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
IDTechEx Report Unveils 3D Electronics Status and Opportunities
04/22/2024 | PRNewswire3D electronics is an emerging manufacturing approach that enables electronics to be integrated within or onto the surface of objects. 3D electronic manufacturing techniques empower new features, including mass customizability, greater integration, and improved sustainability in the electronics industry.
NASA, Japan Advance Space Cooperation, Sign Agreement for Lunar Rover
04/11/2024 | NASANASA Administrator Bill Nelson and Japan’s Minister of Education, Culture, Sports, Science and Technology (MEXT) Masahito Moriyama have signed an agreement to advance sustainable human exploration of the Moon.
Lockheed Martin Conducts Historic LRASM Flight Test
04/04/2024 | Lockheed MartinThe U.S. Navy in partnership with Lockheed Martin [NYSE: LMT] successfully conducted a historic Long-Range Anti-Ship Missile (LRASM) flight test with four missiles simultaneously in flight.
Ynvisible Appoints Felix Karlsson as Director
04/02/2024 | Ynvisible Interactive Inc.Ynvisible Interactive Inc. is pleased to announce the appointment of Felix Karlsson as a Director of the Company effective immediately.
Plasmatreat at IPC APEX EXPO 2024
04/02/2024 | PlasmatreatFor the pretreatment of highly sensitive electronic components, Plasmatreat will present a real innovation at the IPC APEX Expo in Anaheim 2024: The new REDOX tool safely and effectively reduces oxide layers on electronic components in an inline process.