Effects of polytetrafluoroethylene treatment and compression on gas diffusion layer microstructure using high-resolution X-ray computed tomography

• The microstructure of a TGP-H-120 gas diffusion layer (GDL) was investigated using high resolution X-ray CT technique.
• A sample holder was designed to investigate the effects of non-uniform compression pressure.
• Anisotropic microstructure, nonuniform PTFE distribution, and significant microstructural change with compression were seen.
• At 3 MPa, 16% reduction is bulk porosity and a large penetration of GDL into the channel (132 μm) was observed.

The microstructure of a TGP-H-120 Toray paper gas diffusion layer (GDL) was investigated using high resolution X-ray computed tomography (CT) technique, with a resolution of 1.8 μm and a field of view (FOV) of ∼1.8 × 1.8 mm. The images obtained from the tomography scans were further post processed, and image thresholding and binarization methodologies are presented. The validity of Otsu's thresholding method was examined. Detailed information on bulk porosity and porosity distribution of the GDL at various Polytetrafluoroethylene (PTFE) treatments and uniform/non-uniform compression pressures was provided. A sample holder was designed to investigate the effects of non-uniform compression pressure, which enabled regulating compression pressure between 0, and 3 MPa at a gas channel/current collector rib configuration. The results show the heterogeneous and anisotropic microstructure of the GDL, non-uniform distribution of PTFE, and significant microstructural change under uniform/non-uniform compression. These findings provide useful inputs for numerical models to include the effects of microstructural changes in the study of transport phenomena within the GDL and to increase the accuracy and predictability of cell performance.