title: Effect of fluorination on the surface properties of titania P25 powder: an FTIR study.
abstract: A study was carried out on the consequences of the -OH(surf)/F(-) exchange occurring at the surface of TiO(2) P25 when suspended in HF/F(-) solutions. The maximum extent of fluorination was reached at pH 3.0, resulting in the fixation on the surface of ca. 2.5 F(-)/nm(2). The surface features of fluorinated samples under two selected conditions were investigated by IR spectroscopy, in comparison with pristine TiO(2). The collected data suggested that bridged -OH(surf), likely located on regular facets, was more resistant to exchange with F(-). Combined high resolution transmission electron microscopy (HRTEM), inductively coupled plasma mass spectrometry (ICP-MS) and IR measurements indicated that the fluorination performed in the adopted condition did not induce any etching of TiO(2) particles, and the -OH(surf)/F(-) exchange appeared reversible by treatment in concentrated basic solutions. Furthermore, fluorination resulted in an increase of the Lewis acid strength of surface Ti(4+) sites, which, as a consequence, retained adsorbed water molecules even after outgassing at 423 K. Such an effect involved the overwhelming majority of cations exposed on regular facets.
authors.affiliation: Department of Analytical Chemistry and NIS Center of Excellence, University of Torino, Via P. Giuria 5, Torino 10125, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Minella
authors.forename: Maria Giulia
authors.initials: MG
authors.lastname: Faga
authors.forename: Valter
authors.initials: V
authors.lastname: Maurino
authors.forename: Claudio
authors.initials: C
authors.lastname: Minero
authors.forename: Ezio
authors.initials: E
authors.lastname: Pelizzetti
authors.forename: Salvatore
authors.initials: S
authors.lastname: Coluccia
authors.forename: Gianmario
authors.initials: G
authors.lastname: Martra