High performing Zn-embedded Ni9S8 nanosphere electrodes for Pseudo-supercapacitors

Highly electroactive Zn-embedded Ni9S8 nanosphere and its ZnS/NixS6-based nanocomposites were prepared by a simple hydrothermal route. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectra (FTIR), high-resolution scanning electron microscope (HR-SEM), transmission electron microscope (TEM), energy-dispersive X-ray spectral (EDX) techniques. The XRD analysis revealed the formation of orthorhombic phase of Zn-embedded Ni9S8 nanosphere for hydrothermally treated sample. The supercapacitance behavior of crystalline Zn-embedded Ni9S8 nanosphere and ZnS/NixS6 nanocomposite modified electrodes were investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques. Zn-embedded Ni9S8 nanosphere prepared by hydrothermal route achieved highest specific capacitance value of 145 F/g in 1 A/g compared to the calcined sample modified electrodes. The maximum capacity retention of 100, 96 and 90% at 2000 cycles @1 A/g were observed for the pristine Zn–Ni9S8 and calcined Zn-Ni9S8 at 200 and 300 °C, respectively.