Microscopic Observations of Freezing Phenomena in PEM Fuel Cell at Cold Starts

In Polymer electrolyte membrane fuel cells (PEMFCs), the generated water transfers from the catalyst layer to the gas channel through micro channels of different scales in a two phase flow. It is important to know details of the water transport phenomena to realize better cell performance, as the water causes flooding in the high current density conditions and start up problem under freezing temperatures. The keynote speech presents specifics of the ice formation characteristics in the catalyst layer and in the gas diffusion layer (GDL) with photos taken with an optical microscope and a CRYO-SEM. The observation results show that cold starts at −10°C results in ice formation at the interface between the catalyst layer and the micro porous layer (MPL) of GDL, at −20°C most of the ice is formed in the catalyst layer. Water transport phenomena through the micro porous layer and GDL are also a matter of interest, because the role of the MPL is not well understood from the water management angle. The speech will discuss the difference in the water distribution at the interface between the catalyst layer and the GDL arising from the presence of such a micro porous layer.