A comprehensive study on KOH activation of ordered mesoporous carbons and their supercapacitor application

Abstract

Activation of ordered mesoporous carbon orientates the development and application of new carbonaceous supercapacitor materials with high energy density and power density. Ordered mesoporous carbons FDU-15 are synthesized in large scale via a soft template method through evaporation induced self-assembly of mesostructure on the sacrificed polyurethane foam. Common activating agent potassium hydroxide (KOH) is utilized to improve the surface area and tailor the pore texture of the ordered mesoporous carbon by adjusting KOH/carbon mass ratio as well as activation time. At low KOH/carbon ratio, the generated micropores increase in volume and either connect to other micropores or eventually become mesopores. At high KOH/carbon ratio, an excess amount of micropores would be generated. Meanwhile, the continuous shrinkage of carbon framework is carried through as prolonged time at high activation temperature. Competition between KOH etching and shrinkage of mesopores is existed during the activation. The latter obviously preponderates over the former at low KOH/carbon ratio, which is reversed at high KOH/carbon ratio. Thus, an optimized micro-mesostructure is achieved under certain activation conditions: maintained ordered mesostructure, suitable microporosity, high surface area (1410 m2 g−1) and large pore volume (0.73 cm3 g−1). The activated sample exhibits improved electrochemical behavior with a gravimetric capacitance of 200 F/g, excellent rate performance and good cycling stability with capacitance retention of ∼98% over 300 cycles.