Experimental study of the potential degradation due to the polarization curve of a high temperature proton exchange membrane fuel cell

Abstract

The polarization curve is the most common characterization used to describe the steady-state of a fuel cell. The methods proposed in the literature to realize polarization curves for High Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFC) are mainly focused on ensuring stable operating conditions. However, if degradations are caused during its realization, the interpretation of the experimental results may be biased. In order to understand and highlight these different phenomena, an experimental campaign is carried out on Advent PBI (formerly BASF Celtec®-P 1100W) membrane-electrode assemblies (MEA). Four different methodologies for the realization of polarization curves including impedance spectroscopies are proposed. Each one is cycled 30 times in order to compare their impact on fuel cell degradation. The use of a CO2 sensor confirms that carbon corrosion is the main degradation caused by the passage to high voltage. Moreover, the analysis shows that this degradation can be intensified according to the conditions preceding the switch to these voltages. However, the realization of a current truncated polarization curve in order to avoid this degradation can be at the origin of the generation of reversible losses which can distort the interpretation of the results. The atmospheric pressure variation also generates a bias as the polarization curves are not necessarily realized at the same value because the gas outlet pressures are not regulated. A methodology of voltage readjustment according to the operating conditions is thus applied in order to compensate for this effect. Finally, the cycling of one of the polarization curve realization methods shows an interest for improvingthe break-in period.