Porosity-tuned NiO nanoflakes: Effect of calcination temperature for high performing supercapacitor application

Aiming to achieve low cost energy storage applications by green technology, NiO nanoflakes have been synthesized using simple wet chemical route. Variation of calcination temperature is employed to pierce nanoholes within the nanoflakes to obtain higher effective surface area. All the samples are characterized by X-ray diffraction for phase related information. Samples are investigated via field emission scanning electron microscopy and high resolution transmission electron microscopy for morphological features whereas compositional analysis has been carried out using energy dispersive X-ray studies. Electrochemical performances of the as-prepared samples are investigated in detail to predict the potential application of this system in energy storage devices. It is observed that pore diameter and density may be enhanced with increment in calcination temperature. NiO nanowalls with the highest effective surface area (83.940 m(2)/g) synthesized at 900 degrees C exhibited a specific capacitance as high as 738 F/g (scan rate 2 mV/s) which is 82% greater than the less porous NiO sample, calcined at 500 degrees C (406 F/g). This high value of capacitance is correlated with nanohole dimension within nanoflakes and employing software based image analysis. This work, therefore, indicates a doorway for cost effective high performance energy storage application using morphologically modified metal oxide nanoflakes.