Characterization of HT-PEM membrane-electrode-assemblies

Abstract

his chapter describes the most commonly used electrochemical measurement techniques to characterize HT-PEM membrane electrode assemblies (MEAs). Moreover, it will be shown what kind of information can be subtracted from each technique in order to provide a correct diagnosis of the HT-PEMFC behavior. Detailed descriptions of test procedures and methodology routines for each one of the electrochemical techniques are important for the comparison of data between different working groups is not always possible, thus leading to the need of standardized test protocols. The described test procedures and routines have already been verified in two European Projects. Micro-computed tomography X-ray technique has been introduced as a rather new post-mortem three-dimensional imaging method of the specimens under investigation. Therefore, μ-CT imaging enables the nondestructive characterization of usually hidden interfaces in HT-PEM MEAs that cannot be done by conventional microscopy techniques. MEA contact pressure plays an important role for degradation of MEA materials that can affect performance and lifetime of the HT-PEMFC. Thus, electrochemical and ex situ imaging techniques have jointly been used to investigate the effect of contact pressure increase as well as contact pressure cycling to verify the state-of-the-art of HT-PEM technology in different commercial MEAs. The importance to define long-term test routines will be discussed in the last section of this chapter. Long-term testing should reproduce real operation conditions and determine the issues to identify, understand, and minimize degradation mechanisms that limit the applicability of HT-PEM technology nowadays in systems ready for the market.