AVS 53rd International Symposium
    Surface Science Monday Sessions
       Session SS1-MoM

Paper SS1-MoM12
Comparison of the Stability of Small Molecules On Rh(111) and Rh(553)

Monday, November 13, 2006, 11:40 am, Room 2002

Session: Catalytic Chemistry of Hydrocarbons
Presenter: A. Resta, Lund University, Sweden
Authors: A. Resta, Lund University, Sweden
J. Gustafson, Lund University, Sweden
R. Westerström, Lund University, Sweden
E. Lundgren, Lund University, Sweden
A. Mikkelsen, Lund University, Sweden
J.N. Andersen, Lund University, Sweden
Correspondent: Click to Email
We have studied the adsorption and thermally induced reactions of C@sub 2@H@sub 4@ and C@sub 2@H@sub 5@OH, on Rh(111) and Rh(553) with particular emphasis on the differences induced by the atomic steps present on the vicinal Rh(553) surface. The development of surface species was followed at temperatures ranging from 100 K to 680 K by chemically sensitive high resolution core level photoemission (HRCLS) applied to the adsorbate C1s and O1s and the substrate Rh 3d levels. Comparing results from the two surfaces, we find a number of differences which can be ascribed to reactions occurring in the vicinity of the steps on Rh(553). For C@sub 2@H@sub 4@ we monitor the formation and subsequent decomposition of ethylidyne (CCH@sub 3@) by saturating the surfaces with C@sub 2@H@sub 4@ at 100K followed by annealing at increasingly higher temperatures. We find that both the formation as well as the decomposition of ethylidyne occur at a lower temperature on Rh(553) than on Rh(111). Although HRCLS spectra indicate similar decomposition products on both surfaces, a more detailed analysis suggests significantly different decomposition scenarios on the two surfaces. In similar annealing experiments of a few layers of C@sub 2@H@sub 5@OH we find that the formation of CO, which indicates the breaking of the C-C bond in ethanol, occurs at lower temperature on Rh(553) than on Rh(111). We never observe atomic O or OH-like groups on neither surface. In addition to the temperature differences we also find significantly different fragmentation patterns on the two surfaces. For instance, ethylidyne is shown to form on Rh(111) but is absent from Rh(553).