O aumento no consumo energético e a crescente preocupação ambiental frente à emissão de gases poluentes criam um apelo mundial favorável para pesquisas de novas tecnologias não poluentes de fontes de energia. Baterias recarregáveis de lítio-ar em solventes não aquosos possuem uma alta densidade de energia teórica (5200 Wh kg-1), o que as tornam promissoras para aplicação em dispositivos estacionários e em veículos elétricos. Entretanto, muitos problemas relacionados ao cátodo necessitam ser contornados para permitir a aplicação desta tecnologia, por exemplo, a baixa reversibilidade das reações, baixa potência e instabilidades dos materiais empregados nos eletrodos e dos solventes eletrolíticos. Assim, neste trabalho um modelo cinético foi empregado para os dados experimentais de espectroscopia de impedância eletroquímica, para a obtenção das constantes cinéticas das etapas elementares do mecanismo da reação de redução de oxigênio (RRO), o que permitiu investigar a influência de parâmetros como o tipo e tamanho de partícula do eletrocatalisador, o papel do solvente utilizado na RRO e compreender melhor as reações ocorridas no cátodo dessa bateria. A investigação inicial se deu com a utilização de sistemas menos complexos como uma folha de platina ou eletrodo de carbono vítreo como eletrodos de trabalho em 1,2-dimetoxietano (DME)/perclorato de lítio (LiClO4). A seguir, sistemas complexos com a presença de nanopartículas de carbono favoreceu o processo de adsorção das moléculas de oxigênio e aumentou ligeiramente (uma ordem de magnitude) a etapa de formação de superóxido de lítio (etapa determinante de reação) quando comparada com os eletrodos de platina e carbono vítreo, atribuída à presença dos grupos laterais mediando à transferência eletrônica para as moléculas de oxigênio. No entanto, foi observada uma rápida passivação da superfície eletrocatalítica através da formação de filmes finos de Li2O2 e Li2CO3 aumentando o sobrepotencial da bateria durante a carga (diferença de potencial entre a carga e descarga > 1 V). Adicionalmente, a incorporação das nanopartículas de platina (Ptnp), ao invés da folha de platina, resultou no aumento da constante cinética da etapa determinante da reação em duas ordens de magnitude, o qual pode ser atribuído a uma mudança das propriedades eletrônicas na banda d metálica em função do tamanho nanométrico das partículas, e estas modificações contribuíram para uma melhor eficiência energética quando comparado ao sistema sem a presença de eletrocatalisador. Entretanto, as Ptnp se mostraram não específicas para a RRO, catalisando as reações de degradação do solvente eletrolítico e diminuindo rapidamente a eficiência energética do dispositivo prático, devido ao acúmulo de material no eletrodo. O emprego de líquido iônico como solvente eletrolítico, ao invés de DME, promoveu uma maior estabilização do intermediário superóxido formado na primeira etapa de transferência eletrônica, devido à interação com os cátions do líquido iônico em solução, o qual resultou em um valor de constante cinética da formação do superóxido de três ordens de magnitude maior que o obtido com o mesmo eletrodo de carbono vítreo em DME, além de diminuir as reações de degradação do solvente. Estes fatores podem contribuir para uma maior potência e ciclabilidade da bateria de lítio-ar operando com líquidos iônicos. / The increasing in energetic consumption and environmental concerning toward rising in the emission of pollutant gases create a favorable scenario to develop non-pollutant technologies and more efficient energy storages. Rechargeable non-aqueous lithium-air batteries possess high theoretical energy density (5200 Wh kg-1), characterizing as a promising system to stationary and electric vehicles applications. However, many issues on the cathode electrode should be addressed to enable this technology, for example, low reversibility of the reactions, low rate-capability and instabilities issues from cathode materials and electrolytic solvents. Here, a kinetic model was employed for modulate the experimental impedance data in order to obtain the rate constants of elementary steps from oxygen reduction reaction (ORR), which allows the investigation of the role of some parameters such as, type and grain size of electrocatalysts, and the solvent influence. The initial investigation were with less complexes systems of platinum bulk or glassy carbon as the working electrode in 1,2-dimethoxyethane (DME)/lithium perchlorate (LiClO4). Based on that, the role of carbon nanoparticles in the ORR was an increasing the oxygen adsorption process, and by slightly increasing (one order of magnitude) the superoxide formation (rate determining step) as when compared with platinum and glassy carbon electrodes due to the presence of side groups acting as mediators to the electron transfer. Nonetheless, a fast surface passivation was observed in function of Li2O2 and Li2CO3 thin films formations, and these films increase the battery overpotential during the charge process (potential difference between charge/discharge >1V). In addition, dispersed platinum nanoparticles (Ptnp) resulted in an increase of two orders of magnitude on the rate constant of the rate determining step when compared to platinum bulk. This can be explained due to changes in electronic properties of metallic d-bands in function of nanometric size. These changes contributed to enhance the energetic efficiency of the practical device when compared to the non-catalyzed system. However, the Ptnp were non-specific toward the ORR catalyzing the electrolyte degradation reactions, and decreasing the energy efficiency faster than the non-catalyzed system. The ionic liquid rather than DME promoted better stabilization process for intermediary superoxide due to interaction between cations present in solution, resulting in an outstanding enhancement of the rate constant for rate determining step (three orders of magnitude) when compared to the same working electrode in DME. In addition, decrease the electrolyte degradation reaction. These factors can improve a higher rate-capability and cycle life of the practical lithium-air batteries.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-10-10T14:17:08Z No. of bitstreams: 1 Dissertac?a?o mestrado_rafa p?s banca - final.pdf: 6925259 bytes, checksum: 04c8ab3a00fa276e3a89008c46ce0d72 (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-10-16T16:50:44Z (GMT) No. of bitstreams: 1 Dissertac?a?o mestrado_rafa p?s banca - final.pdf: 6925259 bytes, checksum: 04c8ab3a00fa276e3a89008c46ce0d72 (MD5) / Made available in DSpace on 2018-10-16T16:55:39Z (GMT). No. of bitstreams: 1 Dissertac?a?o mestrado_rafa p?s banca - final.pdf: 6925259 bytes, checksum: 04c8ab3a00fa276e3a89008c46ce0d72 (MD5) Previous issue date: 2018-03-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Ionic liquids (ILs) grafting in inorganic solids sorbents is a promising alternative to replace the usual separation process of carbon dioxide from natural gas currently performed using amines. ILs presents unique properties such as, low environmental impact, non-corrosion and process efficiency. The ILs 1,3-bis(3-trimethoxysilylpropyl)imidazolium chloride and 1-methyl-3-(3-trimethoxysilylpropyl)imidazolium chloride were immobilized in MCM-41 and MCMRH silica. The MCMRH was synthesized from rice husk. ILs chemical immobilization was carried out by grafting method, where covalent bonds are formed between silane and hydroxyl groups present in the support. Syntheses were carried out in toluene under nitrogen atmosphere to prevent the hydrolysis and condensation of methoxy groups in the silane structure. CO2 sorption capacity and selectivity for CO2/CH4 were evaluated after synthesis. ILs in concentrations of 10 and 20% were tested. The samples characterization by XPS, NMR, FTIR and TGA confirmed the formation of the proposed IL structures. Sorption and selectivity results showed that the immobilization reduces the CO2sorption capacity, however the selectivity of the materials was higher in relation to the pristine silica. Supports immobilized with ILs 1-methyl-3- (3-trimethoxysilylpropyl) imidazole chloride presented better performance. The observed selectivity increase was 25% when 10% of IL was supported on MCMRH silica. / A imobiliza??o de l?quidos i?nicos ? LIs em suportes inorg?nicos ? uma alternativa ao uso de aminas no processo de separa??o e captura do di?xido de carbono contido no g?s natural, pois possui vantagens ligadas ao aumento de vida ?til de equipamentos, efici?ncia de processo e impacto ambiental. Os LIs cloreto de 1,3-bis(3-trimetoxisililpropil)imidazol e cloreto de 1-metil-3-(3-trimetoxisililpropil)imidazol foram imobilizados na s?lica comercial MCM-41 e na s?lica sintetizada a partir da casca de arroz nomeada neste trabalho como MCMRH. A imobiliza??o qu?mica dos LIs foi realizada atrav?s da forma??o de liga??es covalentes entre grupos silanos na estrutura do l?quido i?nico e grupos hidroxila presentes nos suportes. As s?nteses foram realizadas em tolueno sob condi??es inertes para controle da hidr?lise e condensa??o de grupos metoxi na estrutura dos silanos. Ap?s a sua s?ntese, os suportes imobilizados com LIs tiveram sua capacidade de sor??o de CO2 e seletividade em rela??o a CO2/CH4 avaliadas. LIs em concentra??es de 20 e 10% foram testadas. A caracteriza??o das amostras por XPS, RMN, FTIR e TGA confirmaram a forma??o das estruturas dos LIs propostos e os resultados de sor??o e seletividade mostraram que a imobiliza??o reduz a capacidade de sor??o em rela??o ao CO2, entretanto a seletividade dos materiais foram maiores em rela??o aos suportes antes da imobiliza??o. Os suportes imobilizados com o LIs cloreto de 1-metil-3-(3-trimetoxisililpropil)imidazol tiveram melhor desempenho em rela??o aos demais, o aumento de seletividade observado foi de 25% no melhor caso, onde 10% de LI foi suportado na s?lica MCMRH.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-12-03T15:52:09Z No. of bitstreams: 1 Dissertacao DANIELA MAFFI RODRIGUES.pdf: 1641622 bytes, checksum: 7201a3a551a602c84d3776d0f02f7399 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-12-05T13:35:48Z (GMT) No. of bitstreams: 1 Dissertacao DANIELA MAFFI RODRIGUES.pdf: 1641622 bytes, checksum: 7201a3a551a602c84d3776d0f02f7399 (MD5) / Made available in DSpace on 2018-12-05T13:50:46Z (GMT). No. of bitstreams: 1 Dissertacao DANIELA MAFFI RODRIGUES.pdf: 1641622 bytes, checksum: 7201a3a551a602c84d3776d0f02f7399 (MD5) Previous issue date: 2018-07-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Carbon capture and storage (CCS) and carbon capture and utilisation(CCU) technologies has been pointed out as possibilities to mitigate the effects caused by the massiverelease of CO2 into the atmosphere. The use of CO2 in cycloaddition reactions toepoxides obtaining cyclic carbonates is an interesting possibility to reduce CO2emission. Cyclic carbonates are products of great applicability as solvents in the chemical industry and are used as raw material for a wide range of products. Meanwhile, the use of CO2 for a cycloaddition reaction requires a large amount of energy being necessary the use of catalysts in order to optimize such reactions. Poly (ionic liquids) (PIL) are alternative catalysts due its selective, recyclability and conversion. In this work, cellulosic poly(ionic liquids) (CPIL) obtained from rice husk were testedas heterogeneous catalyst. Cellulose extraction was carried out by chemical method. A chemical modification of the cellulose fibers was carried out by the treatment with citric acid and functionalization with 3 mmol of the ionic liquids BMIM Cl, TBAB, TBPB and BMPYRR to form CPIL-BMIM, CPIL-TBA, CPIL-TBP and CPIL-BMPYRR), without addition of solvents. Cyclo addition reactions were carried out with propylene and styrene oxides with different CO2 pressures(25, 30 and 40 bar) and temperatures (90, 110 and 120 ?C) for 6 h. The obtained product was characterized by gas chromatography (GC), Fourier Transform Infrared Spectroscopy(FTIR)and Nuclear Magnetic Resonance (1H NMR). The results showed better yields for CPIL-TBP and CPIL-TBA, whose values were 53.2% and 39% respectively for propylene carbonate and 67.3% for styrene carbonate using CPIL-TBP. When the ZnBr2 cocatalyst was used, there was an increase in the catalytic activity of these catalysts. For CPIL-TBP the yields were 71.4% for propylene carbonate and 78.7% for styrene carbonate. For CPIL-TBA the increase in propylene carbonate yield was 67.7%. / O uso das tecnologias de captura e armazenamento de carbono (CCS) e de captura utiliza??o do carbono (CCU) v?m sendo apontadas como possibilidades para mitigar os efeitos causados pela libera??o deliberada de elevadas concentra??es de CO2 na atmosfera. A utiliza??o do CO2 em rea??es de cicloadi??o em ep?xidos para obter carbonatos c?clicos vem se mostrando uma possibilidade interessante para reduzir a emiss?o de CO2 na atmosfera. Os carbonatos c?clicos s?o produtos de grande aplicabilidade como solventes na ind?stria qu?mica e s?o utilizados como mat?ria prima para uma vasta gama de produtos. Entretanto, o CO2 apresenta baixa reatividade tornando-se necess?rio o uso de catalisadores para otimizar tais rea??es. Os poli(l?quidos i?nicos) (PILs) v?m se mostrando como poss?veis catalisadores alternativos, demonstrando-se seletivos, recicl?veis e gerando consider?vel convers?o. Neste trabalho foram testados poli(l?quidos i?nicos) celul?sicos (CPIL), obtidos a partir da casca do arroz, como catalisador heterog?neo. A extra??o da celulose foi realizada por um m?todo qu?mico. A modifica??o qu?mica das fibras de celulose foi realizada a partir do tratamento com ?cido c?trico e a funcionaliza??o desta com 3 mmol dos l?quidos i?nicos BMIM Cl, TBAB, TBPB e BMPYRR formando CPIL-BMIM, CPIL-TBA, CPIL-TBP e CPIL-BMPYRR. As rea??es de cicloadi??o foram realizadas com os ?xidos de propileno e estireno com diferentes press?es de CO2 (15, 25, 30 e 40 bar) e temperaturas (90, 110, 120 e 130?C) durante (3, 6 e 9h), todas as rea??es foram realizadas sem a utiliza??o de solventes. O produto obtido foi caracterizado por cromatografia gasosa (CG) , espectroscopia de infravermelho com transformada de Fourier (FTIR) e Resson?ncia Magn?tica Nuclear (1H RMN). Os resultados demonstraram melhores rendimentos para CPIL-TBP e CPIL-TBA, cujos valores foram de 53,2% e 39% respectivamente para o carbonato de propileno e de 67,3% para o carbonato de estireno utilizando o CPIL-TBP. Quando o cocatalisador ZnBr2 foi utilizado, houve um aumento na a atividade catal?tica destes catalisadores, para o CPIL-TBP os rendimentos foram de 71,4 % para o carbonato de propileno e 78,7% para o carbonato de estireno. Para o CPIL-TBA o aumento no rendimento de carbonato de propileno foi de 67,7%.

Les supercondensateurs sont des dispositifs de stockage de l'énergie électrique particulièrement intéressants pour les applications de puissance. Les rendre flexibles permet de considérer de nouvelles possibilités d'intégration. Néanmoins, l'optimisation de la densité d'énergie, point faible de ces dispositifs, passe par la recherche et l'étude de nouveaux matériaux d'électrode et d'électrolytes. Dans ce but, ce travail de thèse s'est orienté vers des matériaux pseudo-capacitifs, avec l'utilisation d'électrodes à base de MnO2, et d'électrolytes à base de liquide ionique fonctionnalisé de type biredox. Afin de conserver le caractère flexible des électrodes, le dioxyde de manganèse a d'abord été synthétisé pour la formulation d'encres à pulvériser sur substrat flexible. A cette occasion, l'influence de dispersants sur les performances a été étudiée. Les performances de matériaux nanocomposites à base de fibres de carbone et de graphène décorés par MnO2 ont ensuite été évaluées. Les contributions faradiques et surfaciques à la capacité développée par MnO2 ont ensuite été déterminées par une étude électrochimique fine. Enfin, l'étude d'un nouveau liquide ionique fonctionnalisé utilisé dans un dispositif carbone/carbone a confirmé l'attractivité de ces phénomènes faradiques dans les performances électrochimiques d'un supercondensateur. / Supercapacitors are attractive electrical energy storage devices for power applications. As flexible devices new integration opportunities can be consider. Nevertheless, the optimization of the energy density, weak point of these devices, proceeds through the search and the study of new electrode materials and electrolytes. In this aim, this thesis work is turned towards so called pseudo-capacitive materials, with the use of MnO2-based electrodes, and biredox Ionic Liquid electrolytes. To preserve the flexible behavior of the electrodes, the manganese dioxide was, at first, synthesized for the formulation of an ink to be sprayed on flexible substrates. The influence of dispersing agents on the electrochemical performances was evaluated. Performances of nanocomposite materials prepared with carbon nanofibers and graphene oxide sheets were also studied. Faradaic and surface contributions to the capacity developed by MnO2 electrode material were then determined by an advanced electrochemical study. Finally, the study of a new Ionic Liquid used in a symmetrical carbon/carbon supercapacitor confirmed the attractiveness of these Faradaic phenomena for the enhancement of the supercapacitor electrochemical performances.

The demand for electric vehicles is increasing rapidly as the world is preparing for a fossil fuel-free future in the automotive field. Lithium battery technologies are the most effective options to replace fossil fuels due to their higher energy densities. However, safety remains a major concern in using lithium as the anode, and the development of non-volatile, non-flammable, high conductivity electrolytes is of great importance. In this dissertation, a gel polymer electrolyte (GPE) consisting of ionic liquid, lithium salt, and a polymer has been developed for their application in lithium batteries. A comparative study between GPE and ionic liquid electrolyte (ILE) containing batteries shows a superior cyclic performance up to 5C rate and a better rate capability for 40 cycles for cells with GPE at room temperature. The improvement is attributed to GPE’s improved stability voltage window against lithium as well as higher lithium transference number. The performance of the GPE in lithium-sulfur battery system using sulfur-CNT cathodes shows superior rate capability for the GPE versus ILE for up to 1C rates. Also, GPE containing batteries had higher capacity retention versus ILE when cycled for 500 cycles vii at C/2 rate. Electrochemical impedance spectroscopy (EIS) studies reveal interfacial impedances for ILE containing batteries grew faster than in GPE batteries. The accumulation of insoluble Li2S2/Li2S on the electrodes decreases the active material thus contributes to capacity fading. SEM imaging of cycled cathodes reveals cracks on the surface of cathode recovered from ILE batteries. On the other hand, the improved electrochemical performance of GPE batteries indicates better and more stable passivation layer formation on the surface of the electrodes. Composite GPE (cGPE) containing micro glass fillers were studied to determine their electrochemical performance in Li batteries. GPE with 1 wt% micro fillers show superior rate capability for up to 7C and also cyclic stability for 300 cycles at C/2 rate. In situ, EIS also reveals a rapid increase in charge transfer resistance in GPE batteries, responsible for lowering the capacity during cycling. Improved ion transport properties due to ion-complex formations in the presence of the micro fillers, is evidenced by improved lithium transference number, ionic conduction, and ion-pair dissociation detected using Raman spectroscopy.

Smältkarbonatbränslecellen (MCFC) är en högtemperaturbränslecell för stationära applikationer. Den har samma höga totalverkningsgrad som konventionella kraftvärme-anläggningar, men kan byggas i mindre moduler (från 250 kWe). De små modulerna och den bränsleflexibilitet (naturgas, biogas, etanol, diesel) som MCFC har, gör den intressant för exempelvis industrier med organiska restprodukter och höga krav på tillförlitlighet. Den höga temperaturen och närvaron av en saltsmälta gör dock materialdegradering till en viktig faktor för forskning och utveckling inom området. För även om de fälttester som nyligen gjorts har visat på att vissa av degraderingsprocesserna är mindre allvarliga än förväntat, finns fortfarande ett behov av utveckling för att sänka kostnaderna och förlänga livstiden. I första delen av detta arbete undersöktes material för olika delar av cellen inom ramarna för EU-projektet IRMATECH. Materialen ansågs vara interessanta alternativ till de nuvarande materialen på grund av deras lägre kostnad och/eller bättre prestanda. Två alternativa anodströmtilledarmaterial undersöktes. För anodströmtilledaren är korrosionen och den elektriska resistansen av det eventuella oxidlagret nyckelparametrar. Dessa parametrar undersöktes och utvärderades. Fastän de båda alternativa materialen hade oxidlager med låg resistans, fanns indikationer på korrosionsprocesser som kan äventyra materialets långtidsstabilitet. För katodmaterialet, NiO, har upplösningen varit problemet. De upplösta nickeljonerna fälls ut i elektrolyten och bildar dendriter som kan kortsluta cellen. Därför undersöktes nickelupplösningen hos tre alternativa katodmaterial. Det mest lovande materialet, en nickeloxid-katod dopad med magnesium och järn testades i en singelcell för att studera elektrokemisk prestanda, morfologi och områden där nickelutfällning skett. Resultaten visade att prestandan var jämförbar med NiO, men att den mekaniska stabiliteten måste undersökas ytterligare. I ”wet-seal”-området är det rostfria stålet belagt med ett aluminiumskikt för att skydda det från den mycket korrosiva miljön. Tillverkningsprocesserna för dessa aluminiumbeläggningar har hittills varit dyra och komplexa. Därför utvärderades en alternativ tillverkningsprocess. Beläggningen, studerad i både reducerande och oxiderande miljö visade en tendens till att spricka och därmed exponera det underliggande rostfria stålet. Detta berodde troligtvis på en manuell beläggningsprocess som resulterade i ett inhomogent ytskikt. I den andra delen av arbetet föreslogs en alternativ tillverkningsmetod, baserad på nyligen publicerade resultat där man elektrodeponerat aluminium från jonvätskor. Dessa har ett större katodiskt fönster än vatten och möjliggör därför elektrodeponering av elektropositiva material. För att göra processen industrivänlig provades ett alternativ till den vanligen använda aluminiumtrikloriden. Det visade sig dock att påverkan av miljön på stabiliteten hos jonvätskan behövde undersökas innan några material kunde tillverkas. Vatten i kombination med syre visade sig ha en stor inverkan på den katodiska strömtätheten. I frånvaro av dessa komponenter var jonvätskan mycket stabil. / The Molten Carbonate Fuel Cell (MCFC) is a high temperature fuel cell for stationary applications. It has the same high over-all efficiency (90%) as traditional combined heat and power plants, but MCFC can be built in small modules (from 250 kWe). The small modules in combination with fuel flexibility (natural gas, biogas, ethanol, diesel) makes MCFC an interesting alternative for industries with organic waste and high demands for reliability. The high temperature (650 °C) and the presence of molten salt result however in material degradation. Corrosion and dissolution of the materials used have been the challenge for MCFC. Although long-term field trials have shown that some of the material problems are not as severe as first believed, further material development is necessary to decrease the cost and prolong the life-time. In the first part of this work, materials for different parts of the cell were tested within the EU project IRMATECH. The materials were interesting alternatives to the state-of-the-art materials due to their lower cost and/or better performance. Two alternative anode current collector materials were tested. For the anode current collector the corrosion and electrical resistance of the possible oxide layer are key parameters. These parameters were investigated and evaluated. Although both the materials showed a low resistance, there were indications of corrosion processes which could affect the life-time of the material. For the cathode material, NiO, the dissolution of the material has been a problem. The dissolved nickel ions precipitate in the electrolyte and form conductive nickel dendrites that eventually short-circuit the cell. Therefore, the nickel dissolution of three alternative cathode materials was tested. The most promising material, a NiO doped with magnesium and iron, was tested in a single cell to study the electrical performance, the morphology after operation and the area where nickel had precipitated. The results showed that the performance was comparable to NiO, but it is necessary to investigate the mechanical strength of the material further. In the wet-seal area, the stainless steel is coated with an aluminium coating to protect the material from a severe corrosion environment. The production of aluminium coatings has so far been expensive and complex and an alternative coating process was evaluated. The alternative coating, tested in both reducing and oxidising environments showed a tendency to crack and expose the stainless steel to the corrosive environment. This was suggested being due to the manual coating process that resulted in inhomogeneous coatings. In the second part, an alternative process to coat the wet-seal was suggested, based on recently published results where aluminium had been electrodeposited from ionic liquids. These solvents have a wider electrochemical window than water, and electropositive materials can therefore be deposited. To make the coating process suitable for industrial applications, an alternative to the commonly used AlCl3 was tested. It was shown however, that the influence of the environment had to be investigated before any materials could be produced. The environment, especially water in combination with oxygen was shown to influence the cathodic current density. In absence of these components, the ionic liquid was shown to be very stable. / QC 20100906

Ce mémoire portant sur le développement de liquides ioniques protiques à l'état liquide à température ambiante en tant qu'électrolytes pour des supercapacités faradiques à base de dioxyde de ruthénium est divisé en trois études distinctes. La première permet d'évaluer quelles propriétés de ces sels fondus doivent être optimisées pour cette application en utilisant les données recueillies avec une série de nouveaux liquides ioniques protiques constitués de l'acide trifluoroacétique et différentes bases hétérocycliques azotées. La seconde discute de l'effet d'impuretés colorées sur les propriétés des liquides ioniques ainsi que sur des aspects pratiques devant être pris en considération lors des synthèses. La troisième traite d'importantes relations structure–propriétés pour une série de liquides ioniques protiques ayant des cations du type pyridinium et différents anions. Dans leur ensemble, les travaux présentés devraient permettre une recherche plus efficace de liquides ioniques avec des propriétés désirables en vue d'application comme électrolyte dans le futur. / This thesis on the development of room temperature protic ionic liquids as electrolytes in ruthenium-dioxide based faradaic superpacitors consists of three separate studies. The first one establishes which properties of molten salts need to be optimized for this application by using the data obtained from the analysis of a series of protic ionic liquids composed of trifluoroacetic acid and N-heterocyclic bases. The second study elaborates on the effect of colored impurities on the properties of ionic liquids and also reports practical aspects which need to be accounted for during their synthesis. The third study focuses on important structure–property relationships for a series of protic ionic liquids with pyridinium cations and various anions. Altogether, the results presented in here should allow a more efficient design of ionic liquids with desirable properties for application as electrolytes in the future.

Les supercapacités hybrides se taillent de plus en plus une place dans le secteur des énergies renouvelables. L’oxyde de manganèse possède certaines caractéristiques (faible coût, caractère écologique et une capacitance spécifique supérieure) qui font de ce dernier un matériau très attirant pour l’assemblage de tels dispositifs. Ce mémoire, divisé en trois parties, propose l’utilisation des liquides ioniques protiques comme électrolytes pour l’assemblage de supercapacités hybrides à base d’oxyde de manganèse et carbone. D’abord, le comportement pseudocapacitif des électrodes à base de films minces d’oxyde de manganèse dans les liquides ioniques protiques ainsi que leurs propriétés optiques sont étudiés et évalués. Des valeurs de capacitance spécifique allant jusqu’à 397 F/g ont été trouvées dans cette partie. Ensuite, des mélanges composés par un solvant organique (acétonitrile) et le liquide ionique protique sont présentés comme une manière de contourner la faible conductivité de ce dernier qui limite les valeurs de capacitance spécifique à obtenir. Une amélioration de la capacitance spécifique d’environ 30% est reportée dans ce chapitre. Finalement, l’assemblage d’une supercapacité hybride est présenté comme une stratégie efficace qui permet l’élargissement de la faible fenêtre de potentiel de travail obtenue avec les électrodes à base d’oxyde de manganèse. De cette façon, la faisabilité de tel arrangement est montré ici, obtenant de valeurs de capacitance spécifique (16 F/g) ainsi que de puissance (81 W/kg) et d’énergie spécifique (1,9 Wh/kg) acceptables en utilisant des liquides ioniques protiques comme électrolytes de remplissage. / Hybrid supercapacitors continue to carve out a place in the field of renewable energies. Manganese dioxide, because of some attractive characteristics (low cost, environmental friendly and high specific capacitance), is a very promising material for the assembly of such devices. This thesis, divided into three chapters, proposes the use of protic ionic liquids as electrolyte for the assembly of a manganese dioxide/carbon based hybrid supercapacitor. Firstly, the pseudocapacitive behaviour and optical properties of thin manganese dioxide based electrodes in protic ionic liquids were investigated and evaluated. Specific capacitance values of up to 397 F/g are reported in this part. Then, mixtures of an organic solvent (acetonitrile) and protic ionic liquids were proposed in order to enhance the poor conductivity of ionic liquids, which limits the specific capacitance values. A 30% improvement of specific capacitance values is shown in this chapter. Finally, the assembly of a hybrid supecapacitor is presented as an alternative strategy to increase the narrow potential window of stability of manganese dioxide electrodes in our protic ionic liquids. The last chapter describes such a device as well as its specific capacitance (16 F/g), energy (1.9 Wh/kg) and power density (81 W/kg) values obtained in protic ionic liquids.

Die effiziente Speicherung von elektrischer Energie im elektrochemischen System des Superkondensators wird realisiert durch die Ausrichtung von Elektrolytionen im elektrischen Feld polarisierter, poröser Kohlenstoffelektroden. Der Energieinhalt und die Leistungscharakteristika der elektrostatischen Zwischenspeicherung von Energie bei Lade- und Entladezeiten von wenigen Sekunden bis zu einigen Minuten wird entscheidend durch die Eigenschaften der zur Ladungsspeicherung genutzten Grenzfläche zwischen dem Elektrodenmaterial und dem Elektrolyten bestimmt. Für die Optimierung des Energieinhaltes und der Leistungscharakteristika von Superkondensatoren durch die rationale Modifizierung dieser Grenzfläche konnten entscheidende Trends herausgearbeitet werden. Durch Einbindung eines pseudokapazitiven Eisenoxids in die spezifische Oberfläche des mesoporösen CMK-3 im Redoxverfahren ist die Darstellung einer neuartigen Nanokompositstruktur möglich. Diese weißt eine dreifach höhere spezifische Kapazität im Vergleich zur nicht-modifizierten Kohlenstoffoberfläche unter Beibehaltung der Strombelastbarkeit der Kohlenstoffmatrix auf. Entscheidend für die Weiterentwicklung von Synthesestrategien und die anwendungsorientierte Optimierung für Nanokompositstrukturen ist deren ausführliche Charakterisierung mittels angepasster Verfahren. Die in dieser Arbeit erstmals zur Analyse von porösen CMK-3 basierten Nanokompositstrukturen verwendeten Methoden der Aufnahme eines Tiefenprofils mittels Auger Elektronen Spektroskopie (DP-AES) und der energiegefilterten Transmissionselektronenmikroskopie (EF-TEM) lieferten die Grundlage zur Weiterentwicklung der rationalen, nanoskaligen Grenzflächenfunktionalisierung. In einem weiteren, stark vereinfachten und effektiveren Verfahren der Schmelzimprägnierung der porösen Matrix mit Nitrathydraten, sowie deren anschließendes Kalzinieren zum Übergangsmetall, respektive pseudokapazitiven Übergangsmetalloxid, konnte eine nochmals optimierte Nanokompositstruktur dargestellt werden. Das entwickelte Verfahren wurde für die Einbettung von Nickel/Nickeloxid und Eisen/Eisenoxid in die Oberfläche des mesoporösen CMK-3 eingesetzt. Ein gesteigerter Energieinhalt, wie auch eine deutlich gesteigerte Stabilität der Kapazität bei hohen Strombelastungen für die resultierenden Elektrodenmaterialien konnte eindeutig nachgewiesen werden. Die signifikante Erhöhung der Leistungscharakteristika ist dabei auf die optimale Kontaktierung des Übergangsmetalloxids durch das Übergangsmetall als Leitfähigkeitsadditiv im Sinne einer Kern-Schale Struktur realisiert. Der für das Nanokomposit C-FeO10 berechnete Kapazitätsverlust von < 11 % bei Erhöhung der spezifischen Stromstärke von 1 A/g auf 10 A/g verdeutlicht die beeindruckende Strombelastbarkeit des Materials. In einem weiteren in dieser Arbeit diskutierten Ansatz zur Steigerung des Energieinhaltes eines Superkondensators wurde auf die Verwendung von Ionischen Flüssigkeiten (IL) als Elektrolyt eingegangen. Die gezielte Darstellung eines oberflächenmodifizierten aus Cabiden gewonnen Kohlenstoffmaterials (CDC) unter Beibehaltung der Textur des porösen Systems ermöglichte die Untersuchung des Einflusses der Oberflächencharakteristika des Elektrodenmaterials auf die Strombelastbarkeit des Energiespeichers. Es konnte klar herausgestellt werden, dass für den vielversprechenden IL-Elektrolyten EMIBF4 eine verminderte Polarität, sowie die Abwesenheit azider Protonen an der Oberfläche des Kohlenstoffs deutlich zur Steigerung der Strombelastbarkeit des Speichers beiträgt. Realisiert wurde die Modifizierung der Oberfläche durch deren Chlorierung. Die Einordnung der vielversprechenden Kombinationen aus maßgeschneiderten Elektrodenmaterialien und Elektrolytsystemen wurde anhand der Kenngrößen im Ragone-Diagramm vorgenommen. Die Ergebnisse der Arbeit reihen sich in die derzeit schnell voranschreitende Technologieentwicklung bei Superkondensatoren ein.

Τα ιοντικά υγρά (ΙΥ) έχουν κερδίσει το ενδιαφέρον των ερευνητών, λόγω των εξαιρετικών ιδιοτήτων τους σε εφαρμογές κατάλυσης, ηλεκτροχημείας, σύνθεσης και αναλυτικής χημείας καθώς και σε μεθόδους διαχωρισμού. Πρόκειται για ιοντικές ενώσεις που αποτελούνται από οργανικά κατιόντα και οργανικά/ανόργανα ανιόντα, τα οποία εμφανίζουν χαμηλό σημείο τήξης Τm<100oC. Η δομή και οι αλληλεπιδράσεις μεταξύ των ιοντικών υγρών καθορίζουν τις φυσικοχημικές τους ιδιότητες όπως είναι το χαμηλό σημείο τήξης, το χαμηλό ιξώδες, η χαμηλή τάση ατμών, η υψηλή αγωγιμότητα, η μη αναφλεξιμότητα αλλά και η δυνατότητα ανακύκλωσης. Η κατανόηση των διαμοριακών αλληλεπιδράσεων που λαμβάνουν χώρα σε αυτές τις δομές είναι απαραίτητη για την πρόβλεψη αλλά και τη σχεδίαση των ιδιοτήτων τους. Για να κατανοηθεί η δομή και οι αλληλεπιδράσεις στην υγρή φάση, στην παρούσα εργασία, μελετήθηκαν πρωτονιωμένα ιοντικά υγρά (ΠΙΥ) HCnImNTf2 (n=0-12) καθώς επίσης και τα τήγματα των αλκαλικών αλάτων ΜNTf2 (Μ:Li-Cs). Επίσης παρουσιάζεται o εγκλωβισμός τους σε μικροπορώδη υλικά για εφαρμογή τους σε κελιά καυσίμου. Κύριο χαρακτηριστικό των πρωτονιωμένων ιοντικών υγρών είναι ότι πέραν των ηλεκτροστατικών δυνάμεων που αναπτύσσονται μεταξύ τους, τα ανιόντα και τα κατιόντα συνδέονται και με ισχυρούς δεσμούς υδρογόνου. Στα συστήματα αυτά μελετήθηκε η επίδραση της θερμοκρασίας στη δομή τους με χρήση δονητικής φασματοσκοπίας FT-IR και FT-Raman καθώς και με διαφορική θερμιδομετρία σάρωσης. Από τη συγκεκριμένη μελέτη προέκυψε ότι στα συγκεκριμένα ιοντικά υγρά εμφανίζονται ηλεκτροστατικές και van der Waals αλληλεπιδράσεις, δεσμοί υδρογόνου καθώς και π-π αλληλεπιδράσεις. Επίσης διαπιστώθηκε ότι η αύξηση της θερμοκρασίας ευνοεί τη cis ισομέρεια του ανιόντος. Αντίθετα, στα τήγματα των αλάτων MNTf2 (Li-Cs) το ανιόν προτιμά την trans διαμόρφωση. Επίσης η μελέτη της επίδρασης του κατιόντος μελετώντας την επίδραση του κατιόντος στη δομή του ανιόντος οδήγησε στο συμπέρασμα ότι το ανιόν μπορεί να χρησιμοποιηθεί ως εσωτερικός δείκτης των αλληλεπιδράσεων που λαμβάνουν χώρα στα ΙΥ. Κατά τη μελέτη των σύνθετων υλικών βρέθηκε ότι κατά την εισαγωγή του ιοντικού υγρού στους ζεόλιθους λαμβάνει χώρα ιονανταλλαγή μεταξύ του κατιόντος του HMIm+του ΠΙΥ και των κατιόντων Na+του ζεόλιθου. Επίσης, παρουσιάστηκε αύξηση της ιοντικής τους αγωγιμότητας σχεδόν τέσσερις φορές, σε σχέση με την αγωγιμότητα της άνυδρης κατάστασης των κρυστάλλων του ζεόλιθου. / Ionic liquids (ILs) have received considerable attention due to their unique properties in applications in catalysis, electrochemistry, synthesis, analytical chemistry, and separations. They consist of organic cations and organic or inorganic anions and have melting points less than 100oC. Their interesting properties such as low melting points, extremely low vapor pressures, low viscosity, high electrochemical window, no flammability and the ability of being recycled depend on the intermolecular and inter-ionic interactions. Understanding how these interactions are affected by the IL cation alkyl substituents is of paramount importance in order to understand how the IL structure influences macroscopically measured properties and eventually design ILs with desired properties by tailoring their structure. The main interactions of between the PIL ions are Coulombic, van der Waals and hydrogen bonding. In order to understand the effect of these forces to their properties, I examined the effect of alkyl length chain and temperature on the structure of Protic Ionic Liquids (PILs) HCnImNTf2 (n=0-12) using vibrational spectroscopy (FT-Raman and FT-IR/ATR) and differential scanning calorimetry (DSC). A similar study was also carried to the alkali molten salts ANTf2 (A:Li-Cs). Finally the encapsulation of HC1ImNTf2 in zeolites was studied. The goal of this study was to increase the crystal conductivity to level that makes them suitable for PEM fuel cell applications. According to these studies, it was found that the ions interactive long range electrostatic interactions, van der Waals interaction, hydrogen bonds and pi-pi stacking interactions. Moreover, it was found that in PILs the cis conformation of the anion is favored with increasing temperatures, whereas, in case of alkaline molten salts MNTf2 (Li-Cs), trans conformation is dominant in the liquid state. Since the population of the two isomers is affected by the local environment of the anion it was concluded that the anion NTf2- can be used as an indirect mean of the interactions that occur in these systems. Finally, from the encapsulation of protic ionic liquid HMImNTf2 into the porosity of zeolite material, it was found that an ion exchange procedure take place between the cation HMIm+ of the ionic liquid and the cation Na+ of the zeolite. The electric conductivity of the zeolite crystals increased by three times under dry conditions