Tailoring nickel disulfide for energy applications: A hydrothermal approach to enhanced performance

This study focused on synthesizing the nickel disulfide (NiS₂) with a non-uniform microflower morphology via hydrothermal synthesis for supercapacitor and water-splitting applications. X-ray diffraction, Fourier transform infrared and Raman spectroscopy, Scanning electron microscopy, and Transmission electron microscopy confirmed the crystal structure, presence of various functional groups, stretching/bending vibration present in the prepared NiS₂ material, and surface morphology and interatomic illustration of the NiS₂ materials. As a result, the prepared materials were utilized for the electrochemical and electrocatalytic measurements using flexible steel mesh as a working electrode in 1 M KOH via a three-electrode cell system. Using a flexible steel mesh electrode, the optimized NiS₂ electrode exhibited a specific capacitance of 630 F/g at 5 mA/cm² with 92 % retention after 5000 cycles. An assembled asymmetric supercapacitor device achieved energy and power densities of 13 Wh/kg and 900 W/kg, respectively, with good cycling stability. For water splitting, the same electrode showed a low overpotential of 140 mV, a Tafel slope of 73 mV/dec, and a high electrochemically active surface area (46.50 cm²). These results demonstrate the potential of NiS₂ for dual applications in sustainable energy storage and conversion.