Overlayer ordering induced by carbon monoxide adsorption on potassium pre-covered Ni(100)

doi:10.1016/0039-6028(94)91474-5

Surface Science

Volumes 307–309, Part B, 20 April 1994, Pages 668-673

https://doi.org/10.1016/0039-6028(94)91474-5 Get rights and content

Abstract

Room temperature adsorption of CO on K pre-covered Ni(100) surfaces causes a strong ordering effect, as observed using low energy electron diffraction. This suggests formation of crystalline K/CO overlayers, even at very low K and CO coverages. The results are compared with recent models of the coadsorption process.

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Cited by (7)

Temperature effects on the coadsorption of K-CO on Ni(100)
2000, Surface Science
High-resolution electron energy-loss spectra of the coadsorption of potassium and CO on the Ni(100) surface show the role of temperature in driving chemical species along the surface towards the formation of ordered islands made of alkali atoms and CO species. At low potassium precoverages, the formation of K–CO islands occurs by heating the sample to 420 K. On the contrary, for a potassium coverage near 0.38 ML, K–CO patches of ordered phases grow spontaneously even at 220 K. The interpretation of the present data relies essentially on two literature works on the K–CO/Ni(100) system, one of them presenting calorimetric measurements and the other reoprting the theoretical temperature behaviour of the chemical species on the nickel surface.
CO adsorption on c(2 × 2)-Li/Cu(100): interaction between CO and Li on unreconstructed Cu(100) surfaces
2000, Surface Science
Citation Excerpt :
The most classical interpretation is that the electron from the alkali metal flows to CO 2π∗ antibonding orbital through the substrate. Formation of a stable CO–alkali metal complex with direct chemical interaction [1–6], formation of a two dimensional CO–alkali metal lattice stabilized by the Madelung effect [7–12], and changes of CO adsorption site [13–15] are also considered in the interaction of CO with alkali metals. As a result of the heat of adsorption measurement of CO/K/Ni(100), Al-Sarraf et al. [9] concluded that charge transfer to CO 2π∗ increased the heat of CO adsorption by 70 kcal/mol and that electrostatic interaction due to the reionization of K increased the heat of CO adsorption by 125 kcal/mol, where adsorption of CO made the metallic K overlayer cationic at high coverage.
CO adsorption on the Cu(100)-c(2×2)-Li surface was studied using high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED) and temperature programmed desorption (TPD) to examine the interaction between CO and Li and the properties of an Li–CO complex on unreconstructed Cu(100) surfaces. The ν(CuLi) peak appeared at 310 cm⁻¹ for the c(2×2)-Li surface with unreconstructed Cu substrate, in addition to a peak at 710 cm⁻¹ which was not observed on the Cu(100)-(2×1)-Li surface with a missing-row structure. CO stretching modes appeared at 1200, 1860 and 2040 cm⁻¹ when the c(2×2)-Li surface of 0.3 ML Li coverage was exposed to CO at 130 K. It is considered that these correspond to the Li–CO complex and CO molecules adsorbed at bridge and atop sites respectively. The 1200 cm⁻¹ peak decreased in intensity when the surface was almost saturated with CO. It was proved from the result of the experiment using ¹³C¹⁸O that the Li–CO complex collapses and changes to the CO adsorbed at atop and bridge sites. The ν(CO) of 1200 cm⁻¹ observed in the present study comes in the category which is the lowest among systems of other alkali metals, whereas the CO desorption temperature rises only by 15 K.
HREELS investigation of CO-K coadsorption on Ni(111)
1997, Surface Science
The coadsorption of CO and K on Ni(111) has been studied by high-resolution electron energy-loss spectroscopy. We used three precoverages, one of them (0.25 ML) corresponding to an ordered surface overlayer (p(2 × 2)) and the other two (0.3 and 0.47 ML), to an incommensurate and a disordered surface layer, respectively. Different local CO adsorption arrangements are suggested for each K coverage. The vibrational spectra show features at 27, 180 and 210 meV. The loss at 27 meV is related to a vibration of the reconstructed Ni(111) surface due to the p(2 × 2)-K layer and is damped by 3 L of CO. For the other two K precoverages, that loss exists regardless of the amount of CO. The losses at 180 and 210 meV are assigned to the CO stretching vibration corresponding, respectively, to the occupation of only one or both sites of the same p(2 × 2)-K cell. The CO saturation of the $p (2 × 2)- K Ni (111)$ surface gives rise to a short-range interaction among CO molecules as well as between each K atom and CO molecules, which causes an overall shift of the CO stretching frequency towards higher loss energies.
Structural studies of alkali metal adsorption and coadsorption on metal surfaces
1996, Surface Science Reports
The study of the adsorption and the coadsorption of alkali metals on single-crystal metal surfaces is a very active sub-field of surface science, partly because of the importance of technological applications (promotion of catalytic reactions, enhanced oxidation, increases in electron emission rates), but also because of the fundamental interest in how these “simple” adsorbates modify the surface. In the past few years there has been a marked increase in the number of structural studies of alkali adsorption and coadsorption systems, motivated in part by developments in theoretical models of adsorption. This article reviews recent studies of alkali adsorption and coadsorption using specifically structural techniques, with the intention of highlighting recent developments, providing a useful reference base to the community, and drawing attention to some unifying concepts.
Formation of ordered islands in CO adsorption on K pre-covered Ni(100) surfaces
1995, Chemical Physics Letters
Coadsorption of CO on a K pre-covered Ni(100) surface leads to the formation of small ordered KCO islands. evidenced by scanning tunnelling microscopy. Structural models of these islands are presented, consistent with these and previous results. In a recent study of this system by Christensen and Nørskov, two configurational ‘strategies’ (I and II) were employed within an electrostatic framework to model microcalorimetry data. These STM findings clearly support this electrostatic model and favour the rearrangement of K atoms adopted in strategy II, but with limited K diffusion.
Changes in oxygen Auger spectra induced by potassium in the Ni(100)-O/K coadsorption system
1995, Journal of Electron Spectroscopy and Related Phenomena
Adsorption of potassium on an oxygen-covered Ni(100) surface produces changes in the O KLL lineshape at all oxygen sub-monolayer coverages. The observed change is clearly K-coverage dependent. It is known that the O KLL Auger spectrum of chemisorbed oxygen is predominantly atomic-like with a band-like feature appearing at higher kinetic energy. The main effect induced by a gradually increased potassium coverage is a decrease in the intensity of this band-like structure. This result can be ascribed to an increase in the ionic character of the chemical bonding of the oxygen. On the other hand, the energies and relative intensities of the lines in the atomic-like part of the spectrum are substantially unchanged.

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Overlayer ordering induced by carbon monoxide adsorption on potassium pre-covered Ni(100)

Abstract

Surf. Sci.

Surf. Sci.

Surf. Sci.

Appl. Surf. Sci.

Surf. Sci.

Chem. Phys. Lett.

Solid State Commun.

Surf. Sci.