Effects of Structure and Hydrophobic Treatment on Water Transport Behaviour in PEM Fuel Cell Gas Diffusion Layers

This paper examines the effects of structure and wettability on water transport behaviour in PEM fuel cell gas diffusion layers (GDLs). Different GDL materials, including carbon cloth and carbon paper with and without PTFE and MPL coatings, were used in this study. The breakthrough pressure of liquid water, water flow rate and water retention in the GDL were measured. For the GDL with and without MPL, the results indicate that the paper GDLs require higher breakthrough pressure than the cloth ones. Compared to the untreated GDL, applying PTFE on the GDL increases breakthrough pressure up to 1.5 times while it decreases water flow rate and water retention up to about 3.8 and 0.5 times respectively, over the tested conditions. The results also show that applying MPL on the GDL surface has greater impact on breakthrough pressure than applying PTFE. Liquid water requires up to about 4 times greater pressure to break through the other side of the GDL with the MPL. By applying MPL, the amount of water retention and flow through the GDL also reduced greatly, to almost zero. In addition, the results suggest that the GDLs are degraded after being exposed to water, which causes a significant decrease in breakthrough pressure and an increase in water retention.