Influence of liquid water accumulation on the impedance of a PEM fuel cell operating in dead end mode: Physical modeling and experimental validation

The dead-end mode operation of a PEM fuel cell reduces the reactants consumption and the system's complexity, but also decreases its performance due to the accumulation of liquid water, which must be purged periodically. Despite extensive use of the EIS technique in studying PEM fuel cells' internal processes, the inherently transient nature of dead-end mode operation has challenged the application and interpretation of this technique. In this paper, a novel analytical model is proposed to physically investigate the effect of liquid water accumulation on the impedance of a PEM fuel cell in dead-end mode operation. The model is well validated against experimental polarization curves and impedance diagrams in various operating conditions by employing a two-step fitting procedure. The findings of the model indicate the constant presence of a large amount of liquid water in the fuel cell due to the dead-end operation. Additionally, the buildup of liquid water reduces the active area of the catalyst layer and the effective oxygen diffusion coefficient in GDL, increasing both the charge and mass transfer resistances. Finally, with its low computational cost, the developed analytical model can provide a suitable framework for purposes such as fault diagnosis and degradation prognosis.