4.8 Article

Hierarchically Assembled Cobalt Oxynitride Nanorods and N-Doped Carbon Nanofibers for Efficient Bifunctional Oxygen Electrocatalysis with Exceptional Regenerative Efficiency

Journal

ACS NANO
Volume 15, Issue 7, Pages 11218-11230

Publisher

AMER CHEMICAL SOC
DOI: 10.1021/acsnano.0c09905

Keywords

cobalt oxynitrides; carbon nanofibers; bifunctional catalysts; oxygen reduction reaction; oxygen evolution reaction

Funding

  1. National Research Foundation of Korea (NRF) - Korean Government (MSIT) [2019R1F1A1044908]
  2. Korea Institute of Industrial Technology [kitech JA-20-0001]
  3. GyeongiDo Technology Development Program [kitech IZ20-0004]
  4. National Research Foundation of Korea (NRF) grant of the Korean Government [NRF-2019M3D1A2104101]
  5. KIST Institutional Program [2E31002]
  6. Hydrogen Energy Innovation Technology Development Program of the National Research Foundation of Korea (NRF) - Korean government (Ministry of Science and ICT(MSIT)) [2019M3E6A1063674]
  7. National Research Foundation of Korea [5199990414547, 2019R1F1A1044908] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)

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Optimized design of bifunctional oxygen electrocatalysts is crucial for achieving high-performance energy conversion systems. The novel CoOx@CoNy/NCNF hybrid catalyst exhibits excellent oxygen reduction and oxygen evolution reaction activity, catalyzing redox reactions effectively and enhancing the stability of Zn-air batteries.
Oxygen-based electrocatalysis is an integral aspect of a clean and sustainable energy conversion/storage system. The development of economic bifunctional electrocatalysts with high activity and durability during reversible reactions remains a great challenge. The tailored porous structure and separately presented active sites for oxygen reduction and oxygen evolution reactions (ORR and OER) without mutual interference are most crucial for achieving desired bifunctional catalysts. Here, we report a hybrid composed of sheath-core cobalt oxynitride (CoOx@CoNy) nanorods grown perpendicularly on N-doped carbon nanofiber (NCNF). The brushlike CoOx@CoNy nanorods, composed of metallic Co4N cores and oxidized surfaces, exhibit excellent OER activity (E = 1.69 V at 10 mA cm(-2)) in an alkaline medium. Although pristine NCNF or CoOx@CoNy alone had poor catalytic activity in the ORR, the hybrid showed dramatically enhanced ORR performance (E = 0.78 V at -3 mA cm(-2)). The experimental results coupled with a density functional theory (DFT) simulation confirmed that the broad surface area of the CoOx@CoNy nanorods with an oxidized skin layer boosts the catalytic OER, while the facile adsorption of ORR intermediates and a rapid interfacial charge transfer occur at the interface between the CoOx@CoNy nanorods and the electrically conductive NCNF. Furthermore, it was found that the independent catalytic active sites in the CoOx@CoNy/NCNF catalyst are continuously regenerated and sustained without mutual interference during the round-trip ORR/OER, affording stable operation of Zn-air batteries.

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