CO tolerance by the PEMFC operational at temperatures up to 200°C

The CO poisoning effect on carbon-supported platinum catalysts in polymer electrolyte membrane fuel cells has been investigated in a temperature range from 125 to 200°C 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 a poisoning factor as less than 2% of power loss due to the poisoning effect, it is evaluated that 3% CO in hydrogen can be tolerated at current densities up to 0.7 A/cm2 at 200oC, while at 125oC 0.1% CO in hydrogen can be tolerated at current densities lower than 0.25 A/cm2. For comparison, the tolerance is only 0.0025 % CO (25 ppm) at 80°C at current densities up to 0.15 A/cm². The effect of CO2 in hydrogen was also studied. At 175°C, 25% CO2 in the fuel stream showed only the dilution effect.