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A polymer electrolyte membrane fuel cell stack was tested for 1000 hours under severe operating conditions, including overnominal temperature and low humidified reactants, to study degradation mechanisms and FC aging.

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What they did

System
MEC

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Abstract

A three-cell polymer electrolyte membrane fuel cell stack equipped with perfluorinated ionomer membranes is tested for 1000 h in severe operating conditions. The fuel cell (FC) is fed by dry hydrogen/low humidified air and it is simultaneously operated at overnominal temperature. During the long term experiment, some polarization curves and electrochemical impedance spectra are recorded at regular time-spaced intervals for various stoichiometry rates. The objective is to characterize the degradation of FC performances with the aim to better understand the FC aging mechanisms. Some response surfaces are plotted to display and analyze the stack voltage variations as a function of aging time, static load current, and gas utilization rates. Different points of the FC impedance spectra are also considered. The evolutions of their coordinates in the Nyquist plot can be monitored versus aging time and for different gas utilization rates.

Key findings

  • The fuel cell showed significant degradation in performance over 1000 hours, with a decrease in stack voltage and an increase in electrochemical impedance.
  • The degradation was more pronounced at higher static load currents and lower gas utilization rates.
  • The Nyquist plot showed a shift in the coordinates of the impedance spectra towards higher frequencies, indicating increased resistance and decreased conductivity.

Keywords

Nyquist plotElectrolyteProton exchange membrane fuel cellStack (abstract data type)MembranePolarization (electrochemistry)

Identifiers

DOI
10.1115/1.3182736
Journal
Journal of Fuel Cell Science and Technology
Year
2010