Oct
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Watching Catalysts Work
October 30, 2008 | 7 Comments
Lawrence Berkeley National Laboratory scientists have managed to observe catalysts restructuring themselves as gases are moved through. Using a state-of-the-art spectroscopy system the team watched, for the first time, as nanoparticles composed of two catalytic metals changed their composition in the presence of different reactants. Until now, scientists have had to rely on snapshots of catalysts taken before and after a reaction, never during.
Berkeley Catalyst Image
The ability to view in real time could give scientists the ability to develop cheaper and smarter catalysts that are fine-tuned to drive the chemistry of everyday life, such as reactions that sweep toxins from pollutants, drive fuel refinement techniques and material processing and production. It could mean the development of catalysts that mop up all the substances in a reaction except the desired product, the hallmark of “green chemistry” in which waste byproducts are minimized.
“By watching catalysts change in real time, we can possibly design smart catalysts that optimally change as a reaction evolves,” said Gabor Somorjai, a surface science and catalysis expert who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s department of chemistry. The research was conducted with Miquel Salmeron, a pioneer in a field of spectroscopy that enabled this work. Salmeron also holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s department of materials sciences and engineering.
Catalysts, most famously exemplified by catalytic converters, which reduce toxic emissions from vehicle tailpipes, are substances that speed up chemical reactions. Used from oil refining on to pharmaceutical manufacturing they are as ubiquitous as they are valuable. They’re essential to the production of many important industrial chemicals.
Until now, however, nanoscale catalysts could only be observed before and after a reaction. The crucial segment — how a catalyst morphs during a reaction — remained the stuff of guesswork. That’s a huge obstacle. As Somorjai explains, “It’s like trying to understand someone’s life by observing the person as a newborn baby, then fast-forwarding to old age. What transpires in between is incredibly important, but also incredibly difficult to decipher by observing two widely disparate stages.”
Salmeron adds, “It’s difficult to tune a catalyst to do exactly what you want unless you know how it adapts during a reaction. With our work, we can for the first time see what the catalyst is doing during the reaction, not before and after.”
This new ability to view the activity required the combined expertise of both Somorjai and Salmeron. First, they had to work at the nanoscale, which is the scale at which most catalysts operate (one nanometer is one-billionth of a meter). Using techniques developed in his lab, Somorjai synthesized nanoscale particles composed of common catalytic metals. Some particles were made of rhodium and palladium, while others were made of platinum and palladium.
Then, to see how these bimetallic catalysts change in the presence of reactants, they turned to one of the few spectroscopy instruments in the world that enables scientists to study catalytic and biological phenomena in their natural environment, that is, at almost normal pressures and in the presence of different chemicals.
The latest spectroscopy instrument is the first of its kind, developed by Salmeron and colleagues and is located at Berkeley Lab’s Advanced Light Source. Like all spectroscopy systems, it identifies elements by detecting their unique spectral signals. But unlike most, the ambient pressure photoelectron spectroscopy system works under similar pressures and environments faced by everyday phenomena, instead of requiring a carefully controlled vacuum.
Next they watched, in real time, as the bimetallic nanoparticles restructured themselves when exposed to different gases, such as nitrogen oxide, carbon monoxide, and hydrogen. In the presence of some reactants, rhodium rose to a particle’s surface. While in the presence of other reactants, palladium rose to the surface.
“From one gas to another, we observed different metals segregating to a catalyst’s surface, which is the part of the catalyst that drives chemical reactions,” says Somorjai. “And this makes all the difference in establishing how the catalyst participates in the chemistry.”
This information enables scientists to develop nanoparticle catalysts and reactants that are tailored to most efficiently yield a product, whether it’s gasoline or cleaner emissions. With the power to see what’s happening researchers can engineer bimetallic nanoparticle catalysts in which one metal rises to the surface during an initial stage of a reaction, and a different metal rises to the surface in a latter stage. The goal is to ensure that the most active metal is on the catalyst’s surface precisely when it’s needed most. In this way, the final product can be developed as quickly and cheaply as possible.
The next step for Somorjai and Salmeron is the hope to observe how catalysts change shape during a reaction, which could be as equally important as compositional change in driving chemical reactions.
Many readers will recognize that this is a very big deal indeed. Catalytic reactions have become a huge part of chemical engineering and production. Catalysts are now a growth segment in biology and humanity’s rush to synthetically recreate nature’s activities. The team at Berkeley has a significant breakthrough here.
As we learned last week about using supercomputers to pre examine custom made molecules the prospects for much faster development of catalysts has just improved dramatically. This is basic research that drives better, faster and cheaper research and enables sifting through ideas much cheaper and faster. Over time the database will get built that will provide innovators a foundation for intuition and surely some spectacular breakthroughs.
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[…] It could mean the development of catalysts that mop up all the substances in a reaction except the desired product, the hallmark of “green chemistry” in which waste byproducts are minimized. … Watching Catalysts Work […]
[…] Watching Catalysts Work First, they had to work at the nanoscale, which is the scale at which most catalysts operate (one nanometer is one-billionth of a meter). Using techniques developed in his lab, Somorjai synthesized nanoscale particles composed of common … […]
It’s a good start on what will surely be a growing field in catalyst research and development. The very idea that catalyst operations can be observed and improved implies that catalyst improvements could be coming much faster and with better results at an ever-increasing rate.
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