Effective microwave-assisted synthesis of graphene nanosheets/NiO composite for high-performance supercapacitors

A facile and fast strategy was used for synthesis of a petal-like graphene nanosheets (GNS)/NiO composite. Using this strategy, graphene oxide was reduced to graphene and formed the GNS/NiO composite via a microwave-assisted method without a complicated procedure and any controlling-agent. The product was characterized by X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analysis results have confirmed that petal-like NiO sheets are well dispersed on the surfaces of graphene nanosheets. The as-prepared composite was electrochemically tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy as an electrode material for supercapacitors. The GNS/NiO composite exhibits a specific supercapacitance of 799 F g(-1) at a current density of 0.3 A g(-1) in 6 M KOH electrolyte and a long cycle life, along with 90% specific capacitance remaining after 1000 cycles. The electrochemical performance of the composite was significantly improved compared to bare graphene and NiO. This could be attributed to their architecture. The results presented here suggest that the GNS/NiO composite could have potential applications in high energy storage systems.