Effects of Ozone on the Performance of a Polymer Electrolyte Membrane Fuel Cell
Résumé
The effects of ozone at concentrations near 1000 vppm in air on the performance of a single polymer electrolyte membrane fuel cell (PEMFC) were investigated. Ozone was injected to the cathode alternately with far longer operation periods at 0.54 A cm-2 with ozone-free air. Impedance spectra were recorded before, during and after exposure to ozone. After the first ozone injection, the loss in voltage was reversible, so were the changes in the resistances of the cell. Subsequent injection periods damaged irreversibly the PEMFC assembly. TEM observations with energy dispersive X-ray spectroscopy analysis of the various parts of the PEMFC assembly together with the variations of the resistances allowed the ageing mechanism to be highlighted. Ozone was shown to allow partial dissolution of the Pt of the cathode catalyst. The charge transfer resistance was noticeably increased accordingly. Platinum re-precipitated in the membrane bulk, and was also observed in the cathode-side GDL. In addition, the likely degradation of the polymer near the triple-point in the cathode could hinder gas solubility and water removal, as indicated by larger diffusion resistances.