[Homestead] Fuel Cells

Tvoivozhd tvoivozd at infionline.net
Mon Sep 13 20:17:13 EDT 2004


Ever since I went to the University of Wisconsin, their Chemistry 
Department has been amont the world's best---the tradition continues 
with the use of carbon monoxide in producing electricity---shoots the 
total fuel cell efficiency up to 40% in a cool-running fuel cell.


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/Source:/ 	*University Of Wisconsin-Madison* 	
/Date:/ 	2004-09-13
/URL:/ 	http://www.sciencedaily.com/releases/2004/09/040913085654.htm

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    Discovery Could Lead To New Strategies For Operating Fuel Cells

MADISON - Carbon monoxide, or CO, has long been a major technical 
barrier to the efficient operation of fuel cells. But now, chemical and 
biological engineers at the University of Wisconsin-Madison have not 
only cleared that barrier - they also have discovered a method to 
capture carbon monoxide's energy.

To be useful in a power-generating fuel cell, hydrocarbons such as 
gasoline, natural gas or ethanol must be reformed into a hydrogen-rich 
gas. A large, costly and critical step to this process requires 
generating steam and reacting it with carbon monoxide (CO). This 
process, called water-gas shift, produces hydrogen and carbon dioxide 
(CO2). Additional steps then are taken to reduce the CO levels further 
before the hydrogen enters a fuel cell.

James Dumesic, professor of chemical and biological engineering , 
postdoctoral researcher Won Bae Kim, and graduate students Tobias Voitl 
and Gabriel Rodriguez-Rivera eliminated the water-gas shift reaction 
from the process, removing the need to transport and vaporize liquid 
water in the production of energy for portable applications.

The team, as reported in the Aug. 27 issue of Science, uses an 
environmentally benign polyoxometalate (POM) compound to oxidize CO in 
liquid water at room temperature. The compound not only removes CO from 
gas streams for fuel cells, but also converts the energy content of CO 
into a liquid that subsequently can be used to power a fuel cell.

"CO has essentially as much energy as hydrogen," Dumesic says. "It has a 
lot of energy in it. If you take a hydrocarbon and partially oxidize it 
at high temperature, it primarily makes CO and hydrogen. Conventional 
systems follow that with a series of these 'water-gas shift' steps. Our 
discovery has the potential of eliminating those steps. Instead, you can 
send the CO through our process, which works efficiently at room 
temperature, and takes the CO out of the gas to make energy."

The research team says the process is especially promising for producing 
electrical energy from renewable biomass-derived oxygenated hydrocarbons 
- such as ethylene glycol derived from corn - because these fuels 
generate H2 and CO in nearly equal amounts during catalytic 
decomposition. The hydrogen could be used directly in a 
proton-exchange-membrane fuel cell operating at 50 percent efficiency, 
and the remaining CO could be converted to electricity via the 
researchers' new process.

The overall efficiency of such a system is equal to 40 percent and, 
unlike traditional ethylene glycol reforming, does not require water. 
The overall efficiency is equivalent to 60 percent of the energy content 
of octane.

Dumesic's team believes the advance will make possible a new generation 
of inexpensive fuel cells operating with solutions of reduced POM 
compounds. While higher current densities can be achieved in fuel cells 
using electrodes containing precious metals, the researchers found that 
good current densities can be generated using a simple carbon anode.

*Editor's Note:* The original news release can be found here 
<http://www.news.wisc.edu/releases/10072.html>.

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/This story has been adapted from a news release issued by University Of 
Wisconsin-Madison./







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