Photostimulated Oxygen Isotope Exchange Between (No)-O-18 And Anatase Tio2 Under Light Irradiation

It is known that an intense photoinduced oxygen isotope heteroexchange (POIEx) between (NO)-O-18 and TiO2 occurs via interaction of (NO)-O-18 with surface hole center O-16(cus)-, where O-16(cus)-, is coordinatively unsaturated surface oxygen captured a photogenerated hole. At the same time the mechanism of formation of (NO)-O-18-O-16(cus)- intermediate has not been investigated. Formation of the intermediate may occur via either a collision of the gaseous NO molecules with the O-16(cus)- centers or a contact of weakly adsorbed NO species with the ones. The present work is devoted to the investigation of POIEx between (NO)-O-18 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 (NO)-O-18 pressure it was shown that the exchange occurs via the collision interaction of gaseous NO molecule with the surface active site O-16(cus)-. The activation energy (E-a = 0.221 +/- 0.003 eV) of oxygen exchange step (NO)-O-18 - O-16(cus)- -> N16O - O-18(cus)- was calculated basing on the dependence of the exchange rate on the temperature in the 150-300 K range. (C) 2016 Elsevier B.V. All rights reserved.