Theory of slow discharge

This conclusion is in complete agreement with the experimental results. Figure 6.1 shows the S vs n dependence for different solutions, viz. for a surface-inactive electrolyte, and for solutions to which specifically adsorbed anions and cations have been added. It can be seen that the results for different solutions differ considerably. If, however, we assume, in accordance with the usual equations of the theory of slow discharge[1], that the change in overpotential at a constant concentration of H" " ions is exactly equal to the change in the local -potential (the coefficient (1 - a)/a of the ij -poten-tial is equal to unity, since a = 1/2 in the Tafel regions for the investigated solutions), the displacement of one curve with respect to the other by the difference in overpotentials enables us to... 

Analysis of the main equation of slow discharge theory shows that two cases are possible. For example, when deviations from the equilibrium are small (i.e. when... 

In 1930, Max Volmer and Tibor Erdey-Griiz used the concept of a slow discharge step for cathodic hydrogen evolntion (slow discharge theory). According to these ideas, the potential dependence of electrochemical reaction rate constants is described by Eq. (6.5). Since hydrogen ions are involved in the slow step A, the reaction rate will be proportional to their concentration. Thus, the overall kinetic equation can be written as... 

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 ... 

Frumkin has combined this reasoning with his theory of the slow discharge [49] to derive the expression for the rate of an electrochemical reaction [50-52], for example, for the cathodic component of... 

At first, however, it seemed that the slow discharge theory was irreconcilably at variance with experimental data since in solutions of pure acids the hydrogen overpotential was found to be independent of the acid concentration. This inconsistency was solved in Frumkin s classical work in which he took into consideration the effects of the double-layer structure on the discharge rate. The numerous studies by Frumkin and his coworkers, as well as the work of other electrochemists, that followed, have provided experimental proof of the limited rate of electrode reactions involving transfer of a charge across the metal-solution interface. 

Krishtalik LI (1957) A contribution to the slow discharge theory, Zh Fiz Khim 31 2403-2413 (1959) Velocities of the elementary stages of the hydrogen evolution mechanism on the cathode I, Zh Fiz Khim 33 1715-1725... 

We want to note that we obtained the main equation of the slow discharge theory based only on principles of formal kinetics and without any models of the elementary... 

Recently, Plonski analyzed the ability of the theory of electromechanical removal of adsorbed anions to fit the experimental initial and steady-state polarization curves of active iron in acid media. Unlike Drazic and Drazic, the author applied the concept of electrochemical dissolution of vulnerable atoms to a mechanism consisting in a slow-discharge hydrogen evolution and a one-step ferrous ion formation. In order to distinguish the possible role of anions from any other interferences, the... 

Thus, in the upper part of the polarization curve, the hydrogen overpotential is found to depend strongly on the solution composition. This can be explained on the basis of the theory of a slow ordinary discharge or electrochemical desorption. 

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