WOx-TiO2 catalysts with different W contents on titanium oxide nanofibers were prepared by impregnation of (NH4)2WO4 aqueous solution and annealed in air at 400 oC. X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and Raman spectroscopy were used for chemical and structural characterization. The results revealed that the support consisted of β-titanium oxide nanofibers with WOx species highly dispersed on the nanofibers saturating the surface at a concentration around 30 wt%. With an increase in the W concentration to 40 and 50 wt%, a crystalline WO3 phase segregates from the support, growing as large WO3 crystallites, whereas the support remains homogeneously decorated by WOx nanoclusters with dimensions around 1.0 nm. The W atoms remained octahedrally coordinated with a W = O Raman vibrating band at 974 cm−1.

Keywords: Tungsten Oxide, TiO2, Catalyst, Nanofibers, HRTEM, HAADF-STEM, Raman Spectroscopy.