Fabrication of gas diffusion layer (GDL) containing microporous layer using flourinated ethylene prophylene (FEP) for proton exchange membrane fuel cell (PEMFC)

Abstract

Proton exchange membrane fuel cell (PEMFC), also known as polymer electrolyte membrane fuel cell, is the type of fuel cell being developed for transport applications as well as for stationary and portable applications. Typical PEMFC consists of several essential components, and gas diffusion layer is considered to be one of the most important components. Gas diffusion layer (GDL) in PEMFC works as a protective layer for the delicate catalyst structure, provides good mechanical strength and easy gas access to the catalyst, and improves the electrical conductivity. Consequently, GDL of PEMFC should have low electronic resistivity, specific surface to enhance good electronic contact and proper hydrophobicity for each application. The properties of the conventional GDL’s can be improved by implementing microporous layer instead of common thick porous support layer. Microporous layer (MPL) reduces the contact resistance between catalyst layer and macroporous substrate. The main purpose of using MPL is the water management, as they provide effective wicking of water from the cathode catalyst layer into the diffusion media, thus improving the overall performance of the PEMFC. In this study, the fabrication of GDL containing microporous layer (MPL) made from the slurry of FEP (Flourinated Ethylene Prophylene) mixed with carbon black was investigated in detail. The properties of FEP, such as low friction and nonreactivity, are same as those of PTFE; however FEP has few advantageous points than PTFE. FEP can be formed into desired shapes more easily; its softer than PTFE (melting temperature of FEP is 260°C); it is highly transparent and resistant to sunlight. The microstructure of the developed GDL containing MPL was analyzed by SEM/EDX by observing the surface and cross section of the specimen. The properties such as viscosity, electric conductivity, density, porosity were measured. The amount of carbon loading to get optimum thickness was defined, and the performance of the fuel cell using developed GDL with MPL was evaluated.