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Determination of O[H] and CO Coverage and Adsorption Sites on PtRu Electrodes in an Operating PEM Fuel Cell

Roth, Christina and Benker, Nathalie and Buhrmester, Thorsten and Mazurek, Marian and Loster, Matthias and Fuess, Hartmut and Koningsberger, Diederik C. and Ramaker, David E. (2005):
Determination of O[H] and CO Coverage and Adsorption Sites on PtRu Electrodes in an Operating PEM Fuel Cell.
In: Journal of the American Chemical Society, ACS Publications, pp. 14607-14615, 127, (42), ISSN 0002-7863, [Online-Edition: http://dx.doi.org/10.1021/ja050139f],
[Article]

Abstract

A special in situ PEM fuel cell has been developed to allow X-ray absorption measurements during real fuel cell operation. Variations in both the coverage of O[H] (O[H] indicates O and/or OH) and CO (applying a novel ΔμL3 = μL3(V) − μL3(ref) difference technique), as well as in the geometric (EXAFS) and electronic (atomic XAFS) structure of the anode catalyst, are monitored as a function of the current. In hydrogen, the NPt-Ru coordination number increases much slower than the NPt-Pt with increasing current, indicating a more reluctant reduction of the surface Pt atoms near the hydrous Ru oxide islands. In methanol, both O[H] and CO adsorption are separately visible with the Δμ technique and reveal a drop in CO and an increase in OH coverage in the range of 65−90 mA/cm2. With increasing OH coverage, the Pt−O coordination number and the AXAFS intensity increase. The data allow the direct observation of the preignition and ignition regions for OH formation and CO oxidation, during the methanol fuel cell operation. It can be concluded that both a bifunctional mechanism and an electronic ligand effect are active in CO oxidation from a PtRu surface in a PEM fuel cell.

Item Type: Article
Erschienen: 2005
Creators: Roth, Christina and Benker, Nathalie and Buhrmester, Thorsten and Mazurek, Marian and Loster, Matthias and Fuess, Hartmut and Koningsberger, Diederik C. and Ramaker, David E.
Title: Determination of O[H] and CO Coverage and Adsorption Sites on PtRu Electrodes in an Operating PEM Fuel Cell
Language: English
Abstract:

A special in situ PEM fuel cell has been developed to allow X-ray absorption measurements during real fuel cell operation. Variations in both the coverage of O[H] (O[H] indicates O and/or OH) and CO (applying a novel ΔμL3 = μL3(V) − μL3(ref) difference technique), as well as in the geometric (EXAFS) and electronic (atomic XAFS) structure of the anode catalyst, are monitored as a function of the current. In hydrogen, the NPt-Ru coordination number increases much slower than the NPt-Pt with increasing current, indicating a more reluctant reduction of the surface Pt atoms near the hydrous Ru oxide islands. In methanol, both O[H] and CO adsorption are separately visible with the Δμ technique and reveal a drop in CO and an increase in OH coverage in the range of 65−90 mA/cm2. With increasing OH coverage, the Pt−O coordination number and the AXAFS intensity increase. The data allow the direct observation of the preignition and ignition regions for OH formation and CO oxidation, during the methanol fuel cell operation. It can be concluded that both a bifunctional mechanism and an electronic ligand effect are active in CO oxidation from a PtRu surface in a PEM fuel cell.

Journal or Publication Title: Journal of the American Chemical Society
Volume: 127
Number: 42
Publisher: ACS Publications
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Erneuerbare Energien
11 Department of Materials and Earth Sciences > Material Science > Structure Research
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 20 Feb 2013 09:47
Official URL: http://dx.doi.org/10.1021/ja050139f
Identification Number: doi:10.1021/ja050139f
Funders: Financial support of the Deutsche Forschungsgemeinschaft is gratefully acknowledged.
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