Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 41: Metal Substrates: Adsorption II
O 41.5: Vortrag
Mittwoch, 28. März 2007, 16:45–17:00, H39
Formation of tetrachloroplatinate complexes on Pt(110). — Enrico Donà1, •Michael Cordin1, Cesare Franchini2, Josef Redinger2, and Erminald Bertel1 — 1Institute for Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck, Austria — 2Center for Computational Material Science, Gumpendorferstraße 1A, A-1060 Vienna, Austria
The chemisorption of Cl and Br on Pt(110) has been studied as a function of coverage by variable-temperature scanning tunneling microscopy (VT-STM) and low-energy electron diffraction (LEED). For a coverage (Θ) of 0.5 monolayers (ML) Cl and Br form a p(2 × 1) and a c(2 × 2) structure, respectively, occupying each second short-bridge (SB) site on the close-packed Pt-rows of the (1 × 1)-Pt(110) surface. Increasing the coverage leads to the formation of a (3 × 1) and a (4 × 1) phase for Θ = 0.66 ML and Θ =0.75 ML respectively, where both SB and long-bridge (LB) sites are occupied. While these two structures are stable for Br, they are only metastable in the case of Cl. Upon soft annealing (300K < T < 670 K) a transition into a phase with (4× 2) periodicity is observed. This phase is characterized by cross-shaped structures, imaged as "clusters" with five bright protrusions by STM. An interpretation of these protrusions entirely in terms of Cl atoms can be excluded by coverage considerations. On the basis of both, experimental arguments and theoretical results the clusters can be identified as tetrachloroplatinate complexes, with the central Pt atom occupying a four-fold hollow site. This implies the onset of Cl induced corrosion on the Pt(110) surface.