Highly dispersed ZIF-67-derived co-NC confined in carbon pores enables efficient oxygen reduction in alkaline media

It is crucial to develop low-cost and efficient electrocatalysts to facilitate oxygen reduction reaction (ORR) and transition metals incorporated into nitrogen-doped carbon matrices (M-NC) catalysts are regarded as a potential candidate to substitute platinum-based electrocatalyst. However, there is still a great challenge in real activity and stability, compared to Pt-based electrocatalysts, for large-scale applications. An effective way to improve the ORR performance for this category of single-atom catalysts is to increase the density of active sites. In this work, therefore, the highly dispersed ZIF-67-derived Co-NC confined in carbon pores electrocatalysts are synthesized by impregnating ZIF-67 precursors into the nanopores of Ketjenblack EC-600JD (KB) resulting in the in-situ growing of small crystals in the pores followed by the high temperature pyrolysis. The as-prepared CoNC-700@C electrocatalyst exhibits excellent ORR performance in alkaline media with an onset potential of 967 mV and a half-wave potential of 892 mV (vs. RHE), which is much higher than that of the commercial Pt/C catalyst. It is inferred that the excellent ORR activity of CoNC-700@C mainly results from the increased density and also enhanced dispersion of active sites due to the confinement effect offered by the pores of KB. This study also provides a simple and effective method to increase the density of active sites for single-atom category materials.