Anode Monitoring By Electrochemical Impedance Spectroscopy in Polymer Electrolyte Membrane Fuel Cells

摘要

Although widely used to study the operation of Polymer Exchange Membrane Fuel Cells (PEMFC), Electrochemical Impedance Spectroscopy (EIS) remains a complex tool: experimental data are somewhat delicate to interpret because of the wide range of physical phenomena occurring in Membrane Electrode Assemblies (MEA) and in the flow field plates. Therefore, impedance models are often based on oversimplified equations or conversely, include too many correlated parameters. A typical example of the complexity of the phenomena governing fuel cell electrical behavior are the oscillations of oxygen concentration resulting from the measuring signal, that propagate along the gas channels and makes more difficult the interpretation of the low frequency loop. In addition, most of the impedance models assume Fickian oxygen diffusion although, at least in fuel cells fed with air, Stefan-Maxwell equations should be used as in most stationary models. In this regard, oxygen diffusion and thus the low frequency impedance are strongly dependent on the overall convective flux and as a result, on water management.