Photostimulated oxygen isotope exchange between N18O and anatase TiO2 under light irradiation

It is known that an intense photoinduced oxygen isotope heteroexchange (POIEx) between N18O and TiO2 occurs via interaction of N18O with surface hole center Ocus−16, where Ocus−16 is coordinatively unsaturated surface oxygen captured a photogenerated hole. At the same time the mechanism of formation of N18O-Ocus−16 intermediate has not been investigated. Formation of the intermediate may occur via either a collision of the gaseous NO molecules with the Ocus−16 centers or a contact of weakly adsorbed NO species with the ones. The present work is devoted to the investigation of POIEx between N18O and TiO2 Hombifine N (anatase) at T = 293 K by means of kinetic mass-spectrometry and temperature-programmed desorption (TPD) spectroscopy. From the linear dependence of the POIEx rate on N18O pressure it was shown that the exchange occurs via the collision interaction of gaseous NO molecule with the surface active site Ocus−16. The activation energy (Ea = 0.221 ±0.003 eV) of oxygen exchange step N18O−Ocus−16→N16O−Ocus−18 was calculated basing on the dependence of the exchange rate on the temperature in the 150-300 K range.