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1
DECAVOLI, CRISTINA. "Organic dye-based photosystems for the production of solar fuels." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/376409.
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La ricerca di una nuova fonte di energia pulita è l'obiettivo per la comunità scientifica che dovrebbe essere raggiunto nei prossimi decenni. L'idrogeno ha guadagnato molta attenzione nella comunità scientifica come vettore di energia rinnovabile. Tuttavia, ora, l'obiettivo principale in campo energetico è quello di passare dalla produzione di idrogeno grigio (ottenuto da fonti fossili con successiva emissione di anidride carbonica) a quella di idrogeno verde (prodotto con zero carbon footprint).
Durante il mio dottorato di ricerca, mi sono concentrata su diverse tematiche riguardanti l'uso dei coloranti organici per migliorare la cattura della radiazione solare in dispositivi per la produzione di combustibili solari. Ho studiato due diverse applicazioni, una fotocatalitica e una fotoelettrochimica. Per queste applicazioni, ho considerato approcci covalenti e non covalenti.
In fotocatalisi, ho studiato solo un approccio non covalente tra il colorante e il donatore di elettroni sacrificali (SED). Ho deciso di non indagare su un'interazione covalente, perché, siccome il SED non può essere rigenerato dal sistema, porterebbe alla conseguente perdita di anche il colorante. In ogni caso, l'instaurazione dell'interazione supramolecolare ha favorito l'attività fotocatalitica confermando il successo del nuovo design proposto.
Riguardo alle celle fotoelettrochimiche, ho invece investigato entrambi gli approcci. Presento il primo esempio di coloranti a base di calix[4]arene impiegati nei fotoanodi di celle fotoelettrochimiche per sfruttare le loro capacità host-guest. Tuttavia, le prove di una corretta interazione host-guest benefica o infruttuosa tra i coloranti e il catalizzatore sono ancora in fase di studio. Il secondo approccio non covalente investigato è l'interazione π-π tra un colorante funzionalizzato con grafene e un catalizzatore propriamente funzionalizzato. Sono tutt'ora in corso le ulteriori caratterizzazioni e gli studi in applicazioni fotoelettrochimiche.
Riguardo all'approccio covalente, questo dovrebbe risultare più stabile e con l'immobilizzazione del catalizzatore a una distanza fissa dalla superficie del semiconduttore, è possibile evitare l'instaurarsi di interazioni dannose con il semiconduttore. Ho presentato il primo esempio di diadi a base di coloranti organici per l'applicazione di fotoanodi. Queste molecole hanno mostrato un'eccellente efficienza nell'evoluzione dell'ossigeno essendo la più alta rispetto allo stato attuale dell'arte per sistemi simili.
L'altro disegno covalente proposto è stato ottenuto durante il mio periodo all'estero a Yale University. Questo design innovativo ha fallito nell’uso in celle fotoelettrochimiche, ma questa molecola ha mostrato ottime prestazioni come semplice catalizzatore in celle elettrochimiche. Significa che questo catalizzatore possiede il giusto potenziale per ossidare l'acqua e può essere utilizzato in combinazione con una fonte di energia esterna, come i pannelli solari. Tuttavia, sono necessarie ulteriori indagini nella porzione di colorante per ottenere un migliore trasferimento di carica per le applicazioni PEC.<br>The pursuit of a clean energy source is a goal for the scientific community that should be achieved in the following decades. In recent years, hydrogen has gained much attention in the scientific community as a renewable energy carrier. However, the main goal in the energetic field is to move from the production of grey hydrogen (obtained using fossil sources with the subsequent emission of carbon dioxide) to the evolution of green hydrogen (produced with zero carbon footprint).
During my Ph. D., I have focused on different topics regarding the use of organic dyes as visible light photosensitizers in devices for the production of solar fuels through efficient light harvesting. I investigated both photocatalytic (PC) and photoelectrochemical (PEC) applications. For these applications, I considered both covalent and non-covalent approaches.
In the PC application, I investigated only a non-covalent approach between the dye and the sacrificial electron donor (SED). I decided not to investigate a covalent interaction because since the system cannot regenerate the SED, it would have led to the loss of the dye as well. Regardless, the establishment of supramolecular interactions that favored the photocatalytic activity confirmed the success of the new proposed design.
In the PEC application, I investigated both approaches. I present the first example of calix[4]arene-based dyes employed in photoanodes of PEC cells to exploit their host-guest capabilities. However, the evidence of the establishment of either beneficial or fruitless host-guest interaction between the dyes and the water oxidation catalyst (WOC) is still under investigation. The second non-covalent approach investigated is the π-π interaction between a graphene-functionalized dye and a suitable modified WOC. All the further characterization and PEC applications are in progress.
On the other hand, the covalent approach should be the most stable, and with the immobilization of the WOC at a fixed distance from the semiconductor surface, it is possible to avoid the establishment of a detrimental interaction with the semiconductor. We presented the first example of organic-dye-based dyads for photoanode application. These molecules showed excellent efficiencies in oxygen evolution being the highest concerning the actual state of the art for similar systems.
The other covalent design proposed has been obtained during my Ph. D. period abroad at Yale University. This innovative design failed in the PEC application, but this molecule exhibited very good performances as simple WOC in electrochemical cells. This means that this WOC has the right potential to oxidize water and can be used in combination with an external source of energy, such as solar panels. However further investigation in the dye portion is required to achieve a better charge transfer for the PEC applications.
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Dryfe, Robert A. W. "Mechanistic photoelectrochemistry." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294269.
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Dean, Frank. "Chalcopyrite photoelectrochemistry." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/11994.
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Dias, N. L. "Semiconductor photoelectrochemistry." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47025.
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Cooper, Jonathan A. "Studies in photoelectrochemistry." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301890.
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Rudge, Andrew John. "The photoelectrochemistry of platinum." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358597.
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Rajapakse, R. M. G. "Photoelectrochemistry of colloidal semiconductors." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47224.
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Ushiroda, Shin. "Microwave photoelectrochemistry of silicon." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760782.
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Bradley, Kieren Adam. "Photoelectrochemistry of nanostructured semiconductors." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687604.
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Semiconductors are vital components in the challenge of harvesting solar power to provide sufficient carbon neutral energy for a growing global population. A trend in semiconductor devices is to nanostructure some of the layers in order to obtain improvements in optical and electrical properties. This work focusses on two materials that have been gaining academic and commercial interest over a number of years. Zinc oxide (ZnO) is a wide bandgap semiconductor that can be grown via a number of physical and chemical deposition methods; the work on ZnO builds upon research on a chemical growth route which can create well aligned hexagonal rods with diameters from ~20 nm to Illm, with lengths of hundreds of nanometres to tens of microns. Changes in the growth solution led to either aligned or disordered rods, but the irreproducibility of the technique is evident. The second material studied is indium gallium nitride (InxGa1-xN), a semiconductor which can have its optoelectronic properties tuned by changing the ratio of In to Ga. Tuneable bandgaps are desirable for absorbing the optimum fraction of solar energy. Photoelectrochemistry is used to probe the optoelectronic characteristics of the semiconductors and theoretical models are used to simulate the combination of the optics and electronics in nanostructured electrodes, with waveguiding effects being shown to alter the expected efficiency of photoelectrochemical reactions in nanorods. A model based on the semiconductor continuity equation and Shockley-Read-Hall recombination is developed to describe the time dependent photoelectrochemical current of semiconductors with mid-band defect states, as functions of applied potential and illumination intensity. From the model a novel technique is provided to calculate the position and density of the defect states; the technique is successfully demonstrated on ZnO nanorods for the first time and evaluated for its effectiveness .
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Hüsser, Oskar E. "Photoelectrochemistry at (semi) insulating electrodes /." Zürich, 1987. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8384.
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Boxall, Colin. "The photoelectrochemistry of colloidal semiconductors." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38239.
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Wilde, C. P. "The photoelectrochemistry of some semiconductor electrodes." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37895.
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Kilmartin, Paul A. "Photoelectrochemistry and Spectroscopy of Conducting Polymer Electrodes." Thesis, University of Auckland, 1996. http://hdl.handle.net/2292/1919.
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Photoelectrochemistry and Spectroscopy of Conducting Polymer Electrodes Paul A. Kilmartin The conductive properties of films of polyaniline, substituted polyanilines, polypyrrole and polythiophene formed on platinum electrodes have been studied using photoelectrochemical, spectroscopic and surface science techniques. Bands due to oxidised and reduced forms of the polymers were monitored using in situ Raman spectroscopy, with polyaniline giving separate bands and polypyrrole showing an apparent shift of the main νCC mode by 35 cm-1 V-1. X-ray photoelectron spectroscopy allowed the elements of the polymers to be quantified into their various oxidation states, particularly through a deconvolution of the N 1s peak. Microscopic mounds of polymer were seen under atomic force microscopy consistent with the extent of polymer growth. The current response to a light flash perturbation on a milli-second time scale provided new information about the conducting polymers. For polyaniline in an insulating state, short-lived photocurrents were observed (less than 1.5 ms), while for polyaniline in a conductive state, longer-lasting photocurrents were observed (greater than 1.5 ms). Prolonged photocurrents indicative of high conductivity were observed up to a pH of 3.7, beyond which only shorter transients were obtained, consistent with previous polyaniline conductivity studies. The transition from conducting to insulating regions at more positive potentials was marked by the appearance of a short-lived cathodic photoresponse, which occurred at more positive potentials as the pH was lowered. Two models are proposed to account for the photocurrents. In the insulating state, the polyaniline film functions as a capacitance, with the fast transients being caused by discharge of surface states. In the conductive state, the prolonged anodic and cathodic photocurrents arise from redox processes with expulsion of solution species. Consistent with these models, polypyrrole showed only cathodic photocurrents (with anion release) and sulfonated polyaniline only anodic photocurrents (release of protons). The stable yellow film of parathiocyanogen (SCN)x formed by oxidation of SCN- at a platinum electrode in warm methanolic solution was studied, and was shown to be insulating and electroinactive, with short-lived photocurrents unless exposed to potentials greater than 1 V. Oxidation of SeCN- in aqueous solutions produced an analogous, though less stable, orange paraselenocyanogen film.
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Zhang, Menglong. "Ordered transparent conductive oxides (TCOs) for applications to photoelectrochemistry." Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/15194/.
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A method for fabricating high quality photonic TCO (transparent conductive oxide) films of macroporous FTO (fluorine doped tin oxide) (mac-FTO) and hollow sphere AZO (aluminum doped zinc oxide) (hs-AZO) is described. The films were used as electrodes to support photoelectrochemical reactions relevant to energy research. Methods have been developed for conformal coating the TCO electrodes with photoactive materials including CdS, Fe2O3 and C3N4. Previous literature describing photonic mac-FTO films generally show poor conductivity and optical properties, which limit the performance of structured TCOs in supporting photoelectrochemistry. Optimizing the synthesis and processing conditions gives high quality optical and conductive films of mac-FTO. Coating films with dispersed nanoparticles of CdS shows that the mac-FTO supports charge carrier transport to the contact and is not just a structural support for continuous conductive films of photoactive materials. Coating to maximise photocurrent gives over 9 mA cm-2 for conformally coated CdS@mac-FTO under visible light (> 420 nm) through a simple approach, showing an improvement in comparison to previous CdS literature work on structured electrodes. The new hs-AZO TCO also supports photocurrents up to 7.8 mA cm-2 after CdS coating. Both FTO and AZO show significant photocurrent enhancement in comparison to planar FTO analogues. In addition to CdS, methods were developed to conformally coat the organic photocatalyst C3N4 and the metal oxide Fe2O3 onto mac-FTO which showed enhanced photocurrent compared to planar analogues. Enhancements were typically in the range x (CdS), y (C3N4), and z (Fe2O3) which reflect the increase in surface area and greater loading of photoactive material. Potential photonic enhancements were not determined, however there is clearly scope for increasing the photocurrent per illuminated surface area using structured TCO electrodes.
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Karp, Christoph D. Lewis Nathan Saul. "Photoelectrochemistry of Si/polymer and Si/metal/solution interfaces /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10262007-085203.
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Maiolo, James Reynold Gray Harry B. Lewis Nathan Saul. "Photoelectrochemistry of microstuctured silicon materials for solar energy applications /." Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-05142009-130434.
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He, Yumin. "Solar Fuel Synthesis via Photoelectrochemistry: Understanding and Controlling Interfaces." Thesis, Boston College, 2019. http://hdl.handle.net/2345/bc-ir:108570.
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Thesis advisor: Udayan Mohanty<br>Solar fuel synthesis via photoelectrochemistry represents a promising strategy to achieve solar energy conversion and storage. The improvement of photoelectrochemical water splitting performance lies in choosing suitable photoelectrode materials, followed by strategic optimization of their properties. Among those properties, the interface between the semiconductors and electrolyte is of paramount importance, yet it is still not well understood. In my dissertation, I will mainly focus on understanding and controlling those interfaces, with two study platforms. The first study platform is tantalum nitride (Ta3N5), which is an attractive photoanode material with good optoelectronic properties. However, it suffers from low photovoltage despite of the high theoretical expectation and rapid performance decay when it is used for water oxidation. With the help of various characterization methods, it was found that water or hydroxyl group adsorption on the surface as well as the self-limited surface oxidation during water oxidation led to the positive shift of band edge positions and Fermi level, accompanied with increase of charge transfer resistance on the surface. In consequence, decrease of photovoltage and photocurrent was observed. Two different strategies were developed. The first was to fully isolate Ta3N5 from water with the deposition of uniform protection layer through atomic layer deposition. The second strategy utilized the reaction between Ta¬3N5 and co-catalyst instead of water, which led to the formation of a photo-induced interface that favored the desired chemistry instead of side reactions. The second study platform is a Si buried junction protected by GaN. By tuning the loading amount of Pt nanoparticles on GaN surface, both the photocurrent density and photovoltage of the photocathode was improved. With detailed spectroscopic study, it was implied that both charge transfer kinetics and interfacial energetics could be influenced by the loading of Pt on the surface<br>Thesis (PhD) — Boston College, 2019<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Chemistry
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Martin, Sophie. "Photoelectrochemistry of immobilised photosynthetic components: From chlorophyll to intact chloroplasts." Thesis, University of Warwick, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487960.
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This thesis aims to explore the use of scanning electrochemical microscopy (SECM) to investigate a range of processes, in particular fundamental electron transfer processes, connected to photosynthesis. These studies focus on several model systems ranging from LB films of chI a to intact chloroplasts. Electrochemical and scanned probe microscopy (SPM) techniques will be invaluable for monitoring these electron transfer processes and the structure - activity relationships in the systems of interest. A study of the different methods of chlorophyll film formation on solid supports and characterisation of these films with regard to surface coverage and film thicknesses has been explored with a range of techniques. Dropcast, spincast and LB films are investigated using UV-visible spectroscopy and AFM in order to elucidate the most appropriate chlorophyll film formation techniques for use in the later studies of this thesis. SECM has combined with an inverted microscope setup to investigate electron transfer in thin films of chlorophyll, with the aim of correlating the photoelectrochemical activity of the chlorophyll layer with the spatial organisation of the film. Using LB techniques, monolayers and multilayer films of chi a have been prepared on solid inert supports. It is clarified that electron transfer occurs from photo-excited chlorophyll to reduce oxygen. This is observed using SEeM, to electrochemically follow the transient change in oxygen concentration close to chlorophyll films upon illumination. The data obtained have been simulated using a commercial software package and used to determine kinetic parameters for this electron transfer process. This work is extended by considering the effects of electron transport in chI a molecules when deposited onto conducting electrode surfaces, compared to inert glass surfaces. These studies present some contradictory results to those previously published in literature and these findings have been discussed. ' The photosynthetic activity and surface structure of chloroplast and 'thylakoid membranes using SPM techniques and CLSM has been investigated. Factors such as illumination conditions, O2 evolution and reactions with different redox mediators will be studied to probe key steps in the electron transport chain reaction. Finally, confocal microscopy has been combined with SECM to study lateral proton diffusion at different phospholipid monolayers under a range of surface pressures. Therefore, investigating key diffusional processes as a model for those processes occurring at biological membranes.
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Harris, Derek B. "The Photoelectrochemistry of semiconductors : solar energy conversion and selective photoetching." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/11218.
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Kabre, Tushar Shriram. "Co3O4 Thin Films: Sol-Gel Synthesis, Electrocatalytic Properties & Photoelectrochemistry." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316552072.
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May, Kevin J. (Kevin Joseph). "Experimental and ab initio studies of oxide interfaces for photoelectrochemistry." Thesis, Massachusetts Institute of Technology, 2018. https://hdl.handle.net/1721.1/122884.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references.<br>The threats posed by anthropogenic climate change have spurred a research thrust towards renewable, carbon-free sources of energy. Photoelectrochemical (PEC) approaches are particularly attractive, combining energy capture from the sun with storage in the form of hydrogen or hydrocarbon fuel. However, there are significant materials challenges to be overcome, as well as a necessity for improved understanding of the material interfaces present in such systems. Transition metal oxides are a popular material for research as photo-electrodes but typically have poor electronic properties compared to conventional semiconductors. However, they are stable in aqueous and oxidizing environments and may present a wide variety of exotic physical behaviors, potentially opening new doors for device design. In this thesis, I explore several aspects of oxide interfaces relevant to PEC devices.<br>PEC measurements of ultra-thin films of LaFeO 3 grown on Nb:SrTiO3 reveal a thickness-dependent response via the depletion regions that form at both the film-substrate and film-electrolyte interfaces. Depending on the applied bias, reduction or oxidation photocurrent is observed that originates from the film-electrolyte or film-substrate interface, respectively. These qualitative behaviors are then explained with a band model. I then use the ACBNO functional for self-consistent Hubbard U corrections to density functional theory (DFT). First, improvement in treating bulk perovskite oxide electronic structure is demonstrated, followed by a study on a series of thin film slab structures that captures nanoscale changes in formal charge and hybridization (via the change in U) at multiple locations within the film, simultaneously. The trends in oxygen adsorption energy and band alignment are explained in terms of film thickness and electronic structure.<br>Finally, a first-principles descriptor for oxygen adsorption energy is developed from high-throughput DFT calculations and analysis of the density of states using tight binding and the moments theorem. This descriptor methodology may be used in high-throughput screening for catalyst materials, where bulk calculations may be used to predict surface properties without resorting to more demanding slab calculations. The combination of high-throughput screening of materials with the engineering possibilities afforded by substrate and active layer thickness variation provides a promising path forward to successful oxide photoelectrochemical devices.<br>by Kevin Joseph May.<br>Ph. D.<br>Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Parker, David. "Structure and photoelectrochemistry of nanostructured II-VI semiconductors for photovoltaic applications." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681734.
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ZnO nanorods, sensitised to visible light using dyes, quantum dots, or thin films of low-bandgap semiconductors are commonly used as photoanodes in novel solar cells . They have a number of exciting properties for such an application. These include a direct conducting path for electrons, with few grain boundaries, and an increased surface area offering enhanced optical absorption. They are also able to sustain a depletion layer, the electric field this creates can effectively separate charge carriers at the nanorod/sensitiser interface, reducing recombination. However, despite these potential benefits, devices made using 1-D ZnO nanostructures are so far unable to match the performance of devices constructed using mesoporous Ti02 films. One of the reasons given for this is the presence of mid-bandgap states at the surface, which are investigated in this work. ZnO nanorods were grown using a hydrothermal growth technique. Using cyclic voltammetry and photocurrent measurements, mid-band gap trap states were identified and their position found to be centred around 0.8V below the conduction band. Visible luminescence from defect states identified by photoluminescence may be associated with these states. The effects of annealing in air at 180°C, 350°C and 450°C were investigated, all three experimental techniques showed that annealing at temperatures equal to or greater than 350°C was effective in reducing the density of these states. Annealing was also found to have a critical effect on doping density of the nanorods, with implications for both conductivity and the characteristics of the depletion layer that forms at the interface of the nanorods. The doping density was measured using a modified form of MottSchottky analysis and found to be high (> 1020cm-3) for as-grown rods, and only slightly reduced by annealing at temperatures up to 350°C. Annealing at 450°C however reduced the doping density by over two orders of magnitude. These results are consistent with previously reported evidence that incorporated hydrogen acts as a donor for ZnO. A study of the structure of alloyed CdSel-xTex quantum dots was also carried out using a combination of high resolution transmission electron microscopy, selected area electron diffraction and X-ray diffraction. This showed that both wurtzite and zinc blende QDs were present at all compositions, with no clear phase transition between different compositions. CdSe QDs were then successfully used to sensitise annealed nanorods to visible light. Electron transport within the rods was shown to be efficient. The results in this work should prove useful in understanding how best to utilise 1D ZnO nanostructures in solar cells, and provide insights into the nature of defect states which have so far limited the efficiency of such devices.
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Jimenez, David Jesus Fermin. "Semiconductor photoelectrochemistry : multi-electron transfer processes at illuminated semiconductor-electrolyte interfaces." Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319217.
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Masilela, Nkosiphile. "Photophysical and photoelectrochemical properties of water soluble metallophthalocyanines." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1004991.
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This work presents the synthesis, characterization, photophysicochemical and photoelectrochemical properties of anionic octa-caboxylated (MOCPcs), tetra-sulfonated (MTSPcs) and quaternized cationic (Q(T-2-Py)MPcs) water soluble aluminium, gallium, silicon, titanium and zinc phthalocynines. The peripherally tetra-substituted cationic (Q(T-2-Py)MPcs) and anionic (MTSPcs) were found to be aggregated in aqueous media, yet the octa-carboxylated (MOCPcs) counterparts were monomeric in solution. Cremophor EL (CEL) was used as a disaggregating agent, all the aggregated complexes disaggregated partially or completely in the presence of CEL. The photophysicochemical properties of aggregated complexes were investigated both in the presence of CEL and in aqueous media of pH 11 alone. Low triplet, singlet oxygen and fluorescence quantum yield were obtained in aqueous media (especially for the aggregated complexes) but a high improvement was achieved upon addition of CEL. The gallium complexes ((OH)GaOCPc and (OH)GaTSPc) showed good photophysicochemical properties with higher triplet and singlet oxygen quantum yields. For photoelectrochemistry the (MPcs) dyes were adsorbed to nanoporous ZnO, electrodeposited in the presence of eosin Y as structure directing agent (SDA) on FTO substrates by refluxing or soaking the films in a solution containing the dye of interest such that a full surface coverage was achieved. Quaternized cationic (Q(T-2-Py)MPc) and tetrasulfonated (MTSPcs) phthalocyanines formed strong aggregates when deposited on the surface of FTO/ZnO substrate leading. High external (IPCE) and internal (APCE) quantum efficiencies of up to 50.6% and 96.7% were achieved for the OTiOCPc complex. There was a lower overall cell efficiency for quaternized and tetrasulfonated metallophthalocyanines because of the strong aggregates when they were on the surface of the electrodes. Among the studied materials, OTiOCPc gave the highest overall cell efficiency of phthalocyanine electrodeposited on ZnO of so far = 0.48%.
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Ritenour, Andrew. "Close-Spaced Vapor Transport and Photoelectrochemistry of Gallium Arsenide for Photovoltaic Applications." Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19202.
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The high balance-of-system costs of photovoltaic installations indicate that reductions in absorber cost alone are likely insufficient for photovoltaic electricity to reach grid parity unless energy conversion efficiency is also increased. Technologies which both yield high-efficiency cells (>25%) and maintain low costs are needed. GaAs and related III-V semiconductors are used in the highest-efficiency single- and multi-junction photovoltaics, but the technology is too expensive for non-concentrated terrestrial applications. This is due in part to the limited scalability of traditional syntheses, which rely on expensive reactors and employ toxic and pyrophoric gas-phase precursors such as arsine and trimethyl gallium. This work describes GaAs films made by close-spaced vapor transport, a potentially scalable technique which is carried out at atmospheric pressure and requires only bulk GaAs, water vapor, and a temperature gradient to deposit crystalline films with similar electronic properties to GaAs prepared using traditional syntheses.
Although close-spaced vapor transport of GaAs was first developed in 1963, there were few examples of GaAs photovoltaic devices made using this method in the literature at the onset of this project. Furthermore, it was unclear whether close-spaced vapor transport could produce GaAs films appropriate for use in photovoltaics. The goal of this project was to create and study GaAs devices made using close-spaced vapor transport and determine whether the technique could be used for production of grid-connected GaAs photovoltaics. In Chapter I the design of the vapor transport reactor, the chemistry of crystal growth, and optoelectronic characterization techniques are discussed. Chapter II focuses on compositional measurements, doping, and improved electronic quality in CSVT GaAs. Chapter III describes several aspects of the interplay between structure and electronic properties of photoelectrochemical devices. Chapter IV addresses heteroepitaxial growth of GaAs on "virtual" Ge-on-Si substrates. This is a topic of importance for the broader III-V community as well as the photovoltaic community, as Si is the substrate of choice in many areas of industry.
This dissertation includes unpublished and previously published co-authored material.
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Flake, John Christopher. "Photoelectrochemical etching of silicon in nonaqeous electrolytes." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/13278.
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Irvine, J. T. S. "The photoelectrochemical reduction of carbon dioxide." Thesis, University of Ulster, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378753.
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Yang, Shangfeng. "Ultrathin films of metallofullerenes : preparation, characterization and photoelectrochemical applications /." View abstract or full-text, 2003. http://library.ust.hk/cgi/db/thesis.pl?CHEM%202003%20YANG.
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Pennarun, Gaelle. "The micro-optical ring electrode : a new and novel electrode system for photoelectrochemistry." Thesis, University of Central Lancashire, 1999. http://clok.uclan.ac.uk/18843/.
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The design of a novel photoelectrochemical sensor, the micro-optical ring electrode (MORE), is described. Based on a thin-ring microelectrode and using at fibre-optic light guide as the insulating material interior of the ring, the MORE has been deisigned, constructed and developed to permit electrochemical investigation of photochemically generated solution species. Initial characterisation of the electrode behaviour in the dark has been ccomplished by the use of ferricyanide in conjunction with predictive mathematical models of the time dependence of the current at micro ring electrode. The photocharacterisation of the MORE has been achieved looking at the photochemical response of tris (2,2'biyridine)ruthenium(II) in presence of the quenching agent Fe3+ . Subsequent application of the MORE has been in the electrochemical investigation of photoactive drugs employed in Cancer Therapy. In the following study, the microelectrochemistry of methylene blue, a dye commonly employed on Photodynamic Therapy (PDT), has been characterised in the dark using, in the first instance, gold disc microelectrodes. The electrochemical behaviour of MB+ on gold disc microelectrodes has than been compared to the results obtained when using the MORE. Exploration of the photoelectrochemical response of the MORE is reported, achieved via the interrogation of the photoelectrochemistry of MB+. Photocurrent signals obtained during cyclic voltammetric and chronoamperometric studies of MB\ conducted with the MORE under illuminated conditions and in the absence of any deliberately added reducing agent, are attributed to the formation and subsequent detection of 3 MB+ within the diffusion layer of the microring electrode. The data demonstrate that the use of the MORE for direct electrochemical detection of photogenerated species with lifetimes of < 9 x 5 10- s is possible. The electrochemistry of 3MB+ over the applied potential range from -0.4 to +1.0 V versus SCE is elucidated and discussed in the context of the behaviour of photoexcited MB+ in the presence of deliberately added reducing agent Fe3+. In order to investigate the production of singlet oxygen associated with cancer treatment, an attempt was made to study the MB+/02 system. This part of the project has not been completed, however a preliminary study of the electrochemistry of the MB.
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Nanthakumar, Alaganandan 1958. "PHOTOELECTROCHEMISTRY AND ELECTROCHEMISTRY OF ELECTROACTIVE LAYERED MOLECULES ON PHTHALOCYANINE AND METAL ELECTRODE SURFACES." Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/277248.
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Leung, Jane Jing. "Molecular hybrid photocathodes based on silicon for solar fuel synthesis." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288001.
Texte intégralRésumé :
Artificial photosynthesis is broadly defined as the process of solar energy conversion into chemical fuels and represents a promising route towards alleviating the global energy crisis. In this context, the development of photocathodes for the use in photoelectrochemical cells is an attractive approach for the storage of solar energy in the form of a chemical energy carrier (e.g. H$_{2}$ and CO$_{2}$-reduction products from H$_{2}$O and CO$_{2}$). However, molecular catalyst-based photocathodes remain scarcely reported and typically suffer from low efficiencies and/or stabilities due to inadequate strategies for interfacing the molecular component with the light-harvesting material, with benchmark systems continuing to rely on precious metal components. In this thesis, the straightforward preparation of a p-silicon|mesoporous titania|molecular catalyst photocathode assembly that is active towards proton reduction in aqueous media is first established. The mesoporous TiO$_{2}$ scaffold acts as an electron shuttle between the silicon and the catalyst, while also stabilising the silicon from passivation and enabling a high loading of molecular catalysts. When a Ni bis(diphosphine)-based catalyst is anchored on the surface of the electrode, a catalytic onset potential of +0.4 V vs. RHE and a high turnover number of 1 $\times$ 10$^{3}$ was obtained from photoelectrolysis under UV-filtered simulated solar irradiation at 1 Sun after 24 hours. Notwithstanding its aptitude for molecular catalyst immobilisation, the Si|TiO$_{2}$ photoelectrode showed great versatility towards different types of catalysts and pH conditions, highlighting the flexible platform it represents for many potential reductive catalysis transformations. The Si|TiO$_{2}$ scaffold was extended towards solar CO$_{2}$ reduction via the immobilisation of a novel phosphonated cobalt bis(terpyridine) catalyst to achieve the first precious metal-free, CO$_{2}$-reducing molecular hybrid photocathode. Reducing CO$_{2}$ in both organic-water and purely aqueous conditions, the activity of this photocathode was shown to be affected by its environment and reached record turnover numbers for CO production by a molecular photocathode under optimal conditions, maintaining stable activity for more than 24 hours. Critically, in-depth electrochemical and in situ resonance Raman and infrared spectroelectrochemical investigations provided key insights into the nature of the surface-bound Co complex under reducing conditions. While demonstrating the power and precision offered by such in situ spectroelectrochemical techniques, these studies ultimately alluded to a catalytic mechanism that contrasts with that reported for the in-solution (homogeneous) catalyst. Overall, this affords a distinct mechanistic pathway that unlocks an earlier catalytic onset and enables photoelectrochemical activity. Finally, in the context of improving product selectivity in molecular-based CO$_{2}$ reduction, polymers based on the cobalt bis(terpyridine) motif were synthesised and immobilised on inverse opal-type electrodes designed specifically to accommodate large molecules. Rational design of the polymers' co-monomers was aimed towards the provision of an artificial environment for the active complex that would influence product selectivity, which was ultimately demonstrated by the improvement of a H$_{2}$:CO product ratio of 1:2 (molecule) to 1:6 (polymer). Further studies of this all-in-one system included modulating its degree of cross-linkage as well as a CO$_{2}$ reducing demonstration photocathode on a Si|inverse-opal TiO$_{2}$ scaffold.
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Mersch, Dirk. "Wiring of photosystem II to hydrogenase for photoelectrochemical water splitting." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709273.
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Somervell, Mark Howell. "Top surface imaging through vapor phase silylation for 193 nm lithography /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Danziger, James Lee. "Characterization of molecular semiconductor and multilayer molecular organic photoconductor interfaces by photoelectrochemistry and surface analytical techniques." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185217.
Texte intégralRésumé :
Organic semiconductor thin films are of interest to us for a variety of molecular electronic applications, including solar cells, chemical sensors, and nonlinear optical devices. We have been seeking unusual new ways of controlling the composition and long-range molecular structure of these materials through the use of vacuum deposition techniques which mimic, in some ways, those used for epitaxial layer growth in inorganic materials. Thin films of perylene tetracarboxylic dianhydride (PTCDA) have been examined as electrodes and photoelectrodes on both metal and metal oxide substrates. In contrast to most previous studies of phthalocyanine thin films, these materials behaved in such a way as to suggest n-type character, i.e. dark electron transfer reactions were facile in negative potential regions with solution redox couples, and little dark electrochemistry could be observed in regions of positive potentials. It is likely that junction formation occurs only as a result of illumination, with different rates of interfacial hole and electron injection and transport, at the PTCDA/electrolyte interface. Electron microscopy of the PTCDA films indicated that they were deposited as elongated crystallites, with relatively large spaces between individual crystallites, which strongly affected their dark and photoelectrochemical behavior, especially on Au substrates. Electrochemical polymerization of α-napthol was carried out to passivate sites that were electrochemically active in the dark, a treatment which greatly enhanced the overall electrochemical activity of these PTCDA thin films. A variety of p-n heterojunction-like structures, created from thin film molecular materials (vanadyl phthalocyanine (VOPc) and perylene tetra-carboxylic dianhydride (PTCDA)), have been nondestructively explored by photoelectrochemical techniques and UHV surface analytical techniques. Vacuum deposited bilayers and multilayers of these thin films behave like "p-n" diodes over a narrow potential window. The open circuit photopotential is determined by the junction potential formed at the Pc/PTCDA interface. It was found that the transient photocurrent (using a modulated light source) in multilayer VOPc/PTCDA assemblies was directly related to the number of interfaces present, consistent with the idea that exciton dissociation is localized primarily to such an interface, and is the photocurrent limiting process.
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Qian, Weizhong, and 钱伟忠. "Microbial electrodes and Cu2O-based photoelectrodes for innovative electricity generation and pollutant degradation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47170281.
Texte intégralRésumé :
Photoelectrochemical cells (PEC) and microbial fuel cells (MFC) are two promising environmental technologies with the purposes of energy production and pollutant degradation. In this study, p-type Cu2O thin film electrodes were synthesized by electrodeposition on the ITO glass. The influences of various electrodeposition conditions, including the deposition potential, temperature, electrolyte pH, substrates and deposition duration on the morphology and the photoelectrochemical properties of the Cu2O films were investigated. The so-called p-type micro-crystal Cu2O thin film photocathodes were synthesized at -0.4 V, 70 °C and pH 10. An innovative composite Cu2O/TiO2 photoelectrode was developed by dip-coating TiO2 on the surface of the Cu2O film. The outer TiO2 layer would help reduce the electron-hole recombination and hence improve the catalyst stability. The photocatalyst was shown to be capable of photocatalytic degradation of model pollutants. Under simulated solar irradiation, methylene blue, acridine orange, and bromocresso brilliant blue G were effectively degraded in the Cu2O-based PEC. The composite Cu2O/TiO2 photoelectrode could further enhance the photodegradation of the dyes.
For the study on MFC with the saline wastewater-inoculated MFCs, an electricity output of 581 mW/m2 could be achieved at a NaCl concentration of 200 mM. Based on the characterization of the bioande using the electrochemical impedance spectroscopy (EIS) technique, the R(QR)(QR) model, instead of the conventional R(QR) model, was found to fit well with the EIS data of the carbon cloth bioanode. The results support the two-interface-based physical model for the description of the bioanode, including an interface on the flat electrode and the other for the porous biofilm matrix. The new model was employed to monitor the biofilm formation and development on the carbon clothe anode during the MFC start-up. In addition, photocatalytic MFC was developed by using the Cu2O film as the photocathode for the MFC. With the simulated solar light illumination, the PMFC open circuit voltage could be increased by 200 mV comparing to the MFC test. Moreover, the cathode material (Cu2O) is much less expensive than Pt used by common MFCs.<br>published_or_final_version<br>Civil Engineering<br>Master<br>Master of Philosophy
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Peng, Xiaoyu. "Electron microscopy studies of nanomaterials for electrochemical and photoelectrochemical applications." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709295.
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Greenaway, Ann. "Close-Spaced Vapor Transport for III-V Solar Absorbing Devices." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23185.
Texte intégralRésumé :
Capture of the energy in sunlight relies mainly on the use of light-absorbing semiconductors, in solar cells and in water-splitting devices. While solar cell efficiency has increased dramatically since the first practical device was made in 1954, production costs for the most-efficient solar absorbers, III-V semiconductors, remain high. This is largely a result of use of expensive, slow growth methods which rely on hazardous gas-phase precursors. Alternative growth methods are necessary to lower the cost for III-V materials for use in solar cells and improve the practicality of water-splitting devices.
The research goal of this dissertation is two-fold: to expand the capabilities of close-spaced vapor transport, an alternative growth method for III-Vs to demonstrate its compatibility with current technologies; and to explore the fundamental chemistry of close-spaced vapor transport as a growth method for these materials. This dissertation surveys plausibly lower-cost growth methods for III-V semiconductors (Chapter II) and presents in-depth studies on the growth chemistry of two ternary III-Vs: GaAs1-xPx (Chapter III) and Ga1-xInxP (Chapter IV). Finally, the growth of GaAs microstructures which could be utilized in a water-splitting device is studied (Chapter V).
This dissertation includes previously published and unpublished co-authored material.<br>2019-01-09
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Tong, Qi. "The Influence of Surface Chemistry on the Photoelectrochemical Properties of FeS(2) Photoanodes." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2482.
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The recurring theme of this dissertation is the correlation between FeS2 surface chemistry and key electrical and electronic properties of FeS2. Efforts have been made to identify and characterize the FeS2 surface, investigate the photoelectrochemistry of FeS2 photoanodes under anhydrous and anoxic conditions, and investigate the influence of deliberate surface chemistry on FeS2 photoelectrochemistry.
Infrared reflection-absorption spectroscopy (IRRAS) was used to investigate a thin adsorbate layer on pyrite. The results showed that the combination of angle-dependent studies and computational efforts are a powerful tool for characterizing the pyrite surface.
The photoelectrochemistry of FeS2 photoanodes was investigated in an I¯/I3¯ acetonitrile electrolyte acetonitrile electrolyte. The results revealed that the non-aqueous system was suitable for strictly anhydrous and anoxic photoelectrochemical studies. A model was proposed to explain the observed influence of concentration of dissolved I2 on the photovoltage. A central component of the proposed model was that shunting was assumed to take place at physically distinct regions of the electrode and that mass-transport to and from these regions could be treated separately from mass-transport to the regions responsible for the rectifying behavior of the FeS2/liquid junction. The implication of the agreement between experimental and calculated J-E curves is that macroscopic photoelectrochemical investigations may underestimate the quality of FeS2 photoanodes due to the presence of defects.
The influence of surface treatments on FeS2 photoelectrochemistry was further studied using non-coordinating redox species. A statistically significant increase of photovoltage was observed after treating FeS2 surfaces with KCN. X-ray photoelectron spectroscopy was used to study chemical bond formation between the electron donating ligands and iron(II) centers on the pyrite surface. The results were discussed in terms of charge recombination models and surface coordination chemistry.
Unfinished work is also presented. Cathodic polarization in acidic media is a prerequisite for any detectable photoresponse. The exact function of the electrochemical activations was further investigated by electropolishing pyrite electrode under different experimental conditions including etchant identity and applied bias. The results suggested that the electrochemical treatment removes the damaged surface layer caused by mechanical polishing, and might also stabilize the surface states. Further experiments can be focus on anhydrous etching of pyrite photoanode.
The research presented in this dissertation guides future studies of thin film FeS2 photovoltaics.
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Lindgren, Torbjörn. "In search of the holy grail of photoelectrochemistry : a study of thin film electrodes for solar hydrogen generation /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4017.
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Lindgren, Torbjörn. "In Search of the Holy Grail of Photoelectrochemistry : A Study of Thin Film Electrodes for Solar Hydrogen Generation." Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4017.
Texte intégralRésumé :
Hydrogen is a wanted energy carrier in a future society less dependent of fossil fuels. This thesis investigates the possibilities of using solar energy to convert water into hydrogen and oxygen, so called artificial photosynthesis. Through this work multiple inexpensive and stable thin film semiconductor electrodes have been produced and used as solar energy absorbers and active sites for direct watersplitting in photoelectrochemical cells. The electrodes have mainly been of nanostructured metal oxide character but also nitrides have been studied. Detailed back ground theory on photoelectrochemistry of semiconductors for hydrogen evolution is given in the summary of the thesis. Nanostructured WO3 electrodes with a quantum yield close to unity were designed and photoelectrochemically characterized. Hematite, α-Fe2O3, nanorods were synthesized and characterized for the aim of water oxidation. The morphology of the hematite nanorods was found to be in favor of the traditional isotropic nanostructured electrodes. Moreover, a unique porous nitrogen doped TiO2 material, photoactive in visible light, was obtained by reactive sputtering. The nitrogen doped material has interesting photoelectrochemical properties and is also promising for related applications such as pollution degradation by photocatalysis. Polycrystalline indium nitride, InN, was produced by reactive sputtering. Electrodes of the as prepared InN as well as electrodes annealed in nitrogen were studied for the aim of photooxidation of water. The electrodes studied are interesting candidates as potential watersplitting electrodes in photoelectrochemical cells, even if all had in common that further improvements and optimizations need to be done.
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França, Rita Borges. "Cryptosporidium spp., Giardia spp. e ovos de helmintos em esgoto hospitalar : destruição e analise de dano estrutural dos protozoarios apos o processo fotoeletroquimico." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/315635.
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Orientador: Regina Maura Bueno Franco<br>Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia<br>Made available in DSpace on 2018-08-09T07:00:20Z (GMT). No. of bitstreams: 1
Franca_RitaBorges_M.pdf: 4952448 bytes, checksum: 49473f55f00ae94646a96bb8c6672aac (MD5)
Previous issue date: 2007<br>Resumo: O efluente hospitalar apresenta, dentre seus componentes, organismos como vírus, bactérias, protozoários e helmintos, que ocasionam muitas doenças com implicações em saúde pública. Cryptosporidium spp. e Giardia spp. são protozoários parasitos com grande importância por sua veiculação hídrica e cujas formas infectantes são resistentes aos processos rotineiramente usados no tratamento de água e esgoto. A transmissão destes pode ocorrer com a ingestão dos oocistos e cistos eventualmente presentes na água e nos alimentos contaminados, por contato direto (pessoa a pessoa), por contato indireto (objetos contaminados), pelo contato sexual ou pode ser zoonótica. Os métodos mais utilizados para desinfecção em estações de tratamento são a aeração, cloração e irradiação por UV, mas a cloração, não é suficiente para eliminar oocistos de Cryptosporidium spp e cistos de Giardia spp. A tecnologia eletroquímica oferece um meio de tratamento eficiente para a oxidação. da carga orgânica e microbiológica degradando-as ou mineralizando-as. O presente trabalho teve por objetivos: (1) verificar a ocorrência natural de Cryptosporidium spp. e Giardia spp. em amostras de esgoto do Hospital de Clínicas de Campinas, utilizando o método, de centrífugo-concentração seguido de clarificação com éter e visualização por, imunofluorescência direta, durante o período de um ano; (2) verificar a presença de ovos e larvas de helmintos no esgoto hospitalar empregando a técnica da NOM (Norma Oficial Mexicana) e (3) avaliar a taxa de destruição e o dano estrutural causado em cistos e oocistos após o tratamento fotoeletroquímico. No esgoto hospitalar bruto 4,1 % e 58,3 % das amostras foram positivas para Cryptosporidium spp. e Giardia spp., respectivamente, sendo observada a concentração média de 2,7 x 103 oocistos/L e 3,8 x 105 cistos/L. Foi possível verificar a elevada presença de helmintos, com 90 % das amostras apresentando positividade e concentração de 5,8 x 104 ovos/L e 4,0 x 105 larvas/L. Os protozoários e helmintos presentes em altas concentrações no esgoto hospitalar representam uma séria ameaça à saúde humana. Para os ensaios com o tratamento fotoeletroquímico, amostras de 1 L de esgoto hospitalar foram artificialmente contaminadas com cistos e oocistos e, posteriormente, submetidas a esse tratamento em um reator de bancada, com tempos de exposição de 0,30, 60 e 90 minutos. Por meio das técnicas de imunofluorescência direta, microscopia de contraste de fase e microscopia eletrônica de varredura verificou-se o dano estrutural causado pela ação dos radicais hidroxila nesses protozoários patogênicos e a destruição dos mesmos. O tratamento fotoeletroquímico mostrou uma redução na concentração dos protozoários nos tempos de 30 e 60 minutos e após 90 minutos, nenhum cisto ou oocisto foi detectado. A presença do cloreto no efluente bruto (média de 45 mg/l) desencadeou uma potencializaçáo da ação de mecanismo do reator, gerando efeito associado com a eletrólise, dos radicais hidroxila com a formação de hipoclorito<br>Abstract: Hospital effluent presents organisms as virus, bacteria, protozoan and helminthes, that cause many iIInesses with implications in public health. Cryptosporidium spp. and Giardia spp. are parasites with waterborne importance and its cysts and oocysts are resistant to the routinely processes used in water treatment. Their transmission can occur by oocysts and cysts ingestion in the water and contaminated foods, by direct contact (person the person), by indirect contact (contaminated objects), by sexual contact or zoonotic. The methods used for disinfection and treatment of sewage are aeration, chlorination and irradiation of ultraviolet light, but the treatment by chlorination is not enough to inactivate Cryptosporidium spp. oocyst and Giardia spp. cysts. The electrochemical technology offers an efficient treatment for the oxidation of organic and microbiological load, degrading and mineralizing them. The present work had as objectives: (1) to verify the natural occurrence of Cryptosporidium spp. and Giardia spp. in samples of Clinical Hospital sewage from Unicamp using centrifugal concentration followed by clarification with ether method and visualization by immunoflourescence assay, during one year, (2) to verify the presence of eggs and larvae of helminthes in the hospital sewage by NOM (Mexican Official Norm) technique and (3) to evaluate the destruction rate and the structural damage caused in cysts and oocysts by photoelectrochemical treatment. In raw hospital sewage 4.1 % and 58.3% of the samples were positive for Cryptosporidium spp. and Giardia spp., respectively, with concentrations of 2.7 x 103 oocysts/L and 3.8 x 105 cysts/L. The high presence of helminthes, 90% positive, with 5.8 x 104 eggs/L and 4.0 x 105 larvae/L and protozoan in hospital sewage represent a serious threat to human being health. For the assays with the photoelectrochemical treatment, samples of 1 L of hospital sewage artificially contaminated with cysts and oocysts ! were submitted to this treatment in a bench reactor, with times of exposition of 0, 30, 60 and 90 minutes. By the techniques of immunofluorescence assays, microscopy of phase contrast and scanning electronic microscopy, the structural damage and destruction were observed, caused by hydroxyl radicals in these pathogenic protozoans. The photoelectrochemical treatment showed a concentration reduction of the protozoan in 30 and 60 minutes, and after 90 minutes no cyst or oocysts were detected. The chloride present in raw effluent (average of 45 rng/L) unchained a potential action of the reactor mechanism, generating an effect associated with electrolysis of the hydroxyl radicals with production of hypochlorite<br>Mestrado<br>Parasitologia<br>Mestre em Parasitologia
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Dong, Wei. "Photoelectrochemical catalysis of waste water in pharmaceutical industry." Магістерська робота, Kyiv National University of Technology and Design, 2021. https://er.knutd.edu.ua/handle/123456789/19552.
Texte intégralRésumé :
The master’s thesis is devoted to the study of photoelectrochemical treatment of the wastewater from pharmaceutical industrials. The aim is achieved through the new redox hybrid materials with viologen and AuNPs and CdS, respectively. The technical task is focused on the preparation of viologen-based hybrid films and improving their electrochemical and photocatalytic properties. Based on the electrochemical, spectroscopic and microscopic analysis, the materials have shown good redox properties, good stability and good photoelectrochemical performance. The excellent redox properties and good photoelectrochemical performance of the hybrid films have improved their photocatalytic properties in wastewater treatment, and their easy preparation and good stabilities will also extend their application as the new wastewater treatment materials in the future.
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Abshere, Travis Arthur. "A picosecond photoluminescence and electrochemical study of the n-GaAs/elctrolyte interface in a nonaqueous photoelectrochemical cell /." view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9978241.
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Thesis (Ph. D.)--University of Oregon, 2000.<br>Typescript. Includes vita and abstract. Includes bibliographical references (leaves 122-126). Also available for download via the World Wide Web; free to University of Oregon users.
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Tatistcheff, Helen B. "Use of microelectrochemical devices to study diffusion of electroactive species in nonfluid media and photoelectrochemistry of surface-confined metallocenes." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/17373.
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Randorn, Chamnan. "Synthesis and characterisation of materials for photoelectrochemical applications." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1716.
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The preparation of visible light driven photocatalysts for photocatalytic water splitting has been achieved by a CO₂ free, low cost and simple novel method. Combination of peroxide based route with organic free solvent and titanium nitride, carbon free precursor and air and moisture stable, would be useful. Clear red-brown solution of titanium peroxo species was obtained by dissolution of TiN in H₂O₂ and HNO₃ acid at room temperature without stirring. The resultant red brown solution is then used as a titanium solution precursor for yellow amorphous and yellow crystalline TiO₂ synthesis. Visible light photoactivity of the samples was evaluated by photooxidation of methylene blue and photoreduction producing hydrogen from water splitting. The high surface area of yellow amorphous TiO₂ exhibits an interesting property of being both surface adsorbent and photoactive under visible light for photodecolourisation of aqueous solution of methylene blue. However, it might not appropriate for hydrogen production. Nanoparticulate yellow crystalline TiO₂ with defect disorder of Ti³⁺ and oxygen vacancies depending upon synthesis conditions has been characterised by ESR, XPS, CHN analysis and SQUID. Single phase rutile can be produced at low temperature. It is stable at high temperature and the red shift of absorption edge increases with the treatment temperature. Yellow crystalline TiO₂ exhibits an interesting property of being photoactive under visible light. The best photocatalytic performance was observed for 600°C calcination, probably reflecting a compromise between red shift and surface area with changing temperature. Moreover, overall water splitting into hydrogen and oxygen might be obtained by using this material even in air atmosphere. Photoactivity can be improved by testing under anaerobic atmosphere and/or adding sacrificial agent. Quantum efficiency under visible light is still low but comparable to other reports. The maximum efficiency varies from 0.03 % to 0.37 % for hydrogen production and from 0.03 % to 0.12 % for oxygen production, depending on photon energy and sacrificial agents.
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Kast, Matthew. "Towards Tunable and Multifunctional Interfaces: Multicomponent Amorphous Alloys and Bilayer Stacks." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22288.
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Controlling the electronic structure and requisite charge transfer at and across interfaces is a grand challenge of materials science. Despite decades of research and numerous successes in the fields microelectronics and photovoltaics much work remains to be done. In many applications, whether they be in microelectronics, photovoltaics or display technology there is a demand for multiple functions at a single interface. Historically, existent materials were either discarded as an option due to known properties or tested with some application based figure of merit in mind. Following this, the quality of the material and/or the preparation of the surface/interface to which the material would be deposited was optimized. As the microelectronics and photovoltaics industries have matured, continued progress (faster, lower power transistors and more efficient, cheaper, abundant solar cells) will require new materials (possibly not previously existent) that are fundamentally better for their application than their highly optimized existent counter parts. The manifestation of this has been seen in the microelectronics field with introduction of hafnium silicates to replace silica (which had previously been monumentally successful) as the gate dielectrics for the most advanced transistors. Continued progress in efficient, cheap, abundant photovoltaics will require similar advances. Advances will be needed in the area of new abundant absorbers that can be deposited cheaply which result in materials with high efficiencies. In addition, selective contacts capable of extracting charge from efficient absorbers with low ohmic losses and low recombination rates will be needed. Presented here are two approaches to the multifunctional interface problem, first the use of amorphous alloys that open up the accessible composition space of thin films significantly and second the use of bilayers that loosen the requirements of a single film at an interface.
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Antuch, Cubillas Manuel. "Photoelectrochemical kinetics of visible-light driven water splitting at Rh∶SrTiO3 based electrodes." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS084/document.
Texte intégralRésumé :
L’étude de la cinétique de la photodissociation de l’eau assistée par lumière visible a été l’objectif principal de ce travail. En tant que matériau photo-excitable, le semi-conducteur SrTiO₃ dopé au Rh a été utilisé. Le dopage permet l’absorption de lumière visible et donc la transformation d’énergie solaire en combustibles chimiques. Le 1er Chapitre de cette thèse est consacré à une étude bibliographique couvrant les méthodes de caractérisation et les modèles de la cinétique photo-électrochimique. Le 2ème Chapitre traite la description des matériaux et méthodes expérimentaux. Le 3ème Chapitre concerne la caractérisation de la cinétique de la photodissociation de l’eau sur photo-électrodes à base de Rh:SrTiO₃, modifiées en surface par ajout d’un clathrochélate modèle, ou avec du Cu ou du Pt métalliques. Le 4ème Chapitre décrit une étude théorique du mécanisme de la réaction de dégagement d’hydrogène, catalysée par un clathrochélate modèle. Le spectre EXAFS du complexe a été analysé et modélisé, et les intermédiaires importants du mécanisme ont été mis en évidence. Le 5ème Chapitre est consacré à l’étude dynamique de photo-électrodes à base de Rh:SrTiO₃ en utilisant la technique de la photo-tension à lumière modulée. Ce Chapitre présente des résultats inattendus, qui sont rapportés pour la première fois. Ce comportement bizarre a été modélisé par un système d’équations différentielles usuellement utilisées pour décrire ce type de système photo-électrochimique<br>The kinetics of water photo-dissociation assisted by visible light was the main topic of this work. The Rh doped SrTiO₃ semiconductor was employed as photo-excitable material. It can absorb visible light and therefore transform solar energy into useful chemical fuels. In this manuscript, a wide bibliographic overview is provided in the 1st Chapter, covering a description of the characterization methods and current models for photoelectrochemical kinetics. The 2nd Chapter is devoted to the description of the materials and methods. The 3rd Chapter deals with the full photoelectrochemical kinetic characterization of water splitting with Rh:SrTiO₃ photoelectrodes, surface-modified by addition of a model clathrochelate or with metallic Cu or Pt. In the 4th Chapter, a theoretical study of the mechanism of hydrogen evolution catalyzed by a model clathrochelate is provided. During the discussion, the EXAFS spectrum of the organometallic complex was thoroughly analyzed and modelled, and the relevant protonated intermediates involved in the mechanism were identified. The 5th Chapter deals with the photoelectrochemical dynamics of illuminated Rh:SrTiO₃ -based photo-electrodes, characterized by the light-modulated photovoltage technique. Unusual results were obtained and are reported in this thesis for the first time. This unexpected dynamic behavior has been modelled by a set of classical differential equations usually used to describe such photo-processes
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Mayer, Matthew T. "Ionic and electronic behaviors of earth-abundant semiconductor materials and their applications toward solar energy harvesting." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3034.
Texte intégralRésumé :
Thesis advisor: Dunwei Wang<br>Semiconductor devices offer promise for efficient conversion of sunlight into other useful forms of energy, in either photovoltaic or photoelectrochemical cell configurations to produce electrical power or chemical energy, respectively. This dissertation examines ionic and electronic phenomena in some candidate semiconductors and seeks to understand their implications toward solar energy conversion applications. First, copper sulfide (Cu₂S) was examined as a candidate photovoltaic material. It was discovered that its unique property of cation diffusion allows the room-temperature synthesis of vertically-aligned nanowire arrays, a morphology which facilitates study of the diffusion processes. This diffusivity was found to induce hysteresis in the electronic behavior, leading to the phenomena of resistive switching and negative differential resistance. The Cu₂S were then demonstrated as morphological templates for solid-state conversion into different types of heterostructures, including segmented and rod-in-tube morphologies. Near-complete conversion to ZnS, enabled by the out-diffusion of Cu back into the substrate, was also achieved. While the ion diffusion property likely hinders the reliability of Cu₂S in photovoltaic applications, it was shown to enable useful electronic and ionic behaviors. Secondly, iron oxide (Fe₂O₃, hematite) was examined as a photoanode for photoelectrochemical water splitting. Its energetic limitations toward the water electrolysis reactions were addressed using two approaches aimed at achieving greater photovoltages and thereby improved water splitting efficiencies. In the first, a built-in n-p junction produced an internal field to drive charge separation and generate photovoltage. In the second, Fe₂O₃ was deposited onto a smaller band gap material, silicon, to form a device capable of producing enhanced total photovoltage by a dual-absorber Z-scheme mechanism. Both approaches resulted in a cathodic shift of the photocurrent onset potential, signifying enhanced power output and progress toward the unassisted photoelectrolysis of water<br>Thesis (PhD) — Boston College, 2013<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Chemistry
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Grau, Abarca Sergi. "Molecular phocatodes and photoanodes for light driven water splitting." Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/668369.
Texte intégralRésumé :
La fotosíntesis artificial és un procés on una molècula d’aigua es transforma en oxigen i hidrogen gas. Aquest procés permet obtenir combustibles solars (hidrogen gas) a partir d’aigua i llum solar i és una metodologia alternativa per obtenir energia neta i sostenible en substitució dels combustibles fòssils tradicionals.
L’objectiu d’aquesta tesi és la síntesi i estudi de catalitzadors de reducció de protó a hidrogen gas, així com la preparació d’elèctrodes i fotoelèctrodes capaços de dur a terme la reducció i l’oxidació d’aigua amb el menor cost energètic possible.
Durant la realització d’aquesta tesi s’han sintetitzat tres catalitzadors de reducció d’aigua de cobalt i el seu estudi ha permès identificar els processos que limiten la reacció i el seu mecanisme. També s’han preparat elèctrodes actius amb catalitzadors moleculars adsorbits sobre grafè. Finalment s’han preparat fotoànodes i fotocàtodes capaços d’oxidar i reduir l’aigua, respectivament, per sota del potencial termodinàmic sota llum solar.<br>La fotosíntesis artificial es un proceso donde una molécula de agua se transforma en oxígeno e hidrógeno gas. Este proceso permite obtener combustibles solares (hidrógeno gas) a partir de agua y luz solar y representa una metodología alternativa para obtener energía limpia y sostenible en sustitución de los combustibles fósiles tradicionales.
El objetivo de esta tesis es desarrollar catalizadores de generación de hidrógeno , así como la preparación de electrodos y fotoelectrodos para la reducción y oxidación del agua con el menor coste energético.
Durante la realización de esta tesis se han sintetizado tres catalizadores de reducción de agua de cobalto y su estudio ha permitido identificar los procesos que limitan la reacción y su mecanismo. También se han preparado electrodos activos con catalizadores moleculares absorbidos sobre grafeno. Finalmente se han preparado fotocátodos y fotoánodos capaces de reducir y oxidar agua, respectivamente, por debajo del potencial termodinámico bajo luz solar.<br>Artificial photosynthesis is a process where a molecule of water is split into molecular oxygen and hydrogen. This process produces a solar fuel (hydrogen gas) from water and sunlight and it is considered a promising clean and sustainable alternative to the traditional fossil fuels.
The objective of this thesis is the synthesis and study of cobalt catalysts active for hydrogen evolution reaction, as well as the preparation of electrodes and photoelectrodes active for the reduction and water oxidation of water with the lowest energy consumption.
In this thesis, cobalt hydrogen evolution catalysts have been synthetized and studied allowing us to determine the limiting factors of the reaction and its mechanism. In addition, active electrodes modified with with graphene functionalized with a molecular catalyst have been prepared. Finally, photoanodes and photocathodes active for the oxidation and reduction of water, respectively, that work below the thermodynamic potential under sunlight have been prepared.
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Duan, Lele. "Artificial Water Splitting: Ruthenium Complexes for Water Oxidation." Doctoral thesis, KTH, Organisk kemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-40848.
Texte intégralRésumé :
This thesis concerns the development and study of Ru-based water oxidation catalysts (WOCs) which are the essential components for solar energy conversion to fuels. The first chapter gives a general introduction about the field of homogenous water oxidation catalysis, including the catalytic mechanisms and the catalytic activities of some selected WOCs as well as the concerns of catalyst design. The second chapter describes a family of mononuclear Ru complexes [Ru(pdc)L3] (H2pdc = 2,6-pyridinedicarboxylic acid; L = pyridyl ligands) towards water oxidation. The negatively charged pdc2− dramatically lowers the oxidation potentials of Ru complexes, accelerates the ligand exchange process and enhances the catalytic activity towards water oxidation. A Ru aqua species [Ru(pdc)L2(OH2)] was proposed as the real catalyst. The third chapter describes the analogues of [Ru(terpy)L3]2+ (terpy = 2,2′:6′,2′′-terpyridine). Through the structural tailor, the ligand effect on the electrochemical and catalytic properties of these Ru complexes was studied. Mechanistic studies suggested that these Ru-N6 complexes were pre-catalysts and the Ru-aqua species were the real WOCs. The forth chapter describes a family of fast WOCs [Ru(bda)L2] (H2bda = 2,2′-bipyridine-6,6′-dicarboxylic acid). Catalytic mechanisms were thoroughly investigated by electrochemical, kinetic and theoretical studies. The main contributions of this work to the field of water oxidation are (i) the recorded high reaction rate of 469 s−1; (ii) the involvement of seven-coordinate Ru species in the catalytic cycles; (iii) the O-O bond formation pathway via direct coupling of two Ru=O units and (iv) non-covalent effects boosting up the reaction rate. The fifth chapter is about visible light-driven water oxidation using a three component system including a WOC, a photosensitizer and a sacrificial electron acceptor. Light-driven water oxidation was successfully demonstrated using our Ru-based catalysts.<br>QC 20110922