Preparation of hollow submicrocapsules with a mesoporous carbon shell

Abstract

The preparation of carbon submicrocapsules with size up to 800nm and a mesoporous shell by hard silica templating is reported. Washing and template synthesis conditions were varied to promote porosity and avoid deformation of the microcapsules. The silica template synthesis conditions analyzed were: silica nucleus formation time (0.25–6h), octadecyltrimethoxysilane/tetraethylorthosilicate volume ratio for silica shell formation (0.2–0.6) and silica shell formation time (1–24h). The samples were characterized by 77K nitrogen adsorption/desorption, mercury porosimetry and electron microscopy. Under all the washing conditions tested the carbon submicrocapsules were deformed due to the large size of the hollow core and the thickness of the shell. Changes in the silica template synthesis conditions did not result in substantial improvement of the strength of the microcapsules. The synthesis of a silica template with a double shell allowed us to obtain thick shell carbon submicrocapsules without significant deflation and with higher porosity. The characterization of these microcapsules showed that they have a BET surface area of 1541m2/g and a pore size distribution with peaks centered at 0.75, 0.86, 1.0nm in the micropore range and 3.5nm in the mesopore range. The pore volume in the 2–80nm range was 1.7cm3/g.