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Nowadays, micro-porous layers (MPLs) for polymer electrolyte membrane fuel cells (PEMFCs) are commonly deposited onto gas diffusion layer (GDL) substrates starting from hydrophobic carbon-based dispersions. In this work, different quantities of fluorinated ethylene propylene (FEP), a fluorinated copolymer proven to be superior to polytetrafluoroethylene (PTFE) for a proper water management, were used to make both GDL and MPL hydrophobic. After the identification of the optimal amount of FEP, carboxymethylcellulose (CMC) was also added to gas diffusion media (GDM) to reduce overall ohmic resistance of the whole device and adhesion of MPLs to GDLs. Ex-situ chemical and mechanical accelerated stress tests (ASTs) were carried out to accelerate degradation of materials aiming to assess their durability. The highest quantity of FEP in GDMs led to the best electrochemical and diffusive properties. The presence of CMC allowed reducing overall ohmic resistance due to a better electrolyte hydration. A satisfactory durability was proven since the fundamental properties related to gas diffusion medium, such as wettability, ohmic and mass transport resistances, revealed to be quasi-stable upon ASTs. [ABSTRACT FROM AUTHOR]

Gas diffusion medium (GDM) is a crucial component in proton exchange membrane fuel cells (PEMFCs). Being composed of a gas diffusion layer (GDL) with a micro-porous layer (MPL) coated onto it, it ensures a proper water management due to the highly hydrophobic materials employed in cell assembly. In current commercial applications, the desired water repellent behaviour is usually obtained by using polytetrafluoroethylene (PTFE). In this work, Fluorolink® P56 (Solvay Specialty Polymers, Milan, Italy), a commercially available, anionic, segmented high molecular weight polyfluorourethane with perfluoropolyether groups was extensively evaluated as an alternative to PTFE for micro-porous layer hydrophobization. A change in polymer used is desirable in order to simplify the production process, both in terms of ink formulation and thermal treatment, as well as to get a higher hydrophobicity and, consequently, more efficient water management. Innovative prepared samples were compared to a PTFE-based GDM, in order to assess differences both from morphological and from an electrochemical point of view. [ABSTRACT FROM AUTHOR]