Poisoning mechanism of the CO and H₂S mixture on the anode of polymer electrolyte membrane fuel cell

Despite the coexistence of CO and H2S in reformed hydrogen, studies on the interaction between impurities are lacking. In this study, the co-poisoning effect of CO and H2S on a polymer electrolyte membrane fuel cell (PEMFC) is systematically investigated using a hydrogen reference electrode inserted into a membrane electrode assembly (MEA). Notably, when CO and H2S are present simultaneously, the poisoning rate is accelerated and is higher than the simple sum of the poisoning by the individual gases, suggesting a complex synergic effect between the two gases. This phenomenon can be attributed to the potential-dependent behavior of H2S poisoning, whereas CO poisoning remains independent of the potential but depends on the total poisoning time. Therefore, the potential of the anode rises over time due to the time-dependent CO poisoning, which accelerates the potential-dependent H2S poisoning. As a result, the cell voltage decreases more rapidly in the CO and H2S mixture.