COLL 488 |
| Hoydoo You, Materials Science Division, Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60563 |
| We studied ordered structures formed on Pt (111) surface in 50 mM H2SO4 and 0.1 M HClO4 + 10 mM NaBr in the presence of solution phase CO. Both (2x2)-3CO and (sqrt19 x sqrt19)R23.4-13CO commensurate super-lattices, previously seen in Weaver's STM studies, were confirmed by x-ray surface scattering measurements. The (2x2) reflections are observed at negative electrode potentials as seen by Markovic et al. and they are replaced by the (sqrt19 x sqrt19)R23.4 reflections positive to the CO oxidation pre-wave. We also studied polarization dependence of the resonant surface scattering spectra. We found that p-polarized spectra in the presence of adsorbed CO for all scattering directions show a bipolar shape with a dip corresponding to Pt Fermi level energy followed by a peak at ~6 eV higher than the Fermi level. The peak in the bipolar-shape spectra is present neither in s-polarized spectra nor in the absence of absorbed CO. Explanation and implications of the observed resonance surface x-ray scattering phenomena will be discussed. Work was performed in collaboration with Y. Tolmachev, A. Menzel, A. Tkachuk, and Y. Chu (ANL) and supported by DOE, Materials and Chemical Science Divisions, Office of Basic Energy Science, under Contract No. W-31-109-ENG-38. |
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Electrochemistry and Surface Science Symposium in Memory of Mike Weaver
Division of Colloid and Surface Chemistry |