Understanding the Gas Diffusion Layer in PEM Fuel Cells: Influence of the PTFE Distribution on Ex-Situ Properties and in-Situ Performance

Proton exchange membrane fuel cells (PEMFCs) are being explored for use in transportation, as well as back-up and portable power applications.  A number of key technical and cost challenges remain before they can be used on the commercial scale, however.  The Gas Diffusion Layer (GDL) is one of the most critical components for PEMFC and it is of paramount importance to understand how key properties influence performance and ultimately cost.  This paper focuses on the PTFE distribution in the GDL, but more specifically on how to control the PTFE distribution throughout the GDL, and the impact of the distribution of PTFE in the GDL on key ex-situ properties including porosity, pore size, thickness under compression, resistivity under compression, diffusivity, through-plane permeability and in-plane permeability.  The influence of PTFE distribution on in-situ performance will also be considered under both normal and extreme operating conditions.