Hydrous nickel sulphide nanoparticle decorated 3D graphene foam electrodes for enhanced supercapacitive performance of an asymmetric device

Hydrous nickel sulphide is successfully synthesized on graphene foam (Ni9S8/GF) using a facile chemical bath deposition (CBD) method. The physico-chemical properties (XRD, RAMAN, FE-SEM and TEM) show that hydrous nanocrystalline Ni9S8 particles are uniformly distributed over the surface of multilayered graphene foam (MGF). The electrochemical capacitive measurement results reveal that the Ni9S8/GF 3D porous electrode exhibits high specific capacitance of 2055 F g(-1) at 2 A g(-1). Moreover, an asymmetric supercapacitor fabricated using the Ni9S8/GF electrode as the positive electrode and activated carbon (AC/NF) as a negative electrode shows a high energy density of 51.11 W h kg(-1) at a power density of 2.66 kW kg(-1). The enhanced capacitive performance of an ACS device can be attributed to the introduction of Ni9S8/GF, since 3D GF offers a porous structure with high specific surface area and continuous conducting structure, which possesses more active sites for charge storage and assists fast charge transport through the continuous 3D graphene structure.