Electrode reaction rate constant

Electrode reaction rate constant k (varies) = Ij nFAY[c ... 

A conditional electrode reaction rate constant ) which is defined as the common value of the anodic and cathodic rate constants at the conditional electrode potential is given according to... 

Table 5.1 Conditional electrode reaction rate constants k° and charge transfer coefficients a. (From R. Tamamushi)... 

For the sake of a practical analysis of the polarization curve the exponential dependence of the electrode reaction rate constant need not be assumed. Then the more general form of Eq. (5.4.22) can be written as... 

Each sort of complex including the free ions has a characteristic electrode reaction rate constant (for example, kc MX., / = 0, 1,.. ., n). 

We assume that neither the preexponential factor of the conditional electrode reaction rate constant nor the charge transfer coefficient changes markedly in a series of substituted derivatives and that the diffusion coefficients are approximately equal. In view of (5.2.52) and (5.2.53),... 

Derivation of the Butler-Volmer equation in terms of electrode reaction rate constants is given in most electrochemical texts.1,3 7 15... 

Here kel is the electrode reaction rate constant, Q is the volume per one semiconductor particle (atom or molecule), which leaves the solid and penetrates into the solution, p is the concentration of holes at the interface, p = p X(y,z, t), y, z), and v is the number of holes per one particle dissolved. In the quasistationary case (i.e., when the condition v Lpfrp is satisfied) the distribution of holes is described by the equation similar to Eq. (29) ... 

A detailed examination of the mass transport effects of the HMRDE has been made. At low rotation speeds and for small amplitude modulations (as defined in Section 10.3.6.2) the response of the current is found to agree exactly with that predicted by the steady-state Levich theory (equations (10.15)-(10.17)) [27, 36, 37]. Theoretical and experimental application of the HMRDE, under these conditions, to cases where the electrode reaction rate constant was comparable to the mass-transfer coefficient has also been made [36]. At higher rotation speeds and/or larger amplitude modulations, the observed current response deviated from the expected Levich behaviour. 

Such an approach could explain, though in a semiquantitative way, the behavior of the systems studied earlier, when a minimum was observed on the kf versus solvent composition dependence. Analysis of the change in the rate of reaction, expressed as a product of the electrode reaction rate constant and the reactant concentration in the surface phase, c, in mixtures of water with acetone reveals a deep minimum, which corresponds to the greatest difference in composition of the surface and bulk phases. 

The temperature effect often disturbs precise measurements if isothermal conditions cannot be maintained and if it leads to damage of the sample. Equation 1.12 shows that at constant power density the temperature effect decreases with decreasing pulse times. Therefore, the application of short pulses may be of advantage to avoid damages. If, however, the modification of the surface requires a large amount of total energy, it should be delivered with low power density. On the other hand, there are numerous applications of the thermal heating. It can be used to evaporate or to dissociate the substrate (LAMMA) [64], to enhance reaction rates at the surface or the convection of the electrolyte [65-67]. Finally, it can be employed to study electrode reaction rate constants and the dynamics of the double layer [68]. 

In a related study, the volume of reaction, the volume of activation for diffusion (A F ff), and the volume of activation obtained from the standard electrode reaction rate constant at various pressures, have been determined for the dec-amethylferrocene (DmFc+/0) system, in several non-aqueous solvents.238 The deca-methylated ferrocene couple, rather than the unmethylated couple, was chosen. This... 

Although standard electrode reaction rate constants k are in principle obtainable from peak-to-peak separations in CVs or from extrapolations of Tafel plots to zero overpotential, the precision needed for measurement of AFei demands alternating eurrent voltammetry (ACV), in which a small AC potential of angular frequency lj is superimposed upon a DC potential ramp and the phase angle (p is extracted from measurements of the maximum in-phase and 90° out-of-phase currents.if the diffusion coefficients of the oxidized and redueed speeies are taken to be the same (D),... 

The electrode reaction rate constant depends on the difference of potentials (f) between the electrode and the site of the discharging particle. This dependence stems from the fact that the reaction involves a charge (electron) transfer from the electrode to the particle (or in the opposite direction). 

At the standard electrode potential, E, ky = k y = A , the standard electrode reaction rate constant. Therefore,... 

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