Carbon Microspheres with Tailored Texture and Surface Chemistry As Electrode Materials for Supercapacitors

Abstract

N-doped carbon microspheres have been prepared by controlled sol-gel polymerization of resorcinol and formaldehyde. The pristine carbon microspheres were activated with CO 2 and the sample activated for 90 min possessed the highest BET area, 1520 m 2 g-1. After N-doping with urea, a 4 wt % N content was reached and the microspheres still had a high BET area of 1350 m 2 g-1 with a porosity composed mostly of micropores (<2 nm) and a high packing density of 0.87 g cm-3. These N-doped microspheres were used as electrodes of supercapacitors, which showed a remarkable specific capacitance of 235 F g-1 at a current density of 125 mAg-1 in 1 mol L-1 H2SO4 as electrolyte. This was due to pseudo-capacitance reactions produced by the presence of N-groups. Furthermore, these electrodes were able to retain 56.5 % of the capacitance using a current density of 7 A g-1 as well as to retain 100% of the capacitance after 12000 galvanostatic charge-discharge cycles at 1 A g-1 .