Cobalt Nanoparticles Embedded into Nitrogen-doped Graphene with Abundant Macropores as a Bifunctional Electrocatalyst for Rechargeable Zinc-air Batteries.

Nitrogen doped carbon materials containing transition metal nanoparticles have attracted much attention as bifunctional oxygen electrocatalysts. In this paper, the template etching method is used to obtain the nitrogen-doped graphene with abundant macropores embedded with cobalt nanoparticles (Co@N-C). The prepared Co@NC-800 catalyst has a half-wave potential (E 1/2= 0.835 V) close to Pt/C and good stability in excess of Pt/C for oxygen reduction reaction (ORR). At the same time, the catalyst has good oxygen evolution reaction (OER) performance. In addition, zinc-air batteries (ZABs) based on the Co@NC-800 catalyst show good cycle stability of up to 200000 s and high power density of 73.5 mW cm -2 . The synergistic effect of the integrated component between nitrogen-doped graphene and cobalt nanoparticles as well as the macroporous structure endow Co@NC-800 with abundant exposed active sites and mass/electron transfer capacity, thus leading to the high electrocatalytic activity. This work shows potential for practical applications in electrochemistry.