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Interfacial phenomena electrochemical

Introducing reactive gases to the plasma phase may even lead to the formation of metal or semiconductor compounds, extending the experimental possibilities even further. From the physicochemical point of view, plasma electrochemical deposition is a highly interesting interfacial phenomenon, linking plasma chemistry and... [Pg.282]

Characteristic potential — means the potential of a certain singular point in electrochemical response that is characteristic of the particular charge-transfer process (- charge-transfer kinetics) or interfacial phenomenon. Any characteristic p. is related to given experimental conditions (such as the temperature, the nature of the solvent, and supporting -> electrolyte and its concentration). The nature and type of characteristic p. depends on the technique that is employed. Typical characteristic potentials are the -> half-wave potential in -> po-larography and the -> peak potentials in -> voltammetry, similar maximum/minimum of inflection points can be listed for other techniques. [Pg.530]

Electrochemical redox studies of electroactive species solubilized in the water core of reverse microemulsions of water, toluene, cosurfactant, and AOT [28,29] have illustrated a percolation phenomenon in faradaic electron transfer. This phenomenon was observed when the cosurfactant used was acrylamide or other primary amide [28,30]. The oxidation or reduction chemistry appeared to switch on when cosurfactant chemical potential was raised above a certain threshold value. This switching phenomenon was later confirmed to coincide with percolation in electrical conductivity [31], as suggested by earlier work from the group of Francoise Candau [32]. The explanations for this amide-cosurfactant-induced percolation center around increases in interfacial flexibility [32] and increased disorder in surfactant chain packing [33]. These increases in flexibility and disorder appear to lead to increased interdroplet attraction, coalescence, and cluster formation. [Pg.252]

One may then conclude that, the gel-type electrolytes, and the PAN-based ones in particular, have electrochemical properties that in principle make them suitable for application in versatile, high-energy lithium batteries. In practice, their use may be limited by the reactivity towards the lithium electrodes induced by the high content of the liquid component. Indeed, severe passivation phenomenon occurs when the lithium metal electrode is kept in contact with the gel electrolytes [60, 69]. This confirms the general rule that if from one side the wet-like configuration is essential to confer high conductivity to a given polymer electrolyte, from the other it unavoidably affects its interfacial stability with the lithium metal electrode. [Pg.230]

The interfacial behavior of alkyl xanthates (a typical member of the O-alkyldithio-carbonate collector family) (Fig. 7.22) is of great interest in flotation studies, where these reagents have been used for the selective hydrophobization of sulfides since 1925. A variety of hypotheses have been put forward to explain this phenomenon (see Refs. [365, 369, 464-466] for review) that can be classified as either chemical or electrochemical. The former category includes adsorption [467-469], coordination [470], and replacement of surface oxidation products [471-473] or lattice ions [474, 475]. However, this hypothesis neglects... [Pg.561]

Parallel events in the field of in situ IR spectroscopy (for a review of sulfate IR studies, see Ref. 26) resulted in a coupled shift to molecular level bi-sulfate anion was recognized in sulfate adlayer even in solutions with predominating sulfate. It was com-pletey new situation, when chemical equilibrium is affected by adsoibate-surface interactioa In usual terms of solution equilibria, the effect corresponds to increase of pKa from its bulk value (ca. 2) to 3.3-4.7 (pKa is potential-dependent). To agree this situation with bulk thermodynamics, one should simply use electrochemical potential instead of chemical. The phenomena of adsorption-induced protonation is relative to UPD, when adsoibate-surface interaction shifts redox equihbria. In more molecular terms, the species determined as bi-sidfate ions are probably interfacial ion pairs, i.e., the phenomenon can be considered as coadsorptioa This situation is screened in purely thermodynamic analysis, as excess surface protonation is hidden in Gibbs adsorptions of sulfate and H. However it becomes important for any further model consideration, as it can affect lateral interactions and the order in the adlayer. The excess adsorption-induced protonation of various anions is a very attractive field. In particular it is the only chance to explain why multicharged oxoanions can form complete mono-layers on platinum. [Pg.134]

A further current increase in region 4 (Fig. 2) cannot be explained by any interfacial electrochemical reaction. An explanation based on the electrochemical electron transfer phenomenon requires the presence of species with energy states higher than those of the solvent. None are available. [Pg.266]

This changes, however, if electrical potential differences are relevant. In such cases, it is necessary to include the individual ions — and, hence, their electrochemical potentials — in the calculation [151-153]. If this electrochemical potential is split into chemical and electrical potential terms (Section 4.3.6), it can be seen that changes in the interfacial tension (d7) are not only caused by changes in chemical potential (d/i, cf. Eq. 5.71)) but also by changes in electrical potential (d ). The dependence of the interfacial tension (morphology ) on the electrical potential is a phenomenon known as electrocapillarity. It can be demonstrated in a strmghtforward way [148] that the interfacial tension of the contact of an ideally polarizable electrode with an electrolyte depends on the potential U (the counterelectrode is assumed to be ideally nonpolarizable ) according to the Lippmann relationship ... [Pg.148]


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