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 at high current density conditions and give rise to startup problems at freezing temperatures. The paper here, which was originally written for the keynote speech in the ICNMM

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... erence in 2011, 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 the GDL, and that 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 paper discusses 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.