Effect of the second heat treatment on the porosity and conductivity of a template-synthesized carbon material for use in supercapacitor electrodes

Due to low energy density of electric double layer capacitors (EDLCs) with carbon electrode materials, what researchers have consistently done in the course of history is to increase the accessible surface area and porosity content of the carbon structure. In addition, it was reported that chemical surface activating the carbon materials leads to the production of surface functional groups, which results in the introduction of Faradic properties and an increase in the capacitance of carbon materials. However, there are no studies on the relationship between porosity content (as well as surface activation) and conductivity, especially for template-synthesized carbon materials. In this work, we show that a second heat treatment on a synthetic carbon material reduces the surface area (and porosity) and removes the surface functional groups, however, the capacitance increases due to the increase in conductivity. In other words, this study seeks to show that activating the carbon surface and creating more porosity may destroy the crystalline structure of the carbon surface and it does not necessarily increase capacitance. Accordingly, the supercapacitors made of the as-prepared carbon (C7) and the carbon with a secondary heat-treatment at 1000 degrees C (C10) show the values of specific capacitance (CS) at 31.5 and 81.4 F/g at a current density of 0.2 A/g, respectively. In addition, the C10 shows about 2.7 times more energy density than the C7 with almost the same power density.

Automated summary

In the study of EDLCs, researchers have focused on increasing the accessible surface area and porosity content of carbon electrode materials to improve the energy density. This study discovered that a second heat treatment on synthetic carbon materials reduces surface area and porosity, removes surface functional groups, but increases capacitance due to increased conductivity. These findings suggest that activating the carbon surface and creating more porosity may not necessarily increase capacitance.