Synthesis of mesoporous carbons for supercapacitors from coal tar pitch by coupling microwave-assisted KOH activation with a MgO template

Abstract

Mesoporous carbons (MCs) for supercapacitors were prepared from coal tar pitch by a microwave-assisted one-step process coupling the potassium hydroxide (KOH) activation and magnesium oxide (MgO) template. MCs were characterized by scanning electron microscope and X-ray diffraction. The results show that the specific surface area (SBET), micropore volume and specific capacitance of MCs made by microwave heating as well as the energy density of MC capacitors pass through a maximum with increasing mass of MgO and the relative mass ratio of KOH/pitch. The SBET of MCs varies from 1003 to 1394m2/g. The SBET and total pore volume of MC and microporous carbon made by microwave heating are bigger than that made by conventional heating. Under optimum conditions with the masses of coal tar pitch, MgO, KOH at 9g, 12g, 6g, and the microwave power at 600W, MC (MC9-12-6) made at 30min heating time shows a high specific capacitance of 224F/g in 6M KOH aqueous electrolyte after 1000 cycles. The results have shown that microwave-assisted rapid KOH activation coupled with the MgO template is an efficient one-step approach to the preparation of low cost yet high performance MCs for supercapacitors.