Carbon coated nickel sulfide/reduced graphene oxide nanocomposites: facile synthesis and excellent supercapacitor performance

A novel CCNS-RGO composite with carbon coated nickel sulfide (CCNS) particles decorated on reduced graphene oxide (RGO) sheets is prepared through a facile hydrothermal route. The CCNS particles, consisting of nickel sulfide (Ni3S2) cores with an average size of 25.5 nm and carbon shells with a thickness of several nanometers, are uniformly dispersed on RGO sheets. The CCNS-RGO composites are investigated as electrode materials for supercapacitors. It is found that the CCNS-RGO composites exhibit an enhanced capacitive performance as compared with individual CCNS and RGO. The specific capacitance for CCNS-RGO is as high as 860.1 F g-1 at the scan rate of 5 mV s-1, and the capacitance retention reaches 98.6% after 500 cycles at the current density of 5 A g-1, indicating an excellent cycling stability of CCNS-RGO. The greatly enhanced capacitive performance of CCNS-RGO can be mainly attributed to the synergistic effect between RGO and CCNS particles, the improved conductivity and relatively larger surface area of the composites. The results demonstrate that metal sulfide/graphene nanocomposites are promising electrode materials for high performance energy storage applications.