Effects of the Pore Structure of Commercial Activated Carbon on the Electrochemical Performance of Supercapacitors

• The effect of the pore structures on electrochemical performance of different commercially-available activated carbons (AC) was studied. • The presence of ultramicropores (that is, those pores with d <1 nm) are responsible for the capacitance characteristics of AC. • The high micropore volume enhanced the exchange and adsorption of ions on the carbon surface. • The suitable mesopore structure promoted the diffusion of the electrolyte. The performance of activated carbon (AC) can be improved by optimizing the pore structure and increasing the specific surface area. In the present work, seven commercial activated carbons having different pore structures were used to explore the effects of pore morphology on electrochemical characteristics. Nitrogen adsorption-desorption, X-ray diffraction, Raman spectroscopy and electrochemical analyses were used to assess these materials. Trials in aqueous 6 M KOH showed that an AC with a high proportion of ultramicropores (pores less than 1 nm in size) and a suitable mesopore structure provided more charge storage sites. These sites promoted the diffusion of the electrolyte, thereby reducing the internal resistance of the material. Specific capacitance values normalized by specific surface area demonstrated that ultramicropores also enhanced the capacitance values of AC-based electrodes. An optimized specimen having a high ultramicropore volume of 0.41 m 3 /g and a reasonable mesopore volume of 0.15 m 3 /g exhibited a specific capacitance of 283.90 F/g at a current density of 1 A/g together with an energy density of 8.47 Wh/kg. This AC also showed superior rate capability and excellent cycling stability with a capacitance retention of 97.16% after 5000 cycles. This study provides guidance that will be helpful in improving commercial AC materials with applications as electrodes in supercapacitors.