Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 60: Dielectric and Molecular/Water Interfaces

O 60.12: Vortrag

Mittwoch, 18. März 2015, 17:45–18:00, MA 043

Methanol electrooxidation on UHV prepared Pt modified Ru(0001) model electrodes — Fabian Argast, •Albert K. Engstfeld, Sylvain Brimaud, and R. Jürgen Behm — Ulm University, Institute of Surface Chemistry an Catalysis, D-89069 Ulm, Germany

The oxidation of methanol (MeOH) on bimetallic PtRu electrodes is described and widely accepted to occur via a bifunctional mechanism, where Pt provides the carbon species and Ru the oxygen species to form CO₂. Only recently it has been shown in a model catalyst study that bimetallic PtRu structures do not necessarily enhance the catalytic activity.(A.K. Engstfeld et al., Angewandte Chemie Int. Ed. 53 (2014) 12936)

We present results on the MeOH electrooxidation on Pt modified Ru(0001) electrodes. The nanostructured electrodes are prepared under ultra high vacuum (UHV) conditions via physical vapour deposition of Pt on Ru(0001) and are characterized by scanning tunnelling microscopy (STM). Subsequently they are transferred to a flow cell system attached to the UHV system for electrocatalytic investigations. We show that PtRu/Ru(0001) surface alloys and Pt island modified Ru(0001) surfaces are essentially inactive for the electrooxidation of MeOH, despite the presence of bimetallic PtRu interfaces. We discuss the influence of vertical and lateral ligand effects of the Ru(0001) acting on the Pt structures, preventing the initial dissociation of the MeOH. We also show that electrochemically restructured surfaces show an enhanced reactivity and we conclude that defect sites on the rough Pt structures are primarily responsible for the increasing activity.