Metal electrons and catalysis

Schwab, G.-M.

doi:10.1039/tf9464200689

Cited by 92 publications

(35 citation statements)

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“…The results of an experiment at 342°C is shown in fg. 1. The amount of decomposition which occurred in this experiment before R attained a constant value was much greater than at lower temperatures.…”

Section: Cyclohexene a N D Hydrogenmentioning

confidence: 53%

Some reactions of cyclohexene with hydrogen and deuterium on evaporated gold films

Erkelens¹,

Kemball²,

Galwey³

1963

Trans. Faraday Soc.

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The reactions of cyclohexene with hydrogen or deuterium on gold films have been investigated using a mass spectrometer to analyze the products. Reactions of oyclohexene and hydrogen between 196 and 342°C yielded cyclohexane and benzene, the proportion of the latter increasing with temperature. Activation energies for the reactions were determined and the kinetics which showed some complex features were examined at 246°C. A simple exchange reaction occurred with cyclohexene and deuterium in the range 150-240" and small amounts of cyclohexanes, initially mainly cyclohexane-t& were produced.The mechanisms of the reactions are discussed in terms of an approximate energy level diagram for the various reaction paths. Gold appears to be a relatively effective catalyst for the dehydrogenation of cyclohexene but a poor catalyst for hydrogenation of the olefm chiefly because the frequency factor of the addition reaction is low.The catalytic properties of gold have not been investigated in nearly as great detail as have those of the transition metals. The decomposition of formic acid * present address :

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Section: Cyclohexene a N D Hydrogenmentioning

confidence: 53%

Some reactions of cyclohexene with hydrogen and deuterium on evaporated gold films

Erkelens¹,

Kemball²,

Galwey³

1963

Trans. Faraday Soc.

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“…On the basis of these considerations Rfietschi and Delahay have explained for the first time the dependence of overvoltage on work function (87), observed empirically by Bockris (47). From equations [6] to [10] it follows that overvoltage can be related to various other electronic properties of the electrode metal, in particular electron concentration, surface energy (88,89), interatomic distances (90), compressibility (91), cohesion energy (92), melting point (93), and others. Bockris and Potter (47) had explained the dependence of overvoltage on work function from the fact that the Galvani potential difference of the contact interface between the metal of the reference electrode and the metal of the electrode under investigation changes with the electronic work function of this metal.…”

Section: September 1959mentioning

confidence: 95%

Overvoltage and Catalysis

Rüetschi

1959

J. Electrochem. Soc.

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Analogies between heterogeneous catalysis on solid-gas interfaces and electrochemical kinetics on solid-liquid interfaces are discussed. The surface potential of a solid-gas interface corresponds to the Galvani potential difference of a solid-liquid interface. These potentials depend to a first approximation linearly on the number of adsorbed potential-determining particles. A corresponding linear variation adsorption energy is explained on the basis of electrostatic or induced interaction between adsorbed particles. This behavior is coherent with a logarithmic dependence of the number of adsorbed particles on the bulk concentration or pressure in the liquid or gaseous phase (Temkin isotherm) and a linear dependence of the activation energy of adsorption on the number of adsorbed particles (Becker-Zeldovich equation). It is shown that the Temkin isotherm corresponds to Nernst's formula for electrode potentials and the Becker-Zeldovich equation to Volmer's equation for the rate of electrochemical reactions, and that these equations follow immediately from the theory of charge-transfer adsorption or electrostatic interaction between (activated) potential-determining species or complexes. This treatment leads to a new interpretation of the charge-transfer coefficient and of the influence of the electronic properties of the electrode material and of specifically adsorbed foreign species on hydrogen overvoltage, oxygen overvoltage, and metal deposition overvoltage.The kinetics and thermodynamics of electrochemical phenomena at solid-liquid interfaces and of catalytic phenomena at solid-gas interfaces are closely related. It is the object of this paper to point out correspondences between the two fields and to derive the fundamental laws of electrochemical thermodynamics and kinetics, in particular the Nernst equation and the Volmer-Tafel equation, from these considerations. Adsorption and InteractionThe relation between the number of adsorbed species on a solid-gas or solid-liquid interface and bulk concentration (or pressure) of the adsorbable species is described by isotherms. The Langmuir isotherm is derived on the assumption that adsorption occurs at fixed sites and that the energy of adsorption is independent of the number of particles adsorbed. Fixed site adsorption is, however, unlikely for many reactions proceeding on electrodes and catalysts. The energy of adsorption usually decreases with increasing number of adsorbed particles. The Freundlich isotherm is therefore more likely to be obeyed since it allows for the latter effect. However, very few experimental results suggest a logarithmic decrease of the energy of adsorption with increasing number of adsorbed species, as derived from the Freundlich isotherm. Very often the energy of adsorption decreases nearly linearly with the number of adsorbed particles. Such a behavior is accounted for by the Temkin isotherm. The latter can be derived for intermediate ranges of coverage from a fixed site Langmuir-type isotherm by allowing for a linear variation in adsorpt...

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“…2,4 Additionally, titanium oxide is a common support for catalysts demonstrating high selectivity toward partial oxidation. 14,18,22 The majority of proposed mechanisms for the role of titanium oxide fall into one of the following categories: (1) formation of active sites when the support wets (or "decorates") the metal particle, 23, 24 (2) oxygen (O) activation and/or spillover from chemically active defects in the support, 25 and (3) electronic mediation through various forms of charge transfer. 12, 26 Although each of these mechanisms can play an important role, this study focuses on the role of charge transfer and electronic mediation due to its importance in energy conversion reactions.…”

Section: ' Introductionmentioning

confidence: 99%