Gas Diffusion Layers (GDLs) are an important component of PEM fuels cells that significantly enhance the mixing and flow homogenization of the reacting species from the flow channels to the catalyst surface of the Membrane Electrode Assembly (MEA). They offer excellent structural strength combined with high electrical and thermal conductivity in the form of a high porosity medium.
GDLs are typical made of unwoven carbon fiber paper produced from Polyacrylonitrile (PAN) filaments with a typical diameter of 8um with a standard paper-making process. The final product is graphitized by heating at temperatures above 2000C and treated with Teflon to increase its hydrophobicity for enhanced water management.
For the microscale study and characterization of GDLs, we perform X-ray micro-ct scans of commercially available carbon paper with a spatial resolution down to 0.66um. The reconstructed skeleton is then used with advanced numerical methods to measure the transport properties of the material, such as species diffusivities, permeabilites and thermal/electrical conductivities. (Related work)