Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 39: Metal substrates: Solid-liquid interfaces

O 39.5: Talk

Wednesday, March 25, 2009, 16:00–16:15, SCH A315

CO electrooxidation at Pt_xRu_1−x/Ru(0001) surface alloys and Pt modified Ru(0001) — •Harry E. Hoster, Otavio Alves, Andreas Bergbreiter, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany

We report on the activity of Pt_xRu_1−x/Ru(0001) surface alloys [1] and Ru(0001) with and without Pt islands [2] towards continuous electrochemical oxidation of CO. The samples were prepared in ultrahigh vacuum (UHV) but the potential dependent CO oxidation currents were recorded under enhanced mass transport conditions in a flow cell attached to the UHV system. On bare Ru(0001), measurable CO oxidation only takes place at E > 0.55 V. Whereas modification by Pt islands does not change this threshold, the attainable oxidation currents become much higher, which we explain by a catalytic effect where Pt helps maintaining high local coverage of CO+O(H) adlayer at the Ru areas. Atomically dispersed Pt_xRu_1−x/Ru(0001) surface alloys show an even higher activity, which results from the higher versatility of mixed or electronically varied adsorption sites with intermediate bonding power. The role of the lateral atom distribution of PtRu surfaces for their local adsorption properties and the reactivity of mixed adlayers under reaction conditions are discussed and compared to previous experimental and theoretical findings.
H.E. Hoster et al., Phys.Chem.Chem.Phys. 10 (2008) 3812.
H.E. Hoster et al., J. Phys. Chem. B 108 (2004) 14780.