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Brian Benicewicz, professor of chemistry
and director of the NY State Center for Polymer Synthesis
since 1997, is involved in a major research effort to develop
high-temperature fuel cell membranes. A fuel cell is a device
that combines hydrogen and oxygen to produce electric power.
It does so without combustion by taking hydrogen, derived
from a source such as natural gas, and drawing in oxygen from
the air. When hydrogen gas is introduced into the system,
the catalyst surface of a polymer membrane splits hydrogen
gas molecules into electrons and protons. The electrons, which
cannot pass through the membrane, must travel around it, thus
creating the source of a direct electrical current. The protons
pass through the membrane to react with the returning electrons
and oxygen from the air, forming water and heat as byproducts.
Polymer membranes play a central
and critical role in PEM (proton exchange membrane) fuel cells.
Limitations in polymers now used prevent the development of
a more efficient fuel cell that can be marketed on a large
scale. For example, the polymer membranes now used in PEM
fuel cells must remain constantly hydrated. The requirement
to maintain a constant amount of water in these membranes
causes instability and limits the reliability necessary for
a commercial fuel cell. Building complex water control systems
to fix the problem are too cumbersome and costly, says Benicewicz.
To avoid traditional complications of current fuel cells,
Benicewicz turned his research to polybenzimidazole (PBI).
Used for many years in high-performance protective apparel
such as fireman’s coats and astronaut space suits, PBI
has characteristics important to building a successful and
inexpensive fuel cell. It has no melting point, will not ignite,
and most importantly, PBI does not require water for conductivity.
Research by Benicewicz and his team is focused on the synthesis
and development of PBI as a high temperature fuel cell membrane.
Many polymers have been prepared and fabricated into membranes.
Proton conductivity measurements have shown that PBI membranes
have conductivities that equal or better the values of materials
currently used. Similar tests at 160°C have demonstrated
that the high conductivities are retained in PBI membranes.
At these high temperatures, membranes that rely on water for
proton conductivity would lose all their water and become
nonconductive. Many advanced concepts to further improve PBI
membranes for fuel cell applications are being pursued.
Brian Benicewicz
Director, NYS Center for Polymer Synthesis
Professor, Department of Chemistry
Rensselaer Polytechnic Institute
110 8th Street
Troy, NY 12180-3590
(518)276-2534
benice@rpi.edu
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