Quantitative analysis of Ti-O-Si and Ti-O-Ti bonds in Ti-Si binary oxides by the linear combination of XANES

Abstract

X-ray absorption near edge structure (XANES) of Ti K-edge of Ti-Si mixed oxides and titania supported on silica with various Ti contents was studied to investigate the fractions of Ti-O-Si and Ti-O-Ti bonds quantitatively by fitting the preedge of Ti K-edge with the linear combination of two reference XANES spectra. In mixed oxides, the fraction of Ti-O-Ti was increased up to 0.55 when Ti/Si was varied from 0.04 to 0.5. The greatest change of each fraction occurred around 0.15-0.2 of Ti/Si, which was coincident with the formation of anatase titania as observed by XRD. For titania supported on silica with a surface area of 300 m(2) g(-1), the preedge fitting results combined with XRD and XPS indicated that monolayer coverage was reached around 7-10 wt % Ti loading where the amount of Ti in Ti-O-Si was saturated to 0.56 mmol-Ti/g-material. This work demonstrated the possibility of the quantification of Ti-O-Si and Ti-O-Ti bonds in Ti-Si binary oxides by using the linear combination of reference XANES spectra.