Roth, C. and Benker, N. and Mazurek, M. and Scheiba, F. and Fuess, H. (2005):
Development of an In-Situ Cell for X-ray Absorption Measurements During Fuel Cell Operation.
7, In: Advanced Engineering Materials, (10), WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, pp. 952-956, ISSN 1438-1656, [Online-Edition: http://dx.doi.org/10.1002/adem.200500122],
[Article]

Abstract

A novel in-situ cell was designed to allow measurements during real fuel cell operation. Thus, potential and fuel dependent changes in the catalyst structure can be pursued in-situ. The X-ray absorption cell was built first in transmission geometry with an inherent graphite beam window, and spectra were recorded at the Pt L3-edge. This design, however, was not feasible for measurements at the Ru K-edge due to the strong absorption of Pt in the Pt-Ru anode catalyst and the low ruthenium content. Therefore, the cell was modified in a second step using either a Be or a Kapton® foil window to allow for fluorescence measurements. The fluorescence set-up offers the additional advantage that Pt at the anode can be separated from Pt at the cathode side without the need to remove part of the cathode in the beam window region. The optimum set-up for both the Pt L3- and the Ru K-edge was found to be the cell hardware modified with a Kapton® window in fluorescence geometry. Spectra of different supported and unsupported electrocatalysts were recorded at different potentials at both edges in hydrogen, H2/CO and methanol operation. But only measurements at a carbon-supported and an unsupported Pt-Ru catalyst in hydrogen will be presented here. Upon first contact with the fuel, both Pt and Ru (surface) oxides present in the as-received state are reduced. Potential-dependent changes, however, are less evident and can be revealed by data fits only.

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