Selective Visualization of Water in Fuel Cell Gas Diffusion Layers with Neutron Dark-Field Imaging

Abstract

Visualizing the water distribution in porous gas diffusion layers (GDLs) of operating polymer electrolyte fuel cells (PEFCs) is indispensable to understand the impact of water management on performance. For this purpose, neutron and X-ray transmission imaging have been used for nearly two decades. Certain limitations inherent to attenuation based imaging methods can be overcome by applying neutron dark-field imaging, which has the ability to selectively visualize structures in the micrometer size range. In this study, we compare dark-field images and transmission images of GDLs filled with water through an injection channel. The high contrast of the dark-field value between a heavy water filled and a dry GDL is suitable to reveal water distribution patterns in the GDL. The water present in the 1 mm wide water injection channel of the test device does not alter the dark-field signal, as this technique is selectively sensitive to microstructures. Therefore, neutron dark-field imaging can be applied for the selective analysis of the water distribution in the GDL overlapping with channel water. In addition to the selective visualization of water distributed in a GDL, we show that neutron dark-field imaging can also be used to visualize GDL damages.

Freeze-Drying with Structured Sublimation Fronts—Visualization with Neutron Imaging

“…We used maltodextrin DE12 Glucidex from Roquette (France) ( Table 1). Maltodextrin was solved in deuterium oxide (heavy water, D 2 O), which has an attenuation coefficient about one order of magnitude lower than H 2 O (neutron attenuation coefficient (at 4.1 Å) is 0.7 cm −1 for D 2 O and 5.4 cm −1 for H 2 O [31]) and allows for a better contrast between frozen water and the surrounding material in image processing. The change in solvent was expected to have no other major impact on the physics of the drying experiment.…”

Enhanced Water Management in PEMFCs: Perforated Catalyst Layer and Microporous Layers

“…Neutron imaging has been used as a state‐of‐the‐art technique for visualizing liquid water in operating PEMFCs with a high special resolution . Several groups have successfully employed neutron tomography to advance the understanding of the relationship between liquid water behavior and the complex structural heterogeneity of porous media …”

Scalable Neutron Imaging Systems at Compact Sources

“…The specific high sensitivity of neutrons for some light elements, namely hydrogen and lithium, make neutrons and especially neutron imaging an outstanding research and development tool in the key field energy conversion techniques especially with respect to fuel cells, hydrogen storage and batteries, but also nuclear safety. These also spur industrial interest and applications and examples are numerous in recent literature [5][6][7][8][9][10][11][12][13].…”