Synthesis of zeolitic imidazolate framework-67 nanocube wrapped by graphene oxide and its application for supercapacitors

Abstract

In this study, a nanocube of zeolitic imidazolate framework-67 (ZIF-67) was prepared by blending cobalt nitrate hexahydrate and 2-methylimidazole together in aqueous solutions containing hexadecyltrimethylammonium bromide (CTAB). Then, grapheme oxide (GO) wrapped ZIF-67 nanocomposites (ZIF-67/GO-n) were prepared by one-pot stirring method at room temperature. The morphology and microstructure of ZIF-67 and its GO nanocomposites were investigated by Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) specific surface area analysis. Electrochemical capacitance properties of all samples were characterized by cyclic voltammetry and chronopotentiometry, respectively. The results demonstrated that the content of GO used during synthesis process affected the specific capacity of nanocomposites while they were constructed as supercapacitor electrode. Compared with pure GO and ZIF-67 nanocubes, ZIF-67/GO-n composites had better specific capacitance. While the concentration of GO was 2 wt% based on their initial total mass of two reactants, ZIF-67/GO-2 composite presents a specific capacitance of 100.41 F g−1 at a sweep rate of 5 mV s−1. The good electrochemical performance of ZIF-67/GO-n composite may be credited to large BET surface area of ZIF-67 nanocubes and good conductivity of GO, and thus is expected to become a potential electrode material for supercapacitors.