Air-cleaning crystal. The first atomic-scale images of nanocrystals that help reduce pollution show a surprising triangular, rather than hexagonal, shape. The new information should help researchers improve the chemical process. Image Credit: Phys. Rev. Lett. 84, 951 (2000)
The chemical reactions that keep sulfur and other pollutants from leaving automobile tailpipes rely on catalysts in the form of microscopic particles dispersed within the large surface area of a porous material. But the atomic-level details of these reactions are hard to study and have never been observed directly. Research published in January 2000 contains the first direct views of the catalyst that removes sulfur from gasoline and other fuels. A Danish team managed to disperse the nanocrystals on a surface in a controlled way, and their scanning tunneling microscope (STM) images revealed surprising crystal structures unlike those of larger crystals. The technique demonstrates a new way to study catalysts at the atomic scale.