Introduction into Electrochemical Kinetics

Damaskin, B. B., and O. A. Petrii, Introduction into Electrochemical Kinetics (in Russian), Vysshaya shkola, Moscow, 1975. 

Damaskin B.B., Petriy O, A. (1983) Introduction into electrochemical kinetics, Vysshaya Shkola, Moscow (Rus.). 

The large-scale spread of DAFCs is closely related to the development of efficient anodic and cathodic materials, characterized by very fast electrochemical kinetics, stability at the high current densities in alkaline environments and modest cost. This objective requires cathodes without noble metals and anodes with very low amounts of noble metals. In order to improve the cheapness and sustainability of the processes described above, the most accepted opinion is the possibility of using solar light by means of the introduction of Ti02, pure or doped, into the electrode material formulation. Figure 4.15 shows a typical laboratory-scale photoelectrocatalytic reactor. 

The connection between overtensions and electrochemical affinities, which so far has received little attention by electrochemists, is of fundamental importance and affords a most useful channel for the introduction of thermodynamic considerations into electrode kinetics. 

The study of reactive intermediates by electrochemical means, as well as the electroanalytical methods, are broad topics which cannot exhaustively be covered in a single chapter. Here, only those electroanalytical techniques which have been reduced to practical application in this field will be considered. A great deal of effort has gone into the development of methods to describe electrode processes theoretically. Only a brief introduction to the theoretical methods for handling the diffusion-kinetic problems is included. The applications discussed cover both thermodynamic and kinetic aspects of reactive intermediate chemistry and are a sampling meant to give an indication of the current state of the field. 

In order to have theoretical relationships with which experimental data can be compared for analysis it is necessary to obtain solutions to the partial differential equations describing the diffusion-kinetic behaviour of the electrode process. Only a very brief account f the theoretical methods is given here and this is done merely to provide a basis for an appreciation of the problems involved and to point out where detailed treatments can be found. A very lucid introduction to the theoretical methods of dealing with transient electrochemical response has appeared (MacDonald, 1977) which is highly recommended in addition to the classic detailed treatment (Delahay, 1954). Analytical solutions of the partial differential equations are possible only in the most simple cases. In more complex cases either numerical methods are used to solve the equations or they are transformed into finite difference forms and solved by digital simulation. 

The current situation in electrode kinetics is thoroughly presented in Vetter s book. Useful but rather specialized reviews are the recent ones by Parsons and Frumkin. Gierst s 1958 thesis and his many valuable later publications show how far an essentially nonthermodynamic point of view can penetrate into the intricacies of electrode kinetics Hurwitz s 1963 thesis adds to that of Gierst a certain amount of correlation with a thermodynamic leading thread which, however, retains the arbitrary separation of chemical and electric terms in the electrochemical potentials and the a priori introduction of transfer coefficients. 

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