Chapter 7. The Role of Perfluoropolyethers in the Development of Polymeric Proton Exchange Membrane Fuel Cells

Abstract

In the field of renewable energy, proton exchange membrane fuel cells (PEMFCs) are the devices that have most benefited from the unique characteristics of fluorinated materials. Fluorinated polymers are present in many parts of the cell, such as the membrane, the catalytic layers and the gas diffusion layers (GDLs). In particular, GDLs promote the distribution of the gaseous reagents from the bipolar plates to the catalyst layer and regulate the correct water management that is necessary to avoid drying of the membrane and accumulation of liquid water inside the cell. Therefore, the conductive carbonaceous materials composing GDLs are usually treated with a hydrophobic material. An innovative methodology to confer stable hydrophobicity on carbonaceous materials involves the use of perfluoropolyethers (PFPEs). PFPEs can either be deposited as a neutral or functional polymer on the surface of carbonaceous materials or linked by thermal treatment with PFPE peroxide. PFPE chains have the typical properties of perfluorinated polymers, such as chemical stability, thermal stability and high hydrophobicity, but also some peculiar features such as a liquid physical form and high gas permeability. The application of PFPEs can be exploited in order to develop conductive hydrophobic composite materials with high performance in PEMFCs.