Unveiling the power of hexagon-shaped KCu7S4 towards hydrogen evolution reactions and supercapacitor electrodes: a bi-functional approach

Abstract

This study investigates the electrocatalytic hydrogen production and supercapacitor effectiveness of hexagonal KCu₇S₄, a material abundant in nature, which serves as a promising dual-functional material for sustainable applications. Concerning the electrochemical reactions, the KCu₇S₄ possesses a unique layered hexagonal structure that minimizes internal resistance and facilitates effective ion transport. Comprehensive characterization techniques such as X-ray diffraction (XRD), analysis, Laser Raman spectroscopy, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) showcase its beneficial structural properties. Techniques such as cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) were utilized to evaluate the true efficacy of the electrocatalytic hydrogen evolution reaction (HER). Galvanostatic charge–discharge (GCD) analysis was used to assess the performances of supercapacitor electrodes. The HER experiments indicate that KCu₇S₄ serves as an efficient electrocatalyst since it exhibits the lowest HER overpotential of 90 mV at − 10 mA cm⁻² and the Tafel slope of 138 mV dec⁻¹ (using Ni-foam as substrate). The supercapacitor examinations revealed that the KCu₇S₄ materials exhibited a greater specific capacitance value of 416 F g⁻¹ (three-electrode mode with graphite sheet) at 3 A g⁻¹ and 54 F g⁻¹ (from the device) at a current density of 1 A g⁻¹. The constructed device delivers a power density value of 700 W kg⁻¹ and an energy density value of 14.78 Wh kg⁻¹ respectively. These findings illustrated the feasibility of producing and utilizing KCu₇S₄ on a pilot scale as a bifunctional material for electrocatalyst and supercapacitor uses in practical scenarios.