Synthesis and characterization of nanocomposite NiO/activated charcoal electrodes for supercapacitor application

Nickel oxide (NiO) nanoparticles (NPs) were synthesized at room temperature using coprecipitation method and have been tested as electrode materials by forming composites with activated charcoal for their application in supercapacitor. To synthesize NiO NPs, nickel sulfate (NiSO4) and sodium hydroxide (NaOH) were used as initial precursors. The obtained NPs were calcined at 400, 500, and 600 °С for 3 h. Composites of NiO and commercially procured activated charcoal (AC) have been prepared in different weight ratios varying from 1:1 to 1:3. The nanocomposite has been characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). A symmetrical supercapacitor has been fabricated using different nanocomposites of NiO nanoparticle/activated charcoal (NiO/AC) with potassium hydroxide as electrolyte materials. The performance characteristics of fabricated supercapacitor have been characterized using a.c. impedance, cyclic voltammetry, and charge–discharge techniques. The optimized NiO/AC composition was observed at 1:1 weight ratio for NPs calcined at 400 °С. The maximum capacitance observed for the optimized composition is 233.3 mF cm−2, which is equivalent to single electrode specific capacitance of 84.8 F g−1. Cyclic stability of fabricated supercapacitor cell has been tested for 1100 cycles and was found to be almost stable after having initial increase of about 5.65% in the specific capacitance values.