ZIF-67 was used as a template for producing metal and nitrogen doped carbon composite as electrocatalysts. By an in-situ polymerization of dopamine on the surface of ZIF-67

Co2+ ions were extracted into the polydopamine shell due to the strong chelation between them and led to the decomposition of ZIF-67

which resulted into a hollow composite of Co-PDA. Subsequently

a yolk-shell structure of metal and nitrogen doped carbon composites (Co@Co-N/C) was obtained by a high temperature pyrolysis at 900℃. The unique structure of Co@Co-N/C provided excellent bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)

repetitively. For ORR

the half-wave potential was 0.81 V and the Tafel slope was 60 mV/dec. For OER

the overpotential was 390 mV at the current density of 10 mA/cm2

and the Tafel slope was 71 mV/dec. More importantly

the total oxygen electrocatalytic activity was as low as 0.82 V.