Experimental Study of Thermal Conductivity and Compression Measurements of the GDL-MPL interfacial composite region

The microporous layer (MPL) and the gas diffusion layer (GDL) in a polymer electrolyte membrane (PEM) fuel cell assembly are often treated as separate layers in the literature. However, there exists a considerable interfacial region where the two different materials merge. The MPL consists of fine carbon particles, a binder and a solvent that is applied on top of the fibrous GDL. In the process of coating, the MPL intrudes into the GDL and forms an MPL-GDL-composite region. This region has properties that differ from either of the materials that it consists of. Through-plane thermal conductivity and thickness variation under different compaction pressures were measured for such a composite region of commercial gas diffusion layer (GDL), Freudenberg H1410, and custom-made MPL. Thermal conductivity at 9.2 bar compaction pressure for GDL only is 0.111 +/- 0.009 W K-1 m(-1), for MPL only 0.08 +/- 0.02 W K-1 m(-1), and for the composite region is 0.124 +/- 0.005 W K-1 m(-1). X-ray Computed Tomography images of the materials ascertain the level of penetration for the MPL into the GDL.