Rotating ring-disc electrode technique

The direct four-electron pathway involves no hydrogen peroxide formation in the solution. This fact, however, does not preclude the participation of an adsorbed peroxide intermediate in the course of the reaction. The distinction between both reaction pathways is usually investigated by the rotating ring-disc electrode technique [55]. From the rotation speed and potential dependence of the disc electrode to ring electrode current ratio, it is possible to determine the relative contribution of each reaction pathway to the overall reaction [56]. 

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). 

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... 

In some cases it is of interest to determine products formed at semiconductor electrodes. If redox reactions are involved this can be done by using a rotating ring disc electrode assembly (RRDE), which has proved to be a powerful tool for investigating electrochemical reactions at metal electrodes. The technique and corresponding results as obtained with metal electrodes have been reviewed by Bruckenstein and Miller [6] and by Pleskov et al. [7]. 

The competition between redox reaction and anodic dissolution became very important in the development of stable regenerative solar cells on the basis of semiconductor-liquid junctions. As shown in the previous section, it is determined by the thermodynamic and kinetic properties of the processes involved. Information on the competitions between these reactions cannot be obtained entirely from current-potential curves, because in many cases they do not look very different upon addition of a redox system, especially if the current is controlled by the light intensity. Therefore, a rotating ring disc electrode (RRDE) assembly consisting of a semiconductor disc and a Pt ring is usually applied, i.e. a technique which makes it possible to determine separately the current corresponding to the oxidation of a redox system [62, 63]. 

It is possible to investigate the mechanism using the rotating ring disc electrode (RRDE) technique. This has been described in detail by Albery and Hitchman [18]. Briefly the method is as follows. 

An armoury of powerful electrochemical methods is available. Potential step techniques such as differential pulse DP or square-wave SW voltammetry offer advantages in sensitivity and resolution. Hydrodynamic techniques involving use of rotating disc or rotating ring-disc electrodes allow the chemical steps of the electrode process to be separated from mass transport. Electrochemical transformations may be monitored optically with spectroelectrochemical methods. Even the electrode interface itself is amenable to study by in situ spectroscopic techniques. Detailed descriptions of these methods are to be found in appropriate texts [1-4]. 

Depending on the electrode material, the reduction of oxygen occurs by one or the other reaction pathway. The two reaction pathways may also take place in parallel. The most powerful technique for the quantitative determination of the extent of these reactions was proved to be the rotating ring-disc electrode voltammetry, which allows the detection of hydrogen peroxide on the ring electrode. 

The response recorded in many electrochemical experiments is extensively changed by the chemical reactivity of the product of electron transfer. Indeed, the study of chemical reactions of intermediates either adsorbed on the surface or free in the solution close to the electrode surface has become a major application of several techniques, e.g. cyclic voltammetry, rotating ring disc electrodes, spectroelectrochemistry, and double potential step. 

In a typical experiment with semiconductor-liquid junctions, one of the most important experimental problems is the differentiation between reactions that involve chemical changes at the semiconductor electrode (corrosion with insoluble products) and chemical changes in the electrolyte that might be subject to mass transfer limitations. The technique of Rotating Ring Disc Electrode (RRDE) (17-19) provides an opportunity to differentiate between these two types of reactions under controlled hydrodynamic conditions. In its simplestform, the metallic ring is isolated... 

Hydrodynamic techniques include measurements with stirred solutions or electrodes (rotated electrode and rotated ring-disc electrode) and measurements in flowing streams of a carrier. 

Oxygen electro-reduction and evolution reaction/ cyclic voltammetry, rotating ring disc electrode (RRDE) Ni.Al,, Mn204 KOH solution Two preparation methods are used coprecipitation of metal hydroxides and sol-gel route using metal propionates were used. A Teflon-bound electrode technique was chosen with graphite addition The substitution of Al, by Ni increases the catalytic activity. Maximum activity is experienced by NiMn204 Ponce et al. (2001)... 

An interesting attempt to approach the problem from another direction has been made. Interpretation of the results is however problematical. Electrochemical oxidation [19] of oxalic acid bis (tetramethylammonium) salt in acetonitrile or DMSO using the technique of the rotating ring-disc electrode (see p. 132) and cyclic voltammetry yields carbon dioxide. The technique made it possible to infer potential intermediates in this 2-electron oxidation but no other evidence was obtained. It is assumed that the intermediates were very short lived. The following sequence was proposed ... 

A valuable new technique has been introduced by which both radical ion species can be produced simultaneously in a very small volume - by rotation of the electrodes, the diffusion of the radical ions towards each other is enhanced [8]. This is achieved by the special design seen in Fig. 16 (Rotating Ring Disc-Electrode RRDE). 

A survey of the literature on electropolymerization covering the past few years indicates a growing use of modem electroanalytical techniques to investigate the nature of the electrode processes involved of particular interest are linear and cyclic voltammetry together with the use of the rotating disc and ring-disc electrodes. This development is most likely associated with the introduction of reliable, stable potentiostats incorporating solid-state electronics. 

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