<p>The demand for heat pumping technologies is expected to see tremendous growth over the next century. Traditional vapor compression cycles are approaching practical limits of efficiency and running out of possibilities for environmentally friendly and safe refrigerants. As a result, there is an increasing interest in pursuing non-vapor compression technologies that can achieve higher efficiencies with alternative working fluids. The chemical looping heat pump (CLHP) investigated here utilizes a chemical reaction to alternate a working fluid between more and less volatiles states. This allows the main compression to take place in the liquid phase and enables the utilization of a range of different working fluids that would not be appropriate for vapor compression technology. </p> <p> </p> <p>Thermodynamic models were developed to assess the potential performance of a chemical looping heat pump driven by electrochemical cells. A number of potential working fluids were identified and used to model the system. The thermodynamic models indicated that the chemical looping heat pump has the potential to provide 20% higher COPs than conventional vapor compression systems. </p> <p> </p> <p>An experimental test stand was developed to investigate the efficiency with which the electrochemical reactions could be performed. The working fluids selected were isopropanol and acetone for reasons of performance and availability. The test stand was designed to measure not only the power consumed to perform the conversion reaction but also the concentration of products formed after the reaction. The experimental tests showed that it was possible to perform the reactions at the voltages required for an efficient chemical looping heat pump. However, the tests also showed that the reactions proceed much slower than expected. To increase the rates of the reactions, an optimization effort on the membrane and catalyst selections was performed. </p> <p> </p> <p>Traditional catalyst materials used by solid polymer electrochemical cells, like those used in the testing, perform best in hydrated environments. The fluids isopropanol and acetone tend to displace water in the membranes, reducing the system conductivity. Multiple membrane types were explored for anhydrous operation. Reinforced sPEEK membranes were found to be the most suitable choice for compatibility with the CLHP working fluids. Multiple catalyst mixtures were also tested in the experimental setup. Density functional theory was used to develop a computational framework to develop activity maps which could predict the performance of catalyst materials based on calculated parameters. </p> <p> </p> <p>A detailed model of the CLHP electrochemical cell was developed. Built on open-source tools, the model was designed to determine the charge, mass, and heat transfers within the cell. The conversion of reactants along the channel of the cell as well as overall power consumption are predicted by the model. The model was validated against measurements and used to determine parameters for a CLHP cell that would have improved conversion performance and energy efficiency compared with the tested cell. </p> <p> </p> <p>The cell model was integrated into an overall system model which incorporates the effect of concentration changes throughout the entire cycle. Compared to the early-stage thermodynamic modeling, consideration of incomplete reactions provided more accurate predictions of the potential performance of CLHP systems. Different cell and system architectures were investigated to boost system performance. The model predictions demonstrated that the CLHP has the potential to provide high heat pumping efficiencies, but more work is still needed to improve the energy density of the system. </p>

Adsorption combined with aqueous phase electrochemical regeneration has been shown by researchers at The University of Manchester (UoM) to offer an alternative approach to the removal of organics from waters and wastewater's. The process, based on a regenerable graphite intercalation compound (GIC) adsorbent, produces no secondary waste, is energy efficient and chemical free. A company, Arvia Technology Ltd., was set up in 2007 to commercialise the technology. As part of a growth and development strategy Arvia investigated other possible applications of the technology and found that odour removal from gas streams might be a good fit with technology features. This Engineering Doctorate (EngD) was a direct investigation into both this technology fit and into the market opportunity for technologies treating odours and volatile organic compounds (VOCs) in gas streams. The research conducted demonstrated that the technology in its different applied forms had certain process drawbacks. Where mass transfer, adsorption and regeneration were combined in a single unit, enhanced transfer as a result of higher pollutant Henry's coefficient was offset by lower adsorbate affinity which varied with hydrophobicity. This relation between affinity and hydrophobicity was different for oxygen functionalised aromatic molecules than for the aliphatic molecules studied. Where adsorption occurred in the gaseous phase and regeneration in the aqueous phase, disadvantages such as short adsorbent packed bed lifetimes and lower current efficiencies of oxidation as a result of adsorbate desorption were shown to be an issue. When the above process challenges were set against the challenging market environment and relatively small market opportunity (approx. £52 million in Europe, 2012) it was difficult to recommend further broad research into the technology. However it was concluded that the concept might still be usefully applied to odour and VOC abatement and that further work should focus on a two phase system with a gas phase adsorbent regeneration technique. The relation observed between adsorbate affinity, hydrophobicity and structure allowed the demonstration of the preferential removal of phenol from solutions containing significantly higher concentrations of aliphatic molecules. This finding is considered the most important project output as it highlights an opportunity to develop Arvia's water treatment technology into a targeted water treatment system for the removal of specific, industrially important, organic contaminants.

Detection of DNA by electrochemical impedance spectroscopy (EIS) has been reported by many authors and assays have been developed using lab setups. However, as for most detection assay methods there are issues to address to enable the development for the sensor market: Long time-to-result & high complexity for labelled assays and a lack of sensitivity and reproducibility for label-free assays. This work considers two different approaches to address the issues of time-to-result and assay complexity. The first part presents work on achieving rapid sequence-specific electrochemical detection of DNA hybridisation to complementary DNA on an electrode surface. To accomplish assay sensitivity to low DNA target concentrations, a signal amplification strategy is often necessary. One approach is to couple an enzyme to the hybridised target molecules and to deposit insoluble dyes in the subsequent enzymatic reaction, which enhances sensitivity through an increase in the impedance signal in presence of a redox mediator. The time typically taken for this process (20 – 40 min) precludes the use outside lab setups. Therefore, a protocol for sensitive detection in the presence of redox mediator is demonstrated on a practical timescale required for use in sensor applications. Based on these results a model for the fundamental understanding of the amplification reaction is presented which explains the retention of sensitivity at these enhanced timescales. This also enabled further optimisation of the assay for application in single base pair mismatch detection in biologically relevant sequences. Moreover, direct detection of the precipitate formation is demonstrated which enables real-time measurement of the enzymatic reaction without redox agent addition and with enhanced mismatch discrimination. The second part investigates the possibility to detect DNA non-sequence-specifically by non-Faradaic means. This approach aims at reducing assay complexity by establishing whether it is possible to sense the presence of polymeric DNA in solution by measuring changes in the properties of the electrochemical double layer without DNA surface hybridisation. In a sensor setup this approach could be linked to a polymerase chain reaction (PCR) to discriminate polymer from nucleotide monomer and thereby enable PCR progress to be monitored. In this work the response in the electrochemical double layer at the interface of blocked metal electrodes and solutions containing DNA are studied by means of EIS. Blocking layers were applied to the electrode surface to prevent unspecific adsorption of molecules and ions to the metal surface whilst preserving the sensitivity to detection of changes in the double layer. The characteristics of surface blocking layers on disposable electrodes are studied as they are key to understand the double layer properties at a blocked surface. A number of self-assembled monolayers are compared with respect to their temperature stability and their blocking characteristics at different potentials and ion concentrations. This established the basis to study the effect of the presence of, initially, a model polyelectrolyte and, ultimately, DNA on the double layer. Polyelectrolyte detection is successfully shown for the model polyelectrolyte, polyacrylic acid. DNA detection was more challenging and possible causes for deviation from the polyacrylic acid response are discussed.

Les phénomènes électrochimiques sont de plus en plus présents dans notre vie quotidienne : ils sont au cœur des batteries de nos ordinateurs, de nos téléphones, dans les piles (à combustibles), etc ... L'objectif de cette thèse est de mieux comprendre les interfaces métal-solvant qui interviennent aux niveaux de ces systèmes (pile à combustible, batteries Li-ion …). Cependant si ceux-ci sont fortement étudiés expérimentalement à la fois dans les laboratoires universitaires et industriels, leur compréhension à l'échelle atomique reste encore imparfaite. Le but de cette thèse est donc d'améliorer la compréhension de l'interface entre l'électrolyte et l'électrode ainsi que sa modification avec le potentiel appliqué à l‘aide de calculs ab initio basés sur la théorie de la fonctionnelle de la densité (DFT). Pour cela au moyen de méthodes de simulation électrochimiques utilisant des approches théoriques spécifiques des surfaces et interfaces développées au sein du laboratoire, nous nous sommes d'abord intéressés à une interface Ruthénium-eau. Le ruthénium est un métal qui crée des interactions fortes avec l'eau : l'eau se trouve alors non dissociée ou partiellement dissociée sur cette surface selon les conditions d'étude. Ainsi, en partant des contradictions apparentes entre résultats expérimentaux présents dans la littérature, nous avons étudiés plus d'une dizaine de phase d'eau sur le ruthénium, dont nous avons extrait le diagramme de phase en fonction du potentiel, de la température, et en tenant compte du fort effet isotopique présent dans ces systèmes. La comparaison de nos résultats calculés avec les résultats expérimentaux nous a permis de rationaliser les observations et d'apporter des réponses sur la cause de l'effet isotopique géant associé à la dissociation de l'eau sur le ruthénium.Dans un second temps nous nous sommes intéressés à une interface lithium-solvant (éthylène carbonate) présente dans les batteries Li-métal. Contrairement à l'étude de l'interface métal-eau précédente nous nous sommes intéressés à la modélisation de la surface et de l'électrolyte liquide. La modélisation du solvant liquide étant plus complexe que celle d'une monocouche d'eau solide adsorbée sur la surface, nous avons donc utilisé une méthode de solvatation implicite que nous avons dû adapter à nos calculs électrochimiques. Nous avons aussi modélisé des molécules de solvant de façon explicite pour pallier aux limites du modèle implicite et inclure les effets de première sphère de solvatation. Notre modèle de solvatation mixte implicite/explicite nous a permis d'étudier les processus électrochimique de réorganisation de surface, de réduction de Li+ ainsi que l'hystérésis/nucléation de surface de Li. / The electrochemical phenomena are increasingly present in our daily lives: they are at the heart of the batteries of our computers, our phones, in batteries (fuels), etc ... The objective of this thesis is to better understand metal-solvent interfaces involved levels of these systems (fuel cell, Li-ion batteries ...). However if they are heavily studied experimentally both in academic and industrial laboratories, understanding at the atomic scale is still imperfect. The aim of this thesis is to improve understanding of the interface between the electrolyte and the electrode and its modification with the potential applied using ab initio calculations based on the Density Functional Theory (DFT).For this simulation using electrochemical methods using specific theoretical approaches of developed surfaces and interfaces in the laboratory, we primarily interested in a ruthenium-water interface. Ruthenium is a metal that creates strong interactions with water: water is then undissociated or partially dissociated on this surface under the conditions of study. Thus, starting from the apparent contradictions between experimental results present in the literature, we have studied more than a dozen water phase on ruthenium, we extract the phase diagram based on potential, temperature, and taking into account the strong isotope effect present in these systems. Comparison of our calculated results with the experimental results allowed us to rationalize the observations and provide answers on the cause of the giant isotope effect associated with the dissociation of water on ruthenium.In a second step we are interested in a lithium-solvent interface (ethylene carbonate) present in the Li-metal batteries. Unlike the previous study of metal-water interface we are interested in modeling the surface and the liquid electrolyte. The modeling of the liquid solvent is more complex than a single layer of solid water adsorbed on the surface, so we used a method of implicit solvation that we had to adapt our electrochemical calculations. We also modeled explicitly solvent molecules to overcome the limitations of the implicit model and include the effects of the first solvation sphere. Our model of mixed implicit solvation / explicitly allowed us to study the electrochemical surface reorganization process, Li + reduction as well as hysteresis / Li surface nucleation.

Technological progress is determined to a great extent by developments of novel materials from new combinations of known substances with different dimensionality and functionality. We investigate the development of 3D ‘hybrid’ nanomaterials by utilizing graphene based systems coupled with transition metal oxides (e.g. manganese oxides MnO2 and Mn3O4). This lays the groundwork for high performance electrochemical electrodes for alternative energy owing to their higher specific capacitance, wide operational window and stability through charge-discharge cycling, environmental benignity, cost effective, easily processed, and reproducible in a larger scale. Thus far, very few people have investigated the potential of combining carbon sheets that can function as a supercapacitor in certain systems with transition metals that have faradaic properties to create electrochemical capacitors. Previous work by Wang et al. has focused on the structural combination of Mn3O4 and graphene based materials,1 and research by Jafta et al. studied the electrochemical properties of MnO2 with GO.2 We find that both physical and chemical attachment of manganese oxide on graphene allows for electrical interplay of the materials as indicated in electrochemical analysis and Raman spectroscopy. Attachment of the two materials is also characterized by scanning electron microscopy and X-ray diffraction.

This thesis mainly concerns the application of electrochemical impedance spectroscopy (EIS) and electrochemical noise analysis (ENA) to the study of CO(subscript)2 corrosion of mild steel and its inhibition. The primary focus is on the use of EIS and ENA to monitor inhibitor film performance and to evaluate inhibitor film persistency.EIS was shown to be a suitable technique to study CO(subscript)2 corrosion product scale, and inhibitor films. The formation and deterioration of protective scales and inhibitor films is found to be accompanied by characteristic spectral changes and a rapid change in electrode impedance. EIS data were used to calculate corrosion related parameters such as the resistances and capacitances of inhibitor layers, and the charge transfer resistance and double layer capacitance. These parameters were used to analyse inhibitor mechanisms, determine corrosion rates and the persistence of inhibitor films.ENA is also a suitable technique to monitor the formation and deterioration of inhibitor films. It has the advantage of being able to monitor rapid processes which occur within one second. Several technical and theoretical developments were made in this thesis including the development of a new method of instantaneous corrosion rate measurement to study fast corrosion processes (the continuous noise resistance calculation method). Experimentally, the noise resistance was confirmed to be similar to linear polarisation resistance in the systems studies. The theoretical background and the advantages and disadvantages of the ENA technique are also discussed.Corrosion product scales formed under different conditions were investigated using EIS and surface analysis techniques. Temperature, pressure and exposure time were confirmed to be the important factors influencing the degree of protection given by the scale. The morphology of corrosion scales ++ / showed an obvious correlation to their protective ability. Electron microscopy revealed two types of crystal structures on corroded steel coupons. The smaller crystals associated with one of these structures was found to contribute most to corrosion protection.Several typical CO(subscript)2 corrosion inhibitors, including an imidazoline and a quaternised amine, were studied by EIS. A multi-layer model was employed to explain the EIS characteristics and self-repairing ability of imidazoline films. A quaternised amine film is most probably a physically or electrostatically adsorbed molecular layer which forms rapidly and desorbs easily.The deterioration of films, formed by commercial batch treatment inhibitors, was found to occur in three stages which were indicated or characterised by Bode phase-angle plots. A method to determine inhibitor film persistency was developed. This method is based on determining the three stages of inhibitor film deterioration, and the continuous measurement of corrosion rate, which is accessible at the second and third stages of film deterioration.

The aim of this project is to develop strategies for fabrication of carbon electrode surfaces with a view to creating stable and versatile monolayer systems for sensing and other applications. Glassy carbon (GC) electrodes have been successfully modified with versatile monolayers via the electrochemical reduction of aryl diazonium salts. The surfaces modified with diazonium salt monolayers were properly characterised by electrochemistry, AFM and XPS. The rates of heterogeneous electron transfer through organic monolayers on GC, Pyrolysed Photoresist Films (PPF) and gold surfaces have been studied using ferrocene as the redox probe. The diazonium salt monolayers created on GC surfaces demonstrated very stable ability and can serve as a good alternative to alkanethiol selfassembled monolayers on gold electrodes for sensing purposes. Tripeptide Gly-Gly-His modified GC electrodes have been successfully used as the electrochemical copper sensors and were found to be extremely stable. PPF has proved to be a good alternative to the GC electrode for the commercialisation of the fabricated electrochemical sensors. The most important and difficult task of this project is to fabricate glucose biosensors and immunosensors on carbon electrodes. The rigid and conjugated molecular wires (MW) as the efficient conduit for electron transfer, and a molecule with poly(ethylene glycol) chains (PEG) as an insulator for reducing the non-specific protein adsorption were successfully synthesised and introduced in the sensing systems. MW modified on GC electrodes can be used to explore the deeply buried active site of glucose oxidase to achieve direct electron transfer of GOx from the active centre FAD through the MW to the underlying GC electrode, and to fabricate third generation biosensors. The interface comprising mixed monolayers of MW and PEG has the ability to facilitate efficient electron transfer. A label-free immunosensor system has been successfully developed for electrochemical detection of biomolecular pairs such as biotin/antibiotin with low detection limitation based on mixed monolayers of MW and PEG modified GC electrode surfaces. In addition, a displacement assay has shown that the free biotin can compete with the attached biotin for binding antibiotin. SWNTs can be used as an alternative to MW to fabricate another label-free immunosensor system due to the high efficiency of electron transfer that SWNTs have demonstrated.

Hexachlorobenzene (HCB) is a pollutant, and there is an urgent need to degrade it. Two methods of degrading HCB to ethers are nucleophilic substitution and electroreduction, chosen for their viability and safety. The kinetics of substitution of HCB by potassium hydroxide and methanol were examined. The substitution of HCB by methoxide produced 1,2,3,5-tetrachloro-4.6-dimethoxybenzene (1,2,3,5-TCDMB) as the major substitution product, and side reactions produced extra chloride due to other substitution products. Thus, the proposed reaction mechanism is complicated due to the formation of ethers and phenols due to consecutive and parallel reactions. The substitution products of HCB were uncatalytically and catalytically electroreduced. Products with increasingly more methoxy substituents had lower electron affinities and increasing positive free energies. Catalysed electroreduction was more effective than uncatalysed electroreduction in dechlorinating the HCB substitution products to aromatic ethers. The most effective organic catalysts were those that possessed the lowest electron affinity as reflected in the reduction potential. A combination of nucleophilic substitution and electroreduction of HCB and its substitution products produced mono-, di- and trimethoxide chloroaromatic ethers and phenols. These products, particularly the ethers, may have future applications as fragrance ingredients / Doctor of Philosophy (PhD)

A new versatile computer controlled electrochemlcal/ESR data acquisition system has been developed for the Investigation of short-lived radicals with life-times of 20 milliseconds and greater, Different computer programs have been developed to monitor the decay of radicals; over hours or minutes, seconds or milliseconds. Signal averaging and Fourier smoothing is employed in order to improve the signal to noise ratio. Two microcomputers are used to control the system, one home-made computer containing the M6800 chip which controls the magnetic field, and an IBM PC XT which controls the electrochemistry and the data acquisition. The computer programs are written in Fortran and C, and call machine language subroutines, The system functions by having the radical generated by an electrochemical pulse: after or during the pulse the ESR data are collected. Decaying radicals which have half-lives of seconds or greater have their spectra collected in the magnetic field domain, which can be swept as fast as 200 Gauss per second. The decay of the radicals in the millisecond region is monitored by time-resolved ESR: a technique in which data is collected in both the time domain and in the magnetic field domain. Previously, time-resolved ESR has been used (without field modulation) to investigate ultra-short-lived species with life-times in the region of only a few microseconds. The application of the data acquisition system to chemical systems is illustrated. This is the first time a computer controlled system whereby the radical is generated by electrochemical means and subsequently the ESR data collected, has been developed.

A series of 2,6- and 3,5-ethynylpyridyl compounds and their cobalt clusters have been prepared and analysed in Chapter 2, in order to study through-space and through-bond interactions between the ethynyl arms. Bidentate N- donor ligands, such as bipyridine and o-phenanthroline with alkyne functionality have been used extensively as building blocks for a wide range of molecular materials, but monodentate ethynylpyridyls have received less attention. The results showed that while there is no orbital restriction on a RC[triple bond]C-n-[pi]�cc-C[triple bond]CR through-bond interaction in 2,6-ethynylpyridyls, no significant interaction exists. Nevertheless, there are intramolecular interactions as manifested in the distortions which occur in the solid state structure of the compounds and the lability of the diphenylphosphine methane (dppm) moieties in the oxidised Co₂(CO)₄dppm species. Polymerisation by Sonogashira coupling between dibromo pyridines or diiodo ferrocene and ethynyl pyridines resulted in only oligomeric fractions that could be separated. The thesis also reports the synthesis and characterization of some novel naphthalimide monomers with acrylic and allyl headgroups. The naphthalimide moiety is substituted in the 4-position with various functionalities. This is presented in detail in Chapter 3 of the thesis. The monomers� structure is the following: [illustration omitted] wherein: A may be a polymerizable group (methacrylate or allyl), which includes a spacer entity (aliphatic or aromatic); B is selected from an ethenyl or ethynyl linked organometallic group, a halogen and/or an amine (i.e. bromo, ethynylferrocene, ethenylferrocene, trimethylsilylethynyl, nitro, piperidine and ethenylpiperidine). The acrylic monomers were synthesized by coupling 4-bromo-1,8-naphthalic anhydride with an amino alcohol to give an imide, which then was coupled with methacryloyl chloride to provide the methacrylate. Functionalization in the 4-position of the naphthalimide moieties was achieved by Sonogashira and Heck coupling reactions with for example ethynylferrocene, trimethylsilyl acetylene, vinylferrocene. For the allyl monomers synthesis, a reaction between allyl amine and 4-Bromo-naphthalic anhydride provided 4-bromo-naphthalimido allyl, which was then functionalized by further Sonogashira and Heck coupling reactions. The monomers were polymerised and copolymerised with other widely used comonomers, such as methyl methacrylate, methyl acrylate, styrene, vinyl carbazole and acrylonitrile. The polymerisation processes and the full analyses of the (co)polymers are described in Chapter 4. Free radical polymerisation, FRP, initiated by azo bisisobutyronitrile, AIBN at elevated temperature was the main technique employed for making the (co)polymers. Atom Transfer Radical Polymerisation, ATRP was conducted for some monomers although the results were inconclusive (the yields were low, under 50%, but the molecular weight distributions were quite narrow, PDI�s <1.7). Heck coupling polymerisation was performed for the bromo- substituted methacrylic and allyl monomers and supplied colorful, well-defined polymeric materials, with low polymerisation degrees. All polymers were analyzed by HPLC, NMR, UV-VIS, IR, electrochemistry and fluorescence. The (co)polymers made by FRP had various molecular masses (Mn = 3000- 90.000), whereas the polydispersities were PDI = 1.4- 4.6. Most of the (co)polymers were fluorescent and had good thermal and electrochemical properties. Potential applications of the polymers have been suggested and relevant literature background in the field is provided in both Chapters 1 and 4. The monomers/ polymers are stable compounds (no special storage conditions required) and can act as good candidates for potential applications in light emitting devices, as resins/ binders for coating materials, in the dyes and pigment industry and also for manufacturing of conducting polymers and/or composite materials.