Oxygen Atoms on Cu(100) Formed at 100 K, Active for CO Oxidation and Water−Hydrogen Abstraction, Characterized by HREELS and TPD

Abstract

The reactivity of oxygen adatoms formed by dissociative adsorption of O 2 on Cu(100) at 100 K for CO oxidation and hydrogen abstraction from water was investigated by means of HREELS and TPD in comparison with the reactivity of adsorbed oxygen in thermally stable phases. The oxygen adatoms formed on the Cu(100) surface by exposure to O 2 at 100 K, designated as as-exposed oxygen, were found to be reactive with coadsorbed CO to yield a CO 2 desorption peak at 125 K in TPD. The as-exposed oxygen atoms are suggested to be more active for CO oxidation than the oxygen atoms prepared above room temperature on Pt and Pd, which are the most active metals for CO oxidation. On annealing the oxygen-as-exposed surfaces to 300 K, a change in the loss feature of ν(Cu-O) was observed, which was indicative of formations of a pseudo c(2×2)-O phase with O(a) in 4-fold hollow sites and a ( 2×2 2)R45°-O phase comprised of -Cu-O-chains grown along the [001] direction. On these two phases, CO 2 formation in TPD was suppressed by 1 order of magnitude. Isolated oxygen atoms in the as-exposed surface are responsible for the high reactivity for CO oxidation. Hydrogen abstraction from water was also examined as a probe reaction for oxygen adatoms on different phases. The as-exposed surface and the pseudo c(2×2)-O phase were found to be reactive and OH(a) was detected by means of HREELS after subsequent exposure to water at 100 K. In contrast, the ( 2×2 2)-R45°-O phase in which oxygen atoms were incorporated into -Cu-O-chains was inert.

Polyvinylidene fluoride–trifluoroethylene as a reservoir for absorbed water

“…1, and reported elsewhere [2,[5][6][7]25]. The thermal desorption of water at 150-160 K is characteristic of water sublimation or the thermal desorption of ice from relatively inert substrates [36][37][38][39][40]. This particular adsorption species does not saturate with increasing water exposure, but continues to increase in intensity.…”

Computational study of adsorption and the vibrational properties of water on the Cu(110) surface

“…These are believed to correspond to the OH stretching bands of OH-bonds hydrogen bonded to the surface, hydrogen bonded to other water molecules and free, respectively. The bending mode is observed at 1589 cm −1 [9], 1600 cm −1 [13] and 1630 cm −1 [14] on the Cu(100) surface. The OH stretching region is observed around 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 [14].…”

“…The bending mode is observed at 1589 cm −1 [9], 1600 cm −1 [13] and 1630 cm −1 [14] on the Cu(100) surface. The OH stretching region is observed around 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 [14]. On the other hand, a structureless OH-stretching region between 3230 − 4030 cm −1 has also been reported when the intensity of the stretching modes has been below the detection limit [9].…”

Poisoning and non-poisoning oxygen on Cu(410)

“…On Cu(100), oxygen adatoms vibrate with an energy of 42 meV on the unreconstructed surface, on which they occupy the fourfold hollows, and at 36 meV when the substrate undergoes a missing row reconstruction, corresponding to an atomic O coverage = 0.5 ML [36,37]. On Cu(110), O forms added rows and vibrates at 47.5 meV for = 0.25 ML and at 48.9 meV for = 0.5 ML [38].…”