Comparative development and evaluation of Fe–N–C electrocatalysts for the oxygen reduction reaction: The effect of pyrolysis and iron-bipyridine structures

Abstract

Proton exchange membrane fuel cells (PEMFCs) constitute a promising avenue for environmentally friendly power generation. However, the reliance on unsustainable platinum-based electrocatalysts used at the electrodes poses challenges to the commercial viability of PEMFCs. Non-platinum group metal (non-PGM) alternatives, like nitrogen-coordinated transition metals in atomic dispersion (M–N–C catalysts), show significant potential. This work presents a comparative study of two distinct sets of Fe–N–C materials, prepared by pyrolyzing hybrid composites of polyaniline (PANI) and iron (II) chloride on a hard template. One set uses bipyridine (BPy) as an additional nitrogen source and iron ligand, offering an innovative approach. The findings reveal that the choice of pyrolysis temperature and atmosphere influences the catalyst properties. The use of ammonia in pyrolysis emerges as a crucial parameter for promoting atomic dispersion of iron, as well as increasing surface area and porosity. The optimal catalyst, prepared using BPy and ammonia, exhibits a half-wave potential of 0.834 V in 0.5 M H₂SO₄ (catalyst loading of 0.6 mg cm⁻²), a mass activity exceeding 3 A g⁻¹ and high stability in acidic electrolyte, positioning it as a promising non-PGM structure in the field.