Method to capture carbon monoxide's energy for new generation of inexpensive fuel cells

Aug 26, 2004

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 UW-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.

Source: University of Wisconsin-Madison

Explore further: Wireless sensor transmits tumor pressure

add to favorites email to friend print save as pdf

Related Stories

Specialized species critical for reefs

25 minutes ago

One of Australia's leading coral reef ecologists fears that reef biodiversity may not provide the level of insurance for ecosystem survival that we once thought.

Recommended for you

Wireless sensor transmits tumor pressure

2 hours ago

The interstitial pressure inside a tumor is often remarkably high compared to normal tissues and is thought to impede the delivery of chemotherapeutic agents as well as decrease the effectiveness of radiation ...

Tim Cook puts personal touch on iPhone 6 launch

3 hours ago

Apple chief Tim Cook personally kicked off sales of the iPhone 6, joining in "selfies" and shaking hands with customers Friday outside the company's store near his Silicon Valley home.

Team improves solar-cell efficiency

19 hours ago

New light has been shed on solar power generation using devices made with polymers, thanks to a collaboration between scientists in the University of Chicago's chemistry department, the Institute for Molecular ...

Calif. teachers fund to boost clean energy bets

19 hours ago

The California State Teachers' Retirement System says it plans to increase its investments in clean energy and technology to $3.7 billion, from $1.4 billion, over the next five years.

User comments : 0