Preparation of oxygen-rich hierarchical porous carbon for supercapacitors through the co-carbonization of pitch and biomass

Abstract

Oxygen-rich hierarchical porous carbons (PCs) were successfully prepared through the co-carbonization of mesophase pitch (MP) and biomass sawdust (BS), following KOH activation. The PCs possessed a high specific surface area and a considerable amount of oxygen functional groups on the surface due to BS containing hierarchical porous structures and an abundant of heteroatoms. Moreover, the PCs exhibited high graphitization degree due to MP with a great deal of polynuclear aromatic structural units for easily forming the graphitized structures. The results showed that the PC-5/5 obtained from the co-carbonization of MP and BS with weight ratio of 5/5 had a high oxygen functional groups (1.43 mmol/g C-OH, 0.65 mmol/g RO-C=O, 0.66 mmol/g O-C=O from Boehm titration results) and its surface area reached to 2361 m2/g. As an electrode material for supercapacitor, the prepared electrode from PC-5/5 exhibited a favorable specific capacitance of 324 F/g at a current density of 0.5 A/g in 6 mol/L KOH electrolyte. The electrode also demonstrated excellent rate ability with a retention rate of 75% when the current density increases from 0.5 to 5 A/g, and remained 95% of the capacitance at 5 A/g after 500 cycles. Therefore, the PCs obtained by co-carbonization of MP and BS have high potential as electrode materials. This route not only enhanced the benefit from biomass wastes, but also reduced the cost of producing electrode materials for supercapacitor.