The Role of Fluorinated Polymers in the Water Management of Proton Exchange Membrane Fuel Cells: A Review

As the hydrogen market is projected to grow in the next decades, the development of more efficient and better-performing polymer electrolyte membrane fuel cells (PEMFCs) is certainly needed. Water management is one of the main issues faced by these devices and is strictly related to the employment of fluorinated materials in the gas diffusion medium (GDM). Fluorine-based polymers are added as hydrophobic agents for gas diffusion layers (GDL) or in the ink composition of microporous layers (MPL), with the goal of reducing the risk of membrane dehydration and cell flooding. In this review, the state of the art of fluorinated polymers for fuel cells is presented. The most common ones are polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP), however, other compounds such as PFA, PVDF, PFPE, and CF4 have been studied and reported. The effects of these materials on device performances are analyzed and described. Particular attention is dedicated to the influence of polymer content on the variation of the fuel cell component properties, namely conductivity, durability, hydrophobicity, and porosity, and on the PEMFC behavior at different current densities and under multiple operating conditions.