Researchers at Eindhoven University of Technology have developed a new catalyst that can convert toxic carbon monoxide into carbon dioxide gas even at room temperature. The so-called three-way catalytic converter in a car’s exhaust system only works correctly when the exhaust gases are several hundred degrees Celsius. As a result, toxic carbon monoxide remains in the exhaust when starting a car or when driving a hybrid car where the petrol engine and electric motor alternate.
Modifying the Carrier Material
The catalysts in automotive catalytic converters are made by depositing noble metals such as platinum, palladium, and rhodium on a substrate of the material cerium oxide, also known as ceria. However, these noble metals are rare and expensive, so researchers are looking for ways to achieve the same or better catalytic activity using less material.
Lead author Valery Muravev and his team shifted their attention from noble metals to the carrier material underneath, ceria, to improve catalysts. They produced ceria in different crystal sizes and deposited the noble metals as single atoms in the same step. They then studied how well these materials could bind an extra oxygen atom to carbon monoxide.
The researchers found that small ceria crystals of 4 nanometers improved the performance of the noble metal palladium under cold start conditions with excess carbon monoxide. This improved performance was due to a higher reactivity of the oxygen atoms at smaller ceria crystal sizes. Under more conventional conditions, 8 nanometers was the optimal size of ceria crystals to achieve high catalytic activity at temperatures below 100° Celsius.
This research shows that it pays to look not only at the noble metals but also at the size of the particles that act as the carrier for the active materials when developing catalysts. Varying the carrier material’s particle size offers an interesting new possibility to improve catalysts, which can improve the efficiency and specificity of chemical reactions. This research is essential in the development of processes to combine carbon dioxide from ambient air with green hydrogen to produce fuels or compounds for the production of sustainable plastics.
The researchers are now working with British company Johnson Matthey, a producer of catalysts for the automotive industry, to further explore how to translate this finding into new products.
Overall, this research is a significant step towards creating more efficient and sustainable catalytic converters for cars. By modifying the carrier material of the catalyst, the researchers have found a way to convert toxic carbon monoxide into carbon dioxide gas even at room temperature, improving the efficiency and specificity of chemical reactions.