Effect of compression on liquid water transport and microstructure of PEMFC gas diffusion layers

This work explores how the degradation of the gas diffusion layer (GDL) under compression contributes to the formation of preferential pathways for water transport. Fluorescence microscopy is used to provide ex situ visualization of liquid water transport through the GDL placed beneath an optically transparent clamping plate. Transient image data obtained with a CCD camera indicates that areas of compression in the GDL coincide with preferential pathways for water transport and break-through. Preferential flow of water through the smaller pores resulting from GDL compression is contrary to the expected behaviour in a hydrophobic medium, and this suggests a loss of hydrophobicity. Scanning electron microscopy (SEM) is used to investigate the effect of compression on the morphology of the GDL. These SEM images show that compressing the GDL causes the breakup of fibers and, indeed, deterioration of the hydrophobic coating.