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Smith, Adrien. "Activation and reduction of CO2 by metalloporphyrin-based molecular catalysts". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF039.
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La transformation du CO₂ en formes réduites valorisables du carbone constitue une approche vers le recyclage de ce gaz à effet de serre, en réintroduisant dans le cycle du carbone des synthons C1 qui ne sont pas issus de ressources fossiles. Les tétraphénylporphyrines de fer et leurs dérivés se sont révélés être des catalyseurs moléculaires efficaces et sélectifs pour la réduction du CO₂ en CO. L'introduction de différentes fonctions dans la seconde sphère de coordination des porphyrines a aussi permis d'améliorer la surtension et les taux catalytiques.Inspirés par la poche distale des centres actifs des enzymes, une porphyrine de fer avec une anse portant une fonction carboxylate est étudiée. Les investigations électrochimiques, cinétiques, et de chimie computationnelle montrent que ce catalyseur permet de réduire fortement la surtension nécessaire à la catalyse tout en conservant des taux catalytiques très élevés. Il est proposé que la fonction carboxylate, initialement ligand axial du métal, joue en conditions catalytiques le rôle important dans l'insertion et la transformation du CO₂.Ensuite, deux porphyrines de fer ont été synthétisées avec un imidazolium à différentes positions par rapport au centre métallique. L'objectif premier était d'établir une corrélation entre la distance de la fonction cationique et les propriétés du catalyseur, afin de guider la conception de nouveaux catalyseurs plus performants.Cependant, l'étude électrochimique de ces composés révèle que ces groupements imidazolium peuvent être électroactifs. La résonance paramagnétique électronique a été utilisée afin de décrire leurs différentes formes réduites. Ces travaux ont amené à dévoiler la nature électroactive de ces groupements imidazolium portés par ces nouvelles porphyrines de ferTransforming CO₂ into valuable reduced forms of carbon is an interesting approach towards the recycling of this greenhouse gas, by introducing non-fossil fuel based C1 building blocks back into the carbon cycle. Tetraphenyl iron porphyrins and derivatives have been shown to be efficient and selective molecular catalysts for CO₂ reduction to CO. The introduction of various functions in the second coordination sphere of porphyrins showed great improvements of both the overpotential and the catalytic rates.Inspired by the distal pocket of enzymatic active centers, an iron porphyrin with a carboxylate strap is investigated. Electrochemical, kinetic and computational chemistry studies show that this catalyst operates at a low overpotential, while maintaining high catalytic rates. It is proposed that the carboxylate function, initially acting as an axial ligand of the metal, plays an important role in the insertion and transformation of CO₂, in synergy with a water molecule trapped in the superstructure.Furthermore, two iron porphyrins were synthetized bearing an imidazolium group at various positions with respect to the metal center. The original goal of this study was to establish a correlation between the distance of the cationic group from the metal center and the catalytic performances of the catalyst, which can guide the design of new catalysts for CO₂ reduction.The electrochemical study of these catalysts revealed that these imidazolium functions can be electroactive. Electron paramagnetic resonance was used to describe their various reduced forms. These studies revealed and describe the potential electroactive behavior of the imidazolium groups on these novel iron porphyrins catalysts
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Afonso, Joana da Costa Franco. "Catalytic hydrogenation of carbon dioxide to form methanol and methane". Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/10854.
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Woolerton, Thomas William. "Development of enzymatic H2 production and CO2 reduction systems". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:393741ac-94b1-4d56-b680-d9a434db77e2.
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One of today’s most pressing scientific challenges is the conception, development and deployment of renewable energy technologies that will meet the demands of a rapidly increasing population. The motivation is not only dwindling fossil fuel reserves, but also the necessary curtailment of emissions of the greenhouse gas carbon dioxide (a product of burning fossil fuels). The sun provides a vast amount of energy (120,000 TW globally), and one major challenge is the conversion of a fraction of this energy into chemical energy, thereby allowing it to be stored. Dihydrogen (H₂) that is produced from water is an attractive candidate to store solar energy (a ‘solar fuel’), as are high energy carbon-containing molecules (such as CO) that are formed directly from carbon dioxide. One key aspect is the development of catalysts that are able to offer high rates and efficiencies. In biology, some microbes acquire energy from the metabolism of H₂ and CO. The biological catalysts - enzymes - that are responsible are hydrogenases (for the oxidation of H₂ to protons); and carbon monoxide dehydrogenases (CODHs, for the oxidation of CO to CO₂). These redox enzymes, containing nickel and iron as the only metals, are extraordinary in terms of their catalytic characteristics: many are fully reversible catalysts and offer very high turnover frequencies (thousands per second are common), with only tiny energy input requirements. This Thesis uses a hydrogenase from the bacterium Escherichia coli, and two CODHs from the bacterium Carboxydothermus hydrogenoformans, as the catalysts in H2 production and CO₂ reduction systems. Chapter 3 describes the concept and development not of a solar fuel system, but of a device that catalyses the water-gas shift reaction (the reaction between CO and water to form H₂ and CO₂) - a process of major industrial importance for the production of high purity H₂. Chapters 4, 5 and 6 detail photochemical CO₂ reduction systems that are driven by visible light. These systems, operating under mild, aqueous conditions, involve CODHs attached either to TiO₂ nanoparticles that are sensitised to visible light by the co-attachment of a ruthenium-based dye complex, or to cadmium sulfide nanomaterials that, having a narrow band gap, are inherently photoexcitable by visible light. The motivation here is not the construction of technological devices; indeed, the enzymes that are used are fragile, highly sensitive to oxygen, and impossible to scale to industrial levels. Rather, the drivers are those of scientific curiosity (can the incorporation of these remarkable biological catalysts enable the creation of outstanding solar fuel devices?), and of producing systems that serve as benchmarks and inspiration for the development of fully synthetic systems that are robust and scalable.
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Pršlja, Paulina. "Theoretical Studies of Single-Site Catalysts for Efficient Electrochemical CO2 Reduction". Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/671468.
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El desenvolupament de l’electroquímica té el potenciar d’utilizar el CO2 com a matèria primera per a la producció sostenible de compostos i materials i té un gran impacte en la indústria química. El catalitzador “de lloc únic” (single site catalyst) és un material prometedor per aconseguir elevades activitats y selectivitats cap a la formació de CO i hidrocarburs C1. L’estructura única d’aquest catalitzador derivat de carboni redueix la competència d’aquests processos amb d’altres processos catalítics com la hydrogen evolution reaction (HER) perquè el single site catalyst requereix la unió de l’hidrogen a la part superior. En aquesta tesi s’han aplicat mètodes DFT i conceptes electroquímics per tal d’entendre els processos de reducció de CO2. Al tercer capítol es descriu la importància de les característiques estructurals del single site catalyst, juntament amb els conceptes relacionats amb la química de coordinació necessaris per a entendre l’activitat del catalitzador en la reacció electroquímica de reducció del CO2 (eCO2RR). L’objectiu del capítol 4 és establir correlacions experimentals i teòriques entre les propietats fisicoquímiques i catalítiques de la eCO2RR que dona com a producte CO per al catalitzador del MNC. El procés de reconstrucció de les nanopartícules de Ni mitjançant la desintegració de Ni(CO)2 en materials de carboni dopats amb N es descriu al capítol 5. Per últim, en el capítol 6 es descriu la selectivitat dels productes de reducció de CO2 tenint en compte com afecta el potencial i la temperatura sobre el catalitzador modelat de CoTPP/MWCNT.El desarrollo de la electroquímica tiene el potencial de utilizar el CO2 como materia prima para la producción sostenible de compuestos y materiales y tiene un gran impacto en la industria química. El catalizador “de sitio único” (single site catalyst) es un material prometedor para lograr una elevada actividad y selectividad hacia CO e hidrocarburos C1. La estructura única de este catalizador derivado de carbono reduce la competencia de estos procesos con otros procesos catalíticos como la reacción hydrogen evolution reaction (HER) porque el single site catalyst requiere la unión de hidrógeno en la parte superior. En esta tesis, métodos DFT y conceptos electroquímicos computacionales han sido aplicados para entender los procesos de reducción de CO2. En el capítulo 3 se describe la importancia de las características estructurales del single site catalyst, además de los conceptos relacionados con la química de coordinación que se aplican para comprender la actividad del catalizador en la reacción electroquímica de reducción de CO2 (eCO2RR). El objetivo del capítulo 4 es establecer correlaciones experimentales y teóricas entre las propiedades fisicoquímicas y catalíticas para la eCO2RR hacia CO para el catalizador del MNC. El proceso de reconstrucción de las nanopartículas de Ni mediante la desintegración de Ni(CO)2 en materiales de carbono dopados con N se describe en el capítulo 5. Por último, en el capítulo 6 se describe la selectividad de los productos de reducción de CO2 teniendo en cuenta cómo afecta el potencial y la temperatura sobre el catalizador modelado de CoTPP/MWCNT.
The development of electrochemistry has the potential to use CO2 as a feedstock for the sustainable production of chemicals and materials and it has an important impact on the chemical industry. Single site catalyst is a promising new material for achieving high activity and selectivity towards CO and C1 hydrocarbons. The unique structure of carbon-based catalyst makes it a good compressor of competing Hydrogen evolution reaction (HER) because the single site requires an ontop binding of hydrogen. In this thesis, I applied DFT methods and computational electrochemical concepts for understanding the processes of CO2 reduction (eCO2RR). In chapter 3 I described the importance of single-site structural features catalyst, besides the basic concept of the coordination chemistry that is applied to understand eCO2RR activity of the catalyst. The aim of chapter 4 was to establish experimental and theoretical correlations between physicochemical and catalytic properties for the eCO2RR towards CO for MNC catalyst. The process of reconstruction of Ni nanoparticles by the disintegration of Ni(CO)2 on N-doped carbon materials is described in chapter 5. Finally, in chapter 6 I unraveled the selectivity of CO2 reduction products that were influenced by potential and the temperature over modeled CoTPP/MWCNT catalyst.
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Dattila, Federico. "Modelling and mapping pathways of electrochemical CO2 reduction on modified catalytic surfaces". Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670954.
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La reducció de CO2 és l'únic procés per generar combustibles verds amb un impacte negatiu net en les emissions de CO2. Per tant, el desenvolupament futur de la nostra societat necessita una aplicació industrial d'aquesta tecnologia per produir productes químics d'ús intensiu com l'etilè. El coure és un material únic per catalitzar aquests productes, però, avenços significatius en aquest procés requereixen una comprensió teòrica profunda de la seva complexitat.
En aquesta tesi em vaig proposar desenvolupar mètodes teòrics per abordar els principals factors involucrats en la reducció de CO2 amb coure: (i) reconstrucció superficial a causa de potencial negatiu; (ii) efectes químics sobre la selectivitat; i (iii) l'efecte de l'electròlit. Els capítols I i II es van dedicar a les motivacions i mètodes i el Capítol 3 a comprovar resultats experimentals ben establerts. En el capítol 4 vaig investigar la reconstrucció del coure policristal·lí a potencials negatius. Aquest procés està impulsat per la polarització de la superfície, que promou dominis (100) i defectes. Seguint les previsions teòriques, vaig sintetitzar un catalitzador a base de coure eficaç per produir etilè amb alt rendiment. En el capítol V, vaig estudiar l'òxid de coure per investigar l'estat d'oxidació del coure, la seva coordinació i els llocs superficials actius cap a la producció de químics C2+. Entre els resultats, vaig demostrar que la polarització impulsa la reducció de CO2, mentre un nou intermedi, el glioxilato desprotonado, millora la selectivitat fins als C2+. En el capítol VI em vaig dedicar a efectes químics que influencien la reactivitat el coure. Adatomos de sofre, que actuen com a centres d'ancoratge, permeten la generació de formiat. Finalment, a l'apèndix A vaig introduir l'efecte dels cations sobre la reducció de CO2, que encara no es comprèn completament, però té una clara rellevància en la distribució del producte.La reducción de CO2 es el único proceso para generar combustibles verdes con un impacto negativo neto en las emisiones de CO2. Por lo tanto, el desarrollo futuro de nuestra sociedad necesita una aplicación industrial de esta tecnología para producir productos químicos de uso intensivo como el etileno. El cobre es un material único para catalizar estos productos, sin embargo, avances significativos en este proceso requieren una comprensión teórica profunda de su complejidad. En esta tesis me propuse desarrollar métodos teóricos para abordar los principales factores involucrados en la reducción de CO2 con cobre: (i) reconstrucción superficial debido a potencial negativo; (ii) efectos químicos sobre la selectividad; y (iii) el efecto del electrolito. Los capítulos I y II se dedicaron a las motivaciones y métodos y el Capítulo 3 a comprobar resultados experimentales bien establecidos. En el capítulo 4 investigué la reconstrucción del cobre policristalino a potenciales negativos. Este proceso está impulsado por la polarización de la superficie, que promueve dominios (100) y defectos. Siguiendo las previsiones teóricas, sinteticé un catalizador a base de cobre eficaz para producir etileno con alto rendimiento. En el Capítulo V, estudié el óxido de cobre para investigar el estado de oxidación del cobre, su coordinación y los sitios superficiales activos hacia la producción de químicos C2+. Entre los resultados, demostré que la polarización impulsa la reducción de CO2, mientras un nuevo intermedio, el glioxilato desprotonado, mejora la selectividad hasta los C2+. En el capítulo VI me dediqué a efectos químicos que influencian la reactividad del cobre. Adatomos de azufre, que actúan como centros de anclaje, permiten la generación de formiato. Finalmente, en el Apéndice A introduje el efecto de los cationes sobre la reducción de CO2, que aún no se comprende completamente, pero tiene una clara relevancia en la distribución del producto.
CO2 reduction is the only process which can generate green fuels with a net negative impact in CO2 emissions. Therefore, the future development of our society needs an industrial scale up of this technology, involving the production of heavily used chemicals such as ethylene. Copper is a unique material for catalyzing these C2+ products, however significant advances need a deep theoretical understanding of the complexity of this material under CO2 reduction conditions. In this thesis I aimed at developing theoretical methods to address the main factors involved in this process: (i) surface reconstruction at negative potential; (ii) chemical effects on copper selectivity; and (iii) the effect of the electrolyte. Chapters I and II were dedicated to the motivations and methods. After having benchmarked in Chapter 3 well-established experimental results, such as the morphology dependence of CO2 product distribution on copper local morphology, I investigated the reconstruction of polycrystalline copper at negative potentials. This process is driven by local surface polarization, which destabilizes close-packed domains and promotes (100) facets and defects. Following theoretical guidelines, I synthesized an effective copper-based catalyst with produced ethylene at high yield and high current density. In Chapter V I studied a complex oxide-derived copper material to provide insights about copper oxidation state, its coordination and surface ensembles active toward C2+ chemicals. Among the outcomes, I demonstrated that polarization drives CO2 reduction activity, whilst a newly reported intermediate, a deprotonated glyoxylate, triggers C2+ selectivity. In chapter VI I dedicated to chemical effects on copper reactivity. Sulfur adatoms, acting as strong tethering centers enable the generation of formate, a chemical employed as preservative for animal food stock. Finally, in Appendix A I introduced cation effect on CO2 reduction, not yet fully understood but having a clear relevance on product distribution.
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Fugate, Elizabeth Anne. "Investigation of Electronic Structure Effects of Transition Metal Oxides toward Water Oxidation and CO2 Reduction Catalysis". The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462868623.
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Chakraborty, Sumit. "Homogeneous Catalysis of Nickel Hydride Complexes Bearing a Bis(phosphinite) Pincer Ligand". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342716471.
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Frogneux, Xavier. "Transformations réductrices du CO2 pour la formation de liaisons C-N et C-C". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112136/document.
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Dans le monde actuel, le dioxyde de carbone (CO2) est le déchet majoritaire issu de l’utilisation des ressources fossiles mais il est encore peu utilisé dans les applications à grande échelle. Afin de tirer parti de son abondance, le développement de nouvelles transformations chimiques du CO2 pour accéder à des produits de chimie fine connait un intérêt croissant au sein de la communauté scientifique. Tout particulièrement, la formation de liaison(s) C-N à partir du CO2 et d’un substrat azotés permet d’accéder à des produits à hautes valeurs énergétiques et commerciales. Un second type de transformation désirable est la formation de liaison C-C à partir du CO2 afin de synthétiser des dérivés d’acides carboxyliques comme des esters. L’utilisation d’hydrosilanes, réducteurs doux, permet de travailler sous 1 bar de CO2 avec des catalyseurs à base de métaux peu coûteux et abondants tels que le fer et le zinc ou bien avec des organocatalyseurs. Les synthèses de formamides, de méthylamines ou d’aminals à partir du CO2 ont ainsi été développées par hydrosilylation. Enfin, la carboxylation des carbosilanes à partir du CO2 a été développée pour la première fois avec un catalyseur à base de cuivre. Dans le cas des 2-pyridylsilanes, l’utilisation de sels de fluorures pentavalents permet d’activer le substrat efficacement sans catalyseurIn the current world, carbon dioxide (CO2) is the major waste of the massive utilization of fossil resources but only few applications have been developed using this compound. In order to take advantage of its abundancy, the development of novel chemical transformation of CO2 to produce fine chemicals is of high interest in the scientific community. In particular, the formation of C-N bond(s) from CO2 and amine compounds unlocks a new way to access high energy and value-added. A second type of highly desirable transformation is the formation of C-C bonds with CO2 so as to synthesize carboxylic acid derivatives. The utilization of hydrosilanes as mild reductants allows the reactions to proceed under 1 bar of CO2 with abundant and cheap metal-based catalysts (iron, zinc) or with organocatalysts. The synthesis of formamides, methylamines and aminals from CO2 are described herein. Ultimately, the catalytic carboxylation of carbosilanes has been achieved for the first time using copper-based complexes. In the specific case of 2-pyridylsilanes, the use of pentavalent fluoride salts allowed us to perform the reaction without catalyst
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Giang, Hannah. "Rational Fabrication of Molybdenum Disulfide and Metal-doped Molybdenum Disulfide Thin Films via Electrodeposition Method for Energy Storage, Catalysis, and Biosensor Applications". OpenSIUC, 2020. https://opensiuc.lib.siu.edu/dissertations/1861.
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This dissertation presents studies electrodeposited MoS2 and metal-doped MoS2 thin films, and their performance for energy storage, catalysis, and biosensor applications. Ni-doped MoS2 thin films were fabricated by electrodeposition from electrolytes containing both MoS42- and varying concentrations of Ni2+, followed by annealing at 400 ºC for 2 h in an Ar atmosphere. The film resistivity increased from 11.3 µΩ-cm for un-doped MoS2 to 32.8 µΩ-cm for Ni-doped MoS2 containing 9 atom% Ni. For all Ni dopant levels studied, only the x-ray diffraction (XRD) pattern expected for MoS2 is observed, with the average grain size increases with increasing Ni content. Ni-doped MoS2 thin films were tested for their activity towards the hydrogen evolution reaction (HER) in 0.5M H2SO4. Tafel equation fits reveal that the catalytic activity for HER, as measured by the exchange current density, increases up to 6 atom% Ni, and then decreases slightly for 9 atom% Ni. Ni-doped MoS2 thin films were also tested in 1.0 M Na2SO4 for use within electrochemical supercapacitors, and the capacitance per unit area increases by 2-3x for 9 atom% Ni-doped MoS2 relative to un-doped MoS2. The highest specific capacitance obtained for Ni-doped MoS2 during galvanostatic charge-discharge measurements is ~300 F/g
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Kour, Gurpreet. "First principles investigations on transition metal based electrocatalysts for efficient clean energy conversion". Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232798/1/Gurpreet_Kour_Thesis.pdf.
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This dissertation relates to the application of density functional theory to the design of novel nanoelectrocatalysts for various electrochemical reduction reactions such as carbon dioxide reduction reactions, carbon monoxide reduction reactions and nitrogen reduction reactions. Many electrocatalysts with high activity, excellent selectivity and stability were designed and engineered using first principle calculations. These findings could potentially guide the experimentalists for creating clean and sustainable energy resources.
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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 catalyseA 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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Ángeles-Boza, Alfredo M. "The importance of heavy atom isotope effects in the elucidation of mechanistic details in small molecule activation reactions". Revista de Química, 2017. http://repositorio.pucp.edu.pe/index/handle/123456789/123963.
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La medición de efectos isotópicos es una herramienta importante en el estudio de las transformaciones químicas. El uso de efectos isotópicos de átomos ligeros como el deuterio es muy común e incluso aparece en muchos textos básicos de química. Lamentablemente, el uso de efectos isotópicos de átomos pesados no ha recibido la misma atención a pesar de su gran utilidad. Este manuscrito sirve como introducción a este tema importante.The determination of isotope effects is an important tool in the study of chemical transformations. Very common in the literature is the use of deuterium isotope effects, which is typically covered in many textbooks. Unfortunately, heavy atom isotope effects have not received the same attention despite its great relevance. This article will serve as an introduction to this very important topic.
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Ma, Bing. "Catalyse moléculaire de la réduction photochimique du CO2 à l’aide de complexes de cobalt en conditions homogène et supportée". Thesis, Université de Paris (2019-....), 2020. http://www.theses.fr/2020UNIP7006.
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La production photocatalytique de carburants solaires est un moyen efficace de stockage chimique de l'énergie solaire et offre une option potentiellement fructueuse pour parvenir à un système énergétique à zéro émission de carbone. La pierre angulaire d'un processus pratique de production de carburant solaire est de concevoir et d'optimiser des photocatalyseurs stables, efficaces et déployables à grande échelle, et comprenant un matériau semi-conducteur permettant l'absorption de photons, la génération efficace de porteurs de charge, leur transport jusqu’à la réalisation de réactions catalytiques.La catalyse moléculaire joue un rôle essentiel dans la photosynthèse naturelle et artificielle. Dans ce travail de doctorat, j’ai étudié (i) un complexe bimétallique pour la réduction sélective du CO2, illustrant le fait que la catalyse moléculaire est l'un des moyens prometteurs pour mettre en œuvre la coopérativité des métaux avec des activités intrinsèques exceptionnelles ; (ii) des matériaux inorganiques (nitrure de carbone semi-conducteur et acide graphitique) pouvant être fonctionnalisés par une molécule (complexe quaterpyridine de cobalt) par le biais d’une liaison amide covalente. Une hétérogénéisation efficace des deux composants a été réalisée. Ces systèmes hybrides ont montré des performances catalytiques élevées vis-à-vis de la photoréduction au CO2. Ils illustrent que le développement de catalyseurs moléculaires vaut la peine d'être exploré afin de parvenir à des systèmes catalytiques évolutifs qui sont nécessaires pour la production pratique de carburant solaire à grande échelle. Dans le mécanisme de fonctionnement des catalyseurs moléculaires supportés par des matériaux, des défis subsistent en ce qui concerne à la fois la stabilité de l’unité moléculaire, les techniques d'hétérogénéisation et le contrôle de l'interaction électronique entre les composantsPhotocatalytic solar fuel production is an effective means of chemical storage for solar energy and it provides a potential fruitful option for achieving a zero-emissions energy system. The cornerstone of a practical solar fuel production process is to design and optimize stable, efficient, and scalable photocatalysts, including a semiconductor material that accommodates photon absorption, efficient charge carriers generation, transport, and then catalytic reactions. Molecular catalysis plays an essential role in both natural and artificial photosynthesis. In this doctoral work, I have (i) investigated a bimetallic complex for selective CO2 reduction, illustrating that molecular catalysis is one of the promising way to activate metal cooperativity with outstanding intrinsic activities; (ii) synthesized inorganic material (semiconductive carbon nitride and graphitic acid) able to be functionalized with a molecular molecule (cobalt quaterpyridine) through a covalent amide bond. Effective heterogenization of the two components was thoroughly accessed. These hybrid systems showed high catalytic performance towards CO2 photoreduction. They illustrate that the development of molecular catalysts is worth to be explored for the invention of scalable catalytic systems that are needed for large scale, practical solar fuel production. In the mechanism of material-supported molecule catalysts, challenges still remain regarding both to molecular stability, heterogenization techniques, and control of the electronic interaction between these components
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Witt, Suzanne Elizabeth. "Dirhodium(II,II) Complexes as Electrocatalysts for Sustainable Energy Applications: Tunable Selectivity For H+ or CO2 Reduction". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu150047691466017.
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Zhang, Yan. "SURFACE AND STRUCTURAL MODIFICATION OF CARBON ELECTRODES FOR ELECTROANALYSIS AND ELECTROCHEMICAL CONVERSION". UKnowledge, 2018. https://uknowledge.uky.edu/chemistry_etds/96.
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Electrocatalysis is key to both sensitive electrochemical sensing and efficient electrochemical energy conversion. Despite high catalytic activity, traditional metal catalysts have poor stability, low selectivity, and high cost. Metal-free, carbon-based materials are emerging as alternatives to metal-based catalysts because of their attractive features including natural abundance, environmental friendliness, high electrical conductivity, and large surface area. Altering surface functionalities and heteroatom doping are effective ways to promote catalytic performance of carbon-based catalysts. The first chapter of this dissertation focuses on developing electrode modification methods for electrochemical sensing of biomolecules. After electrochemical pretreatment, glassy carbon demonstrates impressive figures-of-merit in detecting small, redox-active biomolecules such as DNA bases and neurotransmitters. The results highlight a simplified surface modification procedure for producing efficient and highly selective electrocatalysts. The next four chapters focus on evaluating nitrogen-doped carbon nano-onions (𝑛-CNOs) as electrocatalysts for oxygen reduction and CO2 reduction. 𝑛-CNOs exhibit excellent electrocatalytic performance toward O2 to H2O reduction, which is a pivotal process in fuel cells. 𝑛-CNOs demonstrate excellent resistance against CO poisoning and long-term stability compared to state-of-the-art Pt/C catalysts. In CO2 electrochemical conversion, 𝑛-CNOs demonstrate significant improvement in catalytic performance toward reduction of CO2 to CO with a low overpotential and high selectivity. The outstanding catalytic performance of 𝑛-CNOs originates from the asymmetric charge distribution and creation of catalytic sites during incorporation of nitrogen atoms. High contents of pyridinic and graphitic N are critical for high catalytic performance. This work suggests that carbon-based materials can be outstanding alternatives to traditional metal-based electrocatalysts when their microstructures and surface chemistries are properly tailored.
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Migliaccio, Luca. "Bimetallic catalysts for CO2 electroreduction". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14470/.
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Over the last decades, many steps have been taken in the search for an effective method to reduce carbon dioxide to small organic molecules that can be used as fuel or building blocks for the chemical industry. The object of this work is to prepare two bimetallic electrocatalysts utilizing Cu combined with Au or In for the efficient and selective reduction of CO2 to CO, HCOOH and small fuels molecules. The copper-gold electrode is prepared through the electrodeposition of Cu on the surface of Au, using the underpotential deposition (UPD) technique to obtain a copper monolayer. The prepared electrode shows a high current density compared to Au electrode. Bimetallic metal oxides of CuInO2 is used as the precursor to prepare Cu-In alloys electrodes for electrochemical reduction of CO2. The electrocatalyst preparation is carried out using a thermal reducing treatment able to form different catalytic surfaces with different Cu-In alloys or single-phase metals. The best sample shows a high faradaic efficiency toward CO (71%) at the low overpotential of −0.8 V vs RHE. This study shows two examples of scalable and inexpensive preparation methods of bimetallic surfaces, which may use as selective electrocatalysts for the aqueous reduction of CO2.
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Perazio, Alessandro. "Electrolyzer and Catalyst Engineering for Acidic CO2 Reduction". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS438.
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Le projet est axé sur la réduction électrochimique du CO2 avec des catalyseurs hétérogènes. Grâce à la configuration "gas-fed flow cell" développée dans le groupe, des densités de courant élevées peuvent être atteintes à des surtensions pas si négatives. La première partie du projet est plus axée sur l'efficacité globale de l'électrolyseur. Pour l'optimiser, nous travaillons à trouver le meilleur électrolyte acide pour le système et, en parallèle, nous essayons d'augmenter la fraction de CO2 qui est convertie en produits souhaités. La deuxième partie du projet s'est concentrée sur l'optimisation de la tension du réacteur, visant à minimiser la consommation énergétique du processus de réduction. Enfin, la dernière partie a été consacrée à la modification de surface du catalyseur afin d'obtenir une meilleure sélectivité pour les produits carbonés les plus valorisésThe project focuses on the electrochemical reduction of CO2 with heterogeneous catalysts. Thanks to the "gas-fed flow cell" configuration developed in the group, high current densities can be achieved at moderate overpotentials. The first part of the project is more focused on the overall efficiency of the electrolyzer. To optimize it, we work to find the best acidic electrolyte for the system and, in parallel, we try to increase the fraction of CO2 that is converted into the desired products. The second part of the project focused on optimizing the reactor voltage, aiming to minimize the energy consumption of the reduction process. Finally, the last part was devoted to the surface modification of the catalyst in order to obtain better selectivity for the most valuable carbon products
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SASSONE, DANIELE. "Single metal atom catalysts for the electrochemical reduction of CO2". Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2971997.
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ANNAMALAI, ABINAYA. "Electrochemical Energy Conversion Catalysts for Water Oxidation and CO2 Reduction". Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1086344.
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Numerous efforts have been made for the development of renewable energies to replace fossil fuels and thus reduce greenhouse gas emissions. Renewable energy has the advantage of having a limitless supply over time and is clean. This thesis reports on novel transition metal-based electrocatalysts for acidic water splitting and CO2 reduction, which are two significant technologies to produce chemical fuels (i.e. H2 and C-based compounds) from renewable electricity. The target is to develop and investigate cost-effective, stable, and efficient electrocatalysts for acidic water splitting and CO2 reduction, replacing noble metals and achieving performances above the current state of the art.
In the first part, the preparation and oxygen evolution properties of the oxygen plasma-treated and acid-activated carbon paper are investigated. This part also presents the Ru incorporated Carbon paper, as an efficient, stable, and self-standing catalyst for OER in acid. This catalyst shows an overpotential of 230 mV vs. RHE at 1 mA cm−2, comparable to the other carbon-based materials. It shows a small Tafel slope of 74 mV dec-1 and 20 hours of stability at 10 mA cm−2.
In the second part, the template-assisted wet synthesis and electrochemical OER studies of yolk-shell Co3O4/Co1−xRuxO2 hollow microspheres (MSs) are discussed. It demonstrates a lower overpotential of 240 mV at 10 mA cm-2 and a small Tafel slope of 70 mV dec−1. Also, the MSs exhibit high mass activity of 600 A g−1 and show high stability for 24 hours Chronopotentiometry tests at constant current densities of 10 and 20 mA cm−2 in 0.5 M H2SO4.
Finally, nanostructured CdSe/Cu3P/CdSe heterostructures (in the form of nanocoral and sandwiches), obtained through colloidal synthesis, were used as efficient electrocatalysts for CO2 reduction. The nanocoral and Sandwich structured catalyst demonstrated higher CO2-to- HCOO– conversion giving a FEHCOO– of about 60% and 40% at –1.4 V vs RHE, respectively in 0.5 M KCl.
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Neri, G. "The electro- and photochemical reduction of CO2 mediated by molecular catalysts". Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3007220/.
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In this work, molecular complexes of transition metals have been synthesised and studied for their CO2 reduction ability, either in an electrochemical or photochemical system, with a focus on complexes of nickel with derivatives of the macrocycle cyclam (cyc, cyc = 1,4,8,11-tetraazacyclotetradecane) which are well-known for being extremely active CO2 reduction electrocatalysts in water. The cyc framework has been modified with functional groups suitable for binding to semiconductor oxides to obtain the new complexes Ni(cycC) and Ni(cycP) (cycC = 1,4,8,11-tetraazacyclotetradecane-6-carboxylic acid, cycP = {[(1,4,8,11-tetraazacyclotetradecan-1-yl)methyl]phosphonic acid}), and their electrochemical activity towards CO2 reduction in water has been evaluated. Modification of the ligand framework in the 6 position with a carboxylic acid does not change the CO2 reduction activity of the complex Ni(cycC) at pH 5, through the use of electrochemical and spectroscopic techniques it was found that there is a large increase in the CO2 reduction activity at pH 2, proposed to be due to the protonated carboxylic acid acting as an internal proton source. When Ni(cycC) was immobilised on TiO2 electrodes it was possible to measure the rate of photoinduced electron transfer by using μs-s transient absorption spectroscopy (TAS) under argon in the presence of a hole scavenger, however the carboxylic acid proved unstable under CO2. Ni(cycP) was synthesised to provide a stronger binding group to the surface. It was found that functionalisation on the 1 position affected the CO2 reduction activity in a negative way, however the complex was able to bind strongly to both TiO2 and ZrO2. ZrO2 nanoparticles modified with Ni(cycP) and a ruthenium dye were able to reduce CO2 to CO in water at pH = 4, with higher rates and turnover numbers compared to the components in solution, when illuminated with visible light. The improvement in activity for the heterogeneous photocatalyst was attributed to a faster electron transfer from the immobilised dye to the immobilised catalyst, calculated through detailed steady-state and transient spectroscopies, which prevented charge recombination. In collaboration with the University of Cambridge, Ni(cycP) has been immobilised on ZnSe quantum dots (QDs) and it has been proven to be an effective photocatalyst for CO2 reduction to CO in water. We have carried out a detailed ultrafast TAS study on suspensions of the modified QDs, and it has been found that in the presence of a hole scavenger, upon illumination the electrons are excited from the VB to the conduction band (CB), however they rapidly decay to trap states close to the CB to generate a long lived signal. When Ni(cycP) is present, faster decay of the trapped electron signal is observed, which is assigned to fast electronic transfer from the QDs to Ni(cycP). The knowledge of the mechanisms for CO2 reduction will allow rational design of better catalysts for CO2 reduction. In collaboration with the Rutherford Appleton Laboratories, we have designed an in situ spectroelectrochemical Sum Frequency Generation (SEC-SFG) technique using the ULTRA laser at the Central Laser facility. We have demonstrated the technique by analysing the redox behaviour of a well-known CO2 reduction catalyst, [Mn(bpy)(CO)3Br]. We were able to observe the redox species at the electrode surface as a Cyclic Voltammogram was carried out, and to propose the orientation of the species at the surface. Furthermore, the same technique has been applied to the study of the absorption mechanism of Ni(cycC) on the mercury surface, the first step in the catalytic cycle.
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Parker, Simon. "Anchored photo-electro-catalysts for CO2 reduction based on transition metal complexes". Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/13396/.
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Cruz, neto Daniel H. "Photophysical investigations of reversible charge accumulation in photocatalytic molecular systems". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP098.
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Inspirée de la nature, la conversion de l’énergie solaire par photosynthèse artificielle est l’une des solutions les plus prometteuses à la crise énergétique mondiale actuelle. Cependent, déployer des systèmes artificiels fonctionnels nécessite une compréhension approfondie des processus intégrés dans le fonctionnement des systèmes naturels car ils fournissent les directions pour réaliser des dispositifs de photosynthèse artificielle. Ces processus incluent l’absorption de la lumière, la séparation des charges, plusieurs étapes de transfert de charges menant à leur accumulation et, enfin, la catalyse. Dans ce travail, nous étudions toutes ces étapes élémentaires en utilisant des approches spectroscopiques résolues en temps, dans le but d’explorer la photophysique de différents systèmes moléculaires biomimétiques dédiés à la photoréduction du dioxyde de carbone (CO₂) pour produire des carburants solaires. Nous commençons par le développement d’un nouveau dispositif expérimental pompe-pompe-sonde, capable de déclencher et de détecter l’accumulation progressive de charges grâce à une sonde Raman résonante. Un système modèle contenant le dication méthylviologène (MV²⁺) comme double accepteur d’électrons, le complexe prototypique [Ru(bpy)₃]²⁺ comme photosensibilisateur, et l’ascorbate comme donneur réversible d’électron est utilisé pour une preuve de concept de la technique. En effet, avec la première pompe, MV•⁺ est formé et détecté grâce à son mode vibrationnel caractéristique à 1356 cm⁻¹. Lorsque la concentration transitoire de , MV•⁺ atteint son maximum, nous déclenchons la deuxième pompe laser pour montrer la possibilité de suivre la formation réversible du MV⁰ à travers d’un mode vibrationnel unique à 992 cm⁻¹. Nous passons ensuite à l’étude de systèmes catalytiquement actifs composés de dérivés de porphyrine de fer en tant que catalyseurs pour la réaction de réduction du CO₂. Ces porphyrines sont intégrées dans des systèmes biomimétiques multicomposants contenant du [Ru(bpy)₃]²⁺ et de l’ascorbate comme photosensibilisateur et donneur réversible d’électron, respectivement. Pour le dérivé fonctionnalisé avec des groupements urées (FeUr), un catalyseur contenant un réseau de liaisons hydrogène logé dans sa seconde sphère de coordination, nous fournissons une description mécanistique complète de tous les processus photoinduits conduisant à l’accumulation de charges et son activation vers le CO₂. En atmosphère inerte, en partant de l’état d’oxydation Feˡˡˡ, nous rapportons l’accumulation de deux électrons vers la formation de l’état Feˡ à la suite de la stratégie pompe-pompe-sonde. Sous conditions catalytiques en présence de CO₂, notre approche fournit des preuves convaincantes que l’état d’oxydation Feˡ, produit de deux étapes consécutives de transfert d’électron, est déjà catalytiquement actif, comme en témoigne l’accumulation de l’intermédiaire stable Feˡˡ‒CO caractéristique du cycle de réduction du CO₂. D’une façon générale, nous montrons également que Feˡ est catalytiquement actif indépendamment de la stratégie de fonctionnalisation du macrocycle de la porphyrine, remettant en cause l’interprétation classique de la catalyse de réduction du CO₂ promue par les porphyrines de fer. Enfin, nous nous éloignons du complexe prototypique Ru(bpy)₃]²⁺ pour étudier la photophysique de différents photosensibilisateurs basés sur des éléments abondants sur terre, y compris des complexes à base de cuivre(I), un dérivé porphyrine de zinc (ZnF₂₀), et un colorant carbocationique entièrement organique (TATA⁺). Notamment, nous montrons que le TATA⁺ est capable de photosensibiliser l’accumulation de charges sur le système actif à base de FeUr, activant ainsi la réaction de réduction du CO₂. La caractérisation de nouveaux photosensibilisateurs basés sur des éléments abondants sur terre est fondamentale pour le développement de photosystèmes artificiels avec des applications concrètes dans le monde réelInspired by nature’s masterpiece of evolution, the conversion of solar energy through artificial photosynthesis is one of the most promising solutions to the ongoing global energy crisis. Deploying functional artificial mimics of the photosynthetic apparatus, however, requires a deep understanding of the processes embedded in the functioning of naturally photosensitizing organisms as they provide the roadmap to realize artificial photosynthetic devices. These processes include light harvesting, charge separation, multiple charge transfer steps leading to effective charge accumulation and, finally, efficient catalysis. In this work, we investigate all of these elementary steps by employing state-of-the-art time-resolved spectroscopic approaches with the goal of exploring the photophysics of different biomimetic molecular systems devoted to the photoreduction of carbon dioxide (CO₂) to produce energy-rich solar fuels. We start with the development of a novel pump-pump-probe experimental setup that is capable of triggering and detecting the stepwise accumulation of charge through the powerful lens of a resonance-enhanced Raman scattering probe. A model system containing the methyl viologen dication (MV²⁺) as a dual electron acceptor, the prototypical [Ru(bpy)₃]²⁺ complex as a photosensitizer, and ascorbate as a reversible electron donor is used for a proof-of-concept of the technique. Indeed, with the first pump, MV•⁺ is formed and detected through its fingerprint vibrational mode at 1356 cm⁻¹. When the transient concentration of MV•⁺ peaks, we fire the second laser pump and show the possibility of tracking the reversible formation of the two-electron accumulated MV⁰ species through a unique vibrational mode at 992 cm⁻¹. We then move on to investigating catalytically active systems featuring iron porphyrin derivatives as CO₂ reduction catalysts. These porphyrins are integrated into multicomponent biomimetic systems that similarly contain [Ru(bpy)₃]²⁺ and ascorbate as photosensitizer and reversible electron donor, respectively. For the urea-functionalized derivative (FeUr), a catalyst with a hydrogen-bonding network lodged in its second coordination sphere, we provide a full mechanistic depiction of all photoinduced processes leading to charge accumulation and its activation towards CO₂. In inert atmosphere, starting from Feˡˡˡ, we report the stepwise formation of the formal Feˡ species as a result of the double pump excitation strategy. Remarkably, under catalytic conditions in the presence of CO₂, our spectroscopy-based approach provides compelling evidence that the Feˡ oxidation state of FeUr, product of two consecutive electron transfer steps, is already catalytically active, evidenced by the accumulation of the stable Feˡˡ‒CO intermediate of the CO₂ reduction cycle. Going beyond FeUr, we show that Feˡ is catalytically active irrespective of the design strategy used in the functionalization of the porphyrin macrocycle, challenging the classical picture of CO₂ reduction catalysis promoted by iron porphyrins. Finally, we move away from the prototypical [Ru(bpy)₃]²⁺ complex and dive into the photophysics of different photosensitizers based on earth-abundant elements, including copper(I)-based complexes, a perfluorinated zinc porphyrin derivative (ZnF₂₀), and a fully organic triazatriangulenium carbocationic dye (TATA⁺). Importantly, we show that the TATA⁺ dye is capable of photosensitizing charge accumulation on the active FeUr-based system, activating it towards the reduction of CO₂. The characterization of new photosensitizing units based on abundant elements is fundamental for the development of artificial photosystems with real-world applications
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Chen, Junbo. "Effect of Defects and Photoexcited Electrons on CO2 Reduction using Supported Single Atom Catalysts". Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-theses/1266.
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Excessive CO2 emissions can negatively impact society and our planet. Reduction of CO2 is one potential avenue for its abatement. One of the most significant challenges to reducing CO2 is its extremely stable linear form. Experimentally, Cu/TiO2 has shown promise for CO2 photocatalytic reduction. Dispersed atomic catalysts can achieve high catalytic efficiency on a per atom basis. Active sites also typically having lower coordination number, and therefore may be more reactive. Using density functional theory and experimental techniques, we have investigated the role of surface oxygen vacancies (Ov) and photoexcited electrons on supported single atom catalysts and CO2 reduction. Cu atoms with Ov have shown to aid in the process of bent, anionic CO2 formation. In the first step involving CO2 dissociation (CO2* --> CO* + O*), a single Cu atom in Ov lowered the activation barrier to 0.10 - 0.19 eV, which could enable fast reduction of CO2 even at room temperature, in agreement with experimental findings. A photoexcited electron model was shown to readily promote Cu binding to the surface vacancy, and CO2 adsorption and direct dissociation. Finally, we briefly compare our results to calculations of supported single Pt atoms to determine how metals besides Cu may behave as photocatalysts for CO2 reduction, and we found a single Pt with Ov can promote CO2 dissociation. Our results show that tailoring TiO2 surfaces with defects in conjunction with atomic catalysts may lead to useful catalysts in the photoreduction of CO2.
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Wolff, Niklas von. "Reaction mechanisms of CO₂ activation and catalytic reduction". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS580.
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L’utilisation du dioxyde de carbone (CO₂) comme source de composés C1 pour la chimie fine est intéressante d’un point de vue économique et pour des raisons écologiques. Issu de l’oxydation de la matière carbonée, le CO₂ est un gaz non-toxique, abondant et peu coûteux. Sa transformation en produits chimiques présentant de hautes valeurs ajoutées est actuellement entravée par sa stabilité thermodynamique. Afin de développer de nouveaux processus et catalyseurs pour la réduction catalytique du CO₂, une compréhension détaillée des mécanismes réactionnels de l’activation et de la réduction de ce gaz est nécessaire. En utilisant comme catalyseurs des paires de Lewis frustrée (FLPs) contenant une base azotée liée à un ion silicénium, les influences respectives de l’adduit CO₂-FLP et du réducteur ont été déterminées expérimentalement et par calcul DFT dans le cadre de l’hydroboration du CO₂ en équivalent de méthanol. Une nouvelle réaction visant à la création de liaisons carbone–carbone par le transfert du fragment pyridyle de molécules de pyridylsilanes (C₅H₄N–SiMe₃) sur le CO₂ était également étudiée. Le mécanisme réactionnel de cette transformation a été établi sur la base de calculs théoriques. Nous avons montré le double rôle du CO₂ qui est à la fois un réactif et un catalyseur de la réaction de transfert du groupe pyridyle. La compréhension fine de cette réaction nous a permis de l’étendre à la formation de sulfones et sulfonamides qui sont des groupements chimiques essentiels dans le domaine pharmaceutique. En utilisant le SO₂ à la fois comme catalyseur et réactif, des silanes aromatiques et hétéro-aromatiques ont été transformés en sulfones correspondants en une seule étape. Finalement, nous avons trouvé un couplage croisé original, de type Hiyama, entre espèces aromatiques électrophiles et des espèces C(sp2)–Si nucléophiles en présence de SO₂The use of CO₂ as a C1 chemical feedstock for the fine chemical industry is interesting both economically and ecologically, as CO₂ is non-toxic, abundant and cheap. Nevertheless, transformations of CO₂ into value-added products is hampered by its high thermodynamic stability and its inertness toward reduction. In order to design new catalysts able to overcome this kinetic challenge, a profound understanding of the reaction mechanisms at play in CO₂ reduction is needed. Using novel N/Si+ frustrated Lewis pairs (FLPs), the influence of CO₂ adducts and different hydroborane reducing agents on the reaction mechanism in the catalytic hydroboration of CO₂ were investigated, both by DFT calculations and experiments. In a second step, the reaction mechanism of a novel reaction for the creation of C–C bonds from CO₂ and pyridylsilanes (C₅H₄N–SiMe₃) was analyzed by DFT calculations. It was shown that CO₂ plays a double role in this transformation, acting both as a catalyst and a C1-building block. The fine understanding of this transformation then led to the development of a novel approach for the synthesis of sulfones and sulfonamides. Starting from SO₂ and aromatic silanes/amine silanes, these products were obtained in a single step under metal-free conditions. Noteworthy, sulfones and sulfonamides are common motifs in organic chemistry and found in a variety of highly important drugs. Finally, this concept was extended to aromatic halides as coupling partners, and it was thus shown for the first time that a sulfonylative Hiyama reaction is a possible approach to the synthesis of sulfones
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Spall, Steven J. P. "Rhenium and manganese α-diimine tricarbonyls as CO2 reduction catalysts : insights from novel ligand design". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19369/.
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Concerns over climate change and energy security combined with the commercial application of carbon capture technologies has led to increased interest in the use of CO2 reduction catalysts as a means to convert this captured waste into fuel. In order to accomplish this photocatalytic or electrocatalytic systems must be employed of which the Lehn type catalyst based on the original [ReCl(CO)3(bpy)] complex is highly suitable due its selective CO formation and high efficiency. The purpose of this project was to develop new understanding of Lehn type CO2 reduction catalysis and, in particular, to develop new families of catalysts integrating manganese in place of rhenium. Much of the research has focussed on the concept of decoupling – either decoupling electron withdrawing groups from the α-diimine or decoupling the electronic effects from the steric effects. A variety of rhenium and manganese complexes have been synthesised and studied using a variety electrochemical and spectroscopic methods. Initial research focussed upon developing our understanding of the photodecomposition of the manganese based Lehn type catalysts and it was determined that the complexes decay via CO elimination giving a large variety of decomposition products. This research led to the investigation of the electrocatalytic and photocatalytic properties of three rhenium bis(mestiylimino)-acenaphthene complexes which exhibited electrocatalytic activity but not photocatalytic activity. The major family of ligands studied were asymmetric imino pyridine ligands which due to the break of symmetry between the phenyl moiety and the diimine allow for sterically demanding groups to be incorporated into the complexes without changing the electronic properties of the complex. These complexes are ideal for ‘lab mouse’ investigations of systems that show sensitivity to both steric and electronic factors. It was observed that while the rhenium imino pyridine complexes behaved in a manner similar to bipyridine complexes the manganese variants exhibited behaviour more akin to what has been observed in manganese diazabutadiene catalysts. Attempts to provide quantitative analysis of catalyst performance led to the employment of many different techniques ranging from gas chromatography to line shape analysis of voltammograms, however, no satisfactory method of performing quantitative analysis could be found. The overall conclusion is that the manganese based Lehn type catalysts can be used effectively as homogeneous electrocatalysts but the photosensitivity prohibits practical use in photocatalytic systems. The asymmetric imino pyridine ligands have shown great potential for systematic investigation of CO2 reduction catalysts and offer enormous scope for further development, however it is necessary for the community to adopt and publicise standards for benchmarking new catalysts as the methods employed today are not ideal.
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Alghamdi, Ahlam. "Exploring New Applications of Group 7 Complexes for Catalytic and CO2 Reduction Using Photons or Electrochemistry". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35234.
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This thesis focuses on the synthesis, characterization and reactivity of group VII transition metal complexes. It begins with exploring a new pincer geometry of Re(I) compounds and then examining both Re(I) and Mn(I) compound as homogenous catalysts for photocatalytic and electrocatalytic reduction of CO2. In the first chapter, I focus on some recently reported approaches to photocatalytic and electrocatalytic reduction of CO2 using homogenous catalysts of transition metal.
The second chapter presents efforts to capture Re(I) in a neutral N,N,N pincer scaffold and the resulting enhanced absorption of visible light. Most of these results have appeared in a publication. In this thesis, I only present my work on rhenium compounds that are supported by the bis(imino)pyridine ligand and an examination of the differences in properties between the bidentate and tridentate ligand geometries. Later I examine both tridentate and bidentate complexes for the photocatalytic and electrocatalytic reduction of CO2 to CO.
The failure of tridentate Re1 bis(imino)pyridine compounds to reduce CO2 to CO prompted a change in direction to rhenium compounds that are supported with diimine ligands. Thus, I choose 4,5-diazafluoren-9-one as supporting ligand for rhenium and manganese. This chapter explained the reasons behind choosing these particular ligand and metal combinations. ReI and Mn1 compounds of 4,5-diazafluoren-9-one have shown activity for the photocatalytic and electrocatalytic reduction of CO2 to CO.
In the fourth chapter, as rhenium and manganese compounds of 4,5-diazafluoren-9-one have shown the great ability of CO2 reduction to CO, the focus here was to modify the ligand by attaching a photosensitizer to the ligand in order to prepare supramolecular complexes that may increase the efficiency and yield of reduction products. In this chapter, I examined two types of the photosensitizer; tris(bipyridine)ruthenium(II)chloride and osmium dichloro bis(4,4'-dimethyl-2,2'-bipyridine).
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Wu, Huali. "Molecular doping of copper-based catalysts for the electrocatalytic conversion of CO2 to multi-carbon products". Electronic Thesis or Diss., Montpellier, Ecole nationale supérieure de chimie, 2022. http://www.theses.fr/2022ENCM0016.
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La réaction de réduction du CO2 (CO2RR) est très prometteuse pour la conversion du gaz à effet de serre: le dioxyde de carbone en carburant chimique. L'absence de matériaux catalytiques démontrant des performances élevées et une sélectivité élevée entrave actuellement la démonstration pratique. CO2RR est également limité en raison de la faible solubilité du CO2 dans la solution d'électrolyte. Par conséquent, les réactions électrocatalytiques en phase gazeuse utilisant des électrodes à diffusion gazeuse seraient préférées. Les matériaux 2D sont récemment apparus comme une nouvelle classe de matériaux électrocatalytiques grâce à leurs structures riches et leurs propriétés électroniques. La synthèse de nouveaux catalyseurs 2D et leur mise en oeuvre dans des systèmes photocatalytiques constitueraient une étape majeure dans la mise au point de dispositifs de stockage de l'énergie solaire sous forme de combustibles chimiques. Le projet de recherche portera sur la conception de nouveaux matériaux de faible dimension comme photo- et électrocatalyseurs pour la réduction électrochimique du CO2 en carburants chimiques. Ce projet de thèse vise à comprendre le comportement des matériaux de faible dimension, tels que les matériaux de faible dimension, vis-à-vis de la réduction de CO2 en explorant la relation structure-propriété des matériaux de faible dimensionCO2 reduction reaction (CO2RR) holds great promise for the conversion of green-house gas: carbon dioxide into chemical fuels. The absence of catalytic materials demonstrating high performance and high selectivity currently hampers practical demonstration. CO2RR is also limited because of the low solubility of CO2 in the electrolyte solution and therefore electrocatalytic reactions in gas phase using gas diffusion electrodes would be preferred. 2D materials have recently emerged as a novel class of electrocatalytic materials thanks to their rich structures and electronic properties. The synthesis of novel 2D catalysts and their implementation into photocatalytic systems would be a major step towards the developments of devices for storing solar energy in the form of chemical fuels. The research project will focus on the design of novel low-dimensional materials as photo- and electrocatalysts for the electrochemical reduction of CO2 into chemical fuels. This PhD project aims to understand the behavior of low-dimensional materials such as low dimensional materials toward the reduction of CO2 by exploring the structure-property relationship for low-dimensional materials
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Rasheed, Senan. "Photocatalytic Carbon Dioxide Reduction with Zinc(II) Dipyrrin Photosensitizers and Iron Catalyst". Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/etd/3730.
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Much of the energy used in the United States and around the globe is obtained from petroleum, natural gas, and coal. Photocatalytic CO2 reduction can be used to transform CO2 to useful fuels and making fossil fuels more renewable. Input of energy is required, and the sun can provide the required energy for this transformation. Photosensitizer, catalyst, and electron donor are required for photocatalytic CO2 reduction.
Due to lack of earth-abundant sensitizers, zinc dipyrrin complexes were synthesized by previous group members and have been used as photosensitizers in this research. The ground and excited state electrochemical properties of two zinc dipyrrin complexes were determined in polar and nonpolar solvents and the measured potentials were used to match the zinc sensitizers with an energetically appropriate iron porphyrin catalyst and a benzylthiol sacrificial electron donor. Lastly, pure CO2 gas was used as the source of carbon for the reduction of CO2 by photocatalysis with the zinc photosensitizers, iron catalyst and sacrificial electron donor. The products formed in headspace were analyzed by GC
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Iyemperumal, Satish Kumar. "Conversion of Carbon Dioxide to Fuels using Dispersed Atomic-Size Catalysts". Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-dissertations/505.
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Record high CO2 emissions in the atmosphere and the need to find alternative energy sources to fossil fuels are major global challenges. Conversion of CO2 into useful fuels like methanol and methane can in principle tackle both these environment and energy concerns. One of the routes to convert CO2 into useful fuels is by using supported metal catalyst. Specifically, metal atoms or clusters (few atoms large in size) supported on oxide materials are promising catalysts. Experiments have successfully converted CO2 to products like methanol, using TiO2 supported Cu atoms or clusters. How this catalyst works and how CO2 conversion could be improved is an area of much research. We used a quantum mechanical tool called density functional theory (DFT) to obtain atomic and electronic level insights in the CO2 reduction processes on TiO2 supported metal atoms and clusters.
We modeled small Cu clusters on TiO2 surface, which are experimentally synthesizable. Our results show that the interfacial sites in TiO2 supported Cu are able to activate CO2 into a bent configuration that can be further reduced. The Cu dimer was found to be the most reactive for CO2 activation but were unstable catalysts. Following Cu, we also identified other potential metal atoms that can activate CO2. Compared to expensive and rare elements like Pt, Au, and Ir, we found several early and mid transition metals to be potentially active catalysts for CO2 reduction. Because the supported metal atom or cluster is a reactive catalyst, under reaction conditions they tend to undergo aggregation and/or oxidation to form larger less active catalysts. We chose Co, Ni, and Cu group elements to study their catalyst stability under oxidizing reaction conditions. Based on the thermodynamics of Cu oxidation and kinetics of O2 dissociation, we found that TiO2 supported Cu atom or a larger Cu tetramer cluster were the likely species observed in experiments. Our work provides valuable atomic-level insights into improving the CO2 reduction activities and predicts potential catalysts for CO2 reduction to valuable fuels.
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John, Lukas [Verfasser], e Stephan [Akademischer Betreuer] Schulz. "Computational insights and catalyst syntheses for the electrochemical CO2 reduction / Lukas John ; Betreuer: Stephan Schulz". Duisburg, 2019. http://d-nb.info/1176409549/34.
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Shang, Hongyu SHANG. "Investigating Electronic Structure Effects in Transition Metal Oxides Used as Catalysts for Water Oxidation and CO2 Reduction". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1525451894252362.
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Gao, Guoping. "Computational design of catalysts for clean energy conversion and storage". Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/109443/1/Guoping_Gao_Thesis.pdf.
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This project focuses on the computational design of novel catalyst for artificial synthesis: converting sunlight into fuels. With the atomic-scale insight of catalysts obtained by theoretical calculations, many efficient and optimum catalysts for these processes have been designed and engineered. The outcomes of this thesis are expected to provide theoretical solutions for current global energy and environmental challenges.
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Borges, Ordoño Marta. "Insights into the co-catalyst effects in light driven reactions for water splitting and carbon dioxide reduction". Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/664713.
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La transformació dels fotons presents en la radiació solar a energia química es una estratègia possible per explotar la nostra major font d’energia, el sol. La llum solar pot promoure les transicions electròniques en materials semiconductors que solen ser utilitzats en les reaccions fotocatalítiques. No obstant, els semiconductors tenen banda ampla i no són actius en tota la regió del espectre solar; per això, l’ús de llum ultra violeta es requerit. A demés, els semiconductors basats en òxids mixtes solen presentar poca activitat catalítica. Per aquest motiu i per tal d’incrementar les seves eficiències, els fotocatalitzadors és modifiquen amb materials co-catalítics (promotors). Aquest projecte està basat en la comprensió de la funció dels co-catalitzadors en la producció d’hidrogen per la reacció de dissociació del aigua i per produir combustibles químics en el procés de fotoreducció de CO2. Tècniques espectroscòpiques com és l’absorció (XAS) i emissió (XES) de rajos X es van utilitzar per obtenir major coneixement en les estructures electròniques dels materials fotocatalítics, i l’espectroscòpia per reflectància difusa (DRIFTS) és va utilitzar per aprendre sobre els mecanismes de reacció. Finalment, mètodes electroquímics foren utilitzats per obtenir major coneixement sobre els processos redox durant les reaccions fotocatalítiques.La transformación de fotones contenidos en la radiación solar a energía química es una estrategia posible para explotar nuestra mayor fuente de energía, el sol. La luz solar puede promover transiciones electrónicas en materiales semiconductores que suelen ser utilizados en las reacciones fotocatalíticas. No obstante, los semiconductores tienen banda ancha y no son activos en toda la región del espectro solar; por eso, el uso de luz ultravioleta es requerido. Además, los semiconductores basados en óxidos mixtos suelen presentar poca actividad catalítica. Por este motivo y por tal de incrementar sus eficiencias, los fotocatalizadores se modifican con materiales co-catalíticos (promotores). Este proyecto se basa en la comprensión de la función de los co-catalizadores en la producción de hidrógeno en la reacción de disociación del agua y para producir combustibles químicos en el proceso de fotoreducción de CO2. Técnicas espectroscópicas como es la absorción (XAS) o la emisión (XES) de rayos X se utilizaron para obtener mayor conocimiento en las estructures electrónicas de los materiales fotocataltíticos, y la espectroscopia por reflectancia difusa (DRIFTS) se usó para aprender sobre los mecanismos de reacción. Finalmente, métodos electroquímicos fueron usados para obtener mayor conocimiento sobre los procesos redox durante las reacciones fotocatalíticas.
Transformation of photons contained in solar radiation into chemical energy is a possible strategy to utilize our largest energy source, the sun. Solar light can promote electronic transitions in semiconductor materials which are commonly employed in photocatalytic reactions. Nevertheless, wide-bandgap semiconductors are not active in the full solar spectral region; therefore, utilization of ultraviolet light is required. In addition, bare mixed oxide semiconductors have low catalytic activities. In order to boost their efficiencies, photocatalysts are modified with co-catalyst materials (promoters). This project is targeted to understand the role of co-catalysts in the production of hydrogen from water splitting reaction and to generate chemical fuels from CO2 photoreduction process. Spectroscopic techniques such as e.g. X-ray adsorption (XAS) and emission (XES) were used to gain deeper understanding on the electronic structures of photocatalytic materials, and Diffuse Reflectance Infrared Fourier Transformed spectroscopy (DRIFTS) to learn about the reaction mechanisms. Furthermore, electrochemical methods were used to get insights about the redox processes occurring during both photocatalytic reactions.
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Zhu, Xing. "Development of alkali hexatitanate photocatalysts and co-catalysts for photocatalytic reduction of carbon dioxide by water". Doctoral thesis, Kyoto University, 2020. http://hdl.handle.net/2433/253386.
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京都大学0048
新制・課程博士
博士(人間・環境学)
甲第22550号
人博第953号
新制||人||226(附属図書館)
2019||人博||953(吉田南総合図書館)
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 吉田 寿雄, 教授 内本 喜晴, 教授 田部 勢津久
学位規則第4条第1項該当
Doctor of Human and Environmental Studies
Kyoto University
DFAM
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Ilic, Stefan. "Utilizing NAD+/NADH Analogs for the Solar Fuel Forming Reductions". Bowling Green State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1499262103862098.
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Moraes, Ricardo Sgarbi de. "Investigação da eletrocatálise de interconversão do par dióxido de carbono/íons formato para aplicação em ciclos de estocagem de hidrogênio". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-19042016-150431/.
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A crescente emissão do CO2 para a atmosfera, causada pela matriz energética dependente dos combustíveis fósseis tem gerado a necessidade de sistemas que o utilizem como matéria-prima para a produção ou armazenamento de energia. Em vista disso, este trabalho teve como objetivo o estudo do ciclo de estocagem de hidrogênio baseado em etapas eletrocatalíticas da eletro-redução e eletro-oxidação do par CO2/HCOO-. Para o processo de eletro-redução, foram utilizados eletrocatalisadores suportados em pó de carbono formados à base de estanho (Sn/C) e de estanho modificado com cobalto (Co-Sn/C), cobre (Cu-Sn/C) e paládio (Sn-Pd/C). Os materiais foram sintetizados pelo método de impregnação seguido por tratamento térmico e caracterizados fisicamente por Difratometria de Raios X (DRX) e Espectroscopia por energia Dispersiva de Raios X (EDX). Os testes eletroquímicos foram realizados via cronoamperometria (eletrólise) e a quantificação dos íons formato por Cromatografia Líquida de Alta Eficiência (CLAE) e voltametria cíclica (VC). Os resultados obtidos mostraram que os materiais nanoestruturados sintetizados apresentaram estruturas cristalinas, sendo que o estanho apresentou-se na forma de SnO2, mas sofrendo eletro-redução em condições in situ para SnO ou SnOH. Os resultados eletroquímicos mostraram que o Sn/C eletrocatalisa a redução do CO2 para HCOO-, sendo que a quantificação por VC utilizando eletrodos de paládio e platina indicaram correntes de pico crescentes até o potencial de eletrólise de -1,6 V vs. Ag/AgCl/Cl-. Ademais, experimentos de eletrólise evidenciaram o aumento linear da concentração de HCOO- após 6 horas de polarização, indicando alta estabilidade do eletrocatalisador de Sn/C. A atividade eletrocatalítica dos eletrocatalisadores à base de estanho frente a redução de CO2 para HCOO- foi atribuída a dois aspectos: (i) o estanho favorece a adsorção ou interação do CO2 através dos átomos de oxigênio, possibilitando a transferência de prótons e elétrons sem a quebra da ligação C-O e/ou; (ii) a presença de espécies SnOH na superfície, mesmo em baixos potenciais, permite a interação com o CO2 e leva à formação de intermediários adsorvidos reativos, que sofrem a adição de prótons e elétrons para a formação de HCOO-. A eficiência máxima de corrente faradaica para a formação de HCOO- foi de aproximadamente 7 % tendo a reação de desprendimento de hidrogênio (HER) como rota paralela. A investigação da influência da natureza do eletrocatalisador mostrou inatividade do material de Co-Sn/C, mas com aumento da atividade de Cu-Sn/C para a eletro-redução de CO2, quando comparado com Sn/C puro.With the increase CO2 emissions into atmosphere caused mainly by the energy dependence on fossil fuels, systems for generation or storage of clean energy has been studied to couple CO2 as feedstock. This work proposed a hydrogen storage cycle based on electrocatalytic steps of pair CO2/HCOO-, such electroreduction and electrooxidation. For electroreduction process were used carbon-supported tin-based electrocatalysts (Sn/C) and tin modified with cobalt (Co-Sn/C), copper (Cu-Sn/C) and palladium (Sn-Pd/C). The materials were synthesized by impregnation method followed of thermal treatment, and X Ray Diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDS) techniques were used for physical characterization. Electrochemical tests were performed via chronoamperometry (electrolysis) and the quantification of formate ions by High Performance Liquid Chromatography (HPLC) and cyclic voltammetry (CV). Results of synthesized nanostructured materials showed crystalline structures with tin as SnO2 species, but tin oxide suffering electroreduction to SnO or SnOH in situ conditions. Electrochemical results presented that the Sn/C catalyzes the CO2 reduction to HCOO-, with an increase peak current until electrolysis potential of -1.6 V vs. Ag/AgCl/Cl- quantified by CV on palladium and platinum electrodes. Moreover, electrolysis measurements demonstrated the linear increase of HCOO- concentration after polarization for 6 hours, which indicates the high stability of Sn/C electrocatalyst. The electrocatalytic activity of tin-based electrocatalysts for CO2 reduction into HCOO- was attributed to two aspects: (i) tin favors the adsorption or interaction of CO2 through oxygen atoms, which enables the proton and electron transfer without breaking C-O bond and/or; (ii) the presence on surface of SnOH species allows the interaction with CO2 even at low potential, and leads to the formation of reactive intermediates adsorbed that undergo addition of protons and electrons to form HCOO-. Maximum Faradaic efficiency for HCOO- formation was near 7% with Hydrogen Evolution Reaction (HER) as parallel route. Investigation of the influence of the electrocatalyst nature showed inactivity of CO-Sn/C material, but the activity of CO2 electroreduction increased on Cu-Sn/C material as compared to Sn/C pure.
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Kilaparthi, Sravan Kumar. "Carbon-based electrocatalysts for CO2 reduction, PET hydrolysate, and water splitting towards value-added products". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILN051.
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Cette étude aborde les principaux défis mondiaux tels que les émissions de CO2, la crise énergétique et la mauvaise gestion des déchets plastiques PET, qui non seulement polluent l'environnement mais contribuent également aux émissions de CO2 lors de l'incinération. L'approche innovante présentée dans cette thèse offre une double solution, abordant simultanément les déchets PET et les émissions de CO2.Deux systèmes remarquables ont été explorés dans cette thèse. Le premier utilisait du carbonate d'oxyde de bismuth (BOC) fonctionnalisé de l'oxyde de graphène réduit (rGO) pour l'électroréduction cathodique du CO2 (CO2RR), tandis que CuCoO sur rGO était utilisé pour l'oxydation anodique de l'hydrolysat de PET. De manière impressionnante, le catalyseur anodique CuCoO@rGO a affiché une électroactivité exceptionnelle, atteignant un rendement faradique (FE) exceptionnel de 85,7 % à 1,5 V par rapport à RHE. Simultanément, le catalyseur cathodique BOC@rGO a démontré un FE impressionnant de 97,4 % à -0,8 V par rapport au RHE, facilitant la production de formiate à partir de CO2RR. Lorsqu'elle est intégrée dans une configuration d'électrolyseur, cette approche a abouti à une production d'acide formique à une faible tension de cellule de 1,9 V et à un FE formiate remarquable de 151,8 % à 10 mA cm-2.Un autre système utilisait une électrode 3D en feutre de charbon actif (aCF) comme substrat et du bismuth a été déposé électrochimiquement sur le CF (Bi@aCF) qui agit comme la cathode CO2RR et un feutre de carbone déposé au phosphate de nickel-cobalt (NiCoPOx@CF) pour l'anode. Procédé d'oxydation de l'hydrolysat de PET. Cette configuration a atteint un FE élevé de 94 % pendant CO2RR à -0,8 V par rapport au RHE, produisant du formiate, et un FE de 95 % pour l'oxydation anodique de l'hydrolysat de PET pour former un formiate à un faible potentiel de 1,5 V par rapport au RHE. Remarquablement, l'électrolyseur à deux électrodes a atteint un FE extraordinaire de 157 % pour produire du formiate à une tension de cellule de 1,8 V. Cette percée représente une nouvelle voie pour valoriser les déchets de PET, réduire les émissions de CO2 et promouvoir la durabilité environnementale.De plus, nos expériences ont également porté sur l'électrolyse de l'eau, où une nouvelle stratégie impliquant du Ru intégré dans une matrice de nitrure de carbone a été proposée. Cette approche, utilisant une structure organique covalente 2D CIN-1 avec Ru + 2 coordonné, a abouti à des nanoparticules d'oxyde de Ru avec des sites Ru de faible valence disposés en nanofils entre des couches de nitrure de carbone graphitique après pyrolyse. Ce matériau présentait des surpotentiels significativement inférieurs pour la réaction de dégagement d'hydrogène (HER) et la réaction de dégagement d'oxygène (OER) par rapport aux catalyseurs de référence au Pt et au RuO2, démontrant une stabilité catalytique remarquable. Cette découverte est extrêmement prometteuse pour faire progresser le domaine du fractionnement de l'eau et contribuer au développement de solutions énergétiques durablesThis study tackles the major global challenges such as CO2 emissions, energy crisis and PET plastic waste mismanagement, which not only pollutes the environment but also contributes to CO2 emissions during incineration. The innovative approach presented in this thesis offers a dual solution, addressing both PET waste and CO2 emissions simultaneously.Two remarkable systems have been explored in this thesis. The first utilized Bismuth oxide carbonate (BOC) functionalized reduced graphene oxide (rGO) for cathodic CO2 electroreduction (CO2RR), while CuCoO on rGO was employed for anodic PET hydrolysate oxidation. Impressively, the anodic CuCoO@rGO catalyst displayed exceptional electro-activity, achieving an outstanding Faradaic efficiency (FE) of 85.7% at 1.5V vs. RHE. Simultaneously, the cathodic BOC@rGO catalyst demonstrated an impressive FE of 97.4% at -0.8 V vs. RHE, facilitating the production of formate from CO2RR. When integrated into an electrolyzer setup, this approach resulted in formic acid production at a low cell voltage of 1.9 V and a remarkable formate FE of 151.8% at 10 mA cm-2.Another system employed a 3D activated carbon felt (aCF) electrode as substrate and Bismuth has been deposited electrochemically on the CF (Bi@aCF) which acts as the cathode CO2RR and nickel cobalt phosphate-deposited carbon felt (NiCoPOx@CF) for the anodic PET hydrolysate oxidation process. This setup achieved a high FE of 94% during CO2RR at -0.8 V vs. RHE, producing formate, and a FE of 95% for anodic PET hydrolysate oxidation to formate at a low potential of 1.5 V vs. RHE. Remarkably, the two-electrode electrolyzer attained an extraordinary FE of 157% to produce formate at a cell voltage of 1.8 V. This breakthrough represents a novel pathway for upcycling PET waste, reducing CO2 emissions, and promoting environmental sustainability.Additionally, our experiments also delved into water electrolysis, where a novel strategy involving Ru embedded in a carbon nitride matrix was proposed. This approach, utilizing a covalent organic framework 2D CIN-1 structure with coordinated Ru+2, resulted in Ru oxide nanoparticles with low-valence Ru sites arranged in nanowires between layers of graphitic carbon nitride after pyrolysis. This material exhibited significantly lower overpotentials for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) compared to benchmark Pt and RuO2 catalysts, demonstrating remarkable catalytic stability. This discovery holds tremendous promise for advancing the field of water splitting and contributing to the development of sustainable energy solutions
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Blondiaux, Enguerrand. "Recyclage du CO2 : Une alternative à la pétrochimie pour la synthèse de molécules azotées". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112151/document.
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Les ressources carbonées fossiles (pétrole, charbon, gaz) couvrent 85 % des besoins énergétiques mondiaux et servent de matières premières pour 95 % des consommables chimiques organiques (plastiques, engrais, pesticides…). L’amenuisement des ressources pétrolières et l’accumulation du CO2 résultant de leur utilisation posent donc un problème écologique, énergétique et de disponibilité en matières premières pour l’industrie chimique. Dans ce contexte, il convient de proposer de nouvelles voies de synthèse de consommables chimiques, de manière à construire une industrie durable basée sur l’utilisation de ressources carbonées renouvelables. Contourner la pétrochimie et valoriser au maximum son déchet carboné, le CO2, pour construire des édifices moléculaires sans vocation énergétique (polymères, engrais, textiles synthétiques…) représente donc un enjeu scientifique de premier plan. Dans cet optique, de nouveaux procédés de synthèse de molécules azotées ont été mis au point à partir de CO2 comme source de carbone, d’amines comme source d’azote et de réducteurs doux de type hydrosilanes et hydroboranes comme source d’hydrogène. Ces procédés sont accélérés par l’utilisation de catalyseurs sans métaux et permettent de produire des formamides, des formamidines, des aminals et des méthylamines, qui constituent des molécules de bases de l’industrie chimiqueThe fossil carbon resources (oil, coal, gas) cover 85% of world energy portfolio and serve as raw materials for 95% of organic chemicals consumables (plastics, fertilizers, pesticides...). The decrease of oil resources and the accumulation of CO2 arising from their use thus pose environmental, energetic and availability of raw materials problems for the chemical industry. In this context, it is appropriate to propose new methods of chemical synthesis to build a sustainable industry based on the use of renewable carbon resources. Bypassing petrochemicals and valorize its carbon waste, CO2, to build molecular structures without energy purposes (polymers, fertilizers, synthetic textiles ...) represents a leading scientific challenge. From this perspective, new nitrogen molecules synthetic processes have been developed from CO2 as a carbon source, amines as nitrogen source and mild reductant such as hydrosilanes and hydroboranes as a hydrogen source. These processes are accelerated by the use of metal-free catalysts and enable the production of formamides, formamidines, aminals and methylamines, which are basic molecules of the chemical industry
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Fogeron, Thibault. "Synthèse de complexes inspirés des formiate déshydrogénases à Mo/W : application à la catalyse moléculaire de la réduction du CO2". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS132.
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Dans le contexte du réchauffement climatique, la recherche de sources d’énergie propres et durables est l’un des défis les plus importants de notre époque. La réduction du CO2 permettrait un stockage des énergies renouvelables et une diminution de la concentration de ce gaz dans l’atmosphère. Le développement de catalyseurs moléculaires permet d’étudier avec précision les relations entre structures et réactivités. Malheureusement, la librairie de catalyseurs homogènes existant dans la littérature est réduite. Afin de chercher de nouveaux catalyseurs potentiels, nous avons décidé de nous inspirer du site actif des formiate déshydrogénases (FDH). La synthèse de molécules mimes de ce site actif constitue un challenge intéressant. Dans cette thèse, nous décrivons l’obtention de deux ligands, inspirés de la molybdoptérine (chapitre I). L’obtention des complexes CoCp(dithiolène) a permis de mieux caractériser ces ligands (chapitre II). De plus, l’observation de la réactivité des ligands dans les conditions électrochimiques nous a permis d’anticiper leurs comportements lors des études catalytiques. L’obtention des complexes [MoO(dithiolène)2]2- à partir des ligands bio-inspirés constitue les synthèses de mimes des sites actifs des FDH les plus abouties de la littérature (chapitre III). Ce chapitre a également été l’occasion de travailler sur la généralisation de méthodologies de synthèses. Les complexes [Ni(dithiolène)2]- obtenus à partir des ligands bio-mimétiques constituent les premiers catalyseurs dithiolène pour la réduction du CO2 (chapitre IV). Ils font partie des rares complexes homogènes à base de métaux non-nobles catalysant la réduction du CO2 en formiateIn the context of global warming, the development of new sources of energy, clean and sustainable, is a key challenge of our society. The reduction of CO2 could allow the storage of renewable energies and offer an answer to the dramatic increase of CO2 in the atmosphere. Development of molecular catalysts offers the possibility of studying the structure-reactivity relationships. However, the library of existing homogeneous catalysts in the literature is quite limited. In order to find new potential catalysts, we decided to take inspiration from the active site of formate dehydrogenases (FDH). The synthesis of molecules mimicking this active site is an interesting challenge. In this thesis, we described the synthesis of two ligands inspired from the molybdopterin (chapter I). The synthesis of CoCp(dithiolène) complexes allows us to better characterize these ligands (chapter II). Moreover, the observation of the reactivity of these ligands allows us to understand their behaviour during electrocatalysis. The [MoO(dithiolene)2]2- complexes obtained from the bio-inspired ligands are,so far, the best mimics of the active site of FDH in the literature (chapter III). In this chapter, the generalization of synthetic procedure was also explored. Finally, [Ni(dithiolene)2]- synthesize from the bio-inspired ligands are the first dithiolene complexes able to reduce CO2 (chapter IV). They are among the few non-nobles metal complexes catalyzing the reduction of CO2 into formate
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Nambukara, Wellala Nadeesha P. "Synthesis and Catalytic Activities of Nickel Complexes Bearing Flexible Tridentate Ligands". University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491561548324255.
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Conte, Carlos Henrique. "Utilização de catalisadores de cobre e cobalto suportados em CeO2, TiO2 e matrizes de CeO2-TiO2, para redução de NO com CO na ausência ou presença de O2". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-14042008-151055/.
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A redução da emissão de compostos nitrogenados tem sido um dos grandes desafios da área de proteção ambiental e o tratamento catalítico pode reduzir significativamente tal emissão. Neste caminho, têm sido testadas várias categorias de catalisadores. Considerando-se o potencial de utilização de catalisadores de cobre e de cobalto nos processos de abatimento de compostos nitrogenados, bem como a necessidade de exploração dos efeitos gerados pelos suportes de óxido de cério e óxido de titânio, este trabalho teve como objetivos a preparação e a caracterização dos sistemas catalíticos CuO e Co3 O4 suportados em TiO2 , CeO2 e CeO2 -TiO3 (1%, 10%, 20% e 50% de CeO2 ), para aplicação no processo de redução de NO com CO na presença e ausência de O2 . Os catalisadores foram obtidos a partir do método de impregnação. Na caracterização das amostras foram utilizadas as técnicas de difração de raios X (DRX), redução à temperatura programada com H2 (RTP-H2 ), espectroscopia Raman, espectroscopia por energia dispersiva de raios X (EDX), fisissorção de nitrogênio e espectroscopia UV-visível próxima a região do infra-vermelho (UV-VIS-NIR). Os resultados da caracterização mostraram que os catalisadores apresentam fases de CuO altamente dispersas, bem como formando cristalitos com os suportes. Mostraram, também, que o cobalto está sobre a forma oxida Co3 O4 . As reações de redução de NO com CO mostraram que os catalisadores de cobre são mais ativos para estas reações e a adição do suporte CeO2 em TiO2 aumenta significativamente esta atividade. A adição de O2 na reação diminuiu a atividade frente à reação de redução de NO, isso porque o oxigênio é adsorvido sobre a superfície do catalisador, diminuindo sua atividade.The reduction of the nitrogen composites emissions has been one of the great challenges of the ambient protection area and the catalytic treatment can reduce significantly such emissions. In this way, it has been tested some categories of catalysts. Considering the potential of use of copper and cobalt catalysts in the processes of nitrogen composites discouragement, as well as the necessity of exploration of the effect generated for CeO2 and TiO2 supported , this work had as objective the preparation and the characterization of the catalytic systems supported CuO and Co3O4 in TiO2, CeO2 and CeO2-TiO2 (1%, 10%, 20% and 50% of CeO2), for application in the reduction process of NO with CO in presence and absence of O2. The catalysts had been gotten from the impregnation method. In the characterization of the samples the techniques that had been used was: X-ray diffraction had been used, temperature programmed reduction, Raman spectroscopy, energy dispersive X-ray spectroscopy, nitrogen physsisorption and UV-visible spectroscopy next the region to the infra-red ray (UV-VIS-NIR). The results of the characterization had shown that the catalysts present highly dispersed phases of CuO, as well as cristalitts. And, that cobalto meets under the form Co3O4. The reactions of reduction of NO with CO had shown that the copper catalysts are more active than the cobalto and the addition of the CeO2 support in TiO2 increases significantly this activity. The addition of O2 in the reaction diminished the activity front to the reaction of reduction of NO, just because the oxygen is adsorbed on the surface of the catalysts, diminishing its activity
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Garcia, Janaina de Souza. "Perovskitas preparadas pelo método do citrato como catalisadores para a reação de redução de NO com CO". Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-25082009-092347/.
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Um dos maiores problemas que o homem tem encontrado em função de seu desenvolvimento é a poluição. Os principais responsáveis pela poluição atmosférica são os veículos automotores e para minimizar a poluição gerada por estes fez-se necessário o uso de catalisadores. Estes catalisadores, chamados de catalisadores de \"três vias\", atualmente têm como sítios ativos metais nobres, o que eleva muito o seu custo e leva motoristas a dispensarem este equipamento. O objetivo deste estudo foi preparar, caracterizar e estudar materiais tipo perovskitas (La2CuO4, La(2-x)CexCuO4, La2Mo2O9, LaCoO3, LaNiO3, La2CuO4/LaNiO3) como catalisadores para a reação de redução de NO com CO, com a finalidade de encontrar uma alternativa para substituir os metais nobres nos conversores catalíticos comerciais. Os catalisadores foram preparados pelo método do citrato, calcinados em 800 ou 900oC, caracterizados por difração de raios-X, redução a temperatura programada, área específica e análise química, sendo observada a formação de perovskita em todas as caracterizações. Durante os ensaios catalíticos frente a reação de redução de NO com CO, os catalisadores calcinados em 800oC foram mais ativos em relação aos calcinados em 900oC e em relação aos metais componentes da perovskita, quanto mais preenchida a banda de valência do metal na estrutura perovskita, maior a sua atividade.One of the biggest problems that man has found because of his development is the pollution. The main responsible for atmospheric pollution are the automotive vehicles and to minimize the pollution produced by them it has been necessary to use catalysts. These catalysts, called \"three way catalysts\", actually have noble metals like active sites, what takes up very much their cost and let drivers dispense this equipment. The objective oh this study was to prepare, characterize and study materials of perovskites kind (La2CuO4, La(2-x)CexCuO4, La2Mo2O9, LaCoO3, LaNiO3, La2CuO4/LaNiO3) like catalysts to the reaction of reduction of NO with CO, with the end of find a alternative to substitute the noble metal in the commercial catalytic conversers. The catalysts were prepared by citrate method, calcined at 800 or 900oC, characterized by X-ray diffraction, temperature programmed reduction, specific area and chemical analysis, being observed the formation of perovskite in all characterizations. During the catalytic research to the reaction of NO with CO, the catalysts calcined at 800oC were more active compared to those calcined at 900o and, in relation to the component metal of the perovskite, how more filled the valence band of the metal in the structure of perovskite, better its activity.
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Möller, Tim [Verfasser], Peter [Akademischer Betreuer] Strasser, Peter [Gutachter] Strasser e Mehtap [Gutachter] Özaslan. "Structural and catalytic studies of copper-based materials for the direct electrochemical reduction of CO2 – investigations from fundamental to technological current densities / Tim Möller ; Gutachter: Peter Strasser, Mehtap Özaslan ; Betreuer: Peter Strasser". Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1239177178/34.
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Zhang, Lin. "Photoelectrocatalytic CO2 conversion in ionic liquid/aqueous mixture solution studied by scanning electrochemical microscopy". Thesis, Sorbonne université, 2020. https://accesdistant.sorbonne-universite.fr/login?url=http://theses-intra.upmc.fr/modules/resources/download/theses/2020SORUS122.pdf.
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Cette thèse concerne l’étude de la réaction photoélectrochimique de réduction du CO2 (PEC CO2RR) sur le semi-conducteur de type p CuCo2O4 en abordant le rôle cocatalytique des RTIL à base d'imidazolium par microscopie photoélectrochimique à balayage (SPECM). Le CuCo2O4 a été étudié dans différents électrolytes supports, notamment une solution aqueuse, une solution de mélange binaire (25 vol.% [C2mim][BF4]/H2O et 25 vol.% [C4mim][BF4]/H2O) et des liquides ioniques pur pour explorer par SPECM le rôle des RTIL dans les performances des PEC. Un courant de photoréduction significativement amélioré sous l'éclairage UV-vis et visible est obtenu dans une solution à 25 vol.% [C2mim][BF4]/H2O. Seul le CO généré par la PEC CO2RR a été détecté sur une fibre optique à double sonde - ultra-microélectrode (OF-UME) développée au laboratoire et sur une électrolyse en volume sous illumination. La formation de CO à des potentiels plus positifs que la valeur thermodynamique est rapportée ici et il est clairement indiqué que la réduction directe du CO2 à la surface de l'électrode n'est pas le mécanisme. Un schéma de réaction possible pour la PEC CO2RR par l'intermédiaire de [C2mim]+ est proposé. Ainsi, nos résultats ont démontré pour la première fois le rôle cocatalytique de [C2mim]+ pour le PEC CO2RR. En outre, la CO2RR électrochimique a également été étudiée sur divers catalyseurs de métaux de transition, d'azote et de carbone (M–N–Cs). 25%Fe25%Co–N–C a montré la meilleure performance parmi les M–N–Cs étudiés. La présence de sites Co a fourni un effet synergique pour la génération de microcubes distribués riches en Fe, qui agissent comme des sites actifs dans la CO2RR électrochimiqueThis thesis studies photoelectrochemical CO2 reduction reaction (PEC CO2RR) on p-type semiconductor CuCo2O4 addressing the cocatalytic role of imidazolium based RTILs by scanning photoelectrochemical microscopy (SPECM). CuCo2O4 was studied in different solvent supporting electrolyte systems including: aqueous solution (0.1 M KHCO3 and 0.1 M Na2SO4), binary mixture solution (25 vol.% [C2mim][BF4]/H2O and 25 vol.% [C4mim][BF4]/H2O) and pure RTILs ([C2mim][BF4], [C4mim][BF4]) to explore by SPECM the role of RTILs in CuCo2O4 semiconductor PEC performance. Significantly enhanced photoreduction current under both UV-vis and visible light illumination is reported in 25 vol.% [C2mim][BF4]/H2O solution. Only CO generated from PEC CO2RR was detected using an in-situ detection method based on a home-made dual tip optical fiber-ultramicroelectrode (OF-UME) and from bulk electrolysis under illumination. The formation of CO at potentials more positive than the thermodynamic value clearly points out that direct CO2 reduction on the electrode surface is not the mechanism. A possible reaction scheme for the PEC CO2RR mediated by [C2mim]+ is proposed. Thus, our results have demonstrated for the first time the cocatalytic role of [C2mim]+ for the PEC CO2RR. In addition, electrochemical CO2RR has also been studied on various synthesized transition metal–nitrogen–carbon catalysts (M–N–Cs) by rotating disk electrode. 25%Fe25%Co–N–C exhibited the best performance among the studied M–N–Cs in this thesis. The presence of Co sites in that catalyst provided synergic effect for the generation of distributed Fe-rich microcubes, which act as active sites in electrochemical CO2RR
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Ju, Wen [Verfasser], Peter [Akademischer Betreuer] Strasser, Peter [Gutachter] Strasser e Yong [Gutachter] Lei. "Metal-nitrogen-doped carbon (M-N-C) catalysts for the direct electrochemical reduction of CO2 to value-added chemicals and fuels : materials, mechanisms and cell performance / Wen Ju ; Gutachter: Peter Strasser, Yong Lei ; Betreuer: Peter Strasser". Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1189206250/34.
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Zsoldos, Daniela. "Complexes mono et bis bipyridine carbonyle de ruthénium(II), précurseurs de polymères organométalliques : propriétés électrochimiques et applications à l'électrocatalyse de la réduction du CO2 en milieu aqueux". Université Joseph Fourier (Grenoble), 1997. http://www.theses.fr/1997GRE10027.
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Ce memoire est consacre a l'etude de l'electrocatalytique de la reduction du co#2 par des complexes mono et bis bipyridine bis carbonyle de ru(ii), en phase homogene ou supportee (electrodes modifiees). Une partie de ce travail traite des proprietes electrochimiques des complexes trans-(cl)-cis-(co)-ru(l)(co)#2cl#2 (l = 2,2'-bipyridine substituee ou non ou 1,10-phenanthroline) et cis-(bpy)-cis-(co)-ru(bpy)#2(co)#2#2#+, precurseurs de polymeres du type ru(l)(co)#2#n, espece electrocatalytique clees. Le mecanisme d'electrogeneration de ces polymeres organometallique a pu etre determine, grace en particulier a l'etude des complexes stereoisomeres cis-(cl)-cis-(co)-ru(l)(co)#2xy#n#+(x = cl#- ; y = cl#- ou c(o)och#3#-). Ceux-ci ont un comportement electrochimique different des complexes equivalents trans-(cl)-cis-(co) et conduisent exclusivement a des dimeres. Tous ces complexes se sont averes etre d'excellents catalyseurs pour l'electroreduction du co#2 en milieu hydro-organique en phase homogene ou supportee. Par ailleurs, le probleme de l'instabilite a l'oxygene des electrodes modifiees par les films de ru(l)(co)#2#n a ete contourne grace a l'utilisation d'un autre type de cathodes moleculaires. Ces dernieres ont ete realisees par immobilisation, a la surface d'electrodes, des complexes precurseurs, dans des films de polypyrrole fonctionnalises. Une etude detaillee des differents parametres influencant l'orientation de la reaction de reduction du co#2 vers la production d'ions formiate (en particulier la substitution du ligand bipyridine) dans un electrolyte purement aqueux, a permis d'etablir les conditions optimales pour l'obtention de rendements electriques quasi quantitatifs.
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Matz, Olivier. "Dissociation de H2 sur des surfaces d’oxydes de cérium : étude de la réductibilité". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS270.
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L’oxyde de cérium suscite un fort intérêt en catalyse hétérogène, en particulier dans le domaine de la semi-hydrogénation des alcynes. En effet, il a été montré que CeO2 est capable de dissocier la molécule de H2 en l’absence de métaux nobles en faisant intervenir un intermédiaire hydrure, espèce catalytiquement active. Cependant, sur la surface stoechiométrique (111)-CeO2, cet intermédiaire n’est pas stable et reste systématiquement défavorisé par rapport au produit de dissociation homolytique. Bien que la plupart des applications de CeO2 soient reliées à ses propriétés redox, il y a un manque de connaissance de l’effet de la réduction sur la dissociation de H2. Dans ce contexte, nous proposons une étude complète de la dissociation de H2 par la modélisation à l’échelle atomique basée sur une approche de type DFT+U appliquée en conditions périodiques. L’effet de la réduction a été pris en compte en considérant des surfaces : stoechiométriques, localement réduites via la formation de lacunes d’oxygène, et totalement réduites. L’étude systématique de la dissociation de H2 sur différentes surfaces a permis d’identifier les paramètres clés impliqués et d’en extraire des relations structure-propriété-réactivité. En particulier, nos résultats indiquent une forte dépendance entre la topologie des surfaces et leurs réactivités. De plus, nous avons mis en évidence le rôle clé de la réductibilité : l’activité catalytique augmente graduellement avec le taux de réduction. Nos travaux permettent donc d’interpréter les observations expérimentales en proposant un mécanisme réactionnel, et d’explorer des voies pour orienter la réactivité des matériaux à base d’oxydes de cériumThese last years, cerium oxide has received a great interest in heterogenous catalysis, in particular in the alkyne semi-hydrogenation field. Indeed, it has been shown that CeO2 is able to dissociate H2 molecule in absence of noble metals. Interestingly, the hydrogenation of ceria is found to take place through an hydride intermediate which is a catalytically active species. However, on the stoichiometric (111)-CeO2 surface, this intermediate is not stable and remains systematically unfavored compared to the homolytic product. Although most of the CeO2 applications are related to its redox properties, there is a lack of knowledge regarding the reduction effect on the H2 dissociation. In this context, we propose a full study of H2 dissociation by the modelling of surface reactivity at the atomic scale based on the DFT+U approach applied in periodic conditions. The reduction effect was studied by considering: (i) stoichiometric surfaces (CeO2), (ii) partially reduced surfaces with the formation of oxygen vacancies (CeO2-x), and (iii) fully reduced surfaces (Ce2O3). The systematic study of H2 dissociation on different surfaces allows us to identify the key parameters and to extract structure-property-reactivity relationships. In particular, our results show a strong relationship between the topology of the surfaces and their reactivities. Moreover, we have highlighted the key role of the reducibility: the catalytic activity increases gradually with the reduction rate. Our works allow to interpret the experimental observations by proposing a reaction mechanism, as well as to explore new ways of rational design of cerium oxides based materials
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Pinheiro, Danielle Lobo Justo. "O uso de azalactonas em síntese orgânica: preparação, aplicação em reações de formação de ligação C-C e em síntese total". Universidade Federal de Juiz de Fora (UFJF), 2018. https://repositorio.ufjf.br/jspui/handle/ufjf/7551.
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Azalactonas são heterociclos derivados de aminoácidos protegidos e ciclizados. Por conter em sua estrutura um sítio eletrofílico, um sítio pro-nucleofílico, além de um sítio nucleofílico ou eletrofílico (que será determinado pelas condições reacionais), esses compostos são extremamente versáteis. Nesse trabalho é demonstrado a reação das azalactonas com o reagente de Schwartz, que através de uma de redução quimiosseletiva gera derivados de aminoaldeídos com excelentes rendimentos em apenas 2 minutos de reação. Outra reação de redução quimiosseletiva demonstrada no trabalho envolve o uso de azalactonas de Erlenmeyer, hidrogênio e Pd/C como catalisador. Dessa forma, azalactonas saturadas funcionalizadas, foram possíveis de ser obtidas em uma metodologia simples, com excelentes rendimentos. O processo foi ainda adaptado para reações em um sistema one-pot, produzindo assim, adutos de Michael, Mannich e produtos de abertura de maneira simples e eficiente. O sítio nucleofílico das azalactonas também é explorado em reações de dimerização diastereosseletivas, utilizando uma base de Brønsted formada in situ pela reação entre acetonitrila e sal tricloroacetato de potássio ou sódio. O mecanismo da reação e estudos cinéticos são demonstrados a partir de uma análise obtida por experimentos online no RMN de ¹H. Além disso, um análogo de um produto natural é obtido através de uma redução estereosseletiva dos dímeros. O sítio nucleofílico das azalactonas também é explorado em reações de carbonilação α-arilativa catalisadas por Pd, utilizando o sistema de duas câmaras, seguido de sua abertura, obtendo, dessa forma, aminoácidos α,α-dissubstituídos protegidos. O mecanismo da reação é proposto após reações controle terem sido realizadas. Os mesmos aminoácidos também puderam ser sintetizados e marcados com o ¹³C. Esses compostos marcados foram aplicados em reações quimiosseletivas, como a reação de descarboxilação de Krapcho, reduções quimiosseletivas, e síntese de heterociclos como as oxazolonas e pirazolonas.
Azlactones are heterocycles derived from amino acids. There are an electrophilic site, a pro-nucleophilic site, and a nucleophilic or electrophilic site (determined by the reaction conditions). These compounds are extremely versatile. In this work the reaction of the azlactones with Schwartz reagent is demonstrated. A chemosselective reduction of these compounds is possible to generate aminoaldehydes in excellent yields in only 2 minutes reaction. Chemosselective reduction of Erlenmeyer azlactones is also demonstrated by using hydrogen gas and Pd / C as a catalyst. In this way, functionalized saturated azlactones are possible to obtain in excellent yields. The process was further adapted to reactions in a one-pot system, producing Michael, Mannich and opening products in a simple and efficient manner. The nucleophilic site of azlactones is also explored in the diastereoselective dimerization reactions promoted by a Brønsted base, affording by the reaction in situ between acetonitrile and potassium or sodium trichloroacetate salt. The mechanism of the reaction and kinetic studies are demonstrated from an analysis obtained by ¹H NMR online experiments. In addition, a stereoselective reduction of a dimer analogue gave a natural product in high both yield and diastereoselectivity. The nucleophilic site of the azalactones is exploited in Pd catalyzed α- arylation carbonylation reactions, using the two-chamber system, followed by their opening, thereby obtaining protected α,α -disubstituted amino acids. The mechanism of the reaction is proposed based on control reactions. The same amino acids could also be synthesized with ¹³C-labeled CO. These coumpounds were applied in chemosselective reactions, such as krapcho decarboxylation reaction, chemosselective reduction, and synthesis of heterocycles such as oxazolones and pyrazolones.
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Lin, I.-Chieh, e 林逸杰. "Photo-Catalysis CO2 Reduction ByMicrowave Synthesis Tin Disulfide". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/82321434714528510279.
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碩士國立臺灣師範大學
化學系
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With a photocatalysis system for CO2 reduction reactions linked to a halogen lamp solar source, we continuously collected highly valuable organic products in-situ by using tin disulfide photocatalysis in solid - gas phase reaction with Gas chromatography/Flame ionized detector (GC/FID). Then, using a newly developed calibration curve for the real time system, we converted the signal to measure the quantum efficiency (QE). In this study, we shortened the reaction time and maintained precise control of our system conditions by using a programmable microwave-assisted synthesis system for tin disulfide particles synthetization; thusly, we could reproduce high quality samples easily. Six major techniques were used to characterize the particles: Raman spectroscopy and X-ray diffraction spectroscopy were used for crystallinity analysis, a Scanning Electron Microscopy for microstructure characterization, X-ray absorption spectroscopy from NSRRC, to quantify different components by linear combination of standard compounds, and photo-electron spectroscopy in air coupled with UV-Visible absorption spectroscopy to find the relationship between band position and photocatalytic reactivity. We tried optimizing efficiency of the tin disulfide by: sampling different solvents (ethylene glycol, ethanol, and deionized water ) in the microwave reaction, testing different reaction times (5 min - 120 min), and altering the concentration of SDS (0-2000%). We found that by synthesizing tin disulfide in deionized water with 1% SDS for 1 hour we achieved a QE of 0.028%, which is 25 times better than the commercial tin disulfide. Furthermore, the CO2 reduction reaction resulted in the formation of acetaldehyde, implying eight electrons transferred. In total, we found a new process for the synthesis of tin disulfide that demonstrates a significant enhancement to the reduction activity of carbon dioxide.
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Chang, Jyun-Pu, e 張鈞普. "A Cluster Model Study on the Interaction between p-type Semiconductor and Anchoring Groups for CO2 Reduction Catalysis". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/49793114205234344055.
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