Synthesis of Nano-Flower Metal-Organic Framework/Graphene Composites As a High-Performance Electrode Material for Supercapacitors

Great emphasis has always been placed on exploring electrode materials with high conductivity and high level of electrolyte availability for supercapacitors as next-generation energy storage devices. Recently, metal-organic frameworks (MOFs) have been used as electrode materials for supercapacitors due to their suitability of porosity and high surface area, and their structure and synthesis have been widely studied. However, using single-component metal-organic frameworks in supercapacitors results in poor electrical conductivity, insufficient stability, and poor mechanical properties, thwarting the effect of high capacity and efficient performance. In this paper, a useful strategy was employed to reduce the electric resistance of metal-organic frameworks by interlacing metal-organic framework crystals with graphene. Cu-MOFs/graphene hybrid composites were successfully fabricated and then characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, powder x-ray diffraction, Raman spectroscopy, Brunauer-Emmett-Teller and electrochemical techniques. The prepared nanocomposite showed outstanding electrochemical performance owing to the synergistic effects of the Cu-MOFs specific structure and high conductivity of graphene, yielding a high specific capacitance of 482 F g(-1) at a scan rate of 10 mV s(-1) and a good cycle lifetime along with 93.8% specific capacitance retaining at current density of 0.3 A g(-1) after 1000 cycles in 6 M KOH aqueous electrolyte. Electrochemical examinations confirmed the existence of synergistic effects between Cu-MOF and graphene in the fabricated hybrid composites, making it an ideal advanced electrode candidate for supercapacitor applications. Moreover, a simple asymmetric supercapacitor was assembled in a 6 M KOH electrolyte with Cu-MOF/G and activated carbon as positive and negative electrodes, respectively, which renders high energy density (34.5 Wh kg(-1)) and power density (1350 W kg(-1)) at the current density of 0.5 A g(-1).