Preparation and XAFS spectroscopic characterization of mesoporous titania with surface area more than 1200 m~2/g

摘要

Mesoporous titania with BET surface area over 1200 m~2·g~(-1) was synthesized by primary amine templating followed by acidic extraction of the template. Dodecyl-, tetradecyl- and hexadecylamines gave intense single XRD patterns at 2θ= 2-3°without reflections for higher indices, suggesting the wormhole structure. The pore size changed according to the length of template molecule. The chemical vapour deposition (CVD) of titanium tetraisopropoxide followed by its decomposition with water vapour was carried out in template-extracted titania and the improvement in thermal stability was evaluated by the decrease in S_(BET) by the calcination. The local structure of Ti was investigated by X-ray absorption spectroscopies. The K-edge EXAFS spectra measured at various temperatures demonstrated that large atomic vibrations in mesoporous titania are considerably suppressed in the powder before removing template. The preedge peaks in the XANES region showed the coexistence of 5- and 6-coordinated Ti. The ratio of intensity of these peaks was calculated to compare the degree of framework destruction.