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

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 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.

MOF-Derived Ultrathin NiCo-S Nanosheet Hybrid Array Electrodes Prepared on Nickel Foam for High-Performance Supercapacitors

“…For the Co-S/NF electrode material, the redox peaks were located at 0.27 and 0.10 V, respectively, and the corresponding redox reactions is as follows [ 43 ]: …”

Recent advances in energy storage with graphene oxide for supercapacitor technology

“…The fabrication process involves the reduction of GO to obtain reduced graphene oxide (rGO), which exhibits improved electrical conductivity. 30,189,190 The improved performance of electrode materials for high-energy SCs is shown in Fig. 6.…”

Ion‐exchange synthesis of microporous Co 3 S 4 for enhanced electrochemical energy storage

“…Microporous Co 3 S 4 film was synthesized from a Co 3 O 4 template film through a one-step ion-exchange process under optimized hydrothermal conditions via the following reaction 46 :…”