Enhanced electrochemical performance of the electrodeposited nickel sulfide on ZIF-67@RGO composite for supercapacitor applications

Zeolitic imidazolate frameworks (ZIF), as a form of metal-organic frameworks (MOFs), are promising materials used as electrodes for energy storage devices. Their high electrical conductivity results from numerous conjugated systems and the collaboration between the ligand and cobalt significantly enhances their redox capacity. The bulk electrical conductivity and specific capacitance of ZIF materials can be enhanced by the incorporation of rGO and metal sulfide, respectively. Herein, ZIF-67@RGO nanocomposite was fabricated and then modified with 20.0 wt.% Ni nanoparticles followed by co-electrodeposition of sulfur as a novel electrocatalyst. The prepared composites were analyzed using various techniques, including FT-IR, XRD, XPS, SEM, and EDX mapping. The electrochemical performance of the prepared composite electrodes was measured using different techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge (GCD). The S-Ni/ZIF-67@RGO electrode displayed excellent electrochemical behaviour which is evident in the high value of the specific capacitance of 1142.3 F g-1 at a current density of 1 A g-1. On the other hand, an asymmetric supercapacitor (ASC) was assembled by employing the unique composite material in conjunction with conductive carbon black. The power and energy densities of the ASC device were 774 W kg-1 and 88.2 Wh kg-1, respectively. The capacitance of S-Ni/ZIF-67-RGO is retained at 90.8% even after 3000 cycles, suggesting remarkable cycle stability. This study expands the application scope of ZIF-67 and introduces a new method for fabricating novel electrode materials.