XAFS study on the local structure of Ti in amorphous mesoporous titania

We applied XAFS spectroscopies to investigate the local structure of Ti in mesoporous titania synthesized with a primary amine template, which has an extremely large surface area (>1200 m2 g−1) and an amorphous nature, because the atomic structure was expected to differ in many points from that in all the other known titanium oxides. The coexistence of 5- and 6-fold coordinations of Ti is demonstrated by deconvoluting the pre-edge peaks of the Ti K edge XANES. Their populations are evaluated as 39% and 61%, respectively. The number of 5-fold Ti is decreased by a calcination at 673 K, accompanied by a considerable decrease of the BET surface area. The anharmonic pair distribution function is used for the analysis of EXAFS from the Ti–O bond in order to calculate reliable structural parameters. Template extraction considerably increases the Debye–Waller factor, suggesting that the micelles filling the pores suppress large vibrations of the Ti–O bond in mesoporous titania.