Enhanced Supercapacitor Performance Using a Co3O4@Co3S4 Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes

To avoid an enormous energy crisis in the not-too-distant future, it be emergent to establish high-performance energy storage devices such as supercapacitors. For this purpose, a three-dimensional (3D) heterostructure of Co3O4 and Co3S4 on nickel foam (NF) that is covered by reduced graphene oxide (rGO) has been prepared by following a facile multistep method. At first, rGO nanosheets are deposited on NF under mild hydrothermal conditions to increase the surface area. Subsequently, nanowalls of cobalt oxide are electro-deposited on rGO/Ni foam by applying cyclic-voltammetry (CV) under optimized conditions. Finally, for the synthesis of Co3O4@Co3S4 nanocomposite, the nanostructure of Co3S4 was fabricated from Co3O4 nanowalls on rGO/NF by following an ordinary hydrothermal process through the sulfurization for the electrochemical application. The samples are characterized by using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained sample delivers a high capacitance of 13.34 F cm(-2) (5651.24 F g(-1)) at a current density of 6 mA cm(-2) compared to the Co3O4/rGO/NF electrode with a capacitance of 3.06 F cm(-2) (1230.77 F g(-1)) at the same current density. The proposed electrode illustrates the superior electrochemical performance such as excellent specific energy density of 85.68 W h Kg(-1), specific power density of 6048.03 W kg(-1) and a superior cycling performance (86% after 1000 charge/discharge cycles at a scan rate of 5 mV s(-1)). Finally, by using Co3O4 @Co3S4/rGO/NF and the activated carbon-based electrode as positive and negative electrodes, respectively, an asymmetric supercapacitor (ASC) device was assembled. The fabricated ASC provides an appropriate specific capacitance of 79.15 mF cm(-2) at the applied current density of 1 mA cm(-2), and delivered an energy density of 0.143 Wh kg(-1) at the power density of 5.42 W kg(-1).

Automated summary

A high-performance energy storage device using Co3O4@Co3S4 nanocomposite on nickel foam covered with reduced graphene oxide has been successfully synthesized, demonstrating excellent electrochemical performance with high capacitance and energy density, as well as superior cycling stability.