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Author: Jorge Becerra Sanchez Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
De nos jours, le développement de nouveaux matériaux capables de récolter la lumière solaire de manière efficace pour des applications photocatalytiques est un véritable défi pour la science. Par conséquent, les matériaux réticulaires qui agissent comme des blocs de construction, constitués de joints entre des lieurs organiques et des métaux, avec des propriétés plus adaptées à la photocatalyse, sont devenus encore plus attractifs. Cependant, conférer une fonctionnalité à ces matériaux avec un minimum de défauts cristallins, qui conduisent à une recombinaison de charge électron-trou, et une absorption maximale de la lumière reste un problème. Pour cette raison, différentes stratégies, comme le dopage, l'utilisation de cocatalyseur entre autres, ont été rapportées comme alternatives pour minimiser les problèmes mentionnés ci-dessus et par conséquent les désintégrations photocatalytiques. Néanmoins, les nanostructures de métaux nobles ont récemment montré des propriétés exceptionnelles d'absorption de la lumière, dans lesquelles des pairs électron-trous peuvent être générés et utilisés comme « porteurs de charges », qui améliorent l'activité photocatalytique sur les matériaux pour différentes applications. Les propriétés caractéristiques de ces nanostructures sont associées à l'effet des phénomènes de résonance plasmonique de surface localisée (LSPR en anglais). Les stratégies de préparation de matériaux plasmoniques pour les systèmes photocatalytiques sont très importantes pour améliorer les performances des réactions et les processus photocatalytiques souhaités. Des aspects critiques tels que la morphologie, la taille, les précurseurs chimiques entre autres doivent être pris en compte. Par exemple, l'utilisation du même métal avec une forme différente pourrait affecter ses performances photocatalytiques et déterminer son application. Ce document offre des preuves scientifiques intéressantes, dans le domaine de la photocatalyse, que les techniques d'ingénierie mentionnées ci-dessus sont cruciales pour le développement de matériaux à base de plasmons adaptés à la conversion du CO2. Parmi ces preuves, des nanosphères d'or décorées à la surface d'un cadre d'imidazolate zéolitique (ZIF-67) ont montré un taux de génération de méthanol maximal de 1.6 mmol gcat−1 h−1 avec un rendement quantique apparent (AQY en anglais) de 6.4 %. Alors que les nanoparticules d'or en forme de nanotige ont doublé ce taux avec un AQY de 7.4 %. De plus, les nanoparticules d'or liées chimiquement avec des agents tensioactifs fonctionnels ont montré une amélioration significative des performances avec des taux de génération de 2.5 mmol gcat−1 h−1 en utilisant des charges métalliques inférieures et un AQY de 3.7 %. Alors qu'il existe un nombre croissant de rapports sûr de nouveaux matériaux réticulaires nanocomposites pour les processus photochimiques; les rapports de matériaux plasmoniques sur la chimie réticulaire sont encore rares. Par conséquent, ce rapport fournit un aperçu approfondi des différents concepts liés aux matériaux plasmoniques et à leurs applications sur les matériaux réticulaires afin d'identifier leurs opportunités et leurs défis sur la photocatalyse pour de futures considérations industrielles.
Author: Jorge Becerra Sanchez Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
De nos jours, le développement de nouveaux matériaux capables de récolter la lumière solaire de manière efficace pour des applications photocatalytiques est un véritable défi pour la science. Par conséquent, les matériaux réticulaires qui agissent comme des blocs de construction, constitués de joints entre des lieurs organiques et des métaux, avec des propriétés plus adaptées à la photocatalyse, sont devenus encore plus attractifs. Cependant, conférer une fonctionnalité à ces matériaux avec un minimum de défauts cristallins, qui conduisent à une recombinaison de charge électron-trou, et une absorption maximale de la lumière reste un problème. Pour cette raison, différentes stratégies, comme le dopage, l'utilisation de cocatalyseur entre autres, ont été rapportées comme alternatives pour minimiser les problèmes mentionnés ci-dessus et par conséquent les désintégrations photocatalytiques. Néanmoins, les nanostructures de métaux nobles ont récemment montré des propriétés exceptionnelles d'absorption de la lumière, dans lesquelles des pairs électron-trous peuvent être générés et utilisés comme « porteurs de charges », qui améliorent l'activité photocatalytique sur les matériaux pour différentes applications. Les propriétés caractéristiques de ces nanostructures sont associées à l'effet des phénomènes de résonance plasmonique de surface localisée (LSPR en anglais). Les stratégies de préparation de matériaux plasmoniques pour les systèmes photocatalytiques sont très importantes pour améliorer les performances des réactions et les processus photocatalytiques souhaités. Des aspects critiques tels que la morphologie, la taille, les précurseurs chimiques entre autres doivent être pris en compte. Par exemple, l'utilisation du même métal avec une forme différente pourrait affecter ses performances photocatalytiques et déterminer son application. Ce document offre des preuves scientifiques intéressantes, dans le domaine de la photocatalyse, que les techniques d'ingénierie mentionnées ci-dessus sont cruciales pour le développement de matériaux à base de plasmons adaptés à la conversion du CO2. Parmi ces preuves, des nanosphères d'or décorées à la surface d'un cadre d'imidazolate zéolitique (ZIF-67) ont montré un taux de génération de méthanol maximal de 1.6 mmol gcat−1 h−1 avec un rendement quantique apparent (AQY en anglais) de 6.4 %. Alors que les nanoparticules d'or en forme de nanotige ont doublé ce taux avec un AQY de 7.4 %. De plus, les nanoparticules d'or liées chimiquement avec des agents tensioactifs fonctionnels ont montré une amélioration significative des performances avec des taux de génération de 2.5 mmol gcat−1 h−1 en utilisant des charges métalliques inférieures et un AQY de 3.7 %. Alors qu'il existe un nombre croissant de rapports sûr de nouveaux matériaux réticulaires nanocomposites pour les processus photochimiques; les rapports de matériaux plasmoniques sur la chimie réticulaire sont encore rares. Par conséquent, ce rapport fournit un aperçu approfondi des différents concepts liés aux matériaux plasmoniques et à leurs applications sur les matériaux réticulaires afin d'identifier leurs opportunités et leurs défis sur la photocatalyse pour de futures considérations industrielles.
Author: Vishnu Nair Gopalakrishnan Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
The ensuing thesis examines the conversion of carbon dioxide (CO2) to value-added chemical and fuels under solar light irradiation by employing some of the emerging photocatalytic materials known as covalent organic frameworks (COFs). This approach of photocatalytic process is considered to be one of the most viable remedies to global warming and energy crisis dilemmas. Importantly, this thesis delivers three novel nanostructured hybrid composites based on COFs for photocatalytic CO2 reduction to value-added chemicals and fuels. Light-harvesting, charge separation, and surface reactions are critical aspects that have an enormous impact on CO2 photoreduction. Covalent organic frameworks can be suitable candidates for these processes as they offer outstanding structural features and properties. Diverse nanostructured photocatalysts are actively being developed for CO2 photoreduction. Multidimensional nanostructures and nanocomposite heterostructures are widely studied because of their excellent attributes such as efficient separation and long lifetime of the excited charge carriers. Promisingly, nanostructures and nanocomposites of the covalent organic frameworks with graphene and its derivatives, metal dichalcogenides and plasmonic materials exhibit excellent photocatalytic performance, according to the literature reports. In this investigation, a keto-enamine TpPa-1 covalent organic framework and reduced graphene oxide nanosheet nanocomposite are developed by an in-situ assembling technique. The covalent interactions between TpPa-1 and rGO facilitated the formation of band edges with required potential and thereby to achieve an improved charge separation along with rapid migration of charge carriers to the surface toward the selective reduction of CO2. By the support of the electron mediator [Co(bpy)3]2+ in the hybrid served as the active sites for the coordination, activation, and reduction of CO2 molecules to CO. A hollow nano spherical TpPa-1 covalent organic framework (COF) integrated with single atom Co-1T-MoS2 (TpPa-1/Co-1T-MoS2) is further designed and developed through a dual-ligand strategy to tune the band edge potential and enhance the charge separation to improve CO2 photoreduction efficiency of the system. The interactions between TpPa-1 and Co-1T-MoS2 aided and enhanced the charge separation as well as charge carrier migration to the surface resulted in selective conversion CO2 to CO. Au plasmonic nanoparticles adorned three-dimensional hollow porphyrin-based covalent organic framework with Co single atom (COF-366-Co[subscript (H)]/Au) is developed via dual-ligand strategy and post-synthetic metallization method and found that this system significantly boosted up the CO2 photoreduction efficiency. It utilizes the plasmon-induced energetic electron transfer, enhanced light harvesting, and surface reactions to drive the photocatalytic redox reactions. The developed COF-366-Co[subscript (H)]/Au exhibited fine activity toward photocatalytic CO2 reduction under visible light irradiation, which yielded the CO at a rate up to ~1200 μmolg−1h−1 with a selectivity of 98% over H2.
Author: Alejandro Castañeda Flores Publisher: ISBN: Category : Carbon dioxide mitigation Languages : en Pages : 72
Book Description
A new photocatalytic material was synthesized to investigate its performance for the photoreduction of carbon dioxide (CO2) in the presence of water vapor (H2O) to valuable products such as carbon monoxide (CO) and methane (CH4). The performance was studied using a gas chromatograph (GC) with a flame ionization detector (FID) and a thermal conductivity detector (TCD). The new photocatalytic material was an ionic liquid functionalized reduced graphite oxide (IL-RGO (high conductive surface))-TiO2 (photocatalyst) nanocomposite. Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and UV-vis absorption spectroscopy techniques were employed to characterize the new catalyst. In the series of experiments performed, the nanocomposite material was confined in a UV-quartz batch reactor, exposed to CO2 and H2O and illuminated by UV light. The primary product formed was CO with a maximum production ranging from 0.18-1.02 mol(gcatalyst-hour)-1 for TiO2 and 0.41-1.41 mol(gcatalyst-hour)-1 for IL-RGO-TiO2. A trace amount of CH4 was also formed with its maximum ranging from 0.009-0.01 mol(gcatalyst-hour)-1 for TiO2 and 0.01-0.04 mol(gcatalyst-hour)-1 for IL-RGO-TiO2. A series of background experiments were conducted and results showed that; (a) the use of a ionic liquid functionalized reduced graphite oxide -TiO2 produced more products as compared to commercial TiO2, (b) the addition of methanol as a hole scavenger boosted the production of CO but not CH4, (c) a higher and lower reduction time of IL-RGO as compared to the usual 24 hours of reduction presented basically the same production of CO and CH4, (d) the positive effect of having an ionic liquid was demonstrated by the double production of CO obtained for IL-RGO-TiO2 as compared to RGO-TiO2 and (e) a change in the amount of IL-RGO in the IL-RGO-TiO2 represented a small difference in the CO production but not in the CH4 production. This work ultimately demonstrated the huge potential of the utility of a UV-responsive ionic liquid functionalized reduced graphite oxide-TiO2 nano-composite for the reduction of CO2 in the presence of H2O for the production of fuels.
Author: Constantinos Dimitrakakis Publisher: ISBN: Category : Languages : en Pages : 544
Book Description
Zeolitic Imidazolate Frameworks (ZIFs) are of interest for highly specialised applications in fluid separation, chemical sensing and heterogeneous catalysis and the development of appropriate thin film structures that maximise the utilisation of these materials is of great importance. In this Dissertation, new techniques for the incorporation of ZIFs into various polymeric thin film architectures were explored to exploit their interesting structural and chemical properties. To this end, the chemical compatibility between ZIFs and polymers and the ability to exert control over the positioning of ZIFs on polymeric surfaces were explored in depth and new techniques developed to address these issues.A novel top down patterning process was successfully demonstrated and was the first top down technique described for ZIFs. A pre formed dense layer of ZIF 9 particles, over a layer of a photoresist material such as phenyltriethoxysilane or poly(o hydroxyl imide) on a silicon substrate, was exposed to intense X ray irradiation such that the photoresist underwent chemical hardening. The unexposed regions were then rinsed away to leave behind a patterned array of ZIF regions on the substrate, with no damage occurring to the ZIF material.A bottom up methodology was developed using radio frequency glow discharge plasma polymerisation to apply functional coatings over polytetrafluoroethylene substrates in a patterned manner using a physical masking process. It was found that plasma polymer coatings containing high quantities of oxygenated functionalities, such as carboxylic acid or hydroxyl groups, promoted the in situ growth of ZIFs on surfaces, while amine based plasma polymers instead inhibited growth. These coatings were also found to promote the growth of other porous framework materials. Subsequent functionalisation of the plasma polymer coatings in a second step was performed, using either 3 aminopropyltriethoxysilane or poly(styrene co maleic anhydride), to bind specifically to the plasma polymer treated regions of the patterned surfaces. The introduction of higher quantities of the favourable oxygenated functionalities further enhanced ZIF growth in a patterned manner and led to the formation of denser coatings of smaller crystalline particles over the surfaces. The improvement of the performance of mixed matrix membranes for gas separations was also explored via the inclusion of a room temperature ionic liquid as a third component in the structure. This component was added to fill interfacial voids between ZIF nanoparticles and a gas permeable polybenzimidazole matrix, caused by poor interfacial chemical compatibility, and thus improve the utilisation of the ZIF nanoparticles and the selectivity of the membrane for H2 gas over CO2 and N2. A synergistic maximum loading of the ZIF and the ionic liquid loading within the membrane was observed such that the performance of the membrane was maximised for both its H2 permeability and its selectivity of H2 over CO2 and N2. With higher loadings beyond this synergistic level, the performance of the membranes decreased significantly as the polybenzimidazole matrix became excessively strained.
Author: Sanjit Das Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 0
Book Description
The use of fossil fuels to meet our energy requirements has contributed significantly to increase the atmospheric carbon dioxide level causing global warming. This calls for the development of processes to reduce CO2 level and its conversion to other value-added products. In this regard, photocatalytic CO2 reduction using sunlight is a key reaction to achieve artificial photosynthesis to produce solar or renewable fuels. Designing efficient and robust catalysts for this reduction reaction is crucial and remains a challenging task. Recently, N-heterocyclic carbenes (NHCs) have emerged as strong donor ligands that are useful for forming transition metal-based catalysts. The combination of two NHCs with a central pyridyl ring in a symmetric fashion results in a tridentate CNC-pincer framework that can promote catalyst stability. Metal complexes containing such CNC-pincer ligands along with other co-ligands have been synthesized, characterized, and evaluated for photocatalytic CO2 reduction reaction (CO2-RR). We have shown that the use of a bidentate co-ligand (2,2ʣ-bipyiridine (bpy)) along with a CNC-pincer in ruthenium complexes ([(CNC)RuIIL(bpy)]n+, L is chloride or acetonitrile) resulted in the development of self-sensitized catalysts for photocatalytic CO2-RR under photosensitizer (PS) free conditions. The effect of various donor groups at the 4-position of the central pyridyl ring in CNC-pincer ligand has been evaluated via structure-activity relationships for sensitized photocatalytic CO2-RR in the presence of an external PS using [(CNC)RuIICl(MeCN)2]+ complexes. We have also compared the positional effect for one of the donor group. To further explore the structure-activity relationships, 11 novel ruthenium complexes with the general formula [(CNC)RuIIL(NN)]n+ (NN = diimine ligands, L = chloride or bromide or acetonitrile) were synthesized, characterized, and evaluated for sensitized and self-sensitized photocatalytic CO2-RR. The structures include two CNC-pincer ligands based on imidazole and benzimidazole derived NHCs and three diimine ligands including bpy, 4,4ʣ-dimethyl-2,2ʣ-bipyridine (dmb), and 1,10-phenanthroline. The development of heterogeneous catalysts has also been pursued. Two highly active homogeneous photocatalysts containing CNC-pincer and bpy co-ligand on ruthenium were considered for surface immobilization to develop heterogeneous catalysts with well-defined active sites. Syntheses of ruthenium complexes via bpy ligand modifications are described that can be immobilized onto an inert solid support for surface organometallic chemistry (SOMC). In addition, we have attempted to explore the use of first-row transition metals to develop catalysts for photocatalytic CO2-RR. The development of nickel CNC-pincer complexes for this reduction reaction has been described. We also aimed to synthesized iron-based catalysts and the efforts are described. The use of bulkier wing-tip groups on the CNC-pincer ligands and phosphine co-ligand resulted in the formation of miscellaneous ruthenium complexes.
Author: Scott M. Auerbach Publisher: CRC Press ISBN: 9780203911167 Category : Science Languages : en Pages : 1202
Book Description
The Handbook of Zeolite Science and Technology offers effective analyses ofsalient cases selected expressly for their relevance to current and prospective research. Presenting the principal theoretical and experimental underpinnings of zeolites, this international effort is at once complete and forward-looking, combining fundamental
Author: Leonard R. MacGillivray Publisher: John Wiley & Sons ISBN: 1118931580 Category : Science Languages : en Pages : 1210
Book Description
Metal-Organic Frameworks (MOFs) are crystalline compounds consisting of rigid organic molecules held together and organized by metal ions or clusters. Special interests in these materials arise from the fact that many are highly porous and can be used for storage of small molecules, for example H2 or CO2. Consequently, the materials are ideal candidates for a wide range of applications including gas storage, separation technologies and catalysis. Potential applications include the storage of hydrogen for fuel-cell cars, and the removal and storage of carbon dioxide in sustainable technical processes. MOFs offer the inorganic chemist and materials scientist a wide range of new synthetic possibilities and open the doors to new and exciting basic research. Metal-Organic Frameworks Materials provides a solid basis for the understanding of MOFs and insights into new inorganic materials structures and properties. The volume also reflects progress that has been made in recent years, presenting a wide range of new applications including state-of-the art developments in the promising technology for alternative fuels. The comprehensive volume investigates structures, symmetry, supramolecular chemistry, surface engineering, recognition, properties, and reactions. The content from this book will be added online to the Encyclopedia of Inorganic and Bioinorganic Chemistry: http://www.wileyonlinelibrary.com/ref/eibc
Author: Saravanan Rajendran Publisher: Springer ISBN: 3030045005 Category : Science Languages : en Pages : 310
Book Description
This book describes the role and fundamental aspects of the diverse ranges of nanostructured materials for energy applications in a comprehensive manner. Advanced nanomaterial is an important and interdisciplinary field which includes science and technology. This work thus gives the reader an in depth analysis focussed on particular nanomaterials and systems applicable for technologies such as clean fuel, hydrogen generation, absorption and storage, supercapacitors, battery applications and more. Furthermore, it not only aims to exploit certain nanomaterials for technology transfer, but also exploits a wide knowledge on avenues such as biomass-derived nanomaterials, carbon dioxide conversions into renewable fuel chemicals using nanomaterials. These are the areas with lacunae that demand more research and application.
Author: Jorge Becerra Sanchez
Author: Jorge Becerra Sanchez
Author: Vishnu Nair Gopalakrishnan
Author: Z. Huang
Author: Alejandro Castañeda Flores
Author: Constantinos Dimitrakakis
Author: Sanjit Das
Author: Pooja Ghosh
Author: Scott M. Auerbach
Author: Leonard R. MacGillivray
Author: Saravanan Rajendran