Raman Spectroscopic Mapping of the Carbon and PTFE Distribution in Gas Diffusion Layers

Raman microspectroscopy was used to gather spatially resolved chemical information on the carbon and poly(tetrafluoroethylene) (PTFE) distribution of fuel cell gas diffusion layers (GDL). GDLs with varying PTFE content were imaged over areas of 1,000 μm × 1,000 μm and it was found that the distribution of concentrated PTFE regions on the surface of the GDLs and morphology of the carbon fibre paper was readily observed. Spectroscopic measurements with point‐by‐point resolutions varying between 10 and 500 μm were performed on samples having 1.8–44 wt.% PTFE before and after the PTFE was sintered. The average PTFE signal detected on the surface of the GDLs increased monotonically for both unsintered and sintered GDLs with increasing bulk PTFE loading. The unsintered GDLs had higher PTFE signals on their surface compared to sintered GDLs and showed more concentrated PTFE regions in the mapping experiments.