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

• Vacuum calcinated Ti18O2, Ti17O2 show a spontaneous exchange activity with C16O2.
• The calcination in vacuum creates vacancies in the TiO2 surface layer.
• Bidentate carbonate complex C16,16,17/18O3 on Ti17/18O2 surface is formed.
• C16,17O2 and C16,18O2 are intermediate products.
• C17O2 and C18O2 are final products.

The main motivation for the synthesis of Ti18O2 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 Ti18,17O2/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 C16O2 and solid Ti18O2 or Ti17O2. 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 16O–C–16O isotopologue and the exponential increase of the 18O–C–18O isotopologue. The 18O–C–16O acts as an intermediate in the mixture and its concentration remains almost constant.

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