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

N-doped carbon microspheres were prepared by controlled sol-gel polymerization of resorcinol and formaldehyde. The pristine carbon microspheres were activated with CO2, and the sample activated for 90 min possessed the highest BET surface 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 125 mAg(-1) in 1 M H2SO4 as electrolyte. This was due to pseudocapacitance reactions produced by the presence of N-groups. Furthermore, these electrodes were able to retain 56.5% of the capacitance at current density of 7 A g(-1) and to retain 100% of the capacitance after 12000 galvanostatic charge-discharge cycles at 1 A g(-1).

Automated summary

N-doped carbon microspheres with high BET surface area and specific capacitance were prepared by N-doping with urea, showing significant pseudocapacitance reactions. These electrodes exhibited good retention of capacitance even after cycling for 12000 charge-discharge cycles.