EIS Applications in PEMFCs

The membrane electrode assembly (MEA), which consists of three components (two gas diffusion electrodes with a proton exchange membrane in between), is the most important component of the PEMFC. The MEA exerts the largest influence on the performance of a fuel cell, and the properties of each of its parts in turn play significant roles in that performance. Although all the components in the MEA are important, the gas diffusion electrode attracts more attention because of its complexity and functions. In AC impedance spectra, the proton exchange membrane usually exhibits resistance characteristics the features of these spectra reflect the properties of the gas diffusion electrode. In order to better understand the behaviour of a gas diffusion electrode, we introduce the thin-film/flooded agglomerate model, which has been successfully applied by many researchers to 

The characteristics of a gas diffusion electrode can also be illustrated by the thin-film/flooded agglomerate model. Paganin et al. [4] summarized the parameters that often appear in the impedance spectra of H2/02 and H2/air fuel cells  

Polarization resistance (R,) due to the oxygen reduction reaction (ORR), which is in parallel with the double-layer capacitance (Cdi) 

Distributed resistance due to the ohmic drop in the electrolyte within the catalyst layer 

Limiting concentration gradient of oxygen in the flooded agglomerate 

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This chapter has examined a variety of EIS applications in PEMFCs, including optimization of MEA structure, ionic conductivity studies of the catalyst layer, fuel cell contamination, fuel cell stacks, localized impedance, and EIS at high temperatures, and in DMFCs, including ex situ methanol oxidation, and in situ anode and cathode reactions. These materials therefore cover most aspects of PEMFCs and DMFCs. It is hoped that this chapter will provide a fundamental understanding of EIS applications in PEMFC and DMFC research, and will help fuel cell researchers to further understand PEMFC and DMFC processes. 

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