Out of plane expansion of PFSA membranes for fuel cell applications
Date
2010-05
Authors
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Publisher
University of Delaware
Abstract
A critical element of a hydrogen fuel cell is the proton‐exchange membrane. Its
unique properties allow it to conduct the protons of hydrogen atoms, while excluding the
electrons to create an electrical charge. A fuel cell’s overall durability and conductivity is in
large part determined by the properties of the membrane. This research involves the use of
perfluorosulfonic acid (PFSA) membranes, a common type of proton‐exchange membranes.
When any material is heated or cooled, it typically expands or contracts and, if
this dimensional change is constrained, it causes a stress in the material. This stress, when
applied cyclically over a period of time, leads to damage and eventual failure of the material.
Hence over time as the membrane of a fuel cell is subjected to changes in temperatures, the
membrane experiences a decrease in its durability and conductivity. Also, in order for these
membranes to properly function, a certain level of hydration is needed. PFSA membranes
are hydrophilic, and easily absorb water from the chemical reaction it sustains and from the
atmosphere. Thus the absorption of the water causes the membrane to swell and result in
dimensional changes in its thickness and in‐plane dimensions. Similarly to thermal
expansion, when this swelling strain is constrained, it causes a stress in the material, and
ultimately results in damage or failure when applied cyclically over time. Therefore the goal
of this research is to understand how PFSA membranes expand and contract over a range of
temperatures from ‐40° C to 105° C, as well as with varying humidities in the range of 30% to
100%.