A mathematical model of ignition dynamics and bistable operation of a Stirred Tank Reactor (STR) Polymer Electrolyte Membrane (PEM) fuel cell is developed. In dry inlet gas operation the positive feedback between current, water production, and membrane resistance within the model leads to two stable “ignited” states. Within the framework of the model these correspond to a uniform current distribution or a partially extinguished cell with localized current production. The switching between the two regimes is accompanied by hysteresis and transient behavior on the order of 2–4 hours in a small 1 cm2 cell. We compare the numerical results to experimental data gathered by Jay Benziger and show that the steady-state distribution of membrane water is very sensitive to several parameters and is an excellent diagnostic for determining material parameters.

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