Authors
Di Shen, Fanfei Sun, Zhijian Liang, Honggang Fu, Lei Wang
Published in
Angewandte Chemie (International ed. in English). Pages e202505937. Jun 12, 2025. Epub Jun 12, 2025.
Abstract
Atomically dispersed Fe-based catalyst represents a promising alternative to platinum for oxygen reduction reaction (ORR). However, the prevalent FeN4 configuration exhibits limited intrinsic activity in acidic media owing to its inherent instability, thereby restricting the application in proton exchange membrane fuel cell (PEMFC). Herein, we introduce axial-N coordination to enhance the activity and stability of atomically dispersed Fe sites for acidic ORR by establishing a barrier to prevent Fe dissolution. Compared to FeN4 configuration, the axial-N ligand in the FeN5, FeN5-Fe3 and FeN2C3 configurations induces a square-pyramidal crystal field, which diminishes the spin polarization in the dz2, dxz, and dyz orbitals, and alters the electronic delocalization of Fe atom. In a 0.10 M HClO4 electrolyte, the ORR activity increases with enhanced electronic delocalization, following the trend: FeN5 > FeN5+Fe3 > FeN2C3 > FeN4. Operando technique further reveals that the dissociation of Fe-N bond in the FeN5 configuration occurs alongside the insertion of oxygen, leading to the formation of FeN3O2 and FeN4O1 structures that could accelerate the ORR kinetics. Consequently, the FeN5 configuration shows a positive shift of 30 mV in half-wave potential compared to Pt/C and achieves a peak power of 1.2 W cm-2 at 3.2 A cm-2 in PEMFC.
PMID:
40501393
Bibliographic data and abstract were imported from PubMed on 12 Jun 2025.
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