Although catalytic converters have been mandatory in cars for more than thirty years, there is still plenty of room for improvement. For example, they only work properly when the petrol engine is sufficiently warm, which is certainly not always the case with hybrid cars. Researchers from Eindhoven University of Technology and the University of Antwerp have developed a catalyst that can effectively purify exhaust gases at room temperature.
Photo: Bart van Overbeeke
The research has been published in Science.
The so-called three-way catalytic converter in the exhaust of a car consists of expensive materials and only works properly when the exhaust gases are several hundred degrees hot. As a result, when you start your car, or if you drive a hybrid car in which the petrol engine and electric motor alternate, the gases that leave your exhaust still contain the poisonous carbon monoxide. In a new Science article, scientists led by a professor Emily Hensen can now see that by adjusting the support material of the catalyst, it is possible to convert toxic carbon monoxide almost completely into carbon dioxide gas at around room temperature.
Autocatalysts are made by depositing precious metals such as platinum, palladium and rhodium in the form of nanoparticles of a few nanometers on a substrate of the material cerium oxide, or ceria. However, the precious metals are rare and expensive. Researchers worldwide are therefore working on methods to achieve the same or even better catalyst activity with less material use. Hensen’s group proved this in Previous research all that by distributing the precious metal in the form of separate atoms on the ceria support, not only is less of the expensive metal needed, but the catalyst also works better under certain conditions.
New look
In the doctoral research of Valery Muravev the researchers now shifted their focus from the metal particles to the carrier material underneath to improve the functioning of the catalyst even further. They made the ceria in different crystal sizes and immediately deposited the precious metals on it as separate atoms. They then studied how well these combinations of materials managed to bind an extra oxygen atom to carbon monoxide.
Small ceria crystals of four nanometers in size were found to be able to remarkably improve the operation of the noble metal palladium during a cold start when a lot of carbon monoxide is present. The most likely explanation for this is that the oxygen atoms are more active as the ceria crystals get smaller. Under more regular conditions, eight-nanometer ceria crystals proved to be optimal for achieving high activity at temperatures below 100 degrees Celsius.
In collaboration with the British company Johnson Matthey, which makes automotive catalysts, the scientists will now further explore how this new invention can find its way into new products.
2023-06-27 15:24:59
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