Exploring the structural and charge storage properties of Ni–ZnS/ZnO composite synthesized by one-pot wet chemical route

Abstract

Metal oxide-metal sulfide-based composites of desired properties are of great technological importance because of their applications ranging from photovoltaics to energy storage devices. Herein, we report on the structural and charge storage capabilities of nickel-doped zinc sulfide-decorated zinc oxide (Ni–ZnS/ZnO) composite prepared by wet chemical route. The synthesis of ZnO, Ni–ZnS, and Ni–ZnS/ZnO was performed at 80 °C in a single vessel which was followed by annealing at 300 °C for 1 h. Scanning electron microscopy (SEM) images indicated flower-like morphology of the ZnO decorated with Ni-doped ZnS (Ni–ZnS). The material exhibited characteristic X-ray diffraction (XRD) signals corresponding to ZnO and Ni–ZnS which confirmed the formation of a composite structure. Energy-dispersive X-ray analysis, UV–visible spectroscopy, and Fourier Transform Infrared (FTIR) spectroscopy measurements revealed the successful formation of Ni–ZnS/ZnO composites. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were carried out to examine the energy storage capabilities of the synthesized Ni–ZnS/ZnO composite. The composite electrode demonstrated a specific capacitance of 354 F g−1 in 1 M KOH electrolyte which was higher than that of the Ni–ZnS (154.7 F g−1) and ZnO (132 F g−1). The enhanced capacitive performance of the composite is attributed to the low charge transfer resistance and high electrochemically active specific surface area (27.54 m2 g−1), as revealed by EIS results.