Improving PEMFC performance using low equivalent weight PFSA ionomers and Pt-Co/C catalyst in the cathode

The effects of lower equivalent weight (EW) perfluorosulfonic acid (PFSA) ionomers and Pt-Co/C catalyst on the cathode performance of proton exchange membrane fuel cells (PEMFCs) were investigated at two atmospheric pressure operating conditions: low temperature/high relative humidity (RH), 80 degrees C/100% RH, and high temperature/low RH, 120 degrees C/35% RH. Cell voltage at a current density of 400 mA/cm(2) was used for the performance comparison. The optimized content in the electrode changed with the ionomer EW, from 32% for 1100 EW Nafion, 28% for 920 EW Nafion to 25% for a developmental PFSA 800 EW ionomer. Compared to 1100 EW Nafion, 800 EW ionomer significantly improved the cell performance by 39 mV at 120 degrees C/35% RH; however, at 80 degrees C/100% RH, its effect was not apparent. The introduction of Pt-Co/C catalyst into the cathode increased the cell performance by 43 mV at 80 degrees C/100% RH, which was much higher than a performance improvement at 120 degrees C/35% RH. Compared to electrodes made of Pt/C and Nafion 1100 EW, the combination of 800 EW Ionomer and Pt-Co/C catalyst resulted in a 55 mV cell voltage increase at 80 degrees C/100% RH and a 48 mV cell voltage increase at 120 degrees C/35% RH. (c) 2006 The Electrochemical Society. All rights reserved.