Drei Wasserstoffgenerator-Systeme (WGS) auf Basis chemischer Hydride wurden in dieser Arbeit als Labormuster ausgelegt, gefertigt und in ihren Betriebseigenschaften analysiert. Es wurden ein 20 W-WGS und zwei 100 W-WGS untersucht. Als chemische Hydride wurden Amminboran und Natriumborhydrid ausgewählt. Aufgrund ihrer vergleichsweise einfachen Lagerfähigkeit, ihren moderaten Freisetzungsbedingungen und ihrer volumetrisch wie gravimetrisch hohen Wasserstoffdichten erschienen sie in besonderer Weise geeignet für Wasserstoffgeneratoren im Kleinleistungsbereich. Zwar zeigen diese chemischen Hydride zurzeit hinsichtlich ihrer Kosten, ihrer Energieeffizienz bei der Herstellung und ihrer Umweltverträglichkeit keine Vorteile gegenüber verdichtetem Wasserstoff, jedoch besitzen sie mit ihrer hohen, auf das Hydrid bezogenen Energiedichte ein positives Alleinstellungsmerkmal. Bei der Entwicklung der WGS standen daher neben der Betriebszuverlässigkeit und Regelbarkeit die Optimierung der systembezogenen Energiedichte WGS im Fokus.

The development of new storage materials will facilitate the use of hydrogen as a major energy carrier in near future. Among the chemical hydrides used as hydrogen storage materials for supplying hydrogen at ambient temperature, sodium borohydride seems to be an ideal one because it is stable under ordinary conditions and liberates hydrogen gas in a safe and controllable way in aqueous solutions. However, self hydrolysis of sodium borohydride is so slow that requires a suitable catalyst. This work aims the use of water dispersible cobalt(0) nanoclusters having large portion of atoms on the surface as catalyst for the hydrolysis of sodium borohydride. In-situ formation of cobalt(0) nanoclusters and catalytic hydrolysis of sodium borohydride were performed starting with a cobalt(II) chloride as precursor and sodium borohydride as reducing agent and substrate in the presence of a water soluble stabilizer. As stabilizer, water soluble polyacrylic acid as well as hydrogen phosphate ion were tested. Cobalt(0) nanoclusters were characterized by using all the available analytical methods including FT-IR, TEM, XPS, UV-visible electronic absorption spectroscopy. The kinetics of cobalt(0) nanoclusters catalyzed hydrolysis of sodium borohydride were studied depending on the catalyst concentration, substrate concentration, stabilizing agent concentration and temperature.

Fuel cells are electricity generators which convert chemical energy of hydrogen directly to electricity by means of electrochemical oxidation and reduction reactions. A single proton exchange membrane (PEM) fuel cell can only generate electricity with a potential between 0.5V and 1V. The useful potential can be achieved by stacking cells in series to form a PEM fuel cell stack. There is a potential to utilize 100W class fuel cells. Fuelling is the major problem of the portable fuel cells. The aim of this thesis is to design and manufacture a PEM fuel cell stack which can be used for portable applications. The PEM fuel cell stack is planned to be incorporated to a NaBH4 hydrolysis reactor for H2 supply. Within the scope of this thesis a new coating technique called &ldquo / ultrasonic spray coating technique&rdquo / is developed for membrane electrode assembly (MEA) manufacturing. New metal and graphite bipolar plates are designed and manufactured by CNC technique. A fuel cell controller hardware is developed for fuel supply and system control. The power densities reached with the new method are 0.53, 0.74, 0.77, and 0.88 W/cm2 for 20%, 40%, 50%, 70% Pt/C catalyst by keeping 0.4mg Pt/cm2 platinum loading constant, respectively. The power density increase is 267% compared to &ldquo / spraying of catalyst ink with air pressure atomizing spray gun&rdquo / . All parts of the PEM fuel cell stack designed were produced, assembled, and tested. The current density reached is 12.9A at 12 V stack potential and the corresponding electrical power of the stack is 155W.

The three main components of wood, namely, cellulose, hemicellulose, and lignin, can be used in various areas. However, since lignin covalently crosslinks with wood polysaccharides creating networks that is an obstacle for extraction, direct extraction of different wood components in high yield is not an easy matter. One potential approach to overcome such obstacles is to treat the wood with specific enzymes that degrade the networks by specific catalysis. However, the structure of wood is so compact that the penetration of the wood fibers by large enzyme molecules is hindered. Thus, the pretreatment of wood prior to the application of enzymes is necessary, for “opening” the structure. One pretreatment method that was performed in this thesis is based on kraft pulping, which is a well-established and industrialized technique. For untreated wood, the wood fibers cannot be attacked by the enzymes. A relatively mild pretreatment was sufficient for wood polysaccharides hydrolyzed by a culture filtrate. A methanol-alkali mixture extraction was subsequently applied to the samples that were pretreated with two types of hemicellulases, Gamanase and Pulpzyme HC, respectively. The extraction yield increased after enzymatic treatment, and the polymers that were extracted from monocomponent enzyme-treated wood had a higher degree of polymerization. Experiments with in vitro prepared lignin polysaccharide networks suggested that the increased extraction was due to the enzymatic untying. However, the relatively large loss of hemicellulose, particularly including (galacto)glucomannan (GGM), represents a problem with this technique. To improve the carbohydrate yield, sodium borohydride (NaBH4), polysulfide and anthraquinone were used, which increased the yields from 76.6% to 89.6%, 81.3% and 80.0%, respectively, after extended impregnation (EI). The additives also increased the extraction yield from approximately 9 to 12% w/w wood. Gamanase treatment prior to the extraction increased the extraction yield to 14% w/w wood. Sodium dithionite (Na2S2O4) is an alternative reducing agent for the preservation of hemicelluloses because it is less expensive than metal hydrides and only contains sodium and sulfur, which will not introduce new elements to the recovery system. Moreover, Na2S2O4has the potential to be generated from black liquor. Na2S2O4 has some preservation effect on hemicelluloses, and the presence of Na2S2O4 also contributed to delignification. The extraction yield increased to approximately 15% w/w wood. Furthermore, Na2S2O4 has been applied in the kraft pulping process of spruce. The yield and viscosity increased, while the Klason lignin content and kappa number decreased, which represents a beneficial characteristic for kraft pulp. The brightness and tensile strength of the resulting sheets also improved. However, the direct addition of Na2S2O4 to white liquor led to greater reject content. This problem was solved by pre-impregnation with Na2S2O4 and/or mild steam explosion (STEX) prior to the kraft pulping process. Following Na2S2O4 pre-impregnation and mild STEX, the obtained kraft pulp had substantially better properties compared with the properties exhibited after direct addition of Na2S2O4 to the white liquor. The wood structure opening efficiency of mild STEX alone was also tested. The accessibility of the wood structure to enzymes was obtained even at very modest STEX conditions, according to a reducing sugar analysis, and was not observed in untreated wood chips, which were used as a reference. The mechanical effect of STEX appears to be of great importance at lower temperatures, and both chemical and mechanical effects occur at higher STEX temperatures. / <p>QC 20140903</p>

Sodium borohydride is stable in alkaline solution, however, it hydrolyses and generates hydrogen gas in the presence of suitable catalyst. By this way hydrogen can be generated safely for the fuel cells. All of the catalyst having been used in the hydrolysis of sodium borohydride, with one exception, are heterogeneous. The limited surface area of the heterogeneous and therefore, have limited activity because of the surface area. Thus, the use of metal nanoclusters as catalyst with large surface area is expected to provide a potential route to increase the catalytic activity. In this dissertation we report for the first time the use of ruthenium(0) nanoparticles as catalyst in the hydrolysis of sodium borohydride. The water dispersible ruthenium(0) nanoparticles were prepared by the reduction of RuCl3.xH2O with sodium borohydride and were stabilized by three different ligands dodecanethiol, ethylenediamine and acetate. Among these three colloidal materials the acetate stabilized ruthenium(0) nanoparticles were found to have the highest catalytic activity in catalyzing the hydrolysis of sodium borohydride. The acetate stabilized ruthenium(0) nanoparticles were characterized by tranmission electron microscopy (TEM), X-ray photoelectron spectroscopy and FT-IR spectroscopy. The particle size of the acetate stabilized ruthenium(0) nanoparticles was determined to be 2.62&plusmn / 1.18 nm from the TEM analysis. The kinetic of the ruthenium(0) nanoparticles catalyzed hydrolysis of sodium borohydride was studied depending on the catalyst concentration, substrate concentration and temperature. The activation parameters of this reaction were also determined from the evaluation of the kinetic data. This catalyst provides the lowest activation energy ever found for the hydrolysis of sodium borohydride.

The development of new storage materials will facilitate the use of hydrogen as a major energy carrier in near future. In hydrogen economy, chemical hydrides such as NaBH4, KBH4, LiH, NaH have been tested as hydrogen storage materials for supplying hydrogen at ambient temperature. Among these chemical hydrides, sodium borohydride seems to be an ideal hydrogen storage material because it is stable under ordinary conditions and liberates hydrogen gas in a safe and controllable way in aqueous solutions. However, self hydrolysis of sodium borohydride is so slow that it requires a suitable catalyst. All of the prior catalysts tested for the hydrolysis of sodium borohydride are heterogeneous and, therefore, have limited activity because of the small surface area. Here, we report for the first time the employment of water dispersible metal(0) nanoclusters having a large portion of atoms on the surface as a catalyst for the hydrolysis of sodium borohydride. In-situ formation of nickel(0) nanoclusters and catalytic hydrolysis of sodium borohydride were performed in the same medium. Nickel(0) nanoclusters are prepared from the reduction of nickel(II) acetylacetonate by sodium borohydride in aqueous solution and stabilized with hydrogenphosphate anions. The nickel(0) nanoclusters were characterized by using XPS, Powder XRD, FT-IR, UV-Vis and NMR spectroscopic methods. The kinetics of the nickel(0) nanoclusters catalyzed hydrolysis of sodium borohydride was studied depending on the catalyst concentration, substrate concentration, stabilizing agent concentration and temperature. Tha kinetic study shows that the nickel(0) nanocluster-catalyzed hydrolysis of sodium borohydride is first order with respect to catalyst concentration and zero order with respect to substrate concentration The activation parameters of this reaction were also determined from the evaluation of the kinetic data. The hydrogenphosphate-stabilized nickel(0) nanoclusters provide a lower activation energy (Ea= 55 kJ/mol) than bulk nickel (Ea=73 kJ/mol) for the hydrolysis of sodium borohydride.

L’hydrolyse spontanée du NaBH4 en milieu aqueux est une réaction lente nécessitant l’emploi d’un catalyseur pour l’accélérer. Nous présentons ici l’élaboration de catalyseurs Co supporté sur αAl2O3 mis forme de films, plus appropriés pour des applications nécessitant un démarrage/arrêt à la demande de la génération d’H2. Les films sont déposés sur un substrat Cu par dépôt électrophorétique (DEP). Par ailleurs, des catalyseurs Co supporté sur différentes argiles naturelles (Kaolinite, Illite-A et Illite-B) en provenance du Liban ont été élaborés. Le Co a été déposé sur αAl2O3 par six voies différentes : 1. Imprégnation de Co sur film αAl2O3 ; 2. Précipitation de Co sur film αAl2O3; 3. Electrodéposition du Co sur film αAl2O3; 4. Codéposition du Co et de αAl2O3; 5. Codéposition de nanoparticules de Co et de αAl2O3 et 6. DEP de Co-αAl2O3. La voie 6 est la meilleure pour l’élaboration des films 1, 5, 10 et 15 mass.% Co-αAl2O3. Ces films (homogènes) et les catalyseurs Co-αAl2O3 ont été comparés pour leur réactivité et l’étude cinétique a donné des énergies apparentes d’activation identiques: 51.3 et 52.7 kJ mol-1, respectivement.Ensuite, des catalyseurs de 1, 5, 10 et 15 mass.% Co-argile ont été élaborés selon le même procédé que celui de Co-αAl2O3. Ces catalyseurs ont montré une réactivité pour l’hydrolyse du NaBH4, donnant notamment des énergies apparentes d’activation de 58.8, 51.5 et 58.1 kJ mol-1 pour 15 mass.% Co-Kaolinite, (Illite-A) et (Illite-B) respectivement. De plus, des films homogènes de 1, 5, 10 et 15 mass.% Co-Kaolinite ont été déposés avec succès sur Inox par DEP. Cette étude a montré le potentiel de ces argiles naturelles comme supports de catalyseur / NaBH4 hydrolysis reaction is slow in aqueous medium. Therefore, it can be accelerated by addition of a catalyst. In this work, catalytic films of Co supported over αAl2O3 have been synthesized since they are more convenient for applications requiring generation of H2 on demand. Co-αAl2O3 films were deposited on Cu plates by electrophoretic deposition method (EPD). Furthermore, catalysts of Co supported over different types of natural clay (Kaolinite, Illite-A and Illite-B) provided from Lebanon were also synthesized.Co was deposited over αAl2O3 following six routes: 1. αAl2O3 film impregnation; 2. Co precipitation over αAl2O3 film; 3. Co electrodeposition over αAl2O3 film; 4. Coelectrodeposition of Co from CoCl2 and αAl2O3; 5. Coelectrodeposition of Co nanoparticles and αAl2O3 and 6. EPD of Co-αAl2O3. Route 6 was found to be the best one for the fabrication of homogeneous films of 1, 5, 10 and 15 wt.% Co-αAl2O3. A comparative study on the reactivity of Co-αAl2O3 films and powder catalysts was done and the kinetic study gave similar values of the apparent activation energies: 51.3 and 52.7 kJ mol-1, respectively. Moreover, Co was supported over clay with the same method used for Co-αAl2O3. 1, 5, 10 and 15 wt.% Co-clay catalysts were tested for the hydrolysis reaction and the apparent activation energies obtained were as follows: 58.8, 51.5 and 58.1 kJ mol-1 for 15 wt.% Co-Kaolinite, (Illite-A) and (Illite-B) respectively. Homogeneous films of 1, 5, 10 and 15 wt.% Co-Kaolinite were successfully deposited over Inox substrate by EPD. It was concluded from this work that natural clays can be used as potential supports for Co catalysts in the hydrolysis of NaBH4

Os cações são importantes recursos pesqueiros que podem apresentar concentrações de mercúrio (Hg) e arsênio (As) muitas vezes acima do limite de tolerância, o que os tornam impróprios como alimento. No meio aquático estes contaminantes são convertidos em espécies orgânicas, em especial metilmercúrio (MeHg) e arsenobetaína (AB), respectivamente. O MeHg é neurotóxico, sendo o sistema nervoso em desenvolvimento o mais susceptível. A AB é pouco tóxica, no entanto, o As inorgânico está envolvido em processos de estresse oxidativo, mutagênese e principalmente carcinogênese. Neste trabalho, foi avaliada a eficiência da cisteína na remoção de Hg, a ocorência de As total e inorgânico, e a redução de sua concentração com o emprego de borohidreto de sódio e de preparos para o consumo. A redução máxima de Hg, de 59,4%, com cisteína a 0,5% em pH 5,0, não foi reproduzida quando pretendida a reutilização da solução do aminoácido, importante do ponto de vista prático. O cação-azul continha elevados níveis de As total, 1,98 a 22,56 &#181;g/g (base úmida), que foram removidos com borohidreto de sódio em 99%, demonstrando a alta potencialidade do método usado. O As inorgânico, presente na quantidade média de 0,0086 &#181;g/g (base úmida), foi reduzido em 27,7%. O preparo para o consumo, por cozimento em água, do cação-azul em cubos (1-2 cm3), resultou em maior remoção de As total, de 65,9 a 71,2%; no cação grelhado a redução foi de 55,4 a 60,2%. As amostras, grelhadas ou cozidas, adicionadas de sal e limão enriquecido com ácido ascórbico, e as grelhadas contendo sal e sal com limão, apresentaram redução na concentração de As inorgânico de 30,1 a 42,8%. / The shark are important fishery resources that may have concentrations of mercury (Hg) and arsenic (As) often above the limit of tolerance, which makes them unsuitable as food. In the aquatic environment these contaminants are converted to organic species, particularly methylmercury (MeHg) and arsenobetaína (AB), respectively. The MeHg is neurotoxic, and the developing nervous system more susceptible. AB is slightly toxic, however, the inorganic As is involved in processes of oxidative stress, mutagenesis and carcinogenesis mainly. In this study, we evaluated the efficiency of cysteine to remove mercury, the occurrence of the total and inorganic As, and the reduction of their concentration with the use of sodium borohydride and preparations for consumption. The maximum reduction of Hg, 59.4%, with 0.5% cysteine at pH 5.0, was not reproduced when you want to reuse the solution of the amino acid, important practical point of view. The blue-shark contained high levels of the total As, 1.98 to 22.56 &#181;g/g (wet weight), which were removed with sodium borohydride in 99%, demonstrating the high potential of the method used. The inorganic As, present in the average amount of 0.0086 &#181;g/g (wet weight) was reduced in 27.7%. Preparation for consumption by baking in water, the blue-shark into cubes (1-2 cm3) resulted in greater removal of the total As, 65.9 to 71.2%; in the grilled shark the reduction was 55,4 to 60.2%. The samples, grilled or baked, added salt and lemon enriched with ascorbic acid, and the grilled containing salt and salt with lemon, presented reduction in the concentrations of inorganic As from 30.1 to 42.8%.

Metal nanoclusters exhibit unique properties which differ from their bulk materials, owing to the quantum size effects. For example, the catalytic activity of transition metal nanoclusters generally increases with decreasing particle size. However, nanoclusters tend to be fairly unstable with respect to the agglomerate into bulk metal in solution and thus special precautions have to be taken to avoid their aggregation or precipitation during the preparation of such nanoclusters in solution. In order to obtain stable nanoclusters dispersed in solution, a stabilizing agent is usually added into the reaction system. The stabilization of metal nanoclusters in solution can be achieved either by electrostatically by using charged ions such as acetate ion or sterically by long chain molecules such as polymers. Polymers are one of the most widely used steric stabilizers for the preparation of stable metal nanoclusters in solution. The use of polymers as stabilizer for the synthesis of transition metal nanoclusters provides advantegous regarding solubility, conductivity, thermal stability and reusability. The metal nanoclusters stabilized by polymers generally show higher catalytic activity, stability and optical properties. In this dissertation we report the preparation and characterization of water soluble polymer stabilized transition metal(0) (metal= Ni, Co and Ru) nanoclusters and their v catalysis in hydrogen generation from the hydrolysis of sodium borohydride (NaBH4) and ammonia borane (AB) which are the best candidates as chemical hydrogen storage materials for on-board applications. The water soluble polymer stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters were prepared by using two different facile methods / (i) the reduction of metal precursors by sodium borohydride in the presence poly(N-vinyl pyrrolidone) (PVP) in methanol solution after 1h reflux, (ii) the in situ generation during the hydrolysis of ammonia borane in the presence of poly(4-styrene sulfonicacid-co-maleic acid) (PSSA-co-MA). The characterization of both type of polymer stabilized transition metal(0) nanoclusters were done by using UV-Visible electronic absorption spectroscopy (UV-Vis), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and FT-IR techniques. The catalytic activity of PVP stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters was tested in the hydrolysis of NaBH4 and AB. The catalytic acitivity of PSSA-co-MA stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters was tested only in the hydrolysis of AB in which they were in situ generated. The kinetics of hydrogen generation from both hydrolysis reactions in the presence PVP or PSSA-co-MA stabilized nickel(0), cobalt(0) and ruthenium(0) nanoclusters were studied depending on the polymer to metal ratio, catalyst concentration, substrate concentration and temperature as well as the activation parameters (Arrhenius activation energy (Ea), activation enthalpy (

Os cações são importantes recursos pesqueiros que podem apresentar concentrações de mercúrio (Hg) e arsênio (As) muitas vezes acima do limite de tolerância, o que os tornam impróprios como alimento. No meio aquático estes contaminantes são convertidos em espécies orgânicas, em especial metilmercúrio (MeHg) e arsenobetaína (AB), respectivamente. O MeHg é neurotóxico, sendo o sistema nervoso em desenvolvimento o mais susceptível. A AB é pouco tóxica, no entanto, o As inorgânico está envolvido em processos de estresse oxidativo, mutagênese e principalmente carcinogênese. Neste trabalho, foi avaliada a eficiência da cisteína na remoção de Hg, a ocorência de As total e inorgânico, e a redução de sua concentração com o emprego de borohidreto de sódio e de preparos para o consumo. A redução máxima de Hg, de 59,4%, com cisteína a 0,5% em pH 5,0, não foi reproduzida quando pretendida a reutilização da solução do aminoácido, importante do ponto de vista prático. O cação-azul continha elevados níveis de As total, 1,98 a 22,56 &#181;g/g (base úmida), que foram removidos com borohidreto de sódio em 99%, demonstrando a alta potencialidade do método usado. O As inorgânico, presente na quantidade média de 0,0086 &#181;g/g (base úmida), foi reduzido em 27,7%. O preparo para o consumo, por cozimento em água, do cação-azul em cubos (1-2 cm3), resultou em maior remoção de As total, de 65,9 a 71,2%; no cação grelhado a redução foi de 55,4 a 60,2%. As amostras, grelhadas ou cozidas, adicionadas de sal e limão enriquecido com ácido ascórbico, e as grelhadas contendo sal e sal com limão, apresentaram redução na concentração de As inorgânico de 30,1 a 42,8%. / The shark are important fishery resources that may have concentrations of mercury (Hg) and arsenic (As) often above the limit of tolerance, which makes them unsuitable as food. In the aquatic environment these contaminants are converted to organic species, particularly methylmercury (MeHg) and arsenobetaína (AB), respectively. The MeHg is neurotoxic, and the developing nervous system more susceptible. AB is slightly toxic, however, the inorganic As is involved in processes of oxidative stress, mutagenesis and carcinogenesis mainly. In this study, we evaluated the efficiency of cysteine to remove mercury, the occurrence of the total and inorganic As, and the reduction of their concentration with the use of sodium borohydride and preparations for consumption. The maximum reduction of Hg, 59.4%, with 0.5% cysteine at pH 5.0, was not reproduced when you want to reuse the solution of the amino acid, important practical point of view. The blue-shark contained high levels of the total As, 1.98 to 22.56 &#181;g/g (wet weight), which were removed with sodium borohydride in 99%, demonstrating the high potential of the method used. The inorganic As, present in the average amount of 0.0086 &#181;g/g (wet weight) was reduced in 27.7%. Preparation for consumption by baking in water, the blue-shark into cubes (1-2 cm3) resulted in greater removal of the total As, 65.9 to 71.2%; in the grilled shark the reduction was 55,4 to 60.2%. The samples, grilled or baked, added salt and lemon enriched with ascorbic acid, and the grilled containing salt and salt with lemon, presented reduction in the concentrations of inorganic As from 30.1 to 42.8%.