(277g) Electrochemical Performances of Non-Perfluorinated Membrane-Electrode Assemblies for Dmfc Application

Membrane-electrode assembly (MEA) for fuel cell is composed of proton exchange membrane (PEM) and catalyst layers. The catalyst layers are coated on the membrane or the gas diffusion layer using various methods such as spray coating, screen printing, and rolling. Most of MEA fabrication methods are appropriate to perfluorinated polymer-based MEA. Up to now, Nafion® ionomer with equivalent weight of 1,100 has been used as a catalyst binder. When Nafion® membrane is used as PEM, compatibility between the Nafion® membrane and the catalyst layer containing Nafion® ionomer guarantees high electrochemical properties even in the long term operation. However, in case of MEA containing non-perfluorinated polymer membrane, incompatibility with Nafion®-based catalyst layer leads to difference in adsorption and desorption of PEM and binder materials in water-methanol mixture, delamination of catalyst layers, high contact resistance in the interface of membrane and catalyst layers, and rapid reduction of electrochemical performances of the MEA. In this present study, crosslinked-sulfonated polyimide (XSPI)-inorganic oxide nanocomposite membranes were fabricated via two consecutive processes for fabricating of sulfonated polymer matrix in combination with crosslinking, and direct mixing of inorganic oxide particles to improve radical stability of membranes. The well-known commercial surfactants, Pluronics® were used as both crosslinkers to control water uptake level, and dispersants to homogeneously distribute inorganic particles in the XSPI. The XSPI-inorganic oxide nanocomposite membranes with excellent proton conductivity and hydrolytic stability (~336 days) were used for fabrication of MEAs, which were evaluated under different fuel cell conditions. The single cell performances using the nanocomposite membranes were superior or similar to those of Nafion 117.