Cobalt Sulfide/Reduced Graphene Oxide Nanocomposite with Enhanced Performance for Supercapacitors

Abstract

A cobalt sulfide decorated reduced graphene oxide (CoS/rGO) nanocomposite was successfully synthesized via a facile one-step hydrothermal route assisted by ethylenediamine. The crystalline phase, structure and morphology of the products were systematically characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, nitrogen (N₂) absorption–desorption isotherm, Raman spectra and thermogravimetric analysis. The results show that CoS nanoparticles with the size of 30–100 nm are well dispersed on or anchored in the creasy rGO sheets substrate. Combining the CoS compound nature with the rGO outstanding characteristics, the as-obtained CoS/rGO as an electrode for a supercapacitor harvests high specific capacitance, excellent long-cycle stability and remarkable high-rate capability, which are all superior to those of pristine CoS. Importantly, this nanocomposite possesses a specific capacitance of 813 F g⁻¹ at 0.5 A g⁻¹ (about 2 times that of pure CoS) and excellent cycling stability with 91.2% capacitance retention after 1000 repetitive charge–discharge cycles. It is noteworthy that this approach can be readily applicable to the nanoparticle decoration of graphene sheets and the preparation of other graphene-based nanocomposites for supercapacitors.