Selected examples of impedance-analysis applications

FIGURE 12-1 Representative equivalent circuit for fresh, intact coating 

If a simple layer-by layer-dissolution of a pol3mier takes place, the film thickness will decrease, the measured film capacitance will increase. 

FIGURE 12-3 A. Nyquist B. Bode plots for degraded coating 

For degraded porous films, the discussion in Section 7-5 is generally valid. The high-frequency semicircle is largely related to the film porosity and independent of the kinetics of the Faradaic process at the electrode, while the 

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EIS has played an important role in fuel cell technology development, as one of the most important research tools for fuel cell diagnosis. EIS can help to identify the contributions from different components or processes to the total impedance of a PEM fuel cell. Such information is very helpful for understanding the fundamental processes within the fuel cell, the performance-structure relationships, and the contributions of various components to performance loss, as well as the associated failure modes and mechanisms EIS thus assists with fuel cell design optimization and selection of the most appropriate fuel cell operating conditions. In this chapter, we will present some typical examples of the applications of EIS in PEM fuel cell research, and an overview of EIS spectra analysis. 

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