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The chemistry of the rechargeable system Li/LiAlCl{sub 4}{center_dot}xSO{sub 2}/C (where x = 2.8 to 6), which has an open-circuit voltage of 3.2 V, was investigated and compared with that of Li/LiGaCl{sub 4}{center_dot}xSO{sub 2}/C, which has an open-circuit voltage of 2.9 V. Cyclic voltammetry, pressure measurements, elemental analysis, and vibrational spectroscopy were used to monitor the cycling behavior and the nature of the discharge products. For the LiAlCl{sub 4} based electrolyte, the discharge products were LiCl and an amorphous complex believed to be LiAl{sup III}Cl(SO{sub 2}){sub 3}. For LiGaCl{sub 4} the solid discharge products were LiCl and a sulfur oxide species of the from S{sub n}O, where n is believed to be in the range of 6 to 10.

Cyclic voltammetry was used to follow the electrochemical properties of LiAlCl4 and LiGaCl4 dissolved in SO2. The behaviour of the two electrolytes was very different indicating different reduction products at a glassy-carbon electrode. Attempts to identify the reduction products were made using in situ Raman spectroscopy of discharging Li LiMCl 4 , SO 2 C cells. Only the LiGaCl4 electrolyte yielded a Raman spectrum. The species present was not lithium dithionite as is produced in non-rechargeable Li SO 2 cells.

The growth of thin hydrous Pt oxide (β-oxide) films by the rapid potential cycling method has been examined in detail, β-oxide formation commences in only a few cycles of potential to an extent which is dependent on the sweep rate used during oxide growth. Its properties, as gauged by the shape and position of the reduction peak, vary significantly after ca. 20–30 cycles of potential and then become constant. The compact α-oxide, which is present along with the β-oxide at all times, can be reduced and reformed in potential sweep experiments, as well as thickened under potentiostatic conditions in the presence of the β-oxide film, exactly as at a bare Pt electrode surface. This confirms that the α-oxide lies beneath a porous β-oxide film. In addition, the kinetics of Fe 2+ oxidation at a β-oxide covered electrode has been investigated. The inhibition of this reaction by the oxide, as well as its other electrochemical properties, support the notion that the β-oxide is a solvent-filled, highly porous, polymer-like material.

The role of the steric factors in the electrode reactions occurring on the interface covered by aliphatic alcohols and acids has been investigated, taking as an example the Cd 2+ /Cd(Hg) system. It has been shown that this process takes place inside the inner layer and the activated complex is created by the replacement of r ≠ water molecules from the surface. From studies carried out at surfactant concentrations corresponding to the plateau of the adsorption isotherm the steric factors r ≠ / r i have been determined ( r i is the number of solvent molecules replaced from the surface by one molecule of adsorbed surfactant). By comparison with investigations performed at lower coverages the magnitude of r ≠ and r i has been estimated. The influence of different factors on the experimental value of these parameters has been discussed.

The passivity of nickel electrodes is investigated at high potentials in absence and presence of the inhibitor 2-pentyl-aminobenzimidazole (PAB). At high potentials, the electrode is covered by a thick film of NiOOH. Various states of the 3-valent oxide film can be distinguished: Without inhibitor (3o), with an outer layer of inhibitor (3out), with an almost constant concentration profile in the total film (3tot) and a concentration gradient of inhibitor in the film caused by diffusion (3diff). Under steady state conditions, the films 3o, 3out and 3tot can be distinguished by the rate of anodic oxygen evolution, and the electrode capacity. Moreover, the reduction and reoxidation capacity of the electrode decreases from 3o to 3out and 3tot. If the film 3o is reduced and reoxidized in presence of PAB, the redox capacity decreases simultaneously with the electrode capacity due to the formation of 3diff. The role of the inhibitor is due to the formation of a thick polymer film on top of the oxide as well as to the formation of a nickel hydroxide/PAB complex. The outer polymer film has a good proton conductivity and presumably a good electron conductivity. It is concluded that the anodic oxygen evolution takes place at the inner boundary between the oxide and PAB film. The inhibition of local corrosion is probably due to formation of the outer polymer film. XPS measurements verify the expected concentration profiles of PAB in the oxide and on top of it. The PAB-film contains a lot of water, and within the passive film PAB causes a substitution of O2− by OH−. Die Passivitat von Nickel-Elektroden in Gegenwart des Inhibitors PAB Die Passivitat von Nickelelektroden wurde in An- und Abwesenheit des Inhibitors 2-Pentyl-Aminobenzimidazol (PAB) untersucht. Bei hohen Potentialen ist die Elektrode mit einem dicken Film von NiOOH bedeckt. Verschiedene Zustande des 3-wertigen Oxidfilmes konnen unterschieden werden: ohne Inhibitor (3o), mit einer auseren Schicht des Inhibitors (3out), mit einem fast konstanten Konzentrationsprofil im gesamten Film (3tot) und mit einem diffusionsbedingten Konzentrationsgradienten des Inhibitors im Film (3diff). Unter stationaren Bedingungen konnen die Filme 3o, 3out und 3tot durch die Geschwindigkeit der anodischen Sauerstoffentwicklung und die Elektrodenkapazitat unterschieden werden. Daruberhinaus nimmt die Reduktions- und Reoxidationskapazitat der Elektrode von 3o uber 3out zu 3tot ab. Wenn der Film 3o in Gegenwart von PAB reduziert und reoxidiert wird, sinkt die Redoxkapazitat ebenso wie die Elektrodenkapazitat wegen einer Bildung von 3diff. Die Wirkungsweise des Inhibitors wird sowohl der Bildung eines dicken Polymerfilmes auf dem Oxid als auch eines Nickelhydroxid/PAB-Komplexes zugeschrieben. Der ausere Polymerfilm hat eine gute Protonenleitfahigkeit und ist vermutlich elektronenleitend. Die anodische Sauerstoffentwicklung findet an der inneren Phasengrenze zwischen Oxid- und PAB-Film statt. Die Inhibition der lokalen Korrosion ist vermutlich der Bildung des auseren Polymerfilmes zuzuschreiben. XPS-Untersuchungen beweisen die angenommenen Konzentrationsprofile von PAB in und auf dem Oxid. Der PAB-Film enthalt viel Wasser; innerhalb des Passivfilmes fuhrt PAB zu einer Substitution von O2− durch OH−.

The adsorption of 1,6-hexanediol at the Hg—aqueous solution interface was investigated. The differential capacity, interfacial tension and the zero charge potential were measured. Analysis of the results were carried out both at constant charge and at constant potential. Good congruence with respect to the potential and noncongruence with respect to the charge was found. It was shown that the hexanediol molecules orientate flat against the surface and the adsorption could be described equally well by the Frumkin or Flory—Huggins isotherms. Adsorption parameters for the hexanediol were compared with the literature data on adsorption of ethanediol and 1,4-butanediol. It was concluded that adsorption of diols does not affect the thickness of the inner layer. Thus, this adsorption is well described by the model of two parallel capacitors.

The mechanism of Cd2+ discharge and cadmium amalgam dissolution in the absence and presence of organic neutral surfactants is compared. The generality of the stepwise mechanism of this reaction occurring on Hg electrode both covered and non-covered by the surfactants is shown. The reliability of the existence of Cd+ as an intermediate in the electrode reaction is discussed.

On gold electrodes, anodic deposition layers of NiOOH (3) were formed, reduced to the oxide Ni(OH) 2 (2) and reoxidized. Experiments in the absence or presence of the inhibitor 2-(5-aminopentyl) benzimidazole (PAB) yielded the pure NiOOH (3o) and Ni(OH) 2 (2o) or various NiOOH/PAB-layers with the inhibitor outside (3out), inside (3in) or in the total film (3tot). The formation and transformation of various layers can be distinguished by measurements of the anodic oxide growth i ( t ), the electrode capacity C ( t ) or the redox charge Q of the oxide. For 3tot, the rate of nucleation and oxide growth is retarded by PAB, but the oxide growth takes place by the same mechanism of progressive nucleation as in case of 3o. The redox process is inhibited and the charge Q decreases in presence of PAB with increasing number of cycles. This indicates a mobility of PAB within the film. Protons and hydroxyl ions can move in the film, too, since beneath the NiOOH/PAB layer, Au 2 O 3 can be formed and reduced with a small overvoltage. All layers will be electronically conducting as can be concluded from the high capacity C > 10 μF/cm 2 . XPS measurements verify the presumed distribution of PAB in the film. They show the formation of thick PAB-films ( d > 3 nm) at the oxide surface for 3out and 3tot as well as for the pure gold surface. The high PAB concentration within the film and the low intensity of the O 1S-peak for 3tot indicates the formation of NiOOH/PAB-complexes.

The formation and properties of NiOOH-layers were investigated by electrochemical measurements in presence and absence of 2-pentylamino-benzimidazole (PAB). Various positions of the inhibitor inside (in), outside (out) and in the total film (tot) can be distinguished, but concentration profiles are not stable, since the inhibitor can diffuse within the film. Therefore, the inhibition of various ion and electron transfer reactions within the film increases with polarization time and number of redox cycles. The NiOOH/PAB-layers are presumably conducting for electrons, and H + or OH − . The inhibition of redox reactions of the NiOOH is explained by a chemical transformation of the NiOOH, the inhibition of the oxide growth by an inhibition of the Ni2+-transfer reaction.