Electrocatalytic reactions, general consideration

For simple one-electron redox reactions, in which Ox and Red both remain in solution, the charge transfer coefficients a are often foxmd to be approximately 0.5 for more complex reactions they vary considerably. Thus, an electrocatalytic effect can not only express itself in a change in io, but also by affecting a (i.e. in general by changing the reaction pathway). This is schematically indicated in Fig. 5.39. A generalized expression for the exchange current density is... 

Electrocatalytic processes have received considerable attention in the last decades because of their application in synthesis and sensing. The term catalysis is used for describing the modification in the reaction rate of a given chemical reaction by effect of the addition of a catalyst species. Two essential conditions have to be accomplished by catalytic processes the thermodynamics of the reaction becomes unaltered, and the catalyst stays unchanged. Additionally, a common demand for catalysis is that the catalytic process involves small concentrations of the catalyst. In the most general view, the rate of the reaction can be either increased (positive catalysis) or decreased (negative catalysis), although, obviously, positive catalysis is preferentially desired. 

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