Enhanced Supercapacitor Performance Using a Co<sub>3</sub>O<sub>4</sub>@Co<sub>3</sub>S<sub>4</sub> Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes
Hanieh Ansarinejad, Mehdi Shabani‐Nooshabadi, Sayed Mehdi Ghoreishi
Abstract
Abstract 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 Co 3 O 4 and Co 3 S 4 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 Co 3 O 4 @Co 3 S 4 nanocomposite, the nanostructure of Co 3 S 4 was fabricated from Co 3 O 4 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 Co 3 O 4 /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 Co 3 O 4 @Co 3 S 4 /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 .