비파괴 영상법을 이용한 탄소 지지체 부식에 의한 PEMFC 내 MEA 열화 영향 연구

Abstract

In this study, as the first step toward developing a PEMFC diagnostic technique by water distribution images, I have conducted a visualization of internal water distribution before and after the degraded PEMFC unit cell to check the feasibility of the diagnostic technique by water distribution images. In the process of the experiment, the mechanism of water transport suggested by previous studies was verified by the in-situ operation of PEMFC's internal water distribution images. And the liquid-free region in GDBL near the channel and water transport mechanism at CL to MPL were observed. After visualization of water distribution under normal conditions, visualization of degraded internal water distribution based on carbon support degradation was conducted. Heterogeneous contact interfaces such as CL-MPL and MPL-GDBL were severely corroded, and vacant spaces by carbon corrosion locally appeared. Coated PTFE particles on carbon support were lost by carbon surface corrosion and caused hydrophobicity loss of the GDL. As a result, the water path through CL to the channel is getting longer, the capillary pressure that supports water transport before the corrosion was weakened, and locally vacant spaces were flooded by water, so the net pressure that needs to transport water from CL to the channel has been much larger. This process was getting more severe repeating accelerated stress tests, and eventually, corrosion caused catastrophic flooding, and failure of the system was observed and analyzed by water distribution images.