NAMS 2002 Workshop - ICOM 2008

Fuel Cells II – 1 – Keynote
Thursday July 17, 8:15 AM-9:00 AM, Wai’anae
Fuel Cell Membranes from Nanofiber Composites
R. Wycisk (Speaker), Case Western Reserve University, Cleveland, Ohio, USA -
ryszard.wycisk@case.edu
J. Choi, Case Western Reserve University, Cleveland, Ohio, USA
K. Lee, Case Western Reserve University, Cleveland, Ohio, USA
P. Pintauro, Case Western Reserve University, Cleveland, Ohio, USA
P. Mather, Syracuse University, Syracuse, New York, USA
New generation of proton conducting membranes meeting the needs of the
emerging fuel cell industry will have to appear soon if fuel cells are to play an
important role in the transformation towards greener energy production. Those
membranes will combine the latest developments in both materials chemistry and
nanomorphology control.
The most obvious trend in sulfonic acid type membrane polymers is to increase
the sulfonation degree so as to maximize proton conductivity and water retention
capability, which are especially important for applications in hydrogen fuel cells.
Unfortunately, this approach leads to problems with membrane
dimensional/mechanical stability. Recent studies on the advantageous
nanomorphologies of multiblock sulfonic copolymers open up an interesting
avenue for improvements. Still this approach has limits imposed by the
monomer/oligomer reactivity, block stoichiometry and casting solvent availability.
An entirely new approach for fabricating fuel cell membranes has been
developed by the present authors. It can be universally applied to a wide range of
proton conducting materials. Briefly, a three-dimensional, interconnected network
of proton-conducting polymer nanofibers fabricated via electrospinning is
embedded in an inert/impermeable polymer matrix. The nanofiber network,
occupying about 40-70% of the dry membrane volume, is composed of a high
ion-exchange capacity sulfonic acid polymer to ensure high water affinity and a
high concentration of protogenic sites. The inert (hydrophobic) polymer matrix
controls water swelling of the nanofibers and provides overall mechanical
strength to the membrane. Unlike other fuel cell membranes, the role of the
mechanical support is decoupled from that of the proton conductor. This
composite structure is also free from the limitations imposed by the percolation
effects typical of classic phase-separated systems.
The talk will be on the experimental details of nanofiber composite membranes
fabrication. Water swelling, proton conductivity, and thermal/mechanical
properties of the resulting membranes will be discussed.