Electrode electrolysis without supporting

The first is that the oxidation mechanism of organics in WEO occurs directly at the electrode surface, without evolving intermediate reactions that form chlorinated compounds, and that can be supported by the fact that free residual chlorine is not detected in the effluent samples for all electrolysis conducted at temperatures higher... 

Iodonium and sulfonium salts undergo irreversible one electron electrochemical or chemical reduction [51,52], Reduction of diaryliodonium salts in water exhibit two to four waves in the polarogram depending upon the concentration of iodonium salt, type of electrode, nature and concentration of the supporting electrolyte, and the maximum suppressor [51,53-56]. Reductive electrolysis of diphenyliodonium salts in water at mercury yields mixtures of diphenylmercury, iodobenzene, and benzene, depending upon the potential used during the electrolysis [51,53-55]. Reduction at platinum or glassy carbon electrodes occurs without appearance of the first wave (see below) [54,56,57]. The mechanism shown in Scheme 1 was proposed for aqueous electrolysis of diphenyliodonium salts [51a] ... 

Tajima and co-workers have developed a novel environmentally friendly electrolytic system using solid-supported bases and protic organic solvents such as methanol [24], This method permits electrolysis without an intentionally added supporting electrolyte. Solid-supported bases are not oxidized at the electrode surface because electron transfer between two solids is, in principle, very difficult [25], Therefore, protons generated by the reaction of a solid-supported base and a protic solvent may serve as carriers of electronic charge. After the electrolysis, the solid-supported base can be easily separated by filtration and can be re-used. 

Electrochemical microflow systems have also attracted significant research interest from the viewpoint of electrolysis without an intentionally added supporting electrolyte, becausethe short distance between the electrodes andthehigh electrode surfaceto reactor volume ratio are advantageous for conductivity and reaction efficiency. 

The electrolysis apparatus for the polymerization is illustrated in Figure 2, which is characterized by a single cell without a partition membrane between the electrodes. In poor solvents of poly(phenyleneoxide) s such as methanol and acetonitrile, the polymer was deposited on the electrode, i.e. passivation of the electrode occured. Dichlo-romethane, nitrobenzene, and hydroquinone dimethyl ether were selected as the solvents because both the polymer and a supporting electrolyte dissolved in them and they were relatively stable under electrolysis conditions. 

Now. this is not usually a problem for producing polypyrrole and related polymers. since a typical film on the electrode weighs only some tens of milligrams, and an electrolyte containing, for example, 0.01 M pyrrole can support its formation without appreciable depletion of the monomer. Constant-current electrolysis is therefore often used for these polymers although it should be noted that the exact properties of the film can vary with preparation conditions, and with this methodology the exact electrode potenhal is not known. 

The potentiostatic electrolysis at a platinum electrode at +1-0 V results in a polymer layer on the electrode surface. After an induction period the electrode surface layer gives an ESR signal with one line of 0.15 mT linewidth (Fig.lO). The linewidth is independent on the radical concentration and the type of the cation in the supporting electrolyte. If the polyaniline film is in contact with aniline in the abscence of an applied potential, the line intensity decrease with time indicating a further reaction of the polymer with the aniline. Under UV-irradiation the free spin can be renewed without reaching its initial intensity (Fig.lOb). 

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