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You might not know much about them, but catalysts are all around us, making things happen in the gadgetry of modern life. They trigger the chemical reactions that heat up the wands in cordless hair curlers, detect the presence of a deadly odorless gas in carbon monoxide alarms, and "crack" crude oil into usable fuels.
Usually made from precious metals, catalysts are materials that speed chemical reactions without themselves being consumed in the process. For decades scientists have tried figure out exactly how catalysts work in the hopes of building cheaper, more efficient ones.
A team of University of Utah researchers this week announced a breakthrough after demonstrating links between the size of a catalytic material's particles, its electronic properties, and its ability to influence a reaction.
They published their findings Thursday in the journal Science .
"One of the big uncertainties in catalysis is that no one really understands what size particles of the catalyst actually make a chemical reaction happen," said senior author Scott Anderson, a U. professor of chemistry. Unlocking this mystery could help fix inefficiencies in energy-generation and other industrial systems.
"The development of inexpensive catalysts...is pivotal to energy capture, conversion and storage," said Henry White, chairman of the U. chemistry department, in a news release about the discovery. "This research is vital to the energy security of
Catalysts are costly because they are built with noble metals from the middle of the periodic table, like palladium, gold and platinum, said lead author, doctoral student Bill Kaden. Co-authors included students Tianpin Wu and William Kunkel.
In recent years, scientists have learned that much of the material in catalysts does little to spur reactions.
"In most, 90 percent or more is dead weight," Anderson said. That could mean tons of palladium, currently trading at $325 an ounce, is sitting idle in our catalytic converters -- the devices in automobiles that clean carbon monoxide and nitrogen dioxide from tailpipe emissions.
The U. team learned that the most catalytically active particles may be infinitesimally small -- 10 atoms for gold, for example. If scientists can figure out how to build catalysts from just the right sized particles, they would cost much less to make and work much better. The U. research could also lead to new catalysts built from more-common base metals, like zinc and nickel, but more research is needed.
"The way you are going to do that is by 'tuning' their chemical properties, which means tuning the electronic properties because the electrons control the chemistry," Anderson said.
To conduct the experiments, the U. team used new technologies that allowed them to isolate tiny metal particles of particular sizes. They vaporized a piece of palladium with a laser, then guided the electrically charged nano-scale particles through a helium flow.
Using a mass spectrometer, they separated out particles with a certain number of atoms. The researchers affixed these particles to a ceramic surface in an effort to mimic catalytic devices in industry and observed their influence on catalytic processes and changes in the behavior of their electrons.
Just the addition or subtraction of one or two atoms made a difference in the catalytic and electronic properties, Kaden said.
"That paper is the tip of the iceberg. We can say, 'Wow, look at this, it's pretty cool.' Now we want to get more detail of what's happening on the catalysts," Kaden said. "One drawback is, as catalyst react they change due to heat. Particles tend to agglomerate with heat. The idea is to figure out how to keep appropriately sized particles on the surface."
