An efficient Co-N-C oxygen reduction catalyst with highly dispersed Co sites derived from a ZnCo bimetallic zeolitic imidazolate framework

In this work we report a highly efficient Co based catalyst for the oxygen reduction reaction (ORR) with highly dispersed Co sites on N-doped carbon. The catalyst is derived from a ZnCo bimetallic metal organic framework (MOF) by heat treatment in an inert atmosphere at 1000 degrees C. Zn is simultaneously eliminated during the pyrolysis due to its high volatility at high temperature, yielding a highly porous structure with homogeneous Co loading. Another effect of Zn is to disperse Co in the MOF precursor, which effectively inhibits the aggregation of Co after pyrolysis. The best ORR performance is achieved when 5% Zn is substituted by Co in the MOF precursor. The resulting catalyst shows a high half wave potential of 0.90 V vs. reversible hydrogen electrode in 0.1 M KOH solution, which is mainly attributed to the high dispersion of the ORR active Co sites.