Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 13: Solid-liquid interfaces

O 13.5: Talk

Monday, March 27, 2006, 16:00–16:15, WIL C207

Ensemble size effects in the electrochemical properties of PtRu/Ru(0001) and PdRu/Ru(0001) surface alloys — •H.E. Hoster, A. Bergbreiter, E. Filonenko, and R.J. Behm — Abt. Oberflächenchemie und Katalyse, Universität Ulm, 89069 Ulm

Atomically smooth PtRu and PdRu surface alloys can be prepared in UHV by vapor deposition of Pt or Pd on Ru(0001), respectively, followed by heating to 1000-1350 K. This leads to an incorporation of Pt (Pd) mainly into the outermost layer, which then contains fractions of Pt (Pd) immediately determined by the amount deposited initially. The lateral atomic distribution in the 2D alloys, however, is significantly different in PdRu compared to PtRu. As in bulk alloys, Pt and Ru are well miscible also in two dimensions, coming along with a nearly random atomic distribution. Pd and Ru, on the other hand, are bulk immiscible and also show a clear tendency towards phase separation on a low nm-scale in the studied surface alloys. Atomic distribution and surface density of distinct adsorption ensembles are derived from STM images and quantitatively related to certain features in electrochemical adsorption and reaction data, which provides insights into the ensemble size requirements of typical adsorbates and reactants.