Berlin 2015 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 60: Dielectric and Molecular/Water Interfaces
O 60.9: Vortrag
Mittwoch, 18. März 2015, 17:00–17:15, MA 043
Substrate induced modifications of the electrocatalytic properties of Pt and Pd monolayers on Au: combined electrochemical and periodic DFT study — •Jan Kučera1, Sylvain Brimaud2, Rolf Jürgen Behm2, and Axel Groß1 — 1Institut für Theoretische Chemie, Universität Ulm — 2Institut für Oberflächenchemie und Katalyse, Universität Ulm, D-89069 Ulm, Germany
We combine experimental electrochemical approaches with periodic density functional theory (DFT) calculations to elucidate substrate-induced modifications of noble metal electrodes. The systematic utilization of vertical-ligand effects in order to tune electrocatalytic properties of metal electrodes is often hindered by experimental problems in the practical preparation of well defined bimetallic surfaces. As shown recently, smooth and stable Pt monolayer films on Au (Pt-ML) can be realize by using CO as stabilizing agent [1]. Electrocatalytic testing confirmed that the activity of the resulting Pt-ML differs from that of Pt-bulk. Specifically, the electrooxidation of a CO adlayer on Pt-ML is shifted by about 0.2 V to higher potential compared to Pt-bulk. In contrast, comparative examination of Pd-ML and Pd-bulk systems revealed only subtle changes. Theoretical models show that the electronic structure of adsorbed CO remains practically unchanged upon the exchange of the both substrates. However, a variation of the electronic density in the surface metal layer leads to different thermodynamical stabilities of CO adlayers at high-coverages, whose impact on electrocatalyc CO oxidation activity is discussed.
[1] S. Brimaud and R. J. Behm, J. Am. Chem. Soc. 135 (2013) 11716.