Synthesis of mesoporous carbons using a triblock copolymer containing sulfonic acid groups and their capacitance property

Abstract

Mesoporous carbon films and powders were synthesized by a soft-templating method using a triblock (poly(α-methylstyrene)-hydrogenated polybutadiene-poly(α-methylstyrene), PS-PB-PS) copolymer (S-BCP) as a template. In the triblock copolymer, the polystyrene blocks are functionalized with hydrophilic sulfonic groups. Therefore, they not only interact with hydrophilic carbon sources (resorcinol) but also act as an acid catalyst for polymerization of a resorcinol–formaldehyde composite. Spherical pores with 20 nm in size which are connected to each other were found in both the carbon film and powder products of the carbon (COU-4). The spherical pore structure of the mesoporous carbon can be explained by a surfactant packing parameter (g value). The hydrophilic tails of the triblock copolymer contain bulky phenyl groups and sulfonic acid groups in the PS blocks. Therefore, the structure of the RF–S-BCP composite becomes conic. After the KOH activation, the BET surface area of the mesoporous carbon powders was largely increased from 261 m² g⁻¹ to 1862 m² g⁻¹ and the micropore volume was increased from 0.04 cm³ g⁻¹ to 0.31 cm³ g⁻¹. The KOH activated carbon powder (K-COU-4) shows superior capacitance performance in aqueous electrolyte solutions over microporous carbon (K-AC) and the previously reported ordered mesoporous carbon (K-COU-2).