Platinum films of 1 nm thickness were deposited by electron beam evaporation onto 100 nm thick titanium oxide films (TiOx) with variable oxygen vacancy concentrations and fluorine (F) doping. Methanol oxidation on the platinum films produced formaldehyde, methyl formate, and carbon dioxide. F-doped samples demonstrated significantly higher activity for methanol oxidation when the TiOx was stoichiometric (TiO 2), but lower activity when it was nonstoichiometric (TiO 1.7 and TiO1.9). These results correlate with the chemical behavior of the same types of catalysts in CO oxidation. Fluorine doping of stoichiometric TiO2 also increased selectivity toward partial oxidation of methanol to formaldehyde and methyl formate, but had an opposite effect in the case of nonstoichiometric TiOx. Introduction of oxygen vacancies and fluorine doping both increased the conductivity of the TiO x film. For oxygen vacancies, this occurred by the formation of a conduction channel in the band gap, whereas in the case of fluorine doping, F acted as an n-type donor, forming a conduction channel at the bottom of the conduction band, about 0.5-1.0 eV higher in energy. The higher energy electrons in F-doped stoichiometric TiOx led to higher turnover rates and increased selectivity toward partial oxidation of methanol. This correlation between electronic structure and turnover rate and selectivity indicates that the ability of the support to transfer charges to surface species controls in part the activity and selectivity of the reaction. © 2011 American Chemical Society.
|Original language||English (US)|
|Number of pages||5|
|Journal||The Journal of Physical Chemistry C|
|State||Published - Oct 28 2011|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Deposition and processing of titanium oxide films was performed at the Marvell Nanolab, University of California, Berkeley (UCB). X-ray photoelectron spectroscopy and scattering electron microscopy were carried out at the Molecular Foundry, Lawrence Berkeley National Laboratory. This work was funded by the Helios Solar Energy Research Center, the Chemical Sciences Division supported by the Director, Office of Science, Office of Basic Energy Sciences, U.S. Department of Energy, under Contract No. DE-AC02-05CH11231, and the UCB-KAUST Academic Excellence Alliance (AEA) Program.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.