Fe₃C Nanoclusters Regulated Charge Asymmetric Fe Dual Atomic Sites for Enhanced Oxygen Reduction Performance

Abstract

Dual-atom catalysts (DACs) show attractive prospects for the oxygen reduction reaction (ORR), yet face challenges in precise charge modulation that balances the activity and durability. Herein, we present a N,S-coordinated Fe dual atomic catalyst modified by Fe₃C nanoclusters (Fe₃C/Fe₂N_xS) through pyrolyzing the mixtures of ZIF-8-encapsulated iron dimers and sulfur-doped C₃N₄. Aberration-corrected STEM and synchrotron X-ray absorption spectroscopy (XAS) validated that the catalyst was composed of Fe dual atomic sites and Fe₃C nanoclusters, in which Fe dual atoms were coordinated by five N atoms and one S atom. Fe₃C/Fe₂N_xS exhibited excellent ORR activity in alkaline media, displaying a high half-wave potential (E_1/2 = 0.894 V vs. RHE) with near 4e^– selectivity (n = 3.92) and maintaining 86.8% retention after 20000 s, superior to commercial Pt/C. Impressively, the assembled zinc-air battery delivered exceptional peak power density (163 mW·cm^–2) and 200-hour robust stability. Density functional theory (DFT) calculations revealed that electron transfer from Fe of Fe₂N_xS to neighboring Fe₃C induced local charge asymmetry, shifting the d-band center closer to Fermi level, thereby enhancing O₂ activation. Moreover, the OOH* formation energy barrier was reduced to 0.52 eV in Fe₃C/Fe₂N_xS, accelerating ORR reaction kinetics. This work establishes nanocluster-mediated electronic redistribution to tailor charge asymmetry for high-performance electrocatalysts.

Keywords

Dual-atom catalysts / N / S doping / Nanoclusters / Charge asymmetry / Oxygen reduction reaction

RIGHTS & PERMISSIONS

2025 SIOC, CAS, Shanghai, & WILEY-VCH GmbH