Este trabalho investigou a obtenção de filmes de óxido de cobalto por spray pirólise e sua caracterização para emprego como eletrocatalisador na geração de H2 por eletrólise de águas naturais via energia solar. A função desse eletrocatalisador é reduzir os sobrepotenciais necessários para eletrolisar a água e a decompor em hidrogênio e oxigênio. Para tanto, soluções precursoras de nitrato de cobalto hexahidratado foram depositadas por spray pirólise sobre uma camada de óxido de estanho dopado com flúor (FTO, em inglês) sobre um vidro sodocálcico, a diferentes concentrações e parâmetros de processo. Foram variadas a temperatura do substrato (de 190°C a 300°C), a distância entre o bico aspersor e o substrato (150 mm a 270mm). Os filmes de óxido de cobalto obtidos foram caracterizados quanto à sua cristalinidade por difração de raio-x, e quanto a sua morfologia por microscopia eletrônica de varredura. Os resultados mostraram uma forte influência da temperatura do substrato, relacionada com a natureza do solvente e do substrato, na obtenção de filmes contínuos e com aderência. Para avaliar seu desempenho na eletrólise da água, os filmes de óxido de cobalto obtidos foram ensaiados em uma célula eletroquímica, utilizando três águas distintas: água destilada, água do lago Guaíba (Porto Alegre-RS, Brasil) e do mar (Cidreira-RS, Brasil). Foi avaliada a sua eficiência na geração de hidrogênio e oxigênio, utilizando um voltâmetro de Hoffmann, pelo qual se obtinha o volume de gases gerados na eletrólise. A energia necessária para a separação da água foi fornecida por uma célula fotovoltaica exposta à radiação solar. Da mesma forma, foi avaliada sua atividade catalítica em função do tempo de eletrólise. Os resultados indicaram que os filmes eletrocatalisadores de óxido de cobalto obtidos por spray pirólise mostraram-se capazes de catalisar a eletrólise da água, baixando o sobrepotencial necessário, para todas as águas investigadas. A viabilidade de acoplar tal sistema de eletrólise de águas naturais a painéis fotovoltaicos mostrou-se viável e de grande interesse. Esta comprovação de geração de hidrogênio através de águas naturais define um curso para a implantação em larga escala de energia solar através de um mecanismo para o seu armazenamento como combustível. / This study investigated the obtaining of cobalt oxide films by spray pyrolysis and its characterization as electrocatalyst for use in the generation of H2 by electrolysis of natural water via solar energy. The function of this electrocatalyst is to reduce overpotentials needed to electrolyze water and decompose into hydrogen and oxygen. To this end, precursor solutions of cobalt nitrate hexahydrate were deposited by spray pyrolysis on a layer of fluorine-doped tin oxide (FTO) onto a soda lime glass at different concentrations and process parameters. The substrate temperature (190°C to 300 °C), the distance between the spray nozzle and the substrate (150 mm to 270mm) were varied. The films of cobalt oxide obtained were characterized for their crystallinity by x -ray diffraction, and by their morphology by scanning electron microscopy. The results showed a strong influence on the temperature of the substrate, linked to the nature of the solvent and substrate to obtain continuous films and adhesion. To assess their performance in the electrolysis of water, the films of cobalt oxide obtained were tested in an electrochemical cell using three different water: distilled water, lake water Guaiba (Porto Alegre - RS, Brazil) and the sea (Cidreira- RS, Brazil). We evaluated its effectiveness in the generation of hydrogen and oxygen, using a voltmeter Hoffmann, which was obtained by the volume of gas generated in the electrolysis. The energy required for water separation was supplied by a photovoltaic cell exposed to solar radiation. Similarly, we assessed the efficiency loss due to the electrolysis. The results indicated that the electrocatalyst cobalt oxide films obtained by spray pyrolysis were capable of catalyzing the electrolysis of water, lowering the overpotential required for all waters investigated. The feasibility of such a system of coupled natural water electrolysis photovoltaic panels proved to be feasible and of great interest. This proof of hydrogen generation through natural waters sets a course for the large-scale deployment of solar energy through a mechanism for storage as fuel.

Green algae are quite important primary producers in fresh waters. The genus Chlorella represents one of algae most frequently utilized in algal biotechnologies to produce biomass, using either autotrophic or heterotrophic cultivation systems. It is than exploited as a food supplement for humans or animals. However, particular species within the genus are morphologically indistinguishable and molecular markers should be used to characterize production strains. This work is aimed to molecularly characterize three production strains of Chlorella for patent protection purposes and to specify their phylogenetic and taxonomic position.

Submitted by Izabel Franco (izabel-franco@ufscar.br) on 2016-09-30T18:55:37Z No. of bitstreams: 1 DissTCN.pdf: 1750863 bytes, checksum: 7f270955d14599a5df96c67c05642037 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2016-09-30T19:05:44Z (GMT) No. of bitstreams: 1 DissTCN.pdf: 1750863 bytes, checksum: 7f270955d14599a5df96c67c05642037 (MD5) / Approved for entry into archive by Ronildo Prado (ronisp@ufscar.br) on 2016-09-30T19:05:52Z (GMT) No. of bitstreams: 1 DissTCN.pdf: 1750863 bytes, checksum: 7f270955d14599a5df96c67c05642037 (MD5) / Made available in DSpace on 2016-09-30T19:11:43Z (GMT). No. of bitstreams: 1 DissTCN.pdf: 1750863 bytes, checksum: 7f270955d14599a5df96c67c05642037 (MD5) Previous issue date: 2015-04-24 / Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM) / This study aimed to produce propionic acid, 1,3-propanediol and hydrogen in anaerobic fluidized bed reactor with grounded tire as support material for immobilization of biomass. The experiment took place during 278 days in six distinct phases distributed according to the hydraulic retention time (HRT), which ranged between 8 and 0.5 h. The reactor was maintained at mesophilic conditions (30 ° C) with controlled pH between 4.5 and 5.5 and crude glycerol as carbon source at a concentration of 5 g L-1. The inoculum used in the experiment was derived from the processing of poultry slaughterhouse wastewater station. The results show that the consumption of substrate conversion reached the highest value (89.8 %) in HRT of 6 hours. The biogas produced was composed of H2 and CO2 and the greatest recorded content of H2 has been reached (81.2%) in HRT of 4 hours. The principal soluble metabolite produced were propionic acid and 1,3-propanediol, with maximum yields of 1,77 and 0,82 mol.molglicerol -1, respectively. Both maximum yields were achieved in HRT of 8 h. At all stages of this work occurred predominantly propionic acid, with maximum molar percentage (96,9 %) achieved in HRT of 0,5 h. The second predominant metabolite obtained was 1,3- propanediol, achieving greater molar percentage (29.4%) in HRT of 6 hours. / O presente trabalho teve por objetivo produzir ácido propiônico, 1,3-propanodiol e hidrogênio em reator anaeróbio de leito fluidizado com pneu triturado como material suporte para adesão da biomassa. O experimento ocorreu durante 278 dias, em seis fases distintas distribuídas em função do tempo de detenção hidráulica (TDH), que variou entre 8 e 0,5 h. O reator foi mantido em condições mesofílicas (30 °C), com pH controlado entre 4,5 e 5,5 e possuía glicerol bruto como fonte de carbono na concentração de 5 g L-1. O inóculo utilizado no experimento foi proveniente de estação de tratamento de efluente de abatedouro de aves. Os resultados obtidos mostram que o consumo de substrato atingiu o maior valor de conversão (89,8 %) no TDH de 6 h. O biogás produzido foi composto de H2 e CO2, tendo o maior conteúdo de H2 registado (81,2 %) no TDH de 4 h. Os principais metabólitos solúveis obtidos foram ácido propiônico e 1,3-propanodiol com rendimentos máximos de 1,77 e 0,82 mol.molglicerol -1, respectivamente. Ambos os rendimentos máximos foram atingidos no TDH de 8 h. Em todas as fases apresentadas, ocorreu a predominância de ácido propiônico, sendo a maior porcentagem molar (96,9 %) atingida no TDH de 0,5 h. O segundo metabólito mais produzido foi o 1,3-propanodiol, alcançando maior porcentagem molar (29,4 %) no TDH de 6 h.

Este trabalho investigou a obtenção de filmes de óxido de cobalto por spray pirólise e sua caracterização para emprego como eletrocatalisador na geração de H2 por eletrólise de águas naturais via energia solar. A função desse eletrocatalisador é reduzir os sobrepotenciais necessários para eletrolisar a água e a decompor em hidrogênio e oxigênio. Para tanto, soluções precursoras de nitrato de cobalto hexahidratado foram depositadas por spray pirólise sobre uma camada de óxido de estanho dopado com flúor (FTO, em inglês) sobre um vidro sodocálcico, a diferentes concentrações e parâmetros de processo. Foram variadas a temperatura do substrato (de 190°C a 300°C), a distância entre o bico aspersor e o substrato (150 mm a 270mm). Os filmes de óxido de cobalto obtidos foram caracterizados quanto à sua cristalinidade por difração de raio-x, e quanto a sua morfologia por microscopia eletrônica de varredura. Os resultados mostraram uma forte influência da temperatura do substrato, relacionada com a natureza do solvente e do substrato, na obtenção de filmes contínuos e com aderência. Para avaliar seu desempenho na eletrólise da água, os filmes de óxido de cobalto obtidos foram ensaiados em uma célula eletroquímica, utilizando três águas distintas: água destilada, água do lago Guaíba (Porto Alegre-RS, Brasil) e do mar (Cidreira-RS, Brasil). Foi avaliada a sua eficiência na geração de hidrogênio e oxigênio, utilizando um voltâmetro de Hoffmann, pelo qual se obtinha o volume de gases gerados na eletrólise. A energia necessária para a separação da água foi fornecida por uma célula fotovoltaica exposta à radiação solar. Da mesma forma, foi avaliada sua atividade catalítica em função do tempo de eletrólise. Os resultados indicaram que os filmes eletrocatalisadores de óxido de cobalto obtidos por spray pirólise mostraram-se capazes de catalisar a eletrólise da água, baixando o sobrepotencial necessário, para todas as águas investigadas. A viabilidade de acoplar tal sistema de eletrólise de águas naturais a painéis fotovoltaicos mostrou-se viável e de grande interesse. Esta comprovação de geração de hidrogênio através de águas naturais define um curso para a implantação em larga escala de energia solar através de um mecanismo para o seu armazenamento como combustível. / This study investigated the obtaining of cobalt oxide films by spray pyrolysis and its characterization as electrocatalyst for use in the generation of H2 by electrolysis of natural water via solar energy. The function of this electrocatalyst is to reduce overpotentials needed to electrolyze water and decompose into hydrogen and oxygen. To this end, precursor solutions of cobalt nitrate hexahydrate were deposited by spray pyrolysis on a layer of fluorine-doped tin oxide (FTO) onto a soda lime glass at different concentrations and process parameters. The substrate temperature (190°C to 300 °C), the distance between the spray nozzle and the substrate (150 mm to 270mm) were varied. The films of cobalt oxide obtained were characterized for their crystallinity by x -ray diffraction, and by their morphology by scanning electron microscopy. The results showed a strong influence on the temperature of the substrate, linked to the nature of the solvent and substrate to obtain continuous films and adhesion. To assess their performance in the electrolysis of water, the films of cobalt oxide obtained were tested in an electrochemical cell using three different water: distilled water, lake water Guaiba (Porto Alegre - RS, Brazil) and the sea (Cidreira- RS, Brazil). We evaluated its effectiveness in the generation of hydrogen and oxygen, using a voltmeter Hoffmann, which was obtained by the volume of gas generated in the electrolysis. The energy required for water separation was supplied by a photovoltaic cell exposed to solar radiation. Similarly, we assessed the efficiency loss due to the electrolysis. The results indicated that the electrocatalyst cobalt oxide films obtained by spray pyrolysis were capable of catalyzing the electrolysis of water, lowering the overpotential required for all waters investigated. The feasibility of such a system of coupled natural water electrolysis photovoltaic panels proved to be feasible and of great interest. This proof of hydrogen generation through natural waters sets a course for the large-scale deployment of solar energy through a mechanism for storage as fuel.

Este trabalho investigou a obtenção de filmes de óxido de cobalto por spray pirólise e sua caracterização para emprego como eletrocatalisador na geração de H2 por eletrólise de águas naturais via energia solar. A função desse eletrocatalisador é reduzir os sobrepotenciais necessários para eletrolisar a água e a decompor em hidrogênio e oxigênio. Para tanto, soluções precursoras de nitrato de cobalto hexahidratado foram depositadas por spray pirólise sobre uma camada de óxido de estanho dopado com flúor (FTO, em inglês) sobre um vidro sodocálcico, a diferentes concentrações e parâmetros de processo. Foram variadas a temperatura do substrato (de 190°C a 300°C), a distância entre o bico aspersor e o substrato (150 mm a 270mm). Os filmes de óxido de cobalto obtidos foram caracterizados quanto à sua cristalinidade por difração de raio-x, e quanto a sua morfologia por microscopia eletrônica de varredura. Os resultados mostraram uma forte influência da temperatura do substrato, relacionada com a natureza do solvente e do substrato, na obtenção de filmes contínuos e com aderência. Para avaliar seu desempenho na eletrólise da água, os filmes de óxido de cobalto obtidos foram ensaiados em uma célula eletroquímica, utilizando três águas distintas: água destilada, água do lago Guaíba (Porto Alegre-RS, Brasil) e do mar (Cidreira-RS, Brasil). Foi avaliada a sua eficiência na geração de hidrogênio e oxigênio, utilizando um voltâmetro de Hoffmann, pelo qual se obtinha o volume de gases gerados na eletrólise. A energia necessária para a separação da água foi fornecida por uma célula fotovoltaica exposta à radiação solar. Da mesma forma, foi avaliada sua atividade catalítica em função do tempo de eletrólise. Os resultados indicaram que os filmes eletrocatalisadores de óxido de cobalto obtidos por spray pirólise mostraram-se capazes de catalisar a eletrólise da água, baixando o sobrepotencial necessário, para todas as águas investigadas. A viabilidade de acoplar tal sistema de eletrólise de águas naturais a painéis fotovoltaicos mostrou-se viável e de grande interesse. Esta comprovação de geração de hidrogênio através de águas naturais define um curso para a implantação em larga escala de energia solar através de um mecanismo para o seu armazenamento como combustível. / This study investigated the obtaining of cobalt oxide films by spray pyrolysis and its characterization as electrocatalyst for use in the generation of H2 by electrolysis of natural water via solar energy. The function of this electrocatalyst is to reduce overpotentials needed to electrolyze water and decompose into hydrogen and oxygen. To this end, precursor solutions of cobalt nitrate hexahydrate were deposited by spray pyrolysis on a layer of fluorine-doped tin oxide (FTO) onto a soda lime glass at different concentrations and process parameters. The substrate temperature (190°C to 300 °C), the distance between the spray nozzle and the substrate (150 mm to 270mm) were varied. The films of cobalt oxide obtained were characterized for their crystallinity by x -ray diffraction, and by their morphology by scanning electron microscopy. The results showed a strong influence on the temperature of the substrate, linked to the nature of the solvent and substrate to obtain continuous films and adhesion. To assess their performance in the electrolysis of water, the films of cobalt oxide obtained were tested in an electrochemical cell using three different water: distilled water, lake water Guaiba (Porto Alegre - RS, Brazil) and the sea (Cidreira- RS, Brazil). We evaluated its effectiveness in the generation of hydrogen and oxygen, using a voltmeter Hoffmann, which was obtained by the volume of gas generated in the electrolysis. The energy required for water separation was supplied by a photovoltaic cell exposed to solar radiation. Similarly, we assessed the efficiency loss due to the electrolysis. The results indicated that the electrocatalyst cobalt oxide films obtained by spray pyrolysis were capable of catalyzing the electrolysis of water, lowering the overpotential required for all waters investigated. The feasibility of such a system of coupled natural water electrolysis photovoltaic panels proved to be feasible and of great interest. This proof of hydrogen generation through natural waters sets a course for the large-scale deployment of solar energy through a mechanism for storage as fuel.

Différents systèmes polyoxométallates@M-colorants ont été réalisés dans cette thèse pour électrochimique dégagement d'hydrogène catalytique et génération photocourant.• Des films hybrides, basés sur des interactions électrostatiques entre une porphyrine tetracationique et des nanoparticules stabilisées par des POMs du type POM@Pt sur ITO, ont été formés par la méthode dite couche par couche et ont été utilisés pour la génération de H2 ou de photocourant. • Pour améliorer le transfert de charge entre les nanoparticules POM@M et le substrat, la réduction de l'oxyde de graphène a été réalisée pour former des systèmes hybrides rGO/POM@Pt. Le dégagement d'hydrogène a été mesuré.• Les copolymères polycationiques bis-porphyrine ont également été obtenus par électropolymérisation avec des espaceurs bis-pyridinium. Par réaction de métathèse, l’incorporation avec divers POM de type Keggin ou des nanoparticules du type POM@Ag ont ensuite été realise. Leurs performances photovoltaïques ont ensuite été étudiées.• Enfin des films hybrides PEDOT dopés avec des nanoparticules du type POM@M ont également été fabriqués. Les performances photovoltaïques ont été examinés montrant une forte amélioration sous illumination dans le domaine du visible. L’ensemble de ces matériaux hybrides ont montré des propriétés intéressantes pour des applications photovoltaïques et la conversion d'énergie. / Polyoxometalates@M NPs-dyes molecular hybrid systems were realized in this thesis for electrochemical catalytic hydrogen evolution and photocurrent generation. • First, hybrid films, based on electrostatic interactions between the tetracationic porphyrin and POMs@Pt NPs composites on ITO slides, were formed by the so called Layer-by-Layer method for HER and photocurrent generation.• To improve the charge transfer between POMs@M NPs and the substrate, reduced graphene oxide was introduced to form rGO/POMs@Pt NPs hybrid systems. Hydrogen evolution was measured after dropping this composites onto the surface of glassy carbon electrodes.• Polycationic bis-porphyrin copolymers have been also obtained by an electropolymerization leading to the formation of new bis-porphyrin copolymers with pyridinium as spacers. Incorporation with various Keggin type POMs or POMs@Ag was then achieved, their photovoltaic performances were also studied.• POMs@M NPs doped PEDOT hybrids films have been also fabricated. The photovoltaic performances has been examined showing particularly strong enhancement under visible light. In conclusion, these polyoxometalates based hybrids materials have shown interesting properties for photovoltaic application and energy conversion.

In this thesis we test and expand our current knowledge of Star Formation Laws (SF laws) in the extreme environment of dwarf irregular galaxies. We focus on the SF characteristics of our 18 galaxies sample, extending current investigations of the Schmidt-Kennicutt law to the low luminosity, low metallicity regime. The Hi data used in this project have been observed, calibrated and imaged according to the LITTLE THINGS Survey prescription to which I brought my own contribution as a member of the team. Apart from high resolution, VLA data in B, C and D array configurations, this project makes use of an extensive set of multi- wavelength data (H , FUV, 24 m, 3.6 m, V-band and K-band). Molecular gas in dwarfs is very difficult to observe, mainly because due to the low metallicity environment, we lose our only molecular tracer, the CO which becomes under luminous. Therefore the gas distribution is represented by Hi gas only. We create our Star Formation Rate (SFR) maps mainly based on FUV maps because our analysis shows that FUV is the SF tracer that allows us the most extensive sampling of the SFR surface density (SFRD) and Hi surface density relation. The main results of our study are: Whereas in spiral galaxies Bigiel et al. (2008) have found a one to one relation between star formation rate and molecular gas and no relation between the SFR and the neutral gas, in a small sample of dwarfs as well as in the outskirts of spiral galaxies Bigiel et al. (2010b) has found that SFRD does correlate with Hi surface density. We confirm the existence of the SFRD vs. Hi surface density relation in dwarf irregular galaxies and a linear fitting through all our data (all 18 galaxies combined) yields a power law relation ΣSFR ∝ Σ1.87±0.3/HI . We find that the interiors of Hi shells, at 400 pc scales, become resolved and show up in SFRD versus Hi surface density plots although within the shell interior we have SFRD values but no Hi surface density related to them. Thus, the points originating from those regions contribute significantly to the increase of the scatter in the plot. We show that by excluding those points the correlation between SFRD and Hi surface density improves between 10% and 20%. Eight of the 18 galaxies in our sample have Hi maxima higher than the 10M pc-2 value found by Bigiel et al. (2008) for spiral galaxies. Krumholz et al. (2011) predicted that the 10M pc-2 threshold is metallicity dependent in galaxies with sub-solar metallicity, however the theoretically predicted values for our galaxies only match the observed Hi maxima in one case (DDO168). We find that metallicity cannot be the only factor setting the Hi to H2 transition. In fact, we find evidence that the higher the interstellar radiation field (ISRF), the higher the Hi maximum is, hence we suggest that the ISRF should also be taken into consideration in predicting the Hi to H2 transition threshold. We find that even tighter than the SFRD vs. Hi surface density relation is the SFRD vs. V-band surface density relation. Unlike the SFRD vs. Hi surface density relation the SFRD vs. V-band surface density relation follows a power law and can be written as follows: ΣSFR ∝ (10^μv)^-0.43±0.03. The SFRD vs. V-band surface density relation suggests that the existing stars also play a role in the formation of the next generation of stars. Within our sample of dwarf galaxies the average pressure per resolution element and the SFRD are in a 1:1 linear relation: ΣSFR ∝ P_h^1.02±0.05. A similar relation has been found by Blitz & Rosolowsky (2006) for the low-pressure regimes of spiral galaxies. In conclusion we find that in the extreme environments of dwarf galaxies the metal deficiency and the lack of the classic SF stimulators (spiral arms, shear motions) do not impede the star forming process. In these galaxies, dust-shielding becomes predominantly self-shielding and there is plenty of Hi available to achieve this additional task. Existing stars assume the role of pressure enhancers, which in turn will stimulate SF without the need of spiral arms or shear motion.

Les piles à combustible, alimentée par de l’hydrogène, représentent une solution prometteuse pour limiter la pollution. L’une des alternatives économiques envisagées à court et moyen terme est de produire l’hydrogène à partir d’un carburant tel que le méthane ou le bio-éthanol. Cette transformation a pour objectif d’obtenir un mélange de gaz riche en hydrogène avec une très faible teneur en CO, ce dernier étant un poison pour les piles de type PEM. La réaction de Water-Gas Shift (WGS) est une étape clé du procédé ; elle convertit CO en CO2 par réaction avec l’eau et fournit une quantité d’hydrogène supplémentaire. Des catalyseurs métalliques (Pt, Pd, Ru, Rh, Au, Cu) supportés sur des oxydes (CeO2, TiO2, ZrO2, Fe2O3, CeO2/Al2O3) ont été comparés dans des conditions de WGS identiques en présence de CO2 et H2. Une étude cinétique a été réalisée sur les catalyseurs Pt/CeO2, Au/CeO2, Pt/TiO2 et Au/TiO2. Les énergies d’activation apparentes et les ordres de réaction ont été déterminés à partir d’un modèle de type loi de puissance. Un mécanisme réactionnel avec deux sites a été proposé pour décrire les différentes activités des 4 catalyseurs. Des expériences de désorption programmée en température ont été réalisées pour déterminer les paramètres cinétiques sur le support / The Fuel Cells are promising solution to reduce the air pollution. One of the cost-efficient alternatives is to produce hydrogen from another fuel such as methane or bio-ethanol. A hydrogen fuel processor consists in generating a hydrogen-rich mixture and reducing the carbon monoxide content, as PEM fuel cells are very low CO tolerance. One of these units is the water-gas shift reactor, which converts CO into CO2 by the reaction with water and provides additional hydrogen. Catalysts based on a metal (Pt, Pd, Ru, Rh, Au, Cu) supported on an oxide (CeO2, TiO2, ZrO2, Fe2O3, CeO2/Al2O3) were compared for the WGS reaction in the same conditions and in the presence of CO2 and H2. A kinetic study was conducted on catalysts Pt/CeO2, Au/CeO2, Pt/TiO2 and Au/TiO2. A power law rate model was used to determine apparent activation energies and reaction orders. A dual-site reaction mechanism was proposed to explain the different activities between the four catalysts. The sorption parameters of H2O and CO2 on the supports was quantitatively determined from temperature-programmed desorption experiments

Le carbone présente de nombreuses formes allotropiques, dont le graphite, qui possède une large variété de formes géométriques d'intérêt pour l'industrie. Ce travail de thèse a permis la synthèse d'une nouvelle de ces formes: les pyramides hexagonales. Ces cristaux submicroniques sont créés à partir de substrats de graphite par gravure en plasma radiofréquence (rf) Ar/H2 basse pression. Pour comprendre la formation de ces nouveaux cristaux, la caractérisation des plasmas a été effectuée par sondes de Langmuir et absorption résonante laser afin de vérifier la température de surface et d'estimer les flux et énergies des ions. L'évolution temporelle de la gravure a été directement observée en microscopie électronique à balayage (MEB). La gravure chimique (Ar/H2) a formé des cônes de graphite à hélices dont les paramètres cristallins et une amorphisation de surface, due à l'hydrogène, ont été révélés par microscopie électronique en transmission (MET). La vitesse de gravure et l'état de surface montrent, en fonction du mélange, une zone de transition caractérisée par l'absence de structures. La gravure physique (Ar pur) conduit à la création des pyramides hexagonales de graphite. Un modèle de formation de ces cristaux a pu être proposé grâce à une bonne connaissance des différentes conditions plasma et des études poussées de microscopies électroniques sur plusieurs types de substrats. Les analyses MET haute résolution ont montré des boucles fermant les plans de bord du cristal et liées à sa formation. Nous avons également maîtrisé l'état de surface des substrats de graphite hautement orienté (HOPG) en créant une densité homogène de pyramides dont la taille peut être contrôlée. / Carbon occurs as many different allotropic forms. One in particular, graphite, exhibits a remarkable variety of geometrical configurations largely used in industrial applications. This work permitted the synthesis of a novel crystalline form: the hexagonal-pyramidal graphite hillocks. These submicronic structures are created from graphite substrates by low pressure Ar/H2 radiofrequency (rf) plasma etching. In order to understand the formation of these new crystals, plasma characterization has been carried out by Langmuir probes and laser absorption spectroscopy to check the surface temperature and estimate the ion fluxes and energies. Etching kinetics has been directly observed by scanning electron microscopy (SEM). Chemical etching processes in pure hydrogen resulted in the creation of helical graphite cones whose crystal parameters and surface amorphisation have been revealed by transmission electron microscopy (TEM). The etching rate and surface topography as function of the gas mixture show a transition where no structures are created. The physical etching in pure argon creates hexagonal-pyramidal graphite hillocks. A formation model of these crystals has been proposed owing to a good knowledge of the different plasma conditions and thorough electron microscopy studies on two kinds of substrates. High resolution MET analyses showed graphene loops closing the edges planes along the crystal facets and related to the structure’s formation. We also showed the texturing of the surface of highly ordered graphite (HOPG) by creating a high and homogeneous density of crystals whose size may be controlled

Le développement de technologies de l’énergie alternatives à la combustion des ressources fossiles est un enjeu majeur pour réduire l’émission des gaz à effet de serre et développer une économie durable. Dans cette optique, les piles à combustible à membrane échangeuses de protons (PEMFC) utilisent le platine en tant que catalyseur pour transformer l’énergie chimique en énergie électrique, en réduisant l’oxygène de l’air en eau et en oxydant l’hydrogène en protons. Dans la nature, les enzymes à cuivre et les hydrogénases catalysent respectivement ces réactions. Ces dernières, ainsi que des complexes bio-inspirés de leur site actif, ont été envisagés en tant qu’alternatives au platine, métal noble et coûteux. Ainsi, un complexe mononucléaire bisdiphosphine de nickel renfermant des acides aminés arginines en troisième sphère de coordination a été immobilisé sur une matrice de nanotubes de carbone (NTCs). Cette anode a démontré d’excellentes performances pour oxyder l’hydrogène avec des densités de courant élevées et sur une large gamme de pH. Son utilisation dans une PEMFC a permis d’obtenir une densité de puissance de 15 mW.cm-2, seulement cinq fois inférieure à celle d’une pile classique à base de platine préparée dans les mêmes conditions. Concernant la catalyse de réduction de l’oxygène, des méthodes covalentes ont été développéespour réaliser la connexion électronique directe de laccase de Trametes sp C30, ainsi qu’un mutant de cetten enzymesur matrice de NTCs L’’association du catalyseur de nickel avec une cathode à base de bilirubine oxydase immobilisée sur NTCs a permis de proposer un nouveau concept de pile hybride enzymatique/bio-inspirée. Une densité de puissance de l’ordre de 1,8 mW.cm-2 et une force électromotrice proche de 1V ont ainsi été mesurées pour cette pile sans métaux nobles. Le greffage de complexes de cuivre mono- et dinucléaires, bio-inspirés du site actif d’enzymes à cuivre et actifs vis-à-vis de la réduction de l’oxygène a enfin permis d’élaborer la première pile H2/air ne renfermant que des catalyseurs moléculaires et sans métaux nobles. Cette dernière délivre une densité de puissance de 160 µW.cm-2. / New energy technologies alternative to fossil fuels utilization is a key issue to mitigate greenhouse gases emission and develop a sustainable economy. In this context, platinum-based proton exchange membrane fuel cells use oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) to convert chemical energy into electrical energy. In nature multicopper oxidases and hydrogenases catalyze these two reactions, respectively. These enzymes and corresponding bioinspired catalysts have been used as alternatives to the rare and expensive platinum metal. First, a mononuclear bis-diphosphine nickel complex surrounded by arginine residues was immobilized onto carbon nanotubes (CNTs) and demonstrated excellent performances for HOR developing high current densities over a wide range of pH. This anode was integrated in a PEMFC, which achieved high power densities (15 mW cm-2), only five times lower as compared to classical PEMFC prepared under similar conditions. Regarding ORR catalysis, we covalently grafted LLaccases from Trametes sp C30 multicopper oxidases onto NTCs electrodes and achieved direct electron transfer. Using, bilirubin oxidase deposited on CNTs at the cathode side, we proposed a new concept of hybrid enzymatic/bio-inspired H2/air fuel cell. This hydrogen fuel cell delivered 1.8 mW.cm-2 and a high open circuit voltage of 1V. Finally, various copper complexes inspired from the active sites of copper enzymes were assessed for ORR and the first H2/air fuel cell containing noble metal-free molecular catalysts at both electrodes is reported, achieving 160 µW.cm-2 power density.