Adsorption atomic

Fig. VIII-9. Alteration of the structure of a Ni(llO) surface by H-atom adsorption (a) structure for 0 = 1 (b) structure for 0 > 1. [Reprinted with permission from G. Ertl, Langmuir, 3, 4 (1987). Copyright 1987, American Chemical Society.]...

Kruger S and Rdsch N 1994 The moderately-large-embedded-cluster method for metal surfaces a density-functional study of atomic adsorption J. Phys. Condens Matters 8149... 

Figure 1.5 Plot of computed reaction barriers for dissociation at Eaa. for N2 dissociation as a function of nitrogen atom adsorption energy on surface terrace and stepped surface [2]. The upper curve is for surface terrace of (111) type of fee crystals, and the lower curve presents data on the stepped surfaces.

For indirect atomic adsorption, the transition state is that of two-dimensional motion over the surface. 

Interestingly, the efficiency for producing hot electrons scales with the reaction exoergicity.64 A recent theoretical treatment of such devices has shown that the efficiency with which H-atom adsorption on Cu(lll)... 

Based on the assumption that hydrogen atoms are adsorded in pairs, instead of the expression of dissociative hydrogen atom adsorption, it s adequate to use H2 adsorption as the fractional surface coverage for the rate equation. 

Analytical technique AAS Atomic adsorption spectroscopy C Colorimetric... 

Summarizing, it is clear that the indirect interaction between adatoms has a significant effect on the chemisorption properties of the system. Most noticeably, the chemisorption energy has a damped, oscillatory dependence on the adatom separation, as first quantified in (8.1) by Grimley. Thus, multi-atom adsorption occurs preferentially with the atoms at certain sites relative to one another. 

Applications of local HSAB principle have been used for the determination of the softer regions in Si clusters by using Ga as probe atom [30a], or the site for H-atom adsorption on Si clusters. In the latter case, the isomer predicted by the Fukui function was found but it is not always the most stable one. The use of the reactivity indices is only valid when the adsorption process does not induce strong deformation of the cluster [30b]. 

For each synthesis, a reactant mixture was placed in a stainless autoclave with an agitator. The crystallization was carried out in a temperature range 90°-200°C for 20-72 h. The solid product was filtered, washed and dried. Zeolite was identified by powder X-ray diffraction measurement. Chemical analysis was conducted by atomic adsorption spectrometry. 

Electrooxidation of carbon monoxide to carbon dioxide at platinum has been extensively studied mainly not least because of the technological importance of its role in methanol oxidation in fuel cells [5] and in poisoning hydrogen fuel cells [6]. Enhancing anodic oxidation of CO is critical, and platinum surfaces modified with ruthenium or tin, which favor oxygen atom adsorption and transfer to bound CO, can achieve this [7, 8]. 

The analysis of 0-aluminas for stable cations can be made by a fusion process. The 0-alumina can be dissolved in molten Li2C03 (or K2C03), the resulting glass dissolved in dilute nitric acid, and the solution analyzed by atomic adsorption. Activation analysis or X-ray fluorescence analysis also can be used. 

For each cluster size, the few lowest energy equilibrium isomers with molecular adsorption (MA) and two atoms adsorption (TAA) complexes are represented in Fig 8. Most of these structures are planar or near planar. For 4c, 5b, and 5d, only an O atom is not in the plane. Two atom adsorption leads to major structural changes in the gold cluster, particularly for n>5. For example, in the structures 5a, 6a, and 7a, a gold atom breaks the bonds to other Au atoms to form a highly stable linear O-Au-0 unit which bind each 0 atom to one of the remaining Au atoms. On the other hand, molecular adsorption induces only a modest relaxation in the host cluster, and the O2 molecule is attached on top of a Au atom preferably to the bridge position between two Au atoms. 

Turning to metal substrates, in most cases of atomic adsorption on metal surfaces where the adsorption geometry has been determined (cf. Table 6.1), only one adsorption site is involved, i.e., all adatoms have identical surroundings [the exceptions are Ni(l 11)... 

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