The supercapacitor performance of hierarchical porous activated carbon electrodes synthesised from demineralised (waste) cumin plant by microwave pretreatment

Activated carbon (AC) was prepared from waste cumin utilising the chemical activation method. The cumin was separately washed with HCl and HF to remove minerals. The surface areas of AC of the acid washed samples (AC-HCl, AC-HF) were 1468 and 1472 m2/g, compared with 1361 m2/g for AC obtained directly from the precursor. Washing with the acids improved the supercapacitor performance through a significant decrease in the internal resistance of electrodes. The specific capacitances of electrodes using ACs prepared from acid washed samples (HCl and HF) were 127F/g and 155F/g at current density of 1.5 mA/cm2, compared with 117 F/g from the unwashed precursor.