Halide electrolytes

Hasse et al. [366] have used in situ AFM for the detection of silver nucleation at the three-phase junction of the type metal-silver halide-electrolyte solution. At this phase boundary, electrochemical reduction of submicrometer size silver halide crystals immobilized on the surface of gold and platinum electrodes took place. Following nucleation, the reaction advanced until the entire surface of the silver hahde crystals was covered with 20 atomic layers of silver. Then, reduction was terminated. The obtained silver layer could be oxidized and the next layer of silver halide crystals became accessible for further reduction. 

The electrochemical oxidation of 2,5-dimethylthiophene in various electrolytes has been investigated (71JOC3673). In non-halide electrolytes such as ammonium nitrate or sodium acetate, the primary anodic process is the oxidation of the thiophene to the cation-radical (159). Loss of a proton, followed by another oxidation and reaction with solvent methanol, leads to the product (160) (Scheme 31). When the electrolyte is methanolic NaCN, however, nuclear cyanation is observed in addition to side-chain methoxylation. Attack by cyanide ion on the cation-radical (159) can take place at either the 2- or the 3-position, leading to the products (161)-(163) (Scheme 32). 

According to the Lorentz-Lorenz equation (4.3.21) for the molar refraction at optical frequencies, Y is directly proportional to the molecular polarizability p. The Koppel-Palm equation has also been applied to the analysis of solvent effects on thermodynamic quantities related to the solvation of electrolytes [48, 49]. In the case of the systems considered in table 4.11, addition of the parameter X to the linear equation describing the solvent effect improves the quality of the fit to the experimental data, especially in the case of alkali metal halide electrolytes involving larger ions. The parameter Y is not important for these systems but does assist in the interpretation of other thermodynamic quantities which are solvent dependent [48, 49]. Addition of these parameters to the analysis is only possible when the solvent-dependent phenomenon has been studied in a large number of solvents. 

In recent work the gas-tight e.m.f. measuring cell shown in Fig. 36 was replaced by an arrangement which is presented in Fig. 38. The silvar halide electrolyte is molten into a glass tube to prevent gas leakage between the silver anode and the cathode. In addition, the cathode was separated from the outer atmosphere in a gas-tight compartment to prevent evaporation of the halogen species. The free space over the cathode was made small in order to obtain steady-state conditions within reasonable time. 

A detailed study of the electrochemical oxidation of 2,5-dimethylthio-phen in methanol showed that three types of reactions could occur depending upon the electrolytes used. 3-Bromo-2,5-dimethylthiophen was the sole product when ammonium bromide was used. With non-halide electrolytes the formation of 2-methoxymethyl-5-methylthiophen was observed. Finally, with sodium cyanide the products were cis- and trans-l-cyano-S-methoxy-2,5-dimethyldihydrothiophens cisjtrans = 2.3). ... 

Prior to 1970, electrolyte solutions for amperometric sensors were mainly aqueous in nature. Even nowadays, aqueous solutions are still used as the electrolytes for gas sensing, e.g., acid or halide electrolytic solutions are used for acidic gas (hnaya et al. 2005) and for other gas-detection applications (Ho and Hung 2001). As illustrated in the preceding examples, aqueous electrolytes are effective in many electrochemical gas sensors. Examples of commonly used electrolytes in H sensors are presented in Table 15.1. Liquid electrolytes used for designing other electrochemical sensors are listed in Table 15.2. One can observe that most electrochemical gas sensors utihze H SO and NaOH liquid electrolytes and Nation as polymer electrolyte. 

DSC traces on the lead halide electrolytes showed no sample degradation below 300 C in argon. An endotherm resulting from the melting of PEO was observed, but there was no evidence of well-defined melting points of any complexes of the lead salts. Between the melting of PEO at 65°C and the final decomposition of the samples, a broad endotherm was observed which can be associated with an extended process of melting and dissolution of lead halide complex compositions in PEO. 

In this study, the ePC-SAFT EOS as well as the MSA-NRTL model were applied to describe thermodynamic properties of numerous aqueous electrolyte solutions. Whereas only activity coefficients are obtained by the G model, volumetric properties can be calculated with an EOS. Ion-specific parameters were used independent of the electrolyte which the ions are part of. The model parameters possess a physical meaning and show reasonable trends within the ion series. Two ion parameters are needed in ePC-SAFT, whereas six parameters are necessary for applying MSA-NRTL. Next to the standard alkali halide electrolyte systems, both models even capture the non-ideal behaviour of solutions containing acetate or hydroxide anions where a reversed MIAC series is experimentally observed. Until now, thermodynamic properties of more than 120 aqueous systems could be successfully modelled with ePC-SAFT. The MSA-NRTL parameter set has also been applied to a couple of systems (so far 19 solutions). Implementing an ion-pairing reaction in ePC-SAFT,... 

Halo carboxylic adds and esters are either obtained by cleavage of cyclic ketones by electrochemical methods using halide electrolytes [281] or by treatment of the substrates with an omvanadium complex VO(OEt)Cl2 in the presence of a halide donor... 

The major low-frequency bands for the Ag—X stretching vibration on Ag " are r(115 cm"V90 cm"0, Br (162 cm /l43 cm O, and Cr(240 cm . These surface bands are broader than the SERS bands for molecular vibrations which do not involve atoms directly bonded to the surface, and they also show vibrational frequency shifts with electrode potential (21 cm VV for Ag—CP). Also, the band intensities decrease as the Ag electrode potential is moved in the negative direction. Since the point of zero charge (pzc) is around -0.8 V versus SCE on polycrystalline Ag, there is a sizable potential range on Ag which favors specific anion adsorption. In the absence of a molecular species such as pyridine, the SERS surface band for CP disappears at potentials more negative than ca. -0.6 V versus SCE. In addition to the major surface band, other SERS bands are observed in pure aqueous potassium halide electrolyte. For example, in 1 M KCl at -0.2 V versus SCE at Ag, bands are observed " ... 

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Molten halides are liquid electrolytes in many instances, and their decomposition may be canned out in principle to produce the metal and halogen, usually in the gaseous state. The theoretical decomposition voltage, E°, is calculated from the Gibbs energy of formation tlrrough the equation... 

Lower oxidation states are rather sparsely represented for Zr and Hf. Even for Ti they are readily oxidized to +4 but they are undoubtedly well defined and, whatever arguments may be advanced against applying the description to Sc, there is no doubt that Ti is a transition metal . In aqueous solution Ti can be prepared by reduction of Ti, either with Zn and dilute acid or electrolytically, and it exists in dilute acids as the violet, octahedral [Ti(H20)6] + ion (p. 970). Although this is subject to a certain amount of hydrolysis, normal salts such as halides and sulfates can be separated. Zr and are known mainly as the trihalides or their derivatives and have no aqueous chemistry since they reduce water. Table 21.2 (p. 960) gives the oxidation states and stereochemistries found in the complexes of Ti, Zr and Hf along with illustrative examples. (See also pp. 1281-2.)... 

Early in their work on molten salt electrolytes for thermal batteries, the Air Force Academy researchers surveyed the aluminium electroplating literature for electrolyte baths that might be suitable for a battery with an aluminium metal anode and chlorine cathode. They found a 1948 patent describing ionically conductive mixtures of AICI3 and 1-ethylpyridinium halides, mainly bromides [6]. Subsequently, the salt 1-butylpyridinium chloride/AlCl3 (another complicated pseudo-binary)... 

It is so universally applied that it may be found in combination with metal oxide cathodes (e.g., HgO, AgO, NiOOH, Mn02), with catalytically active oxygen electrodes, and with inert cathodes using aqueous halide or ferricyanide solutions as active materials ("zinc-flow" or "redox" batteries). The cell (battery) sizes vary from small button cells for hearing aids or watches up to kilowatt-hour modules for electric vehicles (electrotraction). Primary and storage batteries exist in all categories except that of flow-batteries, where only storage types are found. Acidic, neutral, and alkaline electrolytes are used as well. The (simplified) half-cell reaction for the zinc electrode is the same in all electrolytes ... 

The third aspect, the stability range of solid electrolytes, is of special concern for alkaline-ion conductors since only a few compounds show thermodynamic stability with, e.g., elemental lithium. Designing solid electrolytes by considering thermodynamic stability did lead to very interesting compounds and the discovery of promising new solid electrolytes such as the lithium nitride halides [27]. However, since solid-state reactions may proceed very slowly at low temperature, metasta-... 

The complexes are 1 1 electrolytes in solution. Other such complexes can be made by a similar route or by halide (or carboxylate) exchange. The first monomeric system Ru2C1(02C.C4H4N)4 (thf), where the ruthenium at one end of the lantern is bound to a thf and the other to a chloride, has recently been made [97], [Ru2Cl(02CBut)4(H20)] and [R Cl CPr thf)] are also monomeric [98],... 

Electrochemical oxidation of 4-aryl-substituted thiane in aqueous organic solvents containing various halide salts as electrolytes gave selectively the trans-sulfoxide (lOe). Under acidic conditions a preferential formation of the cis-sulfoxide was attained328. The stereoselective potential of this method for the oxidation of cyclic sulfides139,329 is apparent (equation 123). 

Vitanov and Popov et al.156 660-662 have studied Cd(0001) electrolyti-cally grown in a Teflon capillary in an aqueous surface-inactive electrolyte solution. The E is independent of ce) and v. The capacity dispersion is less than 5%, and the electrode resistance dispersion is less than 3%. The adsorption of halides increases in the order Cl" < Br" < I".661 A comparison with other electrodes shows an increase in adsorption in the sequence Cd(0001) < pc-Cd < Ag( 100) < Ag(l 11). A linear Parsons-Zobel plot with /pz = 1.09 has been found at a = 0. A slight dependence has been found for the Cit a curves on ce, ( 5%) in the entire region of a. Theoretical C, E curves have been calculated according to the GCSG model. 

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