Correlating Nitrogen Accumulation With Temporal Fuel Cell Performance

The permeability or crossover characteristics of a typical perfluorosulfonic acid base type membrane are used for the temporal and spatial estimations of nitrogen concentration along the anode channels of a polymer electrolyte membrane fuel cell stack. The predicted nitrogen accumulation is then used to estimate the impact of local fuel starvation on stack voltage through the notion of apparent current density. Despite the simplifying assumptions on the water accumulation and membrane hydration levels, the calibrated model predicts reasonably well the response of a 20-cell stack with a dead-ended anode. Specifically, the predicted voltage decay and the estimated gas composition at the anode outlet are experimentally validated using the stack-averaged voltage and a mass spectrometer. This work shows that the crossover of nitrogen and its accumulation in the anode can cause a considerable decay in stack voltage and should be taken into account under high hydrogen utilization conditions.