Molecular and dissociative adsorption of methanol at various sites on the stoichiometric CeO2(111) surface
have been studied using density functional theory periodic calculations. At 0.25 monolayer (ML) coverage,
the dissociative adsorption with an adsorption energy of 0.55 eV is slightly favored. The most stable state is
the dissociative adsorption of methanol via C-H bond breaking, forming a coadsorbed hydroxymethyl group
and hydrogen adatom on two separate O3C surface sites. The strongest molecular adsorption occurs through
an O-Ce7subC connection with an adsorption energy of 0.48 eV. At methanol coverage of 0.5 ML, the dissociative
adsorption and the molecular adsorption became competitive. The adsorption energy per methanol molecule
for both adsorption modes falls into a narrow range of 0.46-0.55 eV. As methanol coverage increases beyond
0.5 ML, the molecular adsorption becomes more energetically favorable than the dissociative adsorption
because of the attractive hydrogen bonding between coadsorbed methanol molecules. At full monolayer, the
adsorption energy of molecular adsorption is 0.40 eV per molecule while the adsorption energy for total
dissociative adsorption of methanol is only 0.17 eV. The results at different methanol coverages indicate that
methanol can adsorb on a defect-free CeO2(111) surface, which are also consistent with experimental
observations. This research was performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory, which is a U.S. Department of Energy national scientific user facility located at Pacific Northwest National Laboratory (PNNL) in Richland, Washington. Computing time was made available under a Computational Grand Challenge “Computational Catalysis”. This work also financially supported by the Laboratory Directed Research and Development project of PNNL.
Revised: April 7, 2011 |
Published: July 19, 2007
Citation
Mei D., N.A. Deskins, M. Dupuis, and Q. Ge. 2007.Methanol adsorption on the clean CeO2(111) surface: A density functional theory study.Journal of Physical Chemistry C 111, no. 28:10514-10522.PNNL-SA-54165.