This thesis describes X-ray studies (XANES, EXAFS and XAS) of the structures of electroactive film modified electrodes and their response to potential. To provide insight into the composition, structure and dynamics of the studied systems EXAFS was combined with other techniques: XPS, electrochemical methods and infrared spectroscopy. The electroactive materials studied were Prussian Blue (PB) and its cobalt and nickel derivatives, iridium oxide and polypyrrole/[P(Mo3O10)4]3- composite films. Selected electroactive materials were diverse, since the study was undertaken with the aim of providing the foundations for future experiments in the area of the dynamic in situ EXAFS research. For cobalt hexacyanoferrate films, cobalt was identified as the active redox site, based on clear evidence of changing bond lengths with potential. This suggests it will be an interesting candidate for future dynamic EXAFS study. The behaviour of PB films was found to be complicated to interpret because both redox sites are Fe-based and there exist additional interstitial iron species. In contrast to cobalt hexacyanoferrate, no significant changes could be observed in the Ni XAS data for the nickel derivative with Fe active redox sites. Polypyrrole/[P(Mo3O10)4]3- composite films showed changes in oxidation state of multiple Mo sites in XPS experiments. Nevertheless, they are not a promising material for a dynamic EXAFS because of the interpretational problems, similar to PB films. Iridium oxide films are another promising candidate. They were successfully characterized in in situ EXAFS configuration and changing bond lengths were observed as the potential (and thus Ir oxidation state) was changed. Additionally the thesis includes nanogravimetric observation of ion exchange characteristics of polypyrrole film p-doping in an ionic liquid. It is shown that polypyrrole film redox switching in the deep eutectic ionic liquid (Ethaline) involves a very different pattern of ion transfers to aqueous media. Ionic liquid in the reduced film provides a reservoir of choline cations whose transfer (in the opposite direction to anion doping) partly satisfies electroneutrality. Overall, the sites of redox activity were identified in a range of multi-site redox systems and structural changes were related to the injected charge. This static study is the first step in identifying systems suitable for X-ray synchrotron-based dynamic studies of electroactive film structure.

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A weak electrolyte theory of ionic conduction in solid electrolytes, applicable to a wide range of both crystalline and amorphous ionic conductors, is presented. At low temperatures this theory predicts linear log δT against 1/T plots, the associated prefactors and activation energies varying considerably with composition, at high temperatures, downward curvature of the Arrhenius plots is expected. Anomalously large, composition dependent prefactors and high temperature curvature of Arrhenius plots have been observed in several solid electrolyte systems, including a lithium ion conducting solid solution, LISICON, discussed in this thesis. Their interpretation is not possible with traditional strong electrolyte theories. For the first time it is shown that the AC conductivity of (a) a single crystal solid electrolyte and (b) the intra- and intercrystalline regions of polycrystalline electrolytes, can be accurately analysed in terms of equivalent circuits containing frequency dependent elements of the form Y* = Awn + jBwn. Such elements are related to the co-operative migration of ions which is known to exist in solid electrolytes. This is in contrast to previous approaches which are based on the physically unrealistic model of isolated ion migration. The analysis is applied to single crystal Na β alumina and polycrystalline LISICON. In particular this approach can explain distorted impedance semicircles and broadened, separated spectroscopic M" and Z" peaks. The phase diagram of the Li₄GeO₄-Zn₂GeO₄ system is determined. It contains a lithium ion conducting solid solution, LISICON. It is shown that interstitial Li+ ions, rather than cation vacancies, give rise to high conductivities. The solid electrolyte properties and possible applications of the solid solutions are evaluated. Irreversible decreases in conductivity (ageing effects) occur on annealing, even at room temperature. A variety of minor polymorphic transitions occur on annealing γII solid solutions below ~ 300°C, their relationship to the conductivity has been determined. Contrary to previous results the intra- and intercrystalline conductivities of LISICON solid solutions have the same activation energy. The grain boundary effect in LISICON arises from constriction of the conduction pathways as a result of air gaps at grain boundaries. A model of a polycrystalline electrolyte with such grain boundary behaviour is presented.

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This thesis describes the use of novel electrolytes in media of extremely low relative permittivity. Double layer capacitance, conductivity and voltammetric experiments are presented and attempts are made to elucidate the ionic entities in solution and at the electrode / solution interface. Charge is found to be predominantly carried by triple ions and these have a surprisingly appreciable influence on the double layer structure.;Voltammetric responses are presented in dichloroethane (DCE), anisole (Anis) and cyclohexane (cHex) and it is shown that the reversibility of a process is affected by the length of the tetraalkylammonium chain of the electrolyte. Reversible responses are only observed at very slow sweep rates, and this is a result of the slow electrode desorption kinetics of the electrolyte ions. This has profound consequences for electrochemical studies made in non-aqueous media using quaternary ammonium electrolytes.;Finally, bulk electrolysis experiments are performed in scCO2/water mixtures. It is shown that formate and hydrogen are primarily formed on a platinum surface, whereas oxalate and hydrogen are the major products on lead. This is ascribed to a change in reaction pathway compared to such studies in aqueous media. Supercritical fluids are shown to have significant advantages over liquid solvents for the electrochemical reduction of CO2.

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In this thesis, the synthesis of the organic cyanoacetylenes NCC≡CC(_6)H(_5) and NCC≡CC(_6)H(_4)-4-NMc(_2) and the metal cyanoacetylides Ru(C≡CC≡N)(PPh(_3))(_2)Cp, Ru(C≡CC≡N)(dppe)Cp* and Fe(C≡CC≡N)(dppe)Cp is presented and their coordination chemistry is explored. The structure and electrochemical behaviour of these novel cyano-carbon complexes is investigated and spectro-electrochemical methods are used to investigate the electronic structure of the cyanoacetylide compounds. In addition, in order to gain a greater understanding of the metal/ligand bonding interaction in these systems, the synthesis, structure and electrochemical behaviour of a series of metal nitriles [Ru(N≡CC(_6)H(_4)X)(PPh(_3))(_2)Cp][PF(_6)] (X = NO(_2), NMe(_2), CN) and [M(N≡CC(_6)H(_4)X)L(_2)Cp'][PF(_6)] (M = Ru, L = PPh(_3), Cp' = Cp; M = Ru, L2 = dppe, Cp' = Cp*; M = Fe, L(_2) = dppe, Cp' = Cp) were investigated, as were the complexes [{Ru(PPh(-3))(_2)Cp}(_2){μ-M(CN)(_4)}] (M = Ni, Pd, Pt) and [{Ru(dppe)Cp*}(_2){ μ - M(CN)(_4)}] (M = Ni, Pd , Pt), which feature a group 10 tetracyanometallate as a bridging moiety.

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