Preparation of mesoporous carbon spheres with a bimodal pore size distribution and its application for electrochemical double layer capacitors based on ionic liquid as the electrolyte

摘要

Mesoporous carbon spheres with a bimodal pore size distribution were prepared by suspension polymerization and steam activation method using phenol-formaldehyde resins as a carbon precursor. The as-prepared carbon spheres had a specific surface area of 1006 m~2 g~(-1) total pore volume of 1.34 cm~3 g~(-1), mesoporous ratio of 81.3% and average pore size of 5.33 nm. Moreover, the carbon material showed a bimodal pore size distribution (3.5 and 23.8 nm). We found a high specific capacitance of 147 F g~(-1) for the carbon spheres in ionic liquid l-ethyl-3-methylmidazolium tetrafluoroborate ([EMIm]BF4) at a current density of 2 mA cm~(-2) and small impedance at the interface of electrode/electrolyte. In addition, a specific energy of 20 Wh kg~(-1) at a specific power of 3100 W kg~(-1) was obtained in some particular cases.