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XPS investigation of the PTFE induced hydrophobic properties of electrodes for low temperature fuel cells

Schulze, Mathias und Christenn, Claudia (2005) XPS investigation of the PTFE induced hydrophobic properties of electrodes for low temperature fuel cells. Applied Surface Science, 252, Seiten 148-153. Elsevier Science Direct. doi: 10.1016/j.apsusc.2005.02.007.

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Offizielle URL: http://www.elsevier.com/locate/apsusc

Kurzfassung

In electrodes of low temperature fuel cells like polymer electrolyte membrane fuel cells (PEFC) or alkaline fuel cells (AFC) the reactants and the water must be transported. For this purpose the pore system in the electrodes needs a hydrophilic character for the transport of the water and a hydrophobic character for the transport of the gases. The degree of the hydrophobicity determines whether the pore system will be flooded by the reaction water. In the case of PEFC, this is also determined by the degree of the required humidification of the reaction gases. In AFC hydrophobicity determines the extension of the three-phase reaction zone. Caused by the strong influence of hydrophobicity on the transport processes, the electrochemical performance and the optimized operation conditions are also affected by hydrophobicity. Typically polytetrafluoro-ethylene (PTFE) is used to make the electrodes hydrophobic, because PTFE has a high chemical stability. Hydrophobicity depends on the concentration of PTFE on the electrode surface. The PTFE concentration, which is related to the hydrophobic character, can be determined by XPS. The changes in the PTFE content and structure of the electrode of a PEFC was investigated by cyclic voltammetry and XPS and correlated with the performance of the cell in long-term operation. With both methods an initial significant increase in free and electrochemically active surface platinum area is observed. This activation is associated with a degradation of the PTFE in the electrode which is responsible for the hydrophobic properties of the electrode. With further operation the performance of the cell decreases because the water management becomes more critical. Generally, it is shown that XPS can be used for the investigation of the hydrophobicity of electrodes prepared by various manufacturing techniques as well as of changes in their hydrophobicity induced by the electrochemical operation.

elib-URL des Eintrags:https://elib.dlr.de/43896/
Dokumentart:Zeitschriftenbeitrag
Titel:XPS investigation of the PTFE induced hydrophobic properties of electrodes for low temperature fuel cells
Autoren:
AutorenInstitution oder E-Mail-AdresseAutoren-ORCID-iDORCID Put Code
Schulze, MathiasNICHT SPEZIFIZIERTNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Christenn, ClaudiaNICHT SPEZIFIZIERTNICHT SPEZIFIZIERTNICHT SPEZIFIZIERT
Datum:April 2005
Erschienen in:Applied Surface Science
Referierte Publikation:Ja
Open Access:Nein
Gold Open Access:Nein
In SCOPUS:Nein
In ISI Web of Science:Ja
Band:252
DOI:10.1016/j.apsusc.2005.02.007
Seitenbereich:Seiten 148-153
Verlag:Elsevier Science Direct
Status:veröffentlicht
Stichwörter:Fuel cells; Hydrophobic properties; XPS
HGF - Forschungsbereich:Energie
HGF - Programm:Rationelle Energieumwandlung (alt)
HGF - Programmthema:E BZ - Brennstoffzellen (alt)
DLR - Schwerpunkt:Energie
DLR - Forschungsgebiet:E BZ - Brennstoffzellen
DLR - Teilgebiet (Projekt, Vorhaben):E - Membran-Brennstoffzellen (alt)
Standort: Stuttgart
Institute & Einrichtungen:Institut für Technische Thermodynamik > Elektrochemische Energietechnik
Hinterlegt von: Schulze, Dr.rer.nat. Mathias
Hinterlegt am:27 Nov 2006
Letzte Änderung:27 Apr 2009 12:56

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