The Role of Native Binder in Controlling the Polytetrafluoroethylene Distribution in Gas Diffusion Layers for Proton Exchange Membrane Fuel Cells

Journal article, 2026

Gas diffusion layers (GDLs), a critical component in (Formula presented.) / (Formula presented.) proton exchange membrane fuel cells (PEMFCs), are commonly treated with polytetrafluoroethylene (PTFE) for controlling hydrophobicity. However, the influence of the GDL's native microstructure on the final PTFE spatial distribution is still poorly understood. We compare the PTFE distribution in a dry-laid GDL containing a native binder with that in a wet-laid, binder-free GDL. To analyze the GDL microstructure, we perform scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and confocal Raman spectroscopy, with (Formula presented.) resolution at identical locations. We find that the binder acts as a scaffold for PTFE agglomerates to deposit, independent of the fiber locations. We show that PTFE deposited on the binder phase results in a significantly lower effect on the dry oxygen transport resistance, measured using a limiting current method at low oxygen concentration.