Enhanced electrochemical properties of NiS@CeO2 spherical nanoflakes

Abstract

Herein we report synthesis of bare cerium oxide nanoparticles from cerium hydroxide and NiS@CeO₂ nanocomposite (NC) from nickel cinnamaldehyde thiosemicarbazone complex (single source molecular precursor) and CeO₂ nanoparticles by solvothermal method using ethylene glycol as a capping agent. These materials were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray techniques. The crystallite size of the composite nanoparticles calculated using XRD is 17.99 nm. TEM shows spherical shape morphology of NiS@CeO₂ nanocomposite with average particle size less than 10 nm. Electrochemical properties of bare CeO₂ and NiS@CeO₂ NC electrodes were evaluated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The electrochemical measurements show that the capacitance value of NiS@CeO₂ NC electrode is significantly higher (707.84 F g⁻¹) compared to bare CeO₂ electrode (80.91 F g⁻¹) at current density 1 A g⁻¹. This can be attributed to synergistic effect in nanocomposite. The cycle stability of NiS@CeO₂ NC electrode was found to be 98.41 % even after 6000 charge–discharge cycles at 2 A g⁻¹ current density.