AVS 50th International Symposium
    Surface Science Friday Sessions
       Session SS1-FrM

Paper SS1-FrM6
Surface Reactions of Co-Adsorbed CH@sub 2@I@sub 2@ and CF@sub 3@I on Ag (111)

Friday, November 7, 2003, 10:00 am, Room 327

Session: Catalysis IV: Reactivity of Complex Systems
Presenter: K. Adib, Brookhaven National Laboratory
Authors: K. Adib, Brookhaven National Laboratory
H. Piao, Brookhaven National Laboratory
J. Hrbek, Brookhaven National Laboratory
W. Huang, University of Texas at Austin
J.M. White, University of Texas at Austin
Correspondent: Click to Email
Synchrotron X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) have been used to study the surface reactions of sequentially coadsorbed CH@sub 2@I@sub 2@ and CF@sub 3@I on Ag (111). When adsorbed separately on Ag (111), CH@sub 2@I@sub 2@ and CF@sub 3@I molecules undergo C-I bond cleavage at temperatures as low as 100 K to produce adsorbed CH@sub 2@ and CF@sub 3@, respectively, as well as I adatoms. In the case of CH@sub 2@I@sub 2@, upon subsequent thermal annealing of the surface, the dissociatively adsorbed CH@sub 2@ fragments may subsequently recombine and desorb primarily as C@sub 2@H@sub 4@. In the case of sequential co-adsorption in the submonolayer regime, the CF@sub 3@ and CH@sub 2@ fragments recombine to desorb as CF@sub 2@CH@sub 2@. Synchrotron XPS results indicate the presence of a surface bound species formed recombinatively in the temperature range of 200-250 K confirming that the CF@sub 2@CH@sub 2@ desorption is a two-step process. The first step involves methylene insertion to produce a surface bound species (CF@sub 3@CH@sub 2@) that can be detected by XPS. The second step involves fluoride elimination and the desorption of CF@sub 2@CH@sub 2@ as detected by TPD.