Concentric ring electrodes

Related to the rotated disc electrode (RDE) is the rotated ring-disc electrfxle (RRDE). Such an electrode is illustrated in Figure 7.9 and is seen to be, in effect, a modified RDE, insofar as the central disc is surrounded with a concentric ring electrode. The gap between the ring and the disc is filled with an insulator such as Teflon or epoxy resin. The face of the RRDE is polished flat in order to prevent viscous drag, which is itself likely to cause the induction of eddy currents. 

Rotated ring-disc electrode (RRDE) Disc electrode within a concentric ring electrode. 

In this section, we consider mass transport-controlled currents to disc and concentric ring electrodes on a planar spinning disc surface. For other less common rotating electrodes, e.g. rotating hemisphere, see Table 3. 

Concentric ring electrodes are the easiest to use for measurement of surface resistivity. The resistance R between them is the sum of the resistances of the elemental annuli in series ... 

Fig. 4 The RRDE consisting of a central disk electrode surrounded by a concentric insulating annulus and a concentric ring electrode.

A photograph of the rotating ring-disc electrode (RRDE) is shown in Fig. 4.1 at the beginning of this chapter, and Fig. 4.17 also illustrates the essential features of the system. It is a view from below and shows the disc electrode surrounded by a concentric ring electrode but with a thin layer of insulating material between. 

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