Dynamics of fuel cell performance degradation

Dynamics of performance degradation of a PEM fuel cell operating in galvanostatic regime is investigated. Experiments enable to distinguish the three phases of cell degradation: the phase of stable operation, the phase of slow decrease of cell voltage V-cell with time and the phase of V-cell rapid fall. Experiments suggest that the duration of stable operation phase depends on oxygen stoichiometric ratio. To explain this we assume that (i) local degradation interrupts generation of local current and (ii) the rate of local degradation is a jump function of local current density. Dynamics of performance degradation is then determined by the degradation wave, which propagates in the along-the-channel direction towards the channel outlet. Analysis of wave properties enables to explain qualitatively the experimental dependence of cell voltage on time. The degradation of fuel cell performance may thus follow the universal scenario, which includes propagation of the degradation wave. Actual physical mechanism of local current interruption determines the time scales in this scenario. (C) 2003 Elsevier B.V. All rights reserved.