The CO Poisoning Effect in PEMFCs Operational at Temperatures up to 200°C

The CO poisoning effect on carbon-supported platinum catalysts at a loading of 0.5 mg Pt/cm 2 per electrode in polymer electrolyte membrane fuel cells PEMFCs has been investigated in a temperature range from 125 to 200C with the phosphoric acid-doped polybenzimidazole membranes as electrolyte. The effect is very temperature-dependent and can be sufficiently suppressed at elevated temperature. By defining the CO tolerance as a voltage loss less than 10 mV, it is evaluated that 3% CO in hydrogen can be tolerated at current densities up to 0.8 A/cm 2 at 200C, while at 125C 0.1% CO in hydrogen can be tolerated at current densities lower than 0.3 A/cm 2 . For comparison, the tolerance is only 0.0025% CO 25 ppm at 80C at current densities up to 0.2 A/cm 2 . The relative anode activity for hydrogen oxidation was calculated as a function of the CO concentration and temperature. The effect of CO 2 in hydrogen was also studied. At 175C, 25% CO 2 in the fuel stream showed only the dilution effect.