Impact of the Microporous Layer on Gas Diffusion Layers with Patterned Wettability I: Material Design and Characterization

Abstract

Gas diffusion media is one of the main components affecting the water management in polymer electrolyte fuel cells, which is key for a high and stable performance. Building up on our previously designed gas diffusion layers (GDLs) with patterned wettability, we included in this study customized microporous layers (MPLs) with the target to enhance the effect of hydrophilic water pathways and reduce mass transport losses. The MPLs were modified by introducing “weak points” using electron induced radiation grafting or local mechanical perforation, in order to canalize the water injection to the hydrophilic pattern of the GDL. We describe the techniques used for gas diffusion media modification, their limitations and their influence on water distribution. We also study in detail the impact of different water injection methods on water distribution, in particular comparing capillary pressure water injection to electrochemical water production. The important differences observed between these two methods, were attributed to the absence of hydraulic connection between the water injection points in the latter case. Although the ex situ characterization shows that the local MPL modifications were successful, the targeted canalization of water injection was not observed, calling for future MPL modifications with an improved lateral transport.