Direct synthesis of oxygen-enriched 3D porous carbons via NaCl template derived from oxidized coal tar pitch for excellent cycling stability electric double layer capacitor

A novel type of oxygen-enriched three-dimensional porous carbons (3DPCs) is prepared using coal tar pitch (CTP) oxidized by KMnO4 as raw material and NaCl as a green template. Oxygen-containing functional groups are grafted on the edge of polycyclic aromatic hydrocarbons (PAHs) through oxidative modification, which avoids excessive accumulation of PAHs and successfully achieves oxygen doping to provide additional pseudo-capacitance. The existence of NaCl supports the formation of 3D structure and improves the diffusion/transport capacity of electrolyte ions. The as-prepared 3DPCs show interconnected 3D structure with large effective specific surface area (3067 m2 g−1) and high oxygen content (up to 9.8%). In addition, the electric double layer capacitor assembled by 3DPC-3 exhibits the largest specific capacitance (306 F g−1 at 0.5 A g−1) and superior cycling stability (specific capacitance retention of 99.7% after 10000 cycles) in 6 M KOH electrolyte. Meanwhile, high energy density (36.8 Wh kg−1) is obtained when it is applied to EMIMBF4 electrolyte. Overall, this work provides an effective way for the synthesis of 3DPCs and can be also conducive to the development of the high value-added CTP-based carbon material industry.