One-pot microwave-assisted synthesis of reduced graphene oxide/nickel cobalt double hydroxide composites and their electrochemical behavior

Reduced graphene oxide (RGO)/nickel cobalt (NiCo) double hydroxide composites were synthesized by one-pot microwave-assisted method in propylene carbonate. This method is efficient because the reduction of graphene oxide and the formation of hydroxide particles on the graphene sheets were simultaneously produced. We investigated an effect of microwave irradiation in organic solvent and an electrochemical influence of nickel and cobalt ratio in double hydroxide. Morphological characterization was performed by XRD, FTIR, XPS and FE-SEM. It was found that the NiCo double hydroxide particles were well decorated on the surface of RGO sheets and the reduction of graphene oxide was completed by short-term microwave irradiation. Electrochemical behavior was also measured by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge performance. The highest specific capacitance was $1622F\;g^{-1}$ obtained at (RGO)/NiCo 2:1 (weight ratio of nickel to cobalt was 2-1). Furthermore, the composites showed higher capacitance, as well as lower resistance, better rate capability and longer cycle life rather than $RGO/Ni(OH)_2$ and $RGO/Co(OH)_2$.