Hierarchical porous activated carbon produced from spinach leaves as an electrode material for an electric double layer capacitor

Hierarchical porous activated carbon (AC) was obtained by the carbonization of dried spinach leaves followed by activation with KOH. The product was characterized by nitrogen adsorption, FT-IR, FE-SEM and electrochemical tests. The AC has a dominant number of micropores, a medium number of mesopores and a few macropores with a specific surface area up to 2616 m(2)/g and a large number of oxygen-containing functional groups. The AC electrode exhibits a good double-layer capacitive behavior with a specific capacitance of 238 F/g in a 2 mol/L KOH electrolyte. A supercapacitor made of the AC has a high energy density of 10.1 Wh/Kg at a current density of 0.5 A/g and an excellent cyclic stability for 2000 cycles over a potential range from 0 to 1.2V.