Studies of Reactions at Surfaces

	Areas of Research - Examples
	Studies of Liquids
	Electronic Structure and Dynamics      of Surface Systems
	Studies of Reactions at Surfaces
	Surface structure, dynamics & magnetism
	Studies of surfaces with X-ray diffraction
	Environmental and materials research
	Studies of Protein Crystals
	Studies of Molecule Structures      with SAXS
	Microscopes - IR & PEEM
	Accelerator Physics
	Nuclear Physics
	Activity Reports from MAX-lab
	Seminars at MAX-lab
	Go to start Research at MAX-lab

Everyone knows that iron rusts, and copper turns green-blue when left outside. Similarly, we know that catalytic converters in cars help to clean up the gases that leave the exhaust. These are but a few examples of chemical reactions occurring at the surface of a material, where gases can interact most easily with the atoms of the solid. Sometimes this is unwanted (in the case of rust), other times these processes are useful and can help to create cleaner end-products, new fuels, useful nutrients, or even help to explain what happens to the ozone layer. Finding out the how and why can help us create better products for the future, which means that one question has to be answered: what exactly happens at the surface during these reactions? At beamline I311 a large part of the experiments is devoted to just that: studying the precise interaction of various gases at metal and oxide surfaces.

In order to do that, we have to start with a clean surface, but surfaces are in fact so reactive that they need to be studied in ultra-high vacuum. Most materials can be cleaned by bombardment with argon ions (like sandpaper, it removes the outer layers), and then heated to allow the atoms to form a well-ordered surface again. Using X-rays we can then excite the electrons from the solid, and map them according to their kinetic energy as they come out. And here lies the simple beauty of the photoemission method: each different atom (iron, copper, platinum, oxygen etc.) has its own unique “electronic fingerprint”, which not only depends on the type, but also on the environment: atoms at the surface are different from bulk atoms and, for example, clean iron is different from oxidized iron. Studying these electronic fingerprints at different temperatures, different surface compositions, gas pressures and mixtures can therefore tell us what the underlying mechanism of a reaction is, and how to optimise it. This is in fact of such importance that the 2007 Nobel Prize in chemistry was awarded to Gerhard Ertl, who is one of the pioneers in this field of surface science.

Other areas of surface science that are studied on I311 include organic molecules and their interaction with surfaces (see also: Electronic structure and dynamics of surface systems), various surface reconstruction patterns, layered intercalation compounds and different resonant processes that can be activated by X-rays.

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