Carbon Paper Gas Diffusion Layers
Carbon Paper Gas Diffusion Layers (GDL) (e.g. Sigracet, Freudenberg, Toray, etc) tend to be thinner and more brittle than Carbon Cloth Gas Diffusion Layers (e.g. ELAT™, GDL-CT). Each type has a different mass transport, porosity, hydrophobicity, and conductivity.
Papers such as Toray are quite hard and brittle, with very little compressibility. These are good for designs where a tighter tolerance is permitted in the compression and where the thin GDL is a critical factor. Since they are so brittle, care must be taken when handling them in order to not break corners or otherwise damage the GDL.
There are a few other GDL’s which are much more flexible (e.g. Sigracet, Freudenberg) and have a little more compressibility than Toray paper, which in turn makes them much easier to handle. They also do not chip or break as easily as Toray paper while still being available in thin sizes. Some GDLs are very hard and brittle with little compressibility (e.g. Toray); others are much more pliant/flexible but still don’t have much compressibility (e.g. Sigracet, Freudenberg). Also, papers may or may not have Microporous Layers (MPL) and/or additional hydrophobic (Teflon) coatings.
Carbon Cloth Gas Diffusion Layers
The Carbon Cloth based GDL materials (e.g. GDL-CT, ELAT LT 1400) are the most flexible and are generally quite mechanically robust, but are also the thickest. These are typically designed to have a fair amount of compression when assembled in the stack (anywhere from ~10% to 60% of the GDL thickness) and can act somewhat as compressible “springs” in the stack design.
We’ve put together a convenient table listing the properties of some of the more common GDL materials. I hope it is useful in helping you make your selection. Of course, you’re always welcome to AskUs@FuelCellsEtc.com if you need more specific guidance in your application. There are many other GDL material types available as well (as custom options) that we are more than happy to assist you with as well.
Gas Diffusion Layer Comparison Table