Dissertations / Theses: 'Photoelectrochemical'

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Pilkington, Matthew B. G. "Photoelectrochemical E.S.R." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253279.

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Buan, Marthe Emelie Melandsø. "Photoelectrochemical Hydrogen Production." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for materialteknologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19101.

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The possibilities for using CaNb2O6 as a photocatalyst in direct water splitting have been evaluated by investigating the electronic structure of the material. In addition the oxide was doped with nitrogen in order to modify the electronic structure and obtain visible light absorption. Experimental techniques such as electrochemical impedance spectroscopy (EIS), photocurrent, and diffuse reflectance spectroscopy (DRS) were combined with theoretical approaches to determine the bandgap, flatband potential and quasi-Fermi levels of the photocatalyst. CaNb2O6 was prepared by a sol-gel synthesis and doped with nitrogen by heat treatment of the oxide powder in an ammonia atmosphere. X-ray diffraction (XRD) confirmed phase pure orthorhombic CaNb2O6 for both pure and N-doped oxide and excluded a possible transformation of the oxide into an oxynitride. Upon illumination anodic photocurrents were observed implying that CaNb2O6 was an n-type semiconductor due to oxygen vacancies in the lattice. From the wavelength dependency of the photocurrent a direct bandgap of 3.7eV and an indirect bandgap of 3.4eV were determined for undoped CaNb2O6. Doping with nitrogen altered the optical properties of the oxide and shifted the absorption edge into the visible light region. Calculations using the density functional theory (DFT) attributed the change in absorption properties to the formation of narrow energy bands above the valence band of pure CaNb2O6. An alternative explanation could be a hybridization of N 2p and O 2p bands. Correspondingly a reduction of the bandgaps for N-doped CaNb2O6 with respect to the undoped oxide was identified. Impedance was applied to determine the flatband potential of CaNb2O6 from Mott-Schottky plots. However the obtained results seemed to be dominated by contributions from the electrode substrate. Theoretical investigations concluded that pinhole-free oxide layers creating an ohmic contact with the substrate are required in order to designate the observed impedance response to the space charge capacitance. Quasi-Fermi level measurements indicated a low photocatalytic activity of CaNb2O6 as no photocurrent could be detected. Further investigations are needed to identify the cause of the photocurrent limitations. Nevertheless probable explanations could be low conductivity in CaNb2O6, high concentrations of recombination centers or slow charge transfer kinetics. The latter was confirmed for porous oxide layers as the addition of a hole scavenger increased the measured photocurrent. Positive photocurrent transients were also observed for porous CaNb2O6 films and could be related to either the diffusion of electrons through the porous oxide layer or to a photoanodic decomposition of the photocatalyst.

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Shan, Ying. "Colloidal photoelectrochemical systems." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46546.

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Viger, Marie-Élise. "Photoelectrochemical degradation of ciprofloxacin." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=92310.

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Conventional wastewater treatment plants have been found to only partially degrade pharmaceuticals. As a result, antibiotics have been detected in the aquatic environment, causing an increase in bacteria resistance.
In this research a photoelectrochemical reactor with a TiO2-RuO2 working electrode was built to study its possible application for the treatment of antibiotic-containing wastewaters. Ciprofloxacin was chosen as a model antibiotic.
Degradation of ciprofloxacin was carried out photocatalitically, electrochemically and photoelectrochemically. All three methods were successful in degrading the antibiotic. However, photoelectrochemical degradation was found to be significantly more efficient than the other two techniques due to a synergetic factor. For instance after one hour at a current of 0.4A for 1mM of ciprofloxacin, photoelectrochemical process degrades 56% while electrochemical and photocatalytic process only degrades 41% and 3% respectively.
Overall, it was demonstrated that photoelectrochemical degradation represents possibly a viable method for the treatment of antibiotic-containing industrial wastewaters.
Les produits pharmaceutiques sont seulement partiellement dégradés dans les centres de traitement des eaux usées. Des antibiotiques se retrouvent donc dans les ruisseaux et rivières. Leur présence cause une résistance grandissante des bactéries aux traitements antibiotiques.
Un réacteur photoélectrochimique avec une électrode RuO2-TiO2 fut construit pour déterminer s'il pouvait être utilisé pour le traitement des eaux usées contenant des antibiotiques. La ciprofloxacine fut choisie comme modèle antibiotique.
Les procédés photochimique, électrochimique et photoélectrochimique peuvent tous dégrader la ciprofloxacine. Le meilleur résultat est obtenu avec la dégradation photoélectrochimique grâce à un phénomène synergétique. Par exemple pour la dégradation d'une solution de 1mM de ciprofloxacine avec un courant de 0.4A, le procédé photoélectrochimique dégrade 56% tandis que les procédés électrochimique et photochimique dégradent respectivement 41% et 3%.
La dégradation photoélectrochimique s'avère donc prometteuse pour le traitement des eaux usées contenant des antibiotiques.

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Trevellick, P. R. "Photoelectrochemical studies on semiconductors." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371584.

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Koker, Lynne. "Photoelectrochemical formation of porous silicon." Thesis, University of Birmingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368290.

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Hickey, Stephen Gerard. "Photoelectrochemical studies of chalcogenide nanoparticles." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393089.

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Davies, John Phillip. "Mechanistic studies of photoelectrochemical systems." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37669.

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Dukku, Bappah Mohammed. "The kinetics of photoelectrochemical systems." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38293.

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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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Hassan, Ibrahim. "Solar energy conversion by photoelectrochemical processes." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542078.

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Burch, Henry Arthur. "Nanostructured electrodes for photoelectrochemical water splitting." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6903/.

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Nanostructured MoS\(_2\) and ZnFe\(_2\)O\(_4\) were synthesised and tested as catalytic water splitting photoelectrodes. MoS\(_2\) was nanopatterned from a bulk crystal using a combination of nanosphere lithography and plasma etching. Three morphologies were produced: nanospheres deposited with interstices between them produced nanopillars, nanospheres squashed into hexagons imprinted a nanowell pattern, and linked nanopillars resulted from parts of each. The MoS\(_2\) was tested as a photocathode and morphologies with linkages between features had improved catalysis than those without. This was attributed to the layered structure of MoS\(_2\). These samples degraded in air to MoSxO(\(_2\)\(_-\)\(_x\)), and an electrochemical technique utilising Na\(_2\)S\(_2\)O\(_3\) was used to re-sulfidate the MoSxO(\(_2\)\(_-\)\(_x\)). The technique decreased the onset potential from -0.27 V SHE to -0.17 V SHE, and the Tafel slope from 282 mV dec\(^{-1}\) to 87 mV dec\(^{-1}\). ZnFe\(_2\)O\(_4\) electrodes were deposited by AACVD from a precursor molecule. The deposition solvent composition was systematically altered between methanol and ethanol to examine its effect on the nanostructure. ZnFe\(_2\)O\(_4\) electrodes deposited from predominantely methanol solvent had compact morphologies due to heterogenous nucleation, while the electrodes deposited from predominantly ethanol solvent had high surface area structures due to homogeneous nucleation. The more exothermic enthalpy of combustion of ethanol was deemed responsible.

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Höjer, Pontus. "Photoelectrochemical Water-Splitting using 3C-SiC." Thesis, Linköpings universitet, Halvledarmaterial, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-139761.

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In 1972 Fujishima and Honda conceptualised a photoelectrochemical cell for hydrogen generation via PEC water splitting. Hydrogen as a clean energy carrier provides environmentally friendly energy storage solutions or can fuel certain applications. This idea has since then been further built upon with new materials and combinations with the aim of improving efficiency. In this project n-type cubic silicon carbide thick layers were grown by a sublimation method and characterised for water splitting performance. A generated photo-current density of 0.45 mA/cm2 was measured with no bias between the working and counter electrodes.

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Gamstedt, Heléne. "Ionic Liquid Electrolytes for Photoelectrochemical Solar Cells." Doctoral thesis, KTH, Chemistry, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-426.

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Potential electrolytes for dye-sensitized photoelectrochemical solar cells have been synthesized and their applicability has been investigated. Different experimental techniques were used in order to characterize the synthesized electrolytes, such as elemental analysis, electrospray ionisation/mass spectrometry, cyclic voltammetry, dynamic viscosity measurements, as well as impedance, Raman and NMR spectroscopy. Some crystal structures were characterized by using single crystal X-ray diffraction.

In order to verify the eligibility of the ionic compounds as electrolytes for photoelectrochemical solar cells, photocurrent density/photovoltage and incident photon-to-current conversion efficiency measurements were performed, using different kinds of light sources as solar simulators. In electron kinetic studies, the electron transport times in the solar cells were investigated by using intensitymodulated photocurrent and photovoltage spectroscopy. The accumulated charge present in the semiconductor was studied in photocurrent transient measurements.

The ionic liquids were successfully used as solar cell electrolytes, especially those originating from the diethyl and dibutyl-alkylsulphonium iodides. The highest overall conversion efficiency of almost 4 % was achieved by a dye-sensitized, nanocrystalline solar cell using (Bu₂MeS)I:I₂ (100:1) as electrolyte (Air Mass 1.5 spectrum at 100 W m^-2), quite compatible with the standard efficiencies provided by organic solvent-containing cells. Several solar cells with iodine-doped metal-iodidebased electrolytes reached stable efficiencies over 2 %. The (Bu₂MeS)I:I₂-containing cells showed better long-term stabilities than the organic solvent-based cells, and provided the fastest electron transports as well as the highest charge accumulation.

Several polypyridyl-ruthenium complexes were tested as solar cell sensitizers. No general improvements could be observed according to the addition of amphiphilic co-adsorbents to the dyes or nanopartices of titanium dioxide to the electrolytes. For ionic liquid-containing solar cells, a saturation phenomena in the short-circuit current densities emerged at increased light intensities, probably due to inherent material transport limitation within the systems.

Some iodoargentates and -cuprates were structurally characterized, consisting of monomeric or polymeric entities with anionic networks or layers. A system of metal iodide crownether complexes were employed and tested as electrolytes in photoelectrochemical solar cells, though with poorer results. Also, the crystal structure of a copper-iodide-(12-crown-4) complex has been characterized

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Nissfolk, Jarl. "Charge Transport Processes in Mesoporous Photoelectrochemical Systems." Doctoral thesis, KTH, Organisk kemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9849.

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During the last decade, the dye sensitised solar cell (DSC) has attracted much attention. The technology has a potential to act as a new generation of photovoltaic device, it has also increased our knowledge within the field of photoelectrochemistry. The materials used in the DSC have been used in other technologies, such as electrochromic displays. This thesis examines how such systems can be analysed to understand their properties from their components. Both of the considered device technologies consist of a thin mesoporous semiconductor film immersed in an electrolyte. The study starts by investigating some of the fundamental properties of the mesoporous semiconductor and its interface with the electrolyte. This gives rise to the charge-voltage relationship for the devices, which is related to the chemical capacitance and electronic energy levels for the materials. In particular,special attention is given to the DSC and the properties of the charge carriers in the semiconductor. For the DSC, several techniques have been developed in order to understand the processes of transport and recombination for the charge carriers in the semiconductor film, which are vitally important for performance. In this thesis, particular focus is given to light modulation techniques and electrical analysis with impedance spectroscopy. The transportproperties show for both techniques a nonlinear behaviour, which is explained with the trapping model. The DSC solar cell is analysed in order to interpret the transport measurements for film thickness optimisation. DSC cells with new semiconductor materials, such as ZnO, were analysed with impedance measurements to provide new insights into the optimisation of the performance of the photoelectrochemical solar cell technology.
QC 20100804

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Gamstedt, Heléne. "Ionic liquid electrolytes for photoelectrochemical solar cells /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-426.

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17

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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Davidson, Alison. "Photoelectrochemical cells for the treatment of wastewater." Thesis, University of Ulster, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272204.

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Altalhi, Amal A. "Energy conversion and storage via photoelectrochemical methods." Thesis, University of Hull, 2013. http://hydra.hull.ac.uk/resources/hull:16512.

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Photoelectro analytical chemistry provides an elegant technique by which to explore, amongst others, various industrial and environmental applications. To this end, four areas of photoelectroanalytical chemistry are investigated in order to develop industrially - and environmentally - relevant galvanic and photogalvanic cells, together with exploring the electro-generation of an industrially important molecule and diffusion factors they may affect this generation. The first study is investigated a long-range charge transfer, using tert-butylferrocene (tBuFc) as model hydrophobic system. It is found that the apparent one-dimensional diffusion coefficient depends on the tBuFc loading. It is suggested that an efficient relay mechanism for electron transfer is through the partitioning of the oxidised form between the two subphases, with inter-pseudophase reaction. However, the second study investigated the normal lyotropic liquid crystals (in the lamellar or hexagonal phases) as a route to afford a structured, three-dimensional, quasi-biphasic framework within which electron transfer cascades may take place using cyclic voltammetry. It is shown that these can take place through reagent partitioning between the hydrophobic and hydrophilic subphases, and it is illustrated how the structure and its orientation, the nature of the ionic doping of the framework, and the hydrophobicity of the redox analyte may give rise to changes in the observed voltammetric waveshape. For the case of an artitifical mimic of the first few stages of Photosystem I, it is demonstrated that photo-induced electron transfer is likewise affected by the orientation, and develop a system of photon efficiency of ~0.1%. Thirdly, a novel attempt at power production was attempted with the construction and optimisation of a photogalvanic cell system. A literature review was conducted and a system proposed utilizing 10-methylphenothiazine (NMP) as a light harvester and zinc as a sacrificial electrode with tetrabutylammonium chloride (TBAP) as a supporting electrolyte and chloroform as a mediator. The study aimed to create a cell that could be produced using industrial run-off or other waste water supplies. A series of cells was produced with varying concentrations of both zinc and NMP solutions and the power conversions studied by producing a voltage-current plot for each system. A system that exhibited 9.02% conversion efficiency keep, future studies were conducted to show whether the zinc species effected the power conversion or if silver would act in a similar way. A mechanism was proposed for the power production process and so studies using 2, 4-Dichlorophenol (DCP) rather than chloroform we conducted; it was believed that the dissociation step for DCP was step wise rather than concerted. Lower power production was seen in these cells as predicted by the reaction mechanism. Tris - (4-bromophenyl) - amine (TBA), an alternative light harvester to NMP, was used to see if altering the active chemical agent resulted in efficiency change. Finally , A photogalvanic cell that employs 2,4-dichlorophenol as a fuel source, an N-substituted phenothiazine as light harvester, and sacrificial zinc anode is presented, and shown to afford a ca. 4% light-to-electrical power conversion efficiency in violet light.

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Thorne, James E. "Understanding the Limitations of Photoelectrochemical Water Splitting." Thesis, Boston College, 2018. http://hdl.handle.net/2345/bc-ir:108257.

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Thesis advisor: Dunwei Wang
Artificial photosynthesis is achieved by placing a semiconductor in water, where photoexcited charges generate a photovoltage at the surface of the semiconductor. However, solar to fuel efficiencies of earth abundant metal oxides and metal nitrides remain limited by their low photovoltages. Many different treatments have been used to improve the photovoltages of semiconductors, such as photocharging, surface regrowths, or the addition of heterogeneous catalysts. However, in these treatments, it remains unclear whether the enhanced photovoltage arises from improved kinetics or energetics. In many of the following studies, the surface kinetics of different semiconductors are measured in order to quantify how surface kinetics are related to the photovoltage of these materials. Different spectroscopic measurements are made along with detailed analysis of the Fermi level and quasi Fermi level in order to corroborate the kinetic data with energetic data. Together, this dissertation explores a multitude of methods and procedures that demonstrate how the photovoltage of semiconductors can be understood and manipulated for photoelectrochemial artificial photosynthesis
Thesis (PhD) — Boston College, 2018
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry

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Eklund, John C. "Electrode reaction dynamics." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297021.

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Ahmed, Samina. "Electrochemical methods for the investigation of supported semiconductor photocatalysis." Thesis, University of Warwick, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342520.

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23

Cotting, Thomas Stefan. "Photoelectrochemical characterization of semiconductors for solar energy conversion /." [S.l.] : [s.n.], 1989. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8800.

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Ardoin, Noel A. "The effects of electrolyte chemistry in photoelectrochemical cells." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/11833.

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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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Hutton, Roger S. "Optical and photoelectrochemical studies of GaAs and GaAlAs." Thesis, University of Southampton, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280857.

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Emig, Christopher Joseph. "Photoelectrochemical array platform for genomic scale DNA synthesis." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37200.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.
Includes bibliographical references (leaves 56-58).
Molecular and synthetic biologists have increasing demand for large, high-fidelity constructs of synthetic DNA. Recent developments in harvesting oligonucleotides from DNA microarrays has proven that these can be assembled into large constructs of DNA for costs significantly less than traditional methods. This thesis presents a complete platform for the photoelectrochemical cleavage of protecting groups during in situ DNA synthesis. Photoelectrochemically patterned microarrays of phosphoramidite dye were produced with spot sizes of 100 um. This technology holds the potential for lowest cost per base pair of DNA produced over alternative microarray technologies, and may prove to be useful in de novo synthesis of large DNA constructs.
by Christopher Joseph Emig.
M.Eng.

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Chamier, Jessica. "Photoelectrochemical detection of inorganic mercury in aqueous solutions." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5213.

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Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Due to the adverse human health effects associated with mercury (Hg) toxicity, an innovative method for inorganic mercury (Hg2+) determination in aqueous solutions was investigated. The method of Hg2+ determination involved the use of a Hg2+ selective chemosensor immobilised onto an indium tin oxide (ITO) coated electrode in a photoelectrochemical cell. Upon light activation and in the presence of Hg2+ the fluorescent chemosensor absorbed a photon, and charge separation would occur according to the nature of the semiconductive material coated onto the ITO substrate. The charge separators and semiconductors investigated were an n-type carrier TiO2, polyaniline (PANI) and copolymers of polyaniline and 2-bromoaniline (P[A-co-2- BrA]s) with different monomer ratios. The polymer and copolymer coated ITO working electrodes used in the Hg2+ sensitive photoelectrochemical cell were electrochemically evaluated. The results demonstrated that the ITO coated with PANI had superior conductive and semiconductive properties compared to ITO coated with P[A-co-2-BrA]s. The ITO glass substrates were coated with TiO2, PANI or P[A-co-2-BrA]s, followed by the fluorescent chemosensor, a rhodamine 6G derivative (RS). The electrodes were subsequently photoelectrochemically evaluated in a photoelectrochemical cell in the presence of Hg2+. The PANI-RS coated electrode behaved as a photocathode in the presence of Hg2+ under illumination. The PANI-RS photoresponse increased with increasing Hg2+ concentration in the range 10 to 150 μg L-1, with a limit of detection of 6 μg L-1. ITO coated with TiO2 (ITO/TiO2) followed by a composite of PANI and RS had a linear photoanodic response in the Hg2+ concentration range of 10 to 200 μg L-1 and a limit of detection of 5 μg L-1. ITO and ITO/TiO2 coated with the P[A-co-2-BrA]s and RS had considerably lower photoresponses towards Hg2+ in aqueous solutions compared to PANI-RS. The photoresponses decreased with increasing 2-bromoaniline content. The PANI and P[A-co-2-BrA]s coated ITO and ITO/TiO2 electrodes were then also coated with another rhodamine 6G derivative with a thiolactone moiety (RT). The PANI coated electrode yielded a photocathodic response in the Hg2+ concentration range 0.2 to 5 μg L-1. ITO coated with TiO2 had no photoresponse towards Hg2+ due to repulsive forces between TiO2 and the RT molecules. The photoresponses of the working photoelectrodes towards Hg2+ were further evaluated in a custom photoelectrochemical Hg2+ detector. The photoresponses of PANI-RS and PANI-RT gave qualitative results for the presence of Hg2+ in aqueous solutions in concentrations as low as 2 μg L-1.
AFRIKAANSE OPSOMMING: Weens die negatiewe gesondheids aspekte toegeskryf aan Hg2+ vergiftiging is ‘n nuwe innoveerende metode van Hg2+ deteksie in wateroplossings ondersoek. Die voorgestelde metode van Hg2+ deteksie behels die gebruik van ‘n Hg2+ selektiewe chemosensor geimmobiliseer op ITO elektrodes in ‘n fotoelektrochemiese sel. Met lig aktivering en in die teenwoordigheid van Hg2+, absorbeer die fluoreseerende chemosensor ‘n foton, gevolg deur lading skeiding, soos bepaal deur die aard van die halfgeleidende material wat op die ITO platjies bedek is. Die halfgeleiers wat ondersoek was, was TiO2, PANI en ko-polimere van PANI met 2-bromoanilien. Die polimeer en kopolimeer bedekte ITO werkende elektrodes wat in die Hg2+ sensitiewe fotoelektrochemiese sel gebruik is, is elektrochemies geevalueer. Daaruit is gevind dat ITO bedek met PANI superieure geleier en halfgeleier eienskappe het in vergelyking met die ITO wat bedek is met P[A-co-2-BrA] kopolimere. Die ITO glas plaatjies is bedek met TiO2, PANI en die P[A-co-2-BrA] kopolimere gevolg deur die fluoresseerende chemosensor, RS. Die elektrodes is onderskeidelik fotoelektrochemies getoets in ‘n fotoelektrochemiese sel in die teenwoordigheid van Hg2+. Die PANI-RS elektrode het soos ‘n fotokatode opgetree in die teewoordigheid van Hg2+ onder beligting. Die foto-reaksie van die PANI-RS elektrode teeonoor Hg2+ het liniêr toegeneem van 10 μg L-1 tot 150 μg.L-1 met ‘n limiet van deteksie op 6 μg L-1. ITO/TiO2 wat bedek is met ‘n samestelling van PANI en RS het ‘n fotoanodiese reaksie gehad teenoor Hg2+ in die liniêre reeks van 10 tot 200 μg L-1 met ‘n deteksie limiet van 5 μg L-1. ITO en ITO/TiO2 bedek met die P[A-co-2-BrA] kopolimere het heelwat laer fotoreaksies getoon teenoor Hg2+ in waterige oplossings Die fotoreaksie het afgeneem met toeneemende 2-bromoanilien inhoud van die kopolimeer. Die PANI en P[A-co-2-BrA] kopolimere bedekte ITO en ITO/TiO2 elektrodes is verder bedek met ‘n tweede rhodamine 6G afgeleide, RT. Die ITO/PANI bedek met RT het weer ‘n fotokatodiese reaksie gehad teenoor Hg2+ in die konsentrasie interval 0.2 tot 5 μg L-1. Die ITO/TiO2 elektrode bedek met die PANI-RT samestelling het geen fotoreaksie gehad teenoor Hg2+ weens afstotende kragte tussen die TiO2 and RT molekules. Die fotoreaksies van die verskeie werkende elektrodes teenoor Hg2+ is verder getoets in ‘n tuisgemaakte fotoelektrochemiese Hg2+ detektor. Die fotoreaksies van die PANIRS en PANI-RT samestellings op ITO het kwalitatiewe resultate gelewer vir die teenwoordigheid van Hg2+ in waterige oplossings in konsentrasies tot so laag soos 2 μg L-1.

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Tengeler, Sven. "Cubic Silicon Carbide For Direct Photoelectrochemical Water Splitting." Thesis, TUprints, 2017. http://www.theses.fr/2017GREAI079/document.

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Le but de ce travail était l’analyse de la capacité de carbure de silicium cubique à servir de matériau d’anode pour le fractionnement de l’eau photo-électrochimique direct. Les données récoltées (principalement la spectroscopie photo-électronique, électrochimie, Raman et spectroscopie UV-Vis) permettaient de ramener la faible efﬁcacité de carbure de silicium cubique dopé n pour le dégagement d’oxygéne à des problèmes fondamentaux.Principalement le courant photoélectrique réalisable est limité par le ﬂux des trous générés par photo à la surface de semi-conducteur. Comme carbure de silicium cubique est un semi-conducteur indirect, le faible coefﬁcient d’absorption en combinaison avec une dotation élevée et une petite longueur de diffusion de trou ont été déterminés comme les facteurs limitant. Un ﬁlm épitaxial additionnel de carbure de silicium n-cubique a entraîné une augmentation signiﬁante du courant photoélectrique maximal.La tension photoélectrique réalisable et les pertes dues aux recombinaisons dépendent principalement des propriétés de surface. L’utilisation des minces couches de catalyseur s’est révélé prometteur pour améliorer les deux propriétés même si cette technique a besoin d'optimisation parce que des états défectueux à l’interface limitent la tension photoélectrique
The goal of this work was to investigate cubic silicon carbide as anode material for direct photoelectrochemical water splitting. From the performed measurements (mostly photoelectron spectroscopy, electrochemical measurements, Raman and UV-Vis spectroscopy) n-type cubic silicon carbide’s low oxygen evolution efficiency could be related to some fundamental problems.Primarily, the attainable photocurrent is limited by the ﬂux of photo generated holes to the semiconductor surface. As cubic silicon carbide is a indirect semiconductor, the low absorption coefﬁcient in combination with a high doping concentration and low hole diffusion length were determined as limiting factors. An additional epitaxial n- cubic silicon carbide ﬁlm resulted in a signiﬁcant improvement of the photocurrent.The obtainable photovoltage and recombination losses are mostly dependent on the surface properties. While a buried junction between the silicon carbide and a thin catalyst layer has proven to be promising for improving both properties, it still needs optimization, as Fermi level pinning from interface defect states drastically reduces the photovoltage

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30

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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31

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.

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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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32

Yilmaz, P. "Photoelectrochemical performance of catalyst systems based on Pd deposited TiO2 and Ag incorporated BiFeO3." Thesis, Queen Mary, University of London, 2016. http://qmro.qmul.ac.uk/xmlui/handle/123456789/18403.

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Since the discovery of titanium dioxide's (TiO2) capability for water-splitting and photocatalytic degradation of organic compounds, semiconductor photocatalysis has received great attention and promises an environmentally clean and sustainable solution by solar hydrogen production and waste water treatment.1,2 In this thesis, the photocatalytic performance of two different photocatalyst systems based on Pd nanoparticle decorated n-type TiO2 nanorods and Ag incorporated ptype BiFeO3 thin films were investigated for solar hydrogen and oxygen production and photodecolourisation of a common textile dye, Rhodamine B. High surface area TiO2 nanorods were grown on glass fibre substrates by a hydrothermal method to produce a mechanically robust photocatalytic filter. Metallic Pd nanoparticles were deposited onto TiO2 nanorods via a photochemical method. It was found that the hybrid Pd/TiO2 catalyst system showed higher photoactivity with a doubled kinetic rate for the photodecolourisation of RhB. Full decolourisation has been achieved in 180 minutes with as-grown TiO2 nanorods whereas this time was reduced to only 90 minutes for the Pd/TiO2 hybrid catalyst. This enhancement was associated with the localised surface plasmon resonance (LSPR) effect due to the interaction of Pd with visible light and the electron scavenging role of Pd for efficient charge separation. The same hybrid Pd/TiO2 photocatalyst system was then developed on FTO coated glass substrates so that the photoelectrochemical experiments can be carried out using a potentiostat. Mott-Schottky curves demonstrated a positive shift in flat band potential and an increased charge carrier density after Pd deposition. The facilitated charge transfer at the interface of Pd and TiO2 was shown by EIS data with a smaller arc size for Pd/TiO2 in Nyquist plots. The photoelectrochemical performance of the bare TiO2 and hybrid Pd/TiO2 samples were compared through the photoelectrocatalysis of Rhodamine B (RhB) and solar hydrogen production in different electrolyte solutions at various applied voltage values. A higher amount of hydrogen by Pd/TiO2 was photogenerated in methanol solution whereas bare TiO2 produced a higher amount of hydrogen in 0.01M Na2SO4 and pure deionised water under the same conditions. The results were discussed by proposing possible reaction mechanisms with an emphasis on the charge trapping role of Pd nanoparticles. P-type BiFeO3 (BFO) thin films were deposited on large scale FTO coated glass substrates by a sol-gel method. A photocurrent density of -0.004mA/cm2 was achieved at 0V vs NHE under AM1.5 G illumination and 1.2μmol of O2 was produced in 2h at an external bias of -0.5V vs Ag/AgCl. These values were significantly increased upon the incorporation of Ag into the BFO matrix. Ag was incorporated into the BiFeO3 matrix at different concentrations as metallic Ag structures and Ag nanowires. The enhancement by Ag modification was attributed to enhanced light absorption due to light scattering effect and efficient charge separation by Ag as they act as electron sinks. These explanations were supported by shifts in flat band and onset potentials after Ag modification in detailed measurements of Mott-Schottky plots and j-v curves.

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33

Parra, Puerto Andrés. "Towards Artificial Photosynthesis: Photoelectrochemical CO2 Reduction to Solar Fuels." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/347965.

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This thesis is devoted to prove the concept of the CO(2) reduction to CH(4) with a decreasing in the voltage requirements using a photocatalytic mechanism. Subsequently, part of the solar energy is transferred to the reaction, obtaining an improvement in the total energy balance. The work developed intends first, to take advantage of the know features of the photoactive nanostructured materials obtained by anodization and hydrothermal synthesis (allowing to obtain better surface areas and improving the photon collection, light photosynthetic reactions). Second investigate the copper and copper oxide cathodes for the CO(2) electroreduction activity to CH(4) (dark photosynthetic reactions) using a complete cell to understand the parameters involved in the process and the products selectivity for each cathodes. And third the implementation of the photoanode and cathode in a photoelectrochemical complete cell. Respect the photoactive materials we are going to talk about TiO(2) based nanostructured materials for water splitting. The first TiO(2) nanostructuration under study are nanotubes obtained by anodization of a Titanium foil using organic electrolytes. The TiO(2) crystal phase obtained by this technique was anatase. The next step in this material was the surface modification to improve the efficiency. To obtain this improvement the anodization process was done using two electrolytes in different steps. As sequence a porous surface with an increment in the surface area was obtained. After, the photoelectrochemical measurements were done in 1 M of sodium hydroxide (NaOH) under AM 1.5G illumination source to observe the photoactivity of these samples. The second nanostructured materials under study were TiO(2) nanorods obtained by hydrothermal synthesis over a conductive glass substrate, Fluorine Tin Oxide (FTO). The nanorods using this technique have rutile structure. An optimization of two parameters involved in the hydrothermal synthesis was studied: (1) initial titanium precursor concentration and (2) increasing the chlorine concentration to obtain larger and thinner rods. To enhance the photoactivity of TiO(2) we try to incorporate other materials inside the structure. The materials selected were: tin which improves the charge carriers, vanadium which allows the absorption in the visible range and nitrogen doping to enhance the efficiency in the photoactivity of the material. Concerning to methane production study, a discussion about the electrochemical CO(2) reduction activity over a copper based electrode using a hydrogen carbonate as supporting electrolyte was done, where the positive ions used are sodium and potassium. The first electrode selected is a pristine copper due to the interest of the methane production. The samples were characterized by scanning electronic microscopy (SEM) and X-Ray diffraction (XRD) to visualize the surface morphology and the crystal structure of the electrode. Afterwards, the electrochemical process is studied to understand the activity of these electrodes. Chronopotentiostatic (CP) experiments were done at different current densities to observe the activity as a function of the reached potential. The second electrode under study was a copper oxide cathode. In the electrochemical experiments an effect was studied related to the electrochemical reduction of the different copper oxide layers generated during the thermal synthesis, leading to a catalytically active copper that enables carbon dioxide reduction. With this type of electrodes a time- dependence test was done to carefully study these crystallographic changes. Finally, another important variable for CO(2) conversion was studied, the humidification of the CO(2) gas stream before the introduction in the electrochemical cell with the impact on the faradaic efficiency of the process. In the implementation in the PEC cell an evaluation of the photoanode and cathode was done. In this evaluation, the external potential requirements were studied concerning about the energy consumption and the benefit from the photoactivated process.
Esta tesis se ha desarrollado con el objetivo de probar el concepto de la reducción del dióxido de carbono a metano, mediante una reducción de los potenciales necesarios usando un mecanismo fotocatalítico. Parte de la energía solar es transferida a la reacción obteniendo una mejora en el balance energético total. El trabajo desarrollado se focaliza primero en el estudio de materiales nanoestructurados fotoactivos basados en dióxido de titanio obtenidos por anodización, generando nanotubos, y por síntesis hidrotermal obteniendo nanohilos sobre un sustrato conductor transparente, los cuales permiten obtener mayores superficies activas mejorando la colección de fotones, similar a las reacciones luminosas en la fotosíntesis. En segundo lugar, se ha estudiado la electroreducción del dióxido de carbono a metano usando cátodos de cobre y oxido de cobre (similar a las reacciones oscuras de la fotosíntesis). Usando el cobre como cátodo, se ha observado la obtención de metano a diferentes densidades de corriente aplicadas para poder observar la productividad respecto al potencial medido. Para el caso de los cátodos de óxido de cobre, no se ha encontrado producción de metano pero si de etileno. En estos cátodos se ha observado un efecto proveniente de la reducción de las capas de los diferentes óxidos de cobre, generados en la síntesis térmica, hacia un cobre catalíticamente activo para la reacción de reducción del dióxido de carbono. Este efecto se ha estudiado profundamente mediante un estudio de los cambios cristalográficos y superficiales a determinados tiempos. Finalmente, se ha estudiado el efecto de la humidificación del dióxido de carbono (gas) previa a la entrada a la celda electroquímica. Como parte final se ha realizado una evaluación energética de los fotoánodos generados por síntesis hidrotermal y de los cátodos basados en cobre estudiados, para poder implementar ambos en una celda fotoelectroquímica completa. En esta parte se ha estudiado los valores de los potenciales externos necesarios para que se pueda dar la reacción, asumiendo un 100% de eficiencia hacia la producción de metano para los cátodos de cobre y de etileno para los de óxido de cobre.

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34

Hedbor, Sigrid, and Linnéa Klar. "Plant Extract Sensitised Nanoporous TiO2 Thin Film Photoelectrochemical Cells." Thesis, Uppsala University, Department of Earth Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-88885.

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För att undersöka skillnad i prestationsförmåga mellan celler sensiterade med växtextraktsbaserad färg, och celler sensiterademed ruteniumkomplex-baserad färg, samt huruvida presskraften påverkar en cells prestationsförmåga, tillverkades icke-slutna fotoelektrokemiska färg-sensiterade solceller med tunnfilmsfotoelektroder av pressad, nanoporös titandioxid.

Cellerna pressades med tre olika presskrafter och sensiterades med växtextraktsfärg från rödkål, rödbeta, viol och henna, samt en ruteniumkomplex-baserad färg som fick utgöra kontrollbetingelse. För varje cell uppmättes IPCE- och iV-värde och motsvarande fyllnadsgrad (fill factor) och dessa jämfördes.

Ingen signifikant skillnad kunde fastställas mellan celler pressade med olika presstryck. Bland cellerna sensiterade med växtextraktbaserad färg presterade rödbeta bäst. Cellen med högst effektivitet hade fyllnadsgraden 70%. Emellertid uppvisade de växtfärgade cellerna genomgående sämre effektivitet än de rutenium-sensiterade och fotoströmmarna var mycket låga. IPCE-värdena var allmännt låga: den bäst presterande cellen hade ett IPCE-värde på något över 0,06 i våglängdsintervallet 440-470 nm. En förklaring till detta är de övriga ämnen som förutom pigment återfinns i de växtbaserade färgerna. Dessa hindrar pigmentmättnad och förhindrar att växtfärgen når ruteniumfärgens intensitet. En annan anledning består i svårigheten att passa ihop energinivåerna i cellens elektrolyt-halvledarsystem med energinivåerna hos pigmentet i växtfärgen.

Non-sealed photoelectrochemical dye sensitised solar cells (DSSC) with pressed nanoporous TiO2 thin film photoelectrodes were manufactured for the purposes of finding out whether plant extractbased dye sensitised cells can perform as well as ruthenium complex-based dye sensitised cells and whether the pressing force affects the cell performance.

The cells were pressed with three different pressing forces and sensitised with plant extracts from red cabbage, beetroot, violet and henna, as well as with a ruthenium complex-based dye for comparison. The IPCE and iV values and the corresponding fill factors of the cells were evaluated and compared.

No significant difference between the cells pressed with different pressing forces could be established. Among the plant extract-based dye sensitised cells the ones sensitised with beetroot extract performed best. The cell that achieved the highest efficiency had a fill factor of 70%. Compared to the ruthenium-sensitised cells the overall performance of the plant dye sensitised cells were very poor and the produced photocurrents very low. The IPCE values were generally low: one of the best-performing cells had an IPCE value of slightly over 0.06 in the 440-470 nm wavelength ranges. One reason for this is that it is difficult to obtain a plant extract dye as intense and deep in colour as ruthenium complex-based dyes, since pigment saturation is obstructed by the presence of other chemical compounds in the plant extracts. Another is that it is a delicate and difficult matter to match the energy levels in the electrolyte-semiconductor system with the energy levels of the pigments in the plant extract dye.

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35

Rodríguez, Rodríguez Juan Martín. "Sputter deposited titanium oxide films for photoelectrochemical water purification." Universidad Nacional de Ingeniería. Programa Cybertesis PERÚ, 2000. http://cybertesis.uni.edu.pe/uni/2000/rodriguez_rj/html/index-frames.html.

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Non-stoichiometric polycrystalline Ti oxide thin films were prepared by reactive DC magnetron sputtering of Ti in Q2+Ar. Sputtered Ti oxide samples with four values of the film thickness were investigated by transmission electron microscopy (TEM) Cross-sections of (he specimens shows thai iheir most salienl feature is a parallel penniform structure extending over che fall cross-sections of the films. A very large intemal surface is manifest Rutile and anatase phase films were obtained by heating the substraia during the deposition. Incident photon-to-currem efficiency (IPCE) was studied as a function of several spuuenng parameters such as temperature of the substrate, film thickness, and 02/Ar gas flow ratio. The IPCE increased as the crystallinity of Ti oxide was systematically varied from amorphous to a mixture of analise and rutile, and it was also enhanced in films depositad at !ow O2/Ar ratios. The photogenerated current was found to be highly dependen on the composition, thickness, and structure of Ti oxide films. Optical constans of the films were determined from spectrophotometric measuremems of reflectante and transmittance. The amorphous films had a band gap of -3.4 cV and a wide absorption tail extending 10 lower energics. The crystalime films displayed a band gap of 3,3-3.35 eV and a more narrow absorption tail. The optical constants were dependem on film ihickness The crystalline films showed evidence of structural inhomogeneilics Icading to diffuse scatiering in the thicker films as well as to a grading of the refraciive Index. The complex dielectric permittivity £ was determined in the 10'3 to 107 H2 range from measurements using a capacitor configuration. The real and imaginary parts of s displayed power-law dependencies from - 10 Hz up to a value between 1 and 10 kHz, Our data could be rationalized in terms of a model for screened hopping of vacancy-inouced charge carriers, but details remain poorly undcrstood. The internal surface area was enhanced with increasing film ihickness, and that property could be correlated with an enlarged photoelectric conversión eficiency. Ti oxide films with thicknesses in the 1,9-8.0-mm range were sputter deposited orno etectrically conductive transparenl glass substrates. X-ray diftraction indicated a dominating rutile structure. The films were used to investigate photo-electrocatalytic degradation of 4-chlorophenol in water solution, employing a specially designed reactor. ITV light was used for (he photocatalysis, and a bias potential was applied for avoiding electron-hole recombination. The photocurrent and the kineiics of the catalytic reaaion were tested with potentiosiatic and spectrophotometric measurements, The reaction producis were investigated using different arrangements of a Ti oxide working electrode and a Pt counter electrode, IA irradiation through the gfass substrate yielded an enhancement of the reaction kinetics for increased film thicknesses and applied bias potential. X-ray diffractomeiry showed that nitile-like and anatase-Hke films were produced depending on the oxygen conteni in the sputter plasma. Rutherford backscatiering spectrometry documented some oxygen overstoichiometry. Spectral optical measurements were used to analyze the absorption around ihe fundamentari band gap and lo give evidence of some hydration and hydroxylation in ihe films. The various Ti oxide films were broughi in contact wiih 4--chlorophenol (4-CP), whose photo-electrocatlytically induced degradation under ukraviolet irradiation was investigated in a reacior allowing optical probing of 4-CP as well as of intermediate reaction products such as benzoquinone. A miile-üke structure was conductive to the degradation of 4-CP, which can be reconciled with the band gap being suitable for producing photoinduced heles capable 10 effecting oxidation of the pollutant.

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36

Sugunan, Abhilash. "Fabrication and Photoelectrochemical Applications of II-VI Semiconductor Nanomaterials." Doctoral thesis, KTH, Funktionella material, FNM, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95410.

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In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdE (E=Te,Se,S) quantum structures synthesized by solution-based thermal decomposition of organo-metallic precursors. We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. We have extended this method wherein nanofibers of poly-L-lactide act as a substrate for the radially oriented growth of ZnO nanowires. By combining the large surface area and the flexibility of the PLLA-ZnO hierarchical nanostructure we have shown the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system to decompose known organic pollutants in water, as well as render common waterborne bacteria non-viable. We have studied synthesis of colloidal quantum dots (QD), and show size, morphology and composition tailored nanocrystals for CdE (E=S, Se, Te) compositions. We have studied the influence of crystal growth habits of the nanocrtsyals on the final morphology. Furthermore we have synthesized core-shell, CdSe-CdS QDs with spherical and tetrahedral morphologies by varying the reaction conditions. We show that these core-shell quantum dots show quasi-type II characteristics, and demonstrate with I-V measurements, the spatial localization of the charge carriers in these hetero-nanocrystals. For this purpose, we developed hybrid materials consisting of the core-shell quantum dots with electron acceptors (ZnO nanowires) and hole acceptors (polymeric P3HT nanofibers). In addition we have also compared the synthesis reaction when carried out with conventional heating and microwave-mediated heating. We find that the reaction is enhanced, and the yield is qualitatively better when using microwave induced heating.
QC 20120525

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37

Jami, Maryam [Verfasser]. "Nanocrystalline materials for (solar) photoelectrochemical water splitting / Maryam Jami." Hannover : Technische Informationsbibliothek (TIB), 2017. http://d-nb.info/1141305631/34.

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38

Kucernak, Anthony Robert John. "Scanning laser photoelectrochemical studies of oxide films on metals." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305577.

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39

Buchanan, J. S. "Electrochemical and photoelectrochemical studies of anodic films on lead." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356528.

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40

Campbell, S. A. "Structural and photoelectrochemical studies of electrodeposited lead dioxide films." Thesis, University of Southampton, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378266.

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41

Mlcak, Richard. "Electrochemical and photoelectrochemical micromachining of silicon in HF electroytes." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37526.

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42

Katz, Jordan E. Okumura Mitchio Lewis Nathan Saul. "Metal oxide-based photoelectrochemical cells for solar energy conversion /." Diss., Pasadena, Calif. : California Institute of Technology, 2008. http://resolver.caltech.edu/CaltechETD:etd-10192007-190231.

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43

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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44

Zhang, Xuemei. "Solution-processed nanomaterials for applications in photoelectrochemical solar cells." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/58236.

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Quaternary Cu2ZnSnS4 (CZTS) and binary Bi2S3 are considered as potential photovoltaic materials due to their suitable electronic and optical properties, low-toxicity and earth-abundant elemental constitution. This thesis investigates the preparation of CZTS and Bi2S3 nanocrystals in solution-based approaches and examines their applicability in photoelectrochemical solar cells with an aim of fabricating low-cost photovoltaics. CZTS nanocrystals with the kesterite crystal structure were prepared by a hot-injection method in which elemental sulfur was used as the sulfur source. The synthetic conditions were optimized in order to obtain high-quality CZTS particles. The kesterite CZTS nanocrystals were explored as both the sensitizers in photoanode and the building blocks for fabricating thin films. CZTS sensitized TiO2 thin films were used as photoanodes in semiconductor sensitized solar cells (SSSCs); CZTS nanocrystal thin films were employed as photocathodes in dye sensitized solar cells (DSSCs). In addition, wurtzite CZTS nanocrystals were also synthesized by a hot-injection method in which an alternative sulfur source, dodecanethiol, was used. In order to examine the influence of metal nanoparticles on the performance of CZTS photocathodes, Au nanoparticles were introduced in the synthesis which led to the formation of core-shell Au@wurtzite CZTS nanoparticles. The performance of those core-shell nanoparticles as a photocathode material was tested in DSSCs. A novel method was developed for the in-situ preparation and deposition of Bi2S3 nanocrystals in the porous TiO2 thin films. Photoresponse studies showed that the in-situ generated Bi2S3 nanoparticles function as good sensitizers to TiO2 thin films. The Bi2S3 sensitized TiO2 thin films were investigated as photoanodes in SSSCs.

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45

Viger, Marie-Élise. "Photoelectrochemical degradation of ciprofloxacin." 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92310.

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46

Hwang, Jung-Min, and 黃忠民. "Photoelectrochemical etching in GaN." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/75265564757670744155.

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碩士
國立清華大學
電機工程學系
87
Etching in GaN is an important priori for device processing due to the chemical inertness, hardness, and easily introducing damage in device process. The plasma/energetic ion etching with high reactive gas will provide a smooth etching bottom and vertical sidewall. But the ion bombardment induced damage will degrade the device performance. Another disadvantage was the different volatility of Ga and N reactant which will produce a non-stoichiometric surface. The damaged surface will limit the device application. So a mild etching process of wet etching was considered. Due to the chemical inertness of GaN, chemical wet etching can not be used for etching process, although wet etching is a low damage etching technology. From the discussion above, we want to find an etching process with high etching rate, smooth etching surface, vertical sidewall and near damage free for etching GaN. In this thesis, photoelectrochemical (PEC) etching GaN was shown to yield high etching rate comparable with dry etching and vertical sidewall. But the enhancement in etching surface roughness and etching induced damage related to yellow luminescence also appeared in this etching process. The boiled KOH solution was used to remove the PEC etching damage successfully from the PL identification. The etching surface was also smoothed by post-treatment with boiled KOH solution. Another important contribution is the rapidly identify threading dislocation density of the film by PEC etching. From selective etching of the threading dislocation and crystalline GaN, we could rapidly identify the dislocation density without using the TEM. We also use this skill to identify the dislocation related luminescence. This is the first report on the origin of this dislocation related PL peak. In this work, we have developed an etching process of PEC etching with boiled KOH solution to obtain a high etching rate, smoothing etching surface, vertical sidewall and near damage free etching. We also showed the etching mechanism and studied the etching damage. The etching process could be applied for device processing, laser cavity formation, nanostructure fabrication and surface damage removal.

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Liu, Ching-Fang, and 劉靜芳. "Coupling photoelectrochemical catalysis and photoelectrochemical Fenton process for the treatment of dye industrial wastewater." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/26227799481044786150.

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博士
國立交通大學
環境工程系所
104
In recent years, advanced oxidation techniques including electrochemical advanced oxidation processes (EAOP) have gained much attention. EAOP have been employed widely for the decontamination of wastewaters containing high-strength organic pollutants due to their versatility, high efficiency, and environmental compatibility. The effectiveness of EAOP such as photoelectrochemical catalysis (PEC), electro-Fenton (EF) and photoelectro-Fenton (PEF) are ascribed to the generation of hydroxyl radicals (OH•), which has a high redox potential that can react non-selectively with most organic compounds to produce CO2, water, and inorganic ions. Recently, many coupled and hybrid electrochemical processes have been proposed aiming developing more powerful processes for dyes removal. It provides more advantages than individual electrochemical processes owing to the high degradation performance on the treatment of wastewater via combined different electrochemical methods. Therefore, the purpose of this thesis was to develop the coupled PEC/PEF process by combining TiO2/Ti and stainless steel dual anode system. In the first parts of this study, the TiO2/Ti and stainless steel anodes would be integrated individually. After that, the combining both anodes with coupled PEC/PEF process for treatment of dye wastewater treatment was integrated in the second part of this study. The first part was the integration of TiO2/Ti photoanode, the TiO2/Ti photoanode was prepared by electrophoretic deposition (EPD) process. The performance of TiO2/Ti photoanode was tested by degradation of azo dye Orange G (OG) using a PEC system. Results of surface analysis and electrochemical analysis revealed that the optimal EPD condition was a deposition potential of 180 V for 1 min and annealed at 350oC. These results showed that the coupling effect of photocatalytic and electrochemical oxidation processes was evaluated in terms of the decolorization of OG. The degradation of OG increased in the following increasing order: photocatalysis (PC) < electrochemical oxidation (EO) < PEC. The degradation of OG follows the pseudo first-order kinetic in PEC process, which proposed the OH radical is the major player in the decolorization reaction. The second part was the integration of stainless steel (SS) anode and graphite cathode system with EF and PEF processes. In this system, the ferrous ions being derived from a sacrificial stainless steel anode and hydrogen peroxide being produced at a graphite cathode. Results indicated that the applied current controlled the rate of electrogeneration of ferrous ion and hydrogen peroxide. The optimal [H2O2]/[Fe2+] (molar) ratio was 3.58 at an applied current density of 45 uA/cm2 for the SS-graphite system. The OG degradation efficiency in the PEF process was greater than that of the EF process under otherwise identical conditions. At an applied current density of 45 uA/cm2, stainless steel anode achieved a decolorization of 85% after 3 h. The degradation of OG followed the pseudo first-order kinetics for both EF and PEF processes, which proposed that OH radical was a main species for the decolorization reaction. For coupling the PEC and PEF two processes, the dual anode electrochemical system by combining the TiO2/Ti and stainless steel was developed for OG treatment. From the result of kinetic aspect, the efficiency of the PEC/PEF process depended on the Fe2+ and H2O2 electrogeneration which yielded OH radical in the solution bulk, which could promote the oxidative degradation of OG and its byproducts. The degradation of OG increased in the following increasing order: photocatalysis < electrochemical oxidation < photoelectrochemical degradation < electro-Fenton < photoelectro-Fenton < coupling the photoelechemical and photoelectro-Fenton. After the 7 h reaction time, a decolorization of 99.8% and TOC removal of 70% were achieved at an applied current density of TiO2/Ti and stainless steel anodes were 75 uA/cm2 and 45 uA/cm2. The degradation of OG following the pseudo first-order kinetic for PEC/PEF process.

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48

Chao, Wei-Chung, and 趙維中. "Flow-Enhanced Photoelectrochemical Hydrogen Production." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/wg7799.

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49

Yang, Bo. "Micromachining of GaN using photoelectrochemical etching." 2005. http://etd.nd.edu/ETD-db/theses/available/etd-06292005-130851/.

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50

Azevedo, João Carlos Almeida Monteiro. "Solar Photoelectrochemical Energy Storage: Materials Devices." Doctoral thesis, 2016. https://repositorio-aberto.up.pt/handle/10216/94736.

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Dissertations / Theses on the topic 'Photoelectrochemical'

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