Kinetics of surface reaction

INS Ion neutralization An inert gas hitting surface is spectroscopy [147] neutralized with the ejection of an Auger electron from a surface atom Spectroscopy of Emitted Ions or Molecules Kinetics of surface reactions chemisorption... 

MBRS Molecular beam spectroscopy [158] A modulated molecular beam hits the surface and the time lag for reaction products is measured Kinetics of surface reactions chemisorption... 

Weinberg W H 1991 Kinetics of surface reactions Dynamics of Gas-Surface Interactions ed C T Rettner and M N R Ashfold (London Royal Society of Chemistry)... 

Another important catalytic reaction that has been most extensively studied is CO oxidation catalyzed by noble metals. In situ STM studies of CO oxidation have focused on measuring the kinetic parameters of this surface reaction. Similar to the above study of hydrogen oxidation, in situ STM studies of CO oxidation are often conducted as a titration experiment. Metal surfaces are precovered with oxygen atoms that are then removed by exposure to a constant CO pressure. In the titration experiment, the kinetics of surface reaction can be simplified and the reaction rate directly measured from STM images. 

The kinetics of surface reactions described in Section 8.4 for the LH model refer to reaction at a point in the particle at particular values of cA (or pA) and T. To obtain a rate law for the particle as a whole, we must take into account the variation of cA... 

In analyzing the kinetics of surface reactions, it will be illustrated that many of these processes are rate-controlled at the surface (and not by transport). Thus, the surface structure (the surface speciation and its microtopography) determine the kinetics. Heterogeneous kinetics is often not more difficult than the kinetics in homogeneous systems as will be shown, rate laws should be written in terms of concentrations of surface species. 

Finally, the application of computational methods to the study of catalysis continues to increase dramatically. C.G.M. Hermse and A.P.J. Jensen (Eindhoven University of Technology, the Netherlands) present a review of the kinetics of surface reactions with lateral interactions. These methods can be used in predicting catalytic reaction mechanisms. In particular, the authors discuss the role of lateral interactions in adsorbed layers at equilibrium and the determination of lateral interactions from experiments—using the simulations to interpret experimental results. This chapter illustrates the increasing use of computational methods to understand and to design catalysts. 

Kinetics of Surface Reactions with Lateral Interactions Theory and Simulations... 

The main progress in the theoretical study of the effect of lateral interactions on the kinetics of surface reactions in recent years has been in kMC simulations and in density-functional theory (DFT) calculations of lateral interactions. We deal with the latter in Section 3.4, and with the former in Section 3.1. Section... 

Before leaving the discussion of kinetics, two points concerning the experimental determination of reaction orders should be noted. First, the kinetics of surface reactions, in contrast to those of homogeneous systems, are temperature-dependent. This must be the case since the relative surface coverages of the reactants A and B are... 

KINETICS OF SURFACE REACTIONS 9.6.1 Steps in a Heterogeneous Catalytic Reaction... 

Any surface reaction that involves chemical species in aqueous solution must also involve a precursory step in which these species move toward a reactive site in the interfacial region. For example, the aqueous metal, ligand, proton, or hydroxide species that appear in the overall adsorption-desorption reaction in Eq. 4.3 cannot react with the surface moiety, SR, until they leave the bulk aqueous solution phase to come into contact with SR. The same can be said for the aqueous selenite and proton species in the surface redox reaction in Eq. 4.50, as another example. The kinetics of surface reactions such as these cannot be described wholly in terms of chemically based rate laws, like those in Eq. 4.17 or 4.52, unless the transport steps that precede them are innocuous by virtue of their rapidity. If, on the contrary, the time scale for the transport step is either comparable to or much longer than that for chemical reaction, the kinetics of adsorption will reflect transport control, not reaction control (cf. Section 3.1). Rate laws must then be formulated whose parameters represent physical, not chemical, processes. 

High Resolution Electron Energy Loss Spectroscopy has been "discovered" at about the same time as the previous cited techniques - die first reported experiment is related to a study of small molecules adsorbed on a (100)W surface and is dated from 1967 (1). During the last 15 years, the characterization of adsorption states of molecules on metal and semiconductor surfaces was the principal attribute of HREELS information on the elemental composition, on the chemistry, and the kinetics of surface reactions (versus temperature and/or time) were studied. One significant "plus" of HREELS is its ability to identify adsorption sites on a metal, by using the "dipole-selection rule" it is therefore possible to gain information on the short-scale structure or morphology of a surface with HREELS. 

W. H. Weinberg, Kinetics of Surface Reactions , Advances in Gas-Phase Photochemistry and Kinetics Dynamics of Gas-Surface Interactions, Eds. C. T. Rettner and M. N. R. Ashfold (The Royal Society of Chemistry, North Yorkshire, Great Britain, 1991) pp. 171-219. 

On the other hand, equation (i), based on the simple gas collision theory, gives Z, = n X 1.5 X 10". This discrepancy between the two methods must now be examined in detail, as the question of using the correct collision formula is fundamental to the interpretation of the kinetics of surface reactions. 

The effect of the electric charge on the kinetics of surface reactions was investigated in detail by Davies (49) and by Davies and Rideal (21). They showed that the effect could be studied from two aspects the varia-... 

R.B. Hall. Pulsed-Laser-Induced Desorption Studies of Kinetics of Surface Reactions. J. Phys. Chem. 91 1007 (1987). 

From the typical forms illustrated in Table 3.2 it can be seen that a number of different relationships are indicated between the partial pressure of various reactants and products and the rate of reaction. As a result, pressure or concentration is an important variable in experimentation on the kinetics of surface reactions. Conversely, the constants appearing in these equations are all strong functions of... 

FIGURE 4.8 Kinetics of surface reactions based on the Langmiur adsorption isotherm. 

Hall, R.B., Tulsed-Laser-lnduced Desorption Studies of the Kinetics of Surface-Reactions," /. Phys. Chem. 91,1007-1015,1987. 

Rosner DE. The apparent chemical kinetics of surface reactions in external flow systems Diffusional falsification of activation energy and reaction order. AIChE Journal 1963 9 321-331. 

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