Hierarchically Porous Co and N-Codoped Carbon Hollow Structure Derived from PS@ZIF-67 as an Electrocatalyst for Oxygen Reduction

The development of low-cost, highly efficient, and durable electrocatalysts for oxygen reduction reaction (ORR) is vital to commercialization of a new generation of rechargeable metal-air batteries and fuel cells. Here we report a facile, efficient, template-assisted strategy for fabrication of hierarchically porous Co, N-codoped carbon hollow structures as ORR eletrocatalysts. The unique architecture of the catalyst was constructed through in situ growth of Co-based zeolitic imidazolate framework (ZIF-67) on the surface of carboxylated polystyrene (PS) nanosphere and pyrolysis for removal of PS and carbonization of ZIF-67. The resulting catalyst exhibited outstanding ORR activity in both alkaline and acidic electrolyte solution, comparable to that of a commercial Pt/C catalyst, and better than those reported for most Co, N-codoped carbon catalysts. Such superior performance is attributed to the unique features of the catalyst: large specific surface area, openly exposed active sites, high content of the pyridinic-N and graphitic-N active sites, and fast transfer of electrons and ions. Moreover, the catalyst also displayed much better tolerance to methanol and durability than the commercial Pt/C catalyst, ascribed to strong coupling of active sites and highly graphitic carbon sheets. Further, the simple, effective and low-cost synthesis strategy for creation of hierarchically porous electrodes is applicable to fabrication of other energy storage and conversion devices as well.