Abstract
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.
Highlights
Fluorinated polymers are a category of materials that finds application in multiple industry sectors, such as energy, aerospace, construction, automotive, and petrochemical, thanks to their versatility
pulsed gas analysis (PGA) allowed to determine where mass losses were concentrated, and the analysis revealed that most of them are related to the gas diffusion layers (GDL) region (“bulk” losses) and not to the CL (“non-bulk” losses)
PTFE and fluorinated ethylene propylene (FEP) have been widely employed in the fabrication of gas diffusion medium (GDM); other fluorinated materials have been proposed over time as valid alternatives
Summary
Fluorinated polymers are a category of materials that finds application in multiple industry sectors, such as energy, aerospace, construction, automotive, and petrochemical, thanks to their versatility These polymers display remarkable chemical inertness and resistance to acidic and basic attacks, due to the stability of the C-F bond (bond energy = 485 kJ·mol−1 ), high flame resistance, and limited oxidation [1]. They normally feature extended thermal and mechanical stability that prevents the quick arising of degradation mechanisms related to heat cycles [2]. (GDM).It is inserted in-between the catalyst layer and the bipolar plate and is crucial for proper.
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