Journal Article

V2O5/TiO2 Catalytic Xerogels Raman and EPR Studies

Rodella, Cristiane B., Magon, Claudio J., Saeki, Margarida J., Donoso, Jose P., Aegerter, Michel A., Sargentelli, Vagner, Nunes, Luis A.O., Franco, Roberto W.A., Florentino, Ariovaldo O.

2002

Overview

Raman spectroscopy and Electron Paramagnetic Resonance (EPR) studies were performed on a series of V2O5/TiO2 catalysts prepared by a modified sol-gel method in order to identify the vanadium species. Two species of surface vanadium were identified by Raman measurements, monomeric vanadyls and polymeric vanadates. Monomeric vanadyls are characterized by a narrow Raman band at 1030 cm−1 and polymeric vanadates by two broad bands in the region from 900 to 960 cm−1 and 770 to 850 cm−1. The Raman spectra do not exhibit characteristic peaks of crystalline V2O5. These results are in agreement with those of X-ray Diffractometry (XRD) and Fourier Transform Infrared (FT-IR) previously reported (C.B. Rodella et al., J. Sol-Gel Sci. Techn., submitted). At least three families of V4+ ions were identified by EPR investigations. The analysis of the EPR spectra suggests that isolated V4+ ions are located in sites with octahedral symmetry substituting for Ti4+ ions in the rutile structure. Magnetically interacting V4+ ions are also present as pairs or clusters giving rise to a broad and structureless EPR line. At higher concentration of V2O5, a partial oxidation of V4+ to V5+ is apparent from the EPR results.

• Publisher: Springer Nature B.V
• Subject: Catalysis / Electron paramagnetic resonance / Fourier transforms / Oxidation / Raman spectra / Raman spectroscopy / Sol-gel processes / Spectrum analysis / Titanium dioxide / Vanadates / Vanadium pentoxide / Vanadium pentoxide-Titanium dioxide / Xerogels