<i>Ex situ</i> Visualization and Network Analysis of Water Distribution in Gas Diffusion Layer of Polymer Electrolyte Fuel Cells by Synchrotron X-Ray Computed Tomography under Water Injection

Abstract

As a rst step towards understanding the e ects of the local micro-structure of gas di usion layers (GDLs) on water accumulation in the GDL pores, ex situ X-ray computed tomography (XRCT) measurements were performed with a water injection device. When polymer electrolyte fuel cells are operated, the liquid water resulting from water vapor condensation adversely a ects their performance because the water clusters obstruct oxygen di usion. The water network constructed from XRCT images indicated that the water clusters could be categorized into three types: fully connected clusters, which started from the microporous layer (MPL) surface and reached the end side of the GDL substrate; MPLconnected clusters, which started from the MPL surface and were dead-ended; and isolated clusters, which did not connect either the MPL surface or the end side of the substrate. The results also suggested that many water paths were created in the substrate by branching, but that only a small portion of the water paths permeated the GDL. The methodology developed in this research is expected to be e ective in comparing GDLs with di erent manufacturing processes.