Structure-property relationship of cryogel based Fe-N-C Catalysts for the oxygen reduction reaction
Résumé
As part of the cost reduction of Proton Exchange Membrane Fuel Cells, the substitution of standard platinum catalyst by iron active sites for the oxygen reduction reaction (ORR) appears as a promising route. We report herein Pt-free catalysts prepared through a Fe-N-doped carbon cryogel synthesis. By tuning selected parameters such as the initial pH and the precursor molar ratios, various new structures with different chemical compositions and catalytic activities were synthesized and characterized. Carbon cryogels are porous materials, and the achieved hierarchical structures proved favorable for the accessibility of the active sites for O$_2$ and H$^+$. The value of the pH medium was identified as a key parameter to control the structure of the N-rich carbon cryogels, leading in a specific pH range to diphasic hydrogels. These materials are described and characterized for the first time, they show promising catalytic activity for the ORR.