Understanding Liquid-Water Management in PEFCs Using X-Ray Computed Tomography and Modeling

Optimal liquid-water management is essential for commercializing polymer-electrolyte fuel cells (PEFCs), especially those with next-generation material sets. At low operating temperatures there is a need to remove liquid water from the cathode electrode where it can impede reactant transport. Optimization of water transport and removal requires a careful design consideration for the porous carbon components, specifically the gas-diffusion layers (GDLs). These heterogeneous materials serve a multifunctional purpose of conducting electrons and heat in the solid phase, providing structural support to the membrane and electrodes, and delivering reactants to the electrode and removing product water. Two-phase transport inside the GDLs, especially during operation, is complex and requires detailed knowledge of a given GDLs’ morphology and transport properties. In this talk, we will elucidate the GDL’s morphological properties using synchrotron-based X-ray micro computed tomography (XCT) and study in-situ water-distributions for different materials. Conditions studied include varying liquid pressure, gas-channel flow-rate, and land-channel compression. The XCT studies are complemented with two-dimensional modeling studies to gain an understanding of liquid-water transport under in-operando conditions.

Acknowledgement

This work was funded by Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231, program manager Donna Ho. This work made use of facilities at the Advanced Light Source (ALS), supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy.