Design of properties and performances of innovative gas diffusion media for polymer electrolyte membrane fuel cells

Gas diffusion medium (GDM) is a crucial carbon-based component for water management in polymer electrolyte membrane fuel cells (PEMFCs). GDM consists of a macro-porous substrate, which is usually a carbon cloth or carbon paper, coated with a thin micro-porous layer (MPL). Traditionally, PTFE is used as hydrophobic agent and binder. In this work, three different GDMs were prepared using fluorinated polymers (polytetrafluoroethylene-co-hexafluoro-propylene (FEP), polytetrafluoroethylene-co-perfluoroalcoxy vinyl ether (PFA) and a fluorinated polyurethane based on perfluoropolyether blocks (PFPE)) in order to replace conventional PTFE as hydrophobic agent, which was used as reference. Inks composition and rheological behaviour were fixed in order to apply the blade coating technique for MPL deposition. These polymers allowed to decrease temperature during thermal treatments with respect to the one necessary for treating PTFE-based MPLs. Moreover, superhydrophobic layers were obtained for all the samples and the final electrical performances of the whole fuel cell system were improved with respect to the ones reached with PTFE-based samples. In particular, FEP allowed to reduce significantly mass transfer resistances in the operating conditions of the fuel cell.