In Situ Confinement Pyrolysis Transformation of ZIF-8 to Nitrogen-Enriched Meso-Microporous Carbon Frameworks for Oxygen Reduction

Metal organic framework (MOF)-derived nitrogen-enriched nanocarbons have been proposed as promising metal-free electrocatalysts for oxygen reduction reaction. However, the characteristic microporous feature of MOF-derived carbon determined by the MOF structure significantly hinders the mass transfer and exposure of active sites, resulting in unsatisfactory electrocatalytic performance. Here an in situ confinement pyrolysis strategy that can simply but efficiently transform monodisperse ZIF-8 polyhedrons to nitrogen-enriched meso-microporous carbon (NEMC) frameworks is reported. Using this strategy, 3D NEMC frameworks, 1D NEMC fibers, and 2D NEMC on graphene (NEMC/G) can be successfully obtained. As a metal-free elctrocatalyst, optimized NEMC/G can reach a comparable electrocatalytic activity with superior stability and methanol resistance to commercial 30 wt% Pt/C catalyst in 0.1 m KOH solution. Such enhanced performance can be ascribed to the stable and highly open network consisting of NEMC and G with fully exposed active sites, thereby leading to durable catalytic activity.