Carbon Thin-Layer-Protected Active Sites for ZIF-8-Derived Nitrogen-Enriched Carbon Frameworks/Expanded Graphite as Metal-Free Catalysts for Oxygen Reduction in Acidic Media

Abstract

Generally, sluggish oxygen reduction reaction (ORR) kinetics on cathode limits the practical application of the direct methanol fuel cell (DMFC). In this study, zeolitic-imidazolate-framework-8 (ZIF-8)-derived carbon is used to decorate expanded graphite (EG) to prepare a nitrogen-rich porous metal-free carbon framework (Z8-NCF-P/EGs) as catalyst for ORR in DMFC. Through use of a simple one-pot method, ZIF-8 is firmly anchored on EG to obtain the ZIF-8/EG precursor via a polyvinypyrrolidone (PVP)-assisted route. After carbonization and acid etching, the formed micromesoporous structure contributes to the high specific surface area and well-distributed porous 3D bulk networks of Z8-NCF-P/EGs, which provide short diffusion paths for rapid oxygen and mass transfer kinetics. Z8-NCF-P/EG-10 (ZIF-8/EG weight ratio of 10) exhibits activity comparable to that of commercial Pt/C (10 wt %) and methanol tolerance and stability much higher than those of Pt/C in acidic electrolyte. EG contributes to the uniform distri...