Multimodal porous carbon as a highly efficient electrode material in an electric double layer capacitor

A simple sol-gel synthesis strategy is developed to fabricate multimodal porous carbon (MPC) with hierarchical nanoarchitectures, in which monodisperse polystyrene sulfonate (PSS) spheres self-assemble themselves into an ordered lattice while the meso-sized silica particles generated in situ through base-catalyzed hydrolysis of tetraethyl orthosilicate aggregate closely at the interstices between the PSS spheres. Removal of the PSS lattice by calcination leaves a three-dimensional interconnected ordered macroporous structure, the walls of which are composed of a templated aggregate of the small silica particles, leading to a bimodal porous silica (BPS) template with open mesopores at the interstices between the small silica particles. This synthesis route allows one to readily fabricate BPS with a tailored three-dimensional ordered nanostructure, which can be further converted to MPC through the inverse replication. The MPC not only possesses ultrahigh surface area (i.e., 2220 m²/g), but also a unique hierarchical porosities composed of macro-, meso-, and micropores, which enable MPC to store and release large electrical charges rapidly whether at a low-mid or high rate. The well-developed 3D interconnected ordered macropore framework with open mesopores embedded in the macropore walls favors fast mass transport at high charge/discharge rates, providing better electric double layer capacitor performance. Compared with commonly used electrode material carbon black Pearls 2000 and other nanostructured carbons such as CMK-1 and CMK-3, the MPC has demonstrated much higher specific capacitance and energy.