A futuristic economy based on hydrogen, an energy source capable of generating energy without pollution, just got one small step closer. Researchers report in the 27 June issue of Science that they've created a new nickel-based catalyst that converts agricultural waste to hydrogen gas. Although the new catalyst can't produce hydrogen as cheaply as can fossil fuels, it's still cheaper than previous catalysts, which required the precious metal platinum.
Dreams of a full-scale hydrogen economy have been rising for years. Fuel cells convert the gas to electricity efficiently with water as the only byproduct. But to make the hydrogen economy feasible, researchers need to find a dirt-cheap way to liberate hydrogen: It's bonded to oxygen atoms in water and carbon atoms in fossil fuels and plant matter, or biomass. Energy companies have long produced fairly cheap hydrogen gas by stripping hydrogen atoms from natural gas. Unfortunately, that generates large quantities of CO2, the heat-trapping gas that's the chief culprit in global warming.
In hopes of kicking the pollution habit, researchers have been focusing on catalysts that can strip hydrogen atoms from biomass. Even though that still generates CO2, the gas gets taken up by other plants as they grow. These plants can then be used to make more hydrogen gas, continuing the cycle. Platinum-based catalysts have long been the best performers in this department, but the precious metal costs a whopping $8000 a pound. Nickel catalysts have also been shown to be highly active. But unfortunately these generate abundant unwanted byproducts such as methane, another greenhouse gas.
To search for better catalysts, a team led by James Dumesic, a chemist at the University of Wisconsin, Madison, created a reactor capable of evaluating 48 separate metal-alloy catalysts simultaneously. The researchers then produced and tested more than 300 catalyst alloys. When they looked at the results, they discovered that a catalyst made from Raney-nickel--an alloy of 90% nickel and 10% aluminum--and a little bit of tin thrown in did the best job. When placed in a chamber with hot water and up to 5% biomass, it produced hydrogen with nearly the efficiency of platinum catalysts while sharply reducing the amount of methane compared to other nickel catalysts.
So far, the Wisconsin researchers have only tested their catalyst on simple sugars from plant cellulose rather than more complex compounds and mixtures also found in biomass. Nevertheless, "it's an important step," says Robert Ferrato, a catalyst expert at Engelhard Corp. in Iselin, New Jersey.
Dumesic Group's Web site