Local Flooding Phenomena in Channel and Land Areas Occurring during Dynamic Operation of a PEFC

Authors

  • S. von Dahlen,

    1. Fuel Cell Diagnostics Activities, Paul Scherrer Institut, Electrochemistry Laboratory, 5232 Villigen PSI, Switzerland
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  • I. A. Schneider

    Corresponding author
    1. Fuel Cell Diagnostics Activities, Paul Scherrer Institut, Electrochemistry Laboratory, 5232 Villigen PSI, Switzerland
    • Fuel Cell Diagnostics Activities, Paul Scherrer Institut, Electrochemistry Laboratory, 5232 Villigen PSI, Switzerland
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Abstract

In this work, we report on flooding phenomena occurring during dynamic operation of a polymer electrolyte fuel cell (PEFC). The combination of high spatially and temporally resolved neutron radiography and submillimeter resolved current density distribution measurements enables the simultaneous observation of local liquid water content and current density transients in the channel and land areas of a differentially operated PEFC air cathode. The local transients of a triangular voltage sweep and a voltage step are presented here. Both results demonstrate that in the land area the current density is only marginally affected by the local liquid water content. In the voltage sweep experiment, at higher cell polarization a limiting current density is observed in the land area as a result of mass transport limitations due to the high lateral diffusion path length. In the channel area the corresponding transients of the liquid water content and the current density both exhibit a hysteresis. The transients of the voltage step indicate liquid water rearrangement in channel and land areas as a slow process occurring on a time scale of several minutes. Thereby, the local cell performance is primarily affected by the local liquid water content in front of the oxygen electrode.

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