Influence of pore structure on electric double-layer capacitance of template mesoporous carbons

The behavior of two types of mesoporous carbons with different pore structures (i.e. unimodal and bimodal) as electrode material in an electrochemical double-layer capacitor has been analyzed. The carbon samples were prepared using mesostructured silica materials (MSM) as templating agents. The unimodal mesoporous carbon has a BET surface area of 1550 m2 g−1, and a pore volume of 1.03 cm3 g−1; the porosity is mainly made up of structural mesopores of ca. 3 nm that exhibit a narrow pore size distribution (PSD). The bimodal carbon shows larger surface area (1730 m2 g−1) and larger pore volume (1.50 cm3 g−1); the porosity is composed of two types of mesopores: structural (size around 3 nm) and complementary (size around 16 nm) mesopores. Both carbons show a disordered 3-D pore structure. Heat treatments at high temperatures (1000 °C) for long times (11 h) do not significantly change the pore structure with respect to the two synthesised carbons (800 °C). From the synthesized and heat-treated carbons, electrodes were processed as composites in which the carbons, polivinilidene fluoride (PVDF) and carbon black (CB) were the components. The effect of the heat treatment and relative CB content on specific capacitance, energy density and power density were studied. We found a specific capacitance of 200 F g−1 for low current density (1 mA cm−2) and 110 F g−1 for high current density (150 mA cm−2). Moreover, the curve of the specific capacitance versus current density shows three regimes, which are related to the three types of pore: micropores, structural mesopores and complementary mesopores. An energy density of 3 Wh kg−1 at a power density of 300 W kg−1 was obtained in some particular cases.