A team of scientists at the U.S.
Department of Energy's (DOE) Brookhaven National Laboratory, in collaboration
with researchers from the University of Delaware and Yeshiva University, has
developed a new catalyst that could make ethanol-powered fuel cells feasible.
The highly efficient catalyst performs two crucial, and previously unreachable
steps needed to oxidize ethanol and produce clean energy in fuel cell reactions.
Their results are published online in the January 25, 2009 edition of Nature
Materials.
 | | Model of a ternary electrocatalyst for ethanol oxidation consisting of platinum-rhodium clusters on a surface of tin dioxide. This catalyst can split the carbon-carbon bond and oxidize ethanol to carbon dioxide within fuel cells. |
Like batteries that never die, hydrogen fuel cells convert hydrogen and oxygen
into water and, as part of the process, produce electricity. However, efficient
production, storage, and transport of hydrogen for fuel cell use is not easily
achieved. As an alternative, researchers are studying the incorporation of hydrogen-rich
compounds, for example, the use of liquid ethanol in a system called a direct
ethanol fuel cell.
“Ethanol is one of the most ideal reactants for fuel cells,” said
Brookhaven chemist Radoslav Adzic. “It’s easy to produce, renewable,
nontoxic, relatively easy to transport, and it has a high energy density. In
addition, with some alterations, we could reuse the infrastructure that’s
currently in place to store and distribute gasoline.”
A major hurdle to the commercial use of direct ethanol fuel cells is the molecule’s
slow, inefficient oxidation, which breaks the compound into hydrogen ions and
electrons that are needed to generate electricity. Specifically, scientists
have been unable to find a catalyst capable of breaking the bonds between ethanol’s
carbon atoms.
But at Brookhaven, scientists have found a winner. Made of platinum and rhodium
atoms on carbon-supported tin dioxide nanoparticles, the research team’s
electrocatalyst is capable of breaking carbon bonds at room temperature and
efficiently oxidizing ethanol into carbon dioxide as the main reaction product.
Other catalysts, by comparison, produce acetalhyde and acetic acid as the main
products, which make them unsuitable for power generation.
“The ability to split the carbon-carbon bond and generate CO2 at room
temperature is a completely new feature of catalysis,” Adzic said. “There
are no other catalysts that can achieve this at practical potentials.”
Structural and electronic properties of the electrocatalyst were determined
using powerful x-ray absorption techniques at Brookhaven’s National Synchrotron
Light Source, combined with data from transmission electron microscopy analyses
at Brookhaven's Center for Functional Nanomaterials. Based on these studies
and calculations, the researchers predict that the high activity of their ternary
catalyst results from the synergy between all three constituents – platinum,
rhodium, and tin dioxide – knowledge that could be applied to other alternative
energy applications.
“These findings can open new possibilities of research not only for electrocatlysts
and fuel cells but also for many other catalytic processes,” Adzic said.
Next, the researchers will test the new catalyst in a real fuel cell in order
to observe its unique characteristics first hand.
This work is supported by the Office of Basic Energy Sciences within DOE’s
Office of Science.
Posted January 25th, 2009
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