Bead-like cobalt-nitrogen co-doped carbon nanocage/carbon nanofiber composite: a high-performance oxygen reduction electrocatalyst for zinc-air batteries

Proper regulation of metal-nitrogen carbon (M-N-C) materials derived from zeolitic imidazolate frameworks (ZIFs) is essential to enhance the oxygen reduction reaction (ORR) performance. However, most of the reports focus on the component regulation, and the structure regulation of ZIFs-derived M-N-C materials by a simple preparation method has been barely reported. Herein, using a one-step electrospinning method with subsequent pyrolysis, we have prepared a bead-like cobalt-nitrogen co-doped carbon nanocage/carbon nanofiber (Co-N-C/CNF) composite electrocatalyst with the porous carbon nanocages arranged one by one in the highly conductive carbon nanofibers. Profiting from the fully exposed active sites and improved conductivity, the Co-N-C/CNF catalyst exhibits an excellent ORR performance even surpassing the commercial Pt/C catalyst. Density functional theory (DFT) results demonstrate that the CoNP-N1-C2 active sites on Co-N-C/CNF make the core contribution to the improvement of ORR properties. Moreover, the zinc-air battery (ZAB) based on the Co-N-C/CNF catalyst also shows outstanding discharge performance. This study provides a new strategy for the preparation and structural design for ZIFs-derived M-N-C materials as efficient ORR catalysts.