Highly efficient and sustainable non-precious-metal Fe–N–C electrocatalysts for the oxygen reduction reaction

Abstract

Exploring non-precious-metal catalysts (NPMCs) for highly-efficient oxygen reduction reactions (ORRs) in fuel cells holds great potential to ease the global energy challenge. Recent developments regarding state-of-the-art Fe–N–C catalysts in terms of precursor development, synthesis innovation, and active site identification are compelling. Here, an efficient and sustainable Fe–N–C catalyst was successfully synthesized by temperature-programmed N₂-pyrolysis from a ferrous ethylenediaminetetraacetic acid (EDTA) chelate. The unique structural properties were characterized by a wide existence of FeN₄/C species encapsulated by a N–C coat, multiple porous morphologies, and a defective graphitic matrix, all of which greatly enhanced their intrinsic conductivities and prevented the aggregation of active moieties. The best Fe–N–C–800 catalysts promoted the ORR peak potential to −0.21 V with a nearly four-electron transfer pathway, only facilitating ∼14% H₂O₂ production. Both the Mössbauer fingerprints and X-ray absorption near edge structure (XANES) analysis revealed the origin of the ORR features derived from the structural compositions and corresponding hyperfine interaction. Interestingly, the embedding of oxygen in the Fe–N–C structure was found favorable for boosting durability and methanol endurance, which also hints at a strategy for rationally designing and producing promising ORR electrocatalysts from proper approaches and precursors.