Reaction dynamics in a parallel flow channel PEM fuel cell

The spatiotemporal dynamic response of a segmented anode parallel channel polymer electrolyte membrane fuel cell was monitored following changes in flow rate, temperature, and load resistance. Autohumidified operation with dry feeds at 1 bar pressure was achieved below 70°C, where the convective transport of water vapor was less than the water production by the fuel cell current. The current could be ignited by a single injection of water into the anode feed, or by reducing the temperature and external load resistance. Co-current flow of the hydrogen and oxygen led to current ignition at the outlets of the flow channels, followed by a wave of high current density propagating toward the inlets. Counter-current flow of the hydrogen and the oxygen resulted in ignition near the center of the flow channels; over time the ignition front fanned out. The spatio-temporal dynamics of the current ignition along the flow channels can be effectively predicted from a model of a set of coupled differential fuel cells in series. This is an abstract of a paper presented at the AIChE Annual Meeting (Salt Lake City, UT 11/4-9/2007).