Influence of nitric acid acitivation on structure and capacitive performances of ordered mesoporous carbon

Abstract

Ordered mesoporous carbon CMK-3 was successfully prepared by a hard template nanocasting method followed by carbonization at temperatures from 700 to 900°C. The values of specific surface area, pore diameter and pore volume were found to increase with the rise of carbonization temperatures. After chemical activation by 6M HNO3, the specific surface areas decreased significantly, but the specific capacitances increased remarkably in both alkaline (3M KOH) and neutral (0.5M Na2SO4) electrolytes. Analysis of the surface structure and composition showed that the chemical activation introduced oxygen-containing functional groups on carbon surface, which are responsible for the enhancement of supercapacitive performances revealed by electrochemical tests. The best achieved specific capacitance is 182.1F/g in 0.5M Na2SO4, and 223.5F/g in 3M KOH, both at the current density of 0.5A/g. The specific capacitance retentions after 500 cycles are 95.6% and 86.3% in 0.5M Na2SO4 and 3M KOH, respectively. The higher specific capacitance in KOH electrolyte is due to the lower faradic charge transfer resistance and better electrochemical surface area utilization than in Na2SO4 electrolyte.