Effective OER activity of rhombohedral nickel sulphide nanoparticles supported via reduced graphene oxide

Abstract

Excessive utilization of fossil fuels is causing significant environmental contamination and energy loss, which has become a major problem today. Thus, there is a growing demand for green energy storage sources, such as water splitting, to address these energy concerns. Hydrogen gas is an economical and environmentally friendly energy source. It is produced from water and is known for being carbon-free. However, in current years, metal sulfides have gained significant interest as an efficient alternative to noble-metal-catalysts due to their capability to contribute to the oxygen evolution reaction (OER). The current work uses a hydrothermal approach to produce NiS/rGO nanocomposite, which is advantageous for commercial applications. It showed higher catalytic efficiency, low cost and convenient accessibility, which improves OER. The efficient fabrication and use of NiS/rGO nanocomposite material were confirmed and evaluated via several analysis approaches, such as XRD, SEM and BET, which showed unique structure, morphology and increased surface area. Furthermore, higher active regions provide a synergistic effect and the composite showed a significantly decreased over-potential (162 mV) at (10 mA/cm2) current-density (j) possessing a Tafel plot (32 mV/dec) for OER in 1 M KOH. The composite showed more active regions and more significant surface area potential for charge transfers due to its distinct structure, which makes the material more stable (40 h). By integrating carbon-based reduced graphene oxide (rGO) into oxygen-deficient NiS, the poor conductivity of the material may be enhanced. This improvement is shown by the low Rct (0.07 Ω) value measured via electrochemical impedance spectroscopy (EIS). The greater surface area (2852.5 cm2) at different scan rates (10–40 mV/s), is evidenced by ECSA measurement. Therefore, research indicates that combining a specific metal sulphide and reduced graphene oxide (rGO) can potentially improve electrocatalyst functionality and make it a feasible choice for OER applications in future due to its cost-effectiveness.