Precipitated surface films form when metal cations are produced faster than they can move away from the dissolving interface. This build up of cations results in supersaturation conditions, which cause a solid to precipitate. The precipitated solid affects ion transport and thus the dissolution kinetics, which ultimately control the two systems studied here. X-ray diffraction, small angle X-ray scattering and fast radiography were chosen to study the metal/solution interface in-situ, using synchrotron radiation. The AC electrograining system is a widely used industrial process whereby an alternating current is applied to aluminium plates to form a pitted surface. During this process, an Al(OH)3 surface gel (smut) forms within seconds whilst electrograining continues for several minutes in its presence. Although smut formation has been investigated previously, how the smut affects metal dissolution is currently unknown and is the primary goal of this project. The second system is a nickel “artificial pit,” which is commonly used to simulate pit propagation. In this system, a salt film is precipitated by imposing a large overpotential whilst restricting transport through a 1-D pit. Interfacial phenomena that occur during salt film formation are investigated towards an understanding of how the salt film forms.

Single walled carbon nanotubes (SWNTs) have unique structural and electronic properties which drive their use in many different fields of modern technology. In electrochemistry, SWNTs have been shown to have outstanding electrochemical characteristic enabling their application in trace level electroanalysis amongst other areas. The SWNT electrochemical activity has been described as originating solely from sidewall structural defects, oxidised open ends and post-growth metal nanoparticles (NPs). However, recent studies have demonstrated the electrochemical activity of pristine and defect-free SWNTs, grown on insulating substrates using catalysed chemical vapour deposition (cCVD) method, suggesting sidewalls support electron transfer (ET). In this thesis cCVD is employed to grow SWNTs of different geometrical arrangements on single crystal stable temperature (ST)-cut quartz substrates for the development of novel nanoelectrodes (NEs) and optically transparent electrodes (OTE). Majority of the work concentrates on cCVD and electrochemical studies of horizontally aligned SWNTs on ST-cut quartz. The quality of SWNT horizontal arrangement is shown to strongly depend on the crystallographic structure of the ST-cut quartz substrate. Perfectly aligned SWNTs are utilised as (i) one dimensional (1D) templates for electrodeposition of silver NPs, and (ii) NEs for the fundamental assessment of SWNT electrochemical behaviour. Formation of uniform silver nanowires (NWs) on most of the SWNTs is possible at high deposition overpotentials and times. Uniformity of the NWs indicates high structural quality of the horizontally aligned SWNTs. Nernstian behaviour of SWNT NEs for simple outer-sphere redox couples is shown in localised voltammetric measurements with microcapillaries, 25 - 50 μm in diameter serving as probes, filled with the redox active electrolyte solution and the reference electrode (RE). For the first time measurements at single SWNTs in the positive and negative potential window are performed, revealing a strong dependence of SWNT electrochemical activity on SWNT structural and electronic properties. Finally, careful tuning of the cCVD parameters enables growth of interconnected SWNT networks on ST-cut quartz, with complete surface coverage and no sign of alignment. These ultrathin mats are utilised as novel OT disk ultramicroelectrodes (OT-UMEs) with complete transparency in the ultraviolet and visible (UV-Vis) range, metallic behaviour and improved electrochemical usability in comparison to conventional solid UMEs.

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This thesis describes the investigation of the electrochemistry principles, technology, construction and composition of the electrode materials, electrolyte and additives used in redox flow batteries. The aim was to study a flow battery system with an appreciable working performance. The study explores and compares mainly three different redox flow battery technologies; all-vanadium, soluble lead-acid and a novel copper-lead dioxide flow batteries. The first system is based in sulfuric acid electrolyte environment whilst the other two are in methanesulfonic acid. Various cell parameters such as cell voltage, individual electrode potentials, flow rate and efficiencies (in particular voltage, charge and energy) have been utilized to compare. Further research in other redox couples and comparative study towards the design, construction and electrochemistry, along with the performance of these three batteries in relation to other electrochemical energy storage technologies available was also discussed. These technological studies are of particular interest for applications in the renewable energy storage (offshore and onshore) and sustainable energy research (grid integration and micro generation).

A new method to fabricate 3D batteries using mixed (ion and electron) conducting polymers as electrolytes has been developed. The majority of the work was done using the polymer Poly(1,11-Di(N-pyrryl)-3,6,9-trioxaundecane) (PP2O3) because it demonstrated mixed conducting properties. Methods are presented for synthesising the monomer then polymerising either electrochemically to give films or chemically to give bulk samples or powders. The conductivities of both polymers were determined by Electrochemical Impedance Spectroscopy (EIS). For polymer films prepared electrochemically on conducting substrates, the conductivities were determined as a function of the p-doping level, using a cell containing a liquid electrolyte and an applied bias potential. The results were fitted with a transmission line model and revealed an electronic conductivity varying from 4.20 x10-10 to 1.69 x10-5 S/cm dependent on the doping level, and a relatively constant ionic conductivity of 1.74 x10-6 S/cm. Oxidative treatment by overdoping resulted in a reduction of electronic conductivity by a factor of about 50,000 times smaller at the potential of maximum conductivity, around 0.30 V with a small change in the ionic conductivity. Bulk samples of the chemically prepared polymer were examined between two blocking electrodes. The electronic conductivities of the as-prepared and chemically oxidized samples were both quite low, around 10-7 and 10-8 S/cm, whereas the ionic conductivity of both samples was around 10-5 and 10-6 S/cm. These values were slightly higher than those of the film samples due to a presence of PC plasticiser in bulk samples. Finally the polymers were tested as electrolyte/separators in lithium ion battery cells: the electrochemically treated film was found to be an effective separator between a 3D LiFePO4 positive electrode and a liquid lithium amalgam negative, and the chemically prepared materials showed a capacity of around 150 mAh per gram LiFePO4 in a conventional Li/LiFePO4 cell,. These experiments demonstrate a proof of concept for the use of mixed conducting polymers as electrolytes in lithium battery systems

New methods for the high-throughput characterisation of polymer electrolytes have been developed. Polymer electrolytes for use in lithium ion batteries have been prepared in a novel systematic manner that involves parallel preparation and subsequent high-throughput conductivity measurements of up to 64 individual compositions in a multi-electrode cell. The method of casting the polymer electrolytes directly onto the substrate also allows high-throughput characterisation by x-ray diffraction. The technique was applied specifically to a ternary system of PVdF-HFP, LiTFSI and PC. By preparing a vast array of samples across the composition range, it was found that the conductivity reached a maximum value when the weight fraction composition was 0.45/0.45/0.1 of PVdF-HFP/LiTFSI/PC with completely free standing samples. The trend of increasing conductivity tended towards the maximum liquid conductivity of LiTFSI/PC. Due to limitations of this method with highly conductive polymer electrolytes, a second novel alternative polymer synthesis, preparation and measurement technique was developed for proton conducting polymers for fuel cell applications. In addition a second multi-electrode cell was designed and constructed specifically allowing AC Impedance measurements to be taken whilst allowing the polymer electrolytes to be subjected to temperature and relative humidity effects. The multi-electrode cell was calibrated using commercially available Nafion samples before being used with synthesised samples. PEEK was sulfonated to SPEEK using varying temperatures and reaction times to obtain many samples with differing DS values. The conductivity of the samples was measured in situ using an in-plane 4 electrode impedance measurement, over a range of environmental conditions. It was found that water loss caused significant conductivity decay under PEMFC conditions for Nafion but not for SPEEK samples. SPEEK with a DS of 75 % was found to have the maximum SPEEK equilibration conductivity of 0.177 S cm-1, a value comparable to that of commercial membranes. By blending this sample with a lower DS SPEEK, high conductivity values could be maintained at temperatures of 105 °C and 75 % relative humidity with maintained mechanical integrity. When an inorganic additive (Zr(HPO4)2) was introduced into the blended samples, the conductivity was enhanced further due to increased water retention within the phosphate structure.

The factors effecting discharge rate limitation within LiFePO4 composite electrode structures have been investigated. It was found that for composite electrodes containing ‘small particles’ of active material solid state processes are not necessarily rate limiting. A simple model has been developed to describe the rate limitation that occurs in the composite electrode structure due to electrolyte concentration, electrode thickness and lithium ion transference number. The conformal electrodeposition of cathode materials onto 3D current collectors has been achieved with good control of film thickness. The advantage of the 3D current collector configuration over a conventional thin film arrangement has been realised by a 250 times capacity increase for a given footprint area. It was suggested the observed rate performance of half-cell 3D microbatteries, based on a manganese dioxide cathode and a lithium foil anode, was limited by the lithium ion transport distance through the porous 3D structure. The electrodeposition of conformal polymers layers onto 3D substrates was investigated. The use of electrodeposited, electrolyte swollen, poly(acrylonitrile) and poly(aniline) films as polymer electrolytes was demonstrated. A novel method for the determination and differentiation of electronic and ionic resistance in electrodeposited polymer layers has been developed. A ‘working’ cell based on consecutively electrodeposited cathode and polymer electrolyte layers and a ‘soft contact’ liquid anode was presented

In this work, the finite element modelling of 2D and 3D scanning electrochemical microsopy (SECM) systems is presented. The main focus has been on the influence of tip geometry and the presence of defects on the limiting current of the SECM tip. The geometry of the electrode of particular interest is conical with conical insulation, as this is the shape of AFM-SECM probes fabricated by our coworkers. This thesis presents an extensive study of the electrochemical response of conical electrodes both in the bulk solution and close to a surface. Key equations were derived for conical electrodes and a thorough quantitative analysis of the influence of the tip geometry, be it the parameters describing it or the presence of defects, is reported. A novel equation was derived to calculate the current in the bulk at a conical electrode with conical insulation and an extensive study of possible defects was conducted to allow users to adjust the expression and obtain a more accurate estimation of the limiting current. The spatial resolution defined as the ability of an electroactive probe to detect a conducting region of a given size- and the lateral resolution -the distance necessary to fully resolve a conducting region form an inert region- were both investigated for a range of geometries as well as for a selection of defects. This enables us to draw conclusions on the ideal tip, and how sensitive it would be to features of the substrate. A set of equations was derived to describe positive and negative feedback approach curves for cones, and steps were defined for users to determine the shape of the electrode from experimental approach curves. Simulated curves are also provided to help with the extraction of kinetics at the substrate surface from the experimental approach curves. Finally, the influence of a ring disc tip geometry was evaluated by monitoring the collection efficiency as a function of tip-substrate distance for different disc-ring separations.

One of the major bottlenecks in catalyst development for proton exchange membrane fuel cell (PEMFC) is the lack of fast high-throughput testing methods. Fast screening techniques enable a large number of catalysts to be tested in a relatively short time under the same conditions. This project was focused on developing systems for screening catalysts used for the oxygen reduction reaction (ORR) at the cathode of PEMFCs. The first system developed was the 64 channel pin electrode array, using liquid electrolyte. The developed method improved both the quality and reproducibility of the data and has been used to rank catalyst samples, as well as to optimize loadings and the preparative methods of inks. The second system developed was a 25 channel array fuel cell, which operated under conditions analogous to real fuel cell environments. Both methods allowed trends in characteristics and activities of a series of catalysts to be established more rapidly than individual single-electrode methods such as half cell, rotating disc electrode (RDE) or fuel cell. The results from the two high-throughput methods are compared to those of the single channel systems. The mass and specific activities towards reduction of oxygen were studied using a series of Pt/C and PtCo/C catalysts. The catalytic properties of the Pt based carbon-supported catalysts were related to their structure e.g. particle size and lattice parameter, which were obtained mainly using Xray diffraction (XRD). It was found that the results acquired using parallel screening methods were similar to those collected with a RDE and a fuel cell. The thesis concludes with suggestions regarding the future improvement/development of high-throughput techniques. For the 64 channel array system the problem associated with the corrosion of the components should be solved. Similarly, the major changes for the array fuel cell would be to modify a heating system and further development of the anode flow field.

Photodynamic Therapy (PDT) is a ôancer treatment involving selective retention of a photoactive drug in tumour cells and tissue. Subsequent illumination with light of the correct wavelength can result in tumour destruction, generally assumed to be mediated by singlet oxygen ( 102) generated by the light-excited drug. Among such compounds, the biological stains methylene blue and toluidine blue 0, both phenothiazinium derivatives, have been widely studied with respect to their use in PDT and potential antimicrobial applications. However, studies of novel methylene blue derivatives (MBD) for PDT are scarce in the literature. We have synthesised a range of novel phenothiazinium derivatives, in particular 3,7-disubstituted analogues and explored the use of electrochemical methods in assessing their potential efficacy in PDT. A range of phenothiaziniums were synthesised by oxidation of the appropriate precursor phenothiazines by iodine and were characterised for synthetic purposes by infrared spectroscopy, nuclear magnetic resonance, ultravioletvisible spectroscopy, mass spectrometry and thin layer chromatographic techniques. The ability of the photosensitiser to resist reduction to the colourless Leuco form by tumour cells means that the efficiency of photosensitisation is maximised. The thermodynamic and kinetic susceptibilities of the synthesised phenothiaziniums to reductive bleaching was assessed using cyclic voltammetric and electrogravimetric methods.