Atomic Fe-N<sub>4</sub> /C in Flexible Carbon Fiber Membrane as Binder-Free Air Cathode for Zn-Air Batteries with Stable Cycling over 1000 h.
basic_science · Level V
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- Record sourced from PubMed, PMID 34787336.
- Also identified by DOI 10.1002/adma.202105410.
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Abstract
Noble-metal-free, durable, and high-efficiency electrocatalysts for oxygen reduction and evolution reaction (ORR/OER) are vital for rechargeable Zn-air batteries (ZABs). Herein, a flexible and free-standing carbon fiber membrane immobilized with atomically dispersed Fe-N<sub>4</sub> /C catalysts (Fe/SNCFs-NH<sub>3</sub> ) is synthesized and used as air cathode for ZABs. The intertwined fibers with hierarchical nanopores facilitate the gas transportation, electrolyte infiltration and electron transfer. The large specific surface area exposes a high concentration of Fe-N<sub>4</sub> /C sites embedded in the carbon matrix. Modulation of local atomic configurations by sulfur doping in Fe/SNCFs-NH<sub>3</sub> catalyst leads to excellent ORR and enhanced OER activities. The as-synthesized Fe/SNCFs-NH<sub>3</sub> catalyst demonstrates a positive half-wave potential of 0.89 V and a small Tafel slope of 70.82 mV dec<sup>-1</sup> , outperforming the commercial Pt/C (0.86 V/94.74 mV dec<sup>-1</sup> ) and most reported M-N<sub>x</sub> /C (M = Fe, Co, Ni) catalysts. Experimental characterizations and theoretical calculations uncover the crucial role of S doping in regulating ORR and OER activities. The liquid-state ZABs with Fe/SNCFs-NH<sub>3</sub> catalyst as air cathode deliver a large peak power density of 255.84 mW cm<sup>-2</sup> and long-term cycle durability over 1000 h. Solid-state ZAB shows stable cycling at various flat/bent/flat states, demonstrating great prospects in flexible electronic device applications.