Electrochem. Soc.2014 volume 161,issue 1, F94-F98.
T. Tanuma, S. Kinoshita.
Asahi Glass Co., Ltd., Research Center, Kanagawa-ku, Yokohama-shi, Kanagawa 221-8755, Japan.
Hydrophobicity is generally believed to be key to water management in polymer electrolyte fuel cells (PEFCs). However, we reported that the membrane electrode assembly (MEA) using a hydrophilic micro porous layer (MPL) showed much better performance in a wide range of pressure and humidity conditions than that using a hydrophobic MPL. When operating an MEA, it usually needs to be humidified in order to maintain conductivity of the membrane. Operation without humidification is critical to the commercialization of PEFCs for backup power and automotive applications. We, therefore, evaluated MEAs at 60°C, at the H2/air stoichiometric ratio of 1.4/5.0, without humidification, in addition to the normal conditions of 80°C, 100 & 30%RH. We found that the MEA employing a gas diffusion electrode (GDE) method on the hydrophilic MPL showed the best performance under a very dry condition, suggesting that the firm interface between the catalyst layer and the MPL plays a crucial role in determining MEA performance, particularly under dry conditions
This paper provides guiding principles in the design of membrane electrode assemblies (MEAs) for PEFCs. Although micro-porous layers (MPLs) containing polytetrafluoroethylene (PTFE) are usually employed in commercially available gas diffusion layers (GDLs), we have proven that an MEA using a hydrophilic MPL shows much better performance both in dry and wet operating conditions. Manufacturing cost of GDLs could be reduced by not using PTFE in the MPL, and so dispensing with the post heat-treatment process that removes the dispersant used in the PTFE dispersion. In this paper, typical cathode fabrication methods, (a) gas diffusion electrode (GDE), (b) direct coating to the membrane, (c) decal transfer to the membrane, were compared. It was found that the MEA employing a GDE method on the hydrophilic MPL composed of ionomer and carbon fiber was the best, and that the interface between the catalyst layer and the MPL, which was formed by way of a coating of catalyst ink on the MPL, was more favorable than that formed by way of a hot-pressing method.