Frumkin theory

The Frumkin theory of the effect of the electrical double layer on the rate of the electrode reaction is a gross simplification. For example, the electrode reaction does not occur only at the outer Helmholtz plane but also at a somewhat greater distance from the electrode surface. More detailed considerations indicate, however, that Eq. (5.3.20) can still be used to describe the effect of the electrical double layer as a good approximation. 

The values of k°a have been corrected for the double layer in a KC1 medium (as 2 data were available only in this medium) by applying the Frumkin theory. They are given in Table 6. 

The ka values in chloride, bromide, and percholate media have been corrected by applying the Frumkin theory for the double-layer... 

The k°a values in KF, KC1, and KBr have been corrected by applying the Frumkin theory for the double-layer correction as cf>2 data were available in the literature for these media. The k°t values obtained in Cl and Br media correspond to CdCl+ and CdBr complexes, respectively, as they correlate93 with corrected values... 

The Frumkin theory with Eqs. 17-18 presents the first improvement of the Szyszkowski-Langmuir theory and is shown in Pig. 1 by the thick line. The Frumkin theory requires input for the surfactant interaction parameter... 

To resolve the problem of negative /3 values obtained with the Frumkin theory, the improved Szyszkowski-Langmuir models which consider surfactant orientational states and aggregation at the interface have been considered [17]. For one-surfactant system with two orientational states at the interface, we have two balances, i.e., Ft = Fi + F2 and Ftco = Ficoi + F2C02, which can be used in conjunction with Eq. 24 to derive two important equations for determining the total surface excess and averaged molecular area required in the calculation of surface tension, i.e.,... 

This equation is known as the Frumkin equation, expressing the Frumkin theory. It shows the corrections which have to be made to a current-potential curve because of the presence of the double layer. However, it has two drawbacks. The first is that the site of reaction is identified with the plane of closest approach. In solutions of several components there are several such planes and the reaction site need not necessarily coincide with any of them. The second drawback is that this theory was developed for a simple, one step reaction and cannot be applied generally. However, equation 4.107 does provide us with some understanding of the influence of the value of < o... 

Frumkin, A., Bemerkung zur Theorie der WasserstofRiberspaimung, Z. Phys. Chem., 160A, 116 (1932). 

These modifications are known as the Frumkin double-layer corrections. They are useful when the electrolyte concentration is sufficiently low, so that fa can be calculated from Gouy-Chapman theory, and the uncertainty in the position of the reaction site is unimportant. Whenever possible, kinetic investigations should be carried out with a high concentration of supporting electrolyte, so that double-layer corrections can be avoided. 

As was mentioned in the introduction, Frumkin and his group [Kuchinsky et al. (107) and Frumkin et al. (10 )] proposed an electrochemical theory, according to which the adsorption of electrolytes by carbon would be determined by the electrical potential at the carbon-solution interface, and by the capacity of the double layer. At higher concentrations some physical adsorption of acid might occur in addition. 

The opposing theories were reviewed in detail by Garten and Weiss (73, 111). To summarize the facts acid is adsorbed only in the presence of oxygen (16), the adsorption is dependent on oxygen pressure, at least at low pressures (22,112), and a part of the adsorbed acid can be removed by solvents such as toluene (109, 111). According to Burstein and Frumkin (113), hydrogen peroxide is liberated when acid is ad.sorbed in the presence of oxygen ... 

The adsorption of some neutral organic compounds on the individual faces of zinc single-crystal electrodes was described by the Frumkin-Damaskin theory with the use of two parallel capacitors model [14]. For pc-Zn electrode, a departure from the two parallel capacitors model due to the energetic inhomogeneity of the surface was observed. 

V. G. Levich spent a major part of his career in the world s largest institute of physical electrochemistry, The Frumkin Institute in Moscow. He was a man who had the good fortune to create a subfield in science and to dominate it during his lifetime. The field concerned is hydrodynamics applied to the relative movement of the solution near an electrode. His early work is encapsulated in a famous book Physicochemical Hydrodynamics, which was finally published in English only in 1962. The most useful equation in this book is one used in this section [Eq. (7.112)]. Later, he was persuaded by Frumkin to apply his talents to the quantum theory of charge transfer, where he led a research group of some twenty-five members. 

Significantly later, foreign scientists reached a similar conclusion regarding the Freundlich isotherm. In the USSR, a theory of adsorption on an inhomogeneous surface was developed independently by M. I. Temkin of the Karpov Physico-Chemical Institute in connection with electrochemical research by Academician A. N. Frumkin. M. I. Temkin s work on a logarithmic isotherm was cited in [74] and published in [75]. The theory of adsorption and catalysis on an inhomogeneous surface was especially extensively developed by S. Z. Roginskii. 

This empirical equation of the adsorption isotherm, giving the relationship between 6 and the pressure, excellently represents many characteristics of chemisorption. Equation (72) is introduced by Frumkin and Slygin (366), who derived it from their electrochemical investigations on hydrogen electrodes. The equation has played an extensive role in the successful theory of ammonia catalysis of Temkin (367) and it has in literature been termed the Temkin equation (368), although Temkin himself and other Russian investigators call it the logarithmic adsorption isotherm. 

For the better or for worse, Frumkin s electrochemical theory of adsorption has played an important role in carbon electrochemistry research, especially in the prolific literature from the former Soviet Union. It can be summarized as follows [80,81] ... 

The Frumkin epoch in electrochemistry [i-iii] commemorates the interplay of electrochemical kinetics and equilibrium interfacial phenomena. The most famous findings are the - Frumkin adsorption isotherm (1925) Frumkin s slow discharge theory (1933, see also - Frumkin correction), the rotating ring disk electrode (1959), and various aspects of surface thermodynamics related to the notion of the point of zero charge. His contributions to the theory of polarographic maxima, kinetics of multi-step electrode reactions, and corrosion science are also well-known. An important feature of the Frumkin school was the development of numerous original experimental techniques for certain problems. The Frumkin school also pioneered the experimental style of ultra-pure conditions in electrochemical experiments [i]. A list of publications of Frumkin until 1965 is available in [iv], and later publications are listed in [ii]. 

Frumkin s slow discharge theory — had been first proposed in 1933 [i] for taking into account the role of reaction layer structure in electrode kinetics. The theory is based on the potential dependence of the - activation energy AG ... 

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