Tesis sobre el tema "Electrolysi"
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Melane, Xolani. "Visualisation of electrolyte flow fields in an electrolysis cell". Diss., University of Pretoria, 2015. http://hdl.handle.net/2263/57492.
Texto completoDissertation (MEng)--University of Pretoria, 2015.
tm2016
Chemical Engineering
MEng
Unrestricted
Klose, Carolin [Verfasser], Stefan [Akademischer Betreuer] Glunz y Simon [Akademischer Betreuer] Thiele. "Novel polymer electrolyte membrane compositions for electrolysis and fuel cell systems". Freiburg : Universität, 2020. http://d-nb.info/1208148036/34.
Texto completoSathe, Nilesh. "Assessment of coal and graphite electrolysis". Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1147975951.
Texto completoSahar, Abdallah. "Etude par analyse spectrale de processus aux electrodes fortement aleatoires". Paris 6, 1988. http://www.theses.fr/1988PA066522.
Texto completoNi, Meng y 倪萌. "Mathematical modeling of solid oxide steam electrolyzer for hydrogen production". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39011409.
Texto completoSIRACUSANO, STEFANIA. "Development and characterization of catalysts for electrolytic hydrogen production and chlor–alkali electrolysis cells". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1337.
Texto completoThe topics of this PhD thesis are concerning with Chlor alkali electrolysis and PEM water electrolysis. • Chlor alkali electrolysis. The industrial production of chlorine is today essentially achieved through sodium chloride electrolysis, with only a minor quantity coming from hydrochloric acid electrolysis. The main problem of all these processes is the high electric energy consumption which usually represents a substantial part of the total production cost. Therefore, in order to improve the process, it is necessary to reduce the power consumption. The substitution of the traditional hydrogen-evolving cathodes with an oxygen-consuming gas diffusion electrode (GDE) involves a new reaction that reduces the thermodynamic cell voltage and leads to an energy savings of 30-40%. My research activity was addressed to the investigation of the oxygen reduction at gas-diffusion electrodes as well as to the surface and morphology analysis of the electrocatalysts. Specific attention was focused on deactivation phenomena involving this type of GDE configuration. The catalysts used in this study were based on a mixture of micronized silver particles and PTFE binder. In this study, fresh gas diffusion electrodes were compared with electrodes tested at different times in a chlor-alkali cell. Electrode stability was investigated by life-time tests. The surface of the gas diffusion electrodes was analyzed for both fresh and used cathodes by scanning electron microscopy and X-ray photoelectron spectroscopy. The bulk of gas diffusion electrodes was investigated by X-ray diffraction and thermogravimetric analysis. • PEM water electrolysis. Water electrolysis is one of the few processes where hydrogen can be produced from renewable energy sources such as photovoltaic or wind energy without evolution of CO2. In particular, an SPE electrolyser is considered as a promising methodology for producing hydrogen as an alternative to the conventional alkaline water electrolysis. A PEM electrolyser possesses certain advantages compared with the classical alkaline process in terms of simplicity, high energy efficiency and specific production capacity. This system utilizes the well know technology of fuel cells based on proton conducting solid electrolytes. Unfortunately, electrochemical water splitting is associated with substantial energy loss, mainly due to the high over-potentials at the oxygen-evolving anode. It is therefore important to find the optimal oxygen-evolving electro-catalyst in order to minimize the energy loss. Typically, platinum is used at the cathode for the hydrogen evolution reaction (HER) and Ir or Ru oxides are used at the anode for the oxygen evolution reaction (OER). These metal oxides are required, compared to the metallic platinum, because they offer a high activity, a better long-term stability and less efficiency losses due to corrosion or poisoning. My work was mainly addressed to a) the synthesis and characterisation of IrO2 and RuO2 anodes; b) conducting Ti-suboxides support based on a high surface area. a) Nanosized IrO2 and RuO2 catalysts were prepared by using a colloidal process at 100°C; the resulting hydroxides were then calcined at various temperatures. The attention was focused on the effect of thermal treatments on the crystallographic structure and particle size of these catalysts and how these properties may influence the performance of oxygen evolution electrode. Electrochemical characterizations were carried out by polarization curves, impedance spectroscopy and chrono-amperometric measurements. b) A novel chemical route for the preparation of titanium suboxides (TinO2n−1) with Magneli phase was developed. The relevant characteristics of the materials were evaluated under operating conditions, in a solid polymer electrolyte (SPE) electrolyser, and compared to those of the commercial Ebonex®. The same IrO2 active phase was used in both systems as electrocatalyst.
Owais, Ashour A. [Verfasser]. "Packed Bed Electrolysis for Production of Electrolytic Copper Powder from Electronic Scrap / Ashour A Owais". Aachen : Shaker, 2003. http://d-nb.info/1181600782/34.
Texto completoSoundiramourty, Anuradha. "Towards the low temperature reduction of carbon dioxide using a polymer electrolyte membrane electrolysis cell". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112174.
Texto completoThe main objective of this research work was to put into evidence the electrocatalytic activity of various molecular compounds with regard to the electrochemical reduction of carbon dioxide, at low temperature, in view of potential application in PEM cells. First, reference values have been measured on copper and nickel metals. Then the performances of some molecular compounds have been measured. The electrochemical activity of these different compounds has been put into evidence by recording the current-potential relationships in various media. The role of a hydrogen source for the reduction processes has been evaluated. The formation of reduction products has been put into evidence and analyzed by gas phase chromatography. Then, a PEM cell has been developed and preliminary tests have been performed. PEM cells with either an oxygen-evolving anode or a hydrogen-consuming anode have been tested. Using nickel molecular complexes, it has been possible to lower the potential of the cathode and to reduce CO₂ but the parasite hydrogen evolution reaction was found to remain predominant
Owais, Ashour [Verfasser]. "Packed Bed Electrolysis for Production of Electrolytic Copper Powder from Electronic Scrap / Ashour A Owais". Aachen : Shaker, 2003. http://d-nb.info/1181600782/34.
Texto completoGoñi, Urtiaga Asier. "Cesium dihydrogen phosphate as electrolyte for intermediate temperature proton exchange membrane water electrolysis (IT-PEMWE)". Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2490.
Texto completoSoleimany, Mehranjani Alireza. "Tape casting of ceramic GDC/YSZ bi-layer electrolyte supports for high temperature co-electrolysis". Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/17600/.
Texto completoLou, Ning. "A Study on Electrolyte Optimization by Adopting Additives in Electrolytic In-Process Dressing (ELID)". University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1271452998.
Texto completoWatkins, Luke. "Development of non-noble catalysts for hydrogen and oxygen evolution in alkaline polymer electrolyte membrane electrolysis". Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2296.
Texto completoDunleavy, Christopher Squire. "Development of quantitative techniques for the study of discharge events during plasma electrolytic oxidation processes". Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/228637.
Texto completoKarakurkchi, A. V., N. D. Sakhnenko, M. V. Ved y A. S. Gorohivskiy. "Nanostructured catalytic cobalt containing PEO-coatings on alloy AL25". Thesis, Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22609.
Texto completoFawcett, Lydia. "Electrochemical performance and compatibility of La2NiO4+δ electrode material with La0.8Sr0.2Ga0.8Mg0.2O3-δ electrolyte for solid oxide electrolysis". Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24667.
Texto completoDumortier, Mikaël. "Modélisation numérique des transferts de matière, de chaleur et électrochimiques au sein d'un électrolyseur haute température". Thesis, Montpellier 2, 2013. http://www.theses.fr/2012MON20127/document.
Texto completoHigh temperature electrolysis of water by using proton conducting ceramic membranes is an interesting process for producing hydrogen. This process can be carried out without noble catalysts and produces pure hydrogen and requires less electricity than classical low temperature electrolysis. The future development of such membrane reactors requires increasing efforts on numerical simulation in order to optimize the heat and mass transfers as well as the design of electrolysis cells. This work presents a set of equations selected from the literature and rigorously demonstrated for the description of transport phenomena in the cell and particularly in the electrodes which are made of cermets. From this model, a parametric study is conducted in order to characterize the influence of various operating parameters on these phenomena. The different findings of this study provide a set of assumptions for the development of methods for simplifying the model and reducing the time of resolution. These simplified models allow analytical determination of quantities in the electrode and leads to the establishment of dimensionless numbers and characteristics length of the device
Verdin, Baptiste. "Etude d'électrodes grande surface d'électrolyseurs PEM : inhomogénéités de fonctionnement et intégration de catalyseurs innovants". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS036/document.
Texto completoHydrogen production from PEM water electrolysis will take a great place in the energy landscape for RES storage. This scale shift requires a significant increase of the nominal power, and therefore an increase in size and a gain in the current density. Optimal operation (in terms of efficiency and lifetime) can be obtained only if the distribution of current lines over the electrode surface is adequately homogeneous. In this thesis, we have used for the first time a specific tool for the in-situ mapping of current and temperature in a large surface area PEM single cell. A customized S++® measuring plate, adapted to our application, has been implemented in a 250cm² PEM single cell. Electromechanical characterization of the cell has put into evidence the link between the field of clamping force and the local current density. We have shown that an optimal mechanical compression is not sufficient to homogenize current distribution. We have demonstrated that the cell design, in particular the fluid distribution, plays a major role in current distribution inhomogeneities, which recurrently form between the center and the periphery of the cell. We have also shown that during dynamic operation, current lines tend to concentrate at the center of the cell as a consequence of spatially differentiated ageing. We have developed an electrode structure that facilitates the global re-homogenization of current lines and additionally shows an increased durability. In parallel, we have developed a numerical model to calculate the distribution of current lines within the thickness of catalytic layers as a function of the geometry of the PTL. We have found that overvoltages play a major role in current distribution, and that the cathode is prone to more heterogeneities. We propose to densify the catalyst layers for a better current repartition and a lesser differentiated ageing. Key findings from single cell tests have been confirmed on a commercial stack
Schalenbach, Maximilian Verfasser], Detlef [Akademischer Betreuer] [Stolten y Eckhard [Akademischer Betreuer] Spohr. "Proton conduction and gas permeation through polymer electrolyte membranes during water electrolysis / Maximilian Schalenbach ; Detlef Stolten, Eckhard Spohr". Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/118606921X/34.
Texto completoLiu, Chang Verfasser], Werner [Akademischer Betreuer] [Lehnert y Lorenz [Akademischer Betreuer] Singheiser. "Noble metal coated porous transport layers for polymer electrolyte membrane water electrolysis / Chang Liu ; Werner Lehnert, Lorenz Singheiser". Aachen : Universitätsbibliothek der RWTH Aachen, 2021. http://d-nb.info/124069119X/34.
Texto completoSchalenbach, Maximilian [Verfasser], Detlef [Akademischer Betreuer] Stolten y Eckhard [Akademischer Betreuer] Spohr. "Proton conduction and gas permeation through polymer electrolyte membranes during water electrolysis / Maximilian Schalenbach ; Detlef Stolten, Eckhard Spohr". Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://nbn-resolving.de/urn:nbn:de:101:1-2019051406021643509245.
Texto completoRozain, Caroline. "Développement de nouveaux matériaux d’électrodes pour la production d’hydrogène par électrolyse de l’eau". Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112177/document.
Texto completoIt is expected that PEM water electrolysis will play a significant role in the hydrogen society as a key process for producing hydrogen from renewable energy sources but before this, substantial cost reductions are still required. Because of the high acidity of membrane materials used in PEM water electrolysers, expensive noble-metals or their oxides are required as electrocatalysts (platinum for hydrogen evolution and iridium for oxygen evolution). As the oxygen evolution reaction takes place with a large overpotential (anodic potential > 1.6 V) only few materials can be used to avoid corrosion. In state-of-the-art, noble metal oxides are generally used alone in the active layer with typical loadings of 2-3 mg/cm² and act as both catalyst and electronic conductor.In order to reduce the noble metal loadings and keep a good electronic conductivity of the catalytic layer, iridium can be supported onto a conductive and electrochemical stable material support. To gain more insights, several MEAs with anodes made of pure iridium oxide or 50 wt % IrO2/Ti anodes have been prepared and characterized using cyclic voltammetry and impedance spectroscopy, and by measuring polarization curves at different operating temperatures. Without the catalyst support, anodic loadings can be reduced down to 0,5 mg/cm² without any degradation in the electrochemical performances. By using anodes made of iridium oxide and titanium particles, further reductions of anodic loading can be made down to 0.1 mg/cm² with performances similar to those obtained with conventional loadings of several mg cm-2
Karakurkchi, A. V., M. V. Ved, N. D. Sakhnenko, I. Yu Yermolenko y S. I. Zyubanova. "Electroplating and functional properties of amorphous Fe-Mo(W) and Fe-Mo-W coatings". Thesis, Институт химии растворов им. Г. А. Крестова РАН, 2015. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22618.
Texto completoGonzález, Martínez Isaí [Verfasser] y Kai [Akademischer Betreuer] Sundmacher. "Hydrogen chloride electrolysis in a polymer-electrolyte-membrane reactor with oxygen-depolarized cathode / Isaí González Martínez. Betreuer: Kai Sundmacher". Magdeburg : Universitätsbibliothek, 2015. http://d-nb.info/1080560793/34.
Texto completoWauters, Cary N. "Electrolytic membrane recovery of bromine from waste gas-phase hydrogen bromide streams using a molten salt electrolyte". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/10131.
Texto completoKunovjánek, Miroslav. "Elektrolyzér pro výrobu vodíku". Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217696.
Texto completoAllanore, Antoine. "Étude expérimentale de la production de fer électrolytique en milieu alcalin : mécanisme de réduction des oxydes et développement d'une cellule". Thesis, Vandoeuvre-les-Nancy, INPL, 2007. http://www.theses.fr/2007INPL109N/document.
Texto completoIron is one of the few metals which is not industrially produced by electrolysis. The electrowinning of iron metal from its oxides in alkaline solution has been studied to develop such an ironmaking route. Two approaches have been adopted. The first one concerns the evaluation of the reaction mechanism. The study of iron ions electrochemistry in alkaline media shows that the electrodeposition of iron metal is possible. The study of a single iron oxide particle reduction reveals that a reaction of the hematite solid phase is possible. The analysis of a partially converted particle proves that magnetite is formed as an intermediate. The second field of study is dedicated to the production of iron metal in various electrochemical cells, using a suspension electrolysis process. The influence of the key operating parameters is established to assess the possible scale-up. All these elements are gathered to propose the main features of an industrial cell dedicated to the reaction
Claudel, Fabien. "Vers le développement d’électrocatalyseurs de dégagement d’oxygène actifs et stables". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAI052.
Texto completoThis thesis focuses on the study and the development of iridium-based electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzers. This work investigates in particular electrocatalyst degradation phenomena and aims at reaching an optimal OER activity-stability ratio. Various electrocatalysts (supported on high-surface area carbon, supported on doped-metal oxides and unsupported) have been synthetized and characterized by electrochemical and physico-chemical methods such as X-ray photoelectron spectroscopy, identical-location transmission electron microscopy and inductively coupled plasma mass spectrometry. Supported electrocatalysts feature stability limitations in OER conditions as revealed by agglomeration, coalescence, dissolution, and detachment of iridium oxide nanoparticles, these last two degradation mechanisms being amplified by corrosion of the carbon supports and dissolution of the elements composing the doped metal oxide supports. Unsupported electrocatalysts currently represent the best compromise between OER activity and stability. Ir(III) and Ir(V) oxides were shown to be the most active towards the OER while Ir(IV) oxide is the most stable, the least stable species being metallic iridium Ir(0). In real PEM water electrolyzers, the global electrolysis performance seems to be less impacted by the degradation of catalytic layers than the degradation of current collectors
Williams, Mario. "Characterization of platinum-group metal nanophase electrocatalysts employed in the direct methanol fuel cell and solid-polymer electrolyte electrolyser". Thesis, University of the Western Cape, 2005. http://etd.uwc.ac.za/index.php?module=etd&.
Texto completoKing, Rebecca Lynne. "Investigation of Anode Catalysts and Alternative Electrolytes for Stable Hydrogen Production from Urea Solutions". Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1275514221.
Texto completoEccleston, Kelcey L. "Solid oxide steam electrolysis for high temperature hydrogen production". Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/322.
Texto completoYang, Xuedi. "Cathode development for solid oxide electrolysis cells for high temperature hydrogen production". Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/979.
Texto completoVukasin, Julien. "Modélisation des transferts de masse et de chaleur dans une cellule d'électrolyse de production de fluor". Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT132.
Texto completoComputer modeling of heat transfer and mass transfer in an electrolytic cell for production of fluorineElectrolytic production of fluorine is a key step in uranium conversion for the nuclear industry. In order to improve this process, the work described in this dissertation aims at two main objectives: to build a numerical simulation of the electrolysis cell and to understand the cathodic hyperpolarization effect which lowers the productivity of the cell. A model coupling several physics (heat transfer with solidification, two-phase flow, electrokinetics) has been developed and experiments were made in order to evaluate unknown physical properties of the electrolyte (thermal conductivity and heat capacity at constant pressure). Experimental data were also acquired in order to assess the capacity of the model to simulate various phenomena occurring inside the cell. Eventually, a reliable 3D model of a semi-industrial R&D cell coupling the physics above mentioned has been obtained. The negative impact of the solidification of the electrolyte on the cooling system was simulated for the first time. Thanks to these experiments, it was also possible to determine the major trends which drive the cathodic hyperpolarization effect. The influence of HF mass fraction and temperature on this phenomenon was clearly shown
Palaniappan, Ramasamy. "Improving The Efficiency Of Ammonia Electrolysis For Hydrogen Production". Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1386341476.
Texto completoNemeth, Regina. "Electrolysis of chalcopyrite". Thesis, Luleå tekniska universitet, Industriell miljö- och processteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-70590.
Texto completoZwaschka, Gregor [Verfasser]. "Shining New Light on Water Electrolysis: Probing Electrolytic Water Splitting on Au and Pt with Micron Spatial and Femtosecond Temporal Resolution / Gregor Zwaschka". Berlin : Freie Universität Berlin, 2021. http://d-nb.info/1224883977/34.
Texto completoLaveissière, Marie. "Elaboration et caractérisations de revêtements élaborés par oxydation micro-arcs sur alliage de titane TA6V". Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30351.
Texto completoSurface treatments are often needed for metallic materials in order to improve their performances and broaden their scope of applications. TA6V (or grade 5) titanium alloy is used in many fields (going from biomedical to aeronautical parts) because it is light and possesses good anticorrosion and thermal properties. Nevertheless its tribological behavior needs substantial improvements that a coating may provide. The aim of this work was to prepare, using Plasma Electrolytic Oxidation (PEO), coatings on TA6V in order to improve its tribological properties. PEO is a recent and innovative electrochemical oxidation process for which growth mechanisms and accurate influence of operating parameters such as electrolyte composition or applied electrical signal, still need clarification. Systematic study of several electrolytes led to the preparation of adherent coatings with thicknesses between 5 and 60 µm. These coatings result from both electrochemical conversion of the substrate and incorporation of compounds from the electrolyte. They are composed of an amorphous phase, its proportion depending directly on the silicates quantity in the bath, and crystalline phases formed after the important rise of surface temperature during treatment. The understanding of correlations between electrolyte and coatings have limited the formation of the soft amorphous phase and favored hard crystalline structures, leading to an optimized electrolyte. The study of electrical parameters, such as frequency or treatment time, highlighted their strong influence on the coatings composition and morphology. The duty cycle influenced the chemical composition of the coatings, promoting the formation of crystalline alumina. Finally coatings prepared with PEO were mechanically tested. The presence of crystalline phases allowed the increase of the coatings Vickers hardness compared to the bare TA6V. Nevertheless, due to the PEO coatings roughness, a step of mechanical polishing post-treatment appeared necessary in order to reduce the friction coefficient and wear loss. Finally, the understanding of correlations between process parameters and coatings properties, has successfully led to the preparation of a coating with promising tribological properties, namely a friction coefficient below 0.3 and a wear loss inferior to 0.01 mm3 after 100,000 cycles, demonstrating a significant improvement in surface mechanical properties of the TA6V substrate
Wang, Yijun. "Advances in electroanalytical chemistry". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:90a0e93a-7c48-4b32-9788-5806b9f85acc.
Texto completoRahil, Abdulla. "Dispatchable operation of multiple electrolysers for demand side response and the production of hydrogen fuel : Libyan case study". Thesis, De Montfort University, 2018. http://hdl.handle.net/2086/17439.
Texto completoTreptow, Florian. "Polyaniline as electrolyte in polymer electrolyte membrane fuel cells". Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/11086.
Texto completoPierra, Mélanie. "Couplage de la fermentation sombre et de l’électrolyse microbienne pour la production d’hydrogène : formation et maintenance du biofilm électro-actif". Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20150/document.
Texto completoNowadays, alternative and sustainable solutions are proposed to avoid the use of fossil fuel. Hydrogen, which constitutes a promising energy vector, is essentially produced by fossil fuel reforming (95%). Environmentally friendly production systems have to be studied. Two main families of technologies are explored to produce hydrogen: 1) by thermochemical and electrochemical decomposition of water and 2) from different biomass sources. Among those last ones, microbial electrolysis cells (MEC) allow to produce hydrogen by electrolysis of organic matter. A MEC consists in a classical cathode, which provides hydrogen production by electrochemical reduction of water, associated to a bio-anode that oxidizes organic substrates into carbon dioxide. This process is only possible because of the anodic development of an electroactive microbial biofilm which constitutes an electrocatalyst. In comparison to classical water electrolysis process, a MEC requires 5 to 10 times less electrical energy and therefore reduces the energetic cost of produced hydrogen. Furthermore, classical process of dark fermentation in mixed cultures converts sugars (saccharose, glucose) to hydrogen with a limited yield of 2-3 moles of hydrogen per mole of hexose because of the coproduction of organic acids (mainly acetic and butyric acids). Fed with acetate, a MEC can produce up-to 3 moles of hydrogen per mole of acetate. Therefore, the association of these two processes could permit to produce 8 to 9 moles of hydrogen per mole of hexose, which represents a major step toward the theoretical limit of 12 moles of hydrogen per mole of hexose.Therefore, this work aims at analyzing the relationship between microbial community structures and compositions and the associated macroscopic functions (biofilm electroactive properties, hydrogen production potential) in electroactive biofilms and in dark fermentation in conditions allowing the coupling of the two processes. The originality of this study is to work in saline conditions (30-35 gNaCl/L), which favors the charges transfer in the MEC electrolyte.First of all, feasibility of dark fermentation in saline conditions (3-75 gNaCl/L) has been shown. This was linked to an inhibition of produced hydrogen consumption and the predominance of a new Vibrionaceae species at salt concentrations higher than 58 gNaCl/L. Secondly, electroactive biofilm growth in conditions compatibles to dark fermentation (pH 5.5-7 and fed with different organic acids) allowed to select dominant microbial species in anodic biofilms that present promising electroactive properties (Geoalkalibacter subterraneus and Desulfuromonas acetoxidans) with maximum current densities up to 8.5 A/m². In parallel, the microbial selection occurring during iron-reducing enrichment method used to select species from a natural inoculum source and based on their capacity to transfer electrons to iron oxydes (Fe(III)) has been studied. A decrease of electroactive performances of the biofilm linked to the divergence of microbial selection led to a limitation of the number of iron-enrichment steps. However, enrichment on Fe(III) presents an efficient alternative to pre-select electroactive species with an increase of coulombic efficiency from 30±4% to 99±8% in comparison with a biofilm obtained with a non-acclimated inoculum. Finally, the addition of exogenous bacteria from a dark fermenter on the electroactive biofilm revealed a decrease of electroactivity with a decrease of maximum current density produced. This diminution could be explained by a lower substrate transfer due to an apparent thickening of the biofilm. Nevertheless, the stability of microbial composition and of bacterial quantity on the anode suggests that a production of exopolymers (EPS) occurred
Giancola, Stefano. "Membranes ionomères renforcées par des nanofibres obtenues par électrofilage pour piles à combustible et l'électrolyseur". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT218.
Texto completoThe preparation of highly proton conducting and durable proton exchange membranes (PEM) for low temperature fuel cells (PEMFC) and electrolysers (PEMWE) is crucial for the large scale application of these energy conversion/storage devices. This PhD thesis focuses on the preparation and characterisation of composite membranes based on highly conducting Aquivion® short side chain perfluorosulfonic acid (PFSA) and polymer fibres obtained by electrospinning. This technique allows the preparation of highly porous mats of fibres with sub-micrometric diameters that can act as an efficient mechanical reinforcement for ionomer membranes. The chosen polymer is the mechanically robust and chemically stable polysulfone (PSU), which can also been functionalised to modify its physico-chemical properties. Reinforced PEM with fibres homogeneously dispersed through the entire membrane cross-section have been realised by a fast and efficient impregnation process.Aquivion®-PSU reinforced membranes based on PFSA with equivalent weight (EW) ranging from 700 to 870 g mol-1 and fibre loading ranging from 5 to 18 wt% have been prepared. They showed reduced volume and area swelling and higher stiffness with respect to non-reinforced membranes with the same EW. The hydrogen crossover was also reduced. The improvement in mechanical and dimensional properties was not detrimental for the in-plane proton conductivity that was kept at the same value of non-reinforced membranes. Membrane-electrode assemblies (MEA) based on these composite PEM show promising i/V characteristics in PEMWE (1.76 V at 2 A cm-2).Polysulfones functionalised with 1,2,3-triazole bearing alkyl and aryl ring substituents have been synthesized by a fast and high-yield chemical route involving the azide-alkyne cycloaddition reaction assisted by microwaves as last step. Electrospun nanofibers of polysulfone functionalised with 4-epthyl-1,2,3-triazole (PSUT) with a degree of functionalisation of 0.3 and 0.9 triazole moiety per PSUT repeat unit have been embedded into the Aquivion® matrix. The aim of this study was to further improve the mechanical properties of the membrane by PFSA-PSUT acid-base interactions (ionic crosslinking). Aquivion®-PSUT membranes showed enhanced mechanical stiffness, toughness and ductility with respect to Aquivion® membranes reinforced with the non-functionalised polymer with the same EW and fibre loading. Reduced volume and area swelling have also been observed with no drop of proton conductivity until a fibre loading of (12 wt%). MEA based on Aquivion®-PSUT reinforced membrane with 12 wt% fibre loading showed identical fuel cell polarisation curve with respect to a MEA based on Aquivion® at 80 °C and 100 % of relative humidity (RH)
Limon, Petersen Juan Gualberto. "Weakly supported voltammetry". Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:c14f972c-8653-41c2-b2d1-b080e691e4dc.
Texto completoRadel, Jason. "Electrolytic capacitive display". Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/35594.
Texto completoUdagawa, Jun. "Hydrogen production through steam electrolysis : model-based evaluation of an intermediate temperature solid oxide electrolysis cell". Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/8310.
Texto completoBARDET, JEAN-PAUL. "Contribution a l'etude de l'effet d'anode dans les electrolytes fondus tel le melange equimoleculaire licl-kcl fondu". Paris 6, 1986. http://www.theses.fr/1986PA066585.
Texto completoRoubaud, Emma. "Technologie électro-microbienne pour le traitement des eaux usées couplé à la récupération d'hydrogène". Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0091.
Texto completoA microbial electrolysis cell (MEC) supplied with wastewater simultaneously produces hydrogen with a lower energy cost than conventional electrolysis and reduces the wastewater polluting. This thesis aimed to identify the barriers hampering to the up-scaling of microbial electrolysis applied to domestic wastewater treatment and to propose optimization solutions for the various components of an MEC. The installation of a cation exchange membrane between the anode and cathode compartments made it possible to use a concentrated KHCO3 solution as the catholyte. For a current density of 10 A/m², the electro-catalytic activity of the HCO3 ions allowed reducing the cathode overpotential by 380 mV compared to domestic wastewater. A grade of industrial graphite has been selected as the most suitable material for the formation of industrial-scale bioanodes, especially for its mechanical resistance which is adapted to machining and thus creating 3D bioanodes. An electrochemical surface treatment applied to the graphite electrodes increased by 56% the current densities produced by the bioanodes formed from this treated graphite. Finally, a laboratory scale MEC prototype was designed on the basis of experimental results obtained previously during the thesis and numerical modelling work. An average hydrogen production of 3.8 L/La/j was achieved, which is 1.5 times higher than the highest production reported in the literature for MECs supplied with domestic wastewater
Stemp, Michael C. "Homogeneous catalysis in alkaline water electrolysis". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0019/MQ45844.pdf.
Texto completoEngel, Johanna Ph D. Massachusetts Institute of Technology. "Advanced photoanodes for photoassisted water electrolysis". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89856.
Texto completoThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
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Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 189-199).
With continuously growing energy demands, alternative, emission-free solar energy solutions become ever more attractive. However, to achieve sustainability, efficient conversion and storage of solar energy is imperative. Photoelectrolysis harnesses solar energy to evolve hydrogen and oxygen from water, thereby enabling energy storage via chemical means. Hematite or [alpha]-Fe₂O₃ has emerged as a highly promising photoanode candidate for photoelectrochemical cells. While significant improvements in its performance have recently been achieved, it remains unclear why the maximum photocurrents still remain well below their theoretical predictions. This study investigates the defect chemistry and conduction mechanism of hematite in order to understand and improve this material's shortcomings. A defect model for donor doped hematite was derived and its predictions conformed by the electrical conductivity of ilmenite hematite solid solution bulk samples as a function of temperature and oxygen partial pressure. The enthalpies of the Schottky defect formation and the reduction reaction for hematite were determined as 13.4 eV and 5.4 eV, respectively. In addition, a temperature independent value for the electron mobility of 0.10 cm2/Vs for 1% Ti donor doped hematite was derived. Furthermore, the electrical conductivity of nanometer scale, epitaxially grown thin films of the ilmenite hematite solid solution system was characterized by electrical impedance spectroscopy. This work reports a detailed correlation between the electrical conductivity of the undoped hematite, the 1 atom% Ti doped hematite and the thin films with higher ilmenite content and the conditions under which they were annealed (20° C=/< T =/< 800° c and 10-4 atm =/< po2 =/< atm). Hematite's room temperature conductivity can be increased from ~10-11 S/cm for undoped hematite films by as much as nine orders of magnitude by doping with the Ti donor. Furthermore, by controlling the non-stoichiometry of Ti-doped hematite, one can tune its conductivity by up to five orders of magnitude. Depending on processing conditions, donor dopants in hematite may be compensated largely by electrons or by ionic defects (Fe vacancies). The electron mobility of the film was determined to be temperature independent at 0.01 cm2/Vs for the < 0001 > epitaxial film containing a Ti donor density of 4.0 x 1020 cm-3. Finally, the photoelectrochemical performance of these materials was tested by cyclic voltammetry and measurements of their quantum efficiencies. The 1% Ti doped hematite thin film exhibited the highest photocurrent density of these dense, thin films at 0.9mA/cm2 with an applied bias of 1.5V vs. RHE. The IPCE of this sample reached 15% at wavelengths between 300nm and 350nm after an annealing treatment at 580° for 36 h. The solid solution containing 33% ilmenite preformed nearly as well as the doped hematite. The performance decreased with higher ilmenite concentrations in the solid solution. For all samples containing any ilmenite, the onset potential shifted to lower values by ~200mV after the annealing treatment. The increase in charge carrier density upon reduction of Ti doped hematite was conformed by a Mott-Schottky analysis of the hematite/electrolyte interface. In contrast, only minor changes in the carrier density were observed when reducing an undoped hematite photoanode. Changes in slope of the Mott-Schottky plots revealed the presence of deep trap states in the hematite films. In-situ UV-vis spectroscopy displayed a pronounced optical signature corresponding to the existence of such deep levels. These results highlight the importance of carefully controlling photoanode processing conditions, even when operating within the material's extrinsic dopant regime, and more generally, provide a model for the electronic properties of semiconducting metal oxide photoanodes.
by Johanna Engel.
Ph. D.
Kopecek, Radovan. "Electrolysis of Titanium in Heavy Water". PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/5023.
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