Líquidos Iônicos eletropolimerizáveis são caracterizados como líquidos iônicos que possuem um grupo eletropolimerizável ligado ao cátion ou ânion, a partir da eletropolimerização destes líquidos iônicos ocorre a imobilização dos íons em uma estrutura polimérica. Neste trabalho é apresentado a síntese de um líquido iônico eletropolimerizável onde anilina foi introduzida como grupo eletropolimerizante no cátion metil-imidazólio. Várias metodologias foram testadas para a eletropolimerização deste líquido iônico, envolvendo a utilização de solventes orgânicos e líquidos iônicos como eletrólitos. A copolimerização com anilina mostrou-se eficiente para obtenção de filmes poliméricos com a presença do monômero sintetizado. A influência deste monômero presente no copolímero foi estudada em relação ao comportamento eletroquímico, demonstrando o aumento da eletroatividade do polímero em líquidos iônicos apróticos. Em relação à morfologia, observou-se que a presença do monômero produz filmes mais compactos diferentemente da polianilina que apresenta uma morfologia dendrítica. Os processos eletrocrômicos para o copolímero não sofrem defasagem em relação aos processos eletroquímicos como observados na polianilina. Os processos redox do material foram acompanhados por EQCM-D demonstrando que a compensação de carga ocorre a partir do fluxo de cátions. Assim a presença monômero sintetizado no copolímero afeta o comportamento da polianilina, assim como qualquer substituinte volumoso, porém o copolímero apresenta propriedades intrínsecas de líquidos iônicos, demonstrando a formação de um material multifuncional. / Electropolymerizable lonic liquids have groups that are susceptible to electropolymerization bounded either to the cationic or anionic structure. In such cases, the ionic species can be immobilized into a polymeric matrix. This work presents the synthesis of an electropolymerizable ionic liquid in which aniline was inserted as the eletrocpolymerizable group in methyl-imidazolium. Several methods were tested for the electropolymerization, involving the use of organic solvents or ionic liquids as electrolytes. The copolymerization with aniline units was effective to obtain polyrnenc films in the presence of the synthesized monomer. The influence of the monomer in the copolymer was studied with respect to the electrochemical behavior, showing the increasing of the polymer electroactivity in aprotic ionic liquid electrolyte. The presence of the monomer produces more compact films than polyaniline which presents a dendritic morphology. The spectroeletrochemical processes for the copolymer do not suffer lag in relation to electrochemical processes as observed in polyaniline. The redox processes were monitored by EQCM-D demonstrating that the charge compensation takes place from the flow of cations. The presence of the synthesized monomer in the copolymer affects the behavior of polyaniline, as well as any substituent in the aniline, however the copolymer shows intrinsic properties of ionic liquids, demonstrating the formation of a multifunctional material

abstract: In this dissertation, micro-galvanic corrosion effects and passivation behavior of single-phase binary alloys have been studied in order to formulate new insights towards the development of “stainless-like” lightweight alloys. As a lightweight material of interest, Mg-xAl alloys were studied using aqueous free corrosion, atmospheric corrosion, dissolution rate kinetics, and ionic liquid dissolution. Polarization and “accelerated” free corrosion studies in aqueous chloride were used to characterize the corrosion behavior and morphology of alloys. Atmospheric corrosion experiments revealed surface roughness and pH evolution behavior in aqueous environment. Dissolution in absence of water using choline-chloride:urea ionic liquid allowed for a simpler dissolution mechanism to be observed, providing additional insights regarding surface mobility of Al. These results were compared with commercial alloy (AZ31B, AM60, and AZ91D) behavior to better elucidate effects associated with secondary phases and intermetallic particles often present in Mg alloys. Aqueous free corrosion, “accelerated” free corrosion and ionic liquid dissolution studies have confirmed Al surface enrichment in a variety of morphologies, including Al-rich platelet and Al nanowire formation. This behavior is attributed to the preferential dissolution of Al as the more “noble” element in the matrix. Inductively-coupled mass spectroscopy was used to measure first-order rate reaction constants for elemental Mg and Al dissolution in aqueous chloride environment to be kMg= 9.419 x 10-6 and kAl = 2.103 x 10-6 for future implementation in kinetic Monte Carlo simulations. To better understand how “stainless-like” passivation may be achieved, Ni-xCr alloys were studied using polarization and potential pulse experiments. The passivation potential, critical current density, and passivation current density were found to decay with increasing Cr composition. The measured average number of monolayers dissolved during passivation was found to be in good agreement with percolation theory, with a fitted 3-D percolation threshold of p_c^3D=0.118 compared with the theoretical value of 0.137. Using these results, possible approaches towards achieving passivation in other systems, including Mg-Al, are discussed. / Dissertation/Thesis / Doctoral Dissertation Materials Science and Engineering 2018

The electrochemical double layer (EDL) at the solid–liquid interface is the near surface region where important electrochemical processes (e.g., electrodeposition, corrosion, and heterogeneous catalysis) take place. Subtle changes in the electrode surface material/topography and the nature of the fluid medium can drastically alter interactions between liquid molecules and the solid surface. A better understanding of this interfacial region can help advance numerous applied fields, such as battery technologies, solar cells, double layer capacitors, and carbon dioxide capture/conversion. Ionic liquids (IL) are an emerging class of solvents that could replace traditional aqueous/non-aqueous solvents due to their advantageous physiochemical properties (e.g., wide solvent window, high thermal stability, and excellent solvating power). However, our understanding of the near-surface structure of ILs in the EDL is still being developed. This thesis focuses on the fundamental electrochemical behavior of ILs to help understand its interfacial behavior in three main areas: 1) the nature of capacitance-potential relationships in neat ILs, 2) the role of ‘user-defined’ experimental variables on capacitive electrochemical measurements, and 3) the impact of IL + water mixtures on experimental data. The general shape of capacitance-potential curves can suggest at the broad architecture of the EDL region. Fundamental capacitive studies of the IL EDL show a wide range of results, even for similar electrochemical systems. Theoretical predictions suggest the capacitance-potential curve should exhibit bell- or camel-shaped curvature depending on the nature of the IL. Experimental observations have demonstrated several functional shapes such as U-shaped, bell-shaped, camel-shaped, and relatively featureless responses. Much of the work in this thesis starkly contrasts theoretical expectations by demonstrating capacitive behavior that is analogous to high temperature molten salts and dilute aqueous electrolytes with metallic and non-metallic electrode materials. However, our systematic studies of a model IL electrochemical system reveal that there are several ‘user-defined’ experimental variables (i.e. potential scan direction, data acquisition protocol, experimental technique, and potential range probed) which in some instances can significantly impact the resulting capacitance curvature. Some of these variables are often overlooked in the literature and our efforts are aimed at uniting the scientific community in this area to help better compare and understand results. An additional experimental variable of importance is the sorption of water into ILs, which is nearly impossible to prevent due to their hygroscopic nature. The presence of water is known to have a significant effect on the resulting mixtures’ bulk and interfacial properties. While the interaction between ILs and water can significantly vary depending on the nature of the IL, this thesis demonstrates that within small quantities (e.g., < 5000 ppm) of sorbed water there are only minor changes in spectroscopic and electrochemical responses. Collectively, the work outlined in this thesis helps the scientific community better understand electrochemical measurements in IL solvents by examining key analytical variables associated with capacitive measurements. The fundamental electrochemical studies described in this thesis demonstrate that the solid-liquid interface for IL solvents is response to even subtle changes in surface chemistries. These governing interfacial properties have ramifications in myriad applications from energy storage to lubrication.

Potential electrolytes for dye-sensitized photoelectrochemical solar cells have been synthesized and their applicability has been investigated. Different experimental techniques were used in order to characterize the synthesized electrolytes, such as elemental analysis, electrospray ionisation/mass spectrometry, cyclic voltammetry, dynamic viscosity measurements, as well as impedance, Raman and NMR spectroscopy. Some crystal structures were characterized by using single crystal X-ray diffraction. In order to verify the eligibility of the ionic compounds as electrolytes for photoelectrochemical solar cells, photocurrent density/photovoltage and incident photon-to-current conversion efficiency measurements were performed, using different kinds of light sources as solar simulators. In electron kinetic studies, the electron transport times in the solar cells were investigated by using intensitymodulated photocurrent and photovoltage spectroscopy. The accumulated charge present in the semiconductor was studied in photocurrent transient measurements. The ionic liquids were successfully used as solar cell electrolytes, especially those originating from the diethyl and dibutyl-alkylsulphonium iodides. The highest overall conversion efficiency of almost 4 % was achieved by a dye-sensitized, nanocrystalline solar cell using (Bu2MeS)I:I2 (100:1) as electrolyte (Air Mass 1.5 spectrum at 100 W m-2), quite compatible with the standard efficiencies provided by organic solvent-containing cells. Several solar cells with iodine-doped metal-iodidebased electrolytes reached stable efficiencies over 2 %. The (Bu2MeS)I:I2-containing cells showed better long-term stabilities than the organic solvent-based cells, and provided the fastest electron transports as well as the highest charge accumulation. Several polypyridyl-ruthenium complexes were tested as solar cell sensitizers. No general improvements could be observed according to the addition of amphiphilic co-adsorbents to the dyes or nanopartices of titanium dioxide to the electrolytes. For ionic liquid-containing solar cells, a saturation phenomena in the short-circuit current densities emerged at increased light intensities, probably due to inherent material transport limitation within the systems. Some iodoargentates and -cuprates were structurally characterized, consisting of monomeric or polymeric entities with anionic networks or layers. A system of metal iodide crownether complexes were employed and tested as electrolytes in photoelectrochemical solar cells, though with poorer results. Also, the crystal structure of a copper-iodide-(12-crown-4) complex has been characterized / QC 20101013

Soybean oil, palm oil and waste cooking oil as feedstock were used to measure the effects of different heating methods, reaction time, molar ratio of methanol to oil, temperature, power, catalyst type and catalyst concentration on the biodiesel yield in this study. Additionally, reducing reaction time for the transesterification reaction used microwave heating to make more complete. The optimized operating conditions of conventional heating used palm oil, concentration for 0.75 wt% sodium methoxide, molar ratio of methanol to oil for 6:1, reaction time for 90 min and reaction temperature for 60 ¢J offered the best yield of 98.1%. the microwave heating used palm oil, concentration for 0.75 wt% sodium methoxide, molar ratio of methanol to oil for 6:1, reaction time for 3 min and power for 750 W offered the best yield of 99.5% Used soybean oil and palm oil as biodiesel feedstock production, its yield was higher than the waste cooking oil. This reason is caused by composition complex and high viscosity of waste cooking oil compare with pure vegetable oil. The catalyst of sodium methoxide is higher effective than sodium oxide used in transesterification reaction, because the reaction process will not formation of water and saponification. Use ionic liquid [Pyr12CN][Cl], [MorEtH][HSO4], [MorMeMe][MeSO4], [PyrMeH][HSO4] and [MorMeEt][EtSO4] as biodiesel catalyst, the optimized operating conditions of concentration for 2.00 wt% [Pyr12CN][Cl], molar ratio of methanol to oil for 6:1, reaction time for 6 min and power for 750 W offered the best yield of 98.1%.

<p>Potential electrolytes for dye-sensitized photoelectrochemical solar cells have been synthesized and their applicability has been investigated. Different experimental techniques were used in order to characterize the synthesized electrolytes, such as elemental analysis, electrospray ionisation/mass spectrometry, cyclic voltammetry, dynamic viscosity measurements, as well as impedance, Raman and NMR spectroscopy. Some crystal structures were characterized by using single crystal X-ray diffraction.</p><p>In order to verify the eligibility of the ionic compounds as electrolytes for photoelectrochemical solar cells, photocurrent density/photovoltage and incident photon-to-current conversion efficiency measurements were performed, using different kinds of light sources as solar simulators. In electron kinetic studies, the electron transport times in the solar cells were investigated by using intensitymodulated photocurrent and photovoltage spectroscopy. The accumulated charge present in the semiconductor was studied in photocurrent transient measurements.</p><p>The ionic liquids were successfully used as solar cell electrolytes, especially those originating from the diethyl and dibutyl-alkylsulphonium iodides. The highest overall conversion efficiency of almost 4 % was achieved by a dye-sensitized, nanocrystalline solar cell using (Bu₂MeS)I:I₂ (100:1) as electrolyte (Air Mass 1.5 spectrum at 100 W m^-2), quite compatible with the standard efficiencies provided by organic solvent-containing cells. Several solar cells with iodine-doped metal-iodidebased electrolytes reached stable efficiencies over 2 %. The (Bu₂MeS)I:I₂-containing cells showed better long-term stabilities than the organic solvent-based cells, and provided the fastest electron transports as well as the highest charge accumulation.</p><p>Several polypyridyl-ruthenium complexes were tested as solar cell sensitizers. No general improvements could be observed according to the addition of amphiphilic co-adsorbents to the dyes or nanopartices of titanium dioxide to the electrolytes. For ionic liquid-containing solar cells, a saturation phenomena in the short-circuit current densities emerged at increased light intensities, probably due to inherent material transport limitation within the systems.</p><p>Some iodoargentates and -cuprates were structurally characterized, consisting of monomeric or polymeric entities with anionic networks or layers. A system of metal iodide crownether complexes were employed and tested as electrolytes in photoelectrochemical solar cells, though with poorer results. Also, the crystal structure of a copper-iodide-(12-crown-4) complex has been characterized</p>

Since their commercialization in 1990, the electrodes of the lithium-ion battery have remained fundamentally the same. While energy density improvements have come from reducing the cell packaging, higher capacity electrodes are needed to continue this trend. A lithium metal anode, where the negative electrode half reaction is the plating and stripping of metallic lithium, is explored as an alternative to current graphite anodes. The specific capacity of the lithium metal anode is over ten times that of the graphite anode, making it a serious candidate to further improve the energy density of lithium batteries. Electrodeposited lithium metal forms dendrites, sharp needles that can grow across the separator and short circuit the battery. Thus, a chief goal is to alter lithium’s plating morphology. This was achieved in two separate ionic liquid electrolytes by co-depositing lithium with sodium. The co-deposited sodium is thought to block dendritic sites, leading to a granular deposit. A nucleation study confirmed that metal deposits from the ionic liquid electrolyte containing sodium, prevented dendritic growth from nucleation on, and not after dendrites had already grown. A model based on the geometry of the nuclei was used to gain insight into the effect of the solid electrolyte interface (SEI) that forms on freshly deposited lithium metal. In addition to sodium, the effect of alkaline earth metals on the lithium deposit morphology was also explored. While these metals did not deposit from the ionic liquid electrolyte, their addition also resulted in granular, dendrite free, deposits. The alkaline earth additives generally increased the overpotential for nucleating on the substrate and lowered the current density achievable. Strontium and barium showed the least of these negative effects while still providing a dendrite free deposit. A second hurdle for lithium metal anodes is the instability between the electrolyte and lithium metal. A protective SEI layer that prevents undesired side reactions is difficult to form because of the large volume change associated with cycling. Formation of a better SEI on lithium metal was attempted through the addition vinylene carbonate, which greatly improved the coulombic efficiency of lithium metal plating and stripping. The effect of gases, such as oxygen, nitrogen and carbon dioxide, on the SEI layer was also investigated. It was found that the presence of nitrogen and oxygen improved the coulombic efficiency by facilitating a thinner SEI layer. This work presents attempts at improving the lithium metal anode both by increasing the coulombic efficiency of the redox process and by eliminating dendrite growth. The coulombic efficiency was improved through the bubbling of gases and addition of organic additives but work remains to increase this value further. Dendritic growth, which poses a safety hazard, was completely eliminated by two methods: 1) co-deposition and 2) adsorption of a foreign metal. Both methods could potentially be applied to different electrolytes, making them promising methods for preventing dendritic growth in future lithium metal anodes.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第19090号 / エネ博第314号 / 新制||エネ||64 / 32041 / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 萩原 理加, 教授 佐川 尚, 教授 野平 俊之 / 学位規則第4条第1項該当

In order to reduce the amount of pollution that is generated by burning fossil fuels alternative energy sources should be explored. Hydrogen has been identified as the most promising replacement for fossil fuels and can be produced by using the Hybrid Sulphur (HyS) cycle. Currently the SO2/O2 separation step in the HyS process has a large amount of knock out drums. The aim of this study was to investigate new technology to separate the SO2 and O2. The technology that was identified and investigated was to separate the SO2 and O2 by absorbing the SO2 into an ionic liquid. In this study the maximum absorption, absorption rate and desorption rate of SO2 from the ionic liquid [BMIm][MeSO4] with purities of 95% and 98% was investigated. These ionic liquid properties were investigated for pure O2 at pressures ranging from 1.5 to 9 bar(a) and for pure SO2 at pressures from 1.5 to 3 bar(a) at ambient temperature. Experiments were also carried out where the composition of the feed-stream to the ionic liquid was varied with compositions of 0, 25, 50, 75 and 100 mol% SO2 with O2 as the balance. For each of these compositions the temperature of the ionic liquid was changed from 30oC to 60oC, in increments of 10oC. The absorption rate of SO2 in the ionic liquid increased when the mole percentage SO2 in the feed stream was increased. When the temperature of the ionic liquid was decreased the maximum amount of SO2 that the ionic liquid absorbed increased dramatically. However, the absorption rate was not influenced by a change in the absorption temperature. The experimental results for the maximum SO2 absorption were modelled with the Langmuir absorption model. The model fitted the data well, with an average standard deviation of 17.07% over all the experiments. In order to determine if the absorption reaction was endothermic or exothermic the Clausius-Clapeyron equation was used to calculate the heat of desorption for the desorption step. The heat of desorption data indicated that the desorption of SO2 from this ionic liquid was an endothermic reaction because the heat of desorption values was positive. Therefore the absorption reaction was exothermic. From the pressure-change experiments the results showed that the mole percentage of O2 gas that was absorbed into the ionic liquid was independent of the pressure of the O2 feed.On the other hand, there was a clear correlation between the mole percentage SO2 that was absorbed into the ionic liquid and the feed pressure of the SO2. When the feed pressure of the SO2 was increased the amount of SO2 absorbed also increased, this trend was explained with Fick’s law. In the study the effect of the ionic liquid purity on the SO2 absorption capacity was investigated. The experimental results for the pressure experiments showed that the 95% and 98% pure ionic liquid absorbed about the same amount of SO2. During the temperature experiments the 95% pure ionic liquid absorbed more SO2 than the 98% pure ionic liquid for all but two of the experiments. However the 95% pure ionic liquid also absorbed small amounts of O2 at 30 and 40oC which indicated that the 95% pure ionic liquid had a lower selectivity than the 98% pure ionic liquid. Therefore, the 95% pure ionic liquid had better SO2 absorption capabilities than the 98% pure ionic liquid. These result showed that the 98% pure ionic liquid did not absorb more SO2 than the 95% pure ionic liquid, but it did, however, show that the 98% pure ionic liquid had a better selectivity towards the SO2. Hence, it can be concluded that even with the O2 that is absorbed it would be economically more advantageous to use the less expensive 95% pure ionic liquid rather than the expensive 98% pure ionic liquid, because the O2 would not influence the performance of the process negatively in such low quantities. / Thesis (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013

In order to reduce the amount of pollution that is generated by burning fossil fuels alternative energy sources should be explored. Hydrogen has been identified as the most promising replacement for fossil fuels and can be produced by using the Hybrid Sulphur (HyS) cycle. Currently the SO2/O2 separation step in the HyS process has a large amount of knock out drums. The aim of this study was to investigate new technology to separate the SO2 and O2. The technology that was identified and investigated was to separate the SO2 and O2 by absorbing the SO2 into an ionic liquid. In this study the maximum absorption, absorption rate and desorption rate of SO2 from the ionic liquid [BMIm][MeSO4] with purities of 95% and 98% was investigated. These ionic liquid properties were investigated for pure O2 at pressures ranging from 1.5 to 9 bar(a) and for pure SO2 at pressures from 1.5 to 3 bar(a) at ambient temperature. Experiments were also carried out where the composition of the feed-stream to the ionic liquid was varied with compositions of 0, 25, 50, 75 and 100 mol% SO2 with O2 as the balance. For each of these compositions the temperature of the ionic liquid was changed from 30oC to 60oC, in increments of 10oC. The absorption rate of SO2 in the ionic liquid increased when the mole percentage SO2 in the feed stream was increased. When the temperature of the ionic liquid was decreased the maximum amount of SO2 that the ionic liquid absorbed increased dramatically. However, the absorption rate was not influenced by a change in the absorption temperature. The experimental results for the maximum SO2 absorption were modelled with the Langmuir absorption model. The model fitted the data well, with an average standard deviation of 17.07% over all the experiments. In order to determine if the absorption reaction was endothermic or exothermic the Clausius-Clapeyron equation was used to calculate the heat of desorption for the desorption step. The heat of desorption data indicated that the desorption of SO2 from this ionic liquid was an endothermic reaction because the heat of desorption values was positive. Therefore the absorption reaction was exothermic. From the pressure-change experiments the results showed that the mole percentage of O2 gas that was absorbed into the ionic liquid was independent of the pressure of the O2 feed.On the other hand, there was a clear correlation between the mole percentage SO2 that was absorbed into the ionic liquid and the feed pressure of the SO2. When the feed pressure of the SO2 was increased the amount of SO2 absorbed also increased, this trend was explained with Fick’s law. In the study the effect of the ionic liquid purity on the SO2 absorption capacity was investigated. The experimental results for the pressure experiments showed that the 95% and 98% pure ionic liquid absorbed about the same amount of SO2. During the temperature experiments the 95% pure ionic liquid absorbed more SO2 than the 98% pure ionic liquid for all but two of the experiments. However the 95% pure ionic liquid also absorbed small amounts of O2 at 30 and 40oC which indicated that the 95% pure ionic liquid had a lower selectivity than the 98% pure ionic liquid. Therefore, the 95% pure ionic liquid had better SO2 absorption capabilities than the 98% pure ionic liquid. These result showed that the 98% pure ionic liquid did not absorb more SO2 than the 95% pure ionic liquid, but it did, however, show that the 98% pure ionic liquid had a better selectivity towards the SO2. Hence, it can be concluded that even with the O2 that is absorbed it would be economically more advantageous to use the less expensive 95% pure ionic liquid rather than the expensive 98% pure ionic liquid, because the O2 would not influence the performance of the process negatively in such low quantities. / Thesis (MIng (Chemical Engineering))--North-West University, Potchefstroom Campus, 2013