| Summary: | We investigated influences of SO2 concentration and relative humidity in fuel and air streams on anode and cathode poisoning behaviors under open circuit voltage and load operating conditions in polymer electrolyte membrane fuel cells (PEMFCs). The rate of cell voltage degradation increased with the increase in SO2 concentration and the normalized cell voltage drop curves were consistent with each other. Cell voltage at equilibrium with SO2 supply was inversely proportional to the concentration of supplied SO2, suggesting that adsorption of sulfur species on the catalyst was in equilibrium and was determined by the SO2 concentration in the electrode. Relative humidity significantly impacted electrode contamination. Electrochemical surface area (ECSA) measured by cyclic voltammetry (CV) revealed pronounced anode contamination under lower RH conditions and suppressed contamination under high RH conditions. Fuel cell load operation showed mitigated anode poisoning, suggesting that appropriate water management of the polymer electrolyte membrane fuel cell (PEMFC) mitigates electrode contamination.
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