Facile solid-phase synthesis of layered NiS/rGO nanocomposite for high-performance hybrid supercapacitor

Generally, transition metal sulfides and their composites are prepared by tedious and uneconomical liquid--phasesynthesis methods. In this work, we developed a facile solid-phase synthesis route for preparing NiS/ rGO nanocomposite by thermal treating a ternary solid mixture of nickel formate, elemental sulfur and GO in an autoclave under ambient atmosphere. The prepared nanocomposite exhibits a loose layered structure, spherical or ellipsoidal NiS nanoparticles with a size of 20-100 nm disperse on the well-separated rGO nanosheets. Due to the unique layered structure, the obtained NiS/rGO nanocomposite exhibits an ultrahigh specific capacity of 299.7 mAh g(-1) (2157.8 F g(-1)) at a current density of 2 A g(-1) and good rate capacity (161.2 mAh g(-1) at 15 A g(-1)). The hybrid supercapacitor device based on the layered NiS/rGO nanocomposite and an interconnected hierarchical porous carbon delivers a high specific energy of 56.1 Wh kg(-1) at a specific power of 880 W kg(-1) while exhibits a high capacity retention of 92.4% after 30,000 charge/discharge cycles, demonstrating the promising potential of the developed solid-phase synthesis route for the preparation of NiS/rGO nano-composites using for high-performance hybrid supercapacitor.