Hierarchically porous carbons as supports for fuel cell electrocatalysts with atomically dispersed Fe–Nx moieties

Abstract

The development of high-performance non-platinum group metal (non-PGM) catalysts for the oxygen reduction reaction (ORR) is still of significance in promoting the commercialization of proton exchange membrane fuel cells (PEMFCs). In this work, a “hierarchically porous carbon (HPC)-supporting” approach was developed to synthesize highly ORR active Fe–phenanthroline (Fe–phen) derived Fe–N_x–C catalysts. Compared to commercial carbon black supports, utilizing HPCs as carbon supports can not only prevent the formation of inactive iron nanoparticles during pyrolysis but also optimize the porous morphology of the catalysts, which eventually increases the amount of reactant-accessible and atomically dispersed Fe–N_x active sites. The prepared catalyst therefore exhibits a remarkable ORR activity in both half-cells (half-wave potential of 0.80 V in 0.5 M H₂SO₄) and H₂–air PEMFCs (442 mA cm⁻² at a working voltage of 0.6 V), making it among the best non-PGM catalysts for PEMFCs.