This invention is based on an innovative process that creates an extremely thin and durable "wet-proof" surface on the interior of gas diffusion media such as the type used in PEM fuel cells.
A Proton Exchange Membrane (PEM) fuel cell depends on proper water management to obtain high power density and energy efficiency. During operation, liquid water is generated in the fuel cell. When it is not properly removed, its accumulation leads to poor fuel cell performance. To address this problem, the gas diffusion media (GDM) in a fuel cell are treated with polytetrafluoroethylene (PTFE) to wet-proof the substrate surface.
In conventional coating methods, as the PTFE level is increased to ensure complete surface coverage, it builds up in the pores. This leads to a phenomenon called "pore-plugging", which results in lower gas transport rate and poorer fuel cell performance. Furthermore, this coating suffers from durability issues because the PTFE coating can detach due to physical changes like expansion, contraction and shear force by fluid flow. To overcome this problem, a new process has been developed to create an extremely durable "wet-proof" gas diffusion layer that does not affect the pore volume and pore sizes of the porous media.
This technology is aimed at improving the GDM components of PEM fuel cell applications such as hydrogen-powered vehicles. It would also provide benefits in flow batteries and any other application where wet-proofing of an electrode is needed.
In this technology, the GDM is directly fluorinated in the interior at the atomic level to create durable wet-proof surfaces. The outer major surfaces stay free of fluorination to maintain electrical connectivity. The patent-pending innovation includes the product plus multiple methods of fabrication.
Development of this technology should result in PEM fuel cells with improved life/durability, as well as improved performance. The chemical means used to bond fluorine with the interior of the GDM achieves two substantial benefits. First, since the wet proof surface is formed of fluorine atoms that react chemically with the first layer of carbon atoms on the surface of the substrate, the wet proof coating is substantially stronger and more durable. Second, the coating thickness is minimized, resulting in enhanced flow through the GDM and optimized fluorine usage.
Our innovation leads to GDM with improved durability, porosity, and hydrophobicity not obtainable with conventional PTFE processes. It is also expected to be more cost effective than the current process because it is simpler, less prone to impurities and contaminations, and uses fewer environmentally harmful fluorinated materials.