Reference electrodes electrosynthesis

Bubble electrodes — Mercury electrodes constructed in such a way that an electrolyte solution is entering a mercury-filled vessel through one or many small orifices in the bottom (cf. Fig. 1). The solution bubbles grow and will finally ascend in the mercury. The counter and the reference electrode have to be situated in the tubing fed to the orifice. Bubble electrodes have been developed as flow-through detectors for HPLC and FIA [i-iii,vi], as electrodes to generate ESR-active species [iii-iv], for - tensammetry [vii], and for electrosynthesis [v]. The fact that they are mercury based impeded further developments of this electrode type. 

There are lots of systems, especially for electroplating and electrosynthesis, in which electrodes of the first kind can be used, without any liquid junctions (the example is liquid A1 in AlFs-containing melts). More universal systems for melts of various kinds are a chlorine electrode in equimolar NaCl + KCl melt and Ag/Ag+ electrodes with the range of Ag" " concentrations (0.01-10 mM) corresponding to usual solubility values. Reference electrodes of the second kind can hardly be used in melts because of the high solubility of the majority of inorganic solids. 

A one-compartment electrochemical cell used for electrosynthesis and EIS measurements. A large area, Pt gauze counter electrode (2.5 x 3.0 cm, AESAR) and a saturated Ag/AgCl reference electrode were used. TBAHFP(Aldrich) was used without further purification and dried in vacuum at 100 C for ca. 24 h prior to use, 3-Methylthiophene (Aldrich) was distilled in an... 

Miniaturized combinatorial electrosynthesis has been achieved by using a computer-controlled instrument equipped with a well-containing microtiter plates (Fig. 3) [7]. An electrode btmdle consisting of a PTFE holder, a working electrode, a CV microdisk, a reference electrode, and a counter electrode is moved from well to well automatically. Libraries of iminoquinol ethers and triazolopyridinium ions are generated by under controlled potential conditions. Progress of the electrolyses can be monitored by microelectrode steady-state voltammetry. 

Fig. 2,34 The electrochemical pump cell, (a) A monopolar cell for production of metal powders. After Jansson, R. E. W. and Ashworth, G. A., (1977) J. Appl. Electrochem., 7, 309). (b) Bipolar rotor cell for electrosynthesis. After Jansson, R. E. W., Marshall, R. J. and Rizzo, J. E. J., (1978) J. Appl Electrochem., 8, 281). (c) An improved version of (b) which incorporates facilities for adjustment of the rotor position, a reference electrode probe and enhanced mass transport. The bipolar rotor has a diameter of 10 cm and rotates at 2800 rev min" ...

Electrosynthesis of the polythiopene was realized on an indium-tin-oxide (ITO) electrode (glass blade covered with an indium-doped tin-oxide film). Before conducting the experiment, each electrode was cleaned by ultrasonication for 10 min in different solvents (acetone, dichloromethane, ether). Electrochemical experiments were performed in a three-compartment cell. The working electrode was the ITO electrode, the counter electrode was a Pt wke, and the reference electrode was an aqueous-saturated calomel electrode (E°/SCE = E°/NHE — 0.2412 V) with a salt bridge containing the supporting electrode. The SCE electrode was checked against the ferrocene/ferricinium couple (E = -1-0.405 V/SCE) before and after each experiment. 

In liquid ECAFM applications, the AFM tip and sample surface comprise the working and counter electrodes of an electrochemical cell. Additionally, a reference electrode can be incorporated into the liquid cell allowing the instrument to effectively perform as a three-electrode electrochemical cell. The technique has expanded into several applications where electrosynthesis and electrodeposition reactions can take place simultaneously with imaging [54]. Electrical connections can be made between the tip and enzymes on a surface to measure electron transfer and conductivity [44,52,55]. In addition, the tip can be functionalized with electroactive biomolecules to perform redox reactions and measure the amperometric and voltammetric response in situ [56]. 

Figure 3.3 Sonoelectrochemical cell used for electrosynthesis and voltammetric studies. 1, Sonic horn 2, transducer 3, to control unit of sonic horn 4, graphite counter electrode 5, argon inlet for degassing 6, Pyrex reservoir 7, platinum-disk macro- or microelectrode 8, copper cooling coil connected to the thermostatted water bath 9, titanium tip 10, platinum resistance thermocouple 11, SCE reference. (From Ref. 557, reproduced with permission.)...

Electrocatalysis is a heterogeneous process that involves the adsorption and the chemisorption of reactants or intermediates at the interface. These phenomena are encountered, for example, in fuel cells (FCs) or in organic electrosynthesis. The electrocatalytic activity of a given electrode for a certain reaction may be characterized by the current density at a chosen potential, which is proportional to the specific activity, when referred to the effective active surface. As shown in Figure 21.2, the role of a heterogeneous catalyst is to adsorb the electro-reactive species (reactant and intermediate) and transform it to another compound that can more readily undergo the desired... 

This chapter comprises a brief introduction to electrosynthesis, with reference to electroanalysis, a domain where, with physical electrochemistry, there have been striking developments from combination with ultrasound. Readers interested in the application of ultrasound at some other point in the electrochemical procedure, for example to clean electrodes prior to making up the cell, or in pretreatment of electrolytes, are directed towards a more extensive review of sono-electrochemistry. ... 

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