Gas permeability, wettability and morphology of gas diffusion layers before and after performing a realistic ex-situ compression test

The through-plane gas permeability, wettability, thickness and morphology have been investigated before and after a compression test, which is important to the GDL design. The compression tests were designed to simulate the initial assembling compression and the cycles of loading and unloading arising as a result of hydration/dehydration of the membrane. Owing to the presence of the microporous layer (MPL), the results show that the coated gas diffusion layers (GDLs) are slightly more resistive to deformation than the uncoated GDLs. Amongst all the tested carbon substrates (i.e. the uncoated GDLs), Toray carbon substrate was found to show the least reduction in thickness and gas permeability after compression, and this was attributed to its relatively high density and low porosity. As for the coated GDLs, the level of MPL penetration for one of the tested GDLs (i.e. SGL 35BC) was significantly higher than that of the other GDL (i.e. SGL 34BC), resulting in substantially less reduction in thickness and gas permeability of the former GDL after compression. Finally, the contact angles of all the tested GDL materials were found to decrease after compression due to the decreased surface roughness.