Facile Preparation of Microporous Carbons with High Specific Capacitance from Coal Tar Pitch for Supercapacitors

Abstract

Microporous carbons (MCs) for supercapacitors were prepared from coal tar pitch (CTP) with potassium hydroxide (KOH) as activating agent at different KOH/CTP mass ratio by different heating modes. The results show that the specific surface area (SBET), micropore surface area (Smic), total pore volume (Vt) and micropore volume ((Vmic) of MCs made by microwave heating at 30 min heating time increases with the KOH/CTP mass ratio, respectively. At 14/7 of the KOH/CTP mass ratio, the SBET of MCs made by microwave heating at 30 min heating time reaches 1786 m2/g while that of MCs made by conventional heating at 180 min heating time is 1769 m2/g. The specific capacitance and energy density of the former reaches 269 F/g and 9.2 Wh/kg in 6 M KOH aqueous electrolyte while that of the latter is up to 307 F/g and 10.5 Wh/kg, respectively. And yet, the former brings bigger MC yield and bigger retention of energy density. The effects of the pore size distribution and pore volume on the specific capacitance and energy density of MC samples with the similar SBET by different heating modes are addressed in this paper.