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

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 m2 g−1, total pore volume of 1.34 cm3 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 1-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.

Graphical abstractCarbons spheres with high specific surface area (1006 m2 g−1) and bimodal pore size distribution (3.5 and 23.8 nm) were successfully prepared by suspension polymerization and steam activation using phenol–formaldehyde resins as a carbon precursor.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Suspension polymerization method for preparation of carbon spheres from phenol–formaldehyde resins. ► BET specific surface area of 1006 m2 g−1, mesoporous ratio of 81.3 and average pore size of 5.33 nm. ► Specific capacitance of 147 F g−1 in ionic liquid [EMIm]BF4.