Nanocomposite of ZIF-67 metal-organic framework with reduced graphene oxide nanosheets for high-performance supercapacitor applications

Demand for new energy storage devices stimulates efforts to develop the novel and effective composites with promising properties. For this purpose, composite materials, including carbonaceous materials such as graphene, carbon nanotube and carbon fiber and metal containing compounds have attracted an increasing attention because of better electrochemical performance as compared to their single material analogs. Here, the Nanocomposite consisting of ZIF-67 nanocrystals on reduced graphene oxide nanosheets (rGO/ZIF-67) has been prepared via a simple and facile ultrasonic route at room temperature. Electrochemical properties of the rGO/ZIF-67 and ZIF-67 were measured by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy techniques in 6 M KOH as an electrolyte. The nanocomposite of rGO/ZIF-67 showed highest specific capacitance value of 210 F/g at a current density of 1 A/g which is much higher than that of ZIF-67 at a similar current density (103.6 F/g). EIS measurements exhibited lower values of internal resistance and charge transfer resistance for the composite electrode in comparison to ZIF-67 electrode, indicating that the prepared nanocomposite has higher electrical conductivity. The prepared nanocomposite showed excellent cycling performance (80% after 1000 successive cycles at a current density of 1 A/g), indicating that the ZIF-67 nanocrystals immobilized on the surface of rGO nanosheets are beneficial to improving electrochemical properties as compared to ZIF-67 single analogs and is an appropriate candidate for supercapacitor applications.