title: On the Simple Complexity of Carbon Monoxide on Oxide Surfaces: Facet-Specific Donation and Backdonation Effects Revealed on TiO2 Anatase Nanoparticles.
abstract: Atomic-scale relationships between the structure of TiO2 surfaces and the physicochemical properties of surface sites, functional for titania-based applications, can be obtained from IR spectroscopy by using carbon monoxide (CO) as a molecular probe. In the literature, it is reported that strongly unsaturated cationic Ti sites (Lewis acid), which are important for reactivity, should cause a large upshift of the CO stretching frequency. By using IR spectroscopy of CO on TiO2 nanomaterials and theoretical analyses, here this model is challenged. It is shown that the stretching frequency of adsorbed CO results from a facet-dependent and synergic CO-surface donation (upshift) - surface-CO backdonation (downshift) mechanism. These results imply that the interaction of adsorbed molecules with the Ti centers is tuned by the surface oxygen atoms of the first coordination sphere, which play an active role as indirect electron density donors (Lewis base).
authors.affiliation: Department of Chemistry and NIS Centre, University of Turin, Via P. Giuria 7, 10125, Torino, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Deiana
authors.affiliation: Department of Science and High Technology, University of Insubria and INSTM, Via Valleggio 9, 22100, Como, Italy.
authors.forename: Ettore
authors.initials: E
authors.lastname: Fois
authors.affiliation: Department of Chemistry and NIS Centre, University of Turin, Via P. Giuria 7, 10125, Torino, Italy. gianmario.martra@unito.it.
authors.forename: Gianmario
authors.initials: G
authors.lastname: Martra
authors.affiliation: Solaronix SA, Rue de l'Ouriette 129, 1170, Aubonne, Switzerland.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Narbey
authors.affiliation: Department of Chemistry and NIS Centre, University of Turin, Via P. Giuria 7, 10125, Torino, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Pellegrino
authors.affiliation: Department of Science and High Technology, University of Insubria and INSTM, Via Valleggio 9, 22100, Como, Italy. gloria.tabacchi@uninsubria.it.
authors.forename: Gloria
authors.identifier: http://orcid.org/0000-0002-1988-6775
authors.initials: G
authors.lastname: Tabacchi
keywords: IR spectroscopy; density functional calculations; metal oxide nanoparticles; molecule-surface interactions; titanium dioxide