On the estimation of high frequency parameters of Proton Exchange Membrane Fuel Cells via Electrochemical Impedance Spectroscopy

• The estimation of impedance parameters of H2/air PEMFC with Randles EEC is discussed.
• Sensitivity analysis gives validity domain for estimation of cathode parameters.
• EIS allows clear separation between charge and mass transfer voltage losses.
• Cathode kinetics parameters were estimated from the charge transfer resistance.
• EIS is more precise and fast than steady-state methods for cathode characterization.

This paper is a discussion on the estimation of impedance parameters of H2/air fed Proton Exchange Membrane Fuel Cells (PEMFC). The impedance model corresponds to the Randles electrical equivalent circuit accounting for charge separation and transport processes in the cathode catalyst layer, as well as for oxygen diffusion through the backing layer. A sensitivity analysis confirms that the cathode parameters are not correlated and that the consideration of the anode has no significant impact on the estimation of their values. In addition, it is shown that the diffusion parameters have a significant impact in the low frequency domain only, at least with this model. The parameters characterizing charge separation and transport processes at the cathode can thus be estimated with the high frequency impedance data, independently of the oxygen transport model. Consequently, even in the absence of a fully validated oxygen transport impedance, EIS can be used as an alternative method (to classical steady-state methods) for the estimation of the parameters characterizing the cathode reaction: the Tafel slope b, the charge transfer coefficient α and possibly, the exchange current density j0. This reduces significantly the measuring time while enhancing the accuracy by comparison with steady-state methods.