Hierarchically assembled cobalt oxynitride and N-doped carbon nanofiber hybrids for efficient bifunctional oxygen electrocatalysis with exceptional regenerative efficiency
- Hierarchically assembled cobalt oxynitride and N-doped carbon nanofiber hybrids for efficient bifunctional oxygen electrocatalysis with exceptional regenerative efficiency
- 채근화; 김형준; 김진영; 박현서; 김종민; 임아연; 이경아; 김승훈; 채지언; 김준; 황창규; 윤기로; 정지원; 조수호; Jitendra Pal Singh; 신기현; 문병무; 함형철; 김일두
- Issue Date
- ACS Nano
- VOL 15-11230
- 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 brush-like 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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