Magnetic purification of non-precious metal fuel cell catalysts for obtaining atomically dispersed Fe centers

The development of non-precious metal oxygen reduction catalysts is vital for enabling the commercialization of proton exchange membrane fuel cells, and Fe/N/C catalysts prepared by the pyrolysis of Fe, N, and C-containing precursors have been widely studied for this purpose. The role of atomically dispersed Fe centers in the reaction mechanisms of Fe/N/C catalysts has been widely studied. This paper demonstrates a facile magnetic purification approach for obtaining atomically dispersed Fe centers for conducting superior Fe/N/C catalysis. Upon treatment of a Fe/N/C catalyst prepared by pyrolyzing Fe-containing polyimide nanoparticles with a magnet, the clustered Fe species (metallic Fe and Fe 3 C) observed before the purification were successfully eliminated, and atomically dispersed Fe species were clearly observed by microscopy. Comparison of the oxygen reduction activities of the Fe/N/C catalysts before and after the magnetic purification in half-cell and fuel cell testing revealed the retention of the high catalytic performances of the Fe/N/C catalysts. Furthermore, no loss in catalytic performance or durability was observed after the magnetic purification. This paper proposes a facile magnetic purification approach for obtaining atomically dispersed Fe centers in non-precious metal fuel cell catalysts, which has been evidenced by X-ray absorption spectroscopy and microscopy.