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

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 (N-2) 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.