Investigation of Photostimulated Oxygen Isotope Exchange on TiO2 Degussa P25 Surface upon UV–Vis Irradiation

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Abstract

The interaction of oxygen molecules with TiO2 (Degussa P25) surface under UV (λ = 365 nm) and vis (λ = 436 nm) irradiation at T = 293 K was investigated by means of mass-spectrometry and thermo-programmed desorption (TPD) spectroscopy. Oxygen chemisorbed on reduced TiO2 surface consists of molecular species O2– and atomic ones. The adsorbed O2 species which are stable at 293 K are not observed on oxidized TiO2. The UV or vis irradiation in 18O enriched oxygen induces an intensive photostimulated oxygen isotope equilibration (POIEq) and exchange (POIEx) via a weakly bonded intermediate O3– due to the interaction of 18O2 with a hole center Os– (which is an exchangeable anion Os2– that captured a photogenerated hole h+). The number of surface exchangeable oxygen anions is 2 × 1011 cm–2 for oxidized TiO2 and 108 cm–2 for reduced TiO2. There is a reason to consider the observed POIEq as a multiple interaction of Os– with 18O2 molecules (in fact by means of heteroexchange). Thus, the obtained POIEq rate corresponds
Original languageEnglish
Pages (from-to)23332–23341
JournalJournal of Physical Chemistry C
Volume116
Issue number44
DOIs
Publication statusPublished - 2012

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