Enhancing the electrochemical properties of a nickel–cobalt-manganese ternary hydroxide electrode using graphene foam for supercapacitors applications

Abstract

This study has investigated the effect of the incorporation of graphene foam (GF) into the matrix of a ternary transition-metals hydroxide containing nickel, cobalt, and manganese for optimal electrochemical performances as electrodes for supercapacitors applications. An adopted simple, low-cost co-precipitation synthesis method involved the loading a mass of the ternary metal hydroxides (NiCoMn-TH) onto various GF mass loading so as to find ints effect on the electrochemical properties of the hydroxides. Microstructural and chemical composition of the various composite materials were investigated by employing scanning/transmission electron microscopy (SEM/TEM), x-ray diffraction (XRD), Raman spectroscopy, and N₂ physisorption analysis among others. Electrochemical performances of the NiCoMn-TH/200?mg GF composite material evaluated in a three-electrode system using 1?M KOH solution revealed a maximum specific capacity around 178.6 mAh g^?1 compared to 76.2 mAh g^?1 recorded for the NiCoMn-TH pristine material at a specific current of 1 A g^?1. The best mass loading of GF nanomaterial (200?mg GF), was then utilised as a positive electrode material for the design of a novel hybrid device. An assembled hybrid NiCoMn-TH/200?mg GF//CSDAC device utilizing the NiCoMn-TH/200?mg GF and activated carbon derived from the cocoa shell (CSDAC) as a positive and negative electrode, respectively, demonstrated a sustaining specific capacity of 23.4 mAh g^?1 at a specific current of 0.5 A g^?1. The device also yielded sustaining a specific energy and power of about 22.32 Wh kg^?1 and 439.7?W?kg^?1, respectively. After a cycling test of over 15,000 cycles, the device could prove a coulombic efficiency of?~?99.9% and a capacity retention of around 80% within a potential range of 0.0–1.6?V at a specific current of 3?A?g^?1. These results have demonstrated the prodigious electrochemical potentials of the as-synthesized material and its capability to be utilized as an electrode for supercapacitor applications.