Water management inside PEFC is one of the most important matter of studies for the improvement of the performance. Although it is considered that the clarification of transport mechanism of water inside PEFC will guide further development of GDL, there is a divergence of report about water transport mechanism in the past literatures. In the study of Deevanhxay et al.¹, for instance, it is reported that there are clear liquid water paths from catalyst layer ( CL ) to GDL through MPL. While in the study of Naito et al.², such a paths are not observed, and they suggests that water transport to GDL from CL is vapor form. Although they used different GDL, there seems to be consistent parameters governing these differences. As such, this study focuses on local MPL thickness, presence of crack and distribution of PTFE, and discusses correlation between these parameters and a mechanism of water transport inside GDL. Figure represents derived interfaces inside MEA and liquid water distribution at 1.5A/cm². In the cathode side, it is found that MPL thickness is not uniform but has relatively large undulation. It is also shown that most of liquid water accumulates inside GDL, while in a thinner MPL region marked by dashed circle, clear liquid water accumulation exists. In the presentation, we will show more comprehensive and detailed mechanisms by focusing on effects of crack presence and PTFE distribution using a result of CT measurement of MEA.

1. Deevanhxay, T. Sasabe, S. Tsushima, S. Hirai, J. Power Sources, 230, 38 (2013).
2. Naito, T-C. Jao, T. Yoshida, T. Sasabe, K. Kawamura and S. Hirai, ECS Trans., 80, 425 (2017).