Flexible, Porous, and Metal-Heteroatom-Doped Carbon Nanofibers as Efficient ORR Electrocatalysts for Zn-Air Battery.

Developing an efficient and durable oxygen reduction electrocatalyst is critical for clean-energy technology, such as fuel cells and metal-air batteries. In this study, we developed a facile strategy for the preparation of flexible, porous, and well-dispersed metal-heteroatom-doped carbon nanofibers by direct carbonization of electrospun Zn/Co-ZIFs/PAN nanofibers (Zn/Co-ZIFs/PAN). The obtained Zn/Co and N co-doped porous carbon nanofibers carbonized at 800 °C (Zn/Co-N@PCNFs-800) presented a good flexibility, a continuous porous structure, and a superior oxygen reduction reaction (ORR) catalytic activity to that of commercial 20 wt% Pt/C, in terms of its onset potential (0.98 V vs. RHE), half-wave potential (0.89 V vs. RHE), and limiting current density (- 5.26 mA cm-2). In addition, we tested the suitability and durability of Zn/Co-N@PCNFs-800 as the oxygen cathode for a rechargeable Zn-air battery. The prepared Zn-air batteries exhibited a higher power density (83.5 mW cm-2), a higher specific capacity (640.3 mAh g-1), an excellent reversibility, and a better cycling life than the commercial 20 wt% Pt/C + RuO2 catalysts. This design strategy of flexible porous non-precious metal-doped ORR electrocatalysts obtained from electrospun ZIFs/polymer nanofibers could be extended to fabricate other novel, stable, and easy-to-use multi-functional electrocatalysts for clean-energy technology.