Publications in Scientific Journals:
M. Setvin, X. Shi, J. Hulva, T. Simschitz, G. Parkinson, M. Schmid, C. Di Valentin, A. Selloni, U. Diebold:
"Methanol on Anatase TiO2 (101): Mechanistic Insights into Photocatalysis";
The photoactivity of methanol adsorbed on the anatase TiO2
(101) surface was studied by a combination of scanning tunneling microscopy
(STM), temperature-programmed desorption (TPD), X-ray photoemission
spectroscopy (XPS), and density functional theory (DFT) calculations. Isolated
methanol molecules adsorbed at the anatase (101) surface show a negligible
photoactivity. Two ways of methanol activation were found. First, methoxy groups
formed by reaction of methanol with coadsorbed O2 molecules or terminal OH
groups are photoactive, and they turn into formaldehyde upon UV illumination.
The methoxy species show an unusual C 1s core-level shift of 1.4 eV compared to
methanol; their chemical assignment was verified by DFT calculations with
inclusion of final-state effects. The second way of methanol activation opens at methanol coverages above 0.5 monolayer (ML),
and methyl formate is produced in this reaction pathway. The adsorption of methanol in the coverage regime from 0 to 2 ML is
described in detail; it is key for understanding the photocatalytic behavior at high coverages. There, a hydrogen-bonding network
is established in the adsorbed methanol layer, and consequently, methanol dissociation becomes energetically more favorable.
DFT calculations show that dissociation of the methanol molecule is always the key requirement for hole transfer from the
substrate to the adsorbed methanol. We show that the hydrogen-bonding network established in the methanol layer dramatically
changes the kinetics of proton transfer during the photoreaction.
anatase, TiO2, methanol, photocatalysis, STM, DFT, XPS, TPD
Created from the Publication Database of the Vienna University of Technology.