No abstract

No abstract

No abstract

The structure of RuO(2)(110) and the mechanism for catalytic carbon monoxide oxidation on this surface were studied by low-energy electron diffraction, scanning tunneling microscopy, and density-functional calculations. The RuO(2)(110) surface exposes bridging oxygen atoms and ruthenium atoms not capped by oxygen. The latter act as coordinatively unsaturated sites-a hypothesis introduced long ago to account for the catalytic activity of oxide surfaces-onto which carbon monoxide can chemisorb and from where it can react with neighboring lattice-oxygen to carbon dioxide. Under steady-state conditions, the consumed lattice-oxygen is continuously restored by oxygen uptake from the gas phase. The results provide atomic-scale verification of a general mechanism originally proposed by Mars and van Krevelen in 1954 and are likely to be of general relevance for the mechanism of catalytic reactions at oxide surfaces.

9. H. Rau, Chem. Rev. 83,535 (1 983). 10. Small amounts of an optically active guest molecule added to a nematic host can induce a cholesteric phase, and the helical organization (pitch) in the mesoscopic system is sensitive to modifications in the chiral guest molecule [G. Solladie and R. G. Zimmemann, Angew. Chem. h t Ed. Engl. 23, 348 (1 98411. 11. Recently, photochemical switching between LC phases through use of diastereomeric photoresponsive guest molecules was shown [B. L. Feringa, N. P. M. Huck, H. A. van Doren, J. Am. Chem. Soc. 117, 9929 (1 99511. 12. J. Jacques, A. Collet. S. Wilen. Enantiomers, Racemates and Resolutions (Wiley, New York, 1981). 13. We thank R. M. Kellogg, H. A. van Doren, and J. van Esch for usefull comments.