Window gasketing for self humidified H2|O2 and H2 |air polymer electrolyte membrane fuel cells fed dry gases

Abstract

Abstract Polymer electrolyte fuel cells (PEFCs) are often formed with the cation exchange polymer Nafion® sandwiched between two electrodes and run on humidified H2 and O2 gases fed to electrodes held in tight gaskets. The tight gasket opening is only slightly wider than the electrodes. When run on dry H2 and O2, tight gasketed cells fail as water becomes imbalanced across the membrane. Here, the cathode is framed by a narrow perimeter washer so the cathode is centered in a generous Nafion window and surrounded by a thin (≈ 0.05 cm) reservoir volume. Unlike tight gasketed cells, water generated at the cathode crosses the large Nafion window to sustain self humidification at 0.522 V on dry H2 and O2 at 70, 37, and 25 oC and dry H2 and air at 37 oC for 1 atm pressure and moderate flow rates. Built from commercial components, window gasketed PEFCs provided stable, steady state current and power at 0.5 V for >170 h on dry H2 and oxidant. Tight gaskets always fail to yield self humidification whereas window gaskets enable effective self humidification on dry gases. A sketch is provided of how the Nafion window enhances water flux from the cathode. Because humidification hardware can be eliminated, window gasketed PEFCs may be especially useful in portable fuel cell systems. Submitted In Honor of Andrej Wieckowski.