Mesoporous Silica-Carbon Composites with Enhanced Conductivity: Analysis of Powder and Thin Film Forms.

The resistivity of the silica SBA-15 type can be significantly improved by forming a thin layer of carbon on the pore surface. This is possible through the carbonization reaction of a surfactant used as a structure-directing agent in the synthesis of mesostructured silica materials. The synthesis of this type of silica-carbon composite (SBA-C) is based on the use of sulfuric acid to create a carbon layer from surfactant molecules encapsulated in silica mesopores. The action of sulfuric acid takes place through dehydration and sulfonation reactions, which promote the formation of aromatic structures and favor crosslinking processes. The same procedure was applied to prepare MTF-C composites based on mesostructured thin films (MTFs). Compared to pure silica materials, these silica-carbon composites exhibit reduced pore diameter and volume while maintaining morphology and structure. The pore structure characteristics were obtained by scanning and transmission electron microscopy, X-ray energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, thermogravimetry, and isothermal sorption analysis. The composite obtained after carbon layer formation exhibited enhanced conductivity in comparison to pure silica SBA-15. The resistivity of SBA-C composite material after annealing at 800 °C under a nitrogen atmosphere decreased to 1980 Ωcm in comparison with pure SBA-15.