Surface Electrode Reaction Involving Interactions Between Immobilized Species

2 Surface Electrode Reaction Involving Interactions Between Immobilized Species 

The theory described in the previous chapter has been developed under provision that no interactions exists between immobilized species. However, for many experimental systems, this prerequisite is not fulfilled [85,104,105]. Hence, it is of interest to consider a case of a surface reaction involving lateral interactions. In a general case, various sorts of interactions can be assumed between O and R forms immobilized on the electrode surface [106]. The following discussion is restricted to the case of uniform interactions between immobilized species. 

To describe a surface electrode reaction in the presence of uniform interactions, besides (2.88) to (2.92), the following form of the kinetic equation is required  

The intrinsic parameter, characterizing the type of interactions, is the Frumkin interaction parameter a, which is positive for attractive forces and negative for repulsive forces. In addition, 9 = is the fraction of the electrode covered with deposited material, and f ax is the maximal surface coverage. Combining (2.93) and (2.94) with (2.102), the following integral equation is obtained as a general solution  

In the presence of interactions, besides the kinetic parameter co and the electron-transfer coefficient, the response is controlled by the interaction product a . The kinetic parameter and the interaction product can be unified into a single complex 

In the presence of interactions, besides the kinetic parameter (o and the electron-transfer coefficient, the response is controlled by the interaction product 0. The kinetic parameter and the interaction product can be unified into a single complex kinetic parameter defined as mint = e . Introducing this parameter, the solution (2.104) simplifies to that given by (2.97) valid for a simple surface reaction. Consequently, the effect of oisnt is equivalent to the effect of to, elaborated in the previous chapter. Therefore, the overall effect of interactions is quite predictable. 

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In the last two decades, significant attention has been paid to the study of surface electrode reactions with SWV and various methodologies have been developed for thermodynamic and kinetic characterization of these reactions. In the following chapter, several types of surface electrode processes are addressed, including simple quasireversible surface electrode reaction [76-84], surface reactions involving lateral interactions between immobilized species [85], surface reactions coupled with chemical reactions [86-89], as well as two-step surface reactions [90,91]. 

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