Enhanced Supercapacitive Performance of Chemically Grown Cobalt–Nickel Hydroxides on Three-Dimensional Graphene Foam Electrodes

Abstract

Chemical growth of mixed cobalt–nickel hydroxides (Co_<i>x</i>Ni_1–<i>x</i>(OH)₂), decorated on graphene foam (GF) with desirable three-dimensional (3D) interconnected porous structure as electrode and its potential energy storage application is discussed. The nanostructured Co_<i>x</i>Ni_1–<i>x</i>(OH)₂ films with different Ni:Co (<i>x</i>) compositions on GF are prepared by using the chemical bath deposition (CBD) method. The structural studies (X-ray diffraction and X-ray photoelectron spectroscopy) of electrodes confirm crystalline nature of Co_<i>x</i>Ni_1–<i>x</i>(OH)₂/GF and crystal structure consists of Ni­(OH)₂ and Co­(OH)₂. The morphological properties reveal that nanorods of Co­(OH)₂ reduce in size with increases in nickel content and are converted into Ni­(OH)₂ nanoparticles. The electrochemical performance reveals that the Co_0.66Ni_0.33(OH)₂/GF electrode has maximum specific capacitance of ∼1847 F g^–1 in 1 M KOH within a potential window 0 to 0.5 V vs Ag/AgCl at a discharge current density of 5 A g^–1. The superior pseudoelectrochemical properties of cobalt and nickel are combined and synergistically reinforced with high surface area offered by a conducting, porous 3D graphene framework, which stimulates effective utilization of redox characteristics and communally improves electrochemical performance with charge transport and storage