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  • 1.
    Gode, Peter
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Ihonen, Jari
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Strandroth, A.
    Ångström Laboratory, Department of Materials Chemistry, Uppsala University.
    Ericson, Hanna
    Department of Experimental Physics, Chalmers University of Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Paronen, Mikael
    Laboratory of Polymer Chemistry, University of Helsinki.
    Sundholm, Franciska
    Laboratory of Polymer Chemistry, University of Helsinki.
    Sundholm, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Walsby, Nadia
    Department of Material Science, Cranfield University, Shrivenham, United Kingdom.
    Membrane Durability in a PEM Fuel Cell Studied Using PVDF Based Radiation Grafted Membranes2003In: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 3, no 1-2, p. 21-27Article in journal (Refereed)
    Abstract [en]

    The durability testing of membranes for use in a polymer electrolyte fuel cell (PEFC) has been studied in situ by a combination of galvanostatic steady-state and impedance measurements. The PEFC measurements, which are time consuming, have been compared to fast ex situ testing in 3% H2O 2 solution. For the direct assessment of membrane degradation micro-Raman spectroscopy and determination of ion exchange capacity (IEC) have been used. PVDF based membranes, radiation grafted with styrene and sulfonated, were used as model membranes. By using low degrees of grafting, below about 35%, the durability of this type of membrane can be increased. Degradation in the fuel cell was found to be highly localised. It was found that in situ measurements in the PEFC alone are not sufficient. Measurement of the cell resistance via impedance is not always a reliable indicator of changes in membrane resistance because other resistance changes in the cell can easily interfere and cannot be separated from those caused by the membrane. Micro-Raman is an ideal complementary method to in situ testing, but it is time consuming. For fast pre-screening of membrane durability mass loss measurements during exposure to 3% H2O2 solution combined with the determination of changes in the IEC can be performed.

  • 2.
    Ihonen, Jari
    et al.
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Mikkola, M.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Flooding of gas diffusion backing in PEFCs - Physical and electrochemical characterization2004In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 151, no 8, p. A1152-A1161Article in journal (Refereed)
    Abstract [en]

    In polymer electrolyte fuel cells (PEFCs) gas diffusion backings (GDBs) have a significant effect on water management and cell performance. In this study, methods for characterizing GDB performance by fuel cell testing and ex situ measurements are presented. The performance of four different commercial GDB materials was tested and significant differences were found between the materials. While the performance and behavior are almost similar in the single-phase region, the flooding behavior of different GDBs in the two-phase region varies widely. The results show that using high clamping pressures increases cell flooding, but the increase varies from material to material. Increased flooding is caused by the combination of decreased porosity and a temperature difference between GDB and current collector. Furthermore, it was observed that the decrease in porosity due to cell compression and corresponding increase in mass-transfer resistance should be studied in the single-phase region, because flooding of the GDB easily becomes the dominating source of mass-transfer resistance. In addition, a literature review on GDB studies and characterization methods was carried out. The review revealed a lack of an established GDB testing regime and the absence of a relation between physical properties of the GDB and fuel cell performance.

  • 3. Noponen, M.
    et al.
    Ihonen, Jari
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Current distribution measurements in a PEFC with net flow geometry2004In: Journal of Applied Electrochemistry, ISSN 0021-891X, E-ISSN 1572-8838, Vol. 34, no 3, p. 255-262Article in journal (Refereed)
    Abstract [en]

    A measurement system for current distribution mapping for a PEFC has been developed. The segmented anode is constructed so as to have high thermal conductivity in order to prevent the formation of large temperature gradients between the electrodes. The construction is therefore feasible for use at high current densities. Both segmented and unsegmented gas diffusion layers are used. The effect of inlet humidification and gas composition at the cathode side is studied. In addition, two different flow geometries are studied. The results show that the measurement system is able to distinguish between current distribution originating from differences in proton conductivity, species concentration and gas diffusion layer properties.

  • 4. Noponen, Matti
    et al.
    Birgersson, Erik
    KTH, Superseded Departments, Mechanics.
    Ihonen, Jari
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Vynnycky, Michael
    KTH, Superseded Departments, Mechanics.
    Lundblad, Anders
    KTH, Superseded Departments, Chemical Engineering and Technology.
    Lindbergh, Göran
    KTH, Superseded Departments, Chemical Engineering and Technology.
    A two-phase non-isothermal PEFC model: Theory and validation2004In: Fuel Cells, ISSN 1615-6846, E-ISSN 1615-6854, Vol. 4, no 4, p. 365-377Article in journal (Refereed)
    Abstract [en]

    A two-dimensional, non-isothermal, two-phase model of a polymer electrolyte fuel cell (PEFC) is presented. The model is developed for conditions where variations in the stream-wise direction are negligible. In addition, experiments were conducted with a segmented cell comprised of net flow fields. The, experimentally obtained, current distributions were used to validate the PEFC model developed. The PEFC model includes species transport and the phase change of water, coupled with conservation of momentum and mass, in the porous backing of the cathode, and conservation of charge and heat throughout the fuel cell. The current density in the active layer at the cathode is modelled with an agglomerate model, and the contact resistance for heat transfer over the material boundaries is taken into account. Good agreement was obtained between the modelled and experimental polarization curves. A temperature difference of 6°C between the bipolar plate and active layer on the cathode, and a liquid saturation of 6% at the active layer in the cathode were observed at 1 A cm-2.

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