Ternary Heteroatomic Doping Induced Microenvironment Engineering of Low Fe‐N4‐Loaded Carbon Nanofibers for Bifunctional Oxygen Electrocatalysis

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-01, Vol.20 (1), p.e2304844-n/a
• Main Authors: Li, Han, Zhao, Haoyue, Yan, Guilong, Huang, Gongyue, Ge, Can, Forsyth, Maria, Howlett, Patrick C., Wang, Xungai, Fang, Jian
• Format: Article
• Language: English
• Subjects: Carbon fibers; carbon nanofibers; Catalytic activity; Charge distribution; Doping; Electrocatalysts; Imidazole; Ionic liquids; Iron; iron single‐atom bifunctional electrocatalysts; Nanofibers; Optimization; Oxygen; polymerized ionic liquids; rechargeable Zn‐air batteries; ternary‐heteroatom doping
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202304844

Fabricating highly efficient and long‐life redox bifunctional electrocatalysts is vital for oxygen‐related renewable energy devices. To boost the bifunctional catalytic activity of Fe‐N‐C single‐atom catalysts, it is imperative to fine‐tune the coordination microenvironment of the Fe sites to optimize the adsorption/desorption energies of intermediates during oxygen reduction/evolution reactions (ORR/OER) and simultaneously avoid the aggregation of atomically dispersed metal sites. Herein, a strategy is developed for fabricating a free‐standing electrocatalyst with atomically dispersed Fe sites (≈0.89 wt.%) supported on N, F, and S ternary‐doped hollow carbon nanofibers (FeN4‐NFS‐CNF). Both experimental and theoretical findings suggest that the incorporation of ternary heteroatoms modifies the charge distribution of Fe active centers and enhances defect density, thereby optimizing the bifunctional catalytic activities. The efficient regulation isolated Fe centers come from the dual confinement of zeolitic imidazole framework‐8 (ZIF‐8) and polymerized ionic liquid (PIL), while the precise formation of distinct hierarchical three‐dimensional porous structure maximizes the exposure of low‐doping Fe active sites and enriched heteroatoms. FeN4‐NFS‐CNF achieves remarkable electrocatalytic activity with a high ORR half‐wave potential (0.90 V) and a low OER overpotential (270 mV) in alkaline electrolyte, revealing the benefit of optimizing the microenvironment of low‐doping iron single atoms in directing bifunctional catalytic activity. A strategy of combining PIL and Fe‐modified zeolitic imidazole framework‐8 (ZIF‐8) as co‐precursors is developed for fabricating Fe single‐atom bifunctional electrocatalysts. The efficient regulation of isolated Fe centers comes from the dual confinement of ZIF and PIL. The coordination microenvironment engineering of low‐doping Fe sites induced by ternary heteroatomic doping and hierarchical porous structures contributes to high‐efficient ORR/OER electrocatalysis.