Molecular Dynamics Study of the Structure and Permeability of Polymer Electrolyte Membranes for Fuel Cells

• Published in: KOBUNSHI RONBUNSHU Vol. 73; no. 6; pp. 520 - 531
• Main Authors: KAWAKAMI, Tomonori, SIMOYAMA, Naoki, SAKIYAMA, Yoko, SHIGEMOTO, Isamu
• Format: Journal Article
• Language: Japanese; English
• Published: The Society of Polymer Science, Japan 01.01.2016
• Subjects: Crossovers; Electrolytes; Fuel Cell; Membranes; Methanol Crossover; Methyl alcohol; Moisture content; Molecular Dynamics; Molecular structure; Polymer Electrolyte Membrane; Proton Conductivity; Simulation
• ISSN: 0386-2186; 1881-5685
• DOI: 10.1295/koron.2016-0032

Polymer electrolyte membranes (PEMs) with high proton conductivity and low fuel (hydrogen or methanol) crossover are essential for developing efficient polymer electrolyte fuel cells (PEFCs). To obtain an optimal design for PEMs with high proton conductivity and low methanol crossover (MCO), we carried out a series of molecular dynamics (MD) simulations on sulfonated poly(phenylene oxide) (SPPO) and Nafion® membranes with variations in water content and degree of sulfonation. We investigated the structures of these polymers and the diffusion mechanisms of protons, water, and methanol. Our simulation results indicated that it is possible to achieve both high proton conductivity and low MCO if the water content in highly sulfonated SPPO can be reduced. We examined composite membranes consisting of SPPO and cross-linked resins such as epoxy and silane in an attempt to control the water content. As a result, we succeeded in reducing water content and MCO in highly sulfonated SPPO, while keeping proton conductivity equivalent to that of Nafion®.