The application of high-resolution IR spectroscopy and isotope labeling for detailed investigation of TiO2/gas interface reactions

The main motivation for the synthesis of (TiO2)-O-18 was the investigation of surface effects during titania/gas interaction. The interaction with carbon dioxide was investigated with the aim to explore oxygen isotope exchange at the (TiO2)-O-18,17/CO2 interface. For this purpose, high-resolution Fourier transform infrared spectroscopy of the gas phase was adopted. In the present study, we have explored the oxygen isotope exchange between gaseous (CO2)-O-16 and solid (TiO2)-O-18 or (TiO2)-O-17. The present measurement in dark mixtures has, as its primary goal, the determination of the time-scale of the spontaneous isotope exchange between carbon dioxide and solid TiO2. The profiles of the individual lines of selected isotopologues (isolated lines in the spectrum) were fitted and quantified. The quantification of the spectra was carried out on the basis of calibration measurements of the absorption spectra of individual isotopologues (reference gases) of carbon dioxide at different pressures. The concentrations of individual isotopologues determined from the intensity profiles of the individual rotation-vibration lines are characterized by the exponential decrease of the O-16-C-O-16 isotopologue and the exponential increase of the O-18-C-O-18 isotopologue. The O-18-C-O-16 acts as an intermediate in the mixture and its concentration remains almost constant. (C) 2013 Elsevier B.V. All rights reserved.