Electrocatalysis theoretical aspects

Theoretical aspects of mediation and electrocatalysis by polymer-coated electrodes have most recently been reviewed by Lyons.12 In order for electrochemistry of the solution species (substrate) to occur, it must either diffuse through the polymer film to the underlying electrode, or there must be some mechanism for electron transport across the film (Fig. 20). Depending on the relative rates of these processes, the mediated reaction can occur at the polymer/electrode interface (a), at the poly-mer/solution interface (b), or in a zone within the polymer film (c). The equations governing the reaction depend on its location,12 which is therefore an important issue. Studies of mediation also provide information on the rate and mechanism of electron transport in the film, and on its permeability. 

In the first part of the present review, new techniques of preparation of modified electrodes and their electrochemical properties are presented. The second part is devoted to applications based on electrochemical reactions of solute species at modified electrodes. Special focus is given to the general requirements for the use of modified electrodes in synthetic and analytical organic electrochemistry. The subject has been reviewed several times Besides the latest general review by Murray a number of more recent overview articles have specialized on certain aspects macro-molecular electronics theoretical aspects of electrocatalysis organic applicationssensor electrodes and applications in biological and medicinal chemistry. 

Leiva EPM, Sanchez C. 2003. Theoretical aspects of some prototypical fuel ceU reactions. In Vielstich W, Gasteiger HA, Lamm A, eds. Electrocatalysis. Volume 2. Chichester Wiley. 

Until recently, surprisingly little work had been done experimentally on the important aspect of coverage by adsorbed H in the kinetic and catalytic behavior of the cathodic H2 evolution reaction. Theoretically, the relation between potential dependence of coverage, 0 , of the H intermediate [see Eqs. (65) and (81)] and the mechanism and kinetics of the HER had been treated extensively, but experimentally evaluated On data to which kinetic behavior could be related remained mostly lacking until recently. It is obviously a very important aspect of electrocatalysis behavior that should be experimentally determined. 

Scherson, Palenscar, Tolmachev and Stefan provide a critical review of transition metal macrocycles, in both intact and thermally activated forms, as electrocatalysts for dioxygen reduction in aqueous electrolytes. An introduction is provided to fundamental aspects of electrocatalysis, oxygen reduction, and transition metal macrocydes. Since the theoretical and experimental tools used for investigation of homogeneous and heterogeneous electrocatalysis are considerably different, these topics are given separate discussion. The influence of the electrode surface on adsorbed macrocydes, and their influence on mechanism and rates of 02 reduction is treated in detail. Issues related to pyrolyzed macrocydes are also described. 

The practical aspects of electrocatalysis (fuel cell-oriented research) required data on the specific adsorption at electrodes with high real-surface area, while for theoretical considerations, results obtained with well-defined electrode surfaces (single-crystal surfaces) were of great importance. 

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