Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.10: Poster

Freitag, 4. März 2005, 17:00–20:00, Poster TU D

Adsorption of Methanol on Pd₃Sn/Pd(111) Surface- Alloy — •Christian Breinlich, Thomas Schmidt, Conrad Becker, and Klaus Wandelt — Institut für Physikalische Chemie, Wegelerstr.12, 53115 Bonn

Over the last decade several experimental UHV- studies have been published, describing the decomposition of methanol, adsorped on Pd(111)- surfaces, into carbon monoxide and hydrogen. We have investigated the adsorption of methanol on a palladium tin surface alloy with a p(2 × 2) superstructure. The idea behind this is to reduce the reactivity of the palladium surface by alloying it with a less noble metall. We investigated the geometric and electronic properties of the surface by AES, LEED and UPS. TDS showed a desorption of methanol from the multilayer at 140 K. At 160 K the monolayer desorbs intact. Neither CO nor hydrogen were detected in significant amounts, so that in contrast to the bare Pd surface, methanol does not decompose on this alloy. These results were supported by UPS data and work function measurements. There was no evidence, that carbon monoxide or surface carbon were formed. A Redhead analysis of the TDS data resulted in an adsorption energy of the multilayer of about 0.36 eV, which is similar to that on Pd (111). For the monolayer we found an adsorption energy of about 0.41 eV. These data agree with our studies on the corresponding (√3 × √3)R30^∘ PdSn₂/Pd(111) surface alloy.