Tetraphenylborate-derived hierarchically porous carbons as efficient electrode materials for supercapacitors

Porous carbons have been prepared by a direct carbonization method, using sodium/potassium tetraphenylborate as carbon sources. It reveals that the carbonization temperature and tetraphenylborate species play crucial roles in determining the structures, including surface areas, pore volumes and pore size distributions. The carbon-K-900 sample has a high surface area 836 m(2) g(-1) and large total pore volume 0.86 cm(3) g(-1). The electrochemical performances have been extensively studied by a two-electrode system and a three-electrode system, using KOH and 1-ethyl-3-methylimidazolium tetrafluoroborate (abbr. [EMIm]BF4) as electrolyte, respectively. The carbon-K-900 sample displays specific capacitance of 281.0 F g(-1) at 1 A g(-1) in a three-electrode system, using KOH as electrolyte, whilst those of 208.4, and 295.6 F g(-1) at 1 A g(-1) can be achieved in a two-electrode system, using KOH and [EMIm]BF4 as electrolyte, respectively. The carbon-K-900 sample exhibits good rate capability and cycling durability. More importantly, we have intensively investigated the effect of operation temperature such as 25/50/80 degrees C upon the capacitive performance of the carbon-K-900 sample. It indicates that introducing ionic liquid into supercapacitor as electrolyte can greatly extend the operation temperature and higher operation temperature indeed favors for gaining better capacitive performance. (C) 2013 Elsevier B.V. All rights reserved.