Facile synthesis of graphene based mixed metal sulphide nanocomposite for energy storage applications

Abstract

Supercapacitors, often referred to as electrochemical capacitors, are becoming more and more common because of their high-power density, long lifespan, and low maintenance requirements. The cobalt sulphide, nickel sulphide, and graphene oxide (CoS/NiS/GO) nanocomposites were developed because of their low cost and superior electrochemical characteristics for use in supercapacitors. Powder X-ray diffractometry and X-ray photoelectron spectroscopy analyses were used to assess the phase purity of each material. Scanner electron microscopy (SEM)/energy dispersive X-ray analysis (EDX) and transmission electron microscope (TEM) images were used to visualize the nanoscale morphology of the synthesized nanocomposite. With a standard three-electrode setup, platinum sheet was used as the counter electrode and Ag/AgCl was used as the reference electrode for all electrochemical studies. The working electrode was a composite made of graphene oxide on CoS, NiS, and nickel foam. In a solution of 3 M KOH, all electrochemical measurements were conducted. In comparison to the corresponding Rct (41.35 Ω.cm2) and Rf (55.62 Ω.cm2) for the GO electrode, the Rct and Rf for the CoS/NiS/GO electrode were found to be 1.99 Ω.cm2 and 2.70 Ω.cm2, respectively. This suggests that the CoS/NiS/GO electrode has significantly lower overall impedance, which could be one of the major contributing factors to the enhanced electrochemical performance of the CoS/NiS. The electrode made of CoS/NiS/GO nanocomposite has a specific capacitance of 1114 mAh/g at current density of 5 A/g. After 8000 charge-discharge cycles, CoS/NiS/GO electrodes with a current density of 5 A/g still had 80% of their original specific capacitance. The CoS/NiS/GO samples have been shown to have energy densities and power densities of 674.12 Wh/kg and 8089.44 W/kg, respectively. Galvanostatic charge/discharge experiments reveal that the CoS/NiS/GO nanocomposite has a high specific capacitance and a long cycle life.