Low-Cost Synthetic Route to Mesoporous Carbons with Narrow Pore Size Distributions and Tunable Porosity through Silica Xerogel Templates

Abstract

Silica xerogels synthesized by the sol−gel process were used as templates to fabricate mesoporous carbons. The silica was prepared in a two-step process, under acid pH conditions, at a high H2O/Si molar ratio of 194 and at different HCl/Si molar ratios. Two sources were used as silica precursors: tetraethoxysilane (TEOS) and sodium silicate. The resulting silica xerogels have surface areas of >500 m2·g-1, pore volumes of >0.4 cm3·g-1, and a tunable mesopore size of between 2 and 10 nm, depending on the HCl/Si molar ratio. The mesoporous carbons obtained as inverse replicas of silica xerogel templates have large pore volumes (in the 1.5−2.1 cm3·g-1 range), large BET surface areas of up to 2200 m2·g-1, and narrow pore size distributions (PSD) in the mesopore range. The mesopore size of the carbons can be tuned between 3 and 4.5 nm depending on the type of silica xerogel selected as template. Carbons prepared in this way have structural characteristics comparable to those of mesoporous carbons made by templ...