A Virginia Tech discovery shows an efficiency rate that is up to 25 times higher than traditional catalysts made from larger iridium structures or nanoparticles.

Catalysts are materials widely used in industry to speed reactions for making gasoline, pharmaceutical drugs, and for cleaning up car exhaust. They typically contain expensive precious metals, which can make manufacturing and processing costs economically unattractive.

One class of catalysts, the single-atom catalysts, makes efficient use of the expensive metal by supporting it as isolated atoms on another cheaper material. Until now, the structure of those isolated atoms during the oxidation of carbon monoxide to carbon dioxide was not known.

Ayman M. Karim, associate professor of chemical engineering and Hongliang Xin, assistant professor of chemical engineering, both in the Virginia Tech College of Engineering, have identified the structure of iridium single-atom catalysts for carbon monoxide oxidation. The identification of the structure and reaction mechanism will help in the design of better and more cost-efficient catalysts.

In the journal article “Identification of the Active Complex for CO Oxidation Over Single- Atom Ir-on-MgAl2O4 Catalysts,” published in Nature Catalysis, the discovery shows an efficiency rate that is up to 25 times higher than traditional catalysts made from larger iridium structures or nanoparticles.

Representative STEM images of Iridium SAC. STEM images of 0.0025% Ir/MgAl2O4 (SAC) after reduction at 500°C. (a) high magnification and (b) low magnification, (c, d) after CO oxidation. Single atoms are identified by white circles. Image Credit: Karim, Xin at Virginia Tech. Click image for the largest view.

Karim said of the research that was funded by the Army Research Office, “Seeing a single atom catalyst at work shows how a chemical reaction can be simple from afar, yet still complex to understand as we dive into the atomic level details. However, uncovering those details paves the way for designing more efficient catalysts.”

Yubing Lu and Jiamin Wang, both doctoral students in the department of chemical engineering at Virginia Tech, contributed to this study. Lu led the experiments while Wang was responsible for the computational work.

Lu explained, “This study provides very detailed atomic level information on the structure and activity of supported noble metal single atoms. We applied different characterization tools and quantum chemical calculations to show how a single atom catalyst works.”

Research collaborators include Simon R. Bare, distinguished staff scientist at the Stanford Synchrotron Radiation Light Source, and scientists from the Pacific Northwest National Laboratory.

Iridium is showing up more and more often in catalyst research. A 25 fold increase is only going to accelerate the research and applications as well as cut the amount per application. This is news, indeed.


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