focus on research
Designing Better Fuel Cells,
One Nanocarbon at a Time
An electrochemist finds new uses for carbon in an effort to boost the
performance and efficiency of fuel cells
“There won’t be a revolutionary advance in
uel cells are poised to revolutionize en- Stevenson is part of a core group of scientists at The
fuel cell technology until we understand the
ergy production around the world. The University of Texas looking to increase the efficiency of
technology could be at the epicenter of fuel cells by improving the way the fuel, hydrogen and
basic mechanisms of these chemical processes
a new “hydrogen economy,” an economy where oxygen, is converted to electricity (see graphic).
hydrogen, not oil or coal, ignites our engines and “If you really want to make fuel cells feasible at a and design better materials to make fuel
powers our homes. Fuel cells could supply us with safer, commercial level, you need to reduce oxygen to water
cell reactions more efficient.”
cleaner energy than the power plants and internal com- more efficiently,” says Stevenson. “This is one of the
bustion engines used today. hardest challenges.”
But there’s much work to be done before that revolu- Oxygen and hydrogen combine to become water
Dr. Keith Stevenson.
tion, says Dr. Keith Stevenson, assistant professor in the with the help of a catalyst, such as platinum, that is
Photo by: Matt Lankes.
Department of Chemistry and Biochemistry. He says affixed to carbon electrodes. Both the catalyst and its 20 nm
that although fuels cells are two to three times more carbon supports need improvement in order to in-
efficient than internal combustion engines, significant crease fuel cell efficiency, Stevenson says. His research Nitrogen-doped carbon nanofibers like the one above (dotted with catalyst) help
promote oxygen reduction and could be used to increase the efficiency of fuel
improvements must be made before the technology focuses on carbon electrodes—making them better
cells. Transmission electron microscopy (TEM) image by: Ganesh Vijayaraghavan.
gains widespread use. supports for catalysts and improving their ability to
how a fuel cell works
conduct electricity.
Stevenson and his collaborators have recently con- A fuel cell produces electricity via chemical reactions, rather than by the physical combustion of hydrocarbons, like gasoline. Hydrogen and oxygen are the
fuels that power fuel cells, and the only waste product is water. When operating at full capacity, a fuel cell has the potential to produce 1.2 volts of electricity,
structed nano-sized hollow tubes made of carbon. The
about the same as a AAA battery. Stacks of fuel cells are combined together to create more power.
bamboo-like nanocarbons can be custom assembled
into complex 3D shapes, and they show significant

1 2 3
promise as carbon electrodes for fuel cells. Stevenson Diagram of a Fuel Cell • Hydrogen (H
2
) enters anode • Electrons flow from anode • With the help of a catalyst,
(Proton Exchange Membrane) • H
is now working on fine-tuning the new nanocarbon’s
2
broken down by a to cathode, generating oxygen (O
2
), electrons, and protons
200 mm 40 mm catalyst into protons (H
+
) electrical current combine to form water
chemical and catalyst support properties. and electrons (e
-
) • H
+
flows from anode
to cathode
To this end, Stevenson has discovered that he can
make the carbon electrodes better by infusing them
with other elements, like nitrogen. The nitrogen-doped
nanocarbon electrodes make more active catalysts like
platinum catalyze more oxygen reactions. These nano-
carbons can also be tuned to catalyze the oxygen reduc- anode cathode
(+) (-)
4 mm 2 mm tion reactions themselves.
It’s big findings at this small scale that will impact
This series of images shows a nickel mesh electrode covered the commercialization of fuel cells. “There won’t be a
with carpet-like carbon nanofibers. Individual nanofibers Carbon Carbon
revolutionary advance in fuel cell technology,” Steven-
are visible in the bottom right image. Scanning electron w/ platinum w/ platinum
microscopy (SEM) images by: Stephen Maldonado. son says, “until we understand the basic mechanisms & ruthenium catalyst
catalysts
of these chemical processes and design better materials
to make fuel cell reactions more efficient.” ✥ Proton Exchange Membrane
12 s p r i n g 2 0 0 6 f o c u s o n s c i e n c e 13
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