The poisoning level of Pt/C catalysts used in PEM fuel cells by the hydrogen feed gas impurities: The bonding strength

Proton exchange membrane fuel cells (PEMFCs) most likely will use reformed fuel as the primary source for the anode feed despite it nearly always contains carbon monoxide or ammonia. In this paper, the microcalorimetry technique was employed to study and compare the poisoning effect of pollutants such as CO and NH3 on three commercial carbon-supported platinum catalysts with high Pt loading, aimed to be used in PEMFCs applications. Microcalorimetric measurements were performed at 80 °C and the results were compared with those obtained from hydrogen adsorption in similar conditions. All the catalysts exhibited significantly higher differential heats of CO adsorption in comparison with NH3 and hydrogen adsorption, indicating that carbon monoxide will be primarily adsorbed in case of co-adsorption, while ammonia and hydrogen will compete in the adsorption process on the same type of active sites. The irreversibly (chemically) amount of adsorbed molecules on Pt/C surfaces decreases in the order: CO >> NH3 > H2.