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O: Fachverband Oberflächenphysik

O 100: Metal Substrates: Adsorption and Reactivity

O 100.3: Vortrag

Freitag, 20. März 2015, 11:00–11:15, MA 043

Interaction of CO with bimetallic Pt_xAg_1-x/Pt(111) surface alloys — •Konstantin M. Schüttler, Thomas Diemant, Joachim Bansmann, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany

From recent studies, it is known that supported PtAg nanoparticles show enhanced (electro-) catalytic properties compared to pure Pt nanoparticles. In order to understand their chemical properties and to correlate them with their atomic structure, structurally well-defined Pt_xAg_1-x/Pt(111) surface alloys, whose structure had been characterized by STM in our institute, were chosen as model system. The interaction of CO as probe molecule with these surface alloys was investigated by temperature-programmed desorption (TPD) and infrared spectroscopy (IRRAS) under UHV conditions.

TPD measurements show a modification of the chemical properties of both components in the surface alloy. For CO adsorbed on Pt sites, the trailing edge first shifts to higher temperature with increasing Ag content, indicating a stabilization of adsorbed CO. At higher Ag content in the surface alloy, an additional desorption feature appears at higher temperature, which is attributed to CO adsorption on smaller Pt ensembles surrounded by Ag atoms. Additionally, a small desorption feature appeared at very low temperature for all surface alloys after CO saturation. This desorption feature is attributed to CO adsorption on Ag defect sites.