Effects of water removal on the performance degradation of PEMFCs repetitively brought to <0°C

For the mobile application, performance of polymer electrolyte membrane fuel cells (PEMFCs) should be maintained with being exposed to subzero temperatures in the winter time. To simulate the situation, a PEMFC was operated at 80degreesC, stopped, cooled to and kept at -10degreesC for 1 h, and heated to 80degreesC for the next operation. With the thermal cycle, cell performance was measured and found to degrade at a degradation rate of 2.3% based on current density at a cell voltage of 0.6 V. The degradation was attributed to freezing of water that was produced during operation and remained in the PEMFC after the operation. To prevent the performance degradation, water was removed from the PEMFC by supplying dry gases or an antifreeze solution to the PEMFC before the cell temperature fell to below 0degreesC. By using the gas-purging and the solution-purging method designed in this work, the performance degradation rate was successfully reduced to 0.06 and -0.47%, respectively. (C) 2004 The Electrochemical Society.