Dissertations / Theses: 'Non noble transition metal'

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Janisch, Daniel. "Geo-inspired pathways towards ternary non-noble metal (pre-)catalysts for water splitting and CO2 reduction." Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS387.pdf.

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Une transition des sources d'énergie fossiles vers la production d'énergie renouvelable nécessite des systèmes de stockage qui compensent l'intermittence des sources d'énergie verte. La production d'hydrogène provenant de l'électrolyse de l'eau alimentée par l'électricité solaire ou éolienne est un vecteur d'énergie abondante, propre et renouvelable. De plus, l'énergie renouvelable en surplus peut être stockée dans des carburants ou des produits chimiques plus complexes. Liée à l'électrolyse, l'électro-réduction du CO2 (CO2R) produit des hydrocarbures à haute densité énergétique qui stockent également de l'énergie dans les liaisons chimiques. Toutefois, le manque de viabilité économique empêche encore l'utilisation à grande échelle de ces procédés. Les électrodes mieux performants actuels dans l’électrolyse de l'eau sont platine et iridium qui sont chers et peu abondants. Les composés de métaux de transition plus répandus représentent une alternative beaucoup moins coûteuse. Il a été démontré que l'activité et la stabilité dans les électrolytes acides et alcalins sont améliorées, notamment dans les borures, les siliciures et les carbures binaires de métaux de transition. Les liaisons covalentes entre les éléments du bloc p et entre ces éléments et les métaux de transition, ainsi que les modifications de la densité de charge du métal qui en résultent, ont été identifiées comme des acteurs clés responsables de l'augmentation de l'activité catalytique. Néanmoins, la relation structure-activité reste obscure. La faible sélectivité du CO2R est l'obstacle majeur actuel de ce processus, car la séparation complexe des produits en aval rend le processus industriel non rentable. Le cuivre est le seul électrocatalyseur métallique capable de former des quantités substantielles d'hydrocarbures C+2. Les éléments du bloc p, tels que le soufre, augmentent la sélectivité des sulfures de cuivre pour les produits à un seul atome de carbone. Cependant, le rôle du soufre au cours de la réaction CO2R n'est pas clair et la modification de l'état de charge du cuivre par deux éléments du bloc p pour favoriser des produits C+2 n'a pas été étudiée. Pour résoudre ces questions ouvertes, nous avons conçu des voies de réaction vers des composés ternaires combinant un métal de transition avec deux éléments du bloc p. Les processus de réaction sont inspirés de phénomènes géologiques et reposent sur l'utilisation de sels fondus en tant que milieux de réaction. Cette approche est susceptible de produire des matériaux nanostructurés avec un rapport surface-volume élevé, ce qui est idéal pour les applications catalytiques. Dans la première partie de ce travail, la synthèse de quatre silicoborures ternaires de métaux de transition Ni6Si2B, Co4.75Si2B, Fe5SiB2 et Mn5SiB2 est présentée, ainsi qu'une étude détaillée des propriétés électrocatalytiques pour l'oxydation de l'eau alcaline. La XRD in situ basée sur le rayonnement synchrotron résout les mécanismes de formation au cours de la synthèse et met en lumière les relations structurelles entre les intermédiaires de réaction et les produits finaux. La deuxième partie est consacrée à l'étude de l'influence du silicium, du bore et du carbone sur le molybdène dans trois composés ternaires, Mo2BC, Mo4.8Si3C, Mo5SiB2, en tant qu'électrocatalyseurs de l'évolution de l'hydrogène à partir d'électrolytes aqueux acides et alcalins. Les techniques XPS et XAS mettent en évidence la relation entre l'état d'oxydation du molybdène et l'activité catalytique. L'évaluation de deux silicosulfures de cuivre ternaires Cu8SiS6 et Cu2SiS3 en tant que catalyseurs pour le CO2R constitue le sujet de la troisième partie de ce travail. La séquence de cristallisation au cours de la synthèse a été suivie par des mesures XRD in situ et les configurations électroniques ont été évaluées par XPS et XAS. Enfin, des mesures XAS in situ pendant les réactions de réduction du CO et du CO2 montrent comment les matériaux évoluent pendant la catalyse A full transition from fossil-based energy sources towards green energy production requires storage systems compensating for the intermittency of renewables. The production of green hydrogen from electrolysis of water powered by surplus electricity from solar or wind attracts a lot of attention as an abundant, clean and renewable energy vector. Beyond the electrolysis of water, surplus renewable energy can further be stored in more complex fuels or chemicals. Related to electrolysis, the electroreduction of CO2 (CO2R) yields energy-dense hydrocarbons storing also energy in chemical bonds. A lack of economic viability, however, still blocks widespread industrial use of these processes. The benchmark electrodes in water electrolysis cells are platinum group metals that are expensive and not abundantly available. Compounds of more common transition metals represent a much cheaper alternative as potential electrocatalysts for water splitting. It was shown that activity and stability in both acidic and alkaline electrolytes is enhanced most notably in binary transition metal borides (TMBs), silicides (TMSs) and carbides (TMCs). Covalent bonds between p-block elements and between these elements and the transition metals, and the resulting modifications of the metal charge density have been identified as key factors responsible for augmented catalytic activity. Nevertheless, the structure-activity relationship remains obscure and whether catalytic properties could be further boosted by a twofold combination of p-block elements with a transition metal has not been answered. Low CO2R selectivity is the current bottleneck in this process as intricate downstream product separation renders an industrial process unprofitable. Copper is the only metal electrocatalyst able to form substantial amounts of C+2 hydrocarbons. Again, p-block elements such as sulphur are reported to increase selectivity in copper sulphides to one-carbon products. Yet, the role of sulphur during CO2R remains unclear and whether a second p-block element could tune the charge state of copper to favour a single reduction pathway towards C+2 products has not been explored. To resolve these open questions, we have designed reaction pathways towards ternary compounds combining a transition metal with two p-block elements. The reaction processes are inspired by geological processes and rely on the use of molten salts as reaction media. Compared to classical solid-state synthesis, molten salts increase diffusivity of reactants and enable overall lower temperatures and reaction times. As a result, the process is prone to deliver nanostructured materials with high surface-to-volume ratio and without organic surface ligands, which is ideal for catalytic applications. In the first part of this work, the synthesis of four ternary transition metal silicoborides Ni6Si2B, Co4.75Si2B, Fe5SiB2 and Mn5SiB2 is presented, together with a detailed study of the electrocatalytic properties for alkaline water oxidation (OER). Synchrotron radiation-based in situ XRD resolves the formation mechanisms during the synthesis and sheds light on structural relationships between reaction intermediate and the final products. The second part is dedicated to the investigation of the influence of silicon, boron and carbon on molybdenum in three ternary compounds, Mo2BC, Mo4.8Si3C, Mo5SiB2, as electrocatalysts of hydrogen evolution from acidic and alkaline aqueous electrolytes. XPS and XAS point out the relationship between the oxidation state of molybdenum and the electrocatalytic activity. The assessment of two ternary copper silicosulphides Cu8SiS6 and Cu2SiS3 as catalysts for CO2R constitutes the topic of the third part of this work. The crystallisation sequence during synthesis was monitored during in situ XRD measurements and electronic configurations were assessed by XPS and XAS. Finally, in situ XAS during CO and CO2 reduction reactions shows how the materials evolve during electrocatalysis

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Tao, Shasha [Verfasser], Bernhard [Akademischer Betreuer] Kaiser, and Bastian J. M. [Akademischer Betreuer] Etzold. "Electrodeposition of Nickel-Based Non-Noble Transition Metal Compounds for Electrocatalytic Water Splitting / Shasha Tao ; Bernhard Kaiser, Bastian J. M. Etzold." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://d-nb.info/1192442547/34.

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Tao, Shasha [Verfasser], Bernhard [Akademischer Betreuer] Kaiser, and Bastian [Akademischer Betreuer] Etzold. "Electrodeposition of Nickel-Based Non-Noble Transition Metal Compounds for Electrocatalytic Water Splitting / Shasha Tao ; Bernhard Kaiser, Bastian J. M. Etzold." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2019. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-89232.

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Ben, Miled Marwan. "Synthèse in situ de nanoparticules métalliques dans une matrice céramique dérivées de polymères précéramiques pour l'électrolyse de l'eau en milieu alcalin." Electronic Thesis or Diss., Limoges, 2024. http://www.theses.fr/2024LIMO0083.

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Face au réchauffement climatique dû aux activités humaines et à l’utilisation de ressources fossiles, le besoin de trouver de nouvelles sources d’énergies décarbonées devient urgent. Le dihydrogène (H2) communément appelé « hydrogène » s’impose comme un vecteur énergétique d’intérêt de par sa capacité à produire une énergie de combustion supérieure à celle des énergies fossiles et à ne produire que de l’eau comme déchet lors de son utilisation dans une pile à combustible. De plus, son utilisation ne génère aucune nuisance sonore à la différence des moteurs thermiques couramment employés. Néanmoins, elle requiert un très haut degré de pureté afin d’éviter la pollution des matériaux catalytiques contenus dans ces piles à combustible. De nos jours, près de 95% de l’hydrogène produit se fait par reformage catalytique du méthane et nécessite donc des procédés de purification souvent complexes et couteux. Une façon de s’affranchir de ces procédés serait de produire l’hydrogène directement par électrolyse de l’eau. Cette méthode consiste à séparer une molécule d’eau sous l’action d’un courant électrique (produit de façon renouvelable) pour produire de l’hydrogène et du dioxygène (O2) aux bornes d’électrodes d’un électrolyseur. Malheureusement, cette réaction se heurte à des limitations cinétiques en raison d’un mécanisme de réaction de dégagement de dioxygène (RDO) très complexe, incluant plusieurs électrons et plusieurs intermédiaires réactionnel. L’émergence de nouvelles technologies de membranes échangeuses d’anion a ouvert la voie à l’utilisation de l’électrolyse en milieu alcalin, permettant donc l’utilisation de métaux de transition non nobles comme catalyseurs, moins couteux que les métaux traditionnellement employés (Ir et Ru). Ce manuscrit de thèse a donc exploré la synthèse de matériaux à visée catalytique pour réduire les barrières énergétiques et cinétiques de la RDO. Afin de proposer des matériaux performants, stables dans le temps et résistant aux milieux agressifs imposés par l’électrolyse de l’eau en milieu alcalin, la voie des céramiques dérivées de polymères précéramiques (PDC pour Polymer-Derived Ceramics) s’est avéré être une méthode d’élaboration de choix pour y parvenir. L’intérêt de cette méthode est de mettre en œuvre des polymères organosiliciés (ici un polysilazane) servant de plateforme moléculaire pour la croissance de métaux non nobles via l’utilisation de complexes métalliques tels que des chlorures et des acétylacétonates de nickel (Ni), de fer (Fe) ou encore de cobalt (Co). Ce polymère modifié par ces métaux sert de précurseur à la formation in situ de nanoparticules métalliques dans une matrice poreuse à base des éléments silicium (Si), carbone (C), oxygène (O) et azote (N) et garantissant leur accessibilité et stabilité après traitement thermique à 500°C sous argon. Ce manuscrit illustré à travers cinq chapitres décrit des travaux sur la synthèse et la caractérisation de nanoparticules de Ni (chapitre 3), Ni-Fe (chapitre 4) et d’alliages à moyenne et haute entropie (chapitre 5) qui complètent un état de l’art (chapitre 1) et une description des matériaux et méthodes mises en œuvre au cours de cette thèse (chapitre 2). Les matériaux formés ont été étudiés à chaque étape de leur synthèse à travers la mise en œuvre d’outils de caractérisation complémentaires avant d’en évaluer les performances électrochimiques ; notamment par mesure de la surtension anodique lors de la RDO afin d’identifier la meilleure combinaison métallique. Des tests post mortem ont été réalisés pour évaluer le potentiel des matériaux préparés. Compte tenu de la simplicité de la voie de synthèse et du faible coût des réactifs utilisés, ces travaux conduisent à une nouvelle famille de matériaux et à plusieurs perspectives prometteuses, non seulement pour le développement de catalyseurs efficaces et stables pour l'OER mais plus généralement pour de nombreuses applications en électrochimie. Ces opportunités sont désormais exploitées Global warming caused by human activity and the use of fossil fuels, urges the need to find new sources of carbon free energy. Dihydrogen (H2) more known as “hydrogen” is rapidly emerging as a technically viable and benign energy vector according to its ability to produce a higher density of combustion than fossil fuels and to produce only water as a waste product when used in a fuel cell. Moreover, its use generates no noise pollution, unlike the combustion engines currently in use. Nevertheless, it requires a very high degree of purity in order to avoid pollution of the catalytic materials contained in the cells. Nowadays, nearly 95% of the hydrogen produced is obtained by catalytic reforming of methane, and therefore requires purification processes that are often complex and costly. One way of avoiding these purification steps would be to produce hydrogen directly by electrolysis of water more known as water splitting. This process consists of separating a molecule of water under the action of an electric current (produced in a renewable way) to produce hydrogen and dioxygen (O2) at the electrodes of an electrolyser. Unfortunately, this reaction has kinetic limitations due to a very complex Oxygen Evolution Reaction (OER) mechanism, including several electrons and several reaction intermediates. The emergence of new anion exchange membrane technologies has paved the way for the use of electrolysis in alkaline media, thus allowing the use of non-noble transition metals as catalysts, which are less expensive than the metals traditionally used (Ir and Ru). Within this context, this PhD thesis has explored the synthesis of catalytic materials to reduce the energy and kinetic barriers of OER. In order to propose materials that are performant, stable over time and resistant to the aggressive environments imposed by the electrolysis of water in an alkaline medium, the polymer-derived ceramics (PDC) route has been selected as a synthesis method of choice. The interest of this method is to implement organosilicon polymers (here a polysilazane) serving as a molecular platform for the growth of non-noble metals via the use of metal complexes such as chlorides and acetylacetonates of nickel (Ni), iron (Fe) or cobalt (Co). This polymer modified by these metals serves as a precursor for the in situ formation of metal nanoparticles in a porous matrix based on the elements silicon (Si), carbon (C), oxygen (O) and nitrogen (N) allowing their accessibility and stability after heat treatment at 500 ° C under argon. This manuscript illustrated through five chapters describes works dedicated to the synthesis and characterization of Ni (chapter 3), Ni-Fe (chapter 4) and medium and high entropy alloys (chapter 5) nanoparticles which complete a state of the art (chapter 1) and a description of the materials and methods implemented during this thesis (chapter 2). The materials which have been prepared were studied at each stage of their synthesis through the implementation of complementary characterization tools before assessing their electrochemical performances; in particular by measuring the anodic overpotential during OER, in order to determine the best metal combinations. Post mortem tests were carried out to evaluate the potential of the prepared materials. Considering the simplicity of the synthesis route, and the low cost of reactants used, this work leads to a new family of materials and to several promising perspectives, not only for the development of efficient and stable catalysts for the OER but more generally for numerous applications in electrochemistry. These opportunities are now being addressed

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Howdle, Steven M. "Spectroscopy in liquefied and supercritical noble gases." Thesis, University of Nottingham, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329846.

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Carson, Cantwell G. "Noble and transition metal aromatic frameworks synthesis, properties, and stability /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29657.

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Thesis (Ph. D.)--Materials Science and Engineering, Georgia Institute of Technology, 2009. Committee Chair: Rina Tannenbaum; Committee Co-Chair: Rosario A. Gerhardt; Committee Member: E. Kent Barefield; Committee Member: Karl I. Jacob; Committee Member: Preet Singh; Committee Member: R. Bruce King. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Garg, Aaron R. "Transition metal carbide and nitride nanoparticles with Noble metal shells as enhanced catalysts." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/121890.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018 Cataloged from PDF version of thesis. Page 157 blank. Vita. Includes bibliographical references (pages 137-153). Core-shell nanostructures represent a promising and versatile design platform for enhancing the performance of noble metal catalysts while reducing the cost. Early transition metal carbides (TMCs) and nitrides (TMNs) have been identified as ideal core materials for supporting noble metal shells owing to their earth-abundance, thermal and chemical stability, electrical conductivity, and their ability to bind strongly to noble metals while still being immiscible with them. Unfortunately, the formation of surface oxides or carbon on TMCs and TMNs presents a difficult synthetic challenge for the deposition of atomically thin, uniform noble metal layers. Recent advances have enabled the synthesis of TMC core nanoparticles with noble metal shells (denoted as NM/TMC), although applicability toward TMN cores has not been previously demonstrated. Furthermore, the complete properties of these unique materials are still unknown. This thesis conducts a detailed investigation of the synthesis, characterization, and catalytic performance of NM/TMC and NM/TMN core-shell nanoparticles to provide a comprehensive understanding of their material properties and the underlying phenomena. First, in-situ studies yielded insight into the mechanism behind the high temperature self-assembly of NM/TMC particles, indicating the presence of a metallic alloy phase preceding the formation of the core-shell structure upon insertion of carbon into the lattice. Next, the synthesis of NM/TMN nanoparticles was demonstrated via nitridation of a parent NM/TMC, and the structural and electronic properties of both core-shell materials were examined through in-situ X-ray absorption spectroscopy (XAS). The analysis revealed significant alterations to the electronic structure of the noble metal shell due to bonding interactions with the TMC and TMN cores, which led to weakened adsorbate binding energies. Finally, the materials displayed improved performance for the oxygen reduction reaction (ORR), a critical challenge for fuel cell technologies. Notably, particles with complete, uniform shells exhibited unprecedented stability during electrochemical ageing at highly oxidizing conditions, highlighting the great potential of core-shell architectures with earth-abundant TMC and TMN cores for future ORR applications. Overall, this work will provide new opportunities toward the design of enhanced noble metal catalysts and enable further optimization of their performance. by Aaron R. Garg. Ph. D. Ph.D. Massachusetts Institute of Technology, Department of Chemical Engineering

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Jonsson, Daniel. "Evaluation of Non-Noble Metal Catalysts for CO Oxidation." Thesis, KTH, Skolan för kemivetenskap (CHE), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207363.

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The aim of the study is to evaluate the ability of non-noble metal catalysts to function as the commercially used noble metal catalyst. The exhaust gas that was used in the project is generated from a heater developed by ReformTech AB with diesel as fuel. The compound that was focused on is carbon monoxide that has a concentration of 300-750 ppm. The catalysts that were tested are MnO/CeO2, CuO/CeO2 and a Pt/CeO2 catalyst used to compare the non-noble metal catalyst with. The sensitivity against sulfur poisoning was also analyzed by mixing sulfur into the fuel. Analysis of the exhaust gas was done with a micro-GC and the catalysts were also analyzed with SEM before and after exposure of sulfur. The manganese catalyst with a loading of 7 wt-% did not show any activity against carbon monoxide oxidation. The copper catalysts contained two different loadings of active material, 7 and 14 wt-% and monoliths with 400 and 600 cpsi were used. Both loadings showed good activity against carbon monoxide oxidation. The most prominent catalyst was the 14 wt-% CuO/CeO2 catalyst with a 600 cpsi monolith because of an increase in surface area. The SEM analysis showed that sulfur was present on the surface when the heater was using diesel with 300 ppm sulfur. The sulfur caused complete deactivation of the non-noble metal catalysts and a small decrease in activity was shown on the noble metal Pt catalyst.

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Wan, Abu Bakar Wan Azelee. "Non-noble metal environmental catalysts : synthesis, characterisation and catalytic activity." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262524.

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Leonardy, Adrianus. "Non-Noble Metal Electrocatalysts for Proton Exchange Membrane Fuel Cell." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12036.

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Transition metal-nitrogen complex have shown promising electrocatalytic activity towards the oxygen reduction reaction (ORR) that can potentially replace the platinum-based electrocatalysts in fuel cell, which generally suffer from scarcity and instability issue. Iron and cobalt have been reported to posses the best electrocatalytic performance in comparison with other transition metals due to the nature of their d-electron configuration that fulfill the prerequisite strong back-bonding for the activation of oxygen molecule. Apart from the metal active centre, other factors such as catalyst support, electrode thickness and surface-nitrogen content have also been considered play important roles to improve the catalytic performance of transition-metal-nitrogen complex materials. In this study we integrated those factors and approaches to create non-noble metal-based electrocatalysts for proton exchange membrane fuel cell (PEMFC) with improved catalytic activity. Iron and cobalt were used as ORR metal active centers and different type of carbon supports were employed as electrocatalysts supports. Three different electrocatalysts were developed in this project, including ironcobaltnitrogen complex supported carbon nanotubes that were grown on carbon paper substrate, iron-cobalt-nitrogen complex incorporated vertically aligned carbon nanotubes and iron-cobalt-nitrogen complex incorporated vertically aligned nitrogen-doped carbon nanotubes. The electrochemical performances of those electrocatalysts were compared with platinum-based electrocatalyst, which is the most common commercial electrocatalysts recently. The results show that the developed non-noble metal-based electrocatalysts posses improved electrocatalytic properties in terms of electrochemical surface area, electron transfer number, kinetic rate constant, durability and methanol fuel tolerance.

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Zhou, Zheng. "Non-Noble Metal-Based Electrocatalysts for Efficient Hydrogen Evolution Reactions." Thesis, The University of Sydney, 2019. http://hdl.handle.net/2123/20956.

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Electrolysis of water by electricity generated from renewable energy sources is promising sustainable hydrogen (H2) production method. A critical task to realize the widespread application of this method is to develop high performance, low price, and stable electrocatalysts for hydrogen evolution reaction (HER). This thesis focuses on the understanding of the stability of non-noble metal-based electrocatalysts in electrolytes with a wide range of pH and the development of novel high-performance non-noble metal-based electrocatalysts for HER. First, using Ni2P as a reprehensive 3d transition metal-based electrocatalyst, its pHdependent performance stability was studied in detail. The pH of electrolytes strongly influences the HER activity of the Ni2P electrocatalyst. Tests in 19 electrolytes with pH ranging from 0.52 to 13.53, my results show that Ni2P is much more active in acidic and alkaline electrolytes. With the increase of pH, lower H+ concentration reduces the formation of adsorbed H atoms in the Volmer reaction, resulting in more impoverished activities. However, the high activity observed in the strong alkaline electrolytes is not the intrinsic property of Ni2P. Ni oxides/hydroxides are formed in strong alkaline electrolytes under applied potentials, resulting in improved activities. Next, I demonstrated the synthesis of ultrafine β-Mo2C nanoparticles with narrow size distribution (2.2 ± 0.3 nm) and high mass loading (up to 27.5 wt.%.) on graphene substrate using a giant Mo-based polyoxomolybdate (POM) cluster, Mo132 ((NH4)46[Mo132O372(H2O)72(CH3COO)30]). A nitrogen-containing polymeric binder (polyethyleneimine) was used to create Mo-N bonds between Mo2C nanoparticles and nitrogen-doped graphene layers, which dramatically improve the catalytic performance of the Mo2C electrocatalyst for HER as revealed by X-ray photoelectron spectroscopy and density functional theory calculations. The optimized Mo2C electrocatalyst shows a large exchange current density of 1.19 mA cm–2, a high turnover frequency of 0.70 s–1 as well as excellent durability. This new synthesis strategy opens the possibility of developing practical platinum substitutes based on Mo2C for practical HER applications.

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Keane, Theo. "Non-adiabatic effects in transition metal complexes." Thesis, University of Sheffield, 2016. http://etheses.whiterose.ac.uk/15948/.

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Chen, Xi. "Noble metal photocatalysts under visible light and UV light irradiation." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/47008/1/Xi_Chen_Thesis.pdf.

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One of the greatest challenges for the study of photocatalysts is to devise new catalysts that possess high activity under visible light illumination. This would allow the use of an abundant and green energy source, sunlight, to drive chemical reactions. Gold nanoparticles strongly absorb both visible light and UV light. It is therefore possible to drive chemical reactions utilising a significant fraction of full sunlight spectrum. Here we prepared gold nanoparticles supported on various oxide powders, and reported a new finding that gold nanoparticles on oxide supports exhibit significant activity for the oxidation of formaldehyde and methanol in the air at ambient temperature, when illuminated with visible light. We suggested that visible light can greatly enhance local electromagnetic fields and heat gold nanoparticles due to surface plasmon resonance effect which provides activation energy for the oxidation of organic molecules. Moreover, the nature of the oxide support has an important influence on the activity of the gold nanoparticles. The finding reveals the possibility to drive chemical reactions with sunlight on gold nanoparticles at ambient temperature, highlighting a new direction for research on visible light photocatalysts. Gold nanoparticles supported on oxides also exhibit significant dye oxidation activity under visible light irradiation in aqueous solution at ambient temperature. Turnover frequencies of the supported gold nanoparticles for the dye degradation are much higher than titania based photocatalysts under both visible and UV light. These gold photocatalysts can also catalyse phenol degradation as well as selective oxidation of benzyl alcohol under UV light. The reaction mechanism for these photocatalytic oxidations was studied. Gold nanoparticles exhibit photocatalytic activity due to visible light heating gold electrons in 6sp band, while the UV absorption results in electron holes in gold 5d band to oxidise organic molecules. Silver nanoparticles also exhibit considerable visible light and UV light absorption due to surface plasmon resonance effect and the interband transition of 4d electrons to the 5sp band, respectively. Therefore, silver nanoparticles are potentially photocatalysts that utilise the solar spectrum effectively. Here we reported that silver nanoparticles at room temperature can be used to drive chemical reactions when illuminated with light throughout the solar spectrum. The significant activities for dye degradation by silver nanoparticles on oxide supports are even better than those by semiconductor photocatalysts. Moreover, silver photocatalysts also can degrade phenol and drive the oxidation of benzyl alcohol to benzaldehyde under UV light. We suggested that surface plasmon resonance effect and interband transition of silver nanoparticles can activate organic molecule oxidations under light illumination.

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OSMIERI, LUIGI. "Non-noble metal catalysts for oxygen reduction reaction in low temperature fuel cells." Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2640183.

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Polymer electrolyte membrane fuel cells (PEMFC) are electrochemical devices which can directly convert the chemical energy of a fuel (such as hydrogen or a low-molecular weight alcohol) and an oxidant (i.e. oxygen) into electrical energy with high efficiency. Moreover, due their low operating temperature, they are suitable for automotive or portable applications. However, the slow kinetics of oxygen reduction reaction (ORR) requires the use of costly Pt-based catalysts at the cathode in order to obtain the desired power density values. Nevertheless, the cathode is still responsible for the main voltage loss in the cell. The overall objective of the research carried out in this Ph.D. thesis was the development of Pt-free ORR catalysts starting from different carbon, nitrogen and transition metals precursors. Different synthesis approaches were used in order to obtain an improvement of the activity, and to understand the influence of the synthesis process variables. In particular, the influence of carbon supports (commercial and synthesized in the lab), nitrogen and transition metals precursors, templating agents, number and temperature of pyrolysis were examined. The catalysts produced were characterized by means of several instrumental techniques such as N2 physisorption, XRD, XPS, EDX, SEM, FESEM, TEM, Raman and FTIR. The effect of the presence of different transition metals on the pyrolysis process was investigated by TGA coupled with a mass spectroscopy analysis, in order to have an insight on their influence in the formation of ORR active sites. The activity toward ORR was assessed by RDE-RRDE (rotating disk electrode - rotating ring disk electrode) analysis and by gas-diffusion electrode in a 3-electrodes electrochemical cell configuration. The electrochemical techniques used were cyclic voltammetry (CV), linear sweep voltammetry (LSV), staircase voltammetry (SV), chronoamperometry and electrochemical impedance spectroscopy (EIS). These electrochemical tests were performed in both acid and alkaline conditions, with reference to the potential applications in both H+ and OH– conducing polymer electrolyte membrane fuel cells. This first part of research was carried out in the laboratories of the Gre.En2 (Green Energy and Engineering) Group in the Department of Applied Science and Technology (DISAT) at Politecnico di Torino. Then, in the second part, some of the most promising electrocatalysts in terms of ORR activity were in different types of single PEMFC. In particular, using acidic electrolyte membrane, the tests were performed using H2 or methanol as fuels. In the case of direct methanol fuel cell (DMFC) tests, short-term durability tests were done in order to compare the durability performance of our catalysts with a standard Pt-based catalysts. The tests with alkaline electrolyte membrane were performed using ethanol as fuel. This second part of research was carried out at the Universidad Autonoma de Madrid in the laboratories of the Department of Applied Physical-Chemistry. Here the structure of the thesis: Chapter 1 is a general introduction about the PEMFC fuel cell technology, particularly focusing on the non-noble metal catalysts for ORR as potential alternative to Pt. Chapter 2 is focused on the use of different types of reduced graphene oxide as support for the synthesis of Fe-N/C catalysts. In Chapter 3, a complex between Co ions and a N-containing ligand molecule is impregnated on multi walled carbon nanotubes and pyrolyzed one or two times for producing a Co-N-C catalyst, and the influence of the second pyrolysis on the activity improvement was investigated. Chapter 4 deals the optimization of the synthesis process of a Fe-N-C catalyst using polypyrrole as N source and mesoporous carbon a C-support. In Chapter 5 the study of the influence of different silica templates on the morphology on the ORR activity of a Fe-N-C catalyst synthesized using Fe-phthalocyanine as precursor is presented. In Chapter 6, different Me-phthalocyanines (Me = Fe, Co, Cu, Zn) were used as precursor for the synthesis of Me-N-C catalysts using SBA-15 silica as hard template. The influence of the different transition metals on the pyrolysis process and on the ORR activity and selectivity toward a complete 4 e- oxygen reduction was investigated in both acid and alkaline conditions. A detailed kinetic analysis in acid conditions is also presented. The most active catalyst was tested in different types of PEMFCs. Finally, in Chapter 7, the influence of four different carbon supports on the ORR activity of Fe-N/C catalysts in acid and alkaline conditions as well as the performance in single PEMFC is examined. The general conclusions of the thesis are presented in Chapter 8.

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15

Smith, Alexis. "Coordination complexes of trivalent non-transition metal ions." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28400.

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Lathaxride(III) complexes of three potentially heptadentate Schiff base ligands were prepared by addition of lanthanide(III) salts to a solution containing a slight excess of ligand in the presence of poorly coordinating chloride ions or strongly coordinating nitrate ions. The complexes La(hatren), La(datren)(CH₃0H) and La(trac) were isolated in the presence of chloride ions, and were found to have the ligand bound in a hexadentate or heptadentate fashion. We were unable to isolate analogous complexes with the heavier lanthanides (Ln = Pr, Nd, Gd, Dy, Yb, Lu). The complexes Ln(H₃L)(NO₃)₃ (Ln = La, Pr, Nd, Gd, Dy, Yb; H₃L = H₃hatren, H₃datren) and Ln(H₃trac)(NO₃)₃ (Ln = Pr, Nd, Gd, Dy, Yb) were isolated in the presence of nitrate ions, and were found to have the Schiff base ligand bound in a tridentate fashion ( where H₃datren = tris(2'-hydroxy-4',5'-dimethylacetopheniminoethyl)amine; H₃trac = tris(3-aza-4-methylhept-4-ene-6-one)amine; and H₃hatren = tris(2'-hydroxyacetophenirninoethyl)amine) All products were characterized by infrared and mass spectroscopy, and by elemental analysis. ¹H-NMR spectroscopy indicated that the complexes were solution labile and dissociated in DMSO to yield free ligand and solvated lanthanide(III) ions. The crystal structure of Gd(H₃trac)(NO₃)₃ was determined. The gadolinium(III) ion is nine coordinate. H₃trac is bound only through its three oxygen donor atoms, and the nitrate ions are bound in a bidentate fashion to the gadolinium center. Aluminum (III) and gallium(III) complexes of 2-chloromethyl-5-hydroxy-4H-pyran-4-one (Hck) were isolated from a basic aqueous solution. The complexes Al(ck)₃ and Ga(ck)₃ were characterized by ¹H-NMR (CDCI₃), infrared and mass spectroscopy, as well as by elemental analysis. Al(ck)₃ was also characterized by ²⁷Al-NMR in CDCI₃. Science, Faculty of Chemistry, Department of Graduate

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16

Stephen, Emma Louise. "Redox non-innocence in transition metal macrocyclic complexes." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580394.

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Abstract Chapter one introduces this thesis with a brief overview of macrocyclic chemistry and provides examples of macrocyclic complexes as well as briefly discussing the applications of macrocyclic complexes, the macrocyclic effect and the co-ordination chemistry of sulfur-based macro cyclic transition metal complexes. The concepts of paramagnetism and Jahn- Teller distortion are approached with respect to the target metal oxidation states Ni(III), Pt(III) and Pd(III). The overall aim of the work presented in this thesis is also stated. Chapter two continues from the concept of paramagnetism briefly discussed in chapter one and describes the technique of EPR spectroscopy and the energy terms associated with the EPR spin Hamiltonian such as the electron Zeeman interaction (g) and the hyperfine and superhyperfine coupling parameters (A, a). The limitation of this technique is discussed in terms of observed hyperfine splitting and the technique of ENDOR spectroscopy is introduced. Chapter three describes the chemistry of Ni(III) macrocyclic complexes and a brief history of 61Ni EPR spectroscopic studies. The Ni(II) complexes [Ni([9]aneNS2-CH3)2]2+ ([9]aneNS2-CH3 = N-methyl-l-aza-4, 7 -dithiacyclononane), 1 2-bis-(1-aza-4 7- , , dithiacyclononylethane), [Ni([9]aneS3)2]2+ ([9]aneS3 = 1,4,7 -trithiacyclononane) and I-phenyl-l-phospha-4,7- dithiacyclononane) have been prepared and can be chemically oxidized to gave the formal Ni(III) products [Ni([9]aneS3)2]3+, [Ni(bis[9]aneNS2-C2H4)]3+ and [Ni([9]aneNS2-CH3)2]3+ and [Ni([9]aneS2P-C6Hs)2]3+ which have been characterized by multi-frequency EPR spectroscopy. The multi-frequency X-, L-, S-, K- and Q- [Ni([9]aneS3)2]3+ and their 86.2% 61Ni-enriched analogues as both fluid and frozen 11 Abstract solutions were simulated. Treatment of the spm Hamiltonian parameters by perturbation theory reveals that the SOMO has 50.6%, 42.8% and 37.2% Ni 3dz' character m and [Ni([9]aneS3)2]3+ respectively, consistent with DFT calculations and reflecting delocalization of charge onto the S-thioether centres. EPR spectra for C8Ni([9]aneS3)2]3+ and [61,S8Ni([9]aneS3)2]3+ are consistent with a dynamic Jahn- Teller distortion in this compound. In contrast to [Ni([9]aneNS2-CH3)2]3+, [Ni(bis[9]aneNS2-C2H4)]3+ and [Ni([9]aneS3)2]3+, DFT calculations on [Ni([9]aneS2P-C6Hs)2]3+ reveal that the SOMO for this complex has 30.9% Ni 3dxy character. Chapter four details the chemistry of Pt(III) and that of Pt(II) macrocyclic complexes. The Pt(II) complexes [Pt([9]aneS3)2]2+ ([9]aneS3 1,4,7- trithiacyclononane), [Pt([18]aneS6)]2+ ([18]aneS6 1,4,7,1 0, 13, 16- hexathiacyclooctadecane) and [Pt([ 1 0]aneS3)2f+ ([ 1 0]aneS3 1,4,7- trithiacyclodecane) have been synthesised. The electrochemical two electron oxidation of [Pt([9]aneS3)2]2+ to [Pt([9]aneS3)2t+ in MeCN [0.2 M NBli4PF6, vs. Fe + IFc, N2, chemically reversible at 243 K] proceeds via an unusually stable [Pt([9]aneS3)2]3+ intermediate [E« = +0.37 V vs. Fc+IFc, ~E = 142 mY, A = 396 nm (5700)]. Single crystals of [Pt([9]aneS3)2](PF6kMeCN were grown from a solution following a limited one electron electrochemical oxidation of the parent Pt(II) complex [Pt([9]aneS3)2]2+. [Pt([9]aneS3)2](PF6)3.MeCN possesses a distorted octahedral geometry consistent with a J ahn- Teller distorted low-spin 5d7 Pt(III) centre. Multi-frequency EPR spectroscopy of chemically-generated [Pt([9]aneS3)2]3+ in HCI04 at Q-, X-, S- and L-band show that [Pt([9]aneS3)2]3+ undergoes a dynamic Jahn-Teller distortion in solution which was minimised at 80 K to reveal rhombic parameters. Treatment of the Spin Hamiltonian reveals that the Pt Sd» orbital iii Abstract contribution to the SOMO of this Pt(III) species, supported by DFT calculations is :S 30.4% and reflecting the non-innocence of the thioether crown macrocyc1e. In addition to this, DFT calculations identify significant spin density on four protons pendant to the macrocyc1ic backbone. The couplings associated with these protons were confirmed by S- and X-band EPR spectroscopy and studied further by double resonance methods to reveal that these protons interact with the Pt 5dz2 orbital through an orbital through-bond interaction. A comparative multi-frequency EPR spectroscopic study was undertaken on the chemically-generated complexes [Pt([18]aneS6)]3+ and [Pt([10]aneS3)2]3+ in 70% HCl04. Interpretation of the spin Hamiltonian parameters reveals that the Pt 5dz> orbital contributions to the SOMOs of these Pt(III) species are :S23.8%. Pt(III) solid state structures were unobtainable for [Pt([18]aneS6)]3+ and [Pt([10]aneS3)2]3+, but attempts to isolate [Pt([l 0]aneS3)2]3+ led to the isolation of the octahedral Pt(IV) complex [Pt([l 0]aneS3)2] (Cl04k(H30)2 [Pt- S = 2.3610(11), 2.3552(10), 2.3792(11) A]. Chapter five begins with a discussion of Pd(III) chemistry and the chemistry of Pd(II) with macrocyc1ic ligands. The Pd(II) complexes [Pd([9]aneS3)2]2+ ([9]aneS3 = 1,4,7-trithiacyc1ononane) and [Pd([18]aneS6)f+ ([18]aneS6 = 1,4,7,10,13,16- hexathiacyc1ooctadecane) have been prepared and can be chemically oxidized to gave the formal Pd(III) products [Pd([9]aneS3)2]3+ and [Pd([18]aneS6)]3+, which have been characterized by X-ray crystallography and multifrequency EPR spectroscopy. The single of crystal X-ray structures distorted octahedral stereochemistries for the Pd centres with Pd-S distances of [2.3692, 2.3695(8), 2.5356(9) A] and [2.3454(5), 2.3490(6), 2.5474(6) A] respectively, consistent with the Jahn- Teller distorted geometry expected for d7 Pd(III) complexes. Further to the chemical oxidation, [Pd([9]aneS3)2](PF6)2 shows a iv Abstract one-electron oxidation process in MeCN [0.2 M NBll4PF6, 293 K] at Ey, = +0.57 V vs. F c + IF c assigned to a formal Pd(III)/Pd(II) couple. Multi-frequency EPR spectra of [Pd([9]aneS3)2]3+ and [Pd([18]aneS6)]3+ as both fluid (X-band) and frozen (Q-, X-, S- and L-band) solutions were simulated. Treatment of the spin Hamiltonian parameters by perturbation theory reveals that the SOMO has 21.8% and 25% Pd character in [Pd([9]aneS3)2]3+ and [Pd([18]aneS6)]3+ respectively, consistent with DFT calculations and reflecting the significant electronic charge distributed over the S-thioether centres. Both [Pd([9]aneS3)2]3+ and [Pd([18]aneS6)]3+ exhibit a clear five line superhyperfine splitting in the g== region in the EPR spectra. Double resonance spectroscopic measurements supported by DFT calculations have shown that four protons pendant to the macrocyclic backbone give rise to this feature through a through-bond interaction with the Pd 4dz2orbital. Chapter six concludes this thesis with a discussion on the overall conclusions to the work on the transition metal macrocyclic complexes presented in this thesis. v

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17

Tünnermann, Maike [Verfasser]. "Photocatalytic water reduction systems based on iridium and non-noble metal complexes / Maike Tünnermann." Paderborn : Universitätsbibliothek, 2018. http://d-nb.info/1170228267/34.

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18

MONTEVERDE, VIDELA ALESSANDRO HUGO. "Non-Noble Metal Cathodic Electrocatalysts for PEM Fuel Cells and Direct Methanol Fuel Cells." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2506285.

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The main problem of PEMFCs and DMFCs, is linked with the high price of Pt-based electrocatalysts, on one side, and durability issues, on the other side. In this work electrocatalysts for oxygen reduction reaction (ORR) were developed, synthesized and tested for the fuel cell systems based on hydrogen or methanol. Moreover, tests under sub-freezing conditions at temperatures below 0°C, were conducted to assess the performance of FCs systems in harsh environmental conditions. Specifically, the electrochemical performance of three types of electrocatalysts for the oxygen reduction reaction, based respectively on a hollow core mesoporous shell carbon (HCMSC), an ultrasonic spray pyrolysis mesoporous carbon (USPMC) and a graphene reduced oxide (GRO) were compared. These catalysts were then evaluated electrochemically in a three-electrode one-compartment cell, using a 0.5 M H2SO4 solution as electrolyte, an auxiliary electrode and a reversible hydrogen electrode (RHE), as counter and reference electrodes, respectively. X-ray photoelectron spectroscopy (XPS), X-ray scattering (XRD), Brunauer-Emmett-Teller (BET) and Transmission electron microscopy (TEM) were carried out in order to understand chemical-physical phenomenon, and electrochemical tests were conducted via linear sweet voltammetry (LSV) and cyclic voltammetry (CV). On the other hand, the effects of methanol concentration, temperature, freezing/thawing (F/T) tests and cell purging time, evaluating the performance of a single direct methanol fuel cell (DMFC), were investigated. Specific purging conditions were optimized to increase the durability of MEAs. SEM analysis of MEAs after F/T cycles showed that a significant MEA degradation occurred when the produced water is not removed. Such a degradation affected the subsequent cell performance and durability, which depend of the purging procedure, purging time, and purge flow. By opportunely modifications of the purging procedure, the performance of single DMFCs remained almost constant after 25 F/Ts.

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Mottaghizadeh, Alireza. "Non-conventional insulators : metal-insulator transition and topological protection." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066652/document.

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Ce manuscrit présente une étude expérimentale de phase isolante non-conventionnelle, l'isolant d'Anderson, induit par le désordre, l'isolant de Mott, induit par les interactions de Coulomb, et les isolants topologiques.Dans une première partie du manuscrit, je décrirais le développement d'une méthode pour étudier la réponse de charge de nanoparticules par Microscopie à Force Electrostatique (EFM). Cette méthode a été appliquée à des nanoparticules de magnétite (Fe3O4), un matériau qui présente une transition métal-isolant, i.e. la transition de Verwey, lors de son refroidissement en dessous d'une température TV~120 K.Dans une seconde partie, ce manuscrit présente une étude détaillée de l'évolution de la densité d'états au travers de la transition métal-isolant entre un isolant de type Anderson-Mott et une phase métallique dans le matériau SrTiO3, et ceci, en fonction de la concentration de dopants, les lacunes d'oxygènes. Nous avons trouvé que dans un dispositif memoresistif de type Au-SrTiO3-Au, la concentration de dopants pouvait être ajustée par migration des lacunes d'oxygènes à l'aide d'un champ. Dans cette jonction tunnel, l'évolution de la densités d'états au travers de la transition métal-isolant peut être étudiée de façon continue. Finalement, dans une troisième partie, le manuscrit présente le développement d'une méthode pour la microfabrication d'anneaux de Aharonov-Bohm avec l'isolant topologique, Bi2Se3, déposée par épitaxie à jet moléculaire. Des résultats préliminaires sur les propriétés de transport quantique de ces dispositifs seront présentés This manuscript presents an experimental study of unconventional insulating phases, which are the Anderson insulator, induced by disorder, the Mott insulator, induced by Coulomb interactions, and topological insulators.In a first part of the manuscript, I will describe the development of a method to study the charge response of nanoparticles through Electrostatic Force Microscopy (EFM). This method has been applied to magnetite Fe3O4 nanoparticles, a material that presents a metal-insulator transition, i.e. the Verwey transition, upon cooling the system below a temperature Tv=120K. In a second part, this manuscript presents a detailed study of the evolution of the Density Of States (DOS) across the metal-insulator transition between an Anderson-Mott insulator and a metallic phase in the material SrTiO3 and this, as function of dopant concentration, i.e. oxygen vacancies. We found that in this memristive type device Au-SrTiO3-Au, the dopant concentration could be fine-tuned through electric-field migration of oxygen vacancies. In this tunnel junction device, the evolution of the DOS can be followed continuously across the metal-insulator transition. Finally, in a third part, the manuscript presents the development of a method for the microfabrication of Aharonov-Bohm rings with the topological insulator material, Bi2Se3, grown by molecular beam epitaxy. Preliminary results on the quantum transport properties of these devices will be presented

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Mottaghizadeh, Alireza. "Non-conventional insulators : metal-insulator transition and topological protection." Electronic Thesis or Diss., Paris 6, 2014. http://www.theses.fr/2014PA066652.

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Ce manuscrit présente une étude expérimentale de phase isolante non-conventionnelle, l'isolant d'Anderson, induit par le désordre, l'isolant de Mott, induit par les interactions de Coulomb, et les isolants topologiques.Dans une première partie du manuscrit, je décrirais le développement d'une méthode pour étudier la réponse de charge de nanoparticules par Microscopie à Force Electrostatique (EFM). Cette méthode a été appliquée à des nanoparticules de magnétite (Fe3O4), un matériau qui présente une transition métal-isolant, i.e. la transition de Verwey, lors de son refroidissement en dessous d'une température TV~120 K.Dans une seconde partie, ce manuscrit présente une étude détaillée de l'évolution de la densité d'états au travers de la transition métal-isolant entre un isolant de type Anderson-Mott et une phase métallique dans le matériau SrTiO3, et ceci, en fonction de la concentration de dopants, les lacunes d'oxygènes. Nous avons trouvé que dans un dispositif memoresistif de type Au-SrTiO3-Au, la concentration de dopants pouvait être ajustée par migration des lacunes d'oxygènes à l'aide d'un champ. Dans cette jonction tunnel, l'évolution de la densités d'états au travers de la transition métal-isolant peut être étudiée de façon continue. Finalement, dans une troisième partie, le manuscrit présente le développement d'une méthode pour la microfabrication d'anneaux de Aharonov-Bohm avec l'isolant topologique, Bi2Se3, déposée par épitaxie à jet moléculaire. Des résultats préliminaires sur les propriétés de transport quantique de ces dispositifs seront présentés This manuscript presents an experimental study of unconventional insulating phases, which are the Anderson insulator, induced by disorder, the Mott insulator, induced by Coulomb interactions, and topological insulators.In a first part of the manuscript, I will describe the development of a method to study the charge response of nanoparticles through Electrostatic Force Microscopy (EFM). This method has been applied to magnetite Fe3O4 nanoparticles, a material that presents a metal-insulator transition, i.e. the Verwey transition, upon cooling the system below a temperature Tv=120K. In a second part, this manuscript presents a detailed study of the evolution of the Density Of States (DOS) across the metal-insulator transition between an Anderson-Mott insulator and a metallic phase in the material SrTiO3 and this, as function of dopant concentration, i.e. oxygen vacancies. We found that in this memristive type device Au-SrTiO3-Au, the dopant concentration could be fine-tuned through electric-field migration of oxygen vacancies. In this tunnel junction device, the evolution of the DOS can be followed continuously across the metal-insulator transition. Finally, in a third part, the manuscript presents the development of a method for the microfabrication of Aharonov-Bohm rings with the topological insulator material, Bi2Se3, grown by molecular beam epitaxy. Preliminary results on the quantum transport properties of these devices will be presented

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Chaïb, Cheikh GASSER J. G. "CONTRIBUTION A L'ETUDE DES PROPRIETES ELECTRONIQUES D'ALLIAGES METALLIQUES LIQUIDES DE TYPE METAL NOBLE (OU DE TRANSITION)-POLYVALENT /." [S.l.] : [s.n.], 1987. ftp://ftp.scd.univ-metz.fr/pub/Theses/1987/Chaib.Cheikh.SMZ8708.pdf.

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22

PEZZOLATO, LORENZO. "Fe-N-C non-noble catalysts for applications in Fuel Cells and Metal Air Batteries." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2809320.

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23

Xu, Yin. "Preparation of noble metal free mixed oxides : applications to environmental catalysis." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R070.

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Dans un contexte politique et législatif favorisant l’utilisation de métaux abondants et non toxiques, différentes classes de catalyseurs à base de métaux de transition ont été développées puis évaluées pour deux réactions de dépollution : (i) l’ozonation catalytique pour l’élimination de polluants en phase aqueuse et (ii) l’oxydation catalytique de composés organiques volatils en phase gazeuse. Les oxydes de structure type spinel AB2O4 et les pérovskites possédant la formule générale ABO3 (où A et B sont des cations métalliques) sont des candidats intéressants de par leur innocuité et leur plus faible coût comparé aux métaux de la famille du platine. Par ailleurs, les propriétés versatiles de ces oxydes mixtes, telles que les nombreuses compositions possibles et leurs états de surface associés, ont démontré leur intérêt en catalyse hétérogène. Dans la première réaction concernant les procédés d’oxydation avancés, des oxydes mixtes de structure type spinel ont été étudiés pour agir comme catalyseur de dégradation de polluants organiques (AO7 et bisphénol A). Deux compositions, CuAl2O4 et CuFe2O4, ont été identifiés comme catalyseurs actifs pour l’activation de l’ozone et du peroxymonosulfate, précurseurs d’espèce radicalaires. La combinaison du cuivre avec l'aluminium ou avec le fer s’est révélée bénéfique pour former des radicaux réactifs à partir d’ozone ou de péroxymonosulfate, améliorant nettement la dégradation des polluants visés par rapport aux oxydes simples. Dans la seconde réaction impliquant l’oxydation catalytique du formaldéhyde en phase gazeuse, des pérovskites et des oxydes de manganèse ont été évalués. Une étude sur l’enrichissement en surface du métal de transition a été réalisée soit par traitement chimique via un lavage acide du précurseur pérovskite, soit par une approche de synthèse en sous-stœchiométrie employée lors de la préparation. Au regard des résultats expérimentaux, cet enrichissement permet d’exalter les propriétés catalytiques des solides pour l’élimination du formaldéhyde à basse température. Ces performances peuvent être reliées aux effets cumulés associés à la formation d’une morphologie contenant une porosité multiple suite au traitement chimique par voie acide, à l’augmentation significative de la surface spécifique et à l’augmentation de la densité des sites redox de surface mise en évidence par le suivi du couple Mn4+/Mn3+. Enfin, la promotion du support catalytique LaMnO3 par des métaux alcalins et alcalino-terreux a été réalisée (La0.8A0.2MnO3 avec A = K, Na, Sr, Ca). Basé sur les performances catalytiques à une température donnant une conversion de 50%, le dopage au potassium s’est révélé être le plus attractif (La0.8K0.2MnO3> La0.8Na0.2MnO3> La0.8Sr0.2MnO3> LaMnO3≈ La0.8Ca0.2MnO3≈ LMO-OH ≈ LMO-Na). Des vieillissements chimiques sous conditions humides et sèches ont par conséquent été réalisés sur les meilleurs catalyseurs afin d’évaluer leur robustesse. Malgré une conservation des propriétés texturales, une désactivation graduelle des pérovskites dopées (K, Na, Sr) a été observée et reliée à une perte d’espèces actives de surface et à une réduction du degré d’oxydation moyen du manganèse In a political and legislative context promoting the use of abundant and non-toxic metals, different classes of transition metal catalysts have been developed and evaluated for two depollution reactions: (i) catalytic ozonation or activated persulfate for the elimination of pollutants containing nitrogen in the aqueous phase and (ii) the catalytic oxidation of volatile organic compounds in the gas phase. Structural spinel oxides AB2O4 and perovskites having the general formula ABO3 (where A and B are metal cations) are interesting candidates because of their safety and lower cost compared to platinum family metals. Moreover, the versatile properties of these mixed oxides, such as the numerous possible compositions and their associated surface states, have demonstrated their interest in heterogeneous catalysis. In the first reaction concerning advanced oxidation processes, spinel type mixed oxides have been studied to act as a degradation catalyst for organic pollutants (AO7 and bisphenol A). Two compositions, CuAl2O4 and CuFe2O4, have been isolated as active catalysts for the activation of ozone and peroxymonosulphate radical precursors. The combination of copper with aluminum or iron has been found to be beneficial in forming reactive radicals from ozone or peroxymonosulphate, significantly improving the degradation of targeted pollutants compared with simple oxides. In the second reaction involving the catalytic oxidation of formaldehyde in the gas phase, the perovskites and the manganese oxides were evaluated. A study dealing with the surface enrichment of the transition metal was carried out either by chemical treatment via acid washing of the perovskite precursor, or by a sub-stoechiometric approach used during the preparation. At the light of the experimental results, this enrichment improves drastically the elimination of formaldehyde towards low temperatures. These performances can be related to the cumulative effects associated with the formation of a morphology containing a multiple porosity following the acidic chemical treatment, the significant increase of the specific surface and the increase of the density of the surface redox sites highlighted by the Mn4 + / Mn3 + couple. Finally, the promotion of the catalytic support LaMnO3 by alkali and alkaline earth metals was carried out according to different conditions (La0.8A0.2MnO3 with A = K, Na, Sr, Ca). Based on the catalytic performances at a temperature giving a conversion of 50% of formaldehyde in CO2, potassium doping proved to be the most attractive doping agent (La0.8K0.2MnO3> La0.8Na0.2MnO3> La0.8Sr0.2MnO3> LaMnO3 = La0. 8Ca0.2MnO3= LMO-OH = LMO-Na). Chemical aging under wet and dry conditions has therefore been carried out on the best catalysts to evaluate their robustness. Despite a conservation of textural properties, a gradual deactivation of the doped perovskites (K, Na, Sr) was observed and related to a loss of surface active oxygen species and a reduction in the average degree of oxidation of manganese

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Ogunsipe, Abimbola Olukayode. "Photophysical and photochemical studies of non-transition metal phthalocyanine derivatives." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1007721.

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A detailed photophysicochemical study of some non-transition metal (AI, Zn, Si, Ge, and Sn) metallophthalocyanine (MPc) derivatives is presented. The effects of substituents, central metal ions and solvents on the photophysical and photochemical properties are investigated and rationalized accordingly. The presence of peripheral substituents on the macrocycle enhances the yield of the triplet state. Near infra-red absorptions of the solvents reveal that solvents which absorb around 1100 nm and around 1270 nm, quench the triplet state of the MPc derivative and singlet oxygen, respectively. Although water has a high singlet oxygen quenching effect, the singlet oxygen quantum yield (Φ∆) value for sulphonated zinc phthalocyanine in water is still reasonably high at 0.48, which may provide an explanation for the efficient photosensitization by this molecule in photodynamic studies. The lowering of Φ∆ following protonation of the MPc macrocycle is attributed to the lowering of triplet energy to the level where energy transfer to ground state oxygen is no longer favourable. MPc inclusion complexes with cyclodextrins showed larger Φ∆ values when compared to the complexes before inclusion. Job's plots show that 2:1 and 4:1 (CD:MPc) complexes may be formed. Fluorescence quenching by electron donors and acceptors were analysed by StemVolmer relationship and the results used in determining fluorescence lifetimes of the complexes. Qualitative and quantitative interpretations of the interaction of sulphonated MPcs with bovine serum albumin (BSA) are provided in this thesis. 1:1 adducts were formed with BSA, but the binding feasibilities varied markedly. Spectral, photophysical and photochemical properties of the complexes are altered in the presence of BSA.

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25

Ackland, G. J. "Non-pairwise potentials and defect modelling for transition metals." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379869.

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26

Bo, Huang. "The Developments of Novel Nanomaterials with Non-Noble Metal Elements RuxCu1-x Solid-Solution Nanoparticles and MgO Nanoparticles/Metal-Organic Frameworks―." Kyoto University, 2017. http://hdl.handle.net/2433/226757.

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27

Stevens, Christopher E. "Study of Transition Metal Dichalcogenides Via Linear and Non-Linear Spectroscopy." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7955.

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Beginning with the discovery of graphene, two-dimensional materials have amassed a strong interest. Like graphene, transition metal dichalcogenides (TMDs) can be coaxed into atomically thin sheets which have some impressive properties. Unlike graphene, TMDs also has a change in their electronic band structure causing an indirect band gap to a direct gap transition in its monolayer form. Additionally, these materials lose their inversion symmetry as a monolayer. These unique properties make TMDs a strong candidate for being used in optoelectronic and valleytronic devices. In order for these devices to be successful, the optical properties of TMDs must be thoroughly understood. Due to this class of material's strong Coulomb interaction, the optical properties are dominated by excitons, a quasiparticle made up of an electron-hole pair. Therefore, the success of these devices relies, in part, on understanding and manipulating excitons. One key parameter of excitons is their dephasing rate which characterizes the lifetime of the coherent superposition of two states (i.e. how the coherence decays which is caused by excitons interacting with their environment). In this work, two optical properties are investigated: (1) How the linear absorption of the TMDs A-exciton peak varies as the material increases in thickness. By looking at how the absorption varies by sample thickness, the interaction between emitters can be understood. Experimental results for the diamagnetic shift are presented which are used to determine the lateral excitonic size. Through theoretical calculations, based on the semiconductor Maxwell-Bloch equations, additional insight into the radiative coupling of the systems are obtained. (2) How the coherence prole of the exciton changes in the presence of an external magnetic eld and specic valley excitation. By varying the polarization scheme in the four wave mixing measurement, specic valley excitation can be selected, allowing for insight into the dephasing mechanisms. By applying an external magnetic eld, the energy levels of the electron and hole can be discretized and the corresponding eects on the system's coherence seen. In conjunction with time-dependent density function theory calculations and the experimental results, a deeper understanding of exciton dynamics and multi-exciton complexes was obtained. Finally, a new system is proposed in which complex spectroscopic techniques can be performed on micron sized samples as well as devices in the presence of an external magnetic eld at cryogen temperatures. This system will allow for the investigation of the optical properties of stacked monolayers (heterostructures) as well as devices.

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28

Redshaw, Carl. "Oxo and organoimido precursors for non-aqueous polytungstate synthesis." Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328135.

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29

Biddinger, Elizabeth Joyce. "Nitrogen-Containing Carbon Nanofibers as Non-Noble Metal Cathode Catalysts in PEM and Direct Methanol Fuel Cells." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274389015.

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30

Reinhardt, Maxwell James. "Metal complexes containing non-innocent ligands for functional materials." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/11723.

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The existence of complexes of that display non-innocence has been of interest in the field of coordination chemistry since the investigations of square-planar dithiolene complexes of the late transition metals in the 1960s. The ligands used in these systems are termed “non-innocent” when bound to a number of the late transition metals, because the orbital energy levels are similar to those of the central metal ion. This allows there to be significant electron delocalisation over the complex with the potential for the complexes to exist in a number of electronic states due to the combined electrochemical activity. In 1966, Jørgensen classified innocence as ligands that “allow oxidation states of the central atoms to be defined”, thus by this logic non-innocent ligands are defined as complexes where the precise oxidation states of the ligand and metal are ambiguously assigned. However it should be noted that no ligand is inherently non-innocent, but rather the ligand may behave in a non-innocent manner under the right circumstances. The qualification of non-innocence should therefore only be applied to combinations of metal and ligand that result in the aforementioned properties. In this thesis, the term “non-innocent” will be used to define ligands that often possess non-innocent behaviour when complexed to the metal centres they are bound to. A general form of ligand that displays non-innocent behaviour is that of the 1,2-bidentate moiety with an unsaturated carbon backbone. The chelating donor groups (X) are either O, NH, S, or a combination of the three. The central transition metal is generally a late metal that favours a square-planar geometry, because the planarity of the complex is crucial for electron delocalisation within the molecule and molecular interactions in the solid material. When the metal is nickel or platinum for example, their square-planar complexes with such ligands have shown threemembered electron-transfer series. Specific examples of ligands that have been shown to display non-innocent behaviour are those of catechol (1,2-dihydroxybenzene) and 1,2-diaminobenzene, where the unsaturated backbone is provided by a phenyl group. The electronic nature of these compounds has been extensively investigated by the groups of Pierpont and Lever, with focus on their redox and magnetic properties. The combined metal and ligand redox activity results in interesting magnetic behaviour, with potential for magnetic exchange interactions between a paramagnetic metal centre and the radical ligand or between two radical ligands mediated by a diamagnetic metal centre. This research has been advanced by Wieghardt and co-workers who have performed experimental and theoretical examination of non-innocent complexes of 1,2-substituted phenyl chelates, where the donor group is a combination of O and NH. These studies have focused on the understanding the nature of the metal-ligand interactions to apply to biological systems, such as those observed at the active site of enzymes that act upon molecules with similar moieties to the non-innocent ligands. Compounds of catechol may be referred to as dioxolenes in analogy to the sulfur-based dithiolenes. The deprotonated, dianionic form of catechol is known as catecholate (cat), which can be readily oxidised to the monoanionic o-semiquinone (SQ) and neutral o-benzoquinone (Q) forms. It has been seen that catecholate compounds can be described by localised electronic states with defined oxidation states, unlike many of the dithiolene class of molecules. However these states can exist in equilibrium with each other when the metal and ligand orbitals are close in energy, with differences in the charge and spin definition in what has been described as “valence tautomerism”. Therefore, although the complexes may not be seen as non-innocent by definition that their oxidation states are not ambiguous, it is still a useful description due to the potential for easily accessible charge states. Metal dithiolene complexes, where the metal is coordinated by one or more ligands with two S-donor atoms linked by a conjugated backbone, are one of the best researched of the non-innocent class of molecules. The square-planar bis-dithiolenes of the late transition metals have interesting magnetic, optical and electrical properties arising from the delocalised nature of the constituent metal and ligand orbitals, which has enabled their use for a wide range of applications such as non-linear optics, transistors and near-infrared switches. Of particular interest is the ability to fine tune the electrical properties to fit the application by changing the substituents on the core dithiolene moiety. For example, Anthopoulos has shown that by lowering the energy of the lowest unoccupied molecular orbital (LUMO), stable n-channel conductivity can be observed in field-effect transistors (FETs). Materials based on square-planar non-innocent complexes have been tested in FETs, and been seen to display field-effect mobilities as high as 10˗2 cm2 V˗1 s˗1 as with Ni bis(o-diiminobenzo-semiquinonate) complexes. Most of these molecules are based on conjugated, chelating ligands such as 1,2-diaminobenzene and the dithiolene class of molecules. Field-effects have also been observed in square-planar Pt complexes, where the conductivity is thought to arise from beneficial Pt-Pt bonds in addition to the π-stacking between molecules. Despite the similarity to the diaminobenzene and dithiolene counterpart, there are no reports of catechol-based materials displaying field-effect properties in the literature. Catechol compounds are well-researched in the field of biological chemistry due to the prevalence of the catechol moiety and enzymes with which it interacts in nature. However they have not been examined far beyond their simple coordination chemistry or chemical characterisation.

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Asara, Gian Giacomo. "Transition metal carbides as active phase and as support in catalysis: Insights from first principles theoretical modelling." Doctoral thesis, Universitat Rovira i Virgili, 2014. http://hdl.handle.net/10803/454774.

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Els carburs de metalls de transició (TMC) exhibeixen propietats químiques i catalítiques similars a les dels costosos metalls nobles. La conversió d'alcohol, hidrogenació d'olefines i altres reaccions importants han demostrat l'aplicabilitat d'aquests compostos en processos industrials. També se sap que nanopartícules de metalls nobles (NMNPs) mostren una alta activitat catalítica tot i la baixa o nul • la reactivitat del metall sòlid. A més, investigacions recents assenyalen que els suports de TMC polaritzen la densitat electrònica de NMNPs adsorbits i augmenten l'activitat catalítica respecte als suports més tradicionals d'òxid metàl • lic. Aquests descobriments recents han inspirat el treball presentat en aquesta tesi, realitzat mitjançant tècniques actuals de la química quàntica. S'ha estudiat CO, CO2, H2, H2O adsorbits sobre TiC i sobre petits clústers d'or adsorbits en el suport. S'ha considerat la superfície (001), terrasses, esglaons monoatòmics i defectes, i també la reactivitat de les molècules adsorbides sobre la superfície neta de TiC (001) i en dos clústers d'or, Au4 i Au6, adsorbits. Les barreres energètiques calculades per a la formació de metà o formaldehid a partir de gas de síntesi, en TiC (001) resulten ser massa altes i aquests processos són inviables sobre el suport net. Sobre els clústers d'or suportats sobre TiC (001) hi ha una major activitat catalítica, però la reacció continua sent altament impedida. No obstant això, la reacció de desplaçament del gas d'aigua es preveu que sigui ràpida en el sistema Au4/TiC (001), superant els catalitzadors utilitzats normalment en la indústria. Experiments recents mostren que els clústers de Ni, Cu i Au estan fortament deformats un cop adsorbits sobre TMC, donant lloc a catalitzadors molt actius. S'ha investigat la interacció dels àtoms amb la fase delta de MoC. La interacció és més forta pel recobriment més baix considerat, la relaxació de la superfície és important i l'activitat es preveu que augmenti en l'ordre Ni> Cu> Au. Finalment, s'han considerat possibles reconstruccions no polars per a la superfície (001) de Mo2C centrant-se en l'energia d’escissió, la qual és proporcional a l'estabilitat de cada tipus de terminació. Les reconstruccions no polars disminueixen l'energia d’escissió, confirmant l'aplicabilitat dels conceptes clàssics de Tasker per a òxids als TMC. Los carburos de metales de transición (TMC) exhiben propiedades químicas y catalíticas similares a las de los costosos metales nobles. La conversión de alcohol, hidrogenación de olefinas y otras reacciones importantes han demostrado la aplicabilidad de estos compuestos en procesos industriales. También se sabe que nanopartículas de metales nobles (NMNPs) muestran una alta actividad catalítica a pesar de la baja o nula reactividad del metal sólido. Además, investigaciones recientes señalan que los soportes de TMC polarizan la densidad electrónica de NMNPs adsorbidos y aumentan la actividad catalítica respecto a los soportes más tradicionales de óxido metálico. Estos descubrimientos recientes han inspirado el trabajo presentado en esta tesis, realizado mediante técnicas actuales de la química cuántica. Se ha estudiado CO, CO2, H2, H2O adsorbidos sobre TiC y sobre pequeños clusters de oro adsorbidos sobre el suport. Se ha considerado la superficie (001), terrazas, escalones monoatómicos y defectos y, también, la reactividad de las moléculas adsorbidas sobre la superficie limpia de TiC (001) y en dos clusters de oro, Au4 y Au6, adsorbidos. Las barreras energéticas calculadas para la formación de metano o formaldehído a partir de gas de síntesis en la superficie limpia de TiC (001) resultan ser demasiado altas y esos procesos son inviables sobre el soporte limpio. Sobre los clusters de oro soportados sobre TiC (001) hay una mayor actividad catalítica, pero la reacción continúa siendo altamente impedida. Sin embargo la reacción de desplazamiento del gas de agua se prevé que sea rápida en el sistema Au4/TiC (001), superando los catalizadores utilizados normalmente en la industria. Experimentos recientes muestran que los clusters de Ni, Cu y Au están fuertemente deformados una vez adsorbidos sobre TMC dando lugar en catalizadores muy activos. Se ha investigado la interacción de los átomos con la fase delta del catalizador de MoC. La interacción es más fuerte para el recubrimiento más bajo considerado, la relajación de la superficie es importante y la actividad se prevé que aumente en el orden Ni> Cu> Au. Finalmente, se han considerado posibles reconstrucciones no polares para la superficie (001) de Mo2C centrándose en la energía de escisión, que es proporcional a la estabilidad de cada tipo de terminación. Las reconstrucciones no polares disminuyen la energía de escisión, confirmando la aplicabilidad de los conceptos clásicos de Tasker para óxidos a los TMC. Carbides of the early transition metals (TMC) exhibit chemical and catalytic properties that in many aspects are very similar to those of expensive noble metals. Alcohol conversion, hydrogenation of olefins and many others important reactions demonstrated the applicability of these compounds for industrial processes. It is also known that small noble metal nanoparticles (NMNPs) show high catalytic activity despite of the poor reactivity or inertness of the bulk metal. Additionally, recent investigations pointed out that supporting TMCs polarize the electron density of adsorbed NMNPs increasing the catalytic activity respect to more traditional metal oxide supports. These recent discoveries inspired the work reported in this thesis using state-of-the-art quantum chemical techniques. We studied CO, CO2, H2, H2O molecules adsorbed on TiC and on small gold clusters adsorbed thereon. We considered the (001) extended surface, terraces, monatomic steps and kink defective sites. The reactivity of adsorbed molecules on the clean TiC (001) surface and on two gold clusters, Au4 and Au6, adsorbed thereon were also studied. Energy barriers calculated for methane or formaldehyde formation from syngas, on the clean TiC (001) surface were by far too high and those processes are unviable on the clean support. Gold clusters supported by TiC (001) show higher catalytic activity but the reaction continues to be highly hindered. However water gas shift reaction is predicted to be fast on the Au4/TiC(001) system, overtaking catalysts normally used in industry. Recent experiments show that Ni, Cu and Au clusters are strongly perturbed upon adsorption on TMC resulting in extremely active catalysts. We investigated the interaction of those atoms with the delta phase of the MoC catalyst. The interaction is stronger for the lowest coverage considered, the relaxation of the surface important and the activity is predicted to increase in the order Ni>Cu >Au. Finally, we have studied possible non-polar reconstructions of the (001) surface of Mo2C focusing on the cleavage energy, proportional to the stability of each type of termination. The non-polar reconstructions decreased the calculated cleavage energy, confirming the applicability of the classical Tasker’s concepts for oxides to TMCs.

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32

Russier, Vincent. "Contribution à la description théorique de l'interface métal noble / solution électrolytique." Paris 6, 1986. https://hal.science/tel-04577395v1.

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Description théorique de l'interface entre un métal noble et une solution électrolytique. La description de l'interface solution-paroi solide est décrite par le modèle "civilisé" dans lequel les molécules sont des sphères dures portant un dipôle ponctuel et les ions de sphères dures chargées. Détermination du profil de densité des dipôles lorsque ceux-ci interagissent avec la surface ainsi que le profil de densité des ions. Pour l'interface métal noble-vide, calcul du travail de sortie et de l'énergie de surface. Utilisation d'un modèle simple permettant de traiter la surface et de rendre compte de l'hybridation s/d Theoretical description of the interface between a noble metal and an electrolytic solution. The description of the solution-wall solid interface is described by the "civilized" model in which the molecules are hard spheres bearing a point dipole and the ions of charged hard spheres. Determination of the density profile of dipoles when they interact with the surface and the density profile of ions. For noble-vacuum metal interface, calculation of output work and surface energy. Use of a simple model to treat the surface and account for hybridization s/d

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33

Krämer, Tobias. "Electronic structure of open-shell transition metal complexes." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:1f4a1330-281d-4696-b3e6-62b76fb41d65.

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This thesis presents electronic structure calculations on problems related to the bonding in inorganic coordination compounds and clusters. A wide range of molecules with the ability to exist in different structural forms or electronic states has been selected and density functional theory is systematically applied in order to gain detailed insight into their characteristics and reactivity at the electronic level. First, we address the question of redox non-innocent behaviour of bipyridine in a series of 1st row transition metal complexes. Complexes of the type [M(2,2'-bipyridine)(mes)₂]0 (M = Cr, Mn, Fe, Co, Ni; mes = 2,4,6-Me₃C6H₂) and their one-electron reduced forms have been explored. The results clearly show that the anions are best described as complexes of the monoanionic bipyridine radical (Sbpy = 1/2), giving a rationale for the observed structural changes within the ligand. Likewise, we have identified dianionic bipyridine in both the complexes [Zn2(4,4'-bpy)(mes)₄]²− and [Fe(2,2'-bpy)₂]²−. In no case have we found evidence for significant metal-to-ligand backbonding. The subject of redox-noninnocence is further revisited in a comparative study of the two complexes [M(o-Clpap)₃] (M = Cr, Mo; o-Clpap = 2-[(2-chloro-phenyl)azo]-pyridine), and their associated electron transfer series. The results indicate that all electron transfer processes are primarily ligand-based, although in the case of the Mo analogue these are coupled to substantial electron density changes at the metal. The ability of pap to form radical anions finds a contrasting case in the di- nuclear Rh complex [Rh₂(μ-p-Clpap)₂ (cod)Cl₂], where the two ligand bridges act as acceptors of strong dπ∗ backbonding from a formally Rh–I centre. We then direct our attention to the endohedral Zintl clusters [Fe@Ge10]³− and [Mn@Pb12]³−, which reveal peculiar topologies. We have probed the electronic factors that influence their geometric preferences, and propose a model based on the shift of electron density from the endo- hedral metal to the cage to account for the observed geometries. Subsequently, we reassess the electronic structure of the xenophilic clusters Mn₂(thf)₄(Fe(CO)₄)₂ and [Mn(Mn(thf)₂)₃(Mn(CO)₄)₃]–. We conclude that these are best viewed as exchange coupled MnII centres bridged by closed- shell carbonylate fragments. In the closing chapter the reduction of NO₂– to NO by the complex [Cu(tct)(NO₂)]+ (tct = cis,cis-1,3,5-tris(cinnamylideneamino)cyclohexane) is studied, a process that mimics the enzyme-catalysed reaction. Two viable pathways for the reaction have been traced and key inter-mediates identified. Both direct release of NO or via decomposition of a Cu-NO complex are kinetically and thermodynamically feasible.

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34

Heard, Peter John. "Dynamic NMR studies on some stereochemically non-rigid transition metal complexes of azines." Thesis, University of Exeter, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385695.

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Seotsanyana-Mokhosi, Itumeleng. "Photosensitizing properties of non-transition metal porphyrazines towards the generation of singlet oxygen." Thesis, Rhodes University, 2001. http://hdl.handle.net/10962/d1006086.

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Metallophthalocyanine complexes containing non-transition metals are very useful as sensitizers for photodynamic therapy, a cure for cancer that is based on visible light activation of tumour localized photo sensitizers. Excited sensitizers generate singlet oxygen as the main hyperactive species that destroy the tumour. Water soluble sensitizers are sought after for the convenience of delivery into the body. Thus, phthalocyanine (pc), tetrapyridinoporphyrazines (tppa) and tetramethyltetrapyridinoporphyrazines (tmtppa) with non-transition central metal atoms of Ge, Si, Sn and Zn were studied. First was the synthesis of these complexes, followed by their characterisation. The characterisation involved the use of ultraviolet and visible absorption spectroscopy, infrared spectroscopy, nuclear magnetic resonance spectroscopy, electrochemical properties and elemental analysis. Photochemical properties of the complexes were then investigated. Photolysis of these macrocycles showed two processes; -reduction of the dye and photobleaching, which leads to the disintegration of the conjugated chromophore structure of the dye. Photobleaching is the reductive quenching of the excited state of the sensitizers. The intensity of the quenching decreased progressively from tmtppa, tppa to pc metal complexes with photobleaching quantum yields, 6.6 x 10.5⁻¹, 1.8 x 10.5⁻¹ and 5.4 x 10⁻⁶ for Zntmtppa, Zntppa and Znpc, respectively. Efficiency of singlet oxygen sensitization is solvent dependent with very different values obtained for the same compound in different solvents, for example, 0.25 and 0.38 were observed as singlet oxygen quantum yields for Gepc complex in DMSO and DMF respectively. In DMSO the efficiency of ¹O₂ generation decrease considerably from pc to tppa and finally tmtppa. In water Getmtppa exhibits much higher singlet oxygen quantum yield, hence promising to be effective as a sensitizer for photodynamic therapy.

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Zhou, Xiuquan. "Non-hydrolytic Sol-gel (NHSG) Synthesis of Transition Metal Sulfides and Theoretical Investigations." University of Toledo / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1365030696.

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Pascone, Pierre. "Synthesis, characterization, and performance of graphene nanoflakes as a non-noble metal catalyst in polymer electrolyte membrane fuel cells." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117071.

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One of the goals in catalyst research for proton exchange membrane fuel cells (PEMFCs) is to find a cost-efficient alternative to platinum. Due to sluggish kinetics, the major requirement of the platinum comes from the catalyst layer used for the oxygen reduction reaction (ORR). Functionalized carbon nanomaterials present themselves as good candidates for the replacement of platinum due to their low cost, excellent electrical conductivity, and chemical resistance to acidic and basic environments. In this work, graphene nanoflakes (GNFs), which are nanopowders consisting of stacked graphene sheets, were used to support atomic iron as a non-noble metal catalyst. In the first stage of the study the iron-based catalyst was synthesized. Synthesis steps include the production of GNFs in methane plasma, adsorption of ferric acetate, and pyrolysis in ammonia-rich atmosphere. The catalyst structure was characterized at various stages throughout the synthesis steps and it was found that 0.28 atomic percent of iron could successfully be incorporated onto the surface. However, the synthesis method employed caused a general decrease to all calculated crystallinity parameters: purity decreased by 28%, crystallite size decreased by a factor of 2, and the average length of graphene plane decreased by a factor of 4. Characterization was also performed on the catalyst layer after it had been exposed to the PEMFC environment, revealing that the crystallinity parameters actually improved with respect to exposure time: after 100 hours purity increased by 32%, crystallite size increased by 25%, and the average length of graphene plane increased by 107%. Exposure to the PEMFC environment repairs the damage done to the original GNFs during the synthesis steps. The synthesized catalyst was used in the catalyst layer for the ORR of a PEMFC with a 1 cm2 active surface. A current of 150 mA/cm2 was observed at an applied voltage of 0.5 Volts with a catalyst loading of 1 mg. When the current is normalized with respect to the amount of metal present, the result of 11.8 A/mg of metal catalyst from the present catalyst out-performs most platinum-based catalysts being used in industry; current platinum catalyst have values ranging from 3 to 14 A/mg of platinum. In stability experiments, no losses were observed at the end of 100-hours long experiments performed at an applied voltage of 0.5 Volts. This represents a great improvement over comparable iron-based catalysts, which show a 45% loss under identical test conditions. The increased stability of the catalyst support structure demonstrates the advantage of the high crystallinity and large crystalline lengths of the GNFs in comparison to other commercial carbon blacks. Un des objectifs de la recherche sur les catalyseurs pour les piles à combustible à membrane électrolyte polymérique (PCMEP) est de trouver une alternative moins coûteuse au platine. En raison d'une cinétique lente, le platine est surtout utilisé dans la couche de catalyseur au niveau de la cathode pour la réaction de réduction de l'oxygène (RRO). Les nanomatériaux de carbone fonctionnalisés se présentent comme de bons candidats pour le remplacement du platine en raison de leur faible coût, d'une excellente conductivité électrique et d'une résistance chimique aux milieux acides et basiques. Dans ce travail, les nanoflocons de graphène (NFG) constitués en moyenne d'une dixaine de plans de graphène empilées, ont été utilisés comme support aux atomes de fer pour créer un catalyseur métallique non noble. Lors d'une première étape, le catalyseur à base de fer a été synthétisé. Les étapes de synthèse comprennent la production des NFG dans le plasma de méthane, l'adsorption de l'acétate ferrique, et la pyrolyse dans une atmosphère riche en ammoniac. La structure du catalyseur a été caractérisée tout au long des étapes de synthèse, et il a été constaté qu'un pourcentage de 0,28 % en atomes de fer ont été incorporé aux structures NFG. Cependant, la méthode de synthèse utilisée a provoqué une baisse générale de tous les paramètres cristallins calculés: la pureté a diminué de 28%, la taille des cristallites a diminué d'un facteur 2, et la taille moyenne des plans de graphène d'un facteur 4. La caractérisation a été également effectuée sur la couche de catalyseur après avoir été exposée à l'environnement PCMEP, révélant que les paramètres cristallins sont effectivement améliorés avec la durée d'exposition. Au bout de 100 heures, la pureté a augmenté de 32%, la taille des cristallites de 25%, et la taille moyenne des plans de graphène de 107%. L'exposition à l'environnement de PCMEP a réduit les dommages causés aux NFG pendant les étapes de synthèse. Le catalyseur synthétisé a été utilisé pour la RRO dans un PCMEP avec une surface active de 1 cm2. Un courant de 150 mA/cm2 a été observé pour une tension appliquée de 0,5 volts et une masse de catalyseur de 1 mg. Lorsque le courant est normalisé par rapport à la quantité de métal présent, le résultat de 11,8 A/mg de métal surpasse les catalyseurs à base de platine les plus utilisés dans l'industrie. Les catalyseurs au platine ont des valeurs allant de 3 à 14 A/mg de platine. Dans les expériences de stabilité, pour une tension appliquée de 0,5 Volts, aucune perte de courant n'a été observée à la fin des 100 heures de l'expérience. Cela représente une grande amélioration par rapport aux autres catalyseurs à base de fer, qui montrent une perte de 45% dans des conditions expérimentales identiques. La stabilité accrue de la structure du catalyseur démontre l'avantage d'utiliser des NFG par rapport à d'autres nanomatériaux de carbone, grâce à leurs cristallinité élevée et leurs grandes longueurs cristallines.

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38

Wang, Xinde [Verfasser], Regina [Akademischer Betreuer] Palkovits, and Marcel [Akademischer Betreuer] Liauw. "Hydrogenolysis of biomass-derived platform chemicals to glycols over non-noble metal catalysts / Xinde Wang ; Regina Palkovits, Marcel Liauw." Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1217256792/34.

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39

DiPasquale, Antonio Giovanni. "Peroxide complexes of non-redox active metal centers : models for alternative mechanisms in cytochrome P450 oxidations? /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/11603.

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40

Tanveer, Muhammad [Verfasser]. "First-principles electronic theory of non-collinear magnetic order in transition-metal nanowires / Muhammad Tanveer." Kassel : Universitätsbibliothek Kassel, 2015. http://d-nb.info/1072321874/34.

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41

Owen, Nathan. "The investigation of a non-transition metal fluoride as a cathode material for lithium batteries." Thesis, Cranfield University, 2012. http://dspace.lib.cranfield.ac.uk/handle/1826/10237.

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Lithium ion batteries are fast becoming the consumer choice for powering their electronic devices. However, current lithium batteries energy densities are not suf- ﬁciently high, and cost per kWh suﬃciently low, to be widely accepted as batteries in electric vehicles. In order to reduce the cost and increase the energy density it may be necessary to move away from intercalation electrode materials, that are limited by the number of vacant lithium interstitial sites available, to conversion reaction materials that can allow multiple electron transfer. This thesis looks to investigate the use of a non- transition metal ﬂuoride as a cathode material in a primary or secondary lithium battery. Initial results for the ball milled material show speciﬁc energy densities over 2050 Wh/kg. The initial energy density rapidly faded over a period of a few cycles due to the structural change of the material and unwanted reactions with the electrolyte. These were identiﬁed by investigating the mechanism of the one stage discharge and charge proﬁle. To further improve the cycling results nanorods were synthesised which improved the rate capability to provide an energy density of over 1250 Wh/kg at a discharge rate of 0.25C. The capacity over repeated cycling was also improved but the same problems that plagued the ball milled samples were also apparent in the nanorod samples. It was found during the initial investigation of the non-transition metal ﬂuoride material that it is rechargeable, but for a limited number of cycles partly due to its poor kinetics. It has the potential to be a good rechargeable battery material but if not can satisfactorily compete with commercial primary batteries in terms of energy density and cost, as it is a very cheap material.

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42

Cerchez, Vladimir. "Nano structures formed by molecular chlorine interaction with noble metal surfaces : scanning Tunneling Microscopy/Spectroscopy study." Thesis, Nancy 1, 2011. http://www.theses.fr/2011NAN10047/document.

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Ce travail de thèse porte sur une étude systématique des mécanismes d'adsorption et d'interaction du chlore avec les surfaces des métaux Au(111), Ag(111) et Cu(111). Pour cette étude nous avons mis en oeuvre une méthode d'élaboration par réaction gaz/surface en conditions ultra-vide. Les systèmes élaborés ont été étudiés d'un point de vue structural par diffraction d'électrons lents et par microscopie à effet tunnel basse température (5K). Les propriétés électroniques on fait l'objet de mesures de spectroscopie locale par effet tunnel. La première partie de ce travail est dédiée aux modifications structurales induites par l'adsorption du chlore dans le régime sub monocouche et au régime de saturation, qui correspond à l'apparition des stades précurseurs de la formation des halogénures métalliques. A partir de nombreux résultats expérimentaux, nous avons réussi à décrire de façon détaillée les mécanismes d'interaction gaz/surfaces et à proposer des modèles de structures à l'échelle atomique jusqu'alors non résolues. Les modèles proposés ont été validés par des calculs DFT. La seconde partie de la thèse est consacrée aux propriétés électroniques originales de réseaux de puits quantiques formés par auto organisation du chlore à la surface (111) de l'or. Nous avons étudié les résonances quantiques qui se forment par confinement des états électroniques de surface dans des pores de quelques nanomètres de diamètre. Les états propres des puits quantiques ainsi constitués ont été caractérisés en fonction de la taille et de la forme des puits et une modélisation numérique des propriétés spectrales par une approche de type "particule dans une boîte" a complété l'étude expérimentale This work is related to the systematic study of chlorine adsorption mechanism on the metal's surfaces Au(111), Ag(111) and Cu(111). We had used for this study the interaction of chlorine gas with metal surface in ultra-high vacuum conditions. Elaborated systems were characterized from the structural point of view by low-energy electron diffraction and low-temperature scanning tunneling microscopy (5 K). Local electronic properties were probed by scanning tunneling spectroscopy. The first part of the work is devoted to the surface's structural modifications induced by chlorine adsorption from sub-monolayer regime to saturation, which corresponds to the appearance of metal halide precursors. From numerous experimental results we were able to describe in details the mechanism of gas/surface interaction and to propose atomic structural models that remained unresolved up to now. The proposed models were validated by density functional theory calculations. The second part of the thesis is devoted to the study of original electronic properties of the superstructure of quantum wells formed by self-organization of chlorine atoms on (111) surface of gold. We had studied the quantum resonances that appeared due to the confinement of surface electronic states in the pores of few nanometers in diameter. The eigenstates were characterized as a function of the quantum well?s shape and size. This study was completed by numerical modeling of spectroscopic properties of nano-pores in the "particle-in-a-box" limit

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43

Simler, Thomas. "New transition metal complexes with functional N-heterocyclic carbene ligands for molecular activation." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF005.

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Le sujet de cette thèse porte sur l’étude de ligands hybrides incorporant un donneur carbène N-hétérocyclique (NHC). Les ligands phosphine-NHC construits sur le motif m-phénylène ont conduit à des complexes di- ou tétranucléaires d’Ag, Cu, Au et Ir, et à des complexes bimétalliques Ag/Cu et Ag/Ir par transmétallation sélective du site NHC. Dans le cas des ligands phosphino-picoline-NHC (PNC), la transmétallation des sels de Li ou K correspondants a permis d’isoler des complexes « pinceurs » dé-aromatisés du Cr, Fe et Co. La déprotonation du ligand bis(phosphinométhyl)pyridine (PNP) a été examinée, et les ligands dé-aromatisés mono- et bis-anioniques correspondants ont été utilisés dans des réactions de transmétallation vers le Cr(II) et Zr(IV). Différents modes de coordination des ligands dé-aromatisés, notamment une métallation de la position alpha-CHP, ont été observés. La substitution de la phosphine dans PNC par une fonction imine conduit à un ligand hybride « rédox non-innocent » The purpose of this work is the synthesis and study of hybrid and potentially “pincer” ligands featuring an N-heterocyclic carbene (NHC) donor. The phosphine-NHC ligands based on the m-phenylene framework led to di- or tetranuclear Ag, Cu, Au and Ir complexes, and to bimetallic Ag/Cu and Ag/Ir complexes by selective transmetallation of the NHC. With the phosphino-picoline-NHC (PNC) ligands, transmetallation from the corresponding Li or K salts led to dearomatised Cr, Fe and Co “pincer” complexes. Deprotonation of the bis(phosphinomethyl)pyridine (PNP) ligand was also examined. The corresponding dearomatised mono- and bis-anionic ligands were isolated as Li or K salts and further used in transmetallation reactions towards Cr(II) and Zr(IV). Different coordination modes of the dearomatised ligands, including side-arm metallation, were observed. Substitution of the phosphine group in PNC by an imine donor led to a hybrid and “redox non-innocent” ligand

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44

Beeck, Torben [Verfasser]. "Small, Size-Selected and Deposited Clusters on Magnetic and Non-Magnetic 3d Transition Metal Surfaces / Torben Beeck." München : Verlag Dr. Hut, 2015. http://d-nb.info/1074063503/34.

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45

Khatua, Sabyasachi. "Adsorption on late transition metal surfaces : non-linear processes on Ir{100} and anisole on Pt{111}." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615690.

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46

Ranjbar, Sahraie Nastaran [Verfasser], Peter [Akademischer Betreuer] Strasser, and Christina [Akademischer Betreuer] Roth. "Synthesis and characterization of novel non noble metal catalysts for the electrocatalytic oxygen reduction reaction / Nastaran Ranjbar Sahraie. Gutachter: Peter Strasser ; Christina Roth. Betreuer: Peter Strasser." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1066163839/34.

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47

Montoya, Javier Antonio. "Ab-initio study on synthesis of new materials at high pressure : transition-metal nitrides and non-molecular CO2 phases." Doctoral thesis, SISSA, 2007. http://hdl.handle.net/20.500.11767/4802.

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Now, I will proceed with a very brief description of the two main parts that form this thesis work, which are inspired by some new possibilities that high pressure has opened for the synthesis of new phases and compounds. The relevance of these new materials from a practical point of view, lies in the possibility of having them recovered to ambient conditions and then used in a wide variety of technical applications. The two examples covered here, include a new class of transition-metal nitrides, and the synthesis of extended forms of CO2. In Chapter 3, it is shown that the new family of late transition-metal nitrides: PtN2, OsN2 and IrN2, all synthesized at similar conditions ( ∼ 50 GigaPascal and 2000 K) [10, 11], shares common structural properties among its members and opens the door to the synthesis of novel materials of this kind; with possible technological applications since they can be recovered to ambient conditions. The synthesis of these new nitrides is a clear example of how pressure can be used to form compounds between species that do not mix at ambient conditions. Chapter 4 reports our studies on a different class of high pressure synthesis, namely the chemical transformation of a molecular species (CO2) into an extended compound with entirely different mechanical and electronic properties. In particular it reports on the transition that molecular CO2 undergoes at pressures above 40GPa and mild temperatures, into an extended glassy phase. CO2’s pressure-induced phase-transition from a molecular to an extended phase was first observed in 1999 when V. Iota and collaborators at Livermore, obtained a fully tetrahedral silica-like phase of CO2 whose precise structure remains unresolved up to these days [12]. Recently, two new extended phases that show strong similarities among themselves in many aspects, have been reported [13, 14]. The first [13], is a non-molecular amorphous phase named “a-CO2” or “carbonia”, while the second [14], is a crystalline phase indexed by its discoverers as stishovite-like, i.e. with six-fold coordinated carbon atoms, that instead we believe is the crystalline counterpart of carbonia. However, in contrast with what is observed in the case of the transition-metal nitrides, for CO2 no recovery of any of the new extended phases to ambient conditions has yet been possible. In fact, it is observed that a-CO2 and phase VI go back to molecular phases at pressures around 20 GPa which coincides with the pressure at which the crossing between the enthalpies corresponding to the molecular and tetrahedral phases takes place. Finally, also in Chapter 4, I consider some first-principles high-pressure chemistry applied to the problem of the catalysis and recovery of new CO2 extended phases. Here, I will show that by means of introducing a transition metal (TM) as an impurity (Ti in our case) in a CO2 molecular sample (2% concentration) an activation of the amorphization reaction is observed and this leads to a transition that occurs much faster than in the case in which no TM is used. It is also expected that attempts succeeding to lower the transition pressure, will also lead to a lowering of the pressures at which the CO2’s non-molecular phases can be recovered, with the final goal of bringing them to ambient conditions. In summary, in this thesis it is shown how first-principles calculation techniques can be effectively used in high-pressure physics and chemistry research for clarifying very important issues regarding structural and electronic properties that wouldn’t be easily accessible by other means.

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48

El, Assal Z. (Zouhair). "Synthesis and characterization of catalysts for the total oxidation of chlorinated volatile organic compounds." Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526221267.

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Abstract The harmful emissions of chlorinated volatile organic compounds (CVOCs) originate only from man-made sources. CVOCs are used in a variety of applications from pharmaceuticals production to decaffeination of coffee. Currently, CVOC emissions are limited by strict legislation. For these reasons, efficient CVOC abatement technologies are required. Catalytic oxidation is very promising option for this purpose, since catalysts can be tailored to each case to maximize the efficiency and minimize the formation of unwanted products, such as dioxins or Cl2. The goal of this thesis was to study the role of the physico-chemical properties of catalysts in dichloromethane (DCM) oxidation. To reach the aim, several catalytic materials were prepared and characterized, and their performance was tested in total oxidation of DCM. The catalytic materials used were powders of four single metal oxides (γ-Al2O3, TiO2, CeO2, MgO), three mixed oxides (Al2O3-xSiO2) washcoated on a cordierite monolith and four active phases (Pt, Cu, V, Mn). At first, support properties were studied. It was found that the DCM conversion and HCl production are dependent on support acidity when the studied single oxides are considered. The best DCM conversions and HCl yields were observed with the support having the highest total acidity (γ-Al2O3). Further, the quality of the by-products formed was dependent on the type of the acid sites present on the support surface. Secondly, the impregnation of the active compound was observed to improve the selectivity of the material. From the tested active phases, Pt presented the best performance, but also V2O5 and CuO showed almost equal performances. Especially CuO supported on γ-Al2O3, that had less formation of by-products and is less toxic than V-containing oxides, seems to be a promising alternative to Pt. Concerning stability, no deactivation was observed after 55h of testing of Pt/Al2O3. Furthermore, in the used reaction conditions, the formation of CuCl2 is not thermodynamically favoured. Finally, the good characteristics of the powder form catalysts were successfully transferred to the monolith. The performance of the Pt/90Al2O3-10SiO2 catalyst in DCM oxidation was improved when the channel density was increased due to an increase in geometric surface area and mechanical integrity factor, and a decrease in open fraction area and thermal integrity factor Tiivistelmä Haitallisten kloorattujen orgaanisten yhdisteiden (CVOC) päästöt ovat ihmisten aiheuttamia. CVOC-yhdisteitä käytetään mm. liuottimina lääkeaineiden valmistuksessa ja kofeiinin poistossa. Nykyisin CVOC-päästöjä rajoitetaan tiukalla lainsäädännöllä. Näistä syistä tehokas CVOC-yhdisteiden käsittelymenetelmä on tarpeen. Katalyyttinen hapetus on hyvä vaihtoehto tähän tarkoitukseen, koska katalyytit voidaan räätälöidä niin, että puhdistuksen tehokkuus saadaan maksimoitua samalla kun ei-haluttujen tuotteiden, kuten dioksiinit ja kloorikaasu, muodostuminen voidaan minimoida. Tämän väitöskirjatyön tavoitteena oli selvittää katalyyttien fysikaalis-kemiallisten ominaisuuksien yhteyksiä dikloorimetaanin (DCM) hapetukseen. Tavoitteen saavuttamiseksi valmistettiin useita katalyyttejä, jotka karakterisoitiin ja testattiin DCM:n kokonaishapetuksessa. Työssä tutkittiin neljää jauhemaista metallioksidia (γ-Al2O3, TiO2, CeO2 ja MgO), kolmea metallioksidiseosta (Al2O3-xSiO2), jotka pinnoitettiin kordieriittimonoliitille, sekä neljää aktiivista ainetta: Pt, Cu, V and Mn. Aluksi työssä keskityttiin tukiaineiden ominaisuuksiin. Työn tulokset osoittivat, että DCM:n konversio ja HCl:n tuotanto ovat riippuvaisia tukiaineen happamuudesta. Paras tulos saavutettiin alumiinioksidilla, jolla oli korkein kokonaishappamuus. Lisäksi havaittiin, että sivutuotteiden laatu riippuu tukiaineen pinnalla olevien happopaikkojen tyypistä. Aktiivisen aineen impregnointi tukiaineeseen paransi materiaalin selektiivisyyttä. Tutkituista aineista Pt osoittautui parhaimmaksi, mutta myös V2O5 ja CuO olivat lähes yhtä hyviä. Erityisesti CuO-katalyytti, joka tuotti vähemmän sivutuotteita ja joka on materiaalina vähemmän haitallinen kuin V2O5, osoittautui lupaavaksi jalometallikatalyyttien korvaajaksi. Materiaalien stabiilisuuteen liittyen Pt/Al2O3-katalyytin toiminnassa ei havaittu muutoksia 55 tunnin testauksen jälkeen. Lisäksi CuCl2:n muodostuminen ei mallinnuksen mukaan ole termodynaamisesti todennäköistä tutkituissa reaktio-olosuhteissa. Jauhemaisen katalyytin hyvät ominaisuudet pystyttiin pinnoituksessa siirtämään monoliittirakenteiseen katalyyttiin. Pt/90Al2O3-10SiO2 -katalyytin aktiivisuus DCM:n hapetuksessa tehostui, kun monoliitin aukkoluku kasvoi aiheutuen suuremmasta geometrisestä pinta-alasta ja mekaanisesta eheystekijästä sekä pienemmästä avoimen pinnan osuudesta ja termisestä eheystekijästä

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Cartié, Bernard. "Etude d'iso et d'heteropolyanions du molybdene pentavalent et hexavalent en milieu non aqueux : anions dodecamolybdosulfates et octodecamolybdodisulfates non reduits et partiellement reduits." Orléans, 1987. http://www.theses.fr/1987ORLE2029.

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50

Xiang, Yixian [Verfasser], Ulrich [Akademischer Betreuer] [Gutachter] Kortz, Gerd-Volker [Gutachter] Röschenthaler, Thomas [Gutachter] Heine, and Josep M. [Gutachter] Poblet. "Synthesis, Characterization and Properties of 3d Transition Metal-Substituted Polyoxotungstates and Polyoxo-noble-metalates / Yixian Xiang ; Gutachter: Ulrich Kortz, Gerd-Volker Röschenthaler, Thomas Heine, Josep M. Poblet ; Betreuer: Ulrich Kortz." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2014. http://d-nb.info/111884730X/34.

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Dissertations / Theses on the topic 'Non noble transition metal'

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