AVS 52nd International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM5
Rh-promoted Decomposition of Methanol Adsorbed on Cerium Oxide Thin Films

Wednesday, November 2, 2005, 9:40 am, Room 203

Session: Reactions on Metals & Oxides
Presenter: J. Zhou, Oak Ridge National Laboratory
Authors: J. Zhou, Oak Ridge National Laboratory
D.R. Mullins, Oak Ridge National Laboratory
Correspondent: Click to Email
Metal nanoparticles supported on single crystal oxides are important model systems for industrial catalysts. Research has found that the oxide substrates can greatly influence the catalytic activity of metal particles supported on them. In our study we have found that the reverse may also be true, i.e. that Rh nanoparticles may influence the thermal decomposition of methanol adsorbed on the oxide. All of the experiments were performed under UHV conditions by temperature programmed desorption (TPD) and synchrotron soft X-ray photoelectron spectroscopy (SXPS). Methanol decomposition was first carried out on the substrate ceria films to differentiate its chemistry from that when Rh is present. SXPS indicates that methanol deprotonates to form methoxy as the only intermediate on the ceria surface. On fully oxidized ceria, chemisorbed methoxy produced methanol and formaldehyde at about 560 K. However, on reduced ceria films methoxy decomposed further to produce primarily CO and H@sub 2@. When Rh nanoparticles were added to the ceria films, methoxy decomposed to CO and H@sub 2@ regardless of the ceria oxidation state and formaldehyde formation was suppressed. The desorption temperatures and intensities of CO and H@sub 2@ were found to be dependent on the reduction of the ceria films. These results indicate that the Rh promotes the decomposition of methanol adsorbed on the ceria and that decomposition may be influenced by the diffusion of methoxy intermediates across the oxide to the metal particles. Research sponsored by the U.S. Department of Energy, under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UT-Battelle, LLC.