Facile hydrothermal deposition of Copper-Nickel sulfide nanostructures on nickel foam for enhanced electrochemical performance and kinetics of charge storage

In this study, novel binder-free copper-nickel-sulfur (CNS) nanostructures are deposited on 3D Ni foam (CNS/Ni) by a facile hydrothermal technique. A step-wise evaluation of the CNS nanostructures is systematically carried out by varying the hydrothermal reaction times (3, 6, 9, 18, and 27 h). The structural phase, chemical composition, and morphological evolution were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (SEM) respectively. The CNS deposited at 18 h shows interconnected 2D nanoflakes that provide maximum porosity, fast surface redox reaction sites, and improved ionic and electronic conductivity. The electrochemical measurements for CNS-18 show high areal capacitance (2589 mFcm⁻²), energy density (0.22 mWhcm⁻²), and power density (7.8 mWcm⁻²) at a current density of 20 mAcm⁻² owing to its high diffusion-controlled contribution (97 %) to the total current as compared to the other CNS samples. The kinetics of the electrochemical measurements are undertaken by the Dunn and Trasatti method. The CNS-18 sample shows long cyclic stability of approximately 81 % up to 7500 cycles. A CNS/AC asymmetric capacitor was fabricated to demonstrate its practical performance. It is surmised that CNS deposited on Ni foam can be used as an efficient electrode in energy storage applications.