Investigation on the effect of microstructure of proton exchange membrane fuel cell porous layers on liquid water behavior by soft X-ray radiography

In order to investigate the effect of microstructure of PEMFC porous layers on the liquid water transport, liquid water accumulation and discharge behavior in the operating PEMFC was visualized by laboratory-based soft X-ray radiography. The utilization of low energy X-ray made it possible to visualize the liquid water behavior in the PEMFC with the spatial resolution of 0.8 μm and the temporal resolution of 2.0 s frame⁻¹, and the cross-sectional imaging can resolve the each components of the PEMFC. The visualization results showed that adding the MPL prevents the accumulation of liquid water in the substrate layer from contacting and forming the liquid water film on the catalyst layer. Furthermore, it was found that the liquid water distribution in the carbon paper and the carbon cloth GDL was completely different. The liquid water in the carbon cloth GDL concentrates at the weaves of fiber bundle and was effectively discharged to the channel. These visualization results suggested that the microstructure of the PEMFC porous layers strongly affect the liquid water behavior in the PEMFC, and the detailed understanding of the pore structures and the network of liquid water is essential for keeping the oxygen transport path to the catalyst site.