Development of a PEFC under low humidified conditions

The life performance must be improved in order to commercialize polymer electrolyte fuel cells (PEFC). A decline of the cell voltage has been found to result from deterioration of the materials and a localization of reaction in the cell. We investigated the localization phenomenon, measuring the current density in the cell. The distribution of current density was measured by divided and isolated electrodes for a long period of operation. At the beginning of generation of electricity, a high current region is observed in the lower gas channel which is relatively humid. However, the high current region gradually moves to the upper dry channel in proportion to the voltage drop, which is remarkable under conditions of low humidity operation. This reaction seems to be reversible, since the PEFC can mostly recover the initial performance, once it is restarted. Improving the MEA and gas separators for low humidified conditions on the basis of this internal analysis, we operated a 20 cells PEFC stack of 0.4 kW for 5000 h and the stack showed −1.5 mV/1000 h of average voltage degradation.