Synergistic effect of Ni-based metal organic framework with graphene for enhanced electrochemical performance of supercapacitors

Abstract

Developing advanced electrode materials with metal–organic frameworks (MOFs) has increasingly attracted attentions as an effective method for improving supercapacitors performances. However, their poor conductivity has limited their use in energy applications. In this paper, an effective strategy is presented to reduce the electric resistance of MOFs by the in situ synthesis of Ni-based MOFs with graphene (Ni-MOF/graphene). The fabricated Ni-MOF/graphene composite was characterized by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), Raman spectra, Brunauer–Emmett–Teller (BET) and electrochemical techniques. Due to the synergistic effects between Ni-MOF and graphene, the fabricated electrode showed a higher specific capacitance of 1017 F g−1 at the scan rate of 10 mV s−1 compared to Ni-MOF (660 F g−1) and graphene (148 F g−1) electrodes. Moreover, a simple asymmetric supercapacitor was assembled in a 6 M KOH electrolyte with Ni-MOF/G and activated carbon as positive and negative electrodes, respectively, which resulted to the high energy density of 39.43 Wh kg−1 and the power density of 34.29 W kg−1. The device also showed good cycle lifetime with 93.5% specific capacitance retaining at the current density of 0.3 A g−1 after 1000 cycles.