L-H = Langmuir-Hinshelwood

R Rideal L-H Langmuir-Hinshelwood. Source Data from Refs. 5 and 19. 

E-R Eley-Rideal-like reaction L-H Langmuir-Hinshelwood-like reaction iiVIs Intermediates A species A on surface A excited molecule A... 

A large number of authors describe the oxidation kinetics by Langmuir—Hinshelwood type models. Depending on the particular L—H model selected, the mathematical difference between L—H models and redox models can be very small, although the former always contains more... 

In several photocatalytic reactions, a linear relation between the rate of photocatalytic reaction and amount of substrate(s) adsorbed on the surface of photocatalyst has been reported.3,1(M2) When the Langmuirian adsorption isotherm was expected, this behavior was sometimes called Langmuir-Hinshelwood (L-H) mechanism even if only a kind of adsorbed substrate was assumed. Strictly speaking, however, this is wrong, because L-H mechanism involves the surface reaction of two kinds of adsorbed species, which is not realized in photocatalytic... 

In the Langmuir-Hinshelwood (L-H) mechanism for surface-catalyzed reactions, the reaction takes place between two surface-adsorbed species [4,5], As a substitute for concentration, we use surface coverage, and the rate is expressed in this term. We consider that the elementary reaction in the L-H mechanism is the bimolecular surface reaction expressed by the following equations ... 

It has been established (38) that the dominant mechanism of the reaction is the Langmuir-Hinshelwood (L-H) mechanism ... 

The above rules can also help rationalize some of the key observations in electrocatalytic systems of great theoretical and practical importance. The example of CO oxidation on Pt in aqueous solutions is quite illustrative It is well established [117] that the activity of Pt(lll) increases dramatically in the sequence Br r HCIO4 NaOH or KOH and the oxidation ignition starts at 1.1, 0.92, and 0.65 V (versus RHE) [117]. In the latter case (0.1 M KOH), the onset of the preignition starts at 0.25 V (versus RHE), that is, in the Huppotential region. The CO oxidation proceeds via reaction between adsorbed CO and OH-in a Langmuir-Hinshelwood (L—H)-type mechanism. This implies that in alkaline solutions adsorbed OH can exist even at potentials below 0.25 V (versus RHE). 

When the activity reaches a pseudo-steady state, deactivation models with residual activity (DMRA) [23] should be used. Eti loying Langmuir-Hinshelwood (L-H) kinetics to analy2 the deactivation process, both the main reaction and the deactivation mechanisms are required to obtain the deactivation kinetic parameters. According to the literature [6,7], the following reaction mechanism can be considered ... 

The application of Langmuir isotherms for the various reactants and products was begun by Taylor, in terms of fractional coverage, and the more convenient use of surface concentrations for complex reactions by Hougen and Watson [27], Thus, the developments below are often termed Langmuir-Hinshelwood-Hougen-Watson (L-H-H-W) rate equations. 

The power law expression was widely adopted in the literature for CO oxidation [25-27]. This form is simplified from a Langmuir-Hinshelwood (L-H) expression and not suitable for small CO concentrations [30]. Therefore a full L-H expression for CO oxidation is necessary to account for a wide range of CO concentrations (Equation 27.4). The H2 oxidation was previously modeled using empirical power law rate expressions by others [29]. However, in PrOx in the presence of CO, the rate-limiting CO desorption strongly inhibits H2 and O2 adsorption and the subsequent H2 oxidation. Hence the incorporation of Pco in the H2 oxidation rate expression is necessary (Equation 27.5). The kinetics of the r-WGS reaction were well studied previously [31], in which an empirical reversible rate expression [32] is attractive due to its relative simplicity and its appropriateness in PrOx kinetic studies, as demonstrated previously [29]. 

The oxidation reaction of adsorbed CO on most metal surfaces, including Pt and Ru, takes place by reacting with oxygen-containing species OHad through a Langmuir-Hinshelwood (L-H)-type reaction to form CO2 [2, 107] ... 

Table 7.10. Langmuir-Hinshelwood (L-H), Hougen-Watson (H-W) Gas-Phase Rate Expressions L is the site density, S is an active site, Kj is either the equilibrium constant for step i or the adsorption equilibrium constant for species i, and K is the equilibrium constant...

When Langmuir-Hinshelwood kinetics are postulated, it is reasonable to expect that the rate constant will show Arrhenius temperature dependence, while the equilibrium constants will decrease with temperature for exothermic reactions. However, any deviation from this usual temperature dependence does not necessarily mean that l H kinetics are inconsistent. This point has been raised by Sinfelt et al. (1960). Consider a simple irreversible reaction the surface reaction... 

Often the surface reactions are referred to as one of two types. The Langmuir-Hinshelwood (L-H) type involves the reaction of two adsorbed molecules... 

In the case of a Langmuir-Hinshelwood (L-H) type of the reaction, where adsorbed atoms A and B react, we have the following reaction rate per unit time and surface area... 

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