This thesis investigates the electrical and electrochemical properties and the long-term stability of anodes of the solid oxide fuel cell (SOFC). A model is suggested, which describes the impedance spectra of symmetrical anode cells. According to this, the series resistance in the spectra is caused by the resistance of the electrolyte (YSZ), ohmic parts of the anodes, which are described as porous electrodes, and by the partial contacting of the anodes. A major contribution to it is provided by the nickel matrix in the anodes. The high frequency relaxation in the spectra is assigned to the transfer reaction, the low frequency to a gas diffusion inhibition along the gas supply channels. The degradation of the symmetrical anode cells, which has been observed in long-term experiments, is ascribed to a degradation of the electrolyte material, of the transfer reaction, of the nickel matrix in the anodes and of the contact resistance between the anodes and the current collecting nickel grids. The degradation rate of the last two depends on the gas composition. A model for the observed behaviour in time is presented. / Diese Arbeit untersucht die elektrischen und elektrochemischen Eigenschaften und die Langzeitbeständigkeit der Anoden von Festoxid-Brennstoffzellen (SOFC). Ein Modell wird vorgestellt, mit dem die Impedanzspektren symmetrischer Anodenzellen beschrieben werden können. Demnach ist der Serienwiderstand in den Spektren verursacht durch den Widerstand des Elektrolyten (YSZ), ohmsche Anteile in den Anoden, die als poröse Elektroden beschrieben werden, und durch die partielle Kontaktierung der Anoden. Maßgebliche Beiträge liefert hier die Nickelmatrix in den Anoden. Die hochfrequente Relaxation in den Spektren wird der Durchtrittsreaktion, die niederfrequente einer Gasdiffusionshemmung entlang der Gasversorgungskanäle zugeordnet. Die in Langzeitversuchen beobachtete Degradation der symmetrischen Anondenzellen wird zurückgeführt auf eine Degradation des Elektrolytmaterials, der Durchtrittsreaktion, der Nickelmatrix in den Anoden und des Kontaktwiderstandes zwischen den Anoden und den stromabnehmenden Nickelnetzen. Die Degradation der beiden letzteren ist in ihrer Rate abhängig von der Gaszusammensetzung. Ein Modell für das beobachtete zeitliche Verhalten wird vorgestellt.

La2Mo2-yWyO9 (y = 1.0 to 2.0) oxides were synthesized by conventional solid state route and studied by XRD, TC-XRD and DTA. A phase diagram of the series was proposed. The thermodynamically stable phases at room temperature are: for 1.0≤ y ≤1.2 a cubic β-La2Mo2O9 type solid solution, for 1.3≤ y ≤1.575 a biphasic mixture of β-La2Mo2O9 type + α-La2W2O9 type phases, and for 1.6≤ y ≤2.0 a triclinic α-La2W2O9 type solid solution. Inhomogeneous distribution of W is suspected in the biphasic samples. It is clear that the compounds above y =1.2 are not suitable for SOFC applications.Cationic diffusion studies were performed using SIMS on La2Mo2O9 (LMO)/La0.8Sr0.2MnO3-δ (LSM) annealed couples. Rod shaped LaMnO3 grains were observed on LMO pellet and SrMoO4 type phases were seen to be growing on LSM pellet. Hypotheses for possible reaction mechanisms are presented. Bulk diffusion coefficients of Sr and Mn in LMO and of Mo in LSM are extrapolated to be around 1x10-20 cm2.s-1 and 1x10-15 cm2.s-1, respectively, at 800oC. Similar diffusion studies were performed by depositing Mn and Sr cation rich solutions on LMO pellets and Mo rich solution on LSM pellet. Mn solution was observed to be forming, upon annealing, LaMnO3 single crystals on the surface of the LMO pellet. Mo in LSM and Sr in LMO diffusion coefficients appear to be much higher than in LMO/LSM couple experiments, namely around 1-2x10-10cm2.s-1 at 1150°C. Because of the reactivity, LMO/LSM couple is not desirable for SOFC applications, unless an appropriate buffer layer separates them.The stability of LMO and W-LMO was studied under reductive atmospheres. Successive structural changes from LMO to La7Mo7O30 (7730), an amorphous reduced phase La2Mo2O7-δ, and partial decomposition to metallic Mo were observed as a function of oxygen loss. The pO2 stability domain of La2Mo2-yWyO9 did not appear to change with W content, but the reduction kinetics varied with y. At reverse, the stability limit of the 7730 phase was found to be dependent on W content. The amorphous reduced phase can accommodate a wide range of oxygen stoichiometry (7-δ from 6.69 to 6.20), but its stability vs. pO2 is questioned. Resistivity measurements performed on a low compacity crack-free amorphous La2Mo2O7-δ sample showed significant increase in the conductivity (> 1 S.cm-1 at 1000 K) relative to La2Mo2O9, with a pseudo activation energy 0.255eV. It is postulated that n-type electronic conductivity arises from partial reduction of hexavalent Mo6+ to a mixture of Mo3+ and Mo4+.

A numerical model was developed to evaluate the performance of detailed solid oxide fuel cell (SOFC) anode microstructures obtained from experimental reconstruction techniques or generated from synthetic computational techniques. The model is also capable of identifying the linear triple phase boundary (TPB) reaction sites and evaluating the effective transport within the detailed structures, allowing a comparison between the structural properties and performance to be conducted. To simulate the cell performance, a novel numerical coupling technique was developed in OpenFOAM and validated. The computational grid type and mesh properties were also evaluated to establish appropriate mesh resolutions to employ when studying the performance. The performance of a baseline synthetic electrode structure was evaluated using the model and under the applied conditions it was observed that the ionic potential had the largest influence over the performance. The model was used in conjunction with a computational synthetic electrode manufacturing algorithm to conduct a numerical powder to power parametric study investigating the effects of the manufacturing properties on the performance. An improvement in the overall performance was observed in structures which maximized the number of reaction sites and had well established transport networks in the ion phase. From the manufacturing parameters studied a performance increase was observed in structures with low porosity and ionic solid volume fractions near the percolation threshold, and when the anodes were manufactured from small monosized particles or binary mixtures comprising of smaller oxygen ion conductive particles. Insight into the anode thickness was also provided and it was observed that the current distribution within the anode was a function of the applied overpotential and an increase in the overpotential resulted in the majority of the current production to increase and shift closer to the electrode-electrolyte interface. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-10-01 09:41:47.617

Thesis (M. Tech. - (Engineering: Electrical, Department: Electronic Engineering, Faculty of Engineering and Technology)) -- Vaal University of Technology, 2011. / “Never before in peacetime have we faced such serious and widespread shortage of energy” according to John Emerson, an economist and power expert for Chase Manhattan Bank. Many analysts believe that the problem will be temporary, but others believe the energy gap will limit economic growth for years to come. A possible solution to this problem can be fuel cell technology. Fuel cells (FCs) are energy conversion devices that generate electricity from a fuel like hydrogen. The FC however, could also be used in the reverse or regenerative mode to produce hydrogen. The reversible fuel cell (RFC) can produce hydrogen and oxygen by introducing water to the anode electrode chamber, and applying a potential across the anode and cathode. This will cause the decomposition of the water to produce oxygen at the anode side and hydrogen at the cathode side. In order to make this process as efficient as possible several aspects need to be optimised, for example, the operation temperature of the RFC, water management inside the RFC and supply voltage to the RFC. A three cell RFC and its components were constructed. The three cell RFC was chosen owing to technical reasons. The design factors that were taken into consideration were the different types of membranes, electrocatalysts, bipolar plates and flow topologies. A water trap was also designed and constructed to eliminate the water from the hydrogen water mixture due to water crossover within the MEA. In order to optimise the operation of the RFC a number of experiments were done on the RFC. These experiments included the optimal operating voltage, the effect that the temperature has on the production rate of hydrogen, and the effect that the water flow through the RFC has on the production rate of hydrogen. It was found that there is no need to control the water flow through the RFC because it had no effect on the production rate of hydrogen. The results also showed that if the operating temperature of the RFC were increased, the energy it consumes to warm the RFC significantly decreases the efficiency of the whole system. Thus the RFC need not be heated because it consumes significantly more energy to heat the RFC compared to the energy available from the hydrogen produced for later use. The optimised operating voltage for the three cell RFC was found to be 5.05 V. If the voltage were to be increased or decreased the RFC efficiency would decrease.

Le gaz électrogénéré dans les réacteurs électrochimiques est un phénomène à la fois électrochimique et hydrodynamique. La chute ohmique dans la solution électrolyte est l'un des paramètres importants à évaluer pour l'optimisation des réacteurs électrochimiques. Elle est due à la résistance de la solution, donc, à sa conductivité électrique et la distance entre les deux électrodes. Pour réduire la consommation énergétique de la cellule de réduction électrolytique de particules d'hématite en fer métallique, on a étudié la conception des anodes, sièges de la production des bulles d'oxygène, dans deux cellules équivalentes d'électrolyse d'eau dans un milieu alcalin. Les résultats ont montré que seulement 25% de l'anode est réellement active et que le taux de rétention augmente le long de l'anode et les bulles atteignent leur vitesse terminale dès 50% de la hauteur de l'anode. Ceci nous a permis de formuler des recommandations qui permettent d'avoir les meilleures conditions de désengagement des bulles électrogénérées, pour une consommation énergétique plus faible du procédé électrochimique / Electrogenerated gas in electrochemical reactors is considered as an electrochemical and hydrodynamic phenomenon. The ohmic drop in the electrolyte solution is one of important parameter to evaluate for the optimization design of electrochemical reactors. It is due to the resistance of the solution, therefore, its electrical conductivity and of the distance between the two electrodes. To reduce the energy consumption of the electrolytic reduction cell of hematite particles to metallic iron, we studied the design of anode, the location of oxygen bubbles production, in two equivalent cells for water electrolysis in an alkali media. The results showed that the gas hold up increases along the anode and only 25% of the initial anode height is actually active. Moreover the bubbles reach their terminal velocity after 50% of the initial anode height. This allowed us to formulate recommendations that allow the best conditions of bubbles electrogenerated disengagement and low energy consumption

O vermelho de alizarina S é um corante cuja cor é função do pH. É uma antraquinona sulfonada que possui dois grupos fenólicos ligados ao mesmo anel onde se encontra o grupo sulfônico. Usualmente é comercializado sob a forma de sal monossódico, também chamado alizarinossulfonato de sódio ou simplesmente vermelho de alizarina. Esse corante pode ser sintetizado pela oxidação e hidroxilação do antraceno, seguida de sua sulfonação. Ele é largamente empregado em histoquímica, análises quantitativas e em indústrias têxtil e de couros. Na indústria de couros, esse corante vem acompanhado de grandes cargas de íon cloreto, o que é vantajoso para a aplicação de eletrodos ADE&reg no tratamento eletroquímico e fotoquímico eletro-assistido desse corante, haja vista que esses eletrodos são capazes de produzir espécies de cloro ativo altamente oxidantes, como gás cloro em pH fortemente ácido (< 2,00). Nesse trabalho foram empregados tratamentos eletroquímicos (puro e eletroquímico foto-assistido) para tratar o vermelho de alizarina S. Foram feitos estudos de densidade de corrente, concentração de cloreto de sódio, temperatura e investigação da natureza dos processos eletroquímicos irradiados. Para monitorar as degradações foram empregadas as técnicas de UV-Vis, DQO, COT, AOX e CLAE-MS. Percebeu-se que a concentração de cloreto de sódio e a corrente influenciam diretamente na velocidade de descoloração. Também foi possível notar que a regra de Van\'t Hoff equilibra-se com a regra de solubilidade dos gases em estudos de temperatura. Observou-se ainda que a irradiação aumenta muito o rendimento oxidativo das degradações, além de diminuir a quantidade de AOX gerados no produto final. Notou-se também que diminuindo a concentração de corante, a constante de velocidade de descoloração aumenta. Para monitorar os materiais eletródicos, foram empregadas as técnicas de VC, EDX e MEV. Constatou-se que eletrodos de composição Ti/Ir1-xSb1-ySn1-zO2 com baixo teor de Ir não são mecânica e eletroquimicamente resistentes, sendo necessário aumentar a concentração desse elemento e de Sb no material eletródico para incrementar a eficiência e a estabilidade. Palavras chave: Vermelho de alizarina S, ânodo dimensionalmente estável, cloreto, tratamento eletroquímico, tratamento eletroquímico irradiado / Alizarin red S is a dye whose color is a function of pH. It is a sulfonated anthraquinone which has two phenolic groups connected to the same ring where there is the sulphonic group. It is usually commercialized in the form of monossodic salt, also called sodium alizarinessulphonate or simply alizarin red. This dye can be synthesized by oxidation and hidroxilation of anthracene, followed by sulphonation reaction. It is largely used in histochemistry, quantitative analysis, textile and leather industries. In leather industry, this dye is accompanied by large quantities of chloride ions, which is advantageous for the application of DSA&reg electrodes in electrochemical or photo-assisted electrochemical treatment. This electrodes are capable of producing chlorine species, highly active oxidants such as chlorine gas in strongly acid pH (< 2.00). In this work we employed pure electrochemical and photo-assisted electrochemical treatments to degrade alizarin red S. The current density, concentration of sodium chloride, temperature parameters and the nature of irradiated electrochemical process were studied. To monitor the degradation were employed techniques of UV-Vis, COD, TOC, AOX and HPLC-MS. It was noticed that the sodium chloride concentration and the current directly influence in the rate of discoloration. It was also possible to note that the Van\'t Hoff rule is balanced with the gases solubility rule in temperature studies. It was observed that irradiation increases the efficiency of oxidation and reduce the amount of AOX generated in the final product. It was also noted that lowering the concentration of dye, the discoloration rate constant increases. To monitor the electrodic materials were used CV, SEM and EDX techniques. It was found that electrodes of Ti/Ir1-(x+y)SbxSnyO2 with low quantities of Ir are not mechanically and electrochemically resistant. Because this, it is necessary to increase the concentration of Sb and Ir elements in electrodic material to increase efficiency and stability. Key words: Alizarin red S, dimensionally stable anode, chloride, electrochemical treatment, irradiated electrochemical treatment

La fabrication de cellules de piles à combustible IT-SOFC de large dimension par un nouveau procédé simple et peu coûteux est présentée dans ce manuscrit. L’optimisation de ce nouveau procédé en regard de l’utilisation d’agents de porosité, d’épaisseur de couches et de température de frittage a été réalisée. Les résultats des tests électrochimiques sur des cellules de surface active 10 cm2 réalisés dans le dispositif Fiaxell semi-ouvert ont été détaillés pour différentes cellules. Des tests de performance de longue durée ont également été menés sur le dispositif Fiaxell, présentés et discutés. La préparation et la réalisation d’un nouveau banc de test de stack a également été mené et présenté dans ces travaux. / The fabrications of large area IT-SOFC planar cell by new simple and cost effective process were explained. The optimization of the new process with respect to pore formers, thickness of layers, sintering temperature were performed. The electrochemical results of 10cm2 performed in Fiaxell open flange set up were detailed with respect to different configuration. Long term ageing performance tests of single cells were conducted in Fiaxell device and results are discussed. Preparation of new test bench and stacking process performed till now were briefed.

Os ésteres de ácido ftálico são utilizados como aditivos na manufatura de plásticos e a contaminação do meio ambiente por esses compostos pode ocorrer por diferentes mecanismos. Dado o efeito destes no sistema endócrino de animais e seres humanos, efluentes contendo esses compostos sintéticos devem ser adequadamente tratados antes de qualquer descarte. Os tratamentos convencionais são ineficientes para tratar efluentes aquosos contendo esses ésteres e a oxidação eletroquímica tem sido utilizada como uma opção viável. Assim, neste trabalho foi estudada a degradação eletroquímica de dimetil ftalato (DMFt) utilizando três tipos de ânodos: Ti/Ru0.3Ti0.7O2, F-&beta;-PbO2 e diamante dopado com boro (DDB). Os experimentos foram conduzidos em condições galvanostáticas em células de compartimento do tipo filtro-prensa e vários parâmetros, tais como, eletrólito suporte e a densidade de corrente, foram avaliados. Durante as eletro-oxidações, alíquotas das soluções foram analisadas cromatograficamente e por determinações de carbono orgânico total (COT) e demanda química de oxigênio (DQO). Quando utilizado o ânodo de Ti/Ru0.3Ti0.7O2, foram observados níveis de combustão próximos a 100% em baixos valores de carga elétrica aplicada, indicando um possível processo de incineração direta. Com a incidência de radiação UV incidindo diretamente na superfície do eletrodo, foi obtida a completa remoção de DMFt e 98 % de mineralização em meio ácido, elevadas concentração de cloreto e temperatura. A limitação de ambos os processos foi o transporte de massa e assim, os melhores resultados foram obtidos a baixas densidades de corrente. Com o uso do ânodo de &beta;-PbO2 a remoção de DMFt foi superior na presença de Na2SO4 e em baixas densidades de corrente, com 40 % de mineralização. Com o ânodo de DDB foram realizadas eletro-oxidações na ausência e na presença de radiação UV e ultrassônica. Foi obtida a completa remoção de DMFt, COT e DQO em todas as condições estudadas, com maior eficiência a baixas densidades de corrente, devido a menor limitação por transferência de massa. Ocorreu um efeito positivo na eletrooxidação com aplicação conjunta das duas radiações, no entanto, menor do que o obtido com a aplicação destes processos separadamente. O mecanismo de degradação proposto apresenta a oxidação de DMFt seguida da remoção de grupos metil éster e a quebra do anel aromático para formar ácidos carboxílicos, os quais são mineralizados a dióxido de carbono. Na presença de cloreto, a produção de clorofenóis e ácido tartárico e o aumento na concentração dos intermediários formados são as principais diferenças observadas. / The phthalic acid esters are used as additives in plastics manufacturing and the environmental contamination by these compounds may occur by different mechanisms. Considering its effect on the endocrine system of animals and humans beings, effluents containing these synthetic compounds must be properly treated before any disposal. Traditional methods present limited efficiency for treating wastewater containing these esters and electrochemical oxidation has been proposed as a viable option. In this work, the electrochemical degradation of dimethyl phthalate (DMFt) using three types of anodes: Ti/Ru0.3Ti0.7O2, &beta;-PbO2,F and boron-doped diamond (BDD) was studied. The experiments were performed under galvanostatic conditions using a one compartment filter-press cell and different parameters, such as, electrolyte and current density, were analyzed. During the electro-oxidations, aliquots of the solutions extracted at diffent times were analyzed by liquid chromatography and by variations of total organic carbon (TOC) and chemical oxygen demand (COD). Using Ti/Ru0.3Ti0.7O2 anode, the combustion levels were almost 100% when low values of electrical charge were applied, indicating a possible direct incineration process. Applying UV radiation to the electrode surface, the complete removal of DMFt and 98% mineralization were obtained in acid medium with relative high chloride concentration. Both processes were limited by mass transport and therefore, the best results were obtained at low current densities. Using &beta;-PbO2 anode, the removal of DMFt was higher with 40% of mineralization in the presence of Na2SO4 and at low current densities. Using DDB anode, the electrooxidations were performed in the absence and presence of UV and ultrasonic radiations. The complete removal of DMFT, TOC and COD was obtained for all conditions studied with greater efficiency at low current densities because the smallest mass transfer limitation. A positive effect on the electro-oxidation was observed when UV and ultrasound radiation were applied simultaneously however, lower than that obtained with the application of the processes separately. The degradation mechanism proposed presents the oxidation of DMFt followed by removal of methyl ester groups and breakage of the aromatic ring to form carboxylic acids, which are mineralized to carbon dioxide. In the presence of chloride, the production of chlorophenol and tartaric acid and the increased concentration of the intermediates formed are the majors differences observed.

Este trabalho compreendeu os estudos de síntese química de pós por via úmida, de processamento cerâmico e de redução do óxido de níquel contido nos compósitos de céria dopada com samária e gadolínia, aplicados, principalmente, como anodos de Células a Combustível de Óxido Sólido. A rota adotada para a preparação dos pós com composição Ce0,8(SmGd)0,2O1,9/NiO e proporção em massa de 40 : 60% foi a coprecipitação de hidróxidos associada ao tratamento solvotérmico, utilizando-se como matérias-primas cloretos de cério, níquel, samário e gadolínio. O surfactante aniônico brometo de cetil trimetil amônio (CTAB) também foi utilizado na etapa de precipitação na relação molar Metal / CTAB entre 1 e 3. A influência do solvente orgânico utilizado no tratamento solvotérmico dos pós foi analisada utilizando o etanol, propanol e o butanol, nas condições de temperatura de 150ºC por 16 h, com e sem calcinação a 600ºC por 1h, e moagem em moinho de bolas. As amostras compactadas foram sinterizadas em temperaturas entre 1200 e 1400ºC por 1h. A redução in situ do NiO-SGDC foi estudada na amostra cerâmica preparada nas seguintes condições: síntese por coprecipitação usando ou não o CTAB, tratamento solvotérmico em butanol, calcinação a 600ºC, prensagem e sinterização a 1350ºC por 1h. O processo de redução das amostras sintetizadas em butanol foi avaliado em forno tubular em atmosfera dinâmica de 4%H2/Ar, fixando-se a temperatura a 900°C e variando-se o tempo entre 10 e 120 minutos. A redução também foi relizada nos compósitos sintetizados utilizando o CTAB na proporção Metal/CTAB = 2, tratados termicamente em etanol e butanol, após calcinação, prensagem e sinterização em forno tubular sob atmosfera de H2/Ar em isotermas de 700, 800 e 900°C por períodos entre 2 e 240 minutos. Os pós, as cerâmicas e os compósitos sintetizados em laboratório foram comparados com os materiais compósitos produzidos com pós de origem comercial. A caracterização dos pós foi realizada por difração de raios X (DRX), microscopia eletrônica de varredura (MEV), área de superfície específica por adsorção gasosa de nitrogênio (BET), análise térmica (TG/DTA) e distribuição granulométrica por espalhamento de feixe laser (Cilas). As cerâmicas foram analisadas por microscopia eletrônica de varredura, DRX e medidas de densidade pela técnica de imersão em água (método de Arquimedes). As cerâmicas e os compósitos foram caracterizados eletricamente por medidas de resistência elétrica pelo método de quatro pontas DC. Os resultados mostraram que os pós sem calcinação apresentaram as estruturas cristalinas características da céria e do hidróxido de níquel, e elevada área de superfície específica (80 m2/g). As cerâmicas provenientes dos pós tratados com etanol e propanol apresentaram boa homogeneidade química, estrutural e valores de densidade de 99% em relação a densidade teórica. Verificou-se que 80 a 90% do NiO é reduzido e as porosidades atingidas pelos compósitos são da ordem de 30%. A caracterização elétrica mostrou que a condutividade iônica da fase cerâmica do anodo, sintetizado solvotermicamente em butanol, possui valor de 0,03S.cm-1 na temperatura de 600°C, valor superior aos encontrados na literatura. A caracterização elétrica dos compósitos reduzidos revelou alta condutividade elétrica característica do níquel metálico, indicando percolação adequada da fase de níquel e distribuição homogênea de ambas fases cerâmica e metálica. As rotas de síntese e os materiais estudados são, portanto, adequados para a aplicação como anodo das IT-SOFCs. / This work comprises studies of powder chemical synthesis by wet route, ceramic processing and reduction of nickel oxide added to samaria and gadolinia doped ceria ceramic composite, mainly applied as Solid Oxide Fuel Cells anode. The route adopted for the powders preparation with composition Ce0.8(SmGd)0.2O1.9/NiO and mass ratio of 40:60% was hydroxides coprecipitation and solvothermal treatment, using as start materials the cerium, nickel, samarium and gadolinium chlorides. The anionic surfactant cetyltrimethylammonium bromide (CTAB) was also used in the precipitation stage with the molar ratio Metal/CTAB ranging between 1 and 3. The influence of organic solvent used in the powders solvothermal treatment was analyzed by using ethanol, propanol and butanol at temperature of 150°C for 16h, with and without calcination at 600°C for 1h, and grinding in a ball mill. The compacted samples were sintered at temperatures between 1200 and 1400°C for 1h. The in situ reduction of NiO-SGDC was studied in the samples synthesized by coprecipitation using CTAB and without it, followed by solvothermal treatment in butanol, calcined at 600°C, pressed and sintered at 1350°C for 1h. The reduction procedure was evaluated in a tubular oven and atmosphere of 4% H2/Ar, setting the temperature at 900°C and time range between 10 and 120 minutes. The composites synthesized using the CTAB in the proportion of Metal/CTAB = 2, followed by solvothermal treatment in ethanol and butanol, after calcining, compaction and sintering, was also reduced in a tubular oven and atmosphere of 4% H2/Ar, setting the temperature at 700, 800 and 900°C and time range between 2 and 240 minutes. The powders, ceramics and the sinterized cermets syntesized in laboratory were compared to the materials produced with comercial powders. The powders characterization was performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area by nitrogen gas adsorption (BET), thermal analysis (TG / DTA) and particle size distribution by scattering beam laser (Cilas). Ceramics were analyzed by scanning electron microscopy (SEM), XRD and density measurements by the technique of immersion in water (Archimedes method). The ceramics and cermets condutivity was characterized by the four probe DC method. The results obtained showed that the powders without calcination presented the crystal structures characteristics of ceria and nickel hydroxide, and high specific surface area (80m2/g) . The ceramic prepared from powders treated with ethanol and propanol had a high chemical and structural homogeneity and density values corresponding to 99% of the theoretical density. It was found that 80 to 90 % of NiO is reduced and the porosity of the composite reached about of 30 %. The anode ceramic phase synthesized solvothermically in butanol presented electrical conductivity of 0.03S.cm-1 at 600°C, higher than found at literature. The reduced cermets electrical characterization showed high electrical conductivity feature of metallic nickel, indicating the nickel phase good percolation and homogeneous distribution of both ceramic and metallic phases. Considering all these results, the synthesis routes and studied materials are suitable for use as the anode IT- SOFCs.

Depuis la découverte par le Pr. Kagan en 1977 de conditions douces de synthèse du diiodure de samarium (SmI2), ce réactif est rapidement devenu un des meilleurs réducteurs chimiques utilisé en synthèse organique. Cependant, en tant que réducteur mono-électronique, il est souvent employé en quantité sur-stœchiométrique ce qui impose l’utilisation de quantité importante de réactif qui possède par ailleurs une faible solubilité dans le THF (solvant de choix pour ce réactif) ce qui impose également de trop importantes quantités de solvant. Dans ce travail de thèse, nous nous sommes intéressés à l’utilisation de l’électrochimie comme alternative de synthèse de SmI2 pour apporter un certain nombre de solutions aux limitations manifestes de l’utilisation de ce réactif.Dans un premier temps nous avons mis en œuvre une méthode de synthèse du SmI2 grâce à l’utilisation originale d’une anode "sacrificielle" de samarium. Le SmI2 électrogénéré, dosé et parfaitement caractérisé nous a permis de réaliser différentes réactions de formation de liaisons carbone-carbone médiées par ce réactif. Le SmI2 est produit et consommé en continu ce qui réduit considérablement les quantités de solvant habituellement exigées. Cette approche a également permis de préparer et de caractériser d’autres dérivés divalents de samarium souvent plus difficiles à synthétiser. Nous avons ensuite exploré la possibilité d’exploiter cette approche électrochimique pour la mise en place d’une nouvelle procédure catalytique en SmI2. Après avoir mis en évidence l’efficacité de la réduction électrochimique de sels trivalents de samarium en dérivés divalents grâce à l’emploi d’une cathode de samarium, nous avons établi les conditions opératoires d’une nouvelle procédure catalytique en SmI2 assistée par électrochimie évitant ainsi tout additif métallique. Cette approche catalytique a été appliqué avec succès dans différentes réactions de couplage. / Since the seminal reports of Kagan, dedicated to the preparation of samarium diiodides and its usefulness in organic synthesis, SmI2 became one of the most important reducing agents available to the synthetic organic chemist, promoting a multitude of radical and anionic reactions. However, the major limitations according to its preparation remains the concentration of SmI2 in THF (around 0.1M) and the inert atmosphere needed during its manipulation. Therefore, the majority of organic reactions mediated by SmI2 as reductive reagent require a stoichiometric amount or even a large excess.We report herein a new electrochemical method to prepare solutions of samarium diiodide in THF. The simple electrolysis of a samarium rod provides a rapid and straightforward in situ synthesis of SmI2. The electrogenerated complex catalyzes various C-C bond formations. The reagent is produced continuously and leads to efficient organic electrosynthesis with significantly smaller amounts of solvent than usually required. Moreover, samarium metal has been then used for the first time as electrode material to perform an efficient and versatile SmI2 catalytic system assisted by electrochemistry. The established electrocatalytic procedure that excludes any metal additives was successfully applied in various transformations mediated by this useful reagent.