In Situ High-Resolution Neutron Radiography of Cross-Sectional Liquid Water Profiles in Proton Exchange Membrane Fuel Cells

Abstract

High-resolution neutron radiography was used to image an operating proton exchange membrane fuel cell in situ. The crosssectional liquid water profile of the cell was quantified as a function of cell temperature, current density, and anode and cathode gas feed flow rates. Detailed information was obtained on the cross-sectional water content in the membrane electrode assembly and the gas flow channels. At low current densities, liquid water tended to remain on the cathode side of the cell. Significant liquid water in the anode gas flow channel was observed when the heat and water production of the cell were moderate, where both water diffusion from the cathode and thermal gradients play a significant role in determining the water balance of the cell. Within the membrane electrode assembly itself, the cathode side was moderately more hydrated than the anode side of the assembly from 0.1 to 1.25 A cm −2 . The total liquid water content of the membrane electrode assembly was fairly stable between current densities of 0.25 and 1.25 A cm −2 , even though the water in the gas flow channels changed drastically over this current density range. At 60°C, the water content in the center of the gas diffusion layer was depleted compared to the membrane or gas flow channel interfaces. This phenomenon was not observed at 80°C where evaporative water removal is prevalent.

Improved modeling and understanding of diffusion-media wettability on polymer-electrolyte-fuel-cell performance

“…However, most current simulations and some experimental ones [42] suggest that the water saturations do not reach such high levels under steady-state performance.…”

“…Neutron imaging has also shown complex water profiles in the GDL [42,50], which are probably due to nonuniform properties and PCI flow effects as discussed in the introduction. It is unknown how much error the above assumption causes.…”

“…In addition to ex-situ analyses, neutron [42][43][44][45] and other imaging techniques [46][47][48][49] have begun to allow one to see the in-situ DM water profiles with increasingly better resolution.…”

Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

“…In the first case, it is possible to differentiate between the water content in the cathode and the anode GDL [29][30][31][32][33][34][35][36]. In the second case, it enables investigations of the effect of different designs, components, and operating conditions on the water distribution across the lateral extent of the cell [37][38][39][40][41][42][43][44][45][46][47].…”

Non destructive testing of medium and high voltage cables with a transportable radiography system

“…In contrast to X-rays, thermal neutrons are particularly attenuated by certain light materials (H, Li, B, C,) whereas they penetrate easily through heavy elements (Pb, Bi, U, W) [6]. The technique is widely used in security applications, in automotive and aerospace applications, engineering studies and industry in order to determine structural defects, geology, medicine and biological research, [7][8][9][10][11][12][13][14][15][16][17]. In the high voltage cables there are simultaneously more than one light material (usually XLPE and PVC) which is practical impossible to distinct with the traditional X-ray systems [18][19][20].…”