Template-free solvothermal synthesis of NiS2 microspheres on graphene sheets for high-performance supercapacitors

• An easy template-free synthetic approach to the fabrication of graphene/NiS2 composite through a solvothermal process was developed.
• Using environmentally-friendly Na2S2O3·5H2O as reducing agent for GO as well as sulfur source for NiS2.
• The prepared graphene/NiS2 composite shows a high specific capacitance value of 478.1 F/g at a current density of 0.5 A/g.

Graphene/NiS2 composite was obtained through a template-free solvothermal reaction using graphene oxide (GO), Na2S2O3·5H2O and NiCl2·6H2O as reactants. Na2S2O3·5H2O plays an important role as the reducing agent for GO as well as the sulfur source for NiS2. Electrochemical behaviour of the graphene/NiS2 composite was studied through cyclic voltammetry and galvanostatic charge-discharge. As for the applications in supercapacitors, graphene/NiS2 composite shows a great value of 478.1 F/g at a current density of 0.5 A/g. Furthermore, the capacitance of graphene/NiS2 decreases only 10.7% of its initial value after 2000 cycles.