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Synchrotron X-ray radiography was utilized to visualize the liquid water distribution in a fuel cell with an active area of 0.48 cm 2 with an effective spatial resolution of 10 μm. Water content was measured in the gas diffusion layers (GDLs), where microporous layer (MPL) thicknesses ranged between 0 and 150 μm. The distribution of liquid water in a substrate-free polymer electrolyte membrane (PEM) fuel cell with a 50 μm-thick MPL was also determined. It was observed that the presence of an MPL significantly reduced the water content at the interfacial region between the catalyst layer and GDL, and increasing the thickness of the MPL led to a reduction of liquid water accumulation at the interface between the substrate and MPL.

Synchrotron X-ray radiography, due to its high temporal and spatial resolutions, provides a valuable means for understanding the in operando water transport behaviour in polymer electrolyte membrane fuel cells. The purpose of this study is to address the specific artefact of imaging sample movement, which poses a significant challenge to synchrotron-based imaging for fuel cell diagnostics. Specifically, the impact of the micrometer-scale movement of the sample was determined, and a correction methodology was developed. At a photon energy level of 20 keV, a maximum movement of 7.5 µm resulted in a false water thickness of 0.93 cm (9% higher than the maximum amount of water that the experimental apparatus could physically contain). This artefact was corrected by image translations based on the relationship between the false water thickness value and the distance moved by the sample. The implementation of this correction method led to a significant reduction in false water thickness (to ∼0.04 cm). Furthermore, to account for inaccuracies in pixel intensities due to the scattering effect and higher harmonics, a calibration technique was introduced for the liquid water X-ray attenuation coefficient, which was found to be 0.657 ± 0.023 cm(-1) at 20 keV. The work presented in this paper provides valuable tools for artefact compensation and accuracy improvements for dynamic synchrotron X-ray imaging of fuel cells.

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