Marie Curie Actions: Inspiring Researchers - Imdea

Catalysts in close-upKnowing her materials in every minute detail is a necessityfor Dr Hungría in her quest to understand the full potential ofcatalysts. It is not only the chemical make-up, but also thetopography of a catalyst – the catalytic particles’ size, shapeand structure – which determine its effi ciency.Precious, precious particles‘Catalysts are usually composed of very precious metals,for instance, gold or platinum,’ she explains. ‘You have tosynthesise your catalysts in such a way that you have themaximum number of atoms on the surface of your particles.If the gold particles are very large, for instance, the catalystwill be very inactive, but if you have very small gold particles,a lot of atoms of gold on the surface, they can react easily.’During her Marie Curie Fellowship, Dr Hungría was able toget a very close look at the structure of a variety of catalystsbased on cerium zirconium oxide with palladium and nickelas their active component. ‘This cerium zirconium mix is usedin three-way catalysts, the kind of catalysts that you have inyour car,’ she clarifi es. ‘These catalysts convert the carbonmonoxide in the exhaust emissions into carbon dioxide (CO 2).Hydrocarbons also get converted into CO 2and nitrogen oxidesinto nitrogen, turning all of them into less toxic gases than wehad to begin with.’ The fi ndings of Dr Hungría’s Marie Curie‘Catalysts Tomography’ project might therefore ultimatelyhelp to improve the performance of catalytic converters inmodern cars, further cleaning the most noxious gases fromcar exhaust fumes.Twists and turns for a better pictureThe technique Dr Hungría used to take this close look ather catalysts is called electron tomography and, accordingto Dr Hungría, ‘the best lab in the world for doing electrontomography of materials’ can be found right there on thehistoric campus of Cambridge University in the UK. In 2001,the Electron Microscopy Group at Cambridge showed thatit was possible to create three-dimensional (3D) images ofcrystalline, high-atomic-number materials using a special set-upin a scanning transmission electron microscope (STEM) which3D reconstruction of ‘cubic’ CeO 2nanoparticles, showing mainly (002) planes. The tilt series of images was acquired every 2 degrees from-70º to +74º on a 200 kV FEI Tecnai F20-G2 TEM/STEM microscope.25