Breaking carbon’s tough bonds for fuel


Jan.  27, 2009

A team of scientists at the U.S. Department of Energy's  (DOE) Brookhaven 
National Laboratory, in collaboration with researchers from the  Univ. of 
Delaware and Yeshiva Univ., 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 
Jan. 25 edition of Nature Materials.

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.

The abstract to this  study is available here, 
_http://www.nano-biology.net/showabstract.php?metaid=165122_ 
(http://www.nano-biology.net/showabstract.php?metaid=165122) 

Brookhaven's  Center for Functional Nanomaterials, _http://www.bnl.gov/cfn/_ 
(http://www.bnl.gov/cfn/) 

SOURCE:  Brookhaven National Lab
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