Monomer-coordination synthesis of Fe-Nx nanofiber catalysts for the oxygen reduction reaction

Developing low-cost, high-performance non-precious-metal catalysts for the oxygen reduction reaction (ORR) is crucial for clean-energy technologies. Herein, we propose a “monomer-coordination/in-situ polymerization” strategy in which inexpensive acrylonitrile monomers are pre-coordinated with Fe 3+ before radical polymerization, yielding uniformly Fe-doped polyacrylonitrile (PAN) (denoted Fe + PAN). Subsequent electrospinning and pyrolysis of this precursor afford Fe-N x nanofiber catalysts (denoted O-Fe-N-C). Compared with the conventional “polymerize-then-dope-Fe” route (denoted T-Fe-N-C), this approach markedly reduces the steric hindrance of PAN chains, strengthens Fe-N interactions, increases the density of Fe-N x active sites after pyrolysis, and suppresses Fe agglomeration. In 0.1 M KOH, O-Fe-N-C delivers an ORR half-wave potential of 0.878 V (vs RHE), outperforming commercial Pt/C. When employed as the air cathode in a Zn-air battery, the O-Fe-N-C cell exhibits an open-circuit voltage of 1.46 V and a peak power density of 133.91 mW cm −2 at 205.7 mA cm −2 , surpassing the Pt/C benchmark. This work provides a molecular-level design paradigm for scalable synthesis of low-cost, high-performance Fe-N x ORR catalysts.