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−phase synthesis 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 nanocomposites using for high−performance hybrid supercapacitor.