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Feature: The Fuel Cell Cometh
Hydrogen often wears the black hat when we talk about the prospect of everyday fuel cell use. It is difficult to transport and store. Alternative means of getting it generate their own problems. And the hydrogen they produce is less than pure and thus less efficient.
But oxygen, which is the other necessary reactant in many of today's fuel cell designs, is something of a villain in its own right. Splitting oxygen molecules into oxygen atoms and the subsequent formation of water is currently the rate-limiting step, the reaction that restricts overall power production, in the process of getting energy from fuel cells. Until this part of the process becomes more efficient, low-temperature fuel cells will not be commercially viable.
Manos Mavrikakis, his collaborators at the University of Wisconsin, and a group of experimental chemists at Brookhaven National Laboratory (led by Radoslav Adzic) are exploring the oxygen reduction reaction and the catalyst that provokes it. Namely, they're looking to make the reaction more efficient and to reduce the cost of expensive all-platinum catalysts. They use TeraGrid resources at the National Center for Supercomputing Applications and previously used TeraGrid resources at San Diego Supercomputing Center.
In 2005, articles by the team in the Journal of the American Chemical Society and Angewandte Chemie, International Edition showed the value of what are called platinum-mono-layer catalysts. The bulk of these catalysts are a cheaper material with a layer of platinum that is a single atom thick covering them. The team compared a variety of catalysts. Ultimately they found that palladium with the platinum monolayer, which is markedly cheaper, offered the best overall performance characteristics. It improved the overall efficiency of the oxygen reduction reaction by 33 percent.
With knowledge from the Mavrikakis team on the basic chemistry of the catalytic reaction, the folks at Brookhaven are further refining the candidate catalysts, looking for ways to reduce not only that platinum load but also the load of the other exotic elements like palladium.
"Everything is proven in reality," says Mavrikakis. "We've proven that [platinum monolayers can make the necessary oxygen dissociation and hydroxyl reactions] go faster and cheaper. The question that remains is how long do they go faster and cheaper. Is it only for the first second? Or will it last for the typical lifetime of your car? It's mind boggling to be able to do this from first principles on TeraGrid resources."
- Bill Bell, National Center for Supercomputing Applications
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