Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 68: Metal Substrates: Solid-Liquid Interfaces
O 68.4: Vortrag
Donnerstag, 28. Februar 2008, 14:00–14:15, MA 043
Electrochemical Faceting of Ir(210) — Payam Kaghazchi1, Khaled A. Soliman2, Felice C. Simeone2, Ludwig A. Kibler2, and •Timo Jacob1,2 — 1Fritz-Haber-Institut der MPG, D-14195 Berlin — 2Institut für Elektrochemie, Universität Ulm, D-89081 Ulm
Highly-disperse nanoparticles are often used to catalyze (electro)chemical reactions. Unfortunately not all nanoparticles have the same size and shape, but rather show a relatively large distribution, limiting our understanding of the ongoing processes.
Focusing on Ir(210), which experimentally was found to form pyramidal-like nano-facets in presence of oxygen [1], we used density functional theory and the extended ab initio atomistic thermodynamics approach [2] to study the adsorption of oxygen on these surfaces being involved in the nanostructures on Ir(210). Constructing the corresponding (p,T,φ)-phase diagram for Ir(210) in contact with an aqueous electrolyte, we found that the same nano-facets should be stable under electrochemical conditions. Recently we were able to confirm this theoretical prediction by cyclic voltammetry and in-situ scanning tunneling microscopy. The presence of nanofacets for Ir(210) gives rise to a characteristic current-peak in the hydrogen adsorption region for sulfuric acid solution. Regarding the electrocatalytic behavior of the nano-facets we found a considerably lower activity compared to planar Ir(210).
[1] I. Ermanoski, C. Kim, S. P. Kelty, T. E. Madey, Surf. Sci. 2005, 596, 89.
[2] T. Jacob, J. Electroanal. Chem., 607, 158–166 (2007).