Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 28: Adsorption an Oberfl
ächen III

O 28.6: Vortrag

Donnerstag, 27. März 2003, 12:30–12:45, FOE/ANOR

Distribution and mobility of Sn adlayer on Pt(111) electrode: co-adsorption with Cu UPD and CO — •Xiaoyin Xiao, Steffen Tillmann, and Helmut Baltruschat — Institute of Physical Chemistry, University Bonn, Romerstr. 164, D 53117 Bonn

Four different surface states are observed when Sn is deposited on a Pt(111) surface at controlled coverages changing from monolayer to the submonolayer region, as indicated by the reduction processes in cyclic voltammetry. At high coverages, Sn adlayers show only one broad oxidation peak at 0.8 V. With decreasing Sn coverage, a specific redox peak pair appears at around 0.61 V and achieves a maximum value of 76 mC cm-2. Its decrease upon further dissolution of Sn is connected to the appearance of hydrogen and sulfate adsorption. The coexistance of the ’spike’ for sulfate adsorption with the Sn redox peaks at low coverages indicates the segregation of Sn into islands.

Adsorbed Sn is not directly observable by STM except when coadsorbed with Cu, CO or sulfate ions. In that case, Sn segregates in observable islands, which indicates a repulsive interaction with these species. 2D step decoration is found and the terraces of the Pt surface were randomly covered by small Sn islands. Within the islands, there is no clear ordering of Sn. We assume that the high mobility of Sn islands prevents its observation in the hydrogen region [1].
X. Xiao, S. Tillmann, and H. Baltruschat, Physical Chemistry Chemical Physics, 2002, 4, 4044.