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

Abstract

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.