Pore-Scale Liquid Water Visualization for Understanding Water Transport in Operating Fuel Cells

Abstract

To implement successful water management strategies in polymer electrolyte membrane (PEM) fuel cells, we need to understand how the complex heterogenous nature of the gas diffusion layer (GDL) impacts the pore-scale transport of liquid water. Here, we investigated the 3-D pore-scale liquid water distribution within the cathode GDL via in operando synchrotron X-ray tomography during low current density fuel cell operation to capture the early appearance of liquid water pathways. We found that the invasion of liquid water into the GDL only partially filled certain GDL pores. Liquid water wicked along some GDL fibers, which was attributed to the hydrophilic nature of carbon fiber and the presence of pore-scale mixed wettability within the GDLs. Mixed wettability and partial pore filling should be considered in the pore-scale modeling and design of next-generation GDLs.

Alternative architectures and materials for PEMFC gas diffusion layers: A review and outlook

“…3 shows in-operando images of liquid water at the cathode, obtained via x-ray computed tomography. This type of technique has provided significant insights into the state of liquid water and reactant gases, during operation [17][18][19], and this will enable further development of optimised pore structures for GDLs.…”