Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 10: Metal/Water Interfaces: Structure and Reactivity
O 10.12: Vortrag
Montag, 16. März 2015, 17:45–18:00, HE 101
Electrocatalytic activity and stability of structurally well defined AgPt/Pt(111) surface alloys-correlation between structure and reactivity — •Stephan Beckord, Albert K. Engstfeld, Sylvain Brimaud, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, 89069 Ulm, Germany
Bimetallic surface often show electrochemical and catalytic properties different from those of the individual metals. This is evident, e.g., in the oxygen reduction reaction (ORR), where Pt is known to be the most active single metal catalyst. However, in previous studies it was shown that this high activity can be enhanced by modifying Pt with transition or noble metals, such as Ni, Co or Cu.[1] We show results on the electrochemical and electrocatalytic properties of well defined AgxPt1−x surface alloys on Pt(111) with increasing Ag content (0%-100% Ag). The surface alloys were prepared under ultra high vacuum (UHV) conditions by physical vapor deposition of Ag on Pt(111), followed by an annealing step to 900 K. Via scanning tunneling microscopy (STM) the atomic distribution in the topmost layer, as well as the abundance of catalytic relevant ensembles (e.g. Pt1Ag2, Pt2Ag1) is determined. Subsequently the surfaces are characterized in an electrochemical flow cell attached to the main UHV system with respect to their stability and their ORR activity in H2SO4. To validate the stability of the surface alloys, they are re-analyzed by STM after the electrochemical measurements. Finally, the experimental results are compared to simulated activities based on DFT calculations.
[1] J. Greeley and J.K. Nørskov, J. Phys. Chem. 113 (2009) 4932.