Advances in the application of bipolar electrodes (BPEs) for screening of electrocatalysts, localized activation of a single conductive electrode, the optical tracking of single particles interacting with an active electrode, and the introduction of microwires in paper-based analytical devices are described. In an original proof of concept study arrays of BPEs were used to determine the relative activity of model nanoparticle systems for the oxygen reduction reaction (ORR) by a simple optical readout: the electrodissolution of Ag microbands. The number of bands that dissolved during the screening procedure determined the relative activity of the materials. These screening results for model nanoparticle systems were related to traditional electrochemical experiments and showed a strong correlation. Building on that initial study, the BPE platform for screening ORR electrocatalyst candidates was improved so that more materials could be evaluated simultaneously by increasing the density of electrodes in the array, controlled compositional variations were prepared with the implementation of piezodispensing, and a different reporter, Cr, replaced Ag at the BPE anodes which reduced the risk of contamination and improved reliability of screening experiments. Further studies into the versatility of the screening platform have been carried out using non-noble metal systems for the hydrogen evolution reaction (HER), which has a long history of interest for electrochemists. A single conductive electrode material can be made to act as an array of electrodes by confining it at the intersection of two orthogonal microfluidic channels. By manipulating the direction and magnitude of the electric field in the device, faradaic reactions can be selectively localized on the BPE. An approach for optically tracking individual, insulating microparticles interacting with an active UME has been achieved. This approach brings new insight and understanding of single particle electrochemical studies. Finally, a method for incorporating microwires and mesh electrodes into paper-based electroanalytical devices is reported. This has many advantages over traditional screen-printed carbon electrodes that are traditionally used in paper-based devices. / text

Electrochemical analysis using mercury electrodes has been a prominent methodology since the beginning of voltammetry, however, due to its toxic nature their use is being slowly phased out in favour of environmentally friendlier alternatives. In this thesis, carbon electrodes feature heavily as a means to provide a cheaper and non-toxic approach to voltammmetric sensing. Pulse techniques have been used for the sensitive detection of commonly studied analytes, including antimony and iron. A simple fabrication of a vibrating electrode is presented by modifying a commercially available vibrating toothbrush with platinum foil as a means to enhance mass transport for electroanalytical work. Finally, pH determination at carbon electrodes is investigated. Carbon electrodes have been proposed as a simple sensor for pH determination by exploiting the pH sensitive nature of surface quinone groups intrinsic within carbon edge-plane like sites. Using this approach, both EPPG and GC electrodes are suggested as new materials for pH determination and can be used in aqueous solutions over the pH range 1.0 to 13.0, as a cheap and simple alternative to the classic glass electrode.

O estudo de polímeros condutores desperta um enorme interesse científico e tecnológico devido às diversas aplicações possíveis para esses materiais, como o desenvolvimento de dispositivos eletro-eletrônicos e sensores. Através de processos de dopagem esses polímeros tornam-se eletroativos, possibilitando por meio de técnicas eletroquímicas a determinação de diversas substâncias. Na agropecuária, a utilização intensiva e crescente de produtos químicos como pesticidas e fertilizantes, tem provocado diversas contaminações e agressões, despertando interesse na utilização de sensores para o monitoramento dessas substâncias em tempo real. Os eletrodos modificados com polímeros condutores têm-se apresentado como uma alternativa devido a algumas peculiaridades como alta estabilidade física e química e excelentes possibilidades analíticas devido à versatilidade da polimerização eletroquímica. Este trabalho teve como objetivo o desenvolvimento de novos materiais de eletrodos modificados com polímeros condutores para a determinação eletroanalítica de pesticidas. Os pesticidas estudados foram os herbicidas 2,4-D, bentazon, glifosato, paraquat e o inseticida paration metílico. Foram realizadas medidas voltamétricas e de impedância com eletrodos de carbono vítreo, pasta de carbono e eletrodos modificados com polianilina e polipirrol, visando a obtenção de sensores para a detecção destes pesticidas. Estudos de interação dos pesticidas com os polímeros foram realizados utilizando-se a técnica de espectrofotometria de UV-visível para a determinação da concentração dos pesticidas em estudos cinéticos. Também utilizou-se a espectroscopia de impedância eletroquímica para auxiliar no entendimento das interações entre os pesticidas e os polímeros condutores. Adicionalmente foi aplicada uma metodologia de análise de fluxo descontínuo (BIA), utilizada com sucesso na determinação de metais, para a determinação de pesticidas. Os resultados mostraram uma seletividade nas interações entre os polímeros condutores e os pesticidas. Por meio da resposta voltamétrica dos polímeros condutores, os eletrodos de pasta modificados com polianilina e polipirrol mostraram-se hábeis na detecção dos pesticidas não eletroativos como o 2,4-D, o bentazon e o glifosato, bem como na determinação do paraquat. Estes resultados atribuem aos eletrodos modificados desenvolvidos neste trabalho a característica de sensores de diagnóstico da presença destes pesticidas em solução. A metodologia de BIA na determinação de pesticidas, apresentou inúmeras vantagens do ponto de vista analítico, como a não renovação da superfície de eletrodo, micro-volumes de injeção de amostra, dezenas de análise sem troca do eletrólito suporte, tempos de análise inferiores a um segundo bem como a possibilidade de utilização de dispositivo portátil para análises em campo. / Studies of conducting polymers have great technological and scientific interest due to many possibilities of applications like the development of electronic devices and sensors. By means of a doping process these polymers became electroactives, allowing the determination of substances that specifically interact with the polymers. In agriculture the intensive and constant use of chemical substances as pesticides and fertilizers are causing several environmental contamination and the development of sensors for real time analysis has been a research field of intense interest. Electrodes modified with conducting polymers have several interesting characteristics as their high physical and chemical stability and excellent analytical possibilities, due to the versatility of the electrochemical polymerization. The objective of the present work was the development of electrode materials modified with conducting polymers for the electroanalytical determination of pesticides. The pesticides studied were the herbicide 2,4-D, bentazon, gliphosate and paraquat and the insecticide methylparathion. Voltammetric measurements were performed on glassy carbon and carbon paste electrodes modified with polianiline and polipirrol to obtain a procedure for the pesticides measurement. Studies of interaction between the pesticides and the polymers were performed using UV-visible spectrophotometry for pesticide concentration determination kinetic sorption experiments and the electrochemical impedance technique was also used to evaluate such sorption processes. Batch Injection Analysis (BIA), a technique successfully used for the analysis of metals, was also tested for the determination of the herbicide paraquat. Results obtained from the kinetic studies and the voltammetric and impedance experiments showed some selectivity for the interaction of the pesticide with the two polymers. By means of the voltammetric response of the polymers, the carbon paste electrode modified with polianiline showed to be very suitable for the detection of the herbicide 2,4-D, bentazon and gliphosate, but not for paraquat and methilparathion. On the other hand the carbon paste electrode modified with polipirrol detect only the gliphosate and paraquat. The results shows that the detection of the paraquat and the gliphosate by the polipirrol are not influenced by protonation, whereas the detection of the 2,4-D, bentazon and gliphosate by the polianiline are due to sorption and consequent doping of the polymer by the pesticides, which have acidic behavior. The BIA technique used for the detection of the pesticide paraquat, showed a good sensitivity and could be used in the future for the analysis of such substances with many advantages when compared with conventional electroanalytical procedures.

3D printing has revolutionised traditional manufacturing methods, opening up and distributing design and production of low cost, custom objects to virtually anyone. Tailoring of print material and part geometry allows for the benefits of this technology to reach multiple engineering and scientific fields, given appropriate design. A multidisciplinary approach concerning development of new print materials and methods was undertaken with the aim of further expansion and application of 3D printing towards electrochemical applications. Specific requirements of materials used in this domain, such as conductivity and chemical stability, led to development of functional printable carbon composites, compatible with consumer grade 3D printers. This allows facile production of cheap, reusable, disposable, electrodes for analytical applications, demonstrating heavy metal detection in aqueous media and allowing further tailoring to specific applications to be easily implemented. A new method for printing of cellulose solutions was developed, with post processing of printed parts resulting in biocompatible, porous, conductive structures. When used as electrodes in microbial fuel cells, improved power and current output over traditionally used carbon cloth electrodes was achieved. Other developments resulting from this work applicable to other fields include a novel trajectory generation method based on exponential functions which can be applied to practically any robotic system, as well as improvements to the production process of metal alloy filaments for 3D printing of metallic components.

O estudo de polímeros condutores desperta um enorme interesse científico e tecnológico devido às diversas aplicações possíveis para esses materiais, como o desenvolvimento de dispositivos eletro-eletrônicos e sensores. Através de processos de dopagem esses polímeros tornam-se eletroativos, possibilitando por meio de técnicas eletroquímicas a determinação de diversas substâncias. Na agropecuária, a utilização intensiva e crescente de produtos químicos como pesticidas e fertilizantes, tem provocado diversas contaminações e agressões, despertando interesse na utilização de sensores para o monitoramento dessas substâncias em tempo real. Os eletrodos modificados com polímeros condutores têm-se apresentado como uma alternativa devido a algumas peculiaridades como alta estabilidade física e química e excelentes possibilidades analíticas devido à versatilidade da polimerização eletroquímica. Este trabalho teve como objetivo o desenvolvimento de novos materiais de eletrodos modificados com polímeros condutores para a determinação eletroanalítica de pesticidas. Os pesticidas estudados foram os herbicidas 2,4-D, bentazon, glifosato, paraquat e o inseticida paration metílico. Foram realizadas medidas voltamétricas e de impedância com eletrodos de carbono vítreo, pasta de carbono e eletrodos modificados com polianilina e polipirrol, visando a obtenção de sensores para a detecção destes pesticidas. Estudos de interação dos pesticidas com os polímeros foram realizados utilizando-se a técnica de espectrofotometria de UV-visível para a determinação da concentração dos pesticidas em estudos cinéticos. Também utilizou-se a espectroscopia de impedância eletroquímica para auxiliar no entendimento das interações entre os pesticidas e os polímeros condutores. Adicionalmente foi aplicada uma metodologia de análise de fluxo descontínuo (BIA), utilizada com sucesso na determinação de metais, para a determinação de pesticidas. Os resultados mostraram uma seletividade nas interações entre os polímeros condutores e os pesticidas. Por meio da resposta voltamétrica dos polímeros condutores, os eletrodos de pasta modificados com polianilina e polipirrol mostraram-se hábeis na detecção dos pesticidas não eletroativos como o 2,4-D, o bentazon e o glifosato, bem como na determinação do paraquat. Estes resultados atribuem aos eletrodos modificados desenvolvidos neste trabalho a característica de sensores de diagnóstico da presença destes pesticidas em solução. A metodologia de BIA na determinação de pesticidas, apresentou inúmeras vantagens do ponto de vista analítico, como a não renovação da superfície de eletrodo, micro-volumes de injeção de amostra, dezenas de análise sem troca do eletrólito suporte, tempos de análise inferiores a um segundo bem como a possibilidade de utilização de dispositivo portátil para análises em campo. / Studies of conducting polymers have great technological and scientific interest due to many possibilities of applications like the development of electronic devices and sensors. By means of a doping process these polymers became electroactives, allowing the determination of substances that specifically interact with the polymers. In agriculture the intensive and constant use of chemical substances as pesticides and fertilizers are causing several environmental contamination and the development of sensors for real time analysis has been a research field of intense interest. Electrodes modified with conducting polymers have several interesting characteristics as their high physical and chemical stability and excellent analytical possibilities, due to the versatility of the electrochemical polymerization. The objective of the present work was the development of electrode materials modified with conducting polymers for the electroanalytical determination of pesticides. The pesticides studied were the herbicide 2,4-D, bentazon, gliphosate and paraquat and the insecticide methylparathion. Voltammetric measurements were performed on glassy carbon and carbon paste electrodes modified with polianiline and polipirrol to obtain a procedure for the pesticides measurement. Studies of interaction between the pesticides and the polymers were performed using UV-visible spectrophotometry for pesticide concentration determination kinetic sorption experiments and the electrochemical impedance technique was also used to evaluate such sorption processes. Batch Injection Analysis (BIA), a technique successfully used for the analysis of metals, was also tested for the determination of the herbicide paraquat. Results obtained from the kinetic studies and the voltammetric and impedance experiments showed some selectivity for the interaction of the pesticide with the two polymers. By means of the voltammetric response of the polymers, the carbon paste electrode modified with polianiline showed to be very suitable for the detection of the herbicide 2,4-D, bentazon and gliphosate, but not for paraquat and methilparathion. On the other hand the carbon paste electrode modified with polipirrol detect only the gliphosate and paraquat. The results shows that the detection of the paraquat and the gliphosate by the polipirrol are not influenced by protonation, whereas the detection of the 2,4-D, bentazon and gliphosate by the polianiline are due to sorption and consequent doping of the polymer by the pesticides, which have acidic behavior. The BIA technique used for the detection of the pesticide paraquat, showed a good sensitivity and could be used in the future for the analysis of such substances with many advantages when compared with conventional electroanalytical procedures.

Dans ce travail nous étudions l’élaboration, la caractérisation et les applications de différents matériaux poreux. L’étude est organisée en trois parties majeures: la synthèse de zéolithes micro/mesoporeux et leur application potentielle dans l’industrie pétrochimique, l’étude théorique de mécanismes réactionnels sur des zeolites microporeux, et le design de métaux mesoporeux avec une chiralité intrinsèque de leur surface interne. Ces matériaux poreux montrent des propriétés excellentes, notamment pour des applications potentielles en catalyse et comme interfaces chirales. / In the present work, the elaboration, characterisation and applications of differentporous materials have been studied. Porous materials are divided into three categoriesdepending on the porous cavity size, namely microporous materials (pore diameter < 2nm), mesoporous materials (2 nm < pore diameter < 50 nm) and macroporous materials(pore diameter > 50 nm). The thesis work is organized in three major parts: the synthesisof hierarchical micro/mesoporous zeolites and their potential application for thepetrochemical industry, the theoretical study of reaction mechanisms on microporouszeolite and the design of mesoporous metals with intrinsic chirality at their inner surface.The hierarchical micro/mesoporous zeolite, composed of microporous andmesoporous features, has been prepared using carbon-silica (C/SiO2) composites derivedfrom a pyrolysis of hydrocarbon gas on silica gel. Our findings demonstrate that not onlythe presence of a high surface area and porosity, but also an improved efficiency of thesematerials for many petrochemical processes such as n-butene isomerization, nhexadecanecatalytic cracking and hydrocracking. The novel synthetic method is expectedto be generalized for other types of zeolites, and is considered to be a promising methodfor creating hierarchical micro/mesoporous zeolites for potential catalytic applications,especially in the petrochemical industry.In addition to the study of practical catalytic aspects, a theoretical approach hasbeen used to investigate potential reaction mechanisms such as the selective isomerizationof 1-butene into isobutene. More specifically, the monomolecular skeletal isomerizationof 1-butene into isobutene on H-FER zeolite was theoretically studied by using theONIOM approach. This process was found to involve the transformation of adsorbed 1-butene through 2-butoxide, isobutoxide, and tert-butyl cation intermediates. The ratedeterminingstep is the conversion of isobutoxide into isobutene, in which the reactionhas to proceed through the primary isobutyl cation transition state. The shape selectivitydue to the “nano-confinement” effect of the zeolite framework strongly affects theadsorption, the stability of alkoxide species and carbenium ion, as well as the skeletalisomerization mechanism of 1-butene.Moreover, the microporous and mesoporous zeolite, the generation of chiralmesoporous metal and its enantioselective recognition properties have been studied.Molecular imprinting (MI) is a major approach for generating materials withenantioselective properties. In this work, a chiral imprinted mesoporous platinum hasbeen obtained by the electrochemical reduction of platinum salts in the simultaneouspresence of a lyotropic liquid crystal phase and chiral template molecules. The resultingmaterials exhibit not only a dramatic increase in active surface area due to theirmesoporosity, but also a significant discrimination between two enantiomers of a chiralprobe, confirmed by both electrochemical and enantioselective adsorption experiments.Most importantly the porous platinum retains its chiral character even after removal of thechiral template molecule. Our findings could lead to the development of new materials,which are of potential interest for applications in areas such as chiral synthesis, sensors,separation, purification and drug development.

CVD diamond possesses certain attractive electrochemical properties inter alia low background current, broad potential window, chemical inertness and resistance to electrocorrosion and fouling. As a consequence its use in various areas of electrochemistry, such as electrochemical sensing, wastewater treatment and electrocatalysis is being explored. Unfortunately, alongside these attractive features, bare CVD diamond electrodes, in common with all other electrode materials, cannot be effectively applied in all electrochemical systems of interest, since for example it may not display useful electrochemical activity for the redox process of interest. In these circumstances it may be possible to modify the electrode by addition of other chemical species to the surface, to introduce the relevant activity. One of the main aims of this thesis was therefore to investigate the properties of certain chemical modifications to the diamond electrode surface. A second aim was also to explore for the first time the use of a practically useful form of single crystal diamond, so-called heteroepitaxial diamond, in electrochemistry. The diamond electrodes used were boron-doped material grown by chemical vapour deposition. A range of electrochemical methods, including especially cyclic voltammetry, square-wave voltammetry, impedance spectroscopy and scanning electrochemical microscopy, were used to characterise electrode properties. Other physical methods employed included scanning electron and atomic force microscopy, X-ray photoelectron spectroscopy and dynamic light scattering techniques. The electrochemical properties of heteroepitaxial single crystal diamond were explored and compared to polycrystalline counterparts. The single crystal diamond electrode was found to show superior properties in terms of wide potential window, low background current and homogeneous activity across the electrode surface, coupled with resistance to fouling. Heterogenous electron transfer rate constants were found to be lower than normally found on polycrystalline diamond; this was attributed to reduced density of states and absence of functional groups. An electrochemical route to the preparation of diamond electrodes, modified by PrOx@Pt core-shell particles was demonstrated. It was observed that these electrode modifiers were far less susceptible to poisoning than bare Pt nanoparticles when used in the electrochemical oxidation of methanol. It was also shown that diamond electrodes with these core-shell particles deposited on them, displayed useful activity for the electrochemical oxidation of nitric oxide. The presence of the PrOx layer was shown to impart useful selectivity against the oxidation of interfering compounds such as nitrite and ascorbic acid, without the loss of sensitivity which normally occurs if nafion coatings are used instead. Basic electrochemical characterisation of the PrOx coating showed that the layer was chemically active and did not serve as a simple blocking layer when deposited on the electrode. The activity of Pt modified diamond electrodes for the oxidation of nitrite species was also studied. It was also shown that the addition of carbon black to a diamond electrode resulted in much enhanced electrochemical properties in the detection of riboflavin.

This thesis is concerned with the deposition of nanoparticle films onto boron-doped diamond and tin-doped indium oxide (lTO) surfaces and the characterisation of the films using electron microscopy, powder diffraction methods and quartz crystal microbalance (QCM) data. The redox behaviour of the porous films was examined using cyclic voltammetry in various media to investigate potential electroanalytical applications. TiOz (anatase) mono-layer films were immobilised onto an inert boron-doped diamond substrate. Cyclic voltammetry experiments allowed two distinct steps in the reduction - protonation processes to be identified that are consistent with the formation of Ti(III) surface sites accompanied by the adsorption of protons. Preliminary data for electron transfer processes at the reduced TiOz surface such as the dihydrogen evolution process and the 2 electron - 2 proton reduction of maleic acid to succinic acid are discussed. Novel multi-layer TiOz films were deposited with a variety of organic binder molecules onto ITO substrates. The redox reactivity of Cuz+ with 1,4,7,10- tetraazacyclododecane- 1,4,7, IO-tetrayl- tetrakis (methyl-phosphonic acid) in solution and immobilised on an electrode surface are investigated. The influences of film thickness, scan rate, and pH on the electrochemistry of immobilised pyrroloquinoline quinone was investigated with two possible electron transport processes observed. The thickness of TiOz phytate films was found to change the shape of the resulting cyclic voltammograms dramatically. Computer simulation and impedance spectroscopy allowed insights into the diffusion of electrons to be obtained. 1, 1 ~Ferrocenedimethanol was employed as an adsorbing redox system to study the voltammetric characteristics of carboxymethyl-y-cyclodextrin films and evidence for two distinct binding sites is considered. The apparent transport coefficients for dopamine and Ru(NHJ)6J+ are estimated for TiOz Nafion® films. The electrochemical processes in biphasic electrode systems for the oxidation of water-insoluble N,N-didodecyl-N;N~diethyl-benzene-diamine (DDPD) pure and dissolved in di-(2-ethyl-hexyl)phosphate (HDOP) immersed in aqueous electrolyte media are described. Transfer of the anion from the aqueous electrolyte phase into the organic phase accompanies the oxidation of pure DDPD. In the presence of HOOP, oxidation is accompanied by proton exchange. The electrochemically driven proton exchange process occurs over a wide pH range. Organic microdroplet deposits of OOPD in HDOP at basal plane pyrolytic graphite electrodes are studied using voltammetric techniques and compared to the behaviour of organic microphase deposits in mesoporous Ti02 thin films. Two types of Ti02 thin film electrodes were investigated, (i) a 300-400 nm film on ITa and (ii) a 300-400 nm film on ITa sputter-coated with a 20 nm porous gold layer. The latter biphasic design is superior. Titanium carbide (TiC) nanoparticies were deposited onto ITa electrodes. Partial anodic oxidation and formation of novel core-shell TiC-Ti02 nanoparticies was observed at applied potentials positive of 0.3 V vs. SCE. Significant thermal oxidation of TiC nanoparticies by heating in air occurs at 250 °c leading to coreshell TiC-Ti02 nanoparticies, then Ti02 (anatase) at ca. 350 °c, and Ti02 (rutile) at temperatures higher than 750 °c. The electrocatalytic properties of the core-shell TiC-Ti02 nanoparticulate films were surveyed for the oxidation of hydroquinone, ascorbic acid, dopamine and nitric oxide (NO) in aqueous buffer media. Mono- and multi-layer Ce02 deposits on ITa are shown to be electrochemically active. A reduction assigned to a Ce(IV/III) process has been observed and followup chemistry in the presence of phosphate discovered. The interfacial formation of CeP04 has been proven and effects of the deposit type, pH and phosphate concentration on the process analysed. The electrochemistry of multi-layer Ce02 nanoparticulate films in organic solvent is shown to be more stable.

The experimental work discussed in this thesis explores the effects of metal modification on the electroanalytical ability of boron doped diamond electrodes. Boron doped diamond (BDD) electrodes have found increased application to electroanalysis in the past two decades, yet relatively little of the literature is focused on metal, nano and microparticle modification of the substrate. In this thesis three metals have been used to modify the BDD electrode; bismuth, antimony and nickel. Bismuth and antimony nanoparticle modified BDD electrodes were directly compared to unmodified BDD and a bulk bismuth electrodes in the determination of trace levels of cadmium and lead using anodic stripping voltammetry. In both instances, the modified electrode allowed for the simultaneous determination of each analyte that was otherwise unattainable at the unmodified BDD electrode. The nickel modified BDD (Ni-BDD) electrode was used in the determination of organic analytes, namely glucose, methanol, ethanol and glycerol. The nickel nano and microparticle electrodes gave the characteristic Ni(OH)₂/NiOOH redox couple in alkali pH, the oxidised form of which (NiOOH) catalysed the oxidation of the organic analytes. The chapter on glucose sensing with the Ni-BDD electrode is preceded by an extensive literature review on the advances of non-enzymatic glucose sensing, and the application of catalytic metals and nanomaterials in this field. Throughout the course of this DPhil, there has been a collaborative project between Asylum Research and myself within the Compton group to develop a commercial electrochemical atomic force microscope (EC-AFM) cell. The aim was to produce an adaptable EC-AFM cell capable of dynamic electrochemical experiments whilst simultaneously or instantaneously acquiring an AFM image of the modified surface, in-situ. This project was successful, and the EC-AFM cell has contributed to a number of chapters in this thesis, and has now been commercialised.

This thesis concerns several advances in electroanalytical chemistry which are separated into four parts: the electrochemical investigation of diffusional behaviour, the mechanistic and kinetic study of electrochemistry with room temperature ionic liquids (RTILs), the study of weakly-supported electrochemistry and a comparison of the Butler-Volmer and Marcus-Hush kinetic theories of electron transfer. A study of the diffusional behaviour of electroactive species is essential for further studies, especially in the case when electrochemistry is complicated through ion-pairing interactions between the electroactive species and other electrolytes. In Part II of this thesis, the possibility of the ferricenium ion-paired with perchlorate and hexauorophosphate in acetonitrile was discussed firstly employing chronoamperometric technique. Afterwards, the hexaammineruthenium III/II couple supported by chloride, nitrate and sulfate respectively was studied by a similar method. In order to avoid unwanted ion-pairing effects, room temperature ionic liquids can be applied as solvent, which provide high conductivity by their own ionic nature so that experiments can be conducted without adding additional supporting ions. Because of RTILs have distinctive properties, for example, high viscosity, high conductivity and ionic nature, electrochemistry could be greatly changed compared to those in conventional solvents. Part III of this thesis gives a detailed description of this topic. First, a study of the reduction of 1,4-benzonquinone in 1-ethyl-3-methylimidazolium bis(triuoromethanesulfonyl)imide is presented to show the new mechanistic insight into comproportionation in a electrochemical process. Second, a discussion of the oxidation of hydroquinone in the same RTIL is introduced to suggest a possible ECE scheme which was never reported before. The interest of weakly supported electrochemistry is also well-established, which not only provides another alternative strategy to avert ion-pairings but also offers more physical insights into electrochemical processes. Quantitative methods analysing voltammetries without an excess amount of supporting electrolyte are developed by introducing a migration term into the mass transport equation. In Part IV, new mechanistic insights into the reduction of 2-nitrobromobenzene and the dimerisation of 2,6-diphenylpyrylium in acetonitrile were provide by using weakly-supported cyclic voltammetry. Also, pulse techniques was also adopted to investigate the reduction of cobaltocenium and cobalt(III) sepulchrate, giving an alternative way for electrochemical analysis. A major application of electroanalytical chemistry is investigating electrochemical kinetics. Two kinetic models mostly concerned by electrochemists are Butler-Volmer and Marcus-Hush formalisms. The classic phenomenological model, Butler-Volmer formalism successfully describes most common electron transfer kinetics but shows little reference with nature of the involved species, solution and electrode material, while a more physically insightful theory, the Marcus-Hush formalism, takes species natural properties, for instance, a change of distances or geometry in the solvation or coordination shells of the redox, into account although it requires more complex formulations. Comparative studies of these two theories are presented in Part V in order to improve our understanding of the electron transfer kinetics under different circumstances. First, comparison of cyclic voltammograms of the reduction of europium(III) and 2-methyl-2-nitropropane at mercury microhemispherical electrodes was carried out. Second, square wave and differential pulse voltammetric techniques were also employed to further discriminate the two kinetic models. These studies all find that the symetric Marcus-Hush theory assuming the reactants and products have identical force constant dose not satisfactorily agree with the experimental results. Hence, the introduction of asymmetric Marcus-Hush theory was presented considering different oxidative and reductive reorganization energies, which gives reasonable agreement with experiments and makes this theory more insightful.