Kinetics of Electron Transfer at the Metal-Liquid Interface

1 Kinetics of Electron Transfer at the Metal-Liquid Interface 

In this section we only consider electron transfer processes between a redox couple dissolved in the electrolyte and an inert metal electrode such as platinum. Here an inert electrode means that we work in a potential range where essentially no other electrochemical reactions take place. Considering a single electron transfer step as given by 

As already mentioned in the introduction to this chapter, kinetic models describing electron transfer processes at metal electrodes, had been used for a long time before Marcus developed his theory. At a fairly early stage a transition state model was applied the rate constants were described in terms of an activation energy so that we have 

Considering now the equilibrium case, the two partial currents given in Eq. (7.2) must be equal = / ). Substituting Eq. (7.3) into (7.2), one obtains after rearranging the equation 

The transition state is shown in Fig. 7.1 in terms of a free energy-reaction coordinate diagram. It is useful to also consider the same type of diagram under standard conditions 

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