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Oxygen-Isotope Exchange between CO2 and Solid Ti18O2

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journal contribution
posted on 09.06.2011, 00:00 by Svatopluk Civiš, Martin Ferus, Pavel Kubát, Markéta Zukalová, Ladislav Kavan
The light–induced oxygen-isotope exchange between gaseous CO2 and solid Ti18O2 (anatase) and the spontaneous thermal isotope exchange that takes place between the vacuum-calcined solid Ti18O2 and CO2 were studied by gas-phase high-resolution Fourier transform infrared absorption spectroscopy over a period of several days. The absorption ro-vibrational spectra of all the measured carbon dioxide isotopologues were assigned and served as the quantification of the time-dependent isotope exchange between the oxygen atoms from the Ti18O2 solid and the oxygen related to the gaseous CO2. The C18O2 was formed as the dominating final product with a minor content of C16O18O. The rate of oxygen-isotope exchange is highly sensitive to the conditions of the titania pretreatment; vacuum-annealed Ti18O2 at 450 °C exhibited a very high spontaneous oxygen exchange activity with gaseous C16O2. A mechanism for the 18O/16O exchange process is discussed at the molecular level. The photocatalytic formation of methane, acetylene, and C16O released from the Ti18O2 surface was observed after irradiation by an excimer laser.