Dresden 2003 – wissenschaftliches Programm
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O: Oberflächenphysik
O 21: Adsorption an Oberfl
ächen II
O 21.13: Vortrag
Dienstag, 25. März 2003, 18:00–18:15, HSZ/03
Adsorption of Methanol on PtRu/C Electrocatalysts studied by Cyclic Voltammetry and by DEMS — •Thomas Seiler1, Elena Savinova1, Kaspar Andreas Friedrich2, and Ulrich Stimming1 — 1TU München, Physik-Department E19, James-Franck-Straße 1, 85748 Garching — 2ZSW Baden-Württemberg, Helmholtzstraße 8, 89081 Ulm
The kinetics of methanol adsorption on PtRu/C electrocatalysts embedded in a membrane electrode assembly of a fuel cell has been studied in the temperature range between 30 ∘C and 110 ∘C. Adsorption was carried out at open circuit potentials (OCP ∼ 20 mV vs RHE) leading to anode poisoning by formation of reaction intermediates. The coverage of the intermediates increases with increasing temperature. The adsorption isotherms were of Temkin type delivering kad = 1,59 cm3 mol−1 s−1 (at 30 ∘C), the apparent activation energy EA = 44,6kJ/mol and the interaction parameter α f which was found to decrease with increasing temperature. By means of a novel DEMS setup the nature of the stable adsorption product has been determined. Above the oxidation onset potential, exlusively CO was found. The H coverage was calculated from the Hupd desorption charge. The relative quantity of H which could be desorbed after methanol adsorption was higher than the relative H desorption charge obtained after adsorption of CO. This effect was more pronounced towards lower temperatures and adsorbate coverages.