Membrane Electrode Assemblies (MEAs) are key components of PEM fuel cells. Typical characteristics of the advanced MEA products were described. The standard materials consist of catalyst coated membranes (CCMs) and suitable gas diffusion layers (GDLs) which are assembled together in a single cell or PEMFC stack. Because of the broad processing window of the proprietary manufacturing processes, MEAs based on various ionomer membrane materials can be manufactured in different sizes. Due to the high porosity structure of the electrode layers, a significant performance improvement is obtained, particularly at high current densities and ambient pressure conditions. Two different MEA product types are available for hydrogen/air as well as for reformate/air operation. For hydrogen/air operation, the standard MEAs contain Pt catalysts at a total loading of 0.6 mg/cm2. The influence of the key operating parameters such as pressure, humidification and temperature on the MEA performance are described. A MEA lifetime test was run for 1,400 hours in non-interrupted operation showing a very stable cell voltage performance. In steady state reformate operation, the MEAs tolerate various concentrations of carbon monoxide in the anode feed gas depending on the air bleed level applied (300 ppm CO with 3 vol.% air and 100 ppm CO with 0.5 to 1 vol.% air). A simulated methanol reformate containing 60 vol.% H2 was used in these experiments. A major poisoning effect by CO2 could not be detected. As the CO pulsing tests for transient poisoning indicate, up to 1,000 pulses of 300 ppm CO with air bleed levels of 0.5 vol.% can be tolerated in the reformate feed gas without cell voltage decay, thus demonstrating a stable performance of the MEAs under the dynamic operating conditions required for mobile use. A low level of air bleed (0.5 to 1 vol.%) is recommended to compensate for the repeated CO Pulses which can occur in the feed gas due to dynamic load changes of the PrOx reactor. When omitting the air bleed completely, the CO tolerance of the anode electrocatalyst is gradually degrading due to irreversible poisoning of some PtRu sites of the catalyst. Additional work is under way to develop further improved MEAs and electrocatalysts to fulfill the requirements for mobile PEMFC application.


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    Title :

    Advanced MEA technology for mobile PEMFC applications


    Additional title:

    Fortgeschrittene MEA-Technologie für mobile PEMFC-Anwendungen


    Contributors:
    Starz, K.A. (author) / Koehler, J. (author) / Ruth, K. (author) / Vogt, M. (author)


    Publication date :

    2002


    Size :

    6 Seiten, 11 Bilder, 9 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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