Synthesis and characterisation of xTiO2·(1−x)SiO2–carbon composites Original Research Article

A series of xTiO2·(1−x)SiO2–carbon xerogels (0.0≤x≤1.0) was obtained by co-polymerisation of resorcinol, formaldehyde, tetrabutyl orthotitanate and tetraethoxysilane. A blank without inorganic phase was also synthesized. The xerogels were pyrolysed at 1000 °C in nitrogen to obtain the composites. The samples were characterised by thermal analysis, gas physisorption, mercury porosimetry, X-ray diffraction, and titration with n-butylamine. The heat treatment of the xerogels caused the removal of moisture and organic precursors and the carbonisation of material. The presence of inorganic phase affected the thermal behaviour of the xerogel. The xerogels and composites were essentially macroporous solids. The pyrolysis of the xerogels gave rise to the creation of microporosity. Mesoporosity was usually little developed in the xerogels and composites. No crystalline phase was detected for the composites with 0.0≤x≤0.4, this indicating a good dispersion of the inorganic phase into the carbonaceous matrix. For x>0.4, however, anatase was observed. The surface acidity increased for the composites as compared to the blank. The acid strength was higher and the distribution of surface acidity was wider for the composites with a high titania content, whereas surface acid sites were weaker for the sample containing only this metal oxide as inorganic phase.