(August 24, 2005) — Heat has always been a problem
for fuel cells. There's usually either too much (ceramic
fuel cells) for certain portable uses, such as automobiles
or electronics, or too little (polymer fuel cells)
to be efficient.
While polymer electrolyte membrane (PEM) fuel cells are widely considered
the most promising fuel cells for portable use, their low operating temperature
and consequent low efficiency have blocked their jump from promising technology
to practical technology.
But researchers at the Georgia Institute of Technology have pinpointed a chemical
that could allow PEM fuel cells to operate at a much higher temperature without
moisture, potentially meaning that polymer fuel cells could be made much more
cheaply than ever before and finally run at temperatures high enough to make
them practical for use in cars and small electronics.
A team lead by Dr. Meilin Liu, a professor in the School of Materials Science
and Engineering at Georgia Tech, has discovered that a chemical called triazole
is significantly more effective than similar chemicals researchers have explored
to increase conductivity and reduce moisture dependence in polymer membranes.
The findings were published in the Journal of the American Chemical Society.
“Triazole will greatly reduce many of the problems that have prevented polymer
fuel cells from making their way into things like cars, cell phones and laptops,” said
Liu. “It's going to have a dramatic effect.”
A fuel cell essentially produces electricity by converting the chemicals hydrogen
and oxygen into water. To do this, the fuel cell needs a proton exchange membrane,
a specially treated material that looks a lot like plastic wrap, to conduct
protons (positively charged ions) but block electrons. This membrane is the
key to building a better fuel cell.
Current PEMs used in fuel cells have several problems that prevent them from
wide use. First, their operating temperature is so low that even trace amounts
of carbon monoxide in hydrogen fuel will poison the fuel cell's platinum catalyst.
To avoid this contamination, the hydrogen fuel must go through a very expensive
purification process that makes fuel cells a pricey alternative to conventional
batteries or gasoline-fueled engines. At higher temperatures, like those allowed
by a membrane containing triazole, the fuel cell can tolerate much higher levels
of carbon monoxide in the hydrogen fuel.
The use of triazole also solves one of the most persistent problems of fuel
cells — heat. Ceramic fuel cells currently on the market run at a very high
temperature (about 800 degrees Celsius) and are too hot for most portable
applications such as small electronics.
While existing PEM fuel cells can operate at much lower temperatures, they
are much less efficient than ceramic fuel cells. Polymer fuel cell membranes
must be kept relatively cool so that membranes can retain the moisture they
need to conduct protons. To do this, polymer fuel cells were previously forced
to operate at temperatures below 100 degrees Celsius.
Heat must be removed from the fuel cells to keep them cool, and a water balance
has to be maintained to ensure the required hydration of the PEMs. This increases
the complexity of the fuel cell system and significantly reduces its overall
efficiency. But by using triazole-containing PEMs, Liu's team has been able
to increase their PEM fuel cell operating temperatures to above 120
degrees Celsius, eliminating the need for a water management system and dramatically
simplifying the cooling system.
“We're using the triazole to replace water,” Liu said. “By doing so, we can
bring up the temperature significantly.”
Triazole is also a very stable chemical and fosters stable fuel cell operating
While they have pushed their polymer fuel cells to 120 degrees Celsius
with triazole, Liu's team is looking into better polymers to get those temperatures
even higher, he said.
For more information contact:
Megan McRainey, Institute Communications & Public Affairs
Contact Megan McRainey email@example.com
Georgia Institute of Technology is one of the nation's premiere research
universities. Ranked among U.S. News & World Report 's top
10 public universities, Georgia Tech educates more
than 16,000 students every year through its Colleges
of Architecture, Computing, Engineering, Liberal
Arts, Management and Sciences. Tech maintains a
diverse campus and is among the nation's top producers
of women and African-American engineers. The Institute
offers research opportunities to both undergraduate
and graduate students and is home to more than
100 interdisciplinary units plus the Georgia Tech
Research Institute. During the 2003-2004 academic
year, Georgia Tech reached $341.9 million in new
research award funding.