Identification of the "Active Sites" of a Surface-Catalyzed Reaction

Abstract

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.

The catalytic reduction of NO by H2 on Ru(0001): Observation of NHads species

“…The diffusion ability of the species in such layers is supposed to be low and, therefore, the low-temperature systems cannot adequately represent the behaviour of the ''real-world'' ruthenium catalysts. In order to obtain some guidance for the conditions when the diffusion processes play an important role (see for instance [17]), we studied the adsorption of NO and O 2 on the Ru(0 0 0 1) surface at room and elevated temperatures. The XPS results are summarised in Fig.…”

“…The two molecular states of NO ads , threefoldbridge and on-top, could not be resolved in the N 1s core level spectra and, therefore, these states were characterised by the broad peak at 400.3 eV [9]. According to the literature [7,9,17], NO adlayer was supposed to be composed of the two molecular states, m 1 (threefold bridge) and m 2 (ontop), and the dissociation products: O ads and N ads . Two O 1s peaks at 529.7 and 531.8 eV were associated with these molecular NO ads and O ads species formed during NO dissociation.…”

“…NO on the Ru(0 0 0 1) surface has been subject of a number of theoretical and experimental studies [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], whereas less attention has been devoted to the reaction between H 2 and NO on ruthenium single crystals [11,24,25]. According to high-resolution energy electron loss spectroscopy (HREELS) and IR absorption spectroscopy (IRAS), below 200 K NO adsorbs molecularly either in threefold hollow and/or on-top positions [7,8,13,18].…”

“…At room temperature and low coverage, NO dissociates completely on the Ru(0 0 0 1) surface [9,17,20]. The dissociation takes place on the active sites with low coordination such as an atomic step [17].…”

“…The dissociation takes place on the active sites with low coordination such as an atomic step [17]. The molecular adsorption states of NO, m 1 and m 2 , are formed at high coverage [9].…”