Rotating disc electrode technique

An ECE mechanism examined with the rotating disc electrode technique involved the pyridination of 9,10-diphenylanthracene (DPA) in acetonitrile/0.2 M tetraethylammonium perchlorate (Manning et al., 1969). Initially, 9,10-diphenylanthracene undergoes a reversible one-electron oxidation (84a) to form the radical cation, which reacts with pyridine (Py) to form an adduct (84b) which is in turn oxidized (84c) at a less positive potential than the initial diphenylanthracene molecule. This reaction sequence leads to formation of a dication that may further react with pyridine to form the final... 

Electrochemical data (from cyclic voltammetry and rotating disc electrode techniques, see Box 8.2) for the 2-electron reduction of tF" " to TF in aqueous solution, are consistent with the formation of a transient intermediate Tl(II) species, [Tl-Tl] ", formed near the electrode. 

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). 

Unfortunately, the to-electrode precipitation required for conventional (photo)electrochemical measurements on colloidal semiconductors necessarily perturbs the (assumed) spherical diffusion fields and surface adsorption equilibria that obtain at particles in the free solution state, phenomena which are instrumental in determining the dynamic and static charge transfer characteristics of the semiconductor. Consequently, there is a requirement for photoelectrochemical techniques capable of in situ, non-per-turbative investigations of the mechanistic details and catalytic properties of colloidal semiconductors in solution conditions typical of their intended ultimate application. Two such techniques are photoelectrophoresis and the Optical Rotating Disc Electrode (ORDE, developed by Albery et al.). As mentioned above, the former technique has already been reviewed by this author elsewhere [47]. Thus, the remainder of this review will concentrate on measurements that can be made with the latter... 

Refs. [i] Heyrovskf J, Kuta J (1966) Principles of polarograpy. Academic Press, New York [ii] Bond AM (1980) Modern polarographic methods of analysis. Marcel Dekker, New York [Hi] Kissinger PT, Heineman WR (eds) (1996) Laboratory techniques in analytical chemistry, 2nd edn. Marcel Dekker, New York [v] Pleskov YuV, Filinovskii VY (1976) The rotating disc electrode. Plenum Press, New York [vi] Galus Z (1994) Fundamentals of electrochemical analysis, 2nd edn. Ellis Horwood, New York, Polish Scientific Publ PWN, Warsaw... 

Altering the convective rate of transport, e.g. by changing the rotation frequency of a rotating-disc electrode. Experiments in which the convective rate of transport can be altered are known as hydrodynamic techniques. 

In order to improve the fuel utilization in a Direct Alcohol Fuel Cell (DAFC) it is important to investigate the reaction mechanism and to develop active electrocatalysts able to activate each reaction path. The elncidation of the reaction mechanism, thus, needs to combine pnre electrochemical methods (cyclic voltammetry, rotating disc electrodes, etc.) with other physicochemical methods, such as in situ spectroscopic methods (infrared and UV-VIS" reflectance spectroscopy, or mass spectroscopy such as EQCM, DEMS " ), or radiochemical methods to monitor the adsorbed intermediates and on line chromatographic techniques"" to analyze qnantitatively the reaction products and by-products. 

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]. 

Figure 4-1. Protein film voltammetry as a technique for studying redox enzyme mechanisms. The catalytic current-potential profile provides information on the rate-defining catalytic processes occurring within the enzyme. It is important that interfacial electron transfer is facile and information is not masked by limitations due to tlie transport of substrate and product for this reason the rotating disc electrode is an important tool in these studies.

The quartz crystal nanobalance (QCN) can be combined with practically any electrochemical methods, such as cyclic voltammetry, chronoamperometry, chronocoulometry, potentiostatic, galvanostatic, rotating disc electrode [11], or potentiometric measurements. The EQCN can be further combined with other techniques, e.g., with UV-Vis spectroscopy [12], probe beam deflection (PBD) [13], radiotracer [14], atomic force microscopy (AEM) [15], and scanning electrochemical microscopy (SECM) [16]. The concept and the instrumentation of... 

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