Metals such as gold or platinum are often used as catalysts. In the catalytic conversion engines of vehicles, for example, platinum nanoparticles convert toxic carbon monoxide to non-toxic CO2. Because platinum and other catalytic active metals are expensive and rare, the nanoparticles involved are made smaller and smaller over time.
The “logical end” of this reduction is “single-atom” catalysts: The metal is no longer present as grains, but as individual atoms anchored on the surface of a cheaper support material. Individual atoms can no longer be defined using the rules developed from larger pieces of metal, so the rules used to predict which metals will be good catalysts need to be re- innovation – this has now been achieved at TU Wien. As it turns out, single atom catalysts based on much cheaper materials may be even more efficient. These results are now published in the journal Science.
Less is sometimes better
Only the atoms outside the metal piece can participate in chemical processes – after all, the atoms inside never communicate with the environment. To save material, so it is best to use tiny particles instead of large lumps, so that a larger proportion of the atoms remain at the surface. If we go to the maximum and use individual atoms, each atom is chemically active. Over the past decade, the field of “single atom” catalysis has grown exponentially, thriving.
Wrong model, right solution
“The reasons why some precious metals are good catalysts were already studied in the 1970s,” says Dr. Gareth Parkinson from the Institute for Applied Physics at TU Wien. “For example, Gerhard Ertl received the Nobel Prize in Chemistry in 2007 for providing atomic-level insights into catalysis.”
In a piece of metal, an electron can no longer be given to a particular atom; the electron states are the result of the interaction of many atoms. “For individual atoms, the old models are no longer relevant” says Gareth Parkinson. “Individual atoms do not share electrons as metals, so the electron bonds, which had vital energy in explaining catalysis, are not just in this case.”
So Gareth Parkinson and his team have been intensively studying the atomic mechanisms behind this single-atom catalysis in recent years. “In many cases the metals that we think of as good catalysts are still good catalysts in the form of individual atoms,” says Gareth Parkinson. , which is responsible for this. “
Custom buildings through a specific surface
An entirely new opportunity arises in single-atom catalysis that is not available when using conventional metal grains: “Depending on the surface on which we place the metal atoms and what the atomic bonds will be they form, we can alter the reactivity of the atoms “, explains Parkinson’s.
In some cases, expensive metals such as platinum may not be the best choice. “Individual nickel atoms show great promise for carbon monoxide oxidation. If we understand the atomic mechanisms of single atom catalysis, we have a lot more way to influence chemical processes,” Parkinson said.
Eight different metals have been studied in detail in this way at TU Wien – the results correspond perfectly to the theoretical models now developed in collaboration with Professor Cesare Franchini at the University of Vienna.
“Catalysts are very important in many areas, especially when it comes to chemical reactions that play a major role in efforts to develop a renewable energy economy,” stresses Gareth Parkinson. our new approach shows that platinum does not always have to be. “The surest factor is the local environment of the atoms – and if you choose it correctly, you can develop better catalysts and at the same time save resources and costs.
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Contact
Professor Gareth Parkinson
Institute for Applied Physicd
TU Wien
Wiedner Hauptstraße 8-10, 1040 Vienna
+43 1 58801 13473
[email protected]
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