Effect of air contaminants on electrolyte degradation in polymer electrolyte membrane fuel cells

The effect of air contaminants (NH3, NO2, H2S, and SO2) on electrolyte degradation was evaluated in PEMFCs. 2 ppm of these contaminants were supplied, and the F-release rate in the cathode effluent water was analyzed under a current density of 1000 mA/cm(2) at 80 degrees C. In the case of sulfur species H2S and SO2, a significant decrease in cell voltage and an increase in F- release rate were observed. The electrolyte degradation appears to be accelerated by hydroxyl radicals generated from H2O2, which was produced by a sulfur-poisoned Pt catalyst. F-19-NMR analysis of the sulfur-poisoned MEA revealed that the degradation of the cathode ionomer was significant compared to the anode ionomer and the membrane. Degradation of the cathode ionomer was confirmed by experiment with the MEA composed of a hydrocarbon-based membrane and a perfluorosulfonic acid ionomer, in which an increase in the F- release rate was also observed.