Nanomorphology-dependent pseudocapacitive properties of NiO electrodes engineered through a controlled potentiodynamic electrodeposition process

Abstract

Three nickel oxide (NiO) electrodes of different morphologies have been successfully engineered through a controlled potentiodynamic electrodeposition process in the presence of different nickel precursors. The effect of nickel precursors on the structural, morphological and pseudocapacitive properties of NiO thin film electrodes have been systematically investigated. The structural information obtained from the X-ray diffraction patterns confirm the formation of cubic structured NiO. The field-emission scanning electron microscopic images endorses for the evolution of uniformly distributed up-grown nanoflakes, irregular nanoflake-like and well-covered porous architecture comprised of interconnected uniform nanoflakes of NiO nanostructures with surface contact angle values 126°, 148° and 104°. The effect of the developed NiO nanostructures on pseudocapacitance behavior has been thoroughly investigated using cyclic voltammetry, chronopotentiometric charge–discharge and electrochemical impedance spectroscopy measurement techniques. The optimal specific capacitance of 893 F g⁻¹ has been achieved for NiO electrode with interconnected nanoflake-type morphology at the scan rate of 5 mV s⁻¹. Furthermore, these NiO electrodes have demonstrated long-term cycling stability in KOH electrolyte. The electrochemical impedance spectroscopy measurements carried out on developed NiO nanostructured electrodes corroborate that, NiO electrode composed of uniformly distributed interconnected nanoflakes is the best and most suitable electrode for good capacity electrochemical supercapacitors.