2022 Volume 55 Issue 1 Pages 71-76
As a first step towards understanding the effects of the local micro-structure of gas diffusion 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 affects their performance because the water clusters obstruct oxygen diffusion. 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; MPL-connected 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 effective in comparing GDLs with different manufacturing processes.