The ionomer-membrane interface in a membrane electrode assembly connects the catalyst and membrane and allows hydrated protons to move between the catalyst and membrane. The continuous operation of the polymer membrane electrolyte fuel cell at high temperature and/or in frequent freeze/thaw cycles leads to membrane degradation and delamination of the interface, which lower the proton conductivity. In this dissertation, we modeled the chemical degradation and proton conductivity of perfluorosulfonic acid (PFSA) ionomers by ab initio calculations and macroscopic modeling. All ab initio calculations were performed using Gaussian 03 suites of program by employing B3LYP/6-311++G** method/basis set. The macroscopic modeling involves nonequilibrium thermodynamics. The results show that PFSA membranes can degrade both via side-chain and backbone in the presence of hydroxyl radical. The energetics of homolytic bond cleavage show that the C–S bond in the side-chain is the weakest link and breaks exothermally in the presence of hydroxyl radical. The C–S bond in the membrane fragment radical can break at low activation energy. The side-chain degradation also leads to the split of the backbone into two parts. The backbone degradation starts with the reaction of –COOH impurities in the backbone with the hydroxyl radical, which has the lowest activation energy, and follows an “unzipping mechanism”. The reactions in this mechanism are exothermic. The channels in the interface were modeled as cylindrical pores and the anionic charges were fixed on the pore wall. The analytical expression of proton conductivity was derived from the evolution equations for mass and momentum of hydronium ions by using an order of magnitude analysis. The results show that the conductivity increases with increasing water content and pore radius. The conductivity usually increases on decreasing the separation distance between sulfonates on the length and decreases with decreasing sulfonates separation distance on the circumference. The conductivity of the two pores, one of the interface and the other of the membrane, is closer to the conductivity of the pore with the lowest conductivity and its magnitude depends on the relative radius and length of the pores.

De nouvelles familles de liquides ioniques conducteurs par ion lithium; à anions aromatiques et aliphatiques de type perfluorosulfonate perfluorosulfonylimidure attachés à des oligoéthers (méthoxy polyéthylène glycol mPEG) de longueurs différentes ont été synthétisées et caractérisées dans le but d'améliorer l'interaction entre les chaînes de POE et les sels de lithium en améliorant la mobilité segmentaire. Ainsi différentes membranes amorphes ou peu cristallines améliorent le transport cationique par rapport aux électrolytes polymères usuels. . Leurs propriétés ont été évaluées dans deux types de polymères hôtes : un polyéther linéaire (POE) et un polyéther réticulé préparé par un procédé "VERT". Leurs parties oligooxyéthylène aident à la solvatation des cations lithium et conduisent à l'augmentation des propriétés de transport; c'est à dire la conductivité cationique et le nombre de transport. Leurs stabilités thermiques et électrochimiques sont adaptées à l'application batterie lithium-polymère. / The new families of lithium-conducting ionic liquids; aromatic and aliphatic lithium salts based on perfluorosulfonate and perfluorosulfonylimide anions attached to an oligoether (methoxy polyethylene glycol mPEG) with different lengths were synthesized and characterized with the aim to improve the salt interaction with the host polymer's POE chains while keeping a high segmental mobility. They allowed obtaining membranes with lower crystallization degree and higher cationic transport number as compared with benchmarked salts. Their properties as lithium salts were investigated in two types of host polymers i.e. a linear polyether (POE) and a cross-linked polyether prepared by a ‘GREEN' process. Their oligooxyethylene moieties improve the lithium cation solvation leading to an increase in cationic transference numbers. Their electrochemical and thermal stabilities are suitable for lithium battery application.

Cette thèse s'inscrit dans le contexte général des efforts de recherche pour développer des supports de catalyseur résistant à la corrosion qui peuvent potentiellement remplacer le carbone dans les piles à combustible à électrolyte polymère. Des nanofibres et des nanotubes à base de TiO2 et SnO2 dopés par Nb ont été préparés par filage électrostatique et caractérisés par diffraction des rayons X, spectroscopie des photoélectrons de rayons X, spectroscopie Raman, mesures de surface spécifique et de conductivité électronique. Les nanofibres de TiO2 et SnO2 dopées par Nb présentent une conductivité et une surface spécifique supérieure à celle des oxydes non dopés. Des nanoparticules de platine ont été préparées en utilisant une méthode polyol modifié par micro-ondes, et déposées sur les supports fibreux. La caractérisation électrochimique des électrocatalyseurs ainsi obtenus a été réalisée ex situ par voltamètre en utilisant une électrode à disque tournant. Le catalyseur supporté, Pt sur SnO2 dopé par Nb présenté une stabilité électrochimique supérieure à celle d'un catalyseur Pt sur carbone commercial (Vulcan XC-72R). Une cathode Pt/Nb-SnO2 préparée par pulvérisation a pu être intégrée dans un assemblage membrane-électrode (AME) et caractérisée in situ dans une cellule de pile à combustible à électrolyte polymère. L'AME a présenté une durée de vie plus élevée mais une densité de puissance plus faible qu'un AME contenant Pt/C. Les nanotubes de SnO2 dopés par Sb ont une conductivité plus élevée que celle des matériaux dopés par Nb et lorsqu'ils sont intégrés dans une cathode, fournissent une densité de puissance accrue par rapport à une cathode à base de Nb- SnO2. / The objective of this thesis is to develop corrosion resistant catalyst support materials that can potentially replace carbon in Polymer electrolyte fuel cells. Therefore, Nb doped TiO2 and SnO2 nanofibres and nanotubes were prepared by electrospinning and characterised by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, N2 adsorption/desorption analysis and electronic conductivity measurements. The obtained Nb doped TiO2 and SnO2 one dimensional structures demonstrated higher conductivity and surface area than non-doped oxides. Pt nanoparticles were prepared using a modified microwave-assisted polyol method and deposited on the electrospun supports. Electrochemical characterisation of the obtained electrocatalysts was performed ex situ using a rotating disc electrode, and compared with a commercial carbon support (Vulcan XC-72R). Pt supported on Nb doped SnO2 provided higher electrochemical stability in comparison to Pt on carbon. Thus, a cathode of Pt/Nb-SnO2 prepared by spray-coating was integrated into Membrane Electrode Assembly (MEA) and characterised in situ in single Polymer electrolyte fuel cell. The MEA exhibited higher durability though lower power density compared to MEA with Pt/C based cathode. Sb doped SnO2 nanotubes have higher conductivity than Nb doped material and when integrated into a cathode, provided enhanced power density in comparison to Nb-SnO2 based cathode.

As células eletroquímicas emissoras de luz (PLECs) pertencem a um novo ramo importante na optoeletrônica orgânica devido ao seu grande potencial para ser usado como ponto - pixels para telas coloridas e também para painéis de iluminação. Diferentemente de diodos orgânicos emissores de luz (OLEDs), a tecnologia de OLECs ainda está em estágios iniciais de desenvolvimento, em comparação com a tecnologia de OLED , OLECs tem a vantagem de ser operado em ambas as polaridades de tensão ( para a frente ou de polarização reversa ), e, além disso, o seu desempenho é menos dependente dos materiais do eletrodos e a espessura da camada ativa do dispositivo. A camada ativa de um OLEC compreende uma mistura de um polímero eletroluminescente conjugado e um eletrólito de polímero. Consequentemente, o transporte elétrico durante a operação do dispositivo envolve uma combinação de dinâmica iônica e eletrônica e efeitos intrincados nas interfaces com os eletrodos. A literatura apresenta até agora duas abordagens diferentes para descrever o fenômeno de transporte nas OLECs. O modelo de eletrodinâmica, que combina separação iônica com o processo de difusão limitada eletrônica, e o modelo de dopagem eletroquímico que considera uma dopagem eletroquímica do polímero conjugado, dando a formação de uma junção p-i-n na camada ativa. Usando as medidas de decaimento da corrente sobre uma voltagem aplicada e espectroscopia de impedância /admissão , investigamos o transporte de portadores de carga em um OLEC tendo como camada ativa uma mistura de poli [ ( 9, 9 - dioctyl - 2, 7 - divinileno - fluorenileno ) - alt - co - { 2 - metoxi -5 - ( 2 - etil- hexiloxi ) -1,4 - fenileno } ] ( PFGE ) , com poli ( óxido de etileno ) ( PEO ) complexado com triflato de lítio ( TriLi ) , na proporção 01:01 : X , onde X foi de 0,10 , 0,05 , 0,01 , 0,00. Foram obtidos dados importantes relacionados com efeito iônico e eletrônico durante a operação deste PLEC, sendo que as medidas de transiente e de impedância mostraram que o movimento iônico auxilia o processo de injeção eletrônica. Outro fato relevante é que o desempenho da PLEC é dependente da formação da dupla camada iônica que tem sua espessura abaixo de 10 nm e que o processo de sua formação depende altamente da condução iônica, que por sua vez vai depender da quantidade de íons e de sua mobilidade, sendo influenciando por fatores como concentração de sal e temperatura do dispositivo. As medidas realizadas mostram que as PLECs com 2,5 e 5% de concentração de sal apresentam o melhor desempenho. / Organic Light-emitting Electrochemical Devices (OLECs) belong to a new important branch in organic optoelectronics due to their great potential to be used as dot-pixels for color displays and also to lighting panels. Differently from organic light-emitting diodes (OLEDs), the technology of OLECs is still in early stages of development. In comparison to OLED technology, OLECs have the advantage in being operated in both voltage polarities (forward or reverse bias), and, in addition, their performance is less dependent on the electrode materials and the device thickness. The active layer of an OLEC comprises a mixture of a conjugated electroluminescent polymer and a polymer electrolyte. Consequently, the electrical transport during the device operation involves a combination of ionic and electronic dynamics and intricate effects at the interfaces with the electrodes. The literature presents so far two different approaches to describe the transport phenomenon in the OLECs. The electrodynamic model, which combines ionic charge separation with electronic diffusionlimited process, and the electrochemical doping model that consider an electrochemical doping of the conjugated polymer, giving and the formation of a p-i-n junction in the active layer. Using current decay under an applied voltage measurements and impedance/admittance spectroscopy, we investigate charge carrier transport in an OLEC having as active layer a mixture of poly [(9, 9 - dioctyl - 2, 7 - divinileno - fluorenileno) - alt - co - {2 - methoxy -5 - (2 - ethyl-hexyloxy) -1,4 - phenylene}] (PFGE), with poly (ethylene oxide) (PEO) complexed with lithium triflate (TriLi), in the proportion 1:1:X, where X was 0.10, 0.05, 0.01, 0.00. We have obtained important results related to ionic and electronic effect during this operation PLEC. This measurements of transient current and impedance showed that ionic movement aids the process of electron injection. Another relevant fact is that the performance of PLEC is dependent on the formation of ionic double layer having thickness below 10 nm. The formation of this double layers is highly dependent on the ionic conduction, which in turn will depend on the amount of ions. The ionic mobility is influenced by factors such as salt concentration and temperature of the device. The measurements show that PLECS with 2.5 and 5% salt concentration had the best perform.

Os componentes do conjunto membrana/eletrodos (MEA) das células a combustível de membrana de eletrólito polimérico/Polymer Electrolyte Membrane Fuel Cells (PEMFC) são sensíveis a impurezas, as quais podem vir do ar, do gás combustível e/ou da degradação dos componentes do módulo. Amônia, sulfeto de hidrogênio e monóxido de carbono são juntos os três principais subprodutos cotaminadores nos processos de geração de hidrogênio por reforma de combustíveis. Estes contaminadores afetam negativamente o desempenho das PEMFCs, assim é importante o entendimento destes efeitos para mitigá-los e introduzir a tecnologia das PEMFCs no mercado consumidor. Desta forma experimentos foram realizados visando diagnosticar os efeitos da amônia e do sulfeto de hidrogênio sobre os componentes do MEA das PEMFCs. Para a contaminação por sulfeto de hidrogênio foi provado, utilizando-se da técnica de cromatografia gasosa e de stripping, que a contaminação ocorre através da interação química e eletroquímica do contaminador com a superfície do catalisador de platina, e que estas interações ocorrem via um processo dissociativo e um processo oxidativos respectivamente. Estes processos de interação geram enxofre adsorvido sobre a superfície da platina, a qual é bloqueada para posterior oxidação de hidrogênio, gerando sobrepotenciais que reduzem a diferença de potencial da célula. Utilizando-se da técnica de cromatografia gasosa e agora de voltametria cíclica foi mostrado na PEMFC, que durante o processo de remoção do enxofre adsorvido a platina dióxido de enxofre é gerado. Ainda na PEMFC, foi mostrado utilizando-se da técnica de \"air bleed\" que maiores tolerâncias ao sulfeto de hidrogênio podem ser alcançadas, apesar de ser insignificante. Para o caso da contaminação da PEMFC por amônia, indiretamente foi mostrado, utilizando-se técnicas eletroquímicas solução de ácido perclórico, que amônia pode afetar a reação de redução de oxigênio pela sua adsorção sobre a superfície do catalisador, ou pelo bloqueio da mesma para posterior adsorção/redução de oxigênio. Em estudos de absorção de água e condutividade de membranas de NafionTM, sob diferentes frações catiônicas (prótons/amônio), em contato com água na fase vapor sob diferentes atividades, foi mostrado que quanto maior a concentração de íons contaminadores no eletrólito menor a quantidade de água absorvida e menor a condutividade da membrana. Também foi mostrado que se tais membranas fossem usadas como eletrólito em PEMFCs, o desempenho da célula seria afetado drasticamente por perdas ôhmicas. Também foi mostrado que sob contaminação por amônia, PEMFCs sofrem aumentos em resistências ôhmicas devido a reduções na condutividade do eletrólito, contudo foi provado que esta representa menos de dez por cento do total de perdas observadas no desempenho da célula. Desde estudo foi concluído que amônia afeta o desempenho das PEMFCs principalmente pela redução na atividade dos prótons na camada catalítica catódica, que causa reduções no potencial misto de equilíbrio da reação de redução de oxigênio, e portanto na diferença de potencial da célula. Finalmente foi provado indiretamente que amônia deixa a célula através do equilíbrio de amônio com água, o qual deslocado gera amônia, a qual deixa a célula junto com o fluxo de gás cotódico. / The Membrane Electrode Assembly components of a PEMFC are sensitive to impurities, which can came with the air or hydrogen stream, or from the degradation of the stack components. Ammonia, hydrogen sulfide and carbon monoxide are together the main sub-products of fuel reforming processes for generating hydrogen. These contaminants negatively affect the PEMFC performance, so it is important to understand what those effects are in order to mitigate them and introduce PEMFC technology in the mass market. Therefore, experiments were carried out to diagnose the effects hydrogen sulfide and ammonia have on the MEA components of PEMFCs. For contamination by hydrogen sulfide it was proved utilizing EMS and stripping techniques that the poisoning process happens by chemical and electrochemical interactions of the contaminant with the Platinum catalyst surface, and that these interactions happen by a dissociative and oxidative process, respectively. Those processes generate sulfur adsorbed on the Platinum surface, which blocks it for further hydrogen oxidation, generating overpotentials, which reduce the cell potential. Utilizing the EMS and now the cyclic voltammetry technique it was shown that during the process of removing sulfur from the Platinum surface one generates sulfur dioxide. Using the Air Bleed technique it was shown that higher tolerances of the PEMFC against hydrogen sulfide can be reached, despite being insignificant. For contamination of the cell by ammonia it was indirectly proved utilizing electrochemical techniques in perchloric acid solutions that ammonia can affect the oxygen reduction reaction by adsorbing on the catalyst surface, or by blocking the surface for further oxygen adsorption/reduction. Studying water uptake and ionic conductivity of Nafion membranes under many different cation fractions (proton/ammonium) in contact with water vapor at different temperatures and water activities, it was proved that the more ammonium one has in the membrane the less will be the water uptake and ionic conductivity of it. It was also shown that if those membranes were used as electrolyte in PEMFC the cell performance would be severely affected by ohmic losses. It was also shown that under ammonia exposure PEMFCs suffer by ohmic resistance increases due to the lowering in the ionic conductivity of the electrolyte, however it was proved that it represent less than ten percent of the observed losses in the cell performance. From this study it was concluded that ammonia mainly affect the PEMFC performance by lowering the cathode catalyst layer proton activity, which lowers the oxygen reduction reaction equilibrium potential, and then the cell potential. Finally it was indirectly proved that ammonia leaves the cell by the equilibrium of ammonium and water, which dislocated generates ammonia that leaves the cell together with the cathode gas stream.

Polymer electrolyte membrane fuel cells (PEMFCs) are one of the most promising clean technologies under development. However, the main obstacles for commercialising PEMFCs are largely attributed to the technical limitations and cost of current PEM materials such as Nafion. Novel poly(2,5-benzimidazole) (ABPBI)/POSS based polymer composite electrolyte membranes with excellent mechanical and conductivity properties were developed in this project including (I) ABPBI, polybenzimidazole (PBI) and their copolymers were synthesised by solution polymerisation and their chemical structures were confirmed by FTIR and elemental analysis. ABPBI/ActaAmmonium POSS (ABPBI/AM) and ABPBI/TriSilanolPhenyl POSS (ABPBI/SO) composites were also synthesised in situ. High quality polymer and composite membranes were fabricated by a direct cast method; and (II) The mechanical and thermal properties, microstructure and morphology, water and H3PO4 absorbility and proton conductivity of phosphoric acid doped and undoped ABPBI and ABPBI/POSS composite membranes were investigated. SEM/TEM micrographs showed that a uniform dispersion of POSS nano particles in ABPBI polymer matrix was achieved. The best performances on both mechanical properties and proton conductivities were obtained from the ABPBI/AM composite membrane with 3 wt% of POSS (ABPBI/3AM). It was found that both the water and H3PO4 uptakes were increased significantly with the addition of POSS due to formation of hydrogen bonds between the POSS and H2O/H3PO4, which played a critical role in the improvement of the conductivity of the composite membranes at temperatures over 100oC. ABPBI/3AM membranes with H3PO4 uptake above 117% showed best proton conductivities at both hydrous and anhydrous conditions from room temperature to 160oC, which is comparable with the conductivity of commercial Nafion 117 at 20oC in water-saturated condition, indicating that these composite membranes could be excellent candidates as a polymer electrolyte membrane for high temperature applications. A new mechanism for illustrating the improved proton conductivity of composite membranes was also developed.

Doctor Scientiae - DSc / In this study novel composite electrodes were developed, in which the catalytic components were deposited in nanoparticulate form. The efficiency of the nanophase catalysts and membrane electrodes were tested in an important electrocatalytic process, namely hydrogen production by water electrolysis, for renewable energy systems. The activity of electrocatalytic nanostructured electrodes for hydrogen production by water electrolysis were compared with that of more conventional electrodes. Development of the methodology of preparing nanophase materials in a rapid, efficient and simple manner was investigated for potential application at industrial scale. Comparisons with industry standards were performed and electrodes with incorporated nanophases were characterized and evaluated for activity and durability. / South Africa

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第22708号 / 人博第958号 / 新制||人||227(附属図書館) / 2020||人博||958(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 高木 紀明, 教授 中村 敏浩 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

This work deals with preparation of PMMA based gel polymer electrolytes with high fire safety and high ionic conductivity. In the theoretical part of the work GPEs for Li – ion accumulators, fire safety tests, fire retardants are mentioned. Preparation of GPEs, electrical and other properties are described in the experimental part. Furthermore, new possible methods of gel preparation are discussed.

Dans le but d’améliorer les performances des micro-accumulateurs au lithium, de nouvelles voies de dépôt, compatibles avec des géométries texturées, sont actuellement explorées. Au cours de ce travail de thèse, un nouvel électrolyte solide déposé par voie « humide » a été développé. Ce matériau, composé d’un liquide ionique et d’un sel de lithium confinés dans une matrice solide, a été synthétisé par polymérisation in-situ d’un oligomère diméthacrylate. Afin de définir leurs caractéristiques de conduction ionique, de nouvelles méthodes, comme le suivi de la photo-polymérisation par impédance in-situ ou encore la réalisation d’un nouveau design de cellules à base de peignes interdigités, ont été développées. De plus, le transfert du lithium a été mesuré par RMN diffusionnelle. Une diminution significative de la vitesse de diffusion des ions Li+ après la photo-polymérisation a ainsi été mise en évidence. La spectroscopie Raman a permis de démontrer que celle-ci est due à la complexation des ions par les chaines de poly(oxyde d’éthylène) de la matrice solide. En outre, grâce aux observations de différentes compositions, un mécanisme de diffusion mixte des ions Li+ par migration dans le liquide et par sauts dans le solide a été identifié. Par conséquent, ces résultats nous ont permis de définir une stratégie pour améliorer la diffusion des ions Li+ : l’ajout d’un copolymère monofonctionnel a permis de diminuer la densité de réticulation de la matrice solide et ainsi d’optimiser la mobilité des chaines polymères. En effet, les performances de cyclage dans des empilements de micro-accumulateurs complets ont été améliorées. A température ambiante, ces résultats se sont révélés très proches de ceux obtenus avec l’électrolyte solide standard LiPON. En conclusion, l’analyse établie a permis de comprendre les liens entre structure et performances électrochimiques, ce qui a permis de dégager les voies d’amélioration les plus prometteuses pour ce type d’électrolytes. / New deposition techniques compatible with making tridimensional geometries are currently being investigated with the aim of improving the performances of lithium microbatteries. This work focuses on the development of a new quasi-solid electrolyte deposited by a “wet process”. An ionic liquid-based membrane containing a lithium salt was prepared by the photo-induced polymerization of a dimethacrylate oligomer. New methods such as a new type of conductivity cell based on planar interdigitated electrodes to measure ionic conductivity as well as in-situ monitoring of photo-polymerization using impedance spectroscopy were used. Transport properties of lithium ion were measured by PGSE-NMR. Interestingly, a significant reduction of lithium ion mobility was observed after UV-curing while the total ionic conductivity only decreased slightly. This phenomenon is due to the formation of lithium ion complexes with ethylene oxide moieties of the solid matrix, evidenced by Raman spectroscopy measurements. Additionally, we have shown that the structures of the complexes depend on the salt concentration and a dual solid/liquid transport mechanism was suggested. Hence, in order to improve lithium ion diffusion, a co-polymer was added in an attempt to decrease the cross-linking density of the solid matrix thus improving its segmental motion. The cyclability of the all solid state micro batteries was indeed improved. Comparable performances with the standard solid electrolyte LiPON were obtained at room temperature. In summary, it was established that electrochemical performances of the solid state microbatteries depend to a certain extent on the structure of the polymer electrolyte. Therefore it is possible to find new ways in designing these types of electrolytes for further improvement.