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.
Highlights
The high cost of Pt-based oxygen reduction reaction (ORR) catalysts has seriously hindered the commercialization of proton exchange membrane fuel cells (PEMFCs)
The synthetic steps of the as-prepared catalysts include the preparation of hierarchically porous carbon (HPC) supports, wet impregnation of the Fe–phen complex into HPCs, and pyrolysis treatment of the composite at 800 C in a nitrogen atmosphere (Fig. 1a)
N2 sorption isotherms revealed that the HPC support has a plot with a type IV pattern (Fig. S1†), including a rapid increase in the low-pressure region, a remarkable hysteresis loop, and a steep increase near P/P0 1⁄4 1, indicating the presence of micro, meso, and macro-pores, respectively.[20]
Summary
The high cost of Pt-based ORR catalysts has seriously hindered the commercialization of PEMFCs. A “hierarchically porous carbon (HPC)-supporting” approach was developed to synthesize highly ORR active Fe–phenanthroline (Fe–phen) derived Fe–Nx–C catalysts. Compared to commercial carbon black supports, utilizing HPCs as carbon supports can prevent the formation of inactive iron nanoparticles during pyrolysis and optimize the porous morphology of the catalysts, which eventually increases the amount of reactant-accessible and atomically dispersed Fe–Nx active sites.
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