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Substitution of Nafion with Sulfonated Polysulfone in Membrane-Electrode Assembly Components for 60-120 °C PEMFC Operation
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.ORCID iD: 0000-0001-9203-9313
Polymer and Materials Chemistry, Department of Chemistry, Lund University.
Polymer and Materials Chemistry, Department of Chemistry, Lund University.
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2008 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 155, no 10, B1001-B1007 p.Article in journal (Refereed) Published
Abstract [en]

To investigate the influence of sulfonated polysulfone (sPSU) in membrane–electrode assemblies (MEAs), sPSU-based gas diffusion electrodes (GDEs) and sPSU membranes were studied both as complete MEAs and as separate components in assembled MEAs at 60–120°C. The complete sPSU MEAs showed mass-transport limitations, irrespective of ion exchange capacity, compared to Nafion MEAs. Cyclic voltammetry and low-current impedance analysis revealed comparable electrochemically active catalyst areas and kinetic properties in the sPSU and Nafion GDEs, while gas-crossover measurements showed a lower gas permeability in sPSU compared to Nafion. The sPSU and Nafion GDEs, deposited on Nafion membranes, possessed comparable fuel cell characteristics at 120°C and 100% relative humidity, demonstrating no considerable limitations when utilizing sPSU as an alternative to Nafion in the GDE, thus implying a sufficient gas permeability in the sPSU GDE at high humidity. Furthermore, the results clearly showed that the sPSU membrane induced mass-transport limitations in both sPSU and Nafion GDEs, revealing that the limiting factor of the sPSU MEAs was primarily the membrane-induced cathode flooding due to unoptimized water transport in the sPSU membrane. The work demonstrates the importance of electrochemical evaluation of ionomers as complete MEAs and as separate components when studying MEAs.

Place, publisher, year, edition, pages
2008. Vol. 155, no 10, B1001-B1007 p.
Keyword [en]
Atmospheric humidity, Bioelectric phenomena, Capillarity, Cell membranes, Cyclic voltammetry, Diffusion in gases, Electric batteries, Electrolysis, Fuel cells, Gas permeability, Gases, Ion exchange, Ion exchange membranes, Ion exchangers, Ionomers, Liquids, Membranes, Metallizing, Meteorology, Moisture, Polymers, Silicones, Voltammetry, Active catalysts, Cathode flooding, Electrochemical evaluations, Gas Diffusion Electrodes, High humidity, Impedance analysis, Ion-exchange capacities, Kinetic properties, Limiting factors, Mass-transport limitations, Membrane-electrode assemblies, Nafion membranes, Relative humidities, Sulfonated polysulfone, Water transport
National Category
Chemical Engineering Chemical Engineering
URN: urn:nbn:se:kth:diva-9180DOI: 10.1149/1.2959113ISI: 000258976500019ScopusID: 2-s2.0-51849165611OAI: diva2:25611
MISTRAs bränslecellsprogram
QC 20100922Available from: 2008-10-13 Created: 2008-09-30 Last updated: 2010-09-22Bibliographically approved
In thesis
1. Membrane Electrode Assemblies Based on Hydrocarbon Ionomers and New Catalyst Supports for PEM Fuel Cells
Open this publication in new window or tab >>Membrane Electrode Assemblies Based on Hydrocarbon Ionomers and New Catalyst Supports for PEM Fuel Cells
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The proton exchange membrane fuel cell (PEMFC) is a potential electrochemicalpower device for vehicles, auxiliary power units and small-scale power plants. In themembrane electrode assembly (MEA), which is the core of the PEMFC single cell,oxygen in air and hydrogen electrochemically react on separate sides of a membraneand electrical energy is generated. The main challenges of the technology are associatedwith cost and lifetime. To meet these demands, firstly, the component expensesought to be reduced. Secondly, enabling system operation at elevated temperatures,i.e. up to 120 °C, would decrease the complexity of the system and subsequentlyresult in decreased system cost. These aspects and the demand for sufficientlifetime are the strong motives for development of new materials in the field.In this thesis, MEAs based on alternative materials are investigatedwith focus on hydrocarbon proton-conducting polymers, i.e. ionomers, and newcatalyst supports. The materials are evaluated by electrochemical methods, such ascyclic voltammetry, polarisation and impedance measurements; morphological studiesare also undertaken. The choice of ionomers, used in the porous electrodes andmembrane, is crucial in the development of high-performing stable MEAs for dynamicoperating conditions. The MEAs are optimised in terms of electrode compositionand preparation, as these parameters influence the electrode structure andthus the MEA performance. The successfully developed MEAs, based on the hydrocarbonionomer sulfonated polysulfone (sPSU), show promising fuel cell performancein a wide temperature range. Yet, these membranes induce mass-transportlimitations in the electrodes, resulting in deteriorated MEA performance. Further,the structure of the hydrated membranes is examined by nuclear magnetic resonancecryoporometry, revealing a relation between water domain size distributionand mechanical stability of the sPSU membranes. The sPSU electrodes possessproperties similar to those of the Nafion electrode, resulting in high fuel cell performancewhen combined with a high-performing membrane. Also, new catalystsupports are investigated; composite electrodes, in which deposition of platinum(Pt) onto titanium dioxide reduces the direct contact between Pt and carbon, showpromising performance and ex-situ stability. Use of graphitised carbon as catalystsupport improves the electrode stability as revealed by a fuel cell degradation study.The thesis reveals the importance of a precise MEA developmentstrategy, involving a broad methodology for investigating new materials both as integratedMEAs and as separate components. As the MEA components and processesinteract, a holistic approach is required to enable successful design of newMEAs and ultimately development of high-performing low-cost PEMFC systems.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. 69 p.
Trita-CHE-Report, ISSN 1654-1081 ; 2008:64
Catalyst support, Carbon, High Temperature Proton Exchange Membrane Fuel Cell, Hydrocarbon Ionomer, Membrane Electrode Assembly, Nafion, PEFC, PEMFC, Porous Electrode, Sulfonated Polysulfone, Titanium Dioxide
National Category
Chemical Engineering
urn:nbn:se:kth:diva-9208 (URN)978-91-7415-124-4 (ISBN)
Public defence
2008-10-24, F3, Lindstedtsvägen 26, Stockholm, 09:30 (English)
QC 20100922Available from: 2008-10-13 Created: 2008-10-03 Last updated: 2010-09-22Bibliographically approved

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