Redox properties of titanium oxides on Pt3Ti
1995 (English)In: Journal of Physical Chemistry, ISSN 00223654 (ISSN), Vol. 99, no 34, 12892-12895 p.Article in journal (Refereed) Published
The morphology and electronic structure of surface-segregated titanium oxides on Pt3Ti(111) are presented. Core level photoemission spectra at grazing emission reveal two states of oxidation: a dominant and reducible four-valent oxide together with a small amount of a three-valent oxide is produced by oxidation in O2 at and below 400Â°C; an irreducible three-valent oxide by oxidation in O2 at and above 450Â°C. The ratio between the active four-valent and the inactive three-valent oxides decreases with increasing oxidation temperature. The probability for reduction by CO is almost unity for the Ti4+ oxide, and the conclusion must be that the four-valent oxide plays an active role for catalytic reactions. Scanning tunneling measurements relate these observations to changes in the dispersion and nucleation of the oxide overlayer. The four-valent oxide grows as islands with remaining areas open for CO adsorption while the three-valent oxide spreads on and blocks the crystal surface. Photoemission spectra relate these dispersion effects to an electronic interaction between the Ti3+ oxide and adjacent Pt atoms. The above observations are in accordance with the common picture of dispersion effects in titania-supported SMSI catalysts and prove that interfacial energies play a crucial role whether the dominant phase is metallic or an oxide. Â© 1995 American Chemical Society.
Place, publisher, year, edition, pages
1995. Vol. 99, no 34, 12892-12895 p.
Condensed Matter Physics
IdentifiersURN: urn:nbn:se:kth:diva-83031OAI: oai:DiVA.org:kth-83031DiVA: diva2:502767
Correspondence Address: Paul, J.; KTH/Royal Institute of Technology, Physics III, 100 44 Stockholm, Sweden NR 201408052012-02-142012-02-122012-02-14Bibliographically approved