Graphene-based cobalt sulfide composite hydrogel with enhanced electrochemical properties for supercapacitors

The three-dimensional cobalt sulfides/graphene hydrogel (CoSGH) nanocomposites were fabricated via a facile one-step hydrothermal route in a water-isopropanol system. The structural, morphological and physical properties of the as-fabricated composites were investigated, and the results confirm that amorphous cobalt sulfide particles were successfully anchored onto graphene sheets. As electrode materials for supercapacitors, the composites exhibit a maximum specific capacitance (C-s) of 435.7 F g(-1) at a current density of 0.5 A g(-1) measured in 6 M KOH electrolyte, which is significantly higher than that of cobalt sulfides and graphene. Furthermore, the CoSGH nanocomposites have also shown excellent cycling stability with 82.3% capacitance retention over 3000 cycles which is higher than that of pure cobalt sulfides. The enhanced electrochemical properties exhibited by CoSGH highlight the special hydrogel structure and synergistic effects between cobalt sulfides and graphene.