Performance enhancement approach for supercapacitor by using mango kernels derived activated carbon electrode with p-hydroxyaniline based redox additive electrolyte

Mango kernel is utilized for the synthesis of activated carbon as an electrode material for supercapacitors application. The synthesized active material is characterized by using the X-ray diffraction, Raman spectroscopy, scanning electron microscopy and fourier transform infrared spectroscopy techniques that confirm its well porous structure in graphitic conducting phase. Electrochemical testing of this material as an electrode for supercapacitor is carried out in 1M sulphuric-acid and sulphuric-acid added p-hydroxyaniline (redox additive) electrolytes by using impedance spectroscopy, cyclic voltammetry and charge-discharge techniques. We find that the fabricated supercapacitor with sulphuric-acid exhibits specific capacitance of 157.5 F g(-1) and energy density of 11.8 Wh kg(-1) at a current density of 1 A g(-1), whereas by adding p-hydroxyaniline in sulphuric-acid, these values shows remarkable enhancement of 587.1 F g(-1) and 34.3 Wh kg(-1), respectively. The credit for remarkable enhancement is given to the hydroxyl and amine groups present in p-hydroxyaniline that initiates faradic redox reaction within the system and is also confirmed through the observed cyclic voltammetry pattern. Cyclic stability test shows 85.3% capacitance retention for almost 5000 cycles. Effect of temperature variation on the diffusion process, resistance and capacitance are also studied for the optimized cells.