Sometimes chemical reactions in the lab work the way you imagine them to, and sometimes they don't. Neither is unusual. What is highly unusual, however, is what a research team at TU Wien has now observed when studying hydrogen oxidation on a rhodium catalyst: The surface of a rhodium foil can be highly chemically active in some surface regions, while in others, only a few micrometers away, it is completely inactive, and still in others oscillations between the active and inactive state occur. Such behavior was previously thought to be almost inconceivable. The results, which have now been published in the scientific journal Nature Communications, show that catalysis is more complicated than previously thought.