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Harvesting Hydrogen Fuel from Plants Gets Cheaper



A major roadblock to widespread use of hydrogen-powered electric vehicles, which emit water vapor as a by-product and could cut greenhouse gas emissions substantially, is the cost and trouble associated with producing a suitable supply of hydrogen. Last year scientists reported having developed a technique to harness the fuel from biomass, but the catalyst required for the reaction was too expensive to be commercially viable. The same researchers announce today in the journal Science that they have discovered a different catalyst that works just as well--at a fraction of the cost.

James Dumesic and his colleagues at the University of Wisconsin-Madison, tested more than 300 materials in search of one that could catalyze the reaction of hydrocarbons derived from biomass to form hydrogen--a process known as aqueous-phase reforming (APR)--as well as a platinum-based catalyst does. "The APR process can be used on the small scale to produce fuel for portable devices such as cars, batteries and military equipment," Dumesic says. "But it could also be scaled up as a hydrogen source for industrial applications, such as the production of fertilizers or the removal of sulfur from petroleum products." The researchers found that a catalyst known as Raney-nickel, which is 90 percent nickel and 10 percent aluminum--was moderately effective at producing hydrogen. Adding tin to the mix yielded a catalyst that was comparable to the platinum-based one and performed admirably at lower temperatures.

The scientists also refined the system to manufacture hydrogen having containing less carbon monoxide (CO), which can contaminate the electrodes in hydrogen fuel cells. Whereas previous setups produced hydrogen with about 300 parts per million of CO, Dumesic and colleagues have lowered the CO content to about 60 parts per million.

"Vehicle of Change," by Lawrence D. Burns, J. Byron McCormick and Christopher E. Borroni-Bird (Scientific American, October 2002), is available for purchase from Scientific American Digital.
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