [1-2]), and it is therefore also unclear if the hierarchical pore size distribution derived from this method is beneficial for improving the mass-transport properties of Fe-N-C cathodes.