Study of PEFCs by AC Impedance, Current Interrupt, and Dew Point Measurements

The effect of humidity in oxygen gases on the performance of a polymer electrolyte fuel cell (PEFC) was examined by using linear current sweep (current-voltage), current interrupt, and ac impedance methods in combination with temperature variations of cathode humidifiers. The total resistance of the membrane increased about 3.4 mΩ by the temperature change of the cathode humidifier from 80 to 35°C. The results of electrochemical analysis showed that one-third of the total resistance change was due to the membrane resistance and almost the same amount could be attributed to the charge-transfer resistance. The measurements of dew points in hydrogen and oxgen gases at the entrance and the exit of the fuel cell made it clear that the water transport was sensitively affected by the temperatures of humidifiers of the cathode side. In the case of equal temperatures, water migrated from the cathode side to anode side, while the water movement in the reverse direction took place at the cathode humidifier temperature lower than the anode.