Rotated ring-disc electrode

Here we have to deal with three types (see Fig. 3.68), viz. (a) the rotating disc electrode (RDE), and (b) the rotating ring electrode (RRE) and the rotating ring-disc electrode (RRDE). The construction of the latter types suits all purposes, i.e., if the disc or the ring is not included in the electric circuit, it yields an RRE or an RDE, respectively, and if not an RRDE, where either the disc forms the cathode and the ring the anode, or the reverse. 

The Controlled-Convection Techniques The Rotating Disc and Rotating Ring-Disc Electrodes... 

The controlled-convection techniques the rotating disc and rotating ring-disc electrodes... 

There arc many controllcd-convection techniques available but we will restrict our discussion to the two most commonly employed by the electrochemist the rotating disc electrode (RDE) and the rotating ring disc electrode (RRDE). 

To learn that the rotated ring-disc electrode (RRDE) is one of the most powerful analytical tools for following the kinetics of fast homogeneous reactions. 

Figure 7.9 Schematic representation of a rotated ring-disc electrode, defining the radii ri (the radius of the disc), and rj and rs (the inner and outer radii of the ring, respectively).

The rotated ring-disc electrode (RRDE) has been shown to be an ideal tool for measuring the rate constants of very fast homogeneous reactions. In this method, we start with one reagent in the solution while the other is electrogenerated at the disc electrode, with the proportion of the latter that remains after reaction being monitored at the ring electrode. 

Albery, W. J. and Hitchman M. L., Ring-Disc Electrodes, Oxford University Press, Oxford, 1971. This now-classic book describes one of the most formidable tools in the arsenal of the electroanalyst, i.e. the rotated ring-disc electrode (RRDE). Its first two chapters are a clear and lucid introduction to the basic rotated disc electrode (RDE) and the multi-faceted problems of mass transport. Well worth a read, if only for the occasional dip into this field. 

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

Considerable progress. However, has been achieved in the recent past due to the development of techniques for the detection of intermediates in low concentrations, such as the rotating ring—disc electrode and in situ spectroelectrochemical techniques such as electron spin resonance (ESR). 

Use of twin electrode cell [103] or rotating ring disc electrode [104] techniques permit the independent separation of the charge and amount... 

The electrosorption valency usually increases as the underpotential decreases to approach the ionic charge (total discharge of the cation) close to the Nernst potential, for instance in the case of lead and thallium upd on silver [114]. However, the co-adsorption of anions may contribute to the observed apparent electrosorption valence, as rotating ring disc electrode (RDE) experiments have shown [113]. 

W.J. Albery, Rotating Ring-Disc Electrodes, Oxford University Press, Oxford, 1971. 

The rotating ring—disc electrode (RRDE) is probably the most well-known and widely used double electrode. It was invented by Frumkin and Nekrasov [26] in 1959. The ring is concentric with the disc with an insulating gap between them. An approximate solution for the steady-state collection efficiency N0 was derived by Ivanov and Levich [27]. An exact analytical solution, making the assumption that radial diffusion can be neglected with respect to radial convection, was obtained by Albery and Bruckenstein [28, 29]. We follow a similar, but simplified, argument below. 

A. Rotating ring—disc electrode. Wall-tube electrode. 

It is more difficult to manufacture these electrodes than the simple disc electrode since the ring must be exactly concentric with the disc. Additionally, in many applications the insulation gap must be thin (0.25 mm or less) as must the ring. For rotating ring—disc electrodes, typical dimensions are a disc radius of 3—4 mm and an outer ring radius of 4—5 mm. For wall-jet ring—disc electrodes, these dimensions can be approximately halved. 

Fig. 7. Typical rotating ring—disc electrode cell. A, rotating ring—disc electrode B, reference electrode with Luggin capillary C, counter electrode D, teflon lid E, porous frit F, thermostatted water jacket.

Ring of rotating ring—disc electrode (reactant produced at disc) PV6U-V2 0.799 C(r, Er) 153 (see also 154)... 

The homogeneous reaction may be of first or second order in the latter case, X is a non-electroactive species. Both these cases have been studied at the rotating ring—disc electrode and the first-order case at a double channel electrode. 

At a double electrode, such as the rotating ring—disc electrode, a potential step at the disc will produce a ring current transient, the form of which is affected only by Faradaic current components at the disc. This fact can be very useful in separating Faradaic and non-Faradaic processes. 

Scheme of a cross section (in the length of the electrode) of rotating-disc electrode (a) and a rotating-ring-disc electrode (b). 

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