Single Atoms as Catalysts
September 3, 2019 | TU WienEstimated reading time: 3 minutes
They make our cars more environmentally friendly and they are indispensable for the chemical industry: catalysts make certain chemical reactions possible—such as the conversion of CO into CO2 in car exhaust gases—that would otherwise happen very slowly or not at all. Surface physicists at the TU Wien have now achieved an important breakthrough; metal atoms can be placed on a metal oxide surface so that they show exactly the desired chemical behavior. Promising results with iridium atoms have just been published in the renowned journal "Angewandte Chemie".
Smaller and Smaller—All the Way Down to the Single Atom
For car exhaust gases, solid catalysts such as platinum are used. The gas comes into contact with the metal surface, where it reacts with other gas components. "Only the outermost layer of metal atoms can play a role in this process. The gas can never reach the atoms inside the metal so they are basically wasted," says Prof. Gareth Parkinson from the Institute of Applied Physics at TU Wien. It therefore makes sense to construct the catalyst not as a single large block of metal, but in the form of fine granules. This makes the number of active atoms as high as possible. Since many important catalyst materials (such as platinum, gold or palladium) are very expensive, cost is a major issue.
For years, efforts have been made to turn the catalysts into finer and finer particles. In the best case scenario, the catalyst could be made up of individual catalyst atoms, and all would be active in just the right way. This is easier said than done, however. "When metal atoms are deposited on a metal oxide surface, they usually have a very strong tendency to clump together and form nanoparticles," explained Gareth Parkinson.
Instead of attaching the active metal atoms to a surface, it is also possible to incorporate them into a molecule with cleverly selected neighboring atoms. The molecules and reactants are then dissolved into a liquid, and the chemical reactions happen there.
Both variants have advantages and disadvantages. Solid metal catalysts have a higher throughput, and can be run in continuous operation. With liquid catalysts, on the other hand, it is easier to tailor the molecules as required, but the product and the catalyst have to be separated again afterwards.
The Best of Both Worlds
Parkinson's team at TU Wien has is working to combine the advantages of both variants: "For years we have been working on processing metal oxide surfaces in a controlled manner and imaging them under the microscope," says Gareth Parkinson. "Thanks to this experience, we are now one of a few laboratories in the world that can incorporate metal atoms into a solid surface in a well defined way.”
In much the same way as liquid catalyst molecules are designed, it is becoming possible to choose the neighbouring atoms in the surface that would be the most favourable from a chemical point of view – and special surface-physics tricks make it possible to incorporate them into a solid matrix on a special iron oxide surface. This can be used, for example, to convert carbon monoxide into carbon dioxide.
Optimal Control
"Single atom catalysis is a new, extremely promising field of research," says Gareth Parkinson. "There have already been exciting measurements with such catalysts, but so far it was not really known why they worked so well. Now, for the first time, we have full control over the atomic properties of the surface and can clearly prove this by means of images from the electron microscope".
This research was funded by the Austrian Science Fund START prize, awarded to Gareth Parkinson in 2015.
Suggested Items
NASA Selects First Lunar Instruments for Artemis Astronaut Deployment
03/27/2024 | NASANASA has chosen the first science instruments designed for astronauts to deploy on the surface of the Moon during Artemis III. Once installed near the lunar South Pole, the three instruments will collect valuable scientific data about the lunar environment, the lunar interior, and how to sustain a long-duration human presence on the Moon, which will help prepare NASA to send astronauts to Mars.
NASA Uses ORNL Supercomputers to Plan Smooth Landing on Mars
03/26/2024 | Oak Ridge National LaboratoryA U.S. mission to land astronauts on the surface of Mars will be unlike any other extraterrestrial landing ever undertaken by NASA.
StenTech to Unveil Cutting-Edge StenTech BluPrint™ CVD Surface Treatment at 2024 IPC APEX EXPO
03/12/2024 | StenTechStenTech® Inc., a leading global company specializing in SMT Printing Solutions, will introduce the new StenTech BluPrint™ Chemical Vapor Deposited (CVD) Surface Treatment at the 2024 IPC APEX EXPO.
Lockheed Martin Awarded $219M To Produce Additional PrSM Units For US Army
03/08/2024 | Lockheed MartinThe U.S. Army has awarded Lockheed Martin a $219 million contract to produce more Early Operational Capability (EOC) Precision Strike Missiles (PrSM).
Reassessing Surface Finish Performance for Next-gen Technology, Part 2
03/04/2024 | Frank Xu, PhD and Martin Bunce of MacDermid Alpha, and John Coonrod of Rogers Corp.The introduction of 5G/6G has created a growing demand for faster rates of data transfer and operation at higher frequencies, pushing signals to travel toward the outer edges of conductors. As a result, the surface finish applied over the copper circuitry is now gaining more attention.