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Supercapacitors are an emerging energy-storage system with a wide range of potential applications. In this study, highly porous nickel-cobalt-oxide@reduced graphene oxide (Ni-Co-O@RGO-s) nanosheets were synthesized as an active material for supercapacitors using a surfactant-assisted microwave irradiation technique. The RGO-modified nanocomposite showed a larger specific area, better conductivity, and lower resistivity than the unmodified nanocomposite because the RGO facilitated faster ion diffusion/transport for improved redox activity. The synergistic effect of Ni-Co-O@RGO-s resulted in a high capacitance of 1903 F/g (at 0.8 A/g) in a mixed KOH/redox active K3Fe(CN)6 electrolyte. The asymmetric Ni-Co-O@RGO-s//AC supercapacitor device yielded a high energy density and power density of 39 Wh/kg and 7500 W/kg, respectively. The porous structure and combination of redox couples from both the electrode and electrolyte provided a highly synergistic effect, which improved the performance of the supercapacitor device.
With the vast exploration of the applications of graphene, researchers are assessing different methods for fabricating graphene-based electrode material with high capacitance but low material and energy costs. In this study, reduced graphene oxide/nickel oxide (RGO/NiO) nanocomposites were prepared using a non-aqueous solvent-based method followed by calcination. Nickel acetate tetrahydrate and tert-butanol were used as the precursor and solvent, respectively. Ultrasmall nickel oxide nanoparticles, ca. 8.0 nm in size, were deposited on the surface of the graphene sheets simultaneously with the partial reduction of graphene oxide. The resulting RGO/NiO electrode exhibited a high capacitance of 689 F g⁻1 at a current density of 0.8 A g⁻1. After 1500 cycles, the specific retention and the coulombic efficiency yielded to 86.34% and 96.39%, respectively, which supports the viability of this composite as an alternative activated material with high electrochemical performance.