Tafel dependencies

Assuming that solid-state electrochemical processes involved in our voltammetry of microparticles analysis satisfy Tafel dependence between current and potential at the rising portion of voltammetric curves, the current can be approached by the expression... 

Relative quantitation can also be obtained from voltammetric data in the case of strongly overlapped peaks using generalized Tafel analysis of the rising portion of voltammetric curves. For quantitation of a mixture of two components, X and Y, one can combine the Tafel dependence for individual components ... 

In other words, in the kinetic regime with a predominant simple Tafel dependence a change in I by a factor of k shifts polarization losses by — Mn/c. i is the most important parameter here, and a larger active surface due to increased thickness improves the performance. 

In electrochemical kinetics, this model corresponds to the Butler-Vohner equation widely used for the electrode reaction rate. The latter postulates an exponential (Tafel) dependence of both partial faradaic currents, anodic and cathodic, on the overall interfacial potential difference. This assumption can be rationalized if the electron transfer (ET) takes place between the electrode and the reactant separated by the above-mentioned compact layer, that is, across the whole area of the potential variation within the framework of the Helmholtz model. An additional hypothesis is the absence of a strong variation of the electronic transmission coefficient", for example, in the case of adiabatic reactions. 

The quantitative theory also has to take into account a variation of the reaction volume with the electrode charge [65]. Another weak point of the model (24) is the hypothesis of the Tafel dependence on the potential difference across the compact layer. Quantum-mechanical estimates [64] testify in favor of a considerable variation of the charge-transfer coefficient, a, over the wide potential range explored experimentally, or even its approach to zero, which corresponds to the activationless regime of the charge-transfer process [66]. Recent analysis which has included these... 

In the latter case, we have two unknown parameters. If one of them is significantly higher than the other one, it can be rejected. Hence, in this case, the R f is determined by the lower exchange current density. Additional information about these two parameters can be obtained from other data, for example, from Tafel dependencies, which were analyzed earlier. Concluding the discussion of this method, we present an example of an experimental research of Cu Cu(II), glycine system (Figure 5.6). 

A kinetic regime at small current densities, y o 7, with simple Tafel dependence, t)o bln (jo/J ) in this regime, transport limitations of any kind are... 

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