Rozprawy doktorskie na temat „Graphene - Photocatalysis”

The development of future electronics depends on the availability of suitable functional materials. Printed electronics, for example, relies on access to highly conductive, inexpensive and printable materials, while strong light absorption and low carrier recombination rates are demanded in photocatalysis industry. Despite all efforts to develop new materials, it still remains a challenge to have all the desirable aspects in a single material. One possible route towards novel functional materials, with improved and unprecedented physical properties, is to form composites of different selected materials. In this work, we report on hydrothermal growth and characterization of graphene/zinc oxide (GR/ZnO) nanocomposites, suited for electronics and photocatalysis application. For conductive purposes, highly Al-doped ZnO nanorods grown on graphene nanoplates (GNPs) prevent the GNPs from agglomerating and promote conductive paths between the GNPs. The effect of the ZnO nanorod morphology and GR dispersity on the nanocomposite conductivity and GR/ZnO nanorod bonding strength were investigated by conductivity measurements and optical spectroscopy. The inspected samples show that growth in high pH solutions promotes a better graphene dispersity, higher doping and enhanced bonding between the GNPs and the ZnO nanorods. Growth in low pH solutions yield samples characterized by a higher conductivity and a reduced number of surface defects. In addition, different GR/ZnO nanocomposites, decorated with plasmonic silver iodide (AgI) nanoparticles, were synthesized and analyzed for solar-driven photocatalysis. The addition of Ag/AgI generates a strong surface plasmon resonance effect involving metallic Ag0, which redshifts the optical absorption maximum into the visible light region enhancing the photocatalytic performance under solar irradiation. A wide range of characterization techniques including, electron microscopy, photoelectron spectroscopy and x-ray diffraction confirm a successful formation of photocatalysts. Our findings show that the novel proposed GR-based nanocomposites can lead to further development of efficient photocatalyst materials with applications in removal of organic pollutants, or for fabrication of large volumes of inexpensive porous conjugated GR-semiconductor composites.

Magister Scientiae - MSc (Chemistry)
Drinking water with high concentrations of inorganic and organic contaminants can cause adverse health defects. Specifically methyl orange dye is an organic water contaminant that has been known (along with others like methyl blue etc.) to have an increase in our water systems over the past few years due to increasing demand in industrial processes. It is therefore of utmost importance to remediate organic contaminants and ultimately enable prevention. The contaminants can be removed by photocatalysis. Anatase TiO2 is known for its photocatalytic degradation of environmental pollutants and photoelectro-chemical conversion of solar energy. However its application is limited since it is a wide band gap semiconductor, (Eg = 3.2 eV). The following study deals with the enhancement of the photocatalytic properties of TiO2 for remediation of organic water contaminants. The study was carried out to produce the two nanocomposites AgFe-TiO2 and AgFe-TiO2-rGO photocatalyst which purpose is to be cheap and easy to apply, with improved (fast and effective) photocatalytic degradation of methyl orange. The main objective was to decrease the band gap and to introduce intra-band gap states to absorb visible light. Modification of the TiO2 with small bandgap semiconductor, graphene and Ag- Fe nanoalloy reduced the bandgap energy for visible light absorption and photocatalytic degradation of methyl orange dye. The two composites were synthesised using sonication and chemical synthesis methods. A photocatalytic study (degradation of methyl orange dye) was carried out using a system incorporating an UV lamp source to determine the degradation of methyl orange catalysed by the synthesised photocatalysts AgFe-TiO2-rGO and AgFe-TiO2 along with UV-vis Spectroscopy. Morphological studies were carried out using HRSEM and HRTEM which determined the spherical agglomerated nature of AgFe-TiO2 and the sheet-like nature of AgFe-TiO2-rGO containing spherical agglomerants but that also contained pockets formed by the sheets of the rGO. XRD served as confirmation of the phase of TiO2 in both composites to be anatase. Analysis confirmed the formation and elemental determination of both composites. It was observed that the Band gap of TiO2 degussa decreased from 2.94 eV to 2.77 eV in the composite AgFe-TiO2. The photocatalytic reactivity of AgFe- TiO2 was an improvement from TiO2 and AgFe-TiO2-rGO based on the photocatalytic study. Therefore concluding that AgFe-TiO2 was the best catalyst to convert the dye (Orange II) into free radicals and ultimately remove the contaminant from the water compared to AgFe-TiO2-rGO.

Ce travail se résume en deux objectifs principaux. Le premier concerne l'élaboration de matériaux nanohybrides de dioxyde de titane (sous forme sphérique ou tubulaire) décoré par des allotropes de carbone (fullerène fonctionnalisé ou graphène). Le deuxième objectif consiste à l'évaluation de ces différents nanomatériaux dans la photodégradation de l'acide formique (AF) sous irradiation UV. Un effet bénéfique des allotropes de carbone sur l'activité photocatalytique des nanohybrides a été observé suite à l'augmentation de la durée de vie des paires électron-trou photogénérées. Dans un premier temps, la méthode d'élaboration et la teneur en fullerène fonctionnalisé ont été optimisées conduisant ainsi à l'élaboration de nanomatériaux révélant des propriétés photocatalytiques améliorées par rapport au TiO2 nanotube seul. Une corrélation entre les propriétés texturales, les propriétés photoélectriques et la constante de vitesse de dégradation de l'AF a été établie afin d'élucider les causes de l'amélioration de l'activité photocatalytique. Dans un second temps, une étude détaillée portant sur l'élaboration d'une nouvelle génération de nanocomposites combinant nanotubes de TiO2 et oxyde de graphène (OG) a été menée. Le degré de réduction de l'oxyde de graphène influence fortement l'activité photocatalytique. Ainsi, l'addition d'OG ou OG réduit aux nanotubes de TiO2 influence positivement les performances intrinsèques en photodégradation de l'acide formique en facilitant le transfert de photoélectrons de la bande de conduction du TiO2 vers l'oxyde de graphène. Finalement, l'étude des matériaux composites combinant l'oxyde de graphène et diverses compositions anatase/rutile a permis de mettre en évidence une synergie entre le OG et les deux phases TiO2
Two main objectives were achieved in the present work. The first objective concerns the elaboration of nanohybrid materials formed by combining titanium dioxide (in spherical or tubular form) with carbon allotropes (functionalized fullerene or graphene). The second objective consists in evaluating these different nanomaterials in the photodegradation of formic acid (FA) under UV irradiation. A beneficial effect of the different carbon allotropes on the photocatalytic activity of the resulting nanohybrids was observed and ascribed to an increased lifetime of photogenerated electron-hole pairs. In a first step, the elaboration method of functionalized fullerenes and their content were optimized leading to the development of nanomaterials showing improved photocatalytic properties compared to TiO2 nanotube alone. Textural properties, photoelectric properties and the FA degradation rate constant were correlated in order to determine the reasons for the photocatalytic activity improvement. In a second step, a detailed study about the development of a new generation of nanocomposites combining TiO2 nanotubes and graphene oxide (GO) was carried out. The degree of reduction of GO strongly influences the photocatalytic activity. Thus, the addition of reduced GO or GO to TiO2 nanotubes improves the intrinsic photodegradation performance of formic acid by facilitating the transfer of photoelectrons from the conduction band of TiO2 to graphene oxide. Finally, composite materials combining graphene oxide and various anatase/rutile compositions were analyzed showing a synergy between GO and the two TiO2 phases

Due to the combination of their electronic, optical and mechanical properties, graphene and other layered materials (GRMs) have great potential for applications such as flexible optoelectronics and energy storage. Given that GRMs can be dispersed in solvents, solution processing is a particularly interesting approach that allows large volume production with tailored properties according to the targeted applications. \par In this dissertation I investigate liquid phase exfoliation and formulation of GRMs-based inks for flexible (opto) electronics, energy and photocatalysis. First I develop a protocol for the characterization of graphene inks, based on the statistical analysis of their Raman spectra. Such a tool is essential because of the scattering of characteristics in liquid-phase exfoliated material. I then report two novel processing techniques. The first consists on the exfoliation of graphene in organic solvents by the means of $\alpha$-functionalized alkanes as stabilising agents, which allows yield by weight ($Y_W$) of $\sim 100\%$. The second is based on exfoliation of graphite by microfluidization, where the material is stabilised in aqueous solution, with concentrations up to 100g/L. Such inks are successfully deposited by blade coating, leading to films of conductivity $\sim$ 2$\cdot$10$^4$ S/m at 25$\mu$m. I then investigate the use of graphene inks in optoelectronics and energy applications: First, I investigate inkjet printed graphene as hole injection layer (HTL). The cells with graphene HTL show high long-term stability, retaining 85$\%$ of the initial fill factor after 900 hrs in damp heat conditions. I then demonstrate flexible displays with graphene-SWNTs as pixel electrode. A 4x4 inch$^2$ demonstrator is realised integrating the ink into 12,700 pixels. I investigate graphene/MoO$_3$ electrode for supercapacitors with a specific capacitance of 342 F/cm$^3$. The electrode shows high cyclic stability, preserving $\sim$96$\%$ of the initial capacitance after 10,000 cycles. I finally report the production of TiO$_2$/exfoliated graphite as efficient photocatalytic composite able to degrade $\sim$100$\%$ more model pollutant with respect to TiO$_2$.

Magister Scientiae - MSc (Chemistry)
Drinking water with high concentrations of inorganic and organic contaminants can cause adverse health defects. Specifically methyl orange dye is an organic water contaminant that has been known (along with others like methyl blue etc.) to have an increase in our water systems over the past few years due to increasing demand in industrial processes. It is therefore of utmost importance to remediate organic contaminants and ultimately enable prevention. The contaminants can be removed by photocatalysis. Anatase TiO2 is known for its photocatalytic degradation of environmental pollutants and photoelectro-chemical conversion of solar energy. However its application is limited since it is a wide band gap semiconductor, (Eg = 3.2 eV). The following study deals with the enhancement of the photocatalytic properties of TiO2 for remediation of organic water contaminants.
2021-12-31

Nanocatalysis has emerged in the last decades as an interface between homogeneous and heterogeneous catalysis, offering simple solutions to problems that conventional materials have not been able to solve. In fact, nanocatalyst design permits to obtain structures with high superficial area, reactivity and stability, and at the same time presenting good selectivity and facility of separation from reaction mixtures. In this work, we prepared hybrid structures comprising gold, palladium and silver nanoparticles (Au, Pd and Ag NPs), titanate nanosheets (TixO2), graphene oxide (GO), and partially reduced graphene oxide (prGO). We focused on bi- and tri-components hybrids, namely TixO2, M/(pr)GO and M/TixO2/(pr)GO (M = Au, Pd or Ag) and developed facile, versatile and environment-friendly preparation methods with an emphasis on control over physicochemical features such as size, shape and composition. In order to exploit the catalytic applications, we employed the reduction of 4-nitrophenol as a model reaction, followed by visible-light assisted oxidation of p-aminothiophenol (PATP). With these tests, we unraveled metal-support interactions and cooperative effects that render hybrid structures superior to their individual counterparts.
A nanocatálise surgiu nas últimas décadas como uma interface entre catálise homogênea e heterogênea, oferecendo soluções simples a problemas que os materiais convencionais não conseguiram resolver. De fato, o design de nanocatalisadores permite obter estruturas com grande área superficial, reatividade e estabilidade, e ao mesmo tempo apresentando boa seletividade e facilidade de separação de misturas reacionais. Neste trabalho apresentamos a preparação de estruturas híbridas compostas por nanopartículas de ouro, paládio e prata (Au, Pd e Ag NPs), nanofolhas de titanato (TixO2), óxido de grafeno (GO) e óxido de grafeno parcialmente reduzido (prGO). Focamos em híbridos do tipo M/TixO2, M/(pr)GO e M/TixO2/(pr)GO (M = Au, Pd ou Ag) e desenvolvemos métodos de preparação simples, versáteis e ambientalmente amigáveis, com ênfase no controle sobre tamanho, forma e composição. Para explorar as potencialidades catalíticas utilizamos a redução do 4-nitrofenol como reação modelo, e em seguida a oxidação assistida por luz do p-aminotiofenol (PATP). Com esses testes, investigamos interações metal-suporte e efeitos cooperativos que tornam as estruturas hibridas superiores a cada um dos materiais que as compõem.

Ces dernières années, les énormes progrès réalisés en nanotechnologie ainsi qu’en science des matériaux ont conduit à la préparation de nombreuses nouvelles nanoparticules sans réellement connaître l’ensemble des propriétés associées à leurs dimensions. La première partie de notre travail vise à évaluer les risques et les problèmes associés aux nanomatériaux, en termes de toxicité, en utilisant des nanoparticules de ZnO. Nous avons tout d’abord étudié la capacité de ces nanoparticules à générer des espèces réactives d’oxygènes (EROs) sous irradiation UV en utilisant trois types des quantum dots (QDs) comme modèles, ZnO, ZnO dopé avec des ions Cu2+ et ZnO avec des ions Cu2+ adsorbés à sa surface. Les trois types des QDs ont montré une forte capacité à générer des EROs mais ceux modifiés par les ions Cu2+ en périphérie sont les plus producteurs. Ces QDs inhibent également le plus fortement la croissance de la bactérie E. coli. La toxicité n’est cependant pas dépendante des EROs photo-produits ni du zinc (+2) libéré par les QDs et montre qu’un mécanisme plus complexe doit être considéré. Dans une second partie, nous avons tenté d’améliorer l’activité photocatalytique de nanobâtonnets de ZnO en les associant à de l’oxyde de graphène réduit (rGO). Des nanocomposites ZnO/rGO ont été préparés par voie solvothermale et utilisés pour la phototodégradation du colorant Orange II comme modèle de polluant. Les résultats obtenus montrent que le photocatalyseur ZnO/rGO est très efficace sous irradiation solaire ou visible et qu’il est peu sensible à des variations de pH ou à la présence de perturbateurs dans le milieu. Finalement, le photocatalyseur est très stable et peut être réutilisé plus de dix fois sans perte notable d’activité
In recent years, tremendous advances in nanotechnology and materials science have led to the synthesis of many new nanoparticles without really knowing all the properties associated with their dimensions. The first part of our work aims to evaluate the risks and problems associated with nanomaterials, in terms of toxicity, using ZnO nanoparticles. We first studied the ability of these nanoparticles to produce reactive oxygen species (ROS) under UV irradiation using three ZnO-based quantum dots (QDs) as models, ZnO, ZnO doped with Cu2+ ions and ZnO with chimisorbed Cu2+ ions at their periphery. The three QDs have a strong capacity of generating ROS but those modified with Cu2+ at their surface were found the be the highest producers. These dots were also found to inhibit more markedly the growth of the E. coli bacteria. The toxicity does neither depend on the amount of photo-generated ROS nor on the amount of Zn(+2) leaked by the QDs, thus indicating that a more complex mechanism should be considered. In a second part, we tried to improve the photocatalytic efficiency of ZnO nanorods by associating these nanomaterials with reduced graphene oxide (rGO). ZnO/rGO composites were prepared by a solvothermal method and applied for the photodegradation of Orange II used as model pollutant. Results obtained demonstrate that the ZnO/rGO photocatalyst is highly efficient under solar and under visible light irradiation and weakly sensitive to pH changes and to the presence of perturbators in the reaction medium. Finally, the photocatalyst is stable and can be reused up to ten times without significant loss of catalytic activity

De nos jours, les produits chimiques toxiques industriels ne sont pas toujours traités proprement, et leurs contaminants peuvent directement affecter la sécurité de l'eau potable. La photocatalyse, «une technologie verte» est une approche efficace et économique qui joue un rôle important dans la conversion de l'énergie solaire et la dégradation des polluants organiques. Ce manuscrit de thèse rapporte sur le développement des matériaux avancés (basés sur TiO2 et ZnO) susceptibles d'exploiter l'énergie solaire renouvelable pour résoudre les problèmes de pollution environnementale. Une partie de ce travail a été consacrée pour l’amélioration de l’activité photocatalytique du TiO2 sous lumière UV et visible. Par conséquent, les nanofibres composites de rGO/TiO2, BN/TiO2 et BN-Ag/TiO2 ont été élaborées en utilisant la technique d'électrofilage (electrospinning). La deuxième partie porte sur le ZnO, ainsi que les nanotubes multi co-centriques de ZnO/ZnAl2O4 et les nanotubes de ZnO dopés Al2O3 qui ont été synthétisés en combinant les deux techniques : dépôt de couche atomique (ALD) et electrospinning. Les propriétés morphologiques, structurelles et optiques de toutes les nanostructures synthétisées ont été étudiées par différentes techniques de caractérisations. Les résultats ont montré que les propriétés chimiques et physiques ont un effet très important sur les propriétés photocatalytiques des matériaux synthétisés. En outre, il a été constaté que l'effet de dopage conduit à une séparation de charge efficace dans le photocatalyseur, ce qui rend l’activité photocatalytique plus efficace. De plus, le méthyle orange et le bleu de méthylène ont été utilisés comme modèle de référence. Une amélioration significative et une stabilité à long terme de l’activité photocatalytique ont été observées avec les matériaux dopés comparés aux matériaux non-dopés sous lumière UV et visible. Des tests antibactériens contre Escherichia coli ont été également effectués; les résultats indiquent que BN-Ag/TiO2 présente à la fois des propriétés photocatalytiques intéressantes pour la dégradation des composés organiques et pour l'élimination des bactéries
Nowadays, industrial toxic chemicals are still not properly treated and these contaminants may directly impact the safety of drinking water. Photocatalysis “a green technology” is an effective and economical approach and plays an important role in solar energy conversion and degradation of organic pollutants. This thesis manuscript reports on developing advanced materials (based on TiO2 and ZnO) being capable of exploiting renewable solar energy for solving the environmental pollution problems. A part of this work was dedicated to improve the UV and visible light TiO2 photoresponse. Therefore, rGO/TiO2, BN/TiO2 and BN-Ag/TiO2 composties nanofibers were successfully elaborated using the electrospinning technique. The second part focused on ZnO. Novel structures of ZnO/ZnAl2O4 multi co-centric nanotubes and Al2O3 doped ZnO nanotubes were designed by combining the two techniques of atomic layer deposition (ALD) and electrospinning. The morphological, structural and optical properties of all synthesized nanostructures were investigated by several characterization techniques. The results show that the chemical and physical properties have a high impact on the photocatalytic properties of the synthesized materials. Moreover, it was found that the doping effect lead to a more efficient charge separation in the photocatalyst, which is an advantage for photocatalytic activities. In addition, methyl orange and methylene blue were used as model reference. A significant enhancement and a long-term stability in the photocatalytic activity were observed with the doped materials compared to the non-doped ones under both UV and visible light. Antibacterial tests against Escherichia coli have also been performed; the results indicate that BN-Ag/TiO2 present interesting photocatalytic properties for both organic compound degradation and bacterial removal

Zinc Oxide (ZnO) is one of the most extensively studied semiconductors because of its unique properties, namely, its wide band gap (3.37 eV) and high excitation binding energy (60 meV). These properties make ZnO a promising material for uses in a broad range of applications including sensors, catalysis and optoelectronic devices. The presented research covers a broad spectrum of these interesting nanomaterials, from their synthesis and characterization to their use as photocatalyts. A new synthetic approach for producing morphology controlled ZnO nanostructures was developed using microwave irradiation (MWI). The rapid decomposition of zinc acetate in the presence of a mixture of oleic acid (OAC) and oleylamine (OAM) results in the formation of hexagonal ZnO nanopyramids and ZnO rods of varying aspect ratios. The factors that influence the morphology of these ZnO nanostructures were investigated. Using ligand exchange, the ZnO nanostructures can be dispersed in aqueous medium, thus allowing their use as photocatalysts for the degradation of malachite green dye in water. Photocatalytic activity is studied as a function of morphology; and, the ZnO nanorods show enhanced photocatalytic activity for the degradation of the dye compared to hexagonal ZnO nanopyramids. After demonstrating the catalytic activity of these ZnO nanostructures, various ways to enhance photocatalytic activity were studied by modification of this MWI method. Photocatalytic activity is enhanced through band gap modulation and the reduction of electron-hole recombination. Several approaches were studied, which included the incorporation of Au nanoparticles, N-doping of ZnO, supporting ZnO nanostructures on reduced graphene oxide (RGO), and supporting N-doped ZnO on N-doped RGO. ZnO-based nanostructures were studied systematically through the entire process from synthesis and characterization to their use as photocatalysis. This allows for a thorough understanding of the parameters that impact these processes and their unique photocatalytic properties.

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.

The technology of semiconductor-based photocatalytic water splitting to produce hydrogen using solar energy has been considered as one of the most important approaches to solve the world energy crisis. Therefore, the development of the effective semiconductor photocatalysts has undergone considerable research. However, the traditional photocatalysts suffer from the negative effects from rapid charge recombination, which reduces the excited charges by emitting light or generating phonons. Efficient charge separation and fast charge transport, avoiding any bulk/surface recombination, are fundamentally important for photocatalytic hydrogen generation through water splitting. Here, we have introduced assembled layered materials as photocatalyst systems with their unique physicochemical properties to realize the effective charge separation and high photocatalytic activity. Using graphene as a two-dimensional supporting matrix, we have succeeded in selective anchoring of semiconductor and metal nanoparticles as separate catalytically active sites on the graphene surface. The ability of graphene to capture, transfer and store electrons and its potential to serve as a conductive support are demonstrated. The TiO₂ semiconductor/metals nanocrystals-graphene ensemble makes it possible to carry out selective catalytic processes at the separate sites and provides the potentials for applications in water splitting reactions. After demonstrating the positive role of graphene in such photocatalytic system, we then fabricate a simple but highly cooperative ensemble with CdS and MoS₂ nanocrystals dispersed on graphene sheets. It is demonstrated that CdS nanocrystals can also capture visible light energy and facilitate excited electron transfer to MoS₂ (as metal substituent) for catalytic hydrogen production via the 2-D graphene which plays a key role as an efficient electron mediator. Hexagonal multilayer MoS₂ with a layered structure in this system serves to provide active sites for hydrogen evolution by its exposed Mo edges. Hence, multilayer MoS₂ is an ideal cocatalyst of semiconductors for hydrogen generation. This crystalline-layered structure also shows semiconducting properties, however, its characteristic indirect band gap displays a poor light capture and emission ability with excited electrons and holes with different momentum. In contrast, single layer MoS₂ shows a direct band gap behavior. Our studies have clearly shown that single layer MoS₂ prepared with lithium intercalation indeed displays encouraging results in hydrogen evolution due to the direct band gap and quantum confinement effects. In addition, the exfoliated single layer MoS₂ exhibits extraordinary enhanced activity and stability in combination with the Eosin Y sensitized system when compared to those of multilayer MoS₂ and bulk MoS₂ counterparts, which is attributed to the improvement of the density of surface active sites with stronger adsorption for the Eosin Y molecules on the single layer MoS₂. In addition, this multifunctional catalyst on graphene sheet can also create adsorption sites on a defective basal surface of single layer MoS₂ through adsorption of Eosin Y where electron transfer from photoexcited Eosin Y molecule to graphene via the 2-D MoS₂ mainly takes place. Thus, the photo-generated electrons are then effectively transported to the exposed active sites of MoS₂ for the proton reduction to hydrogen molecule. It is believed the above novel assembled molecular layered systems may be applicable for a wide range of catalytic,photocatalytic and electrocatalytic reactions.

The control of environmental pollution, particularly in wastewater treatment, is one of the major concerns of the 21st century. Among the currently available pollution control technologies, photocatalysis is one of the most promising and efficient approaches to the reduction of pollutants. Graphene, a carbon nanomaterial with specific physical and chemical properties, has been reported as a promising potential new catalyst material in this field. A Bi2WO6 photocatalyst modified with graphene oxide was synthesized in a two-step hydrothermal process. Compared with pure Bi2WO6, the modified photocatalyst with 1.2 wt% graphene oxide improved photoactivity during the degradation of rhodamine-B (RhB) dye pollutant, by facilitating the dissociation of photogenerated excitons, which in turn results in more O2- radicals. XRD characterization showed that the modification of Bi2WO6 with graphene oxide does not affect its structure or morphology. The adsorption properties of graphene also contribute to the improvement of photoactivity. Other parameters such as catalyst dosage, temperature and solution pH are studied, with the aim to improve the efficiency of RhB removal.

Ce projet s’inscrit dans la contribution à l’élaboration de tenues de protection vis-à-vis d’agents chimiques de guerre : les combinaisons actuelles ont un rôle de barrière, qui stoppent le contaminant sans le dégrader, conduisant à un risque de contamination croisée accru. L’idée novatrice est de recouvrir ces textiles avec une couche intelligente multifonctionnelle et transparent associant un composé actif (TiO2, capable de photo-oxyder les composés toxiques sous irradiation à température ambiante) à un composé passif (nanostructures carbonées, permettant de stocker temporairement les produits de réaction ou le contaminant en cas de manque de lumière ou de pic de contamination). L’étude a commencé sur surfaces modèles afin d’optimiser l’association par assemblages par la méthode Layer-by-Layer (LbL) des différents éléments à savoir, TiO2 à un polymère (PDDA), à du graphène, à du charbon actif ou encore à des nanodiamants. L’efficacité photocatalytique de cette couche sur la dégradation d’un simulant gazeux du gaz moutarde a été testée. Les meilleures revêtements ont ensuite été transférés sur textile et leur efficacité évaluée sur un simulant liquide du gaz Sarin. Des études plus spécifiques ont également été menées pour comprendre l’influence des différents constituants et de l’épaisseur sur l’efficacité photocatalytique du film. Le renforcement de ces textiles fonctionnels contre des contraintes d’abrasion et de lavage a aussi été étudié, ainsi que sa régénération après tests photocatalytiques
This project is focused on the elaboration of protective suits against Chemical Warfare Agents. Indeed, the suits currently used mainly act as physical barriers, without any degradation of the toxic molecules, thus increasing cross-contamination risks.The original idea is to functionalise textile fibers with a multifunctional, multicomponent and transparent smart layer, combining active components (TiO2, for photo-oxidation of toxic agents under irradiation at room temperature) to passive components (carbon nanostructures, in order to temporary stock the reaction products or the contaminant in case of lack of irradiation or of high contamination level). The study begins on model surfaces, in order to optimise Layer-by-Layer (LbL) association of TiO2 with polymer, graphene, activated carbon, or nanodiamonds. The photocatalytic efficiency of the layer was evaluated towards the degradation of a gaseous mustard gas simulant. The best functionalisations were then transferred to textile and their photocatalytic efficiency were evaluated towards the degradation of a liquid simulant of Sarin gaz. Some detailed results were obtained in order to understand the impact of the different components and of the thickness of the films on the activity. Textiles reinforcement against abrasion and washing were also studied, as well as their regeneration after photocatalytic tests

After the Kyoto Protocol, the World Health Organization estimated in2016 that up to date one out of every nine deaths was related to outdoor/indoor air pollution[1]. As a consequence the World’s population expressed the need to have Healthier Cities and the design of new technologies to eliminate air pollutants[e.g. nitrogen oxides(NOx)and organics] by using natural sunlight, and their integration into smart cities became the centre of an ever increasing research[2]. Photocatalysts based on TiO2 are already on the market[3] and embedded in commercial products, such as cement[4]. However, they work only with the UV light λ<380nm [5], with a significant drop of performance in the visible[6]. In this work I enhanced and extend the TiO2 spectral activity by creating hybrid photocatalysts with organics (e.g perylenes), or graphene and related materials (GRM-PCs)(e.g. graphene, MoS2, WS2 and red phosphorous (RP)). We test the photocatalytic activity by monitoring the dye degradation(rhodamineB,(RhB))caused by GRM-PCs after a fixed irradiation time with respect to pristine TiO2. GRM-PCs based on TiO2 mixed with exfoliated graphite (TiO2-Gr) or with RP show ~90% higher photocatalytic activity, in terms of dye degradation, than pristine TiO2, after 20 min UV-Vis irradiation. Tests in the visible range (400<λ<800nm) how that RP is ideal for indoor applications, with a~800%improvement of photocatalytic activity with respect to TiO2, after 40min vis-light irradiation (5mW/cm2). The photocatalytic activity of TiO2-Gr is tested after mixing in an industrial concrete matrix, resulting in an increment of dye degradation of50%. These data underpin the potential of GRM-PCs for smart surfaces. In a city such as Milan, covering 15% of urban surfaces with TiO2-based cement photocatalysts would enable a reduction in pollution~50%. An efficient dispersion of the new cementitious coatings I have developed will allow to reach an abatement of the pollution of90% with2.5% surface covering. [1]http://www.who.int.[2]H.Tong,Adv.Mater,24,229(2012)[3]http://www.ti-line.net/[4]http://www.italcementigroup.com/ITA/[5]M.R.Hoffmann,Chem.Rev.,95,69(1995)[6]R.Asahi,Science,293,269,(2001)

Afin de résoudre les problèmes environnementaux et énergétiques modernes, ces dernières années ont vu le développement de catalyseurs photocataytiques capables d’utiliser la lumière solaire. En effet, les possibles applications des semiconducteurs présentant des propriétés photocatalytiques dans les domaines de la production d’hydrogène ou la dégradation de polluants organiques ont généré un grand intérêt de la part de la communauté scientifique. Actuellement, les photocatalyseurs à base de dioxyde de titane (TiO₂) et de nitrure de carbone graphitique (g-C₃N₄) sont considérés comme les matériaux les plus étudiés pour leurs faibles coûts et leurs propriétés physico-chimiques exceptionnelles. Cependant, la performance photocatalytique de ces matériaux reste encore limitée, à cause de la recombinaison rapide des porteurs de charge et et d'une absorption limitée de la lumière. En générale, malgré des caractéristiques exceptionnelles, ces matériaux ne contribuent pas significativement à la séparation de charge et l’absorption de la lumière lorsqu’ils sont produits par des méthodes conventionnelles. L'objectif de cette thèse est de développer de nouvelles voies pour la production de matériaux efficaces basés sur TiO₂ et g-C₃N₄). Nous avons d'abord préparé de la triazine (CxNy) qui fonctionne comme un co-catalyseur d'oxydation ce qui facilite la séparation des paires «électron-trou» dans le système du photocatalyseur creux de type Pt-TiO₂-CxNy. La présence simultanée de Pt et de CxNy, qui servent comme co-catalyseurs de réduction et d'oxydation, respectivement, a permis une amélioration remarquable des performances photocatalytiques du TiO₂. De plus, nous avons développé une nouvelle approche, en utilisant un procédé de combustion de sphère de carbone assisté par l’air, pour préparer du C/Pt/TiO₂ . Ce matériau possède de nombreuses propriétés uniques qui contribuent de manière significative à augmenter la séparation « électron-trou », et en conséquence, à améliorer la performance photocatalytique. Dans le but de développer un matériau qui soit capable de fonctionner sous les rayons du soleil et dans l'obscurité, nous avons développé un photocatalyseur creux à double enveloppes : le Pt-WO₃/TiO₂-Au. Ce matériau a montré non seulement une forte absorption de la lumière solaire, mais aussi une séparation des charges élevée et une haute capacité de stockage d'électrons. Par conséquent, ce type de photocatalyseurs a montré une dégradation efficace des polluants organiques, à la fois sous la lumière visible (λ ≥ 420 nm) et dans l'obscurité. En ce qui concerne le g-C₃N₄, nous avons exploité la relation entre les lacunes d’azote et les propriétés plasmoniques des nanoparticules d’or (Au). Ce type de photocatalyseur du Au/g-C₃N₄ a été préparé en présence d’alcali suivi par une post calcination. En effet, les lacunes d’azote ainsi produites permettent le renforcement des interactions entre l’or et le g-C₃N₄ et des propriétés plasmoniques de l’or. Ces caractéristiques exceptionnelles renforcent l'utilisation efficace de l’énergie solaire ainsi que la séparation des paires « électron-trou », ce qui contribuent à la performance photocatalytique pour la production d'hydrogène du photocatalyseur. Afin d’améliorer la capacité d’absorption de la lumière visible de g-C₃N₄, une nouvelle voie de synthèse dénommée « poly-alcaline » a été développée. La possibilité d’ajouter du polyéthylèneimine (PEI) et de l’hydroxyde de potassium (KOH) pour générer de nombreux centres lacunaires en azote ainsi que des groupes hydroxyles dans la structure du matériau, a été explorée afin d’optimiser l’efficacité du matériau. De telles modifications ont démontré leurs capacités à réduire la bande interdite et à provoquer plus facilement la séparation de charges améliorant ainsi les propriétés photocatalytiques du photocatalyseur vis-à-vis de la production d’hydrogène. Cette méthode ouvre donc une nouvelle voie d’avenir pour préparer des photocatalyseurs nanocomposites efficaces possédant à la fois, une forte d’absorption de la lumière et une bonne séparation de charges.
Afin de résoudre les problèmes environnementaux et énergétiques modernes, ces dernières années ont vu le développement de catalyseurs photocataytiques capables d’utiliser la lumière solaire. En effet, les possibles applications des semiconducteurs présentant des propriétés photocatalytiques dans les domaines de la production d’hydrogène ou la dégradation de polluants organiques ont généré un grand intérêt de la part de la communauté scientifique. Actuellement, les photocatalyseurs à base de dioxyde de titane (TiO₂) et de nitrure de carbone graphitique (g-C₃N₄) sont considérés comme les matériaux les plus étudiés pour leurs faibles coûts et leurs propriétés physico-chimiques exceptionnelles. Cependant, la performance photocatalytique de ces matériaux reste encore limitée, à cause de la recombinaison rapide des porteurs de charge et et d'une absorption limitée de la lumière. En générale, malgré des caractéristiques exceptionnelles, ces matériaux ne contribuent pas significativement à la séparation de charge et l’absorption de la lumière lorsqu’ils sont produits par des méthodes conventionnelles. L'objectif de cette thèse est de développer de nouvelles voies pour la production de matériaux efficaces basés sur TiO₂ et g-C₃N₄). Nous avons d'abord préparé de la triazine (CxNy) qui fonctionne comme un co-catalyseur d'oxydation ce qui facilite la séparation des paires «électron-trou» dans le système du photocatalyseur creux de type Pt-TiO₂-CxNy. La présence simultanée de Pt et de CxNy, qui servent comme co-catalyseurs de réduction et d'oxydation, respectivement, a permis une amélioration remarquable des performances photocatalytiques du TiO₂. De plus, nous avons développé une nouvelle approche, en utilisant un procédé de combustion de sphère de carbone assisté par l’air, pour préparer du C/Pt/TiO₂ . Ce matériau possède de nombreuses propriétés uniques qui contribuent de manière significative à augmenter la séparation « électron-trou », et en conséquence, à améliorer la performance photocatalytique. Dans le but de développer un matériau qui soit capable de fonctionner sous les rayons du soleil et dans l'obscurité, nous avons développé un photocatalyseur creux à double enveloppes : le Pt-WO₃/TiO₂-Au. Ce matériau a montré non seulement une forte absorption de la lumière solaire, mais aussi une séparation des charges élevée et une haute capacité de stockage d'électrons. Par conséquent, ce type de photocatalyseurs a montré une dégradation efficace des polluants organiques, à la fois sous la lumière visible (λ ≥ 420 nm) et dans l'obscurité. En ce qui concerne le g-C₃N₄, nous avons exploité la relation entre les lacunes d’azote et les propriétés plasmoniques des nanoparticules d’or (Au). Ce type de photocatalyseur du Au/g-C₃N₄ a été préparé en présence d’alcali suivi par une post calcination. En effet, les lacunes d’azote ainsi produites permettent le renforcement des interactions entre l’or et le g-C₃N₄ et des propriétés plasmoniques de l’or. Ces caractéristiques exceptionnelles renforcent l'utilisation efficace de l’énergie solaire ainsi que la séparation des paires « électron-trou », ce qui contribuent à la performance photocatalytique pour la production d'hydrogène du photocatalyseur. Afin d’améliorer la capacité d’absorption de la lumière visible de g-C₃N₄, une nouvelle voie de synthèse dénommée « poly-alcaline » a été développée. La possibilité d’ajouter du polyéthylèneimine (PEI) et de l’hydroxyde de potassium (KOH) pour générer de nombreux centres lacunaires en azote ainsi que des groupes hydroxyles dans la structure du matériau, a été explorée afin d’optimiser l’efficacité du matériau. De telles modifications ont démontré leurs capacités à réduire la bande interdite et à provoquer plus facilement la séparation de charges améliorant ainsi les propriétés photocatalytiques du photocatalyseur vis-à-vis de la production d’hydrogène. Cette méthode ouvre donc une nouvelle voie d’avenir pour préparer des photocatalyseurs nanocomposites efficaces possédant à la fois, une forte d’absorption de la lumière et une bonne séparation de charges.
The utilization of solar light-driven photocatalysts has emerged as a potential approach to deal with the serious current energy and environmental issues. Over the past decades, semiconductor-based photocatalysis has attracted an increasing attention for diverse applications including hydrogen production and the decomposition of organic pollutants. Currently, titanium dioxide (TiO₂) and graphitic carbon nitride (g-C₃N₄)-based photocatalysts have been considered as the most investigated materials because of their low cost, outstanding physical and chemical properties. However, their photocatalytic performances are still moderate owing to the fast charge carrier recombination and limited light absorption. The main target of the research presented in this thesis is to develop novel routes to prepare efficient materials based on TiO₂ and g-C₃N₄. These materials possess prominent features, which contribute to address the fast charge separation and light absorption problems. We firstly have prepared triazine (CxNy) acting as an oxidation co-catalyst, which efficiently facilitates electron-hole separation in a Pt-TiO₂-CxNy hollow photocatalyst system. The co-existence of Pt and CxNy functioning as the reduction and oxidation co-catalysts, respectively, has remarkably enhanced the photocatalytic performance of TiO₂. Next, we have also developed a new approach employing the air- assisted carbon sphere combustion process in preparing C/Pt/TiO₂. This material possesses many salient properties that significantly boost the electron-hole separation leading to enhanced photocatalytic performance. In an attempt to design a material that can operate under sunlight and in darkness, we have introduced Pt-WO₃/TiO₂-Au double shell hollow photocatalyst. The material has shown not only strong solar light absorption but also efficient charge separation and electron storage capacity. As a result, this type of photocatalyst exhibits a high activity performance for the degradation of organic pollutants both under visible light (λ ≥ 420 nm) and in the dark. Regarding to g-C₃N₄, we have explored the relationship between nitrogen vacancies and the plasmonic properties of Au nanoparticles employing alkali associated with the post-calcination method to prepare Au/g-C₃N₄. In fact, the produced nitrogen vacancies in the structure of g-C₃N₄ essentially enhance the interaction at Au/g-C₃N₄ interface and the plasmonic properties of Au nanoparticles. These outstanding features contribute to enhance the utilization of solar light and electron-hole separation that prompt the photocatalytic performance towards hydrogen production. Finally, we have employed a novel poly-alkali route to prepare a strong visible light absorption photocatalyst-based g-C₃N₄. The co-existence of PEI and KOH, which induces numerous nitrogen vacancies and incorporated hydroxyl groups in the structure of the resulted material, has been explored for the first time. These modifications have been proved to narrow the bandgap and facilitate the charge separation leading to enhance the solar light-driven hydrogen production. This method also opens up a new approach to prepare efficient nanocomposite photocatalysts possessing both strong light absorption and good charge separation.
The utilization of solar light-driven photocatalysts has emerged as a potential approach to deal with the serious current energy and environmental issues. Over the past decades, semiconductor-based photocatalysis has attracted an increasing attention for diverse applications including hydrogen production and the decomposition of organic pollutants. Currently, titanium dioxide (TiO₂) and graphitic carbon nitride (g-C₃N₄)-based photocatalysts have been considered as the most investigated materials because of their low cost, outstanding physical and chemical properties. However, their photocatalytic performances are still moderate owing to the fast charge carrier recombination and limited light absorption. The main target of the research presented in this thesis is to develop novel routes to prepare efficient materials based on TiO₂ and g-C₃N₄. These materials possess prominent features, which contribute to address the fast charge separation and light absorption problems. We firstly have prepared triazine (CxNy) acting as an oxidation co-catalyst, which efficiently facilitates electron-hole separation in a Pt-TiO₂-CxNy hollow photocatalyst system. The co-existence of Pt and CxNy functioning as the reduction and oxidation co-catalysts, respectively, has remarkably enhanced the photocatalytic performance of TiO₂. Next, we have also developed a new approach employing the air- assisted carbon sphere combustion process in preparing C/Pt/TiO₂. This material possesses many salient properties that significantly boost the electron-hole separation leading to enhanced photocatalytic performance. In an attempt to design a material that can operate under sunlight and in darkness, we have introduced Pt-WO₃/TiO₂-Au double shell hollow photocatalyst. The material has shown not only strong solar light absorption but also efficient charge separation and electron storage capacity. As a result, this type of photocatalyst exhibits a high activity performance for the degradation of organic pollutants both under visible light (λ ≥ 420 nm) and in the dark. Regarding to g-C₃N₄, we have explored the relationship between nitrogen vacancies and the plasmonic properties of Au nanoparticles employing alkali associated with the post-calcination method to prepare Au/g-C₃N₄. In fact, the produced nitrogen vacancies in the structure of g-C₃N₄ essentially enhance the interaction at Au/g-C₃N₄ interface and the plasmonic properties of Au nanoparticles. These outstanding features contribute to enhance the utilization of solar light and electron-hole separation that prompt the photocatalytic performance towards hydrogen production. Finally, we have employed a novel poly-alkali route to prepare a strong visible light absorption photocatalyst-based g-C₃N₄. The co-existence of PEI and KOH, which induces numerous nitrogen vacancies and incorporated hydroxyl groups in the structure of the resulted material, has been explored for the first time. These modifications have been proved to narrow the bandgap and facilitate the charge separation leading to enhance the solar light-driven hydrogen production. This method also opens up a new approach to prepare efficient nanocomposite photocatalysts possessing both strong light absorption and good charge separation.

This thesis consists of two research problems in the water decontamination area. In the first work, the main focus is to understand the structure and photocatalytic activity of titanium dioxide with graphene (G-TiO2) which is synthesized by using sol-gel method. The photocatalytic activity of TiO2 is limited by the short electron hole pair recombination time. Graphene, with high specific surface area and unique electronic properties, can be used as a good support for TiO2 to enhance the photocatalytic activity. The obtained G-TiO2 photocatalysts has been characterized by X-Ray Diffraction (XRD), Raman Spectroscopy, Transmission Electron Microscopy (TEM), FTIR Spectroscopy and Ultraviolet visible (UV-vis) Spectroscopy. This prepared G-TiO2 nanocomposite exhibited excellent photocatalysis degradation on methyl orange (MO) under irradiation of simulated sunlight. Such enthralling photocatalyst may find substantial applications in various fields. The primary objective of the second work is to understand the nanocomposite structure of SiO2 coated over graphene (G) nanoplatelets. An attempt has been made to synthesize G-SiO2 nanocomposite using sol-gel technique. The G-SiO2 nanocomposite is characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy, FTIR spectroscopy, and Electrochemical and Electrical measurement technique, respectively. In this work, G-SiO2 nanoparticles with the water containing salts of zinc is added, and allowed to settle in water. The ZnCl2 ix concentration displays a whitish color solution which has turned to colorless within one or two hours of treatment with G-SiO2 nanocomposites. The presence of heavy metal is tested using electrochemical cyclic voltammetry (CV) technique. The CV measurement on the water treated with G-SiO2 has been tested for several days to understand the presence of heavy metals in water. Interestingly, the near complete separation has been observed by treating the heavy metal contaminated water sample for one to two days in presence of G-SiO2 nanoparticles. The redox potential observed for the heavy metal has been found to diminish as a function of treatment with respect to time, and no redox peak is observed after the treatment for four to five days. Further test using EDS measurement indicates that the heavy metal ions are observed within the G-SiO2 nanocomposite. The recovery of G-SiO2 nanocomposite is obtained by washing using deionized water. Our experimental finding indicates that the G-SiO2 nanocomposite could be exploited for potential heavy metals cleaning from waste or drinking water.

This master thesis deals with the topic of alternative production of hydrogen as the energy carrier of the future. The primary focus is on the production of hydrogen based on photocatalytical water splitting in the presence of semiconductor materials (especially modified and unmodified TiO2). The aim of the thesis is a synthesis of nanostructured oxide, graphene/graphene oxide particles and its composites, and a study of its structures and photocatalytical properties regarding photolysis of water. Products of the syntheses are described from the point of view of phase composition, surface area and photocatalytical activity. The main output of the thesis is a discussion of the influence of alkaline complex forming reagents on the hydrothermal low-temperature synthesis of biphasic TiO2, and a study of the influence of graphene/graphene oxide modification on photocatalytical activity of biphasic TiO2.

La società moderna è in gran parte fondata sulle infrastrutture che garantiscono la fornitura di beni, trasporti e mezzi di comunicazione. La loro salvaguardia e il risparmio delle risorse necessarie per il loro funzionamento è di crescente importanza per l’Ingegneria civile. Per questo motivo, la ricerca sui materiali da costruzione si sta concentrando sul riutilizzo di sottoprodotti industriali riciclati, per un’industria edilizia più sostenibile. L’Ingegneria dei materiali, grazie al recente sviluppo di nanomateriali ad alte prestazioni, propone molteplici spunti per la realizzazione di materiali strutturali multifunzionali. La presente ricerca mira a sviluppare compositi multifunzionali a base di leganti idraulici, con l'aggiunta di filler e fibre a base di carbonio di origine riciclata, ottenuti da sottoprodotti industriali. Sono stati studiati i miglioramenti in termini di resistenze meccaniche e di durabilità, nonché le loro proprietà disinquinanti e fotocatalitiche. Le proprietà elettriche delle miscele sono state studiate, per la valutazione delle capacità di schermatura delle interferenze elettromagnetiche delle aggiunte, e come base di studio per lo sviluppo di materiali auto-sensibili per il monitoraggio strutturale. Sono state realizzate paste e malte contenenti grafene o altri filler a base di carbonio di origine riciclata (da 0.25 a 4% sul peso del legante) e fibre di carbonio (da 0.05 a 1.6% sul volume della miscela). Sui composti sono stati eseguiti test di resistenza meccanica e durabilità, nonché test di adsorbimento degli inquinanti, di fotocatalitisi e di resistività elettrica. La sensibilità elettrica alla deformazione è stata valutata misurando la variazione percentuale della resistività su provini soggetti a carichi di compressione semi-statici. I risultati mostrano che l’aggiunta di filler a base di carbonio riciclati porta a un raffinamento della microstruttura della matrice e a un incremento delle resistenze meccaniche, nonché a un decremento della permeabilità all’acqua. L’aggiunta di micro-fibre di carbonio riciclate porta a un incremento delle resistenze meccaniche a flessione, e a un notevole aumento della conducibilità elettrica (di svariati ordini di grandezza, rispetto ai tradizionali materiali cementizi).
Today's society is largely based on infrastructures that guarantee goods, transport and communication networks. Their safeguarding and saving of resources for their operation is becoming increasingly important in the field of building engineering. For this reason, research on building materials is increasingly focused on the re-use of recycled industrial by-products, for a more sustainable construction industry. Materials engineering, thanks to the development of high performance nanomaterials, offers several ideas for the construction of multifunctional building materials. The present research aims to develop multifunctional hydraulic binder-based composite with the addition of recycled carbon-based fillers and fibers obtained from industrial by-products. The enhancement of mechanical strength and durability of the composites have been studied, together with their de-polluting and photocatalytic properties. The electrical properties of the mixtures have been studied to analyze the Electromagnetic interference shielding capability of carbon-based admixtures, and to provide a basis for the development of strain-sensing materials for structural health monitoring. Pastes and mortars containing graphene or other commercial and recycled carbon-based fillers (from 0.25 to 4.0% on binder weight) and fibers (from 0.05 to 1.6% by mixture volume) were realized. Tests of mechanical resistance and durability were performed on the mixtures, together with test of pollutants adsorption, photocatalysis and electrical resistivity. Strain-sensitivity has been evaluated by measuring the fractional change in resistivity of the specimens subjected to quasi-static compressive loads. Results show that the addition of recycled carbon-based fillers leads to a refinement of the matrix microstructure, increasing the mechanical strength and decreasing the water permeability. The addition of recycled carbon micro-fibers leads to an increase in flexural strengths and to a noticeable increase in electrical conductivity (up to several orders of magnitude compared to the traditional cementitious materials).

碩士
國立高雄第一科技大學
環境與安全衛生工程系碩士班
105
This study investigated liquid-phase photocatalysis of sulfadiazine(SDZ) by both titanium dioxide (TiO2) and graphene doped TiO2 (GR/TiO2) thin-film. The thin-film photocatalysts were prepared with an electrophoretic deposition (EPD) technique by immobilizing P-25 TiO2, with various amount of GR, onto pure titanium (Ti) metal plates. This study explored the effects of preparation recipes on the photocatalytic activities of prepared samples, which were determined by the degradation rate of SDZ assisted by the prepared samples irradiated with a near-UV light. Several preparation parameters including applied DC biases (15~35 V), and terminal calcination temperatures (250~450℃) for the samples were evaluated. The study also used SEM and XRD to identify surface morphology, and crystal phase of prepared samples. Selected photocatalysts with better activities were further used for conducting SDZ photocatalytic degradation tests in variation pH levels and light sources. The results showed the photocatalysis of SDZ following pseudo first-order reaction kinetics. A better photocatalytic activities of prepared samples were achieved when the they were prepared with calcined in a 450℃ oven. Among them, TG0.5 photocatalyst has the highest activity (k = 0.348 hr-1), which is 13.7 % higher than that of TiO2 photocatalyst. In addition, the effect of EPD of DC biases on the degradation rate of SDZ, the photocatalytic activity of TiO2 increases with the increase of EPD of DC biases, with the highest activity at 35 V. The TG series of photocatalyst, it will be in a EPD of DC biases, with the fastest response rate, which are: TG0.5 (25 V), TG1.0 (20 V), TG1.5 (20 V). Based on the above results, it can be found that the calcination temperature is 450 ℃ with the highest activity, and different series of photocatalyst also has the best EPD of DC biases, can be assembled with a high activity of the photocatalyst, in order: 450TiO2-35V, 450TG0.5-25V, 450TG1.0-20V, 450TG1.5-20V. Finally, the effects of different light sources and pH values on degradation rate of SDZ were investigated. According to the experimental results, it was found that the degradation rate was the fastest and the proportion of pollutants adsorbed by the catalyst at pH= 3. In addition, the TiO2 photocatalyst itself is very poor for the visible light absorption capacity. The experimental results show that the photocatalyst doping of graphene can not only increase the activity of the original TiO2 photocatalyst, but also increase the absorption of the visible light source. Finally, the photocatalyst prepared in this study has the highest activity in UV light and LED light with photocatalyst doped with 0.5% graphene.

碩士
國立中山大學
化學系研究所
102
Graphene has been widely studied in hybrid nanocomposites catalyst because of its unique chemical and electrical properties. However, the enhancement mechanisms in photocatalysis of graphene hybrid catalyst with respect to the number of stacked graphene sheets have not been systematically studied before. In this work, we fabricated a graphene stacking hybrid film (GSHF) comprised of controlled number of stacked graphene layer and photoactive semiconductors (TiO2, ZnO) to investigate the variation of photocatalytic activities. Three layer graphene stacked GSHF exhibits the highest dye-degradation rate constant (k = 0.002 min-1) than other GSHF. With an order of photocatalysis rate constant：3L-GSHF > 5L-GSHF > 1L-GSHF > 7L-GHSF > TiO2 (or ZnO), we found the interface properties of conductivity; surface energy and transmittance of graphene were not the main reasons to affect the photocatalytic activities. The results show that the thickness of graphene plays an predominant role in photocatalytic performance of GSHF. To verify the thickness graphene affect, we demonstrated a photo-assisted Au deposition to label the photocatalytically active sites on GSHF surface. The FE-SEM results of Au-deposited GSHF show that 3L-GSHF has the largest Au density than 1L-GSHF and 7L-GSHF. We propose that the main reason that determines photodegradation activity is graphene energy levels quantization at different stacking thickness. Enhancement factors of surface enhanced Raman spectra (SERS) confirm that 3L-GSHF has the largest amount of photocatalytic sites than 1L-GSHF or 7L-GSHF. We revealed that photocatalytic activities of graphene hybrid nanocomposites can be directly controlled by the thickness of graphene.

Increasing energy demands as well as the depletion of traditional energy sources has led to the need for the development and improvement of energy conversion and storage technologies. Concerns regarding climate change and environmental awareness has also created increased support for renewable energy and clean technology research. One technology of interest is the photocatalyst, which is a material that is able to use natural light irradiation to create electrical currents or drive useful chemical reactions. For this purpose, a strong photocatalytic material has the following properties: i) strong absorbance over a wide solar radiation spectrum; ii) high surface area for adsorbance of target species; iii) high electron efficiency characteristics such as high conductivity, long charge-carrier lifetimes, and direct pathways for electron transport; and iv) good chemical stability. All of these requirements serve to maximize the efficiency and overall output of the device, and are a means of overcoming the performance hurdle required for the commercialization of various energy conversion technologies. Unfortunately, current photocatalytic materials suffer from small absorbance windows and high recombination rates which greatly reduce the conversion efficiency of the catalyst. Titanium dioxide (TiO2), the most well-known and widely used photocatalyst, can only absorb light within the ultraviolet (UV) range – which accounts for only a small fraction of the entire solar spectrum. For this reason, the majority of recent research has been directed toward producing photocatalysts that are able to absorb light within the visible and infrared range in order to maximize the amount of light absorbed in the solar spectrum. Other research is also being conducted to increase electrical conductivity and charge-carrier separation to further increase conversion efficiency. It is hoped that these two major problems surrounding photocatalysis can be solved by using novel functional nanomaterials. Nanomaterials can be synthesized using three main techniques: crystal structuring, doping, and heterostructuring. By controlling the structure of the crystal, materials of different phase, morphology, and exposed crystal facets can be synthesized. These are important for controlling the electronic properties and surface reactivity of the photocatalyst. Doping is the act of introducing impurities into a material in order to modify its band structure and create a red shift in light absorption. Lastly, heterostructuring is a method used to combine different photocatalysts or introduce co-catalysts in order to widen the range of absorption, encourage charge separation, or both. Many novel photocatalytic materials have been synthesized using these techniques. However, the next-generation photocatalytic material has remained elusive due to the high cost of production and complexity of synthesis. This thesis proposes a novel photocatalytic material that can be used in photocatalyzed waste-water remediation. Graphene-wrapped hierarchical TiO2 nanoflowers (G-TiO2) are synthesized using a facile synthesis method. TiO2 is a material of particular interest due to its chemical and photo-corrosion stability, high redox potential, strong electronic properties, and relative non-toxicity. Hierarchical structures are highly desired because they are able to achieve both high surface area and high conductivities. Graphene hybridization is a popular method for creating composites with highly conductive networks and highly adsorptive surfaces. To the best of my knowledge, the hybridization of graphene on hierarchical TiO2 structures without pre-functionalization of TiO2 has not yet been demonstrated in literature. Therefore, it is proposed that the use of such a material would greatly simplify the synthesis process and enhance the overall photocatalytic performance of TiO2 over that of commercial TiO2 photocatalysts. In the first study, hierarchical TiO2 nanoflowers are synthesized using a solvothermal reaction. It is then shown that under UV irradiation, the hierarchical TiO2 material is able to outperform commercial TiO2 material in the photodegradation of methylene blue (MB). Further characterization shows that this improvement is explained by a higher electrical conductivity, and exists in spite of having a lower specific surface area compared to the commercial material. In the second study, G-TiO2 is synthesized by mixing hierarchical TiO2 nanoflowers with graphene oxide (GO) and reducing GO in a hydrothermal reaction. Photocatalytic tests show that this hybridization further improves the performance of the hierarchical TiO2. Further studies reveal that an optimal graphene loading of 5 wt% is desired in order to achieve the higher rate of MB decomposition, and greatly outperforms P25 in this task. Characterization shows that G-TiO2 composites have increased specific surface area and electrical conductivity compared to the hierarchical TiO2 nanoflower. It is believed that this work will provide a simple and efficient avenue for synthesizing graphene–TiO2 composites with greatly improved photocatalytic activity. This work may also find use in other photocatalytic applications such as chemical deconstruction and manufacturing, hydrogen production, solar cells, and solar enhanced fuel cells.

碩士
國立中興大學
材料科學與工程學系所
105
Graphene has attracted much attention because it has lower resistivity and larger thermal conductivity comparing with silver and diamond. In general, the formation of graphene is using chemical vapor deposition method. Several researches reported that graphene layer can be formed by the chemical reduction of graphene oxide (GO). However, the chemical reduction method will cause environment pollution. In this study, the graphene films were fabricated by photocatalytic reduction of GO. Silicon-nanowire-array photocatalysts formed by metal-assisted chemical etching were immersed into the solution of GO in water and photocatalytic reduction process carried out under white light irradiation. The results show that large area and continuous graphene films were formed on the top of silicon nanowire arrays by photocatalytic reduction of GO. The coverage area and thickness of graphene depended on the morphology of silicon nanowire array, irradiation time and the concentration of GO solution. A graphene film with about 4 nm in thickness and a coverage rate of 88％ was achieved using silicon nanowire array formed by 24 nm Ag film-assisted chemical etching, the irradiation time of 4 hours and the GO solution concertration of 0.1 mg/ml. The sheet resistance was 1.49×103 Ω/□. The ferromagnetism property at room temperature was observed. The graphene films can be transferred from the silicon-nanowire-array photocatalysts to the target substrates using thermal release tapes.

碩士
國立臺灣海洋大學
光電科學研究所
102
In this study , we used hydrothermal reaction to grow the titanium oxide　nanostructure for photocatalysis reaction . For improving the efficiency of photocatalysis reaction with the photocatalyst, we combined the reduce grapheme oxide (rGO) which has superior conductivity to upgrade the photocatalysis reaction of titanium oxide .Next , we used Silver mirror reaction to coat silver nanoparticles on the rGO-TiO2, which can promote the efficiency of the photocatalyst by surface plasmon resonance(SPR) between silver nanoparticles and TiO2 . Because the silver nanoparticles coated on TiO2 , which can extend the optical absorption to the visible region and increasing the number of photoexcited electrons. 　　After the photocatalyst synthesized successfully , we confirmed it by Raman spectrum、Fourier transform infrared spectroscopy、UV-Vis spectrum、SEM、XRD、XPS. 　　Finally we put the photocatalyst into Methyl blue solution for phtocatalysis experiment. The results of experiment shows the Methyl blue solution was decomposed by the photocatalyst successfullyand the efficiency is better than other three photocatalyst .

碩士
國立高雄科技大學
機械工程系
107
The semiconductor oxide and the metal oxide semiconductor material are prepared by the electrospinning method, and the photocatalytic decomposition of methylene blue (MB) is carried out by using a self-made photocatalyst device. High-resolution scanning electron microscopy, transmission electron microscopy, and X-film diffractometer were used to investigate the structural properties and surface morphology of the material. The topic of this paper is to element with a tin oxide (TiO2) nanofiber structure, and discuss the optimal parameters for the production of tin oxide nanofibers using electrostatic spinning process technology, and doping with silver nitrate and graphene oxide at different concentrations. Formation of TiO2/Ag and TiO2/GO heterostructures, respectively exploring the influence of different materials after annealing temperature. Under the irradiation of ultraviolet light and visible light, the TiO2/Ag composite photocatalyst material exhibited better photocatalytic efficiency than pure TiO2 photocatalyst and improved the degradation rate by 50%. Finally, the study investigated the catalytic properties of TiO2/Go in ultraviolet light and visible light. The optimum doping ratio was 7wt% graphene oxide, which effectively improved the degradation rate by 42%.

碩士
國立臺北科技大學
化學工程研究所
104
We have fabricated different composite modified electrdoes for application to electrochemical sensors, biosensors and photocatalysis. For instance, in the fisrt part we describe the use of a nanocomposite consisting of graphene and β-cyclodextrin (β-CD) which was used to modify a glassy carbon electrode (GCE) to serve as a matrix for immobilization of hemoglobin (Hb). The composite was characterized by scanning electron microscopy (SEM), Ultraviolet-visible spectroscopy (UV-vis) and Fourier-transform infrared (FTIR) spectroscopy. The modified electrode displays an enhanced and well-defined reversible peaks for the heme protein at a formal potential of -0.284 V (vs. Ag/AgCl). The direct electrochemistry of Hb is strongly enhanced at this modified electrode compared to electrodes not modified with graphene or β-CD. The heterogeneous electron transfer rate constant (Ks) is 3.18 ± 0.7 s‾¹ which indicates fast electron transfer. The biosensor exhibits excellent electrocatalytic activity towards the reduction of bromate, with a linear amperometric response in the 0.1 to 177 μM concentration range at a working voltage of -0.33 V. The sensitivity is 3.39 µA µM‾¹ cm‾², and the detection limit (LOD) is 33 nM. The biosensor is fast, selective, well repeatable and reproducible, and therefore represents a viable platform for sensing bromate in aqueous samples. The part II deals with the fabrication of novel and sensitive amperometric sensor for chlorpromazine (CPZ) based on the reduced graphene oxide (RGO) and polydopamine (PDA) composite modified glassy carbon electrode (GCE). The RGO@PDA composite was prepared by the electrochemical reduction of graphene oxide (GO) and PDA composite. The resulting composite was further characterized by SEM, Raman and FTIR spectroscopy. The RGO@PDA composite modified electrode shows an excellent electro-oxidation behaviour to CPZ when compared with other modified electrodes such as GO, RGO and GO@PDA. An amperometric i-t method was used for the determination of CPZ and shows that the RGO@PDA composite could detect the CPZ in the linear ranging from 0.03 to 967.6 µM. The sensor exhibits a low LOD of 0.0018 µM with the analytical sensitivity of 3.74 µA µM–1 cm–2. The RGO@PDA composite shows its high selectivity in the presence of other potentially interfering drugs such as metronidazole, phenobarbital, chlorpheniramine maleate, pyridoxine and riboflavin. The fabricated sensor has also showed an appropriate recovery towards CPZ in the pharmaceutical tablets. In the final part (Part III) we have investigated the phtocatalytic activity of as-synthesized silver molybdate (Ag2MoO4) modified electrode. The potato-like Ag2MoO4 microstructure was synthesized through simple hydrothermal treatment with the assistance of urea. The successful formation of Ag2MoO4 was confirmed by various analytical and spectroscopic techniques such as X-ray diffraction, FTIR, Raman, SEM, Energy dispersive x-ray and X-ray photoelectron spectroscopies. Furthermore, the as-prepared Ag2MoO4 was used as a photocatalyst for the degradation of ciprofloxacin (CIP) as well as an electrochemical sensor for the detection of H2O2, for the first time. The obtained UV-vis spectroscopy results demonstrate that, Ag2MoO4 had excellent reusable photocatalytic activity for the degradation CIP under Ultraviolet-light illumination possess great degradation rate of above 98% after 40 min. Moreover, the cyclic voltammetry and amperometry results revealed that Ag2MoO4 modified GCE showed good electrocatalytic performance for the detection of H2O2 with good linear range and LOD are 0.04 to 240 µM, and 0.03 µM, respectively. It also exhibit high selectivity of H2O2 in the presence of range of biological interferences such as catechol, fructose, lactose, sucrose, glucose, hydroquinone, ascorbic acid, uric acid, dopamine, and epinephrine. Hence, the potato-like Ag2MoO4 microstructure has great practical applicability for use as wastewater treatment and electrochemical detection of H2O2 in real samples.

碩士
國立高雄應用科技大學
化學工程與材料工程系博碩士班
104
Photocatalysis can be effectively applied in removing the pollutants in the water, and it has the significant problem that need to be solved. As a result, this research mainly focused on synthesizing magnetic photocatalysts which can effectively remove organic pollutants in the water under visible light. The organic pollutants (Methyl orange, MO) can be transformed into CO2¬ and H2O, etc. The used photocatalysts can be recycled by magnetic process. The octahedron, hollow sphere, and dodecahedron Cu-2O/graphene were synthesized via sol-gel and solvothermal methods. Then dope Cu2O onto high electron conductivity of graphene oxide (rGO) to reduce recombination electrons and electron holes. As a result, it has the most effective degradation efficiency when combine with 1% graphene oxide. Besides, the results demonstrate that Cu2O dodecahedra with exposed {110} facets with more dagling “Cu” atoms possesses higher activity than those with hollow sphere {110} & {111} facets and Octahedral {111} facets. We synthesized magnetic core-shell materials (Fe3O4@SiO2), follow by adding Cu2O and graphene oxide that can produce high saturation magnetization and photocatalysis performance of magnetic photocatalysts. Magnetic photocatalysts, dodecahedron Cu¬2O/rGO have removal efficiency of 98% MO in two hours under visible light, after several cycles still retains 85.17%.

碩士
國立暨南國際大學
應用材料及光電工程學系
104
Abstract In this study, photocatalytic reduction and ion exchange methods were employed to fabricate the ternary nanocomposite photocatalysts of Ag-TiO2-graphene (ATG) and Ag3PO4-TiO2-graphene oxide (APTGO), respectively. The contents of graphene and Ag in ATG were adjusted, and the molar ratio of Ag3PO4 to TiO2 in APTGO was tuned. The properties and photocatalytic activity of the nanocomposites were examined, and their photodegradation mechanisms were explored. When an ATG had more graphene, light absorption and charge transport were enhanced, leading to higher efficiencies of photodegradation and hydrogen production from water splitting. It was proved that the optimum ratio between TiO2 and graphene was 5:1. More Ag contributed to light absorption and reduced impedance. The surface enhanced Raman scattering (SERS) effect induced by Ag nanoparticles was favorable to photocatalytic activity. However, excess Ag decreased the specific surfacearea of an ATG photocatalyst, and lower light absorption and increased recombination probability were thereby caused. Accordingly, an appropriate content of Ag was required so as to obtain more effective photocatalysis. Moreover, it was found that the optimum Ag content was different for a different mixing ratio between TiO2 and graphene. The best photocatalytic efficiency of ATG (max. hydrogen production 4233 mole g-1 and QE = 26.2 %) was achieved when graphene and Ag both existed optimal contens. More TiO2 in APTGO improved light absorption but caused a larger impedance and inferior charge transport. Excess TiO2 distributed over the surfaces of Ag3PO4 and graphene oxide decreased the specific surface area and thus lower light absorbance of an APTGO photocatalyst. It has been evidenced that an appropriate TiO2 content was beneficial to enhance photocatalytic performance. Larger and wider light absorption and thereby highest photocatalytic efficiency of APTGO (max. hydrogen production 1312 mole g-1 and QE = 8.13 %) were achieved when the molar ratio of Ag3PO4 to TiO2 was 0.6.

碩士
國立中興大學
化學工程學系所
102
In this thesis, the purpose is to study the photocatalytic activity of titania photocatalyst, which is supported by platinum and doped with graphene nonoplatelet (GNP). The preparation of the novel photocatlyst is as follows：sythesis of titania by sol-gel method, deposition of platinum by photoreduction, then doping with GNP. The photocatalytic activity of the catalyst is tested by photodegadation of methyl orange using quartz glass reactor under the UV light illumination. The parameters of catalyst preparation include temperature of calcination, amount of water, kinds and ratios of dispersant, weight of CTMAB addition, weight of GNP doping, loading of platinum, and sources of UV light for photoreduction of platinum. Operating conditions in photocatalytic reaction included initial concentration of methyl orange solution, wavelength of illumination and photodegradation of methylene blue. The results revealed that the doping of 1 wt% graphene-nanoplatelet and loading of 1wt% platinum in titania effectively improve the dispersion and reaction activity of the catalyst. The particle size of platinum metal is very small to be 2-3 nm and distributed uniformly. Under 150 min of the UV light illumination, the conversion of photodegradation of methyl orange solution is above 88 %. The photodegradation of the methyl orange solution is also performed by the catalyst Pt(1)( TiO2(99)GNP(1))(99) under irradiation of UV light (365 nm), and the conversion of the degradation is 91.4 % in 150 min. The reaction rate constant for photodegradation of the methylene blue solution under irradiation of visible light (420 nm), is 1.2 min-1 which is 1.3 times of the catalyst Pt(1)TiO2(99) without doping GNP, showing the high catalytic efficiency of Pt(1)( TiO2(99)GNP(1))(99).

碩士
國立東華大學
材料科學與工程學系
107
In this study, the graphite oxide(GO) prepared by improved Hummer's method was used as the O2 evolution photocatalyst, and the H2 evolution photocatalyst was Rh doped SrTiO3 (denoted as SrTiO3:Rh) with Ru nanoparticle as cocatalyst. All the catalysts were characterized by X-ray diffraction spectrometer (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible Spectrophotometer (UV-vis), Fourier transform infrared spectrometer (FT-IR), Raman spectrometer (Raman) and X-ray photoelectron spectroscopy (XPS) to analyze the physical, chemical and surface properties. The gas-evolution activity of photocatalyst is tested by gas chromatograph (GC). The Z-scheme is a two-photocatalyst system for photocatalytic overall water splitting. It is using H2 evolution catalyst combined with O2 evolution catalyst in [Co(Bpy)3]2+/3+ aqueous solution as redox mediator. The photocatalyst is photocatalyzed by ultraviolet light/visible light to generate H2 and O2. The activity of the photocatalyst in water splitting reaction is discussed in three parts. First, compare the activity of different grams and preparation of graphite oxide in the oxidation reaction.The highest of photoactivity O2 evolution photocatalyst is 0.02 g of Goc (O2: 3141.38μmole g-1 h-1).The second section is the H2 evolution reaction of Ru/SrTiO3:Rh in [Co(Bpy)3]2+(aq), wherein 0.05g has the highest hydrogen production activity (H2: 287.87μmole g-1 h-1).Last, the combination of Ru/SrTiO3:Rh and graphite oxide in different ratio in the Z-scheme system for the study of the gas evolution reaction. The photocatalytic overall water evolution reaction of 0.05 g of GO and 0.05 g of Ru/SrTiO3:Rh combined with [Co(Bpy)3]2+(aq) has the highest activity (H2:505.26、O2:786.11 (μmole g-1 h-1)).

碩士
逢甲大學
化學工程學系
104
In this study, CuS-ZnS1-xOx/g-C3N4 organic-inorganic heterostructured nanocomposite which was prepared by means of a hydrothermal method, exhibited good activities for photocatalytic hydrogen production. Effects of the ZnS1-xOx process condition, Cu(NO3)2 precursor concentration and g-C3N4 content on the morphology, crystalline properties, optical property, surface chemistry and photocurrent were investigated by using field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD), field-emission transmission electron microscopy (FETEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (DRS), Photoluminescence (PL), electrochemistry impedance spectroscopy (EIS), photocurrent response, and hydrogen production tests. The optimized photocatalytic H2 production rates of ZC25N5I photocatalyst under UV light irradiation reach 12200 μmol g-1h-1. CuS-ZnS1-xOx/g-C3N4 photocatalysts have excellent properties, including decreased bandgap and enhanced light absorption due to CuS helping and increased specific surface area and efficient charge separation resulting from incorporation of g-C3N4. In second part, the photocatalytic reforming of glycerol to hydrogen at room temperature by zincoxysulfide, zincoxysulfide/graphene catalysts was investigated. The photocatalysts were characterized by FESEM, XRD, FETEM, XPS, DRS, EIS, PL, photoelectrochemical test, and photocatalytic H2 production tests. The photocatalytic H2 production rates of ZG5 photocatalyst in 40% glycerol solution under UV light irradiation reach 1070 μmol g-1h-1.Incorporation of graphene helps the separation of photogenerated charge through the zincoxysulfide/graphene interfaces and enhance the photocatalytic activity of the photocatalysts. The ZG5 photocatalysts improved superior activity because of increased specific surface area, efficient charge separation, and enhanced light absorption.

碩士
國立臺中教育大學
科學教育與應用學系碩士班
105
In this study, a series of the silver vanadium oxide and silver vanadium oxide composite graphene oxide (GO) are prepared using hydrothermal methods, and using the visible light as the light source of degradation of Atrazine and CV. In the experiment, first, AgNO3 、NH4VO3 and commercial GO are used as the starting material, then seperately dissolved in DI water, stirring and mixing, and using NH4OH to adjust the pH value. Then the aqueous solution is placed in a 23ml autoclave and put into an oven, and heated. The ultimate products of photocatalyst are characterized by XRD, FE-SEM-EDS, FE-TEM, FT-IR, DRS, BET, and HR-XPS. Last, using different conditions of photocatalyst to conduct the process of degradation of Atrazine and CV, investigating silver vanadium oxide and silver vanadium oxide/GO for photocatalytic efficiency. In the study, we collect that the best parameter condition of AgxVyOz is effective in the degradation of both Atrazine and Crystal Violet. Moreover, the composite of AgxVyOz and GO not only shortens the duration of degradation, but also increases the stability and the quantity of recycling of photocatalyst.

碩士
國立成功大學
環境工程學系
105
Nowadays, people spend more than 80% of time in indoor environments in modern social way of life. Therefore, indoor air quality should be paid more attention due to the indoor air pollutants impact on human health through directly chronic inhalation. Formaldehyde most often appears in the indoor environment where can be escaped from furnishing, cleaning agents and paints. And it has been confirmed to be carcinogenic to the human body. Thus, the elimination of formaldehyde is essential for improving air quality. Indoor environmental conditions are usually room temperature, high humidity and often with low concentration pollutants which are not easy to collect. Fortunately, photocatalytic oxidation is a suitable technology with low-cost, no secondary pollution and low energy consumption. Titanium dioxide is most widely used in photocatalytic applications. However, titanium dioxide absorption band is mostly in the range of ultraviolet light, this drawback limits the removal of indoor air pollution by titanium dioxide. In this study, the photocatalysts were prepared through doping sulfur, nitrogen and graphene in titanium dioxide by a solvothermal method to improve the visible light absorption of titanium dioxide. The UV-visible absorption spectrum indicates that doping of S, N and graphene can improve visible light absorption intensity and reduce the band gap. The XPS, FTIR and Raman spectra show that synthesis of the rGO/S0.05N0.1TiO2 composite produces new chemical defect and bonding by introducing oxygen-containing functional groups, further enhances the photocatalytic effect. The XRD, SEM, TEM and BET results show that crystallite sizes of rGO/S0.05N0.1TiO2 are reduced by introduction of graphene sheets. The TiO2 particles are attached to the rGO surface and interposed between the rGO layers, promoting an increase of specific surface area. rGO can enhance the overall photocatalytic efficiency due to its excellent electron transport capacity and high specific surface area, but excess rGO could shield the light. In this study, 0.1 wt% rGO is the best doping amount. The reaction rate of formaldehyde is mainly affected by water vapor concentration. Too little water vapor may reduce the generation of hydroxyl radicals; Too much water vapor may cause competitive adsorption of water with formaldehyde. Langmuir-Hinshelwood model 4 is best suited to this study, the water vapor has more effect on the formaldehyde conversion than the temperature under building room environment. Regarding the conversion mechanism was verified by FTIR, formaldehyde may be first converted to formate, then carbon monoxide, and finally carbon dioxide.

博士
國立臺灣科技大學
材料科學與工程系
102
Artificial photosynthesis is one of the solutions to solve global warming and mitigate the rising demands of energy consumption. Photocatalytic conversion of carbon dioxide (CO2) to hydrocarbons such as methanol makes possible simultaneous solar energy harvesting and CO2 reduction, resulting in solution for both the energy demands and environmental problems. This work describes a promising photocatalyst based on improved graphene oxides (iGOs), which have high photocatalytic conversion efficiency of CO2 to hydrocarbon fuels. Improved Hummer’s method has been applied to synthesize the GO based photocatalyst for the enhanced catalytic activity. The photocatalytic CO2 to methanol conversion rate on the pristine improved graphene oxide is 0.172 μmole g-1-cat. h-1 under visible light, which is four-fold higher than the pure TiO2 (P25). On the other hand, we have also synthesized a composite catalyst based on molybdenum disulfide-iGO system.The MoS2 nanosheet decorated improved graphene oxide (iGO) hybrid nanostructures are fabricated by a facial one-step hydrazine-assisted hydrothermal method. The photophysical properties of the synthesized photocatalysts have been investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), UV-Vis spectrometer, Ultraviolet photoelectron spectroscopy (UPS), cyclic voltammetry (CV), linear sweep voltammetry (LSV) and X-ray photoelectron spectroscopy (XPS). Enhanced visible light-driven activity for the CO2 photoreduction to solar fuel has been achieved. The average apparent CO2 reduction to solar fuel formation rate of MoS2 nanosheet decorated iGO composite is more than 10 times higher than the pristine iGO; or 40 times that of TiO2 (P25). The MoS2 nanosheet decorated iGO composite nanostructures makes an outstanding contribution to the excellent photocatalytic CO2 reduction.

碩士
國立中興大學
化學工程學系所
107
Photocatalytic reduction of CO2 is a promising technology to both reduces the greenhouse gas emissions and provides alternative energy sources. Here, we designed a hierarchical Z-scheme photocatalyst consists in an Ag2O/Ag/GO nanostructure, in which Ag was deposited on the GO and subsequently Ag2O was oxidized on the surface of Ag/GO. Transmission Electron Microscopy (TEM), X-ray Diffractometer (XRD), X-ray Photoelectron Spectroscopy (XPS), UV-vis Diffuse Reflectance Spectra (UV-vis DRS), Surface Area and Porosity Analyzer (BET), Fluorescence Spectrophotometer (PL), Thermogravimetric analyzer (TGA) and Fourier transform infrared spectroscopy (FTIR) analysis were applied to characterize the Ag2O/Ag/GO catalysts. In addition, the photocatalytic activities of the Ag2O/Ag/GO catalysts were evaluated by the photocatalytic reduction of CO2 to methanol. The maximum MeOH formation rate was reached at a 0.01gram of 5wt% Ag2O/Ag/GO composite catalyst and a 300 mL of 0.2 N NaOH under the UV irradiation. The results of this reaction conditions have shown the methanol formation rate of 8.6 x105μmole g-cat-1hr-1. From the results, the HRTEM image clearly indicates an intimate interface between Ag2O, Ag and GO in the composite and some lattice fringes can be clearly observed. The lattice spacing of 0.23 nm and 0.271 nm match the (111) plane of Ag and the (111) plane of Ag2O, respectively. We have proposed a possible Z-scheme mechanism based on the results. Z-scheme consists of ultrathin graphene oxide plates and Ag2O nanoparticles as photocatalysts, and Ag nanoparticle as a solid electron mediator offering a high speed charge transfer channel and leading to more efficient spatial separation of electron-hole pairs. It allows the electrons remaining in the conduction band (CB) of GO and holes in the valence band (VB) of Ag2O to possess strong reduction and oxidation capabilites, respectively, leading the Ag2O/Ag/GO to exhibit high photocatalytic reduction of CO2.

碩士
國立勤益科技大學
化工與材料工程系
102
The photocatalyst materials are usually TiO2 due to its high photocatalytic performance. This article explores the TiO2 photocatalyst modified with four different graphene modified by hydrothermal/ calcining and hydrothermal method, and various mass ratio of the graphene. (Photocatalyst composites were label as TxYC, x: weight percent, Y: graphene species, C: Calcining). Photocatalyst composites were characterized by field-emission scanning electron microscope (FESEM), X-ray diffraction(XRD), Raman spectroscopy, UV-vis diffuse reflectance spectra(UV-vis DRS), Fourier Transform infrared spectroscopy (FTIR) and photoactivity tests. The absorption spectra of the samples are shown that the narrowing of the band gap of TiO2 occurred with graphene introduction. The band gap of TiO2 is 3.08 eV, whereas the band gap of the photocatalyst composite has been slightly reduced to 2.50 eV. XRD and Raman analysis were suggested that addition of graphene cannot change crystalline structure of TiO2(Degussa, P25). FTIR spectra show that the chemical bonding between the graphene and TiO2. In photocatalytic tests, the visible light photocatalytic activity of TxGOA and TxGH1 composite are enhanced greatly on decomposition of methylene blue (MB).The photocatalytic activities of T4GOA samples are superior to that of TiO2, the methylene blue decomposition efficiency reached 100% only 30 min under UV light.

碩士
國立高雄應用科技大學
化學工程與材料工程系博碩士班
103
Recently, the sulfamethoxazole (SMX), one of the emerging contaminants in surface waters, has been detected at high frequency. SMX in the water system was a potential risk to the ecosystem balance. Unfortunately, the traditional treatment techniques can not remove SMX completely. Thus, the objective of this study is to synthesize an efficient photocatalyst for degrading emerging contaminants under visible light.The Cu2O/graphene photocatalysts were synthesized via a simple wet-chemical method by using CuSO4·5H2O and graphene oxide as precursors and ascorbic acid as reducing agent. Then, the Cu/graphene photocatalysts were obtained by reducing the Cu2O/graphene photocatalysts in H2 at 500℃. A variety of different spectroscopic and analytical techniques, such as X-ray diffraction, Raman scattering spectroscopy, UV-visible spectroscopy, X-ray photoelectron spectroscopy and transmission electron microscopy were used to characterize the physical properties of materials. Photodegrading SMX by these photocatalysts under visible light was also examined in this study. In the photodegrading experiments, it was found that the Cu/graphene photocatalysts sample (B80) has the superior visible-light response of 80% removal ratio which may be confirmed that a localized surface plasmon resonance effect of copper nanoparticles and doping graphene can enhance the photocatalytic activity under visible light irradiation.

碩士
國立成功大學
環境工程學系
104
Hydrogen peroxide (H2O2) is a clean oxidant and fuel that is desirable in many real-world applications. Current industrial manufacturing of H2O2 involves expensive, noble metal-based catalysts with high energy demand. Searching for more environmentally sustainable process for H2O2 production merits greater attention in research. In this work, the potential of graphene oxide (GO), an emerging, two-dimensional carbon-based nanomaterial, as a new photocatalyst toward H2O2 photoproduction driven by solar energy was explored. The result indicates that 〉 1 mM of H2O2 can be photoproduced within 6 h of solar irradiation even without organic electron donors present. This is particularly attractive considering that photocatalytic H2O2 production processes usually require organic electron donors. To our knowledge, the H2O2 photoproduction reported here is among the highest values in related work. O2 is needed for this process and greater yield is favorable at increased pH. The greater yield at increased pH contrasts the more rapid loss of GO’s long-term photocatalytic stability that can be attributed to greater phototransformation of GO at increased pH. Two-electron O2 reduction is the likely pathway toward H2O2 formation. The apparent quantum yields (AQYs) were also reported. The results indicate that GO is a promising photocatalyst toward H2O2 production that can be driven by renewable sunlight energy under organic electron donor-free condition.

碩士
國立臺中教育大學
科學教育與應用學系碩士在職專班
105
In this study, bismuth silicate and bismuth silicate composite graphene oxide (GO) and composite graphitic carbon nitride (g-C3N4) are prepared using autoclave hydrothermal methods. The novel heterojunctions of Bi12SiO20/GO and Bi12SiO20/g-C3N4 are fabricated by the hydrothermal method for the first time. Bismuth silicate is prepared by Bi(NO3)3 and Na2SiO3, dissolved in an 3M NaOH aqueous solution and adjusted the pH value . The aqueous solution is then transferred into a 15 mL Teflon-lined autoclave and heated to 100oC for 4 hours. Bi12SiO20/GO or Bi12SiO20/g-C3N4 is mixed in different weight ratio independently in a autoclave and heated to 100 oC for 4hours. The products are characterized by XRD, SEM-EDS, FE-TEM, HR-XPS, PL, DR-UV, BET, FT-IR, and EPR. To discuss bismuth silicate and bismuth silicate composite with graphene oxide and graphitic carbon nitride for photocatalytic efficiency, photocatalytic efficiency of the catalyst is used for the photocatalytic degradation of organic pollutants - crystal violet (CV) and 2-hydroxybenzoic acid . The measurement of crystal violet (CV) concentration, that the reaction rate constant k of Bi12SiO20 / 20wt%-GO and 5wt%-Bi12SiO20/g-C3N4 is 0.050h-1 and 0.078 h-1, respectively. This study shows that the ratio of Bi12SiO20：GO and Bi12SiO20： g-C3N4 strongly affect composite morphology, light response and photocatalytic activity.

碩士
國立中正大學
光機電整合工程研究所
105
Carbon dioxide (CO2) emission causing global warming has been a crucial issue these years. In addition to reducing the amount of greenhouse gas emission, scientists discover that photocatalytic conversion of carbon dioxide, a process of chemical reduction whereby carbon dioxide is reduced to CO2 or hydrocarbons under solar excitation, turns out to be a feasible method to solve the environmental emergency and energy shortage by reutilizing CO2 to fuels. As a result, it is very important to develop high-performance photocatalysts to enhance photocatalytic activity of CO2 conversion and further to understand the mechanism. Two-dimensional molybdenum disulfide (MoS2) not only has narrow and tunable band gap, bit its photocatalytic activity and hydrolization are also very similar to platinum (Pt), which makes it a suitable research candidate. On the other hand, a photocatalyst based on graphene has these advantages: high excellent electronic conductivity, large specific surface area, good optical transmittance, and superior chemical stability. Several researches have indicated that the characteristics of semiconductors can be changed with graphene hybrid. By analyzing the change of band gap and band position, we can have a better understanding of its mechanism and further enhancing the photocatalytic activity of CO2 reduction to solar fuels. Several photocatalytic products of MoS2/graphene hybrid are detected by gas chromatograph (GC) system comparing with pure monolayer MoS2. Quantum efficiency (QE) performance of our hybrid material is about 6 times higher than pure monolayer MoS2., which makes it an outstanding contribution to the excellent photocatalytic CO2 reduction.

碩士
國立交通大學
材料科學與工程學系
100
This work reported the one-step preparation of Cu2O/RGO nanoheterostructures with the photochemical reaction method. By modulating the concentration of GO employed in the reaction, the amount of Cu2O nanocrystals grown on RGO surface can be readily controlled. Because of the considerably high electrical conductivity of RGO, the photoexcited electrons of Cu2O would preferentially transfer to RGO, leaving positively charged holes in Cu2O to achieve charge carrier separation. Time-resolved photoluminescence spectra were collected to quantitatively analyze the electron transfer event between Cu2O and RGO and its dependence on RGO content. Among the different samples tested, Cu2O /RGO sample with RGO content of 2.0 wt% displayed the highest charge separation efficiency, consistent with the result of dye photodegradation experiment. As compared to the relevant commercial products like N-doped P-25 TiO2 and Cu2O powders, the as-synthesized Cu2O /RGO nanoheterostructures exhibited superior photocatalytic performance toward dye degradation under visible light illumination, demonstrating their potential as applied in relevant photoelectric conversion processes. The recycling test reveals that Cu2O /RGO sample could be promisingly utilized in the long-term course of photocatalysis. Furthermore, the result of performance evaluation under natural sunlight shows that the present Cu2O /RGO nanoheterostructures can be used as highly efficient photocatalysts which can effectively absorb solar spectrum for solar fuel generation.

碩士
國立雲林科技大學
化學工程與材料工程系
103
In this study, the development of new visible light photocatalyst target, hoping to enhance the incorporation of impurities in the photocatalyst efficiency in the use of visible light. Indoors general fluorescent lamp of UV energy is only 0.1 ~ 1μW, for the general photocatalyst are not sufficient to produce the decomposition of pollutants effect. Therefore, how to improve the above problem is the most important breakthrough in improving the general principle by the photocatalyst photocatalyst fast electron hole recombination question the effectiveness and increase the absorption and adsorption efficiency in the visible region. 　　In this study, sol-gel method to prepare a spinning technique with electrostatic GO/TiO2 composite photocatalyst and microfiber GO/Ag/TiO2 composite photocatalyst microfiber, which has a visible drop of Methylene Blue and Methyl Orange features and explore the different proportions of GO/TiO2 composite microfiber and GO/Ag/TiO2 composite superfine fiber properties. The use of SEM, EDS, TEM, XRD, Raman, FT-IR, TGA, BET, UV-Visible DRS to detect patterns and distribution microfiber case, crystal, elemental composition, specific surface area, visible light absorption and energy gap . Finally, solid - liquid phase of methylene blue dye and degradation of methyl orange light, visible light degrades assessment results. 　　Observed by the SEM surface patterns that GO/TiO2 and GO/Ag/TiO2 are fiber patterns, and add fiber patterns GO has a similar structure to produce more than the surface area of the cobwebs. TEM observation GO/Ag/TiO2 fiber surface distribution of Ag nanoparticles. EDS shows the percentage by weight of Ag different GO/Ag/TiO2 fibers in line with the proportion of cases expected results of its elements. BET can be made that, added to the GO is the specific surface area can be increased, but also because the import GO-Ag nano silver particles help to reduce the particle size and thus more surface area to improve the fiber. TiO2 composite photocatalyst prepared by the XRD show mainly anatase crystal mine, and added the GO will significantly wider diffraction peak production. The Raman spectra, we can clearly observe TiO2 composite photocatalyst have significant D band and G band production. UV-Visible analysis showed that the GO/TiO2 and GO/Ag/TiO2 fibers in the visible region of the absorption of a substantial energy gap and reduce the phenomenon. 　　Finally, this study conducted a series of aqueous methylene blue and methyl orange visible degradation experiments showed that adding GO/TiO2 superfine fiber 20mgGO has the best visible degradation efficiency; add in GO/Ag/TiO2 superfine fiber 0.5mgGO -2wt% Ag has the best degradation efficiency of visible light, which indicates that three-way co-heterostructure GO/Ag/TiO2 visible light microfiber with good catalytic effect.

碩士
逢甲大學
化學工程學系
103
Graphene@ZnS and polyaniline/ZnS (P-ZnS) nanoparticle were use as hydrogen production photocatalysts. In first part, ZnS nanoparticles were prepared as the core material by a solvothermal process with zinc acetate and thiourea as precursors. ZnS nanoparticles were encapsulated by polyaniline to make the composite photocatalysts. Properties of the photocatalysts were characterized by field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible diffuse reflectance spectroscopy (DRS), photoinduced current, and photocatalytic hydrogen evolution test. The photocatalytic activity of the catalysts was evaluated by splitting Na2S/Na2SO3 solution into H2. The optimized photocatalytic hydrogen production rates of P-ZnS nanoparticles reach 6430 μmol h-1 g-1, respectively. All the photocatalysts can be recycled. Recycled photocatalysts exhibit good hydrogen generation performance after being recycled for three times. In second part, ZnS which mentioned above is use as the shell which fabricate on graphene nanosheet. Ni-doped graphene@ZnS photocatalysts for photocatalytic hydrogen production was also prepared by a solvothermal method. Doped Ni helps the separation of the photon induced electron and hole pairs, hence enhances the photocatalytic activity. Energy- dispersive X-ray spectroscopy (EDX) analysis indicated that a small amount of Ni is loaded on the ZnS. Because of increased surface area of ZnS layer, enhanced separation of the photoinduced carriers by Ni-doping, and effective contact among sacrificial aqueous solution and the ZnS shell, The optimized photocatalytic hydrogen production rates of graphene@ZnS nanoparticles reach 5967 μmol h-1 g-1. And the graphene@Ni-doped ZnS nanocomposites are highly active photocatalysts for hydrogen evolution and the highest photocatalytic activity reaches 8683 μmol h－1g－1. Effects of introducing graphene, doping, and decorated ZnS on the surface chemistry, crystalline property, optical property, surface morphology, and photocatalytic hydrogen production performance were studied. Ni-doping and decorated ZnS on graphene improved the photocatalytic H2 production activity because of improved dispersing property, increased surface area, increased absorption, and enhanced transfer of photogenerated electrons. Keywords: Photocatalysts, H2 Production, ZnS, PANI, Graphene, Core-shell, ZnS, graphene, Ni2+-doping

博士
國立清華大學
化學系所
105
Developing of a simple and cost-effective strategy to diagnose and treat cancer with single and minimal dosage through noninvasive methods are highly challenging. To make such theranostic strategy effective, single light induced photothermal and photodynamic reagent with dual modal imaging capability is highly desired. Cancer has long been considered a huge threat to the world population, leading to millions of threat worldwide. Often cancer leads to weaker immune system in the body, making it easier for bacterial attacks and secondary infections. Bacterial pathogens have caused much more havoc in our lives in general and the lack of effective conventional antibiotics exposes us to a major epidemic threat. Modern therapeutics based on nanomaterials has provided various solutions due to their unconventional approach towards pathogen killing and inhibition. For cancer, recent studies on drug delivery have shown progress although limited by the system of application and delivery process and often, drugs are designed very specific to their target disease. Designing of a multifunctional nanomaterials, keeping in mind their unconventional applications is a challenging task. Our major concern must be to employ nanomaterials for a potential breakthrough in the field of biomedicine and therapy. Modern therapeutics demand for specialized delivery system while rest are limited due to their insolubility in water. Graphene, considered a wonder material has emerged as a promising material owing to its fascinating properties in superior electronics, thermal stability, specific surface areas, optical and mechanical, as well as good conductivity. Apart from the other intriguing properties, graphene is also a biocompatible material, unlike its other counter parts like fullerene and carbon nanotubes (CNTs). Among the globally prevalent and further emanating risks of recently engineered nanomaterials, organic pollutants, microbial infections, etc., dumping of dyes in ground water thereby contaminating the water supply is the most notable. Untreated Industrial wastes containing dyes are released on our grounds and water bodies, which demands for a more strategic and efficient water treatment methods. For such concerning problems, we have designed a graphene based nanocomposite for effectively destroying dyes and organic pollutants, like Rhodamine B and bacterial population while still maintaining its biocompatibility. Our designed materials have not only been successful in killing cancer cells, but also bacterial pathogens. Therefore, the discovery of materials like RGOPAA, DHA@MGPAICT and G-V-PEI, we provide a diverse choice of materials with effective and vast potential applications in biomedical diagnostics and imaging, photodynamic and photothermal studies, magnetically guided drug delivery, as well as effective treatment for organic water pollutants.

Graphene and graphene-based materials, owing to their unique physical and chemical properties, have attracted considerable attention across the scientific communities worldwide. It has heralded a revolution in almost all the branches of materials science and chemistry. The attractive properties of graphene have led the extensive investigations to design and develop low-cost and high yield preparation protocols for chemically-derived graphene (graphene oxide). Graphene oxide (GO), a two-dimensional sheet of sp2 hybridized carbon, has received increasing attention as it possesses similar properties to that of graphene, as well as the availability of polar functional groups i.e. hydroxyl, carboxyl, etc. on its planar surface. Because of its high surface area, thermal stability, mechanical and electrical properties, it can be used as a potential supporting material and has already shown many promising applications. Keeping this in mind, the overall objectives of this PhD thesis is broadly focused on two main objectives; (1) synthesis of GO based nanocomposite such as GO–SnO2 ,GO-CuFe2O4 and GO-MnO2 for catalytic application and (2) Synthesis of GO based GO-SnO2-TiO2 and GO-CuFe2O4-ZnO ternary nanocomposite for photocatalytic application. In the heterogeneous catalysis part, emphasis was given on using graphene oxide based binary nanocomposite for the synthesis of biologically active molecules. As there was no significant literature(s) available at the start of my PhD work demonstrating the use of graphene oxide-based heterogeneous catalyst for biologically active molecules syntheses, it gave us a possible scope to explore and investigate towards the objective. In the first major project, a graphene oxide–SnO2 nanocomposite was utilized as potential nanocatalyst for biologically active molecules synthesis. For the first time, we have demonstrated the use of a GO–based nanocomposite as an extremely efficient catalyst for the synthesis of β-enaminones and β–enaminoesters biologically active molecules (RSC Adv., 2015, 5, 39193). The GO–SnO2 nanocomposites exhibited synergistically more superior catalytic efficiency compared to pure graphene oxide and SnO2 nanoparticles. Highlighting the importance of recyclability, in the next project, graphene oxide based magnetic nanocomposite was explored as novel recyclable heterogeneous catalyst for xanthenes synthesis. Magnetic graphene oxide based nanocomposites are important in catalysis as they can minimize the amount of catalyst loss during recyclability study and make the catalyst separation easy. In the second objective, a facile, efficient and environmentally-friendly protocol for the synthesis of xanthenes by graphene oxide-based GO-CuFe2O4 nanocomposite was developed by one-pot condensation route. (Sci. Rep.7, 2017: 42975). This approach offers several advantages such asshort reaction times, high yields, easy purification, a cleaner production and superior recovery and reusability of the catalyst by a magnetic field. Continuing this narrative, in the next objective, emphasis was given for the synthesis of a simple magnetic graphene oxide-MnO2 binary nanocomposite as an efficient nanocatalyst for other biologically active molecule synthesis. GO-MnO2 nanocomposite was used as an efficient catalyst for chalcones synthesis (Manuscript Submitted).The superior catalytic activity of this GO-based nanocomposite can be attributed to the synergistic interaction between GO and metal oxide nanoparticles, high surface area and presence of small sized metal oxide nanoparticles. In the next two projects, the focus was given to design GO-based ternary nanocomposite photocatalyst to degrade the toxic organic dyes present in water via solar light driven photocatalysis. Towards this objective, a, GO-SnO2-TiO2 ternary nanocomposite was designed as an efficient photocatalyst to degrade toxic organic dyes (RSC Adv., 2015, 5, 39193). This ternary (GO-SnO2-TiO2) nanocomposite have shown enhanced photocatalytic performance due to the stepwise structure of conduction band-edge (CB) levels of the individual component, TiO2 (CB)> SnO2(CB)> GO. It was found that such energy levels are beneficial for photo-induced electrons to transfer from TiO2 CB via SnO2 CB to GO, which can efficiently separate the photo-induced electrons and hinder the charge recombination in electron-transfer process, thus, enhancing its photocatalytic performance. In the last objective, emphasis was given to design magnetic GO-CuFe2O4-ZnO ternary nanocomposite as an efficient photocatalyst for the degradation of a series of toxic phenol and organic dyes under sunlight (New J. Chem., 2017, 41, 10568–10583.). In this work, attempts were made for efficient separation and recyclability process and to increase the photocatalytic efficiency under sunlight. The ternary nanocomposite was found to be more active as compared to their binary composite. The improved photocatalytic activity of the ternary nanocomposite can be ascribed due to the superior light assimilation, proficient charge transfer process, synergistic effect, high surface area, as well as superior durability of the composite. Solution combustion route was used to synthesize the GO based ternary photocatalyst which holds great promise for the synthesis of other GO-based nanocomposites.

碩士
國立高雄應用科技大學
化學工程與材料工程系博碩士班
104
Ag3PO4, with a band gap of 2.45 eV, shows excellent photocatalitc ability under visible light irradiation. Ag3PO4 was reported to integrate with magnetic materials for recycle use. Up to date, the combination of Fe3O4/ Ag3PO4 composite with graphene oxide (GO) was not found. Accordingly, a composite of Ag3PO4 and magnetic silica (Fe3O4@SiO2) was synthesized in this study, the resultant product Fe3O4@SiO2/Ag3PO4 was mixed with GO for investigating the photocatalytic activity of Fe3O4@SiO2/Ag3PO4/GO. First, the Fe3O4 nanoparticles prepared by co-precipitation method were dispersed a reverse microemulsion suspension containing tetraethyl orthosilicate (TEOS). Then, AgNO3 and Na2HPO4 were introduced into Fe3O4@SiO2 suspension for preparing Fe3O4@SiO2/Ag3PO4, followed by mixed with various amounts of GO. The as-prepared composites Fe3O4@SiO2/Ag3PO4/GO were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), confirming the magnetic Ag3PO4 were successfully combined with GO. The results indicate that the as-prepared composite exhibits higher visible-light photocatalytic activity toward methyl orange in aqueous solution compared with Fe3O4@SiO2/Ag3PO4, possible due to GO could suppress the recombination of electron-hole pairs. On the other hand, the magnetic photocatalyst Fe3O4@SiO2/Ag3PO4/GO could be easily collected from reaction mixture by a magnet. The magnetic composite Fe3O4@SiO2/Ag3PO4/GO is thought to be a potential photocatalyst for degrading dyes and pollutants under visible light.