Tesi sul tema "Photocatalysis"
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1
He, Jijiang. "Preparation and photocatalysis of graphite carbon nitride based photocatalysts". Thesis, Curtin University, 2015. http://hdl.handle.net/20.500.11937/521.
Testo completoAbstract (sommario):
The connection between ritual and the interior is interrogated through a theoretical framework integrating Van Gennep’s Rites of Passage Theory and Turner’s Theory of Liminality. A multi-faceted methodological framework is developed from the interrogation of the disciplinary edges of multiple methodologies, addressing the experiential, cultural and subjective dimensions of ritual. This new way of exploring the interior demonstrates how knowledge can be acquired from the body’s immersion in unfolding ritual situations, revealing elements of ritual and interior in relation to one another and the generation of new theories on the interior.
2
Zhou, Ruixin. "SEMICONDUCTOR PHOTOCATALYSIS: MECHANISMS, PHOTOCATALYTIC PERFORMANCES AND LIFETIME OF REDOX CARRIERS". UKnowledge, 2017. http://uknowledge.uky.edu/chemistry_etds/85.
Testo completoAbstract (sommario):
Photocatalytic reactions mediated by semiconductors such as ZnS, TiO2, ZnO, etc. can harvest solar energy into chemical bonds, a process with important prebiotic and environmental chemistry applications. The recycling of CO2 into organic molecules (e.g., formate, methane, and methanol) facilitated by irradiated semiconductors such as colloidal ZnS nanoparticles has been demonstrated. ZnS can also drive prebiotic reactions from the reductive tricarboxylic acid (rTCA) cycle such as the reduction of fumarate to succinate. However, the mechanism of photoreduction by ZnS of the previous reaction has not been understood. Thus, this thesis reports the mechanisms for heterogeneous photocatalytic reductions on ZnS for two model reactions in water with sulfide hole scavenger. First the reduction of CO2 is carried out under variable wavelength of irradiation and proposed to proceed thorough five steps resulting in the exclusive formation of formate. Second the reduction of the double bond of fumaric acid to succinic acid is reported in detail and compared to the previous conversion of CO2 to formic acid. Both reactions are carried out under variable wavelength of irradiation and proposed to proceed thorough one electron transfer at a time. In addition, a new method to measure the bandgap of colloidal ZnS suspended in water is established. Furthermore, the time scales of electron transfer and oxidizing hole loss during irradiation of ZnS for both reactions are reported and interpreted in terms of the Butler-Volmer equation.
The sunlight promoted production of succinate introduced above, provides a connection of this prebiotic chemistry work to explore if central metabolites of the rTCA cycle can catalyze the synthesis of clay minerals. Clay minerals are strong adsorbents that can retain water and polar organic molecules, which facilitate the polymerization of biomolecules and conversion of fatty acid micelles into vesicles under prebiotic conditions relevant to the early Earth. While typical clay formation requires high temperatures and pressures, this process is hypothesized herein to be accelerated by central metabolites. A series of synthesis are designed to last only 20 hours to study the crystallization of sauconite, an Al- and Zn-rich model clay, at low temperature and ambient pressure in the presence of succinate as a catalyst. Succinate promotes the formation of the trioctahedral 2:1 layer silicate at ≥ 75 °C, 6.5 ≤ pH ≤ 14, [succinate] ≥ 0.01 M. Cryogenic and conventional transmission electron microscopies, X-ray diffraction, diffuse reflectance Fourier transformed infrared spectroscopy, and measurements of total surface area and cation exchange capacity are used to study the time evolution during the synthesis of sauconite.
While the studies with ZnS presented above advanced the fundamental understanding of photocatalysis with single semiconductors, the environmental applications of this material appear limited. A common limitation to photocatalysis with single semiconductors is the rapid recombination of photogenerated electron-hole pairs, which reduces significantly the efficiency of the process that in the case of ZnS also suffers from photocorrosion in the presence of air. In order to overcome the fast charge recombination and the limited visible-light absorption of semiconductor photocatalysts, an effective strategy is developed in this work by combining two semiconductors into a nanocomposite. This nanocomposite is solvothermally synthesized creating octahedral cuprous oxide covered with titanium dioxide nanoparticles (Cu2O/TiO2). The nanocomposite exhibits unique surface modifications that provide a heterojunction with a direct Z-scheme for optimal CO2 reduction. The band structure of the nanocomposite is characterized by diffused reflectance UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy. The photoreduction of CO2(g) to CO(g) on the nanocomposite is investigated in the presence water vapor as the hole scavenger that generates the quantifiable hydroxyl radical (). The quantum efficiency of CO production under irradiation at λ ≥ 305 nm with the nanocomposite is 2-times larger than for pure Cu2O. The detection of and XPS analysis contrasting the stability of Cu2O/TiO2 vs Cu2O during irradiation prove that TiO2 prevents the photocorrosion of Cu2O.
Overall, the studies of photocatalytic reductions on single component semiconductors reveal new knowledge needed for developing future photocatalytic application for fuel production, wastewater treatment, reducing air pollution, and driving important prebiotic chemistry reactions. Furthermore, the design of a photocatalyst operating under a Z-scheme mechanism provides a new proof of concept for the design of systems that mimic photosynthesis. Finally, this work also demonstrates how molecules obtained by mineral mediated photochemistry can catalyze clay formation; highlighting the important role that photochemistry may have played for the origin of life on the early Earth and other rocky planets.
3
Plumejeau, Sandrine. "Croissance de TiO₂ en surface de fibres de cellulose pour l'élaboration de filtres photocatalytiques". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT230/document.
Testo completoAbstract (sommario):
La dépollution est aujourd’hui un enjeu majeur pour la protection de l’environnement et un développement durable. Les technologies membranaires et les procédés d’oxydation avancée jouent un rôle de plus en plus important dans le traitement de l'eau que ce soit pour la production d’eau potable que pour le traitement des eaux usées urbaines ou industrielles. La photocatalyse hétérogène est un procédé d’oxydation avancée permettant la génération des espèces très oxydantes comme les radicaux OH•, en présence d’eau et de dioxygène, lors de l’irradiation de certains solides semi-conducteurs au premier rang desquels on retrouve le dioxyde de titane. L’objectif final visé dans cette thèse est le développement de filtres photocatalytiques performants mis en œuvre dans des procédés hybrides couplant séparation et photodégradation. Le mode d’élaboration envisagé pour ces filtres photocatalytiques est basé sur une voie de synthèse en rupture utilisant un polymère biosourcé, la cellulose, à la fois comme réactif (source d’oxygène) et support mécanique pour la croissance de nanoparticules de TiO2 à partir de tétrachlorure de titane. La première partie de la thèse est dédiée à une revue bibliographique qui porte principalement sur les procédés membranaires et hybrides, le dioxyde de titane et ses propriétés photocatalytiques et sur les propriétés chimiques, structurales et microstructurales et l’évolution thermique de la cellulose. Après un descriptif des matériels et méthodes mis en œuvre dans l’étude expérimentale sont d’abord présentés et discutés les résultats obtenus sur la préparation et la caractérisation de poudres purement minérales, à base de TiO2, et de poudres composites TiO2-carbone. L’effet du dopage du TiO2 par différents métaux de transition afin d’améliorer ses propriétés fonctionnelles est ensuite examiné. Une simplification du procédé de synthèse consistant à éliminer tout usage de solvant est exposée dans le chapitre suivant. S’appuyant sur le savoir-faire précédemment acquis en matière de synthèse et sur les performances photocatalytiques préalablement mesurées, le dernier chapitre est consacré aux travaux préliminaires menés sur la préparation de filtres photocatalytiques et sur l’évaluation leurs performances fonctionnellesThe pollution is definitely a major issue for environmental protection and sustainable development. Membrane technologies and advanced oxidation processes play more and more a key-role in the treatment of water both for the production of drinking water and for the treatment of municipal and industrial wastewaters. Heterogeneous photocatalysis is an advanced oxidation process for generating highly oxidizing species such as OH• in the presence of water and dioxygen, under irradiation of some semiconducting solids like titania (TiO2). The targeted objective for this PhD work is the development of efficient photocatalytic filters to be implemented in hybrid processes coupling separation and photodegradation. The innovative route investigated for preparing such photocatalytic filters is based on the use of a bio-based polymer, i.e. the cellulose, both as reactant (oxygen source) and mechanical support for the growth of titania nanoparticles from titanium tetrachloride. The first part of the thesis is dedicated to a literature review mainly focused on membrane and hybrid processes, on titanium dioxide and its photocatalytic properties and on the chemical, structural, microstructural and thermal behaviour of cellulose. After a description of the experimental procedures, the second part of this manuscript is first dedicated to the presentation and the discussion of the experimental results on the preparation and characterization of pure titania powders and of TiO2-carbon composite powders. The effect of titania doping by different transition metals in order to improve its functional properties is then examined. Simplification of the synthesis process by removing any is described in the next chapter. From the previously developed know-how on synthesis and photocatalytic performance, the last chapter is devoted to preliminary work on the preparation of photocatalytic filters and on the assessment of their functional properties
4
Guo, Muyao, e 郭牧遥. "Metal oxide photocatalysis". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50434457.
Testo completoAbstract (sommario):
Photocatalysis has been attracting much research interest because of its wide applications in renewable energy and environmental remediation. Among the photocatalysts, metal oxide semiconductors are the best choice due to distinctive properties, durability and cost effectiveness. However, the mechanisms of photocatalysis are still not entirely clear and the photocatalytic activity of the metal oxide materials needs to be improved. Therefore, this thesis concentrates on the study of the photocatalytic mechanism and the factors affecting the photocatalytic activity.
The photocatalysis of different commercial metal oxide nanoparticles has been studied. Different photocatalytic experiments have been designed to find out the mechanisms of photocatalysis. It is found that the dominant mechanism of photocatalysis is direct charge transfer between metal oxide and organic compounds. Reactive oxygen species, such as hydroxyl radicals also play a minor role in the photocatalysis.
ZnO tetrapods were synthesized by evaporating Zn powder in the flow of Ar gas at high temperature in this study. They exhibit excellent photocatalytic activity. By the comparison between ZnO tetrapods and different ZnO nanoparticles, it is found that the photocatalytic activity of the metal oxide is strongly affected by the native defects, especially by the nonradiative defects.
1D TiO2 nanotubes and ZnO nanorods were synthesized by anodization and hydrothermal growth respectively. ZnO nanorods with alumina and titania shell were prepared by solution-based methods. These structures are interesting as supported catalysts, which is important for practical applications, since it enables simple removal of photocatalyst from treated water. The core shell structures are expected to improve the stability of ZnO. The results also imply that the photocatalytic avtivity of materials is affected by the native defects.
Two different solution based methods hydrothermal growth and electrodeposition to grow CuxO layer were used. The hydrothermal grown CuxO exhibit excellent photocatalytic activity and good photocorrosion resistance. It was also found that the photocatalytic activity of the CuxO prepared by hydrothermal methods can be recovered by simple immersion of the sample into the precursor solution.published_or_final_version
Physics
Master
Master of Philosophy
5
Jackson, S. A. "Intermediates in photocatalysis". Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384288.
Testo completo
6
Qiao, Yu. "Preparation, Characterization, and Evaluation of Photocatalytic Properties of a Novel NaNbO3/Bi2WO6 Heterostructure Photocatalyst for Water Treatment". Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38080.
Testo completoAbstract (sommario):
Semiconductor-based heterogeneous photocatalysis, as one of the advanced oxidation processes that makes use of semiconductors and inexhaustible solar light, has recently been extensively studied and applied to water decontamination. However, due to low light absorption efficiencies and severe electron-hole recombination, modifications on semiconductor structures are required in order to enhance their photocatalytic performance. Heterogeneous photocatalyst composites, taking advantage of the improved light absorption efficiency as well as the facilitated electron-hole separation at the interface between different semiconductors, have been proven to be a promising strategy. In this study, novel NaNbO3/Bi2WO6 photocatalyst composites with a type-II heterogeneous alignment were successfully prepared via a facile wet impregnation method. The as-prepared photocatalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-Vis spectroscopy (DRS), photocurrent (PC) and electrochemical impedance spectroscopy (EIS) analyses. The 30 wt% NaNbO3/Bi2WO6 composite exhibited the best performance for degrading an RhB (rhodamine B) aqueous solution under visible light irradiation (λ > 410 nm), which was ca. 40 times and ca. 2.5 times that of the pristine NaNbO3 and Bi2WO6, respectively. The improved photocatalytic activity may be attributed to the enhanced electron-hole separation efficiency in Bi2WO6 with the assistance of NaNbO_3, as well as the dye-sensitization effect of RhB itself. Radical quenching experiments revealed that h+ played the predominant role, and O2•- functioned as well to some degree. The produced intermediates during the reaction and RhB degradation pathway were speculated and investigated as well. The excellent stability and reusability were verified by repetitively running for five times. Based on experimental results, a plausible functioning mechanism was proposed. Effects of several operation parameters on the catalyst performance including initial RhB concentration, catalyst dosage, reaction temperature and initial pH were also discussed. This study provides solid evidence for NaNbO3 to be a promising candidate for photocatalysis and gives out a novel photocatalytic mechanism of Bi2WO6-based type-II heterostructures.
7
Yatmaz, Huseyin Cengiz. "Photocatalysis of organic effluents". Thesis, University of Newcastle Upon Tyne, 1993. http://hdl.handle.net/10443/271.
Testo completoAbstract (sommario):
Heterogeneous photocatalytic oxidation is a relatively new technology for the destruction of toxic organic substances in water and so far has concentrated on reaction mechanisms and kinetics, but the engineering side was hardly touched. In this study a detailed investigation for suitable reactor design has been carried out using three different reactor types. An annular photoreactor was used with two different lamps with different intensities; low pressure and medium pressure mercury lamps. Two types of Ti02 powder catalysts Degussa P-25 and Tioxide PCi were used as slurry solutions and Degussa P-25 was found more photocatalytically active than the other. Two main organic reactants salicylic acid and 4-chlorophenol were studied to assess the light intensity effect. Although better reaction rates were achieved with the higher intensity medium pressure lamp, quantum yield results showed that low pressure lamp photons were utiised more effectively. The falling film reactor (FFR) was used to increase the light intensity utilisation with the stronger medium pressure lamp and using the same reactants in slurries catalysts Degussa P-25 gave superior results to those in annular reactor. Because of the thin film characteristics, FFR provided good oxygen transfer at the film/air interface. A commercial supported catalyst system as a fibre glass gauze was also used inside the reactor and was found as effective as slurry systems. In order to improve the thin film characteristics and combine these with an immobiised catalyst, a spinning disc reactor (SDR) with catalyst coated borosilicate disc was used to degrade aqueous solutions of 4- chlorophenol and salicylic acid. It was found that the efficiency of the photocatalyst process was dependent upon the type of UV source used. Lamps supplying shorter wavelength UV radiation were found to be more efficient than those whose emissions lay mainly in the near UV region. The method used to coat the disc of the SDR does not appear to meet its operational requirements.
8
O'Rourke, Christopher. "Photocatalysis for organic synthesis". Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675420.
Testo completoAbstract (sommario):
A wide range of commercially available self-cleaning materials/products are now available, from architectural materials, such as; glass, paint, plastics, and concrete, to water and air purification systems. These products exploit the destructive oxidative nature of SPC to purify air and water. In contrast, this thesis introduces the less well studied use of SPC to mediate the synthesis of a range of useful organic species, and aims to develop a fast screening process for monitoring such reactions to aid future developments in SPC mediated organic synthesis. It is demonstrated that NMR is a very effective way to monitor SPC mediated organic reactions. By coating the inside of an NMR tube with a sol-gel titania film, and performing SPC reactions in-situ, inside a sealed NMR tube on a 1 mL scale, the need for sample-taking and pre-treatment is negated. The small scale also allows for much faster reaction times. For example, it is shown for the SPC oxidation of toluene, that the use of this NMR/sol-gel titania method is ca. 10 times faster than the more conventional large scale (100 mL) reaction utilising a titania dispersion, whilst still providing similar product yields, thus, demonstrating a new rapid screening method for SPC mediated organic synthesis reactions. Using the new fast screening NMR tube method, the SPC C-C coupling of phenoxyacetic acid (PAA) with N-methylmaleimide (NMI) to produce adduct and cyclic products in yields up to 67% and 15% respectively after only 15 min of UVA irradiation was assessed in detail. Despite the well-known photochemical feature of NMI to form dimers efficiently, the background photochemistry and photocatalysis associated with the individual reactants are shown to be minimal due to the faster SPC kinetics for the coupling reaction. Acrylamide (ACM) was also used in the SPC C-C coupling with PAA, gaving rise to only one product, 4-phenoxybutanamide, in high yields (78%). This efficient reaction was then used to assess the robustness and reusability of the titania coated NMR tubes.
9
Cornu, Catherine J. G. Hoffmann Michael R. "Photocatalysis under periodic illumination". Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechETD:etd-05082006-143046.
Testo completo
10
Mercer, Sarah M. "Heterogeneous photocatalysis: Design and experimental characterization of a new photocatalytic reactor for wastewater treatment". Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27393.
Testo completoAbstract (sommario):
The objective of this study is to promote photocatalytic wastewater treatment by proposing a reactor design that employs a catalyst-coated, rotating, corrugated drum to increase the surface area, induce agitation and promote reactant and photon transfer to the surface. Corrugation profiles with surface areas ranging from 405 cm2 to 3650 cm2 were considered---the addition of corrugations improved the phenol degradation rate by up to 200%. Based on an analysis of rotational speed and initial pollutant concentration, the reaction was found to be limited by the kinetics at 20 ppm and 40 ppm, but limited by phenol transfer to the reaction sites at 5 ppm. Finally, Langmuir-Hinshelwood kinetics was applicable with an average phenol adsorption coefficient of 0.120 L/mg and an increasing overall reaction rate constant with surface area. Further studies are necessary for the industrial use of such a reactor design including treatment of wastewater with varying characteristics, reactor design scaling and the applicability of this design for solar-activated applications.
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Tran, Duc Trung. "Elaboration et mise en œuvre de membranes composites polymère-TiO2 faiblement colmatantes". Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTG023.
Testo completoAbstract (sommario):
Cette thèse porte sur l’élaboration et l’étude des performances de membranes d’ultrafiltration PVDF-TiO2 possédant des propriétés anti-colmatantes et photo-induites. La membrane est obtenue par application de la méthode de séparation de phases induite par un non-solvant sur un collodion de polyfuorure de vinylidène au sein duquel ont été incorporées des nanoparticules de TiO2. Il est montré : i) que la presence des nanoparticules de TiO2 les propriétés membranaires, et notamment le flux de perméat, par rapport à la membrane PVDF ; ii) que l’augmentation de la température de préparation de la membrane permettait de modifier la structure membranaire, en passant d’une morphologie constituée principalement de macrovides (dite en “doigts de gants”) à des températures basses à une morphologie spongieuse, contenant des pores de plus petite taille, à température élevée. Au-delà de la structure membranaire, des propriétés telles que la perméabilité, la porosité, la résistance mécanique, la cristallinité et les propriétés thermiques sont également influences par les changements de température de formation. Lorsque les membranes PVDF-TiO2 sont mises en oeuvre en mode photo-filtration (c.-à-d. filtration avec irradiation ultraviolette (UV) continue sur la membrane), le flux à l’eau pure de la membrane PVDF-TiO2 est encore augmenté, du fait du phénomène d’hydrophilicité photo-induite des nanoparticules de TiO2. Des premières estimations suggèrent que la photo-filtration par les membranes PVDF-TiO2 serait une économiquement rentable, car le gain en termes de filtration et qualité d’eau l’emporterait sur le cout énergétique induit par l’irradiation UV. En outre, l’efficacité de la photo-filtration a été évaluée avec des solutions d’alimentation synthétiques contenant des composés inorganiques et organiques représentatifs des eaux de surface. Il a été montré que si la plupart des ions inorganiques communément rencontrés dans l’eau potable n’ont aucun effet sur l’efficacité de la photo-filtration, la coexistence de Cu2+ et HCO3- dans l’eau d’alimentation entraîne un colmatage inorganique sévère qui inhibe le phénomène hydrophilicité photoinduite. En outre, la membrane PVDF-TiO2 présente également des flux plus élevés et une activité photocatalytique lors de la photo-filtration de solutions contenant des matières colmatantes organiques comme les acides humiques ou l’alginate de sodium. En conclusion, la membrane composite PVDF-TiO2 a démontré des propriétés et des performances significativement améliorées par rapport à la membrane PVDF, a fortioti lorsqu’elle est mise en oeuvre dans un système de photo-filtration sous irradiation UV. Ainsi, ce sont des matériaux prometteurs pour des applications membranaires en traitement de l’eauThis thesis deals with the elaboration and performance of a specific type of ultrafiltration membrane with anti-fouling and photo-induced properties, the PVDF-TiO2 composite membrane. The membrane was fabricated via the nonsolvent-induced phase separation method by incorporating titanium dioxide (TiO2) nanoparticles into the polyvinylidene fluoride (PVDF) polymer matrix. The TiO2 nanoparticles played a significant role in facilitating the membrane formation process and improving the composite membrane properties compared to the neat PVDF membrane. It was demonstrated that, by changing the membrane preparation temperature, the membrane structure could be affected dramatically, notably the morphological dominance of finger-like macrovoids at lower temperatures and their diminution in both size and number when temperature increased. Other membrane properties also saw systematic transitions with changes in formation temperature, as characterized by permeability, porosity, mechanical strength, crystallinity, and thermal properties. In terms of performance, the PVDF-TiO2 membrane exhibited superior permeate flux compared to the neat PVDF membrane. More importantly, when being operated in photo-filtration mode (i.e. filtration with continuous ultraviolet (UV) irradiation on the membrane), the pure water flux of PVDF-TiO2 membrane could be further increased, thanks to the enhanced hydrophilicity of the membrane, which comes from the photo-induced hydrophilicity phenomenon of TiO2. Preliminary estimations suggest that photo-filtration is a cost-effective method, as the benefit from enhanced water output outweighs the extra energy demand for UV irradiation. Furthermore, the efficiency of photo-filtration was evaluated with synthetic feed solutions containing inorganic and organic contents representative in surface water. It was identified that, while most of the common inorganic ions in drinking water had no effects on photo-filtration efficiency, the coexistence of Cu2+ and HCO3- in the feed led to severe inorganic fouling and inhibited the photo-induced hydrophilicity phenomenon. Besides, the PVDF-TiO2 membrane also showed its stronger flux performance and photocatalytic activity during photo-filtration of solutions containing organic foulants like humic acids or sodium alginate. In conclusion, the PVDF-TiO2 composite membrane exhibited much improved properties and performance compared to the neat PVDF membrane, and even stronger performance when operated in photo-filtration mode. Thus, it is a promising candidate to be used in membrane-based applications for water treatment
12
Bai, Xiaofei. "Effet de taille et du dopage sur la structure, les transitions et les propriétés optiques de particules du multiferroïque BiFeO₃ pour des applications photocatalytiques". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC013/document.
Testo completoAbstract (sommario):
Ce travail de thèse expérimentale a été consacré à la synthèse par des méthodes de chimie par voie humide de nanoparticules à base du multiferroïque BiFeO3 et à leur caractérisation, avec comme objectif finale des applications photocatalytiques. Ce matériau présente une bande interdite, avec un gap de 2.6eV, qui permet la photo-génération de porteurs de charges dans le visible faisant ainsi de BiFeO3 un système intéressant pour des processus photo-induits. Ce travail s’est en particulier focalisé à caractériser les propriétés de nanoparticules à base de BiFeO3 en vue de comprendre l’effet de ses propriétés sur leur potentiel dans des applications liées à la photocatalyse. Tout d’abord, l’étude des effets de taille sur les propriétés structurales, de transitions de phase, et physico-chimiques des particules a été réalisée, en gardant comme principal objectif de découpler les propriétés liées à la surface de celles du massif/cœur de la particule. Pour cela, une maîtrise et une optimisation des procédés de synthèse de particules aux échelles nano- et micro-micrométriques de BiFeO3 a été nécessaire pour obtenir des composés de taille variable et de très bonne qualité cristalline. Malgré la diminution de la taille des particules, on constate que, grâce au contrôle de paramètres de synthèse, nos nanoparticules présentent des propriétés très proches à celles du massif de BiFeO3, gardant la structure rhomboédrique R3c avec des faibles effets de contrainte. Afin de contrôler indirectement par le dopage les propriétés optiques des composés à base de BiFeO3, on a réussi à réaliser un dopage très homogène en La3+, et un dopage partiel en Ca2+, sur le site de Bi3+. Les propriétés optiques des nanoparticules et leurs applications dans les premières expériences photocatalytiques sur la dégradation du colorant rhodamine B ont montré la complexité de la physico-chimie de leur surface et du processus d’interaction lumière-particule. Après analyse des données d’absorbance optique en fonction de la taille de nanoparticules, on observe que la bande interdite déduite pour ces différentes particules n’est pas le facteur prédominant sur les performances photocatalytiques. D’autres facteurs ont pu être identifiés comme étant à l’origine de la localisation de charges photo-générées, tels que des états de surface liés à une fine couche de peau ou skin layer sur les nanoparticules, présentant des défauts structuraux, une réduction de l’état d’oxydation du Fe3+ vers le Fe2+ et la stabilisation d’autres adsorbats, tels que FeOOH ; tous ces facteurs peuvent contribuer au changement dans les performances photocatalytiques. Les résultats photocatalytiques restent très encourageants pour poursuivre les études de nanoparticules à base de BiFeO3, montrant une dégradation de la rhodamine B à 50% au bout de 4h de réaction photocatalytique pour certaines des nanoparticules étudiéesThis experimental PhD work has been dedicated to the synthesis, by wet chemistry methods, and characterization of nanoparticles based on multiferroic BiFeO3, with the aim of using them for photocatalytic applications. This material presents a bandgap of 2.6eV, which allows the charge carrier photoexcitation in the visible range, making BiFeO3 a very interesting system for photoinduced processes. This thesis has been particularly focused on characterizing the properties of BiFeO3 nanoparticles in view of understanding the relationship of their properties on their potential use for photocatalytic applications. First of all, the topic of the size effect on the structural properties, phase transitions, and physics and chemistry of the particles has been developed, keeping as first aim to separate the properties related to the surface from those arising from the bulk/core of the particle. To do so, the mastering and optimization of the synthesis processes of BiFeO3 particles at the nano and microscale were needed, to finally obtain different size compounds with high crystalline quality. Despite the size reduction of the particles, we notice that, thanks to the control of the synthesis process, our BiFeO3 nanoparticles present properties very close to those of the bulk BiFeO3 material, keeping the rhombohedral structure R3c with weak strain effects. In order to indirectly tune the optical properties exploiting the doping, we have succeeded in realizing a homogenous La3+ doping, and a partial Ca2+ doping, on the Bi3+ site. The optical properties of the nanoparticles and their use on the first photocatalytic experiments for degrading rhodamine B dye have shown the complexity of the physics and chemistry phenomena at their surface and of the light-particle processes. After analyzing optical absorbance data as a function of the particle size, we observe that the deduced bandgap for different particles is not the main parameter directing the photocatalytic performances. Other factors have been identified to be at the origin of the localization of the photoexcited charges, as the surface states linked to the skin layer of the nanoparticles, depicting structural defects, a reduction of the oxidation state of Fe3+ towards Fe2+ and the stabilization of other adsorbates, such as FeOOH; all these parameters may contribute to the change on the photocatalytic performances. The photocatalytic results are very encouraging, motivating to continue the study of BiFeO3 based nanoparticles, though depicting a 50% rhodamine B degradation after 4h of photocatalytic reaction using some of the present nanoparticles
13
Wang, Fan. "Visible light photocatalysis with supported metal nanoparticles for organic synthesis". Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/103567/1/Fan_Wang_Thesis.pdf.
Testo completoAbstract (sommario):
This project was a step forward in developing new effective photocatalysts for fine organic synthesis under visible light irradiation. These kind of new photocatalysts are able to facilitate reaction rates by using visible light under moderate reaction conditions through a green, economical and environmentally friendly pathway. This thesis investigated the catalyst synthesis, characterization and the application in organic reactions with high activity and selectivity. The discovery of these new metal nanoparticle photocatalysts may inspire further studies on other efficient photocatalysts and enhance the potential to utilize sunlight via a controlled and environmentally friendly process.
14
Ran, Rong. "Preparation and Optimization of Novel Visible-Light-Active Photocatalysts for Waste-Water Treatment". Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34152.
Testo completoAbstract (sommario):
Photocatalysis is a series of advanced light-induced redox reaction processes resulting in the degradation and mineralization of organic pollutants in the presence of oxygen and water. Due to their capability to destroy contaminants under mild conditions, photocatalytic processes have attracted considerable attention in the field of waste-water treatment. However, photocatalytic reactions using the traditional TiO2 photocatalyst suffer from low energy efficiencies under solar irradiation. This low efficiency in the utilization of solar energy lies in its incapability in absorbing visible lights and also the high recombination rate of photo-excited species in photocatalysts. In addition, difficulties in the separation of fluids from micro- or nano-scale catalysts in large scale systems substantially impact cost efficiency in practice. In this thesis, strategies are explored which address these issues in order to improve the feasibility of solar photocatalysis. Two branches of photocatalytic transition metal-oxide semiconductor materials are investigated, namely bismuth-based and silver-based multi-phase heterogeneous photocatalysts. This research is focused on the design of visible-light-active metal-oxide photocatalysts to increase the absorption of visible light and to decrease the rates of electron-hole recombination, resulting in a high photocatalytic efficiency in regards to the degradation of organic pollutants. BiVO4 powder, synthesized from freshly made potassium metavanadate was prepared via hydrothermal treatment, characterized and experimentally investigated for the degradation of rhodamine B under visible light irradiation. The crystal structures and the specific surface areas of the composites, based on BiVO4 single phase crystal structures, are discussed. A multi-phase silver species (Ag2O/Ag3VO4/Ag4V2O7) photocatalyst was synthesized by adjusting the molar ratio of silver to vanadium (Ag to V) via hydrothermal method. The stabilities of as-prepared silver species composites regarding crystal structural changes due to photocatalytic reactions are investigated. Multi-phase silver species composites assisted with graphene oxide (GO-Ag2O/Ag3VO4/AgVO3) were synthesized at room temperature, and exhibited high visible-light photocatalytic activities regarding the degradation of model organic pollutants. The effect of graphene oxide addition on the photoactivity and on the photocorrosion of silver species composites under VLI is explored. The synergistic roles of each individual phase incorporated into the multi-phase composites are discussed regarding the photocatalytic performance.
15
Altomare, M. "TOWARDS THE PHOTOCATALYTIC PRODUCTION OF SOLAR FUELS - NANOSTRUCTURED TITANIUM DIOXIDE FOR PHOTOCATALYSIS & PHOTO-ELECTROCHEMISTRY". Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/229553.
Testo completoAbstract (sommario):
In spite of many efforts given during the last decades to find new alternative photocatalytic materials, titanium dioxide (TiO2) still represents the most widely employed semiconductor for photocatalytic applications, being photoactive, cheap, easily available, non-toxic, inert and, most of all, chemically stable. However, although exhibiting a powerful combination of extraordinary and attractive physico-chemical properties, it suffers from some issues, common to all semiconductors, related to the dynamic of the charge carriers. Precisely, trapping and recombination of valence band holes and conduction band electrons occur at a certain extent, anyway resulting in a drop of the process efficiency. Therefore, in view of limiting these detrimental phenomena, the charge transfer and the electric conductivity of a semiconductor can be enhanced, thus leading to an overall improvement of the photocatalyst performance.
In the first part of the work, homemade and commercial TiO2 powders were studied as photocatalysts for different applications, including the liquid-phase photocatalytic oxidation of ammonia and formic acid, and the H2 production through photocatalytic reforming of water-methanol vapors. In this context, a dopant (NH4F) was used during the sol-gel synthesis of the semiconductor to stabilize the formation of the TiO2 anatase phase (typically more active than rutile TiO2 because of its higher electron mobility), especially when crystallization of the amorphous oxides was performed at high temperature (700 ˚C). Furthermore, the effects induced by noble metal nanoparticles deposition on TiO2 anatase powders were also investigated. In situ electron spin resonance spectroscopy was employed to determine the amount of electrons and holes trapping centers formed under irradiation, in the absence and in the presence of noble metal co-catalysts at the surface of TiO2, hence assessing also the ability of Au and Pt nanoparticles in trapping conduction band electrons. The results were of great usefulness not only to interpret the different H2 production rates but also to understand some mechanistic aspects concerning the selectivity towards the different oxidation products in the methanol photo-steam reforming reaction.
In the second part of the work, the nanostructuring of the semiconductor was explored by fabricating TiO2 nanotube arrays through electrochemical anodization. The anodic oxides were employed for both photocatalytic and photo-electrochemical H2 production. In view of large-scale application, the anodization approach was studied on wide Ti substrate surfaces, in order to assess the feasibility of the scale up. Moreover, TiO2 nanotubes were also grown on Ti-based alloys. When fabricating the nanotubes under optimized conditions on Ti-Ta alloys, highly photoactive Ta-doped TiO2 nanotubes were obtained, exhibiting superior water splitting ability. When anodizing Ti-Au alloys, the TiO2 nanotubes resulted decorated with Au nanoclusters. These Au-decorated TiO2 nanotube arrays were used as efficient photocatalyst for H2 production from ethanol-water solutions. Finally, the fabrication of short TiO2 nanotube layers exhibiting an unprecedented level of self-ordering was achieved through an innovative anodization approach. The highly ordered topography allowed the subsequent self-ordering dewetting of Au, leading to Au nanoparticles of controllable size and distribution. These short, Au nanoparticles-filled TiO2 nanotubes exhibited advanced photoactivity ascribed to their reaction vessel-like geometry, fulfilling the requirements in terms of solid state charge carriers diffusion and liquid phase diffusion of oxidizing radicals.
16
MacDonald, Grant. "Mathematical modelling of semiconductor photocatalysis". Thesis, University of Strathclyde, 2016. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27029.
Testo completoAbstract (sommario):
Semiconductor photocatalysis can be extremely effective in the complete mineralisation of hundreds of organic materials and has been utilised in various different commercial systems, for example, self-cleaning glass, purification of water, the purification of air, sterilisation/disinfection and detecting oxygen in food packaging. The aim of this thesis is to further the understanding of semiconductor photocatalysis using mathematical models. One of the main issues considered is the applicability of assuming that reaction intermediates remain in a steady-state throughout the majority of any reactions taking place. We show that this assumption is not always valid. First, we consider an intelligent ink that is used to test the effectiveness of self-cleaning glass. The system is modelled by a diffusion equation for the transport of dye molecules in the film coupled to an ordinary differential equation describing the photocatalytic reaction taking place at the glass surface. A finite difference method is introduced to solve the equations arising from the model. We are able to show that the proposed model can replicate experimental results well. The model also offers an explanation as to why the initial reaction rate is dependant on film thickness for several different reaction regimes considered. Second, we consider models motivated by systems where photocatalytic reactions take place throughout the domain as opposed to exclusively at domain boundaries. We present a numerical method to solve such systems, and based on informal experimental results, explain the reasons behind the initial reaction rate being dependent on the size of the domain. Third, we consider four previously published models based on the removal of organic pollutants using semiconductor photocatalysis. We introduce more general mathematical models and demonstrate that by doing so there are a wider rangeof systems that the models can be applied to. One model involves an expanding domain and we present a moving mesh finite difference method that is used to solve such systems. Fourth, we propose a moving mesh finite element method for coupled bulk-surface problems in two-dimensional time-dependant domains. These problems are motivated by a system where semiconductor photocatalysis is used to destroy organic dirt across a domain which is increasing in size. Finally, we show how to determine the colour of a substance based on its absorbance spectrum. By comparing predictions made from experimental data to published photographs we are able to demonstrate that we can accurately predict the colour of a substance.
17
Davies, R. H. "Semiconductor photocatalysis for water purification". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636399.
Testo completoAbstract (sommario):
Although many aspects of the semiconductor photocatalysed mineralisation of water contaminants have been studied by researchers over the past decade, there are still certain areas which need further clarification, if the technique is to be used as an alternative to the presently available methods of water purification. It was the objective of the work in this thesis to provide further understanding of some of these remaining areas. One of the greatest inducements for the introduction of the technique of semiconductor photocatalysed pollutant mineralisation, in preference to the currently available technology, would be an efficiency advantage. The work in Chapter 3, studies the effect of many reaction variables (e.g. T, pH, [TiO2]) in order to provide rate enhancements and therefore further efficiency of the technique. In Chapter 4 the model pollutant, 4-chlorophenol, is used to illustrate the role of activation energies in semiconductor photocatalysed mineralisation reactions, an area which has been largely ignored by researchers in this field to date. In order to speed up the process of reactor designs for commercial semiconductor photocatalysis reactors, there was a need for a predictive kinetic model, to provide information on individual pollutant mineralisation rates, under certain reaction conditions. Chapter 5 outlines a kinetic model which is able to accurately model the mineralisation of various pollutants and can also be used as a predictive tool for non-standard conditions. Chapter 6 enhances this work, to provide a model capable of modelling further pollutant systems, previously unable to be modelled. The technique of semiconductor photocatalysed pollutant mineralisation, will only become a plausible alternative to the currently available technology, if it can be scaled up from the batch reactor level. The work in Chapter 7 aims to provide scale up of the batch system used in Chapter 3 from 2.5 ml to 101.
18
Coleman, Heather Margaret. "Photocatalysis of oestrogens in water". Thesis, University of Ulster, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342532.
Testo completo
19
Mohd, Ghazi Tinia Idaty. "Heterogeneous photocatalysis for chemicals manufacture". Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614672.
Testo completo
20
Crow, Matthew. "Environmental remediation and semiconductor photocatalysis". Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=12837.
Testo completo
21
Beheshtaein, Setareh. "Photocatalysis on a microfluidic reactor". Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10108187.
Testo completoAbstract (sommario):
The photocatalytic reaction has been integrated as a developing technology for various applications such as air and water remediation, and self-cleaning surfaces. The photocatalysis is an emerging pathway of heterogeneous photocatalysis and physical chemistry. In heterogeneous photocatalysis, semiconductor compounds, mainly TiO2, ZnO, CdS, and WO3, have been utilized especially for water treatment and contaminant degradation. Various pollutants, such as aromatic compounds, dyes and surface active agents, can be degraded with photocatalytic techniques. Ultraviolet light and visible light are the most important sources of radiation to conduct photocatalytic reactions.
In this study, we have developed a combined method using microfluidics and photocatalysis for wastewater treatment. This technique represents a promising solution for contaminant degradation that has advantages such as continuous operation, large surface area to volume ratio, rapid response, and fine flow control. The experiment was conducted by exposing samples to UV light with methylene blue as the model pollutant and titanium dioxide (TiO2) as the catalyst. The degradation of methylene blue was monitored with spectrophotometry. The effects of variables, such as residence time, chip thickness and intensity have been investigated. The photocatalytic degradation has been determined to be a pseudo-first-order reaction with a rate constant (0.18 C C0.334) related to catalyst concentration. Once optimized, this system could be scaled out to process wastewater at a larger scale.
22
Ye, Xuejun. "Selected topics on VOC photocatalysis". online access from Digital Dissertation Consortium, 2003. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?3141458.
Testo completo
23
Wilson, Gregory J. "Photocatalysis with a heterosupramolecular assembly". Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16290/1/Gregory_Wilson_Thesis.pdf.
Testo completoAbstract (sommario):
Supramolecular chemistry has asserted itself as a significant multidisciplinary field concerned with molecular effects afforded through non-covalent molecular interactions. The increased interest in the literature towards nanoscale devices, through modulation of molecular function, has seen the renaissance of supramolecular chemistry as function progresses from solution to surface. Heterosupramolecular chemistry follows the architectural principles of supramolecular chemistry and embraces both covalent and non-covalent interactions of condensed phase surfaces and molecular components.
A modular approach to device architecture was applied as a novel method of performing photocatalysis under visible light illumination. The application of heterosupramolecular assembly to the design of photoelectrochemical cells capable of visible light induced charge separation allowed the study of interfacial processes by means of electrochemical observations.
Preparation of a series of supramolecular components was undertaken as specific molecular species within a photochemical system. Starting from a synthesised bidentate ligand that incorporated an acidic functional group, 4,4'-bis(methyl)phosphonate-2,2'-bipyridine (dmpbpy) as its ethyl ester, was chelated to give the surface sensitisers, bis-(2,2'-bipyridine)-(4,4'-bis(methyl)phosphonato-2,2'-bipyridine)ruthenium(II) dichloride ([Ru(bpy)2(dmpbpy)]Cl2) and cis-bis-(4,4'-bis-(methyl)phosphonato-2,2'-bipyridine)(2,2'-bipyridine)ruthenium(II) dichloride ([Ru(dmpbpy)2(bpy)]Cl2). An electron relay moiety with an acidic functional group, 1-ethyl-1'-(2-phosphonoethyl)-4,4'-bipyridinium dichloride (EVP), was also prepared using a procedure developed by the candidate.
The electronic properties of the prepared photosensitisers were examined by theoretical quantum chemical TD-DFT calculations on the molecular structures and singlet excitations were discussed in relation to experimental data. This identified that the lowest lying LUMO states were consistently occupied by 2,2'-bipyridine (bpy) and this was speculated to be a factor affecting quantum injection yields.
The effect of microwave modification of colloidal TiO2 suspensions under extended periods of treatment was investigated. Nanoparticles of TiO2 were compared and contrast to similar convection hydrothermally treated TiO2 and a commercial titania product, namely Degussa P25, both of which are utilised in device fabrication. The investigation identified that extended periods of microwave hydrothermal treatment do not greatly enhance the crystallinity and primary grain size of TiO2.
The heterosupramolecular assembly of a multi-component photochemical system was constructed from prepared molecular and condensed phase components. It was demonstrated that this device was capable of inducing a photochemical reaction in H2O under irradiation with > 420 nm in the absence of an organic electron donor. Interpretation of the photocurrents obtained from this assembly provided understanding of photochemical reactions under low light intensities. Optimised conditions for the photochemical reaction was determined to be pH = 5 and illumination yielded = 0.0036% with an apparent quantum yield (AQY) = 1.6%.
Photocatalytic decomposition of organic compounds in a dye-sensitised photoelectrocatalytic cell was investigated for the complete mineralisation of EDTA into CO2, H2 and simple amines and interpreted through photocurrent observations. This was extended to a broad range of organic compounds of various solution concentrations as a simulated industrial waste stream. Photooxidation gave unique photocurrent-time profiles which identified two distinct interfacial processes by mathematical treatment of photocurrent transients with a kinetic model. Kinetic parameters were proposed as a factor for qualitative discrimination of the organic compounds.
The implications of these results for heterogeneous catalysis were discussed and the formation of Host-Guest complexes as a method of molecular sensing and as specific photocatalytic receptors was proposed.
24
Wilson, Gregory J. "Photocatalysis with a Heterosupramolecular Assembly". Queensland University of Technology, 2006. http://eprints.qut.edu.au/16290/.
Testo completoAbstract (sommario):
Supramolecular chemistry has asserted itself as a significant multidisciplinary field concerned with molecular effects afforded through non-covalent molecular interactions. The increased interest in the literature towards nanoscale devices, through modulation of molecular function, has seen the renaissance of supramolecular chemistry as function progresses from solution to surface. Heterosupramolecular chemistry follows the architectural principles of supramolecular chemistry and embraces both covalent and non-covalent interactions of condensed phase surfaces and molecular components. A modular approach to device architecture was applied as a novel method of performing photocatalysis under visible light illumination. The application of heterosupramolecular assembly to the design of photoelectrochemical cells capable of visible light induced charge separation allowed the study of interfacial processes by means of electrochemical observations. Preparation of a series of supramolecular components was undertaken as specific molecular species within a photochemical system. Starting from a synthesised bidentate ligand that incorporated an acidic functional group, 4,4'-bis(methyl)phosphonate-2,2'-bipyridine (dmpbpy) as its ethyl ester, was chelated to give the surface sensitisers, bis-(2,2'-bipyridine)-(4,4'-bis(methyl)phosphonato-2,2'-bipyridine)ruthenium(II) dichloride ([Ru(bpy)2(dmpbpy)]Cl2) and cis-bis-(4,4'-bis-(methyl)phosphonato-2,2'-bipyridine)(2,2'-bipyridine)ruthenium(II) dichloride ([Ru(dmpbpy)2(bpy)]Cl2). An electron relay moiety with an acidic functional group, 1-ethyl-1'-(2-phosphonoethyl)-4,4'-bipyridinium dichloride (EVP), was also prepared using a procedure developed by the candidate. The electronic properties of the prepared photosensitisers were examined by theoretical quantum chemical TD-DFT calculations on the molecular structures and singlet excitations were discussed in relation to experimental data. This identified that the lowest lying LUMO states were consistently occupied by 2,2'-bipyridine (bpy) and this was speculated to be a factor affecting quantum injection yields. The effect of microwave modification of colloidal TiO2 suspensions under extended periods of treatment was investigated. Nanoparticles of TiO2 were compared and contrast to similar convection hydrothermally treated TiO2 and a commercial titania product, namely Degussa P25, both of which are utilised in device fabrication. The investigation identified that extended periods of microwave hydrothermal treatment do not greatly enhance the crystallinity and primary grain size of TiO2. The heterosupramolecular assembly of a multi-component photochemical system was constructed from prepared molecular and condensed phase components. It was demonstrated that this device was capable of inducing a photochemical reaction in H2O under irradiation with > 420 nm in the absence of an organic electron donor. Interpretation of the photocurrents obtained from this assembly provided understanding of photochemical reactions under low light intensities. Optimised conditions for the photochemical reaction was determined to be pH = 5 and illumination yielded = 0.0036% with an apparent quantum yield (AQY) = 1.6%. Photocatalytic decomposition of organic compounds in a dye-sensitised photoelectrocatalytic cell was investigated for the complete mineralisation of EDTA into CO2, H2 and simple amines and interpreted through photocurrent observations. This was extended to a broad range of organic compounds of various solution concentrations as a simulated industrial waste stream. Photooxidation gave unique photocurrent-time profiles which identified two distinct interfacial processes by mathematical treatment of photocurrent transients with a kinetic model. Kinetic parameters were proposed as a factor for qualitative discrimination of the organic compounds. The implications of these results for heterogeneous catalysis were discussed and the formation of Host-Guest complexes as a method of molecular sensing and as specific photocatalytic receptors was proposed.
25
Purohit, Bhagyesh. "Precursors-guided synthesis of upconverting nanomaterials for near-infrared driven photocatalysis". Electronic Thesis or Diss., Lyon, 2021. https://n2t.net/ark:/47881/m6sn08q4.
Testo completoAbstract (sommario):
L'utilisation de l'énergie solaire pour résoudre des problèmes environnementaux tels que la détoxification de l'eau, la purification de l'air et la production d'hydrogène a suscité un grand intérêt de la part de la communauté scientifique au cours des deux dernières décennies. La photocatalyse solaire est une piste intéressante pour cibler toutes ces questions environnementales. Actuellement, les technologies ne permettent pas encore d'utiliser efficacement une partie importante du spectre solaire, à savoir l'infrarouge, qui correspond à près de ~48 % du spectre solaire total. Cette thèse vise à préparer des matériaux nanocomposites qui utilisent ces photons solaires à faible énergie en les convertissant en photons UV et visibles à haute énergie et en les utilisant ensuite pour la photocatalyse classique. Pour y parvenir, l'accent a été mis sur deux aspects majeurs de la préparation de ce photocatalyseur modifié. Premièrement, la synthèse de matériaux qui pourraient convertir efficacement les photons actuellement inutilisés et deuxièmement, la préparation de leur composite avec TiO2, le photocatalyseur le plus largement utilisé. Cette thèse de doctorat se concentre sur une approche basée sur l’ « upconversion » afin d’étendre la gamme d'utilisation du spectre solaire. Pour atteindre cet objectif, deux stratégies d’optimisation ont été abordée. L’'optimisation du rendement quantique des nanoparticules à upconversion en utilisant de nouveaux précurseurs anhydres et, la préparation de photo-catalyseur nanocomposite UCNPs-TiO2 en utilisant des métallogels et/ou des structures coeur-coquille. Pour finir nous testons l’objectif de l'utilisation des photons solaires infrarouges à faible énergie en réalisant une photocatalyse sous irradiation IR uniquement en utilisant la plate-forme développée dans ce travailThe utilization of solar energy to solve environmental problems such as water detoxification, air purification and hydrogen production has attracted great interest from the scientific community over the last two decades. Solar photocatalysis is an interesting avenue to target all these environmental issues. Currently, technologies do not yet allow for the efficient use of a significant portion of the solar spectrum, namely the infrared, which corresponds to nearly ~48% of the total solar spectrum. This thesis aims at preparing nanocomposite materials that use these low energy solar photons by converting them into high energy UV and visible photons and then using them for classical photocatalysis. To achieve this, two major aspects of the preparation of this modified photocatalyst were emphasized. Firstly, the synthesis of materials that could efficiently convert currently unused photons and secondly, the preparation of their composite with TiO2, the most widely used photocatalyst.This doctoral thesis focuses on an approach based on "upconversion" in order to extend the range of use of the solar spectrum. To achieve this goal, two optimization strategies were addressed. The optimization of the quantum efficiency of upconversion nanoparticles (UCNPs) using new anhydrous precursors and, the preparation of UCNPs-TiO2 nanocatalyst using metallogels and/or core-shell structures. Finally, we test the objective of using low energy infrared solar photons by performing photocatalysis under IR irradiation only using the platform developed in this work
26
Nascimento, Ulisses Magalhães. "Preparação, caracterização e testes catalíticos de um fotocatalisador magnético (Fe3O4/TiO2) na degradação de um poluente-modelo: acid blue 9". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-23042013-112144/.
Testo completoAbstract (sommario):
A aplicação de semicondutores no tratamento de água e efluentes líquidos é uma tecnologia de remediação ambiental promissora, em especial para poluentes orgânicos. Entre os vários semicondutores que também são fotocatalisadores, o TiO2 é amplamente usado em aplicações ambientais, por ser inerte biológica e quimicamente, ter elevado potencial de oxidação, baixo custo e estabilidade frente à corrosão. Entretanto, o TiO2 também tem algumas desvantagens, tais como: ele é excitado apenas por luz UV e requer uma operação unitária adicional (por exemplo, filtração ou centrifugação) para o reuso do catalisador. Para contornar estas limitações, usou-se um procedimento simples para a síntese de um fotocatalisador magnético (Fe3O4/TiO2) com alta área superficial específica e atividade catalítica, quando comparado com o TiO2 P25 da Evonik. O fotocatalisador foi sintetizado através de um procedimento em três etapas: (1) Partículas α-Fe2O3 foram obtidas por precipitação de uma solução de FeCl3.6H2O 0.01 mol L-1, que foi submetida a uma hidrólise forçada à 100°C por 48 h; (2) Partículas de α-Fe2O3/TiO2 foram obtidas por heterocoagulação de oxi-hidróxidos de Ti(IV) sobre as partículas de α-Fe2O3, as quais foram calcinada a 500°C por 2 h; e (3) As partículas \"casaca/caroço\" do fotocatalisador foram obtidas por calcinação a 400°C por 1 h sob atmosfera redutora (H2). A atividade fotocatalítica do material sintetizado foi avaliada aplicando-o no descoramento de uma solução do corante Azul Ácido 9 (C.I. 42090). Os efeitos do pH e da concentração de catalisador foram estimados por meio de um planejamento fatorial 22. Foi obtido um fotocatalisador com área superficial específica de 202 m2 g-1, facilmente separável do meio reacional em aproximadamente 2 min com o auxílio de um ímã. O fotocatalisador apresentou absorção em toda a região do visível. A maior remoção de cor (54%) foi obtida com pH 3,0, 1,0 g L-1 de catalisador e 2 horas de reação.The use of semiconductors for treating polluted waters and wastewaters is a promising environmental remediation technology, especially for organic pollutants. Among the several semiconductors that are also photocatalysts, TiO2 is extensively used for environmental application, due to its biological and chemical inertness, high oxidation power, low cost, and stability regarding corrosion. However, TiO2 also has some disadvantages, such as: it is only UV-excited and requires an additional unit operation (e.g. filtration or centrifugation) for reuse purposes. In order to work around those limitations, a simple procedure for synthesizing a magnetic photocatalyst (Fe3O4/TiO2), with high specific surface area and good photocatalytic activity when compared to Evonik\'s TiO2 P25, was used. The photocatalyst was synthesized in a three-step procedure: (1) α-Fe2O3 particles were obtained, by precipitation, from FeCl3.6H2O 0.01 mol L-1, which underwent a forced acid hydrolysis at 100°C for 48 h; (2) α-Fe2O3/TiO2 particles were obtained, by heterocoagulation, of Ti(IV) oxide species on the α-Fe2O3, followed by calcination at 500°C for 2 h; and (3) The core/shell photocatalyst particles were obtained by calcination the α-Fe2O3/TiO2 particles at 400°C for 1 h under reducing atmosphere (H2). The photocatalytic activity of the synthesized material was assessed by the color removal of an Acid Blue 9 (C.I. 42090) dye solution. pH and catalyst dosage effects were estimated by a 22 factorial design. Fe3O4/TiO2 core/shell particles with specific surface area of 202 m2 g-1were obtained. They were easily separated from the reaction medium, in approximately 2 min, with the aid of a magnet. The photocatalyst absorbed radiation throughout the visible spectrum. The greatest color removal (54%) was achieved with pH 3.0, 1.0 g L-1 of photocatalyst, and 2 h of reaction.
27
Huo, Zhaohui. "Polyoxometalate - porphyrin hybrids systems : application for the photocurrent generation and the photocatalysis". Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF032/document.
Testo completoAbstract (sommario):
Des films du type polyoxométallates-porphyrines ont été synthetisés et sont basés sur des interactions du types covalentes ou électrostatiques. Les films polyoxométallates–porphyrines sont obtenus par électro-oxydation de l’octaéthylporphyrine de zinc (ZnOEP) ou la 5,15-ditolylporphyrine (H2T2P) en présence de différents types of polyoxométallates (POMs) portant deux groupes pyridyles pendants (py-POM-py) Trois type de systèmes py-POM-py ont été utilises : i) un Lindqvist polyoxovanadate fonctionalisé via deux groupes tris-alkoxo , ii) un derive organosilyl fonctionalisé du type Keggin ou Dawson, et iii) des briques du type Dawson [P2W15V3O62]9− fonctionalisée avec des groupements organiques bis-pyridine de géométrie variée via un greffage diolamide). Tous ces films ont été testé pour la génération de photocourant et la photocatalyse de la réduction de métaux (Ag et Pt). Des films électrostatiques POM-porphyrin ont été également préparés par incorporation de polyanion du type Preyssler [NaP5W30O110]14- sur les films de porphyrine polycationic (poly-ZnOEP) électropolymérisés avec des espaceurs viologènes ou bis-viologènes. [NaP5W30O110]14- agit comme relais d’électron entre une porphyrine excitée ZnOEP* et le viologène (ou le bis-viologène) retardant la recombinaison de charge ce qui permet une augmentation du photocourant. Enfin, des nanoparticules POM@NPs (Pt, Au, Ag) ont été introduites en surface de copolymère polycationique à base de bis-porphyrine par métathèse afin d’augmenter l’efficacité de la génération de photocourant. La résonance de plasmon de surface localisée qui se produit à la surface des nanoparticules d'argent a sensiblement améliorée l'excitation électronique de porphyrinePolyoxometalates-porphyrin hybrid films were synthesized based on covalent or electrostatic interactions. Copolymeric polyoxometalate–porphyrin films were obtained by the electro-oxidation of zinc octaethylporphyrin (ZnOEP) or 5,15-ditolyl porphyrin (H2T2P) in the presence of a different type of polyoxometalates (POMs) bearing two pyridyl groups (py-POM-py). Three type of py-POM-py have been used: i) a tris-alkoxo functionalized Lindqvist polyoxovanadate, ii) an organosilyl functionalized Keggin-type [PW11Si2O40C26H16N2]3- and Dawson-type [P2W17Si2O62C26H16N2]6-, and iii) a bis-pyridine-substituted organo-polyoxometallic bricks using [P2W15V3O62]9− diolamide-grafting method with various geometries of the pendant group. All are applied for photocurrent generation and photocatalytical recovery of metals (Ag and Pt). Electrostatic POM-porphyrin films were also prepared by incorporated Preyssler type polyanion [NaP5W30O110]14- onto the electropolymerized polycationic porphyrin (poly-ZnOEP) with viologen or bis-viologen as spacers. [NaP5W30O110]14- as an efficient electron shuttle between the excited ZnOEP and viologen (or bis-viologen) which effectively retarded the fast charge pair recombination and enhanced the photocurrent magnitude. Later, we introduced nanoparticles POM@MNPs to a bis-porphyrin copolymer through metathesis reaction to further improve the efficiency of the photocurrent generation in which the localized surface plasmon resonance that occurs at the surface of silver nanoparticles has substantially enhanced the electronic excitation of surface-anchored porphyrin
28
Ede, Sarah Melinda. "Infrared and photocatalytic studies of model bacterial species for water treatment". Thesis, Queensland University of Technology, 2006. https://eprints.qut.edu.au/16438/1/Sarah_Ede_Thesis.pdf.
Testo completoAbstract (sommario):
The use of a CO2 infrared (IR) laser and photocatalysis for water treatment microorganism disinfection purposes was investigated.
During CO2 infrared (IR) laser treatment E. cloacae inactivation was comparable to inactivation via ultraviolet (UV) treatment; however no inactivation of the more resistant B. subtilis endospores occurred. Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy of the bacterial cells displayed increased polysaccharide contents after IR treatment. FTIR and Raman spectroscopy of simple carbohydrates before and after IR laser treatment displayed no spectral changes, with the exception of N-acetyl-D-glucosamine (NAG), which was partially attributed to sampling techniques. E. cloacae inactivation during IR treatment was attributed to localised and overall temperature increases within the water. Due to the inability to inactivate B. subtilis endospores this technique is not suitable for water treatment purposes.
Photocatalytic water treatment using novel TiO2 colloids prepared via a postsynthetic microwave-modification process (MW-treated) was also examined. These colloids were characterised using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses and compared to Degussa P25 and convection hydrothermally-treated (HT-treated) TiO2. Slurry suspensions displayed comparable E. coli inactivation rates, so the colloids were examined in immobilised form using both a model organic degradant, oxalic acid, and E. coli. Oxalic acid degradation studies showed that the MW-treated colloids displayed similar inactivation rates to the HT-treated TiO2, due to their pure anatase composition, while Degussa P25 displayed higher inactivation rates. Investigations into the effect of shortening UV wavelength were also performed. Degussa P25 was the only catalyst which displayed higher apparent quantum yields upon shortening the UV wavelength, which was attributed to its mixed-phase anatase-rutile composition.
As E. coli inactivation was observed using distilled water, photocatalysis in natural river water was trailed. It was discovered that the pH had to be lowered from 7.5 to 5.0 and the initial cell concentration must be approximately 1 x 103 colony forming units (CFU) per cm3 or less for inactivation to be observed during a 5 hour treatment period. At a catalyst loading of 1.0 mg per cm2, Degussa P25 absorbed all the applied UVA irradiation; however the MW- and HT-treated TiO2 colloids did not due to their smaller particle size. Therefore sandwich experiments were devised to evaluate the effect of unabsorbed UV irradiation within the system. Small colony variants were identified after photocatalytic and UV treatment, which pose a potential threat to public health.
Further investigation of the different TiO2 colloids was performed using in situ
FTIR, both with and without an applied potential and compared to a thermally prepared TiO2 catalyst. The latter displayed potential dependent photocatalysis, while the mesoporous TiO2 catalysts displayed potential independent photocatalysis. All catalyst types displayed increased degradation rates upon the application of a positive bias, which was followed in situ via the production of CO2. Sodium oxalate and NAG was examined for photocatalytic degradation, both of which were degraded to CO2, with proposed break-down products identified when using NAG.
29
Ede, Sarah Melinda. "Infrared and photocatalytic studies of model bacterial species for water treatment". Queensland University of Technology, 2006. http://eprints.qut.edu.au/16438/.
Testo completoAbstract (sommario):
The use of a CO2 infrared (IR) laser and photocatalysis for water treatment microorganism disinfection purposes was investigated. During CO2 infrared (IR) laser treatment E. cloacae inactivation was comparable to inactivation via ultraviolet (UV) treatment; however no inactivation of the more resistant B. subtilis endospores occurred. Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy of the bacterial cells displayed increased polysaccharide contents after IR treatment. FTIR and Raman spectroscopy of simple carbohydrates before and after IR laser treatment displayed no spectral changes, with the exception of N-acetyl-D-glucosamine (NAG), which was partially attributed to sampling techniques. E. cloacae inactivation during IR treatment was attributed to localised and overall temperature increases within the water. Due to the inability to inactivate B. subtilis endospores this technique is not suitable for water treatment purposes. Photocatalytic water treatment using novel TiO2 colloids prepared via a postsynthetic microwave-modification process (MW-treated) was also examined. These colloids were characterised using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses and compared to Degussa P25 and convection hydrothermally-treated (HT-treated) TiO2. Slurry suspensions displayed comparable E. coli inactivation rates, so the colloids were examined in immobilised form using both a model organic degradant, oxalic acid, and E. coli. Oxalic acid degradation studies showed that the MW-treated colloids displayed similar inactivation rates to the HT-treated TiO2, due to their pure anatase composition, while Degussa P25 displayed higher inactivation rates. Investigations into the effect of shortening UV wavelength were also performed. Degussa P25 was the only catalyst which displayed higher apparent quantum yields upon shortening the UV wavelength, which was attributed to its mixed-phase anatase-rutile composition. As E. coli inactivation was observed using distilled water, photocatalysis in natural river water was trailed. It was discovered that the pH had to be lowered from 7.5 to 5.0 and the initial cell concentration must be approximately 1 x 103 colony forming units (CFU) per cm3 or less for inactivation to be observed during a 5 hour treatment period. At a catalyst loading of 1.0 mg per cm2, Degussa P25 absorbed all the applied UVA irradiation; however the MW- and HT-treated TiO2 colloids did not due to their smaller particle size. Therefore sandwich experiments were devised to evaluate the effect of unabsorbed UV irradiation within the system. Small colony variants were identified after photocatalytic and UV treatment, which pose a potential threat to public health. Further investigation of the different TiO2 colloids was performed using in situ FTIR, both with and without an applied potential and compared to a thermally prepared TiO2 catalyst. The latter displayed potential dependent photocatalysis, while the mesoporous TiO2 catalysts displayed potential independent photocatalysis. All catalyst types displayed increased degradation rates upon the application of a positive bias, which was followed in situ via the production of CO2. Sodium oxalate and NAG was examined for photocatalytic degradation, both of which were degraded to CO2, with proposed break-down products identified when using NAG.
30
Karriem, Fatiema. "Oxidative fixation of dinitrogen by photocatalysis". Thesis, University of Western Cape, 2000. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5777_1267648612.
Testo completoAbstract (sommario):
The heterogeneous photocatalytic oxidation of dinitrogen to nitrate, NO3 and/or nitrite, no2 using peroxy species of titanium (IV) in aqueous suspensions has been investigated. The photocatalysts used were titanium peroxide and Degussa p25 TiO2 pretreated with H2O2. These photocatalysts were investigated by SEM and FTIR spectroscopy.
31
Cai, Yanling. "Titanium Dioxide Photocatalysis in Biomaterials Applications". Doctoral thesis, Uppsala universitet, Nanoteknologi och funktionella material, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160634.
Testo completoAbstract (sommario):
Despite extensive preventative efforts, the problem of controlling infections associated with biomedical materials persists. Bacteria tend to colonize on biocompatible materials and form biofilms; thus, novel biomaterials with antibacterial properties are of great interest. In this thesis, titanium dioxide (TiO2)-associated photocatalysis under ultraviolet (UV) irradiation was investigated as a strategy for developing bioactivity and antibacterial properties on biomaterials. Although much of the work was specifically directed towards dental materials, the results presented are applicable to a wide range of biomaterial applications. Most of the experimental work in the thesis was based on a resin-TiO2 nanocomposite that was prepared by adding 20 wt% TiO2 nanoparticles to a resin-based polymer material. Tests showed that the addition of the nanoparticles endowed the adhesive material with photocatalytic activity without affecting the functional bonding strength. Subsequent studies indicated a number of additional beneficial properties associated with the nanocomposite that appear promising for biomaterial applications. For example, irradiation with UV light induced bioactivity on the otherwise non-bioactive nanocomposite; this was indicated by hydroxyapatite formation on the surface following soaking in Dulbecco’s phosphate-buffered saline. Under UV irradiation, the resin-TiO2 nanocomposite provided effective antibacterial action against both planktonic and biofilm bacteria. UV irradiation of the nanocomposite also provided a prolonged antibacterial effect that continued after removal of the UV light source. UV treatment also reduced bacterial adhesion to the resin-TiO2 surface. The mechanisms involved in the antibacterial effects of TiO2 photocatalysis were studied by investigating the specific contributions of the photocatalytic reaction products (the reactive oxygen species) and their disinfection kinetics. Methods of improving the viability analysis of bacteria subjected to photocatalysis were also developed.
32
Gomes, Ana Catarina Costa. "Photocatalysis : Carbonylation of arenas and alkanes". Thesis, University of York, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516370.
Testo completo
33
Lafta, Abbas Jassim Attia. "New materials for photocatalysis and photovoltaics". Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4105/.
Testo completoAbstract (sommario):
Photocatalytic processes are of widespread interest. Among different types of photocatalytic material TiO2 is the generally considered amongst the best due to its favourable physical and chemical properties. In recent decades, photovoltaic devices have been widely studied to provide alternative routes to energy and reduce dependency upon fossil fuel. Solar photovoltaic are cells capable of harvesting of sunlight into electrical power. This technology is one of the most promising routes in the search for sustainable and renewable sources of energy. The study presented in this thesis relates to the preparation and characterization of a range of different materials which can be applied in photocatalytic processes and for photovoltaic devices. The photocatalysis work has been focused mainly upon modification of the various phases of titanium dioxide. This has been undertaken via doping with nitrogen by treatment with ammonia at different temperatures. In addition, samples containing Al, Co and Cu dopants, as well as their N doped counterparts, have been prepared, characterized and tested. The photocatalytic activity was screened by following photocatalytic decomposition of an aqueous solution of methylene blue using a light source containing various components in the UV and visible regions. For selected samples, the photocatalytic activity for polymerization of methyl methacrylate and styrene has been determined with the aim of producing composites. In terms of potential photovoltaic materials, the synthesis of novel viologen compounds and polymerization via electrochemical and chemical means has been undertaken. Different viologen monomers have been synthesized with various moieties in conjugation to a phenanthroline core to afford novel push-pull systems. These compounds have incorporated both TCNE and TCNQ moieties as strong electron acceptors and hence yield chromophore with large dipole moments. In addition, novel ruthenium complexes were prepared featuring bipyridine and phenanthroline ligands. The optical and redox properties of these materials have been investigated. DSSCs have been fabricated form some of these systems and their properties have been compared to dye 719.
34
Elhage, Ayda. "Palladium-based Catalyst for Heterogeneous Photocatalysis". Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39388.
Testo completoAbstract (sommario):
Over the past decade, heterogeneous photocatalysis have gained lots of interest and attention among the organic chemistry community due to its applicability as an alternative to its homogeneous counterpart. Heterogeneous catalysis offers the advantages of easy separation and reusability of the catalyst. Several studies showed that under optimized conditions, efficient and highly selective catalytic systems could be developed using supported metal/metal oxide nanoparticles. In this dissertation, we summarize the progress in the development of supported palladium nanoparticles for different types of organic reactions.
Palladium-decorated TiO2 is a moisture, air-tolerant, and versatile catalyst. The direct excitation of Pd nanoparticles selectively isomerized the benzyl-substituted alkenes to phenyl-substituted alkenes (E-isomer) with complete conversion over Pd@TiO2 under H2-free conditions. Likewise, light excited Pd nanoparticles catalyzed Sonogashira coupling, a C-C coupling reaction between different aryl iodides and acetylenes under very mild conditions in short reaction times. On the other hand, UV irradiation of Pd@TiO2 in alcoholic solutions promotes alkenes hydrogenation at room temperature under Argon. Thus, The photocatalytic activity of Pd@TiO2 can be easily tuned by changing the irradiation wavelength. Nevertheless, some of these systems suffer from catalyst deactivation, one of the main challenges faced in heterogeneous catalysis that decreases the reusability potential of the materials. In order to overcome this problem, we developed an innovative method called “Catalytic Farming”. Our reactivation strategy is based on the crop rotation system used in agriculture. Thus, alternating different catalytic reactions using the same catalyst can reactivate the catalyst surface by restoring its oxidation states and extend the catalyst lifetime along with its selectivity and efficiency. In this work, the rotation strategy is illustrated by Sonogashira coupling –problem reaction that depletes the catalyst– and Ullmann homocoupling –plausible recovery reaction that restores the oxidation state of the catalyst (Pd@TiO2). The selection of the reactions in this approach is based on mechanistic studies that include the role of the solvent and evaluation of the palladium oxidation state after each reaction.
In a more exploratory analysis, we successfully demonstrated that Pd nanoparticles could be supported in a wide range of materials, including inert ones such as nanodiamonds or glass fibers. The study of the action spectrum shows that direct excitation of the Pd nanoparticles is a requisite for Sonogashira coupling reactions. The main advantages of heterogeneous catalysis compared to its homogeneous counterpart are easy separation and reusability of the catalyst.
Finally in order to facilitate catalyst separation from batch reaction and develop a suitable catalytic system for continuous flow chemistry, we employed glass fibers as catalyst support for a wide variety of thermal and photochemical organic reactions including C-C coupling, dehalogenation and cycloaddition. Different metal/metal oxide nanoparticles, namely Pd, Co, Cu, Au, and Ru were deposited on glass wool and fully characterized. As a proof of concept, Pd decorated glass fibers were employed in heterogeneous flow photocatalysis for Sonogashira coupling and reductive de-halogenation of aryl iodides.
35
Wang, Zheng. "Studies on the Photocatalytic Conversion of CO2 in and by H2O over Heterogeneous Photocatalysts". 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/199324.
Testo completo
36
Yamamoto, Akira. "Studies on Low-temperature De-NoX System over TiO2-based Photocatalysts". 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/200501.
Testo completo
37
Lam, Chun-wai Ringo, e 林俊偉. "Development of photocatalytic oxidation technology for purification ofair and water". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38572382.
Testo completo
38
Hathway, Timothy Lee. "Titanium dioxide photocatalysis studies of the degradation of organic molecules and characterization of photocatalysts using mechanistic organic chemistry /". [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3369929.
Testo completo
39
Sasser, Shawn. "The Design and Testing of a Novel Batch Photocatalytic Reactor and Photocatalyst". Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6381.
Testo completoAbstract (sommario):
With an ever-increasing human population, the importance in having sustainable energy resources is becoming increasingly evident, as the current energy habits have brought about massive atmospheric pollution in the form of CO2 emissions, resulting in a rise in the average global temperature. To battle the effects of climate change, many alternative energy resources have been investigated. Among these, photocatalytic conversion of CO2 to renewable hydrocarbon fuels such as methane and methanol is one of the most desirable, as it provides the opportunity to utilize the sun’s energy to convert CO2 to renewable fuels. The work in this study is primarily focused on developing a batch photoreactor system to improve the integrity of photocatalytic experiments and using that system to test the performance of Er-doped solid solutions of ZnO/GaN (ZG) towards photocatalytic reduction of CO2.
To upgrade the abilities from previous photoreactor systems, a novel photoreactor was deigned in SolidWorks and fabricated in-house. The photoreactor was designed to increase surface area at the gas-solid interface, improve utilization of the light source, and promote larger mass transfer rates of reactants to the catalyst surface. These goals were accomplished by immobilizing the catalyst on a transparent porous support, incorporating a threaded mount on top of the photoreactor for mounting an interchangeable LED to illuminate the catalyst bed, and recirculating the gas mixture through a closed loop system with a compressor, respectively.
Pure and Er-doped ZG photocatalyst samples were synthesized through the nitridation of Zn/Ga/CO3 layered double hydroxide (LDH) precursors. Erbium was chosen as a dopant to potentially enhance the photocatalyst by utilizing its upconversion photoluminescence properties. The LDH precursors were synthesized using a coprecipitation method. Levels of erbium doping were varied by [Er]/[Zn] = 0, 0.025, 0.05, and 0.10. ZnO/GaN solid solutions were chosen for their low bandgap energy so that visible light, roughly 40% of the solar spectrum [1], can be used to activate the catalyst. Diffuse reflectance spectroscopic data of the pure and Er-doped ZG samples were measured and used to calculate the bandgap energy. Bandgap values of EG = 2.53, 2.52, 2.56, and 2.56 eV were obtained for the [Er]/[Zn] = 0, 0.025, 0.05, and 0.10 samples, respectively. XRD data of the LDH samples indicated the formation of Zn/Ga/CO3 LDH and the Zn(OH)2, β-Ga2O3, α-GaOOH, and ZnGa2O4 impurity phases. Moreover, the broadening of the diffraction peaks in the Er-doped LDH samples suggested Er3+ ions substituted the Ga3+ ions in the LDH structure. XRD data of the pure and Er-doped ZG samples revealed strong peaks at 2θ = 31.86, 34.37, and 36.31°, indicating the formation of a solid solution of ZnO and GaN. Additionally, peaks at 2θ = 29.27, 48.79, and 57.86° indicate the formation of the secondary phase of Er2O3 in the Er-doped samples. Consequently, it was concluded that the Er3+ ions did not go into the crystal structure of the oxynitride solid solution. These findings were supported by the SEM images revealing hexagonal nanoplates and nanoprisms that coincide with the solid solution along with additional nanostructures corresponding to the Er2O3 phase.
During photocatalytic experiments with the pure and Er-doped ZG samples, CO2, and UV light (405 nm nominal wavelength), hydrocarbon production was observed to increase with increasing [Er/Zn]. However, results from control experiments with no catalyst while varying the nominal LED wavelength and the o-ring material suggested that hydrocarbon formation was partially or entirely the result of the o-ring photochemically degrading in the presence of UV light. An o-ring comprised of a silicone material yielded zero hydrocarbon formation in the presence of UV light, while this was not the case for o-ring materials of Viton® and Kalrez®. These findings can be applied to other research groups that plan to perform photocatalytic experiments in a photoreactor with o-rings while using a UV light source.
40
Pang, Rui. "Development of Novel Photocatalysts and Co-catalysts for Photocatalytic Conversion of CO2 by H20". Kyoto University, 2019. http://hdl.handle.net/2433/242527.
Testo completo
41
Xiao, Qi. "Visible light photocatalytic synthesis of fine organic chemicals with new photocatalysts". Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/84078/14/Qi_Xiao_Thesis.pdf.
Testo completoAbstract (sommario):
This project was a step forward in developing new recyclable photocatalysts for chemical reactions. These new photocatalysts can facilitate reactions by using visible light under moderate reaction conditions which is suitable for a sustainable, green and eco-friendly modern chemical industry. The outcome of the study greatly extended our understanding in metal nanoparticle photocatalysis, which reveals new photocatalytic mechanisms for the controlled transformation of chemical reactions. The prospect of sunlight irradiation driving chemical reactions may provide opportunity for the organic synthesis via a more controlled, simplified, and greener process in the future.
42
Shahine, Issraa. "A chemical route to design plasmonic-semiconductor nanomaterials heterojunction for photocatalysis applications". Thesis, Université de Lorraine, 2019. http://www.theses.fr/2019LORR0105/document.
Testo completoAbstract (sommario):
L’ingénierie de nanomatériaux hybrides semi-conducteurs/plasmoniques représente une technologie durable en raison de l’efficacité parfaite du couplage pour améliorer, rénover et enrichir les propriétés des composants intégrés. Ce couplage a pour résultat la variation des propriétés fonctionnelles du système, grâce auquel les plasmons de surface générés par les métaux peuvent améliorer la séparation des charges, l’absorption de la lumière et la luminescence du semi-conducteur. Ce phénomène permet de fortes interactions avec d'autres éléments photoniques tels que les émetteurs quantiques. Ces fonctionnalités aux multiples facettes découlent de l'interaction synergique exciton-plasmon entre les unités liées. Ainsi, les nanomatériaux hybrides conviennent à diverses applications, notamment : conversion de l'énergie solaire, dispositifs optoélectroniques, diodes électroluminescentes (LED), photocatalyse, détection biomédicale, etc. Les nanostructures Au-ZnO suscitent un intérêt croissant dans ces applications où le couplage de ZnO à de nanoparticules d’or (GNPs) favorise la réponse du système dans le domaine du visible grâce à leur résonance plasmon de surface (SPR). En fonction de la taille de deux nanomatériaux, de la distance qui les sépare et leurs rapports massiques dans un échantillon, les propriétés des particules hybrides peuvent varier. Dans ce contexte, nous nous sommes concentrés sur la construction de nano-cristaux (NCs) de ZnO purs de dimensions contrôlables, puis incorporés dans des solutions de GNPs par une simple voie chimique. Ce travail est divisé en deux parties : la première consiste à effectuer une synthèse de nanocristaux de ZnO (NCs) purs présentant d'excellentes propriétés de photoluminescence dans l’UV. Ceci a été réalisé par une synthèse à basse température, aboutissant à des structures rugueuses et amorphes. La synthèse a été suivie d'un traitement post-thermique afin de cristalliser les nanoparticules obtenues. Une étude structurale et optique poussée a été établie à la suite de la synthèse (SEM, TEM, DRX, photoluminescence). Les activités photocatalytiques des ZnO NCs ont été étudiées en mesurant leur capacité à dégrader le bleu de méthylène (MB). De plus, la relation entre les structures en ZnO, la luminescence et les propriétés photocatalytiques a été explorée en détail. Dans la deuxième étape, les ZnO NCs obtenus ont été couplés ajoutés à des nanoparticules d'or de tailles et fractions volumiques variables. Le rôle effectif des GNPs concernant leur morphologie, leur contenu et leur effet SPR sur la photoémission des nanostructures de ZnO est souligné par le transfert de charge et / ou d'énergie entre les constituants du système hybride. De plus, l’activité photocatalytique du système hybride a été examinée. Comme débouché et perspective de ce travail de thèse, l'intégration des ZnO NC dans une couche nanoporeuse de polymère (PMMA) a été réalisée et caractérisée afin d'obtenir un substrat de large surface à base de ZnO. Les ZnO NCs assemblés dans du PMMA pourraient être des substrats prometteurs en tant que catalyseurs pour la croissance de nanofils de ZnO, de nanomatériaux métalliques et de matériaux hybridesHybrid heterojunctions composed of semiconductors and metallic nanostructures have perceived as a sustainable technology, due to their perfect effectiveness in improving, renovating, and enriching the properties of the integrated components. The cooperative coupling results in the variation of the system’s functional properties, by which the metal-generated surface plasmon resonance can enhance the charge separation, light absorption, as well as luminescence of the semiconductor. This phenomenon enables strong interactions with other photonic elements such as quantum emitters. These multifaceted functionalities arise from the synergic exciton-plasmon interaction between the linked units. Thereby, hybrid systems become suitable for various applications including: solar energy conversion, optoelectronic devices, light-emitting diodes (LED), photocatalysis, biomedical sensing, etc. Au-ZnO nanostructures have received growing interest in these applications, where the deposition of gold nanoparticles (GNPs) promotes the system’s response towards the visible region of the light spectrum through their surface plasmon resonance (SPR). Based on a specific size and purity of ZnO nanostructures, as well as the GNPs, and a definite inter-distance between the nanoparticles, the properties of the ZnO nanostructures are varied, especially the photoemission and photocatalytic ones. In this context, we have focused on the construction of size-tunable ZnO nanocrystals (NCs), then incorporated into GNPs solutions using a simple chemical way. This work is divided into two parts: the first is to perform synthesis of pure ZnO NCs having excellent UV photoluminescence. This was achieved through a low-temperature aqueous synthesis, resulting in rough and amorphous structures. The synthesis was followed by a post-thermal treatment in order to crystallize the obtained particles. The synthesis was followed by structural and optical studies (SEM, TEM, XRD, photoluminescence). The photocatalytic activities of ZnO NCs were studied through tailoring their ability to degrade the methylene blue (MB) dye. In addition, the relationship between ZnO structures, luminescence, and photocatalytic properties was explored in details. In the second step, the obtained ZnO NCs were added to gold nanoparticles of various sizes and volume fractions. The effective role of GNPs concerning their size, amount, and their capping molecule on the photoemission of the ZnO nanostructures was emphasized through the charge and/or energy transfer between the constituents in the hybrid system. In the same way, the systems photocatalytic activities were examined after coupling ZnO to GNPs. Further advancement in the integration of the ZnO NCs into PMMA polymer layers was featured in order to obtain large area template of homogenous ZnO properties. The PMMA-assembled ZnO nanoparticles could be promising substrates as catalysts for growing ZnO nanowires, metallic nanoparticles and hybrid nanomaterials
43
Grant, Neil. "Application of titania photocatalysis for organic synthesis". Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=185854.
Testo completoAbstract (sommario):
The addition of benzyltrimethylsilane to maleic anhydride mediated by TiO2 photocatalysis was initially investigated. The affect of changing the catalyst, the radical trap loading and the substitution of the benzyltrimethylsilane molecule was assessed. Cyclisation precursors based on benzyltrimethylsilane were prepared, but were found not to cyclise via TiO2 photocatalysis. A number of other systems were assessed for their ability to cyclise under TiO2 photocatalysis; tertiary amines, aminomethyltrimethylsilanes, phenoxymethyltrimethylsilanes and phenoxyacetic acids. Phenoxymethyltrimethylsilane and phenoxyacetic acid were found to add effectively to maleic anhydride under TiO2 photocatalysis conditions, however they were unreactive with regards to cyclisation. EPR spectroscopy has been employed to characterise further the reaction of benzylsilanes with maleic anhydride under TiO2 photocatalytic conditions. A number of EPR active species were observed; trapped holes and electrons, which reside within the TiO2 catalyst. In addition, methyl and benzyl radicals were observed and were found to originate from the oxidation of the benzylsilanes by trapped holes in the TiO2 catalyst. However, no radical species were observed from the maleic anhydride. These observations had the following consequences for the currently proposed reaction mechanism for the addition of benzyltrimethylsilane with maleic anhydride under TiO2 photocatalysis. The observation of the benzyl radical definitely proved that the reactive intermediate was indeed the proposed benzyl radical The absence of any maleic anhydride EPR active species cast doubt on the role of maleic anhydride as an electron trap. Moreover when maleic anhydride is removed from the reaction system, interstitial Ti3+ species is absent from the EPR spectra, indicating that maleic anhydride is in fact acting as a hole trap.
44
Sawunyama, P. "Catalysis, photocatalysis and corrosion involving metal oxides". Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638775.
Testo completoAbstract (sommario):
In today's environmentally conscious society, greater emphasis is now on clean chemical technologies. Reactions at metal oxide-solution interfaces have received much attention in this respect. Although progress has been made in applying the associated technology to such fields as hydrometallurgy, solar energy conversion, descaling of pipework and nuclear plant decontamination, and environmental decontamination, the fundamental processes involved are not always understood. There is a need, therefore, to investigate these processes further. Chapter Three describes the oxidative dissolution kinetics of ruthenium dioxide hydrate to ruthenium tetroxide by periodate in perchloric acid. The kinetics fit a soft-centre model, in which ruthenium dioxide hydrate particles are assumed to be monodispersed, spherical but inhomogeneous in composition, comprising a difficult-to-corrode outer shell and a more easy-to-corrode inner core. Chapter Four details the kinetics of oxidative dissolution of chromium(III) oxides to chromic acid by periodate in perchloric acid. The kinetics obey a simple inverse-cubic rate model, in which chromium(III) oxide particles, are assumed to be monodispersed, spherical and homogeneous in composition. A kinetic model that can simulate this process under reaction conditions that produce non-linear inverse-cubic plots is described. In Chapter Five, the photocatalytic efficiencies of laboratory made and commercial titanium dioxide samples are compared using a standard test reaction; the photomineralisation of 4-chlorophenol to carbon dioxide, water and hydrochloric acid, mediated by Degussa P25 titanium dioxide in a batch reactor. The results show that there is no clear simple dependence upon physical characteristics of the titanium oxide sample such as: degree of crystallinity, surface area, and percentage water content. The kinetics of photomineralisation of 4-chlorophenol sensitised by the most active laboratory made titanium dioxide sample are discussed. Chapter Six outlines the photo-oxidation of manganese(II) to manganese dioxide, in the presence of, first, the nitrate ion, and then titanium dioxide in nitrate free solutions.
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Belghazi, A. "Heterogeneous semiconductor UV-photocatalysis for water purification". Thesis, Swansea University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636072.
Testo completoAbstract (sommario):
As traditional disinfection techniques have proved to be inefficient in coping with toxic pollutants, there is a real need to create and develop alternatives such as Advanced Oxidation Processes (AOP's). As one of the most promising AOP's developed to date, heterogeneous semiconductor UV-photocatalysis has been shown to efficiently mineralise and inactivate a wide range of organic, inorganic and biological pollutants. This technique is based on the powerful redox properties of UV-illuminated semiconductors. The photocatalyst (semiconductor), which is insoluble in water, can be used in the form of a dispersion or as a thin coated film over which the pollutant can flow and interact in the liquid as well as in the gas phase. Although many pollutants have been studied, the development of more powerful analytical tools has meant that trace levels of water pollutants such as bromate, a potential carcinogenic by-product of the ozonation process and their destruction needs to be addressed. Chapters Three, Four and Five investigate the development and use of an analytical method for monitoring trace levels of bromate (ppb level or μg.dm-3), in studies involving the use of Granular Activated Carbon (or GAC) and platinised TiO2 (Pt-TiO2) UV-photocatalysis for the removal of this inorganic pollutant. In Chapter Six, a study of TiO2 photocatalysed oxidation of urea-based pesticides is given. Chapter Seven investigates two photoreactor designs for use in flow systems with larger volumes of pollutant which is required if the system is to be commercially viable. These flow photoreactors use thin immobilised films of TiO2 over which the pollutant can flow. Finally, using the flow photoreactor designs studied in Chapter Seven, Chapter Eight presents a study of the photocatalysed oxidation of volatile organic pollutants (or VOC's) in the gas phase.
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Jo, Won Jun. "Solar energy conversion via photovoltaics and photocatalysis". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111409.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references.
Due to the forthcoming shortage of natural resources, the demand for more efficient and ecofriendly chemical processes for the conversion of energy and matter, especially with respect to carbon management, is growing rapidly. Therefore, a search for high-performance solar energy conversion systems to end the current carbon economy era is of paramount importance in both academic and industrial sectors. In this regard, we have studied organic photovoltaics and solar water splitting by using oCVD (Oxidative Chemical Vapor Deposition) polymers and doping-treated bismuth vanadate (BiVO 4), respectively. oCVD is a solvent-free conformal vacuum-based technique to enable thin-film fabrication of insoluble polymers at moderate vacuum (~ 0.1 Torr) and low temperature (25 150 °C). Moreover, oCVD carries the well-cited processing benefits of vacuum processing, such as parallel and sequential deposition, well-defined thickness control, large-area uniformity, and inline integration with other standard vacuum processes (e.g., vacuum thermal evaporation). Based on the above-mentioned technical advantages from oCVD, polyselenophene and poly(3,4- dimethoxythiophene) have been successfully applied to organic photovoltaics. Cost-effective solar hydrogen production requires catalytic materials that have earth-abundant element composition, suitable photoelectrochemical properties, and broad technological applicability. To create this versatile catalytic material, controlling the catalyst's atomic structure is of primary importance since their functionalities (e.g., electronic band structure, catalytic activity, chemical stability, etc.) are governed by its atomic structure. According to the strategy, BiVO 4's atomic structure has been engineered via phosphorus, indium and molybdenum doping. The improved photocatalytic behavior of doping-treated BiVO4 has been studied within experimental and computational domains.
by Won Jun Jo.
Ph. D.
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Kazantsev, Roman V. "Self-Assembled, Crystalline Organic Nanostructures for Photocatalysis". Thesis, Northwestern University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=3741384.
Testo completoAbstract (sommario):
The goal of this thesis was to integrate light-absorbing supramolecular materials into a photocatalytic system for solar-to-fuel conversion. Toward this end, a series of perylene-based chromophore amphiphiles was synthesized and their self-assembly properties explored. Characterization of these materials by electron microscopy and x-ray scattering techniques revealed molecular assembly into 1D ribbon nanostructures. Surprisingly, these ribbons were observed to spontaneously crystallize in solution, as observed by wide-angle and grazing incidence X-ray scattering. These crystalline nanostructures could be gelled with oppositely charged electrolytes, forming a 3D light-absorbing scaffold. By designing and synthesizing oppositely charged proton reduction catalysts to electrostatically bind to the light-absorbing scaffold, hydrogen gas was detected by gas chromatography after white light illumination of the scaffold / catalyst system. As a direct result of their crystalline nature, the exciton properties of these materials and the photocatalytic properties of the system could be tuned by slight modification in their molecular packing arrangement. These changes were achieved by creating a library of chromophores with small functional groups directly attached to the PMI core. Some amphiphiles in this library were observed to undergo a crystalline phase transition between two unique packing arrangements as evidenced by variable temperature absorbance and x-ray scattering experiments. This transition involved a substantial change in the exciton properties of the material. Surprisingly, some crystalline phases carried the distinct spectral signature of charge-transfer (CT) excitons, an excitation that is shared among multiple chromophores. Characterization of this CT state was accomplished by ground state and transient absorption spectroscopy, transient electron paramagnetic resonance spectroscopy, and second-order harmonic generation microscopy. The crystalline nanostructures of the library that yielded evidence for CT-excitons were the most photocatalytically active. This observation is consistent with established theories developed elsewhere that connect CT-exciton formation with an enhancement in exciton mobility.
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Khan, Muhammad Abdullah. "Carbon nitride based materials for heterogeneous photocatalysis". Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:8498a9f5-e5c8-4eda-b62d-0cd36471759c.
Testo completoAbstract (sommario):
Photocatalysis on semiconductor surfaces has grown tremendously in the last four decades. One reason for this is its analogy with photosynthesis, the most important natural photochemical process. Semiconductors to some extent can mimic the key steps of this fascinating heterogeneous photocatalytic process, i.e., photochemical charge generation, charge trapping, interfacial electron exchange and subsequent reaction. Building on this premise this thesis constitutes an investigation into the photocatalytic properties and applications of semiconducting layered framework carbon nitride based materials. Similar to traditional photocatalysts, the photocatalytic activity and efficiency of carbon nitride systems developed thus far is limited mainly by the fast recombination and low mobility of photogenerated excitons. Here, by exploiting the band alignment strategy, carbon nitride isotype (type II) and carbon nitride-niobium oxide of type II semiconductor heterojunctions were successfully constructed with the aim of suppressing the exciton recombination and improving charge extraction for the successful initiation of desirable redox chemistry. These features were demonstrated by employing the materials in heterogeneous photocatalysis for water splitting, organic pollutant decomposition and photochemical organic synthesis. Carbon nitride isotype heterojunctions constructed by controlled thermal condensation are shown to exhibit lower recombination of excitons relative to the pristine carbon nitride. As a consequence photocurrent generation and visible light driven H2 production activity was enhanced. This increase is attributed to the surface passivation and improved electron mobility of built-in electric field which arises from the topology-induced band offset of favoured type II heterojunction configuration. Building on the insights into the heterojunction-activity dependence, new type II graphitic carbon nitride (C3N4), Nb2O5 (C3N4-Nb2O5), heterojunctions synthesised via a hydrothermal method were exploited for their photodegradation ability of the organic pollutants. The synergic effect of carbon nitride and Nb2O5 coupling leads to the substantial photocatalytic activity improvement which can be attributed to the formation of an intimate interface and gradual attenuation of energy-wasteful charge recombination processes in C3N4-Nb2O5 heterojunctions materials. While water splitting and pollutant decomposition using semiconductors has received the bulk of attention, the possibilities concerning chemical synthesis are only beginning to be meaningfully exploited. We, therefore, employed carbon nitride to catalyse photo organic synthesis. It was demonstrated for the first time that carbon nitride can efficiently catalyse the photoacetalization reactions of aldehydes/ketones with alcohols, forming acetals at high yields using visible light under ambient conditions. Mechanistic studies suggest that the transient charge separation at the surface of this material is sufficient to catalyse the reaction in the absence of Lewis or Brønsted acids or solvent systems. Since the photoacetalization of aldehydes occurs under conditions similar to those of alcohols oxidation, both using visible light and carbon nitride as a catalyst, the two reactions actually proceed via different mechanisms. This study also demonstrates, visible light induced heterogeneous auto-tandem catalysis, coupling the oxidation and subsequent acetalization of alcohols in a single chemical process. This green strategy can be applicable to a wide variety of organic photo-induced synthesis.
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Pyrgiotakis, Georgios. "Titania carbon nanotube composites for enhanced photocatalysis". [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013482.
Testo completo
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Li, Zizhen. "Development of Two Dimensional Materials in Photocatalysis". Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39507.
Testo completoAbstract (sommario):
Photocatalysis is a process to convert light energy into chemical energies. This advanced process has been extensively applied in different areas, such as water splitting to evolve hydrogen, organic/ inorganic pollutants decomposition, artificial photosynthesis (CO2 reduction), disinfection, heavy metal recovery, organic synthesis and nitrogen fixation (reduction). The difficulty for photocatalysis applied in practical is primarily due to the low quantum yield as for the high recombination of photogenerated charge carriers. Various strategies have been implemented to overcome these challenges. As recently developed advanced materials, two dimensional materials have attracted lots of attentions as for their superiorities such as large specific surface area and high conductivity. These advantages for two dimensional materials make them be promising cocatalysts in enhance catalytic activity. In this thesis, various two dimensional materials (such as MoS2, SnS, BN as well as C3N4) other than graphene were prepared and investigated in the promotion of photocatalytic activity. Specifically, the focus of present work is on two dimensional materials enhanced photocatalysis in environmental remediation, including organic pollutants detoxification as well as bacteria inactivation. It was found that two dimensional materials, including MoS2, SnS, BN, may be excellent candidates as cocatalysts to enhanced visible-light-driven photocatalytic activity. And g-C3N4 as an effective photocatalyst exhibited excellent photocatalytic oxidation activity, and its activity can be further enhanced with surface modification by hydroxyl functional groups (a modification method reported in the thesis). Suggestions for future work were also proposed in this thesis.