Water Transport in Gas Diffusion Layers of PEMFCs

Abstract

We present an ex-situ analysis of water transport in the carbon paper gas diffusion layers for PEM fuel cells. We employ florescent imaging that allows us to distinguish liquid water from air through an optical microscope by seeding the water with fluorescent molecules. We were able to infer the vertical location of water and create three-dimensional reconstructions of the water surface by correlating surface height with image intensity. Our study investigated water phase movement in an uncompressed GDL as well as the additional effect of the localized compression that a fuel cell's bipolar plate introduces. The visualizations indicate that localized compression promotes regions of increased wettability. We put forth that the increased wettability results from fractured carbon fibers and the degradation of the PTFE coating.