Sulfonated Polyhedral Oligosilsesquioxane (S-POSS) as a Nano-additive in Composite Multilayer Hydrogen Fuel Cell Proton Exchange Membranes
C. Hartmann-Thompson, P.I. Carver, D.L. Keeley, S.E. Keinath, B. Decker, P.R. Santurri
Michigan Molecular Institute, US
Keywords: polymers, POSS, fuel cell, proton exchange membranes
Abstract:The proton exchange membrane is a key component in the fuel cell system, and must exhibit a combination of good chemical resistance, temperature resistance, mechanical strength, and proton conductivity. Perfluorosulfonic acid ionomers such as Nafion® by DuPont are highly conductive and chemically stable, but they are costly to produce, lack mechanical strength and dimensional stability, have poor methanol crossover properties in direct methanol fuel cell applications, and perform poorly above 80°C, i.e., at the temperatures necessary to maximize catalyst efficiency and to minimize the size of the automotive cooling system. In earlier work1, a sulfonated polyhedral oligosilsesquioxane (S-POSS) nano-additive was formulated into sulfonated polysulfone (S-PPSU) to give a single-layer composite membrane that exhibited comparable proton conductivity but superior dimensional stability, temperature resistance and mechanical strength when compared with Nafion. In this study, S-POSS and S-PPSU (Figure 1) were used to fabricate multilayered composite proton exchange membranes with reduced brittleness and good proton conductivity at low relative humidity (Figure 2).