Control of chemical catalysts with sculpted light

Like a cat fighter, catalysts play the role of catalysts in chemical reaction speeding up the process – and getting out of it that way. And, just as not every house in the neighborhood has someone willing to take part in such a battle, not every part of the catalyst participates in the retaliation. But what if one could be persuaded to disengage the unrelated parts of a catalyst? Chemical reactions may occur more quickly or efficiently.

Stanford University materials scientists led by Jennifer Dionne have done just that by using lightweight and advanced manufacturing techniques and characterization to bring catalysts to new capabilities.

In a psychometric test, rods of palladium that were about 1 / 200th the width of human hair served as a catalyst. The researchers placed these nanoparticles over gold nanobars that focused and sculpted the light around the catalpa. This sculpted light altered the regions on the nanorods where there was a chemical reaction – which releases hydrogen. This work, published January 14 in Science, this could be an early step towards more efficient catalysts, new forms of catalytic modifications and even catalysts capable of sustaining more than one reaction at a time.

“This research is an important step in the production of catalysts elevated from the atomic scale to the reactor scale,” said Dionne, associate professor of materials science and engineering and lead author. on paper. “The goal is to understand how we can, with the appropriate shape and form, increase the reactive range of the catalyst and control the reactions that occur. it’s happening. “

Just to be able to see this reaction, a special microscope was needed, which was able to plot an active chemical process at a very small scale. “It’s hard to see how catalysts change under refraction conditions because the nanoparticles are very small,” said Katherine Sytwu, a former graduate student in Dionne’s lab and lead author of the nanoparticles. paper. “The properties of a catalpa atomic scale usually determine where transformation takes place, so it is crucial to differentiate between what is happening inside the small nanoparticle.”

For this particular reaction – and the later catalpa-controlled experiments – the microscope had to be compatible with the introduction of gas and light into the sample.

To accomplish all this, the researchers used an environmental diffusion electric microscope at Stanford Shared Facilities with a special connection, previously developed by Dionne’s lab, to bring in light. As their name suggests, diffuse electric microscopes use electrons to produce images, which allow a higher magnification rate than a classical optical microscope, and the environmental feature of this microscope means that introduce gas into an airless environment.

“Basically you have a mini-lab where you can do experiments and show what’s going on at a near-atomic level,” Sytwu said.

Under certain conditions of temperature and pressure, palladium is full of hydrogen to form hydrogen atoms. To see how light would affect this typical catalytic transformation, the researchers performed a gold nanobar normalization – designed using equipment at Stanford Nano-Shared Facilities and Stanford Nanofabrication Facility – to sit under the palladium and act as an antenna, collecting the light input and inserting it into the nearby receiver.

“First we had to understand how these materials change naturally. Then we started to think about how we could adapt and control how these nanoparticles change,” he said. Sytwu.

Without light, the most reactive points of dehydrogenation are the two tips of the nanorod. The reaction then travels through the nanorod, emitting hydrogen along the way. With light, however, the researchers were able to manipulate this reaction so that it traveled from the outer center or from one end to the other. Based on the location of the gold nanobar and the lighting conditions, the researchers were able to make different locations.

This work is one of the rare times that shows that it is possible to tweak how catalysts behave even after they are made. It opens up a huge potential for increasing efficiency at the one-catapult level. One catalyst could play a lot of space, using light to make several of the same reactions over its surface or the number of sites for reactions could increase. Light control can also help scientists avoid unwanted, unconventional reactions that sometimes happen in conjunction with the ones you want. Dionne’s most ambitious goal is to develop efficient catalysts that will be able to break down plastics at a molecular level and transform them back into the original material for recycling.

Dionne confirmed that this work, and whatever comes next, would not have been possible without the shared facilities and resources available at Stanford. (These researchers used the Stanford Research Computing Center to conduct their data analysis.) Most laboratories cannot have this advanced equipment on their own, and therefore by sharing it increases access and support of experts.

“What we can learn about the world and how we can enable the next big break is as possible with shared research platforms,” said Dionne, who is also an associate senior provost for high – search platforms / shared resources. “Not only do these places offer essential tools, but a truly amazing community of researchers. “

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Additional Stanford co-authors include former postdoctoral scholar Michal Vadai, former doctoral student Fariah Hayee, and graduate students Daniel K. Angell, Alan Dai and Jefferson Dixon.

This research was funded by the SLAC National Acceleration Laboratory; the National Science Foundation, including the Alan T. Waterman Award, U.S. Department of Energy (partly as part of the Energy Frontiers Research Center “Photonics at Thermodynamic Limits), Office of Science, Department of Materials Science and Engineering, Gabilan Stanford Graduate Fellowship, TomKat Center for Sustainable Energy at Stanford, Academia Multiple Doctoral Fellowship Program, Recruitment Excellence (DARE) at Stanford Dionne is also a Modular Faculty in Radiation, a member of the Wu Tsai Institute of Neurosciences and Stanford Bio-X, and a fellow of Precourt Power Institute.