Synthesis and study of nickel sulfide nanoparticles and nanostructures for energy storage device applications

Nickel sulfide (NiS) nanostructures were synthesized by simple and low-cost hot injection method (HIM). The effects of sulfur concentration on the compositional, morphological, optical and structural properties of NiS nanoparticles were investigated in detail. The X-ray diffraction pattern confirms the formation of NiS nanoparticles without any impurities. The Raman spectra show the presence of NiS active modes in the synthesized material prepared at different sulphur concentration. The electrochemical performance of the synthesized NiS powder was estimated through cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in KOH electrolyte. The specific capacitance (CS) of the NiS powder electrode was measured with the three-electrode method, and it confirms the maximum CS of 315.8 F/g at a scan rate of 5 mVs$^{-1}$. The calculated value of energy density and power density of the NiS powder electrode is 3.324 WhKg$^{-1}$ and 199 WKg$^{-1}$ respectively at a lower current density. Present study provides a simple and low-cost HIM is capable for controlling the structural, optical, and morphological properties of nickel sulfide series, which would be of great potential for the synthesis of other metal sulfides.