Facile synthesis of a reduced graphene oxide/cobalt sulfide hybrid and its electrochemical capacitance performance

Abstract

In this work, reduced graphene oxide (RGO) in situ composites with cobalt sulfide (CoS) are achieved through a facile hydrothermal approach. The morphology and structure of the composite materials have been investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and X-ray diffraction (XRD). The results have shown that the composites consist of CoS nanoparticles with a diameter of 30–50 nm uniformly dispersed on the basal plane of RGO. The maximum specific capacitance of 1130 F g⁻¹ measured by chronopotentiometry at a current density of 0.5 A g⁻¹ is obtained in a 6 M KOH aqueous solution, which is 2.4 times higher than that of pure CoS nanoparticle electrodes (473 F g⁻¹). Furthermore, RGO/CoS nanocomposite exhibits good cycling stability with 92.1% capacitance retention over 1000 cycles.