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Gas Diffusion Electrodes and Membrane Electrode Assemblies Based on a Sulfonated Polysulfone for High-Temperature PEMFC
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
Division of Polymer and Materials Chemistry, Lund University.
Division of Polymer and Materials Chemistry, Lund University.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Applied Electrochemistry.
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2006 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 153, no 11, A2077-A2084 p.Article in journal (Refereed) Published
Abstract [en]

Membrane electrode assemblies MEAs with a sulfonated polysulfone sPSU as the proton-conducting phase were fuel cellevaluated at varying temperatures in over-humidified conditions. The sPSU was prepared by a direct polycondensation involvinga commercially available sulfonated naphthalene diol monomer. The gas diffusion electrodes GDEs and MEAs were successfullyfabricated and a thorough morphological study was subsequently carried out on GDEs with varying sPSU contents and inksolvents. The scanning electron microscopy and porosimetry studies revealed highly porous GDE morphologies at sPSU contentsbelow 20 wt %. Double-layer capacitance measurements showed an almost fully sPSU-wetted electronic phase when the sPSUcontent was 10 wt %. The MEAs were prepared by applying the GDEs directly onto sPSU membranes. MEAs with a total Ptloading of 0.2 mg/cm2 were successfully fuel cell operated at 120°C. The MEAs showed mass-transport limitations in the rangeof 600–800 mA/cm2, most probably caused by abundant water due to the overhumidified measuring conditions. The low resistanceof the MEAs indicated a well-integrated structure between the GDEs and the membrane.

Place, publisher, year, edition, pages
2006. Vol. 153, no 11, A2077-A2084 p.
Keyword [en]
Gas diffusion electrodes (GDE), Membrane electrode assemblies (MEA), Sulfonated polysulfone (sPSU), Diffusion, High temperature effects, Membranes, Monomers, Morphology, Polysulfones
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9178DOI: 10.1149/1.2335979ISI: 000241057000011Scopus ID: 2-s2.0-33749612550OAI: oai:DiVA.org:kth-9178DiVA: diva2:25593
Projects
MISTRAS bränslecellsprogram
Note
QC 20100922Available from: 2008-10-13 Created: 2008-09-30 Last updated: 2017-12-13Bibliographically 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.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:64
Keyword
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
Identifiers
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)
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Supervisors
Note
QC 20100922Available from: 2008-10-13 Created: 2008-10-03 Last updated: 2010-09-22Bibliographically approved

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