Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Removing a hydrogen fuel-cell roadblock

28.03.2007
Ames Laboratory seeks palladium substitute that’s key to cost-effective fuel-cell operation

Researchers at the U.S. Department of Energy’s Ames Laboratory are employing some modern day alchemy in an effort to find a material with properties of rare and high-priced palladium. If they’re successful, it could remove a major roadblock from the path of hydrogen fuel-cell powered vehicles.

Hydrogen fuel-cell technology sounds almost too good to be true. You combine cheap and plentiful hydrogen and oxygen gas, the fuel cell generates electricity and the by-product is simply water. But it’s a little more involved.

The key is a proton exchange membrane, or PEM, containing platinum. The platinum acts as a catalyst that separates electrons from the hydrogen gas atoms. The free electrons are gathered as current and the positively charged hydrogen ions pass through the membrane where they readily combine with oxygen atoms to form water. But if the hydrogen gas contains impurities, such as water vapor or carbon monoxide, it can “gum up” the fuel cell’s separation membrane, dropping efficiency or halting the process altogether. Pure hydrogen, however, is hard to come by, and that’s where palladium enters the picture.

“Hydrogen is tough to handle because of the small size of the atoms and because it naturally wants to bond with other elements,” said Ames Laboratory scientist Alan Russell, one of the investigators on the project. “Palladium acts like an atomic filter – the hydrogen atoms readily diffuse right through the metal.”

In the conventional approach to purifying hydrogen, an alloy of 73 percent palladium and 27 percent silver is drawn into long thin tubes, about 3 mm in diameter and 20 feet long. Clusters of these tubes are placed inside a vacuum chamber and heated to between 400 and 500 Celsius. Impure hydrogen gas is then pumped into the small tubes, and the hydrogen readily diffuses through the palladium-silver tube walls and is captured in the outer chamber while the impurities travel out the other end of the tubes.

“Palladium is $11,000 a kilogram, and even if you didn’t choke at the price, there isn’t enough palladium in the entire world to convert the world’s automobiles to hydrogen power,” Russell said. “So the trick is to find a material with the same properties as palladium that is cheaper and much more readily available.”

His use of the word trick isn’t a stretch. Not only does the material have to be less expensive and readily available, it has to allow hydrogen to pass through it and be ductile enough to be drawn into long, thin tubes. It also has to resist oxidation, because oxygen and water vapor are commonly present in impure hydrogen. And finally, hydrogen has a nasty habit of making metals brittle, so the metal also has to handle repeated heating and cooling cycles, while loaded with hydrogen, without becoming brittle.

“With so many variables, we don’t really have any analytical tools that would let us mathematically predict the ideal composition,” Russell said, “so we have to use a Thomas Edison approach – relying on intuition and a fair amount of luck to come up with a combination that works.”

The three-year project is being spearheaded by Robert Buxbaum, president of REB Research, a Michigan firm involved in hydrogen filtration and fuel-cell technology. Buxbaum is particularly interested in a membrane reactor which combines hydrogen generation and filtration right at the fuel cell. Buxbaum obtained $2.8 million from DOE to find substitutes for platinum and palladium. Besides Russell and visiting Chinese scientist Jie Zhang, the project includes Larry Jones, director of Ames Laboratory’s Materials Preparation Center, as well as researchers at Los Alamos National Laboratory, the National Energy Technology Laboratory, and G&S Titanium, an Ohio-based materials fabrication firm.

Buxbaum proposed developing 100 different alloys, relying on the expertise of Russell and Jones in the field of metals development to pick the mixtures. “It is not by accident that I asked to work with Alan and Larry,” Buxbaum said. “They are fantastically talented at what they do,” adding that the program in Ames “is the best in the United States and among the best in the world.”

Using X-ray diffraction technology to study the crystal microstructure of the materials, Zhang can determine whether the materials show promise in terms of ductility. This provides a shortcut of sorts so that the team doesn’t waste time on materials that are potentially brittle. A little more than a year into the project, about 60 binary alloys have been developed with additional ones in the planning stages. The results have been mixed, but Russell indicated one sample is quite promising and several others show promise.

“There have been surprises. Some alloys that you would expect to be ductile turn out to be hopelessly brittle, like glass,” Russell said. “We also tried a material with 25 percent ruthenium, an element which is notorious for making alloys brittle, but that material turned out to be quite ductile.” Samples produced in Ames are first cold rolled to see if they are ductile. Those showing promise are further tested and shipped to REB Research where they’re tested to determine how easily hydrogen will diffuse through the metal. Those showing promise get further testing to see if they can be formed into tubes and how they respond to heating and cooling cycles. But even those materials that are rejected as a palladium substitute, may ultimately wind up as useful for other purposes.

“I think we’ve got a good chance of finding something that works for hydrogen generation, but even if none of these alloys are good at that, the materials we’re working with will certainly have other applications.” Buxbaum said. “One metal in particular is an amazing alloy – shiny, ductile, high melting, and totally resistant to aqua regia (a mixture of nitric and hydrochloric acids that dissolves gold or platinum).”

Russell added that the willingness of the DOE to fund such a program is indicative of the commitment to develop alternative energy sources.

“Research funding often depends on your ability to demonstrate specific results,” he said. “It’s refreshing in a way to get to try traditional metallurgy techniques to try to solve a 21st century problem.”

Ames Laboratory, celebrating its 60th anniversary in 2007, is operated for the Department of Energy by Iowa State University. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.

Kerry Gibson | EurekAlert!
Further information:
http://www.ameslab.gov

More articles from Power and Electrical Engineering:

nachricht Researchers pave the way for ionotronic nanodevices
23.02.2017 | Aalto University

nachricht Microhotplates for a smart gas sensor
22.02.2017 | Toyohashi University of Technology

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Organ-on-a-chip mimics heart's biomechanical properties

23.02.2017 | Health and Medicine

Light-driven reaction converts carbon dioxide into fuel

23.02.2017 | Life Sciences

Oil and gas wastewater spills alter microbes in West Virginia waters

23.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>