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Design of an effective methanol-blocking membrane with purple membrane for direct methanol fuel cells

Xiang, Yan, Zhang, Jin, Liu, Yang, Guo, Zhibin, Lu, Shanfu
Journal of membrane science 2011 v.367 no.1-2 pp. 325-331
artificial membranes, composite materials, electricity, fuel cells, membrane proteins, methanol, permeability, surfaces
In this study, purple membrane (PM) was applied as a methanol-blocking agent on Nafion® membranes. A series of well-organized poly(diallyldimethylammonium chloride)/PM multilayer films were obtained on a Nafion® 212 surface (PDDA/PM/Nafion®) to form composite membranes by the electrostatic layer-by-layer (LbL) self-assembly method. The effect of the PDDA/PM/Nafion® heterogenic interface on proton conductivity and methanol permeability was studied by alternating the deposited surface. With five PDDA/PM bilayers, double-sided modification (PDDA/PM)DF₋₅ and single-side modification (PDDA/PM)SF₋₅ resulted in excellent methanol blocking with a 73.4% and 64.7% reduction in methanol permeability in comparison with unmodified Nafion® 212, respectively. Indeed, the involvement of PM suppressed the methanol crossover. With regard to the selectivity factor (PDDA/PM)DF₋₁ composite membranes showed approximately 2-fold improvement as compared with unmodified Nafion® membranes. The cell performance of (PDDA/PM)SF₋₁ composite membranes achieved a power density of 27.0mWcm⁻² which is 48.4% increase compared to cells using unmodified Nafion® 212 membranes. Moreover, with (PDDA/PM)DF₋₁, we achieved a power density of 34.4mWcm⁻². This study highlights the potential application of PM as multifunctional protein membrane in direct methanol fuel cells.