Resolving the Effects of Surface Area and Porosity on the Capacitance of Activated Carbon

Abstract

One strategy to improve the energy density of electrochemical double-layer capacitors is to maximize the capacitance per unit surface area. However, due to the intercoupled relationship between surface area and pore size distribution, the effect of pore size on capacitance remains unclear. In this study, two samples prepared from the same raw material, with similar specific surface areas and chemical compositions, but different pore size distributions are compared in order to investigate the effects of pore size on capacitance. The results demonstrate that in the microporous sample, the SSA-normalized capacitance is 15.1 µF cm-2, while the mesoporous sample has an SSA-normalized capacitance of 13.2 µF cm-2 for all charging rates. However, when normalized to mass, the enhanced micropore capacitance may be masked due to variations in a sample’s bulk density. Therefore, these results demonstrate in broad pore size distribution activated carbon samples, the SSA-normalized capacitance is enhanced in microporous materials.