Andrieux-Saveant characteristic currents

In their work, Andrieux and Saveant analyse the behaviour in terms of the characteristic current densities for each process. This has the advantage that, in general, the expressions for these characteristic current densities are fairly straightforward and obvious and, therefore, easily derived. In the case where the different processes involved are strictly first-order, the reciprocal of total current density can be obtained by combining the reciprocals of the current densities for the individual steps. For example, the limiting current density, //., for a reaction at the surface of a rotating disc coated by a permeable membrane is given by... 

This system of equations appear to be quite different from those proposed by Albery and Hillman/ but it is exactly equivalent. We can numerically resolve these expressions to obtain currents ii and I z in terms of the characteristic currents ip, is, and i - However Andrieux and Saveant adopted an approach similar to Albery and Hillman and identified a number of rate-limiting situations associated with rate... 

To apply the Andrieux-Saveant model, we must determine each of the characteristic currents. We note from Fig. 2.24 that can be readily determined, since the substrate is easily oxidized at the bare glassy carbon electrode. This value depends on the value of the substrate concentration used and the rotation speed. Typical values are given in Table 2.9 for aqueous perchlorate media. They exhibit a large range of values typically from 37-408 /lA cm . The value of is, the characteristic... 

Table 20.4 Characteristic Currents in the Andrieux-Saveant Model for Redox Catalysis at Polymer-Modified Electrodes...

Figure 2. Characteristic current densities defined according to Andrieux-Saveant theory.

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