Impedance Spectroscopy Study of the PEM Fuel Cell Cathode with Nonuniform Nafion Loading

Tatyana Reshetenko,Andrei Kulikovsky

doi:10.1149/2.0041711jes

Abstract

We report modeling and experimental study of impedance of the PEM fuel cell cathode with nonuniform ionomer loading. A physics–based model for the high–frequency impedance is developed and analytical solution for impedance is derived. Assuming that the CCL proton conductivity σp exponentially decays from the membrane surface, we fit the model to experimental spectra of the cell measured at the open circuit conditions. Fitting gives the characteristic scale of the σp decay, the average CCL proton conductivity and the double layer capacitance.

Highlights

Fuel cell impedance can, in principle, give parameters of virtually all kinetic and transport processes running in the cell
In PEMFCs at open circuit, this contribution is much less than the cathode catalyst layer (CCL) impedance due to hydrogen crossover[19]
At small currents and in particular at open circuit voltage (OCV), the cell impedance spectrum depends on the processes in the CCL only

Summary

Cdl blt

It is advisable to estimate the right side of Eq 25. A typical current density of hydrogen crossover is about 0.003 A cm−2. The segmented cell system employs close loop Hall sensors (Honeywell CSNN 191) for current sensing and allows us to perform simultaneous measurements of spatial electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and cyclic voltammetry (CV). The Pt/C loading of the anode and cathode electrodes was 0.4 mgPt cm−2. The anode/cathode testing conditions for the EIS measurements were hydrogen/air at 1.0/1.0 l min−1, 100/50% relative humidity and back pressure of 150 kPa. The cell temperature was 60◦C. Spatial EIS are measured simultaneously from 10 segments and from the whole cell, thereby providing good statistics for fitting parameters (see below). Hydrogen crossover current was measured by LSV using a Solartron SI 1287/electrochemical interface as a voltage source. The LSV was performed at the same operating conditions as EIS, while hydrogen and nitrogen were supplied to the reference/counter and working electrodes, respectively. The voltage sweep was applied from 0.1 to 0.4 V vs the reference hydrogen electrode at a scan rate of 0.1 mV s−1

Results and Discussion

Conclusions

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