New Membrane Nano-Morphologies for Improved Fuel Cell Operation
Author(s)
Pintauro, Peter
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Abstract
Polymeric membranes play a crucial role during the generation of electricity in hydrogen/air and direct
methanol proton-exchange membrane (PEM) fuel cells. The membrane in such devices has three
functions: (1) to physically separate the positive and negative electrodes (so there is no electrical short
circuit), (2) to prevent mixing of the fuel and oxidant, and (3) to provide a conduit for proton transport
between the electrodes. For hydrogen fuel cells, the membrane must exhibit low gas permeability and
high proton conductivity. For a direct liquid methanol PEM fuel cell, the ion-exchange membrane must
conduct protons and be a good methanol barrier. For any fuel cell, the membrane must have good
mechanical properties in the wet and dry states and be chemically stable under fuel cell operating
conditions. DuPont’s Nafion® (a perfluorosulfonic acid polymer) has many attractive properties and has
been widely studied in PEM fuel cells, but it does not meet all performance criteria. In a hydrogen/air
fuel cell, Nafion loses water and the conductivity drops at temperatures 80oC, unless the water activity
in the feed gases is near unity. Nafion has also been used in direct methanol fuel cells, but high methanol
crossover (permeation) leads to low power output due to cathode depolarization.
Polymer nano-morphology manipulation/control is a promising strategy to improve the performance of
fuel cell membranes. Two examples of this approach will be discussed: (i) pre-stretched recast Nafion for
direct methanol fuel cells and (ii) composite membranes based on proton conducting ionomeric nanofibers.
Membrane fabrication methods and the results of membrane characterization tests will be
described. Physical property data relevant to PEM fuel cell applications will be related to the membrane’s
nanostructure and fuel cell performance data will be presented.
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Date
2009-02-04
Extent
60:08 minutes
Resource Type
Moving Image
Resource Subtype
Lecture