Synthesis of nickel sulfide-graphene oxide composite microflower structures to enhance supercapacitor performance

Ni(x)S(y)in various crystal phases (NiS, NiS2, and Ni3S4) was synthesized on thermally reduced graphene oxide (TRGO) by a one-step hydrothermal process. Microstructures and morphologies of as-prepared NixSy-TRGO composites were characterized. Ni(x)S(y)was formed as microflowers with average size of 1.1-2.3 mu m, which grew homogeneously on the curved TRGO nanosheets. Electrochemical performance of NixSy-TRGO was revealed with high specific capacitance of 1602.2 F g(-1)at 1 A g(-1)and favorable cycling retention of 90.81% after 3000 cycles at 5 A g(-1). An asymmetric supercapacitor device based on NixSy-TRGO||TRGO exhibited a superior energy density of 39.78 Wh kg(-1)at the power density of 0.75 kW kg(-1)with an cycling stability of 91.2% capacitance retention after 3000 cycles. Thus, the as-prepared NixSy-TRGO could be an advanced supercapacitor electrode material.