Facile Synthesis of 3D NC-rGO@Ni-Foam Nanonetwork as a Binder-Free Hybrid Electrode Material for Ultrahigh Capacitance Applications

In this study, a three-dimensional (3D) structured nanomaterial has been developed to enhance the electrochemical properties of supercapacitors. The nanomaterial's structure was engineered by incorporating divalent metal ions (M²⁺: Ni²⁺ and Co²⁺) into reduced graphene oxide (rGO) layers supported on nickel foam (3D NC-rGO@Ni-foam), forming a binder-free hybrid electrode. This was accomplished through a combination of in situ wet-chemistry and hydrothermal techniques. This binder-free electrode material has stacked layers of rGO, which improve conductivity, while the M²⁺ ions intercalated between these layers function as redox couples, thereby significantly improving the specific capacitance. Furthermore, the Ni-foam substrate offers a porous configuration and works as the current collector. In contrast to traditional slurry coating methods, the in situ growth of nanostructures on Ni-foam is expected to enhance strong adhesion, high conductivity, and effective ion transport. The structural morphology, chemical composition, and electrochemical behavior of the 3D NC-rGO@Ni-foam electrode were comprehensively investigated using techniques such as scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), electrochemical impedance spectroscopy (EIS), and other analytical methods. This binder-free 3D hybrid electrode material demonstrated a specific capacitance (<i>C</i> _s) of 2612 F/g at 1 A/g. The symmetric device fabricated also demonstrated a substantial energy density (<i>E</i>) of 55 W·h/kg and a power density (<i>P</i>) of 155 W/kg across a wide potential window of 2.5 V. The electrochemical characteristics and mechanical stability of 3D NC-rGO@Ni-foam indicate its potential as a high-performance electrode material for scalable energy storage systems.