Analysis of gas transport phenomena in a polymer electrolyte fuel cell by electrochemical pressure impedance spectroscopy
Résumé
Electrochemical pressure impedance spectroscopy (EPIS) was introduced in view to differentiating transport/transfer phenomena of gas and liquid occurring in electrochemical cells. This work aimed at measuring EPIS impedance in a 100 cm 2 membrane fuel cell upon predominant control from gas transport, in conditions where the presence of liquid water is little significant. Operating the fuel cell with pure oxygen allowed observation of gas convection: EPIS impedance modulus was below 1 µV Pa-1 in the frequency range 1 mHz-1 Hz, whereas the phase shift decrease did not exceed 30° near 200 mHz with an MPL-free gas diffusion layer (GDL). Conversely, occurrence of diffusion phenomena with oxygen diluted into nitrogen or helium is revealed by the strong increase in the EPIS modulus up to 12-30 µV.Pa-1 near 500 mHz depending on the nature of the diluting gas, the GDL, and the excess in fed oxygen.
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