Heterogeneous Through-Plane Porosity Distributions for Treated PEMFC GDLs I. PTFE Effect

To the authors' best knowledge, this is the first parametric investigation of the effect of polytetrafluoroethylene (PTFE) treatments on the heterogeneous through-plane local porosity distributions of PTFE-treated gas diffusion layers (GDLs) for polymer electrolyte membrane fuel cells (PEMFCs). In this work, the through-plane porosity distributions of uncompressed PTFE-treated paper GDLs were measured from high resolution microscale computed tomography visualizations. We analyzed paper GDLs with varying thicknesses and PTFE treatments. When compared to untreated GDL porosity distributions, we observed that the application of PTFE resulted in decreased local porosities near the surface regions and non-uniform distributions of PTFE throughout the material. The rate of porosity decrease with increasing PTFE application is in agreement with the literature. The changes to the overall through-plane porosity distributions are more significant than the changes to the average bulk porosities, which are attributed to batch-specific manufacturing variations. This work provides new insight into the effects of PTFE treatments on GDL through-plane porosity distributions, which are expected to inform future PEMFC models. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3594578] All rights reserved.