Carbon electrode materials for supercapacitors obtained by co-carbonization of coal-tar pitch and sawdust

High-surface area-activated carbons (ACs) are successfully prepared by coal-tar pitch (CTP)/sawdust (SD) co-carbonization followed by simple KOH activation. The ACs inherit the tubular morphology of the biomass and possess a hierarchical porous structure, a high specific surface area of 2224 m(2)/g, and a considerable amount of oxygen-containing species on the surface. The AC obtained from the co-carbonization of 67 % CTP and 33 % SD has a 25 wt% higher oxygen content than the AC (0.17 wt%) from 100 % CTP, and has a 27.50 wt% higher carbon yield than the AC (14.42 wt%) from SD. As an electrode material for supercapacitors, the prepared electrode from 67 % CTP and 33 % SD exhibits a favorable specific capacitance of 251 F/g at a current density of 0.5 A/g in 6 mol/L KOH electrolyte. The electrode also demonstrates excellent cycling stability with a retention rate of 93 % over 7000 cycles at 2 A/g and a favorable rate capability with a retention rate of 74 % when the current density increases from 0.5 to 5 A/g. Therefore, the ACs obtained by co-carbonizing CTP and SD have high potential as electrode materials. This route not only enhances the benefit from agricultural wastes, but also reduces the cost of producing electrode materials for supercapacitors.