Iron-based Catalysts for Oxygen Reduction in PEM Fuel Cells: Expanded Study Using the Pore-filling Method

Fe/N/C catalysts for the oxygen reduction reaction (ORR) in PEM fuel cells were synthesized via a new method. A catalyst precursor was first prepared by filling the pores of a microporous carbon black with a mixture of pore-filler (organic molecules) and iron precursor by means of planetary ballmilling. The resulting catalyst precursor was then pyrolysed either in NH3 only or, first in Ar and then in NH3. Various pore-fillers and carbon blacks were investigated. The ORR activity in fuel cell is influenced by (i) the type and mass ratio of the pore-filler and the nominal loading of iron in the catalyst precursor and (ii) the micropore surface area and nitrogen content in the catalyst. The highest kinetic activity obtained in fuel cell at 0.8 V iR-free is 429 A g(-1) using 1 wt% nominal iron loading, phenanthroline as the pore-filler and Black Pearls 2000 as the microporous carbon black.