High-performance Co-N-C catalyst derived from PS@ZIF-8 @ZIF-67 for improved oxygen reduction reaction

A kind of Co-N-C catalysts with hollow core-shell structures with large amount of carbon nano tubes (CNTs) growing on the surface were prepared, using polystyrene (PS) spheres as sacrificial templates, ZIF-8 @ZIF-67 as Co-N-C source and PVP as binder, and their performances in oxygen reduction reaction (ORR) were further explored. The electrochemical test results show that the prepared electrocatalyst Co/NHCNT-160 has good catalytic activity for ORR process and a nearly four-electron reaction path. Co/NHCNT-160 has long-term stability at high onset potential (0.955 V), half-wave potential (0.88 V) and limiting current density (6.3 mA cm−2), with a current retention rate of 99.7 % after 7 h. The ORR performance of Co/NHCNT-160 has surpassed that of commercially available Pt/C catalyst and most of the non-precious metal catalysts reported to date. Its excellent ORR catalytic performance is mainly due to its unique hollow core-shell structure and the abundance of CNTs spawned, the high degree of graphitization facilitating electron migration, the graded pores facilitating mass migration, and the functionalization of the Co-Nx active site with a highly dispersed carbon backbone. This catalyst preparation strategy will provide some ideas for the development of other ZIF-based ORR catalysts for energy storage and electrochemical devices.