Mesostructured silica–carbon composites synthesized by employing surfactants as carbon source

Abstract

A general synthetic route for the fabrication of carbon–silica composites with a carbon layer coating the mesopores of the mesostructured silica is presented. The carbon layer is produced by carbonizing the surfactant employed as structure-directing agent in the synthesis of the mesostructured silica materials (MSM). The synthesis of this kind of composites is based on using sulphuric acid to generate a carbon residue from the surfactant molecules confined within the mesopores of the silica. The action of the sulphuric acid takes place via dehydration and sulphonation reactions, which promote the formation of aromatic structures and favour cross-linking processes. In order to illustrate this synthetic strategy we selected three mesostructured silica materials prepared with the aid of two types of surfactants: (i) oxygen-containing non-ionic triblock PEO-EO-PEO copolymer (Pluronic P-123) used for the synthesis of SBA-15 and KIT-6 and (ii) an alkyl ionic surfactant CTAB (cetyltrimethylammonium bromide) used to synthesize MCM-41. The silica–carbon composites prepared have high BET surface areas, large pore volumes and an ordered porosity made up of uniform mesopores.