Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 11: Grenzfl
äche fest-flüssig

O 11.1: Vortrag

Montag, 24. März 2003, 15:00–15:15, M\"UL/ELCH

The potentials of zero charge of Pd(111) and ultra thin Pd films on Au(111) and Pt(111) — •A.M. El-Aziz, R. Hoyer, L.A. Kibler, and D.M. Kolb — Department of Electrochemistry, University of Ulm, 89069 Ulm, Germany

The potential of zero charge (pzc) is a fundamental parameter characterizing the metal/electrolyte interface, and its knowledge is important for a detailed understanding of double-layer phenomena and the adsorption behaviour of charged and neutral species. However, there is a lack about the information of pzc of Pt metal single crystals. This shortage is often caused by specific adsorption on these surfaces. The potential of zero charge (pzc) of Pd(111) has been determined in dilute NaF solutions according to Gouy-Chapman theory by differential capacitance measurements. For massive Pd(111) single crystal electrode a pzc of -0.12V vs. SCE has been found. The corresponding values for thin Pd overlayers on Au(111) as well as on Pt(111) have been determined. It is strongly dependant on the nature of the metal substrate. The pzc of the first pseudomorphic Pd layers on Au(111) as well as on Pt(111) are -0.09V and -0.21V vs. SCE, respectively. By increasing the coverage of Pd overlayers, a clear shift of the pzc to the value of massive Pd(111) is recorded. The results were compared with pzc of massive Pd(111) indicating a significant dependence on the film thickness of the ultra thin Pd layers and the surface structure. By comparing pzc’s and work function for Au(111) and Pd(111), the dipole contribution to the potential drop across the Pd(111)/water interface is estimated.