PEFCs interfacial properties

This introductory chapter provides a brief outline and history of the PEFC technology, and important requirements and aspects in the development of polymer membranes for fuel cells. To obtain materials that meet specific requirements, the relationship of composition/structure and the properties has to be estabUshed. For the preparation of the membrane electrode assembly, it is important to understand the interfacial properties between membrane and electrodes. 

The focus of this section is on the corrosion phenomena of the GDL substrate graphite fibers driven by solid-liquid surface chemical interactions and surface energetics. Particular importance is assigned to uncoated areas of fibo s by hydrophobic fluoropolymer and interfacial zones between fiber and fluoropolymer. Since Teflon products such as PTFE and FEP are known to have excellent thermal resistance, electrochemical corrosion stability, chemical durability, and mechanical properties, the GDL and MPL fluoropolymer phase is not considered to be vulnerable in a PEFC operating enviromnent. 

Capillary pressure increases as pore radius decreases, so that the very small pores in a catalyst layer can have very high capillary pressure. It is important to emphasize that, even for very homogeneous porous media, these relationships cannot be applied on a microscopic level to the entire media due to the complex and highly varied pore structure in PEFCs, and attempts at modeling the effects are considered global and meant to capture the qualitative trends using bulk parameters derived that are representative of the bulk media. Therefore, these parameters must be derived experimentally and are highly dependent on material properties, and in fuel cells, interfacial effects are not treated in the... 

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