Preparation of nitrogen-doped macro-/mesoporous carbon foams as electrode material for supercapacitors

An oil-in-water (O/W) emulsion system of Span 80-Tween 80/liquid paraffin/aqueous resorcinol-formaldehyde was manufactured. Nitrogen-doped macro-/mesoporous carbon foams (N-MMCFs) were prepared by the polymerization of this O/W emulsion, followed by carbonization and activation process. As-prepared N-MMCFs were characterized by scanning electron microscopy, infrared (IR) spectra, N-2 adsorption and desorption analysis, and electrochemical workstation. The results indicate that the N-MMCFs have main macropore of 0.2 mu m, mesopore of 2.6-4.0 nm and specific surface areas of 1205-1808 m(2) g(-1). The contact angle of N-MMCFs for water is about 37.5 degrees, obviously lower than that of MMCFs (72.9 degrees), which suggests that the surface wettability of N-MMCFs is greatly improved due to the incorporation of nitrogen into the carbon framework. Electrochemical measurements show that specific capacitance of a typical N-MMCF as electrode material in 6M KOH aqueous solution is as high as 198 Fg(-1) at a current density of 1.0A g(-1). Its specific capacitance can still remain 159 Fg(-1) at a high loading current density of 20.0 A g(-1) with the retention of 80.3%, which indicates that the typical N-MMCF as electrode material has a good rate capability. The high current charge and discharge capability offers the promising prospects for the application of N-MMCFs as electrode materials in supercapacitors which could meet the need of high power density. (C) 2012 Elsevier B.V. All rights reserved.