Investigating the Effect of Channel Width and Surface Wettability on Liquid Water Content in PEMFCs Using Synchrotron Radiography
In this study, a PEM fuel cell, with an active area of 0.48 cm2, was designed for synchrotron imaging to acquire through-plane radiographs of the cell. Using Toray GDLs coated with an MPL (TGP-H-60), each fuel cell experiment was performed at specified operating conditions controlled with a Scribner 850e test station. Two different channel geometries were studied: one with a channel width of 0.6 mm; the other, 0.2 mm. In addition, the effect of channel wettability was also investigated. For each channel geometry, two sets of bipolar plates were prepared; they were either coated with a hydrophilic or hydrophobic coating.
Visualizations of the dynamic liquid water content in operating fuel cells were performed at the Biomedical Imaging and Therapy – Bending Magnet (05B1-1) beamline at the Canadian Light Source Inc. (Saskatoon, Canada) using conventional absorption imaging. A monochromatic X-ray beam set to an energy level of 18 keV was used to acquire two- dimensional radiographs. By applying the principles of the Beer-Lambert law, the raw radiographs were processed to isolate the water content, in the form of a water thickness distribution.
The results of the current study aim to improve the understanding of how the channel surface wettability and channel dimensions influence the water management of PEM fuel cells. This is important as the channel water morphology can have an effect on the GDL water distribution, which is linked to the overall fuel cell performance. As the interface between the liquid water in the GDL and the liquid water in the channel is not fully understood, this study will shed light on interface effect by taking advantage of the fine spatial and time resolutions of the synchrotron X-ray radiography.
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