With increasing globalization and the urgent need for sustainable energy solutions, electrochemical water splitting has emerged as a crucial technology for clean energy production. In this study, we report the successful synthesis of 0.1 % Fe-doped NiS2 via a one-step hydrothermal method. The incorporation of Fe into the NiS2 matrix significantly enhances its electrochemical performance, as evidenced by a remarkable reduction in overpotential, to 180 mV at a current density of 10 mA cm-2, compared to 250 mV for undoped NiS2. Additionally, the Fe-doped NiS2 exhibits a reduced Tafel slope, high double layer capacitance, and lower charge transfer resistance than undoped NiS2, indicating improved reaction kinetics for oxygen evolution. These improvements are attributed to the enhanced conductivity and catalytic activity imparted by Fe doping, which facilitates more efficient charge transfer and reaction processes at the electrode surface. The results suggest that Fe-doped NiS2 is a highly promising and robust candidate for applications in electrochemical energy conversion. Moreover, the doping strategy employed here offers a valuable approach for tailoring the properties of other metal sulfides and chalcogenides, paving the way for the design of next generation electrocatalysts that can drive large-scale energy conversion processes with minimal energy loss.

As the pace of technological advances accelerates, the role of electrical energy storage has become increasingly important. Among various storage solutions, supercapacitors are garnering significant attention. Their unique attributes, including high power density, rapid charge/discharge capabilities, and extended lifecycle, position them as a promising alternative to conventional batteries. This study investigates the synthesis of a nickel oxide (NiO) and nickel oxide/graphene oxide (NiO/GO) composite using a single-step hydrothermal method, to evaluate their potential as supercapacitor electrode materials. The synthesized NiO, graphene oxide (GO), and NiO/GO composite were comprehensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy to analyze their crystal structures and chemical bonding. The XRD analysis confirmed the formation of an NiO phase with a rhombohedral crystal structure, and no change after GO incorporation. SEM analysis revealed the formation of spherical NiO particles and porous morphology of the NiO/GO composite, which also exhibited a spherical shape. The GO displayed a randomly arranged wrinkled sheet-like structure. Electrochemical analysis of the NiO/GO composite exhibited a remarkable specific capacitance of 893 F g-1 at a current density of 1 A g-1, surpassing that of NiO and GO alone, demonstrating NiO/GO has promising performance for supercapacitor applications. The charge transfer resistance, derived from the Nyquist plot, suggests that the reduction in charge transfer resistance contributed significantly to the improved capacitance. Additional stability studies of over 5,000 cycles at 5 A g-1 revealed an 85 % initial capacitance retention, confirming the advantages of GO inclusion to improve material retention for superior long-term performance. The asymmetric supercapacitor (ASC) assembled using an electrode with the configuration NiO/GO//activated carbon (AC) showed a specific capacitance of 77.8 F g-1 obtained at a current density of 0.5 A g-1.