Embedding Cobalt Into ZIF-67 to Obtain Cobalt-Nanoporous Carbon Composites as Electrode Materials for Supercapacitor

Metallic cobalt nanoparticles are embedded into ZIF-67 (Co(MeIM)(2), MeIM=2-methylimidazole) by a facile method. The X-ray diffraction (XRD) results show that the metallic cobalt crystals in the composite do not come into existence obviously until the carbonation temperature reaches 700 degrees C. According to the results of transmission electron microscope (TEM), the obtained Co/ZIF-67 maintains the structure of ZIF-67. In addition, the cobalt-nanoporous carbon composites process the carbon-shell/cobalt-core architecture, which inherits from the porous structure of Co/ZIF-67. What is more, the grain sizes of the cobalt/carbon composites obtained at 700 degrees C, 800 degrees C, 900 degrees C and 1000 degrees C are 2.1 nm, 3.1 nm, 9.9 nm and 14.8 nm, respectively. As a result, the specific capacitance of the composites material is up to 511.5 Fg(-1) at a current density of 100 mAg(-1) in 1.0 M KOH electrolyte. More significantly, the comparative investigations at different carbonization temperatures suggest the capacitance is mainly based on the redox mechanism.