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Physical and electrochemical characterization of catalysts for oxygen reduction in fuel cells

Christenn, Claudia and Steinhilber, Gudrun and Schulze, Mathias and Friedrich, Kaspar Andreas (2006) Physical and electrochemical characterization of catalysts for oxygen reduction in fuel cells. Journal of Applied Electrochemistry, 37 (12), pp. 1463-1474. Springer Netherlands. DOI: 10.1007/s10800-007-9369-2

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The cathode catalysts in low temperature fuel cells are associated with major cell efficiency losses, because of kinetic limitations of the oxygen reduction reaction. Additionally, methanol oxidation at the cathode leads to significant lowering of the efficiency in direct methanol fuel cells, which can be alleviated by use of methanol-tolerant catalysts. In this work, alternative carbon-supported platinum-alloy catalysts were investigated by physical methods. Second, methanol-tolerant ruthenium-selenide catalysts were characterized by physical and electrochemical methods. Besides V-i characteristics and electrochemical impedance spectroscopy as electrochemical methods, physical methods such as X-ray photoelectron spectroscopy, nitrogen adsorption, porosimetry by mercury intrusion and temperature programmed reduction are used to characterize the catalysts. The electrochemical characterization yields information about properties and behavior of the catalyst. In contrast to platinum a significantly different hydrophobic behavior of the carbon supported RuSe catalysts is found. Low open circuit voltage values measured for RuSe/C indicate an effect on both electrodes. The anode reaction was also influenced by the different cathode catalysts. As a result of the formation of H<sub>2</sub>O<sub>2</sub> at the cathode, which passes the membrane from cathode to anode side, a mixed anode potential is formed. By comparing carbon supported RuSe catalysts before and after electrochemical stressing, changes of the catalysts are determined. Postmortem surface analysis (by X-ray photoelectron spectroscopy) revealed that catalyst composition and MEA structure changed during electrochemical stressing. During fuel cell operation selenium oxide is removed from the surface of the catalysts to a large extent. Additionally, a segregation effect of selenium in RuSe to the surface is identified.

Item URL in elib:https://elib.dlr.de/45940/
Document Type:Article
Title:Physical and electrochemical characterization of catalysts for oxygen reduction in fuel cells
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Date:31 October 2006
Journal or Publication Title:Journal of Applied Electrochemistry
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
DOI :10.1007/s10800-007-9369-2
Page Range:pp. 1463-1474
Publisher:Springer Netherlands
Keywords:Cathode catalyst, Electrochemical characterization, Methanol, Pt-alloy, Physical characterization, Ruthenium selenides
HGF - Research field:Energy
HGF - Program:Efficient Energy Conversion (old)
HGF - Program Themes:E BZ - Fuel cells (old)
DLR - Research area:Energy
DLR - Program:E BZ - Fuel cells
DLR - Research theme (Project):E - Membran-Brennstoffzellen (old)
Location: Stuttgart
Institutes and Institutions:Institute of Engineering Thermodynamics > Electrochemical Energy Technology
Deposited By: Christenn, Claudia
Deposited On:07 Jan 2008
Last Modified:12 Dec 2013 20:22

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