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1
Serdaroglu, Gulcan. "Controlling the microstructure of the porous nickel electrodes in alkaline electrolysers". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49141/.
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Ni-based electrodes have been extensively studied for hydrogen evolution reaction (HER) in alkaline electrolysers in an attempt to improve its electrocatalytic activity through alloying it with other metals and/or increasing the surface area. However, the role of microstructure on the electrochemical performance has received little attention. In this study, Ni-based catalysts have been prepared by a powder metallurgy technique including compaction and sintering of a mixture of Ni, starting alloy (consisting of Al3Ni and Al3Ni2) and binder. As-sintered samples were then treated in concentrated alkaline solution for leaching of Al. The microstructural properties are controlled by changing the parameters of the preparation process; i.e. sintering temperature, starting alloy to Ni ratio, leaching temperature and binder properties (concentration and particle size). Increasing the sintering temperature from 625 to 900 °C improved the mechanical strength but also increased the diffusion of Al from Al-rich phases into Ni, resulting in reduced Al-rich phases available after sintering. Since Al can only be leached from Al-rich phases, the specific surface area of micro- and mesopores (with the latter having a size range of 2-14 nm) created during the leaching reduced by almost 90 % from 625 to 900 °C sintering temperature. Although there was a ca. 15 times increase in the specific surface area by increasing the starting alloy concentration from 0 to 60 wt.%, the robustness of catalysts reduced since the compressibility of alloy powder is lower than that of Ni, resulting in increased macroporosity. This suggests that the starting alloy concentration should be in the range of 20-40 wt.% in order to achieve relatively robust and inexpensive porous catalysts without compromising too much the surface area. N2 sorption isotherms showed that leaching at 30 and 50 °C resulted in pores with a slit shape, whilst leaching at 60, 70 and 80 °C lead to ink-bottle pores. This was attributed to increasing leaching rate with higher leaching temperatures in comparison to speed of atomic rearrangement at the surface. Increasing the leaching temperature from 30 to 60 °C improved the specific surface area by almost 4 times, whilst leaching at 60, 70 and 80 °C gave similar surface areas. Greater binder concentrations led to increased macroporosity and surface roughness as well as greater numbers of windows between the adjacent cavities. Consequently, the mechanical strength of porous catalysts reduced due to the decrease in the wall thickness. It was also found that the size of the binder particles influences the robustness of the porous catalysts, with the smaller the binder size the greater the robustness. The comparison of trends in alkaline electrolyser cell voltage and compositional and microstructural properties showed that the surface area has a dominant effect on the electrocatalytic activity for HER in comparison to the composition of Ni-based electrodes. Despite greater Al contents, the cell voltage still decreased with increasing surface areas (with micropores accounting for ca. 80 %). However, it was found that the effective use of micro- and mesopores depends on the pore morphology, with slit-shaped pores being more effectively used during HER in comparison to ink-bottle pores which can be more subject to mass transport limitation. It was shown that H2 bubbles cannot form inside the micro- and mesopores, therefore generated H2 can only leave the pores through diffusion which appears to be favoured by a slit shape in comparison to ink-bottles. It was also found that increasing the amount of large macropores (> 15 μm) is not advantageous to the production of electrodes for alkaline electrolysers as it results in increased electrode thickness and reduced mechanical strength with no measureable improvement in electrochemical performance.
2
Kiaee, Mahdi. "Investigation of the cumulative impact of alkaline electrolysers on electrical power systems". Thesis, University of Strathclyde, 2016. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=26885.
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Hydrogen could be the best candidate fuel for our future, especially in the transportation sector. It could be generated using water electrolysers running with power from carbon-free, renewable resources, since this is zero emission at the point of use, and so can help transition from the energy infrastructure available today into an energy world with a growing renewable electricity supply. This work models a highly distributed electrolyser system e.g. an urban hydrogen filling station network, and explores the Demand Side Management (DSM) potential of these electrolysers to improve the performance of the power system operating under the impact of intermittent renewable power generation. A comprehensive literature review has been carried out on the hydrogen economy, electrolysers and the potential role of storage devices in power systems. Three main areas related to alkaline electrolysers working within power systems were identified for further exploration. - Potential role of electrolysers in the existing distribution networks to increase the integrated wind power capacity - Potential role of electrolysers to stabilise the frequency of the power system - Potential role of electrolysers to absorb any surplus, carbon free, generation within the UK electricity networkThe first item of archival value within this work is the identification, presentation and discussion of electrolyser characteristics which are relevant to the introduction of an acceptable control strategy to integrate such electrolyser loads within the power system and thus provide improved performance of the network when exposed to the highly time variable energy supply from renewable sources. Two types of electrolyser made by NEL Hydrogen are detailed: atmospheric and pressurised. Their characteristics are reported in this thesis using the results from experiments designed by the author. In addition, an experiment has also been carried out on a PEM electrolyser available at Strathclyde University to compare its results with the characteristics of the commercial alkaline units. Second, a novel algorithm for sizing, placing and control of electrolysis based hydrogen filling stations operating within radial distribution networks has been proposed and its performance is assessed using a United Kingdom Generic Distribution System (UKGDS) case study. The controller objective is to dispatch alkaline electrolysers appropriately to increase the amount of integrated wind power capacity and reduce the grid losses within the network while satisfying the network constraints and respecting the electrolyser characteristics. In addition, a MATLAB Simulink model has been developed to investigate the impact of alkaline electrolysers as dynamically controlled loads for the stabilisation of system frequency in the case of a sudden loss of generation and also when the power system has high penetrations of wind power. The electrolysers are controlled according to a droop control strategy. A novel approach to determine the aggregate nominal electrolysis demand for frequency stability purposes has also been proposed in this work, and the financial viability of the proposed strategy to control electrolysers has been assessed. Finally, several scenarios have been modelled to investigate the role of electrolysers to absorb surplus power and produce hydrogen for the fuel cell vehicles in the UK in the year 2050. Different wind, solar and nuclear power generation capacities have been considered. On the demand side, different penetration levels of electric vehicles and hydrogen fuel cell cars have been modelled. The results are discussed and analysed.
3
Chade, Daniel Szymon. "Performance and reliability studies of Atmospheric Plasma Spraying Raney nickel electrodes for alkaline electrolysers". Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25532.
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This PhD main aim was the examination of the Atmospheric Plasma Spraying Raney nickel electrodes samples with strong emphasis on electrochemical characterisation and investigation of the degradation/deactivation mechanisms which occur within the electrodes structure. Nowadays research in alkaline electrolysis mainly aims to improve efficiency, extend durability and decrease the price of electrolyser units. One of the methods to achieve all of these goals is the development of novel electrode types. Raney nickel electrodes manufactured by Force Technology (Denmark) using a novel atmospheric plasma spraying method (APS), have been shown to exhibit good performance with low overpotential towards the hydrogen evolution reaction (HER). In comparison to the other electrode production methods APS is considered also to be relatively cheap. To our knowledge, this is the first time APS has been applied for the production of Raney nickel electrodes for water electrolysis. APS is cheaper and simpler than actually used vacuum plasma spraying, making it more suitable for mass production of the electrodes. For a purpose of experimental work the laboratory environment was set-up which consisted of the electrochemical cells and the data acquisition devices. The methods of Tafel extrapolation, cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy were applied, that allowed to estimate electrochemical parameters of the samples. Characterisation work concluded, that overall performance of the tested samples have been attributed to the very high electrochemical active area as well as enhanced kinetics obtained for these samples following the chemical and electrochemical activation procedures Investigation of degradation mechanisms work part identified hydrides impact as a main source of deactivation for cathodes. To prevent, this effect techniques of hydrides oxidation and activation of the electrolyte were tested however, neither of them was able to eliminate hydrides impact completely. The overall work is concluded that suppressing hydrides impact should be possible by improving electrodes manufacturing process for example by application of molybdenum coatings. The performed study is supplemented by two additional outcomes. First of them is electrochemical measurement device, which concept was created and initial prototype was built using cheap electronic components. Second one is feasibility study of application of hydrogen storage technologies to increase hybrid wind energy-diesel electricity generation system efficiencies.
4
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.
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Lumanauw, Daniel. "Hydrogen bubble characterization in alkaline water electrolysis". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0017/MQ54129.pdf.
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Fiorentini, Diego. "Development of a polymeric diaphragm for Alkaline Water Electrolysis". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
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The importance of new technologies capable of providing clean energy is one of the most difficult and important challenge that science has to take up. The discovery of new green processes or the development of those already in use are common goals, which can partially solve the current climatic problems. The aim of this thesis is to extend the GVS portfolio with a polymeric separator able to improving the performances of alkaline water electrolysis (AWE) currently in use, as an alternative to separators produced by competitors. The separator consists of a membrane made of a high temperature resistant and chemically inert techno-polymer and an Inorganic filler. Once the new polymer had been studied to see how it affects the properties of the membrane and the basic information had been obtained, the influence of all the parameters in the preparation of the casting solution and the production process were analyzed. In addition, the most appropriate substrate and production method for the separator were investigated and selected in order to produce the best performing membrane possible.
Once the best separator was produced, it was possible to compare it with those produced by competitors, achieving better results in most of the analyses carried out. The prototypes were sent to companies producing cells for the Alkaline Water Electrolysis in order to validate the results obtained internally and carry out stability analyses inside the cells. The next steps after this study will be to industrialize the process developed on a laboratory scale in order to obtain a product that will benefit both the manufacturer and the environment.
7
Bradwell, David (David Johnathon). "Liquid metal batteries : ambipolar electrolysis and alkaline earth electroalloying cells". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/62741.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 198-206).
Three novel forms of liquid metal batteries were conceived, studied, and operated, and their suitability for grid-scale energy storage applications was evaluated. A ZnlITe ambipolar electrolysis cell comprising ZnTe dissolved in molten ZnCl 2 at 500 0C was first investigated by two- and three-electrode electrochemical analysis techniques. The electrochemical behavior of the melt, thermodynamic properties, and kinetic properties were evaluated. A single cell battery was constructed, demonstrating for the first time the simultaneous extraction of two different liquid metals onto electrodes of opposite polarity. Although a low open circuit voltage and high material costs make this approach unsuitable for the intended application, it was found that this electrochemical phenomenon could be utilized in a new recycling process for bimetallic semiconductors. A second type of liquid metal battery was investigated that utilized the potential difference generated by metal alloys of different compositions. MgjlSb cells of this nature were operated at 700 °C, demonstrating that liquid Sb can serve as a positive electrode. Ca,MgIIBi cells also of this nature were studied and a Ca,Mg liquid alloy was successfully used as the negative electrode, permitting the use of Ca as the electroactive species. Thermodynamic and battery performance results suggest that Ca,MgIISb cells have the potential to achieve a sufficient cell voltage, utilize earth abundant materials, and meet the demanding cost and cycle-life requirements for use in grid-scale energy storage applications.
by David J. Bradwell.
Ph.D.
8
Davids, Wafeeq. "Consolidated Nanomaterials Synthesized using Nickel micro-wires and Carbon Nanotubes". Thesis, University of the Western Cape, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_9685_1264387931.
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Law, Joseph. "The role of vanadium as a homogeneous catalyst in alkaline water electrolysis". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0020/MQ54216.pdf.
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Haug, Philipp [Verfasser]. "Experimental and theoretical investigation of gas purity in alkaline water electrolysis / Philipp Haug". München : Verlag Dr. Hut, 2019. http://d-nb.info/1181514061/34.
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Schmidt, Martin Jurgen. "Bubble phenomena in narrow gap electrolysis cells". Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322262.
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Boggs, Bryan Kenneth. "Improving Electrochemical Methods of Producing Hydrogen in Alkaline Media via Ammonia and Urea Electrolysis". Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1268668151.
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Bateni, Fazel. "Development of Non-precious Metal and Metal Oxide Electrocatalysts for an Alkaline Lignin Electrolysis Process". Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1562674707447307.
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Jia, Jingshu. "Fabrication of high quality one material anode and cathode for water electrolysis in alkaline solution /". View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?EVNG%202008%20JIA.
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Douglas, Tamunosaki Graham. "Development of an ambient temperature alkaline electrolyser for integrating with the electrical grid and renewable energy system". Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=19516.
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Electrolytic hydrogen production from an alkaline electrolyser is considered a promising energy storage technology that integrates renewable energy sources such as wind, solar, wave and tidal energy with the electrical grid. Hydrogen energy systems consisting of conventional temperature (at 80°C) alkaline electrolysers have been widely demonstrated by industry and their collaborators in academic institutions to minimise dependence on fossil fuels especially in the transport sector and thus help to ultimately reduce carbon emissions. However, the conventional temperature alkaline electrolysers are limited in terms of reliability, dynamic and fast-response operation when powered by renewable energy sources. Also, cost and safety concerns are barriers to decentralise and distribute the technology. As a result of this adds to the scepticism about the feasibility of a so called future 'hydrogen economy'. In this PhD study, an ambient temperature (at 23°C) alkaline electrolyser was investigated as part of a future integrated renewable energy system and compared with existing conventional temperature alkaline electrolyser system. The ambient temperature alkaline electrolyser is identified as a low-cost, reliable, and safe technology that is suitable for dynamic, intermittent, continuous and fast-response operation with renewable energy sources and the electrical grid. This also means the ambient temperature alkaline electrolyser is capable of wider operational range at 5%-100% of rated electrical power and faster response time in less than 1 second when powered by renewable energy sources. The auxiliary equipment are significantly reduced in the operation of ambient temperature alkaline electrolyser thereby reducing the cost of hydrogen and oxygen production and also making the technology reliable and safe for portable, stationary, transport and renewable energy system applications. Equally important is the capability of the alkaline electrolyser to efficiently convert electricity and water into hydrogen and oxygen. This is demonstrated by DC polarisation and Electrochemical Impedance Spectroscopy (EIS) analysis of the alkaline electrolyser. EIS is used to determine resistance and capacitance which are basic electrical circuit elements of the alkaline electrolyser, and thus provides useful knowledge to the electrical engineer who is interested in modelling and optimisation of alkaline electrolysers as electrical loads. Additionally, the thesis provides a systematic approach to fabricating and characterising the electrodes for the ambient temperature alkaline electrolyser that is powered directly by either renewable energy sources such as wind turbine or the electrical grid. As such, EIS has become invaluable to characterise the electrodes based on exchange current density and corrosion rates. The objective is not only to enhance energy efficiency of was investigated as part of a future integrated renewable energy system and compared with existing conventional temperature alkaline electrolyser system. The ambient temperature alkaline electrolyser is identified as a low-cost, reliable, and safe technology that is suitable for dynamic, intermittent, continuous and fast-response operation with renewable energy sources and the electrical grid. This also means the ambient temperature alkaline electrolyser is capable of wider operational range at 5%-100% of rated electrical power and faster response time in less than 1 second when powered by renewable energy sources. The auxiliary equipment are significantly reduced in the operation of ambient temperature alkaline electrolyser thereby reducing the cost of hydrogen and oxygen production and also making the technology reliable and safe for portable, stationary, transport and renewable energy system applications. the cell but to develop low-cost and durable electrodes. During this PhD work the electrodes have been characterised in an 'open-system' and flow-cell alkaline electrolyser. The 'open-system' simulates the monopolar tank-type alkaline electrolyser cell, and consists of stainless steel coated with nickel and molybdenum (SS-Ni-Mo) electro-catalyst that enhances the efficiencies for hydrogen and oxygen production. The flow-cell alkaline electrolyser has the unique advantage of modularity because the electrodes can be configured in either monopolar or bi-polar filter press arrangements. The flow-cell alkaline electrolyser is manifolded in order to capture the hydrogen and oxygen product gases that can be subsequently utilised in an alkaline fuel cell to essentially generate back electricity. It is demonstrated in this research work that, through electro-catalysis, appropriate cell design and good electrochemical engineering, efficiency and durability of the ambient temperature vestigated as part of a future integrated renewable energy system and compared with existing conventional temperature alkaline electrolyser system. The ambient temperature alkaline electrolyser is identified as a low-cost, reliable, and safe technology that is suitable for dynamic, intermittent, continuous and fast-response operation with renewable energy sources and the electrical grid. This also means the ambient temperature alkaline electrolyser is capable of wider operational range at 5%-100% of rated electrical power and faster response time in less than 1 second when powered by renewable energy sources. The auxiliary equipment are significantly reduced in the operation of ambient temperature alkaline electrolyser thereby reducing the cost of hydrogen and oxygen production and also making the technology reliable and safe for portable, stationary, transport and renewable energy system applications. alkaline electrolyser can be enhanced by about 13 % and 50 % respectively.
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Espiritu, Richard. "Polyethylene-based anion exchange membrane for alkaline fuel cell and electrolyser application : synthesis, characterisation and degradation studies". Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3702.
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Alkaline anion exchange membranes (AAEM) have been fabricated using polyethylene as the base polymer offering a low cost AAEM for electrolyser and fuel cell applications. This study focused on the synthesis and characterisation of AAEM with controlled degree of grafting (DOG) and ion-exchange capacity (IEC) with the following parameters investigated: low density polyethylene (LDPE) film thickness 30-130 μm, gamma radiation dose and monomer concentration. The corresponding IEC, water uptake (WU) and degree of swelling (DS) are reported. The performance of 74.6% DOG membrane in a hydrogen fuel cell showed a high open circuit voltage of 1.06 V, with a peak power density of 608 mW cm-2 at 50 °C under oxygen. The use of a membrane with a high DOG does not impact fuel cross-over significantly and provides improved fuel cell performance due to its high conductivity, water transport and resilience to dehydration. The AAEMs showed long term stability, at 80 °C, exhibiting a conductivity of ca. 0.11 S cm-1 over a period of 3300 h under nitrogen. The membrane showed a degradation rate of 5.7 and 24.3 mS kh-1 under nitrogen and oxygen, respectively. With the membrane lifetime defined as the duration of fuel cell operation until the conductivity of the membrane has reduced to a cut-off value of 0.02 S cm-1, the estimated lifetime of the membrane is 2 years under nitrogen and 5 months under oxygen operating at 80 °C. The fabricated anion exchange membranes were subjected to degradation tests in deionised water for electrolyser/fuel cell operation. After the degradation test, the decrease in ion exchange capacity (IEC) of the AEM, hence decrease in ionic conductivity, was influenced by the applied gamma radiation dose rate. The use of a high radiation dose rate produced membranes with improved stability in terms of % IEC loss due to shorter, more uniformly distributed vinylbenzyl chloride (VBC) grafts. For LDPE-based AEMs, increasing the applied radiation dose rate during grafting from 30 to 2000 Gy h-1 significantly reduced AEM % IEC loss from 38 to 11%, respectively. Analyses of both the aged functionalised membranes and their resulting degradation products confirmed the loss of not only the functional group, but also the VBC group, which has not been reported previously in the literature. Investigation of other amine functional groups revealed similar degradation via the removal of both VBC and head group. Oxidation reactions iii taking place at pH close to neutral are the main contributor to the IEC loss, in contrast to the widely reported E2 or SN2 attack on the head group in high alkalinity solutions. A parallel degradation mechanism is proposed to explain head group loss of AEMs, that involves peroxide radicals which are more dominant in low alkalinity solutions. The investigation of the degradation of a commercially available AEM (A201, Tokuyama Corp.) was performed and compared with the fabricated LDPE AEMs. Using similar membrane thickness, results revealed that the fabricated AEM exhibited superior stability to the commercial A201 membrane in terms of % IEC loss and ionic conductivity, both in fuel cell and electrolyser modes. It is believed that the faster degradation rate of the A201 membrane could possibly be due to the attack of OH- ions on both the head group and on the polymer backbone, the latter of which was not observed on the fabricated AEMs.
17
Boukarkour, Youness. "Étude de systèmes électro-catalytiques pour l’amélioration des performances de véhicules à moteurs thermiques". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0081.
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Aujourd’hui, la recherche de solutions énergétiques durables est devenue une préoccupation essentielle due à la crise environnementale que nous vivons, le secteur des transports étant parmi les domaines les plus polluants en raison de l’utilisation des moteurs à combustion interne (MCI). Bien que la transition vers des moteurs électriques est en cours, elle prendra du temps, car ces équipements ne seront pas accessibles à tous et présentent également leurs propres inconvénients. Les MCI vont donc rester d’actualité pendant longtemps malgré les politiques environnementales en cours. Logikko, l’entreprise avec qui nous avons travaillé, a eu l’idée d’accompagner la transition énergétique vers les moteurs électriques en injectant du H2 dans les MCI. Cette injection, même à de petites quantités, peut avoir un effet positif sur les émissions polluantes et sur le moteur lui-même en le gardant propre et efficace. Pour cela, il est nécessaire de produire localement l’hydrogène sous le capot du véhicule en mettant en oeuvre un électrolyseur alcalin qui peut être embarqué sous le capot. Dans ce contexte général, l’objectif de mon travail de thèse CIFRE a été centré sur l’amélioration des électrolyseurs développés par Logikko afin de les rendre plus résistants à la corrosion et aussi plus efficaces sur un plan énergétique. Le chapitre 1 décrit les notions nécessaires pour comprendre les mécanismes de la production de H2 par électrolyse alcaline et les processus qui les régissent. Nous discutons des conséquences de l’injection de ce gaz et du rôle qu’il peut jouer dans la réduction des polluants émis par le moteur. Dans le chapitre 2, nous étudions l’optimisation de l’électrolyte utilisé par l’entreprise, notamment peut réduire la corrosion. Différents matériaux d’électrodes ont été étudiés par voltammétrie cyclique ainsi que par chronoampérométrie. À l’issue de ce chapitre, nous avons proposé deux nouveaux matériaux d’électrodes prometteurs à l’entreprise. Dans le chapitre suivant, nous optimisons l’électrolyseur en changeant sa conception. Pour ce faire, nous avons approfondi le principe de l’électrochimie bipolaire pour identifier le rôle des plaques neutres et leur impact sur l’efficacité de l’électrolyseur. Comme résultat de cette étude, nous avons pu réduire encore plus les effets de la corrosion ainsi que les pertes énergétiques de l’électrolyseur. Poursuivant notre objectif, nous avons envisagé dans le chapitre 4 l’application d’un champ magnétique externe comme une innovation stratégique pour induire des effets magnétohydrodynamiques (MHD). Ils peuvent permettre d’augmenter l’efficacité énergétique de l’électrolyseur et la production d’hydrogène, en ouvrant la voie à des applications innovantes et économiquement viables. Enfin, le chapitre 5 décrit des travaux connexes que nous avons menés en parallèle. Ils concernent la détection du Cr(VI) dans l’électrolyte après un temps de fonctionnement ainsi que des méthodes analytiques utilisant l’électrochimie bipolaire pour analyser rapidement et efficacement le potentiel de matériaux d’électrodes alternatifs en vue de développements futursToday, the search for sustainable energy solutions has become a key concern due to the environmental crisis we are experiencing, with the transport sector among the most polluting areas due to the use of internal combustion engines (ICEs). While the transition to electric motors is underway, it will take time, as this equipment will not be accessible to everyone, and also has its own drawbacks. Therefore, despite current environmental policies, ICEs will still be around for a while. Logikko, the company we worked with, came up with the idea of supporting the energy transition by injecting H2 into ICEs. This injection, even in small quantities, can have a positive effect on pollutant emissions and on the engine itself, keeping it clean and efficient. To achieve this, it is necessary to produce hydrogen locally using an alkaline electrolyser that can be fitted under the hood of the vehicle. In this general context, the aim of my CIFRE thesis work was to improve the electrolysers developed by Logikko to make them more resistant to corrosion and also more energy efficient. Chapter 1 describes the concepts needed to understand the mechanisms of H2 production by alkaline electrolysis and the processes that govern them. We discuss the consequences of injecting this gas and the role it can play in reducing the pollutants emitted by the engine. In Chapter 2, we look at how the electrolyte used by the company can be optimised to reduce corrosion. Different electrode materials were studied using cyclic voltammetry and chronoamperometry. At the end of this chapter, we proposed two promising new electrode materials to the company. In the following chapter, we optimise the electrolyser by changing its design. To do this, we have delved into the principle of bipolar electrochemistry to identify the role of neutral plates and their impact on electrolyser efficiency. As a result of this study, we were able to further reduce the effects of corrosion and energy losses in the electrolyser. Pursuing our objective, in Chapter 4 we considered the application of an external magnetic field as a strategic innovation for inducing magnetohydrodynamic (MHD) effects. These can help increase electrolyser energy efficiency and hydrogen production, paving the way for innovative and economically viable applications. Finally, Chapter 5 describes related work we have been carrying out in parallel. These deal with the detection of Cr (VI) in the electrolyte after an operating time, as well as analytical methods using bipolar electrochemistry to rapidly and efficiently analyse the potential of alternative electrode materials for future developments
18
Zhang, Zhihao. "The Development of Three Dimensional Porous Nickel Materials and their Catalytic Performance towards Oxygen Evolution Reaction in Alkaline Media". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40636.
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As the global energy crisis and environmental pollution problem continues, there is an increasing demand for clean and sustainable energy storage and conversion technologies, such as water-splitting electrolysis. Water electrolysis is a process of running an electrical current through water in separating the hydrogen and oxygen. Oxygen evolution reaction (OER) is a key reaction in this electrochemical process, and the electrochemical performance of these systems is usually hindered by the slow OER reaction kinetics. In order to achieve high energy conversion efficiency, the development of efficient OER catalysts is the key. To achieve that, abundant research is done by using noble metal oxides as catalyst, such as IrO2 and RuO2. However, considering their high cost, a cheap earth-abundant material with a high OER catalytic activity is required. Accordingly, this study has been focused on the synthesis of three dimensional porous structured Ni-based OER catalysts. First, a 3D porous Ni meso-foam was developed through a facile high-temperature one-pot synthesis method, and its catalytic activity towards OER was explored. Specifically, the as-synthesized Ni meso-foam material, referred to as raw NMF, has a wire-linked structure and high surface area. A reduction procedure was introduced to obtain reduced Ni meso-foam materials, referred to as NMF-H2. It was also oxidized in air at 600 ℃ to form a semi-hollow NiO crosslinking phase and subsequently reduced in H2 at 300℃, forming a regenerated porous Ni foam material, referred to as NMF-O2/H2. The composition and morphology of all materials were investigated by XRD and SEM, respectively. The SEM image reveals that, in the porous NMF-O2/H2, the cross-linked meso-wire structure was maintained, and the average pore size is between 0.5-5 μm. Electrochemical analysis show that the OER activity of the Ni foam catalysts follows NMF-O2/H2 > NMF-H2 > raw NMF. In addition to the NMF-based materials, a Ni/Ni(OH)2 layer-structured electrocatalyst, referred to as NiDHBT, was also developed using a dynamic hydrogen bubble templating (DHBT) method. First, the 3D-porous micro Ni/Zn nanoplatelets were constructed in a two-step DHBT deposition method. The Ni/Zn foil was used as a scaffold, featured with the open porous structure and high surface area, for the subsequent electrodeposition of Ni(OH)2. Then, the Zn was etched from the as-prepared Ni/Zn/Ni(OH)2 nanocomposite to obtain the NiDHBT. The catalytic performance of the NiDHBT toward OER reaction was evaluated, and the optimal catalysts developed from different electro deposition potentials were determined. On the recognition of the high catalytic activity of NMF-O2/H2 and NiDHBT, porous structured FeOx-Nickel meso-foam, referred to as Fe@NMF-O2/H2, and FeOx- Ni/Ni(OH)2 layered-structure materials, referred to as Fe@NiDHBT, was further developed to explore the benefits of FeOx deposition for its OER catalytic performance. The deposition of FeOx is achieved by physical mixing FeOx colloid with NMF-O2/H2 and NiDHBT, and the electrochemical performance of these materials was examined in 1 M KOH. Among the developed materials, the best performing catalyst is Fe@NiDHBT synthesized by loading FeOx colloid onto the NiDHBT support. The overpotential for Fe@NiDHBT to reach 10 mA·cm-2 is 247mV, and the corresponding Tafel slope is 48.10mV·dec-1. Therefore, it was concluded that the FeOx¬¬ loading modification is an effective strategy to improve the OER activity of Ni foam-based catalysts.
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Haug, Philipp [Verfasser], e Thomas [Akademischer Betreuer] Turek. "Experimental and theoretical investigation of gas purity in alkaline water electrolysis / Philipp Haug ; Betreuer: Thomas Turek". Clausthal-Zellerfeld : Technische Universität Clausthal, 2019. http://d-nb.info/1231363312/34.
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Watkins, 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.
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Hydrogen is seen as the ‘energy carrier of the future’ due to the element’s relative abundance, the formation of water as opposed to the green house gases when utilised as a fuel in fuel cells, and the ability to be produced by electrolysers powered from renewable energy sources such as wind, water and sunlight. The development of hydrogen production through electrolysis is hindered by the high costs associated with the technology, specifically the ion exchange membranes and electrocatalysts that are employed in the membrane electrode assemblies used in polymer electrolyte electrolysers. This research focused on the development of non-noble catalysts suitable for hydrogen and oxygen evolution in alkaline electrolysis. Synthesis of NiO was achieved through thermal decomposition, chemical bath deposition and solution growth techniques. A mixed metal oxide, NiCo2O4, was synthesized through thermal decomposition of metal nitrate salts. Cyclic voltammetry and steady state electrochemical experiments on the electrodes were conducted in an electrochemical half cell electrolyser. A thin film of pure NiO was formed onto a titanium substrate through chemical bath deposition followed by thermal decomposition. The performance of the electrode at 1.73 V, relative to the mass of the catalyst loading, produced 0.25 A cm-2 mg-1 in 1 M NaOH at 25°C (IrO2 produced 0.44 A cm-2 mg-1 in the same electrolyser). The electrode’s performance is attributed to the nanoporous structure of the catalyst film (20 – 200 nm pore diameters), which was formed from the chemical bath deposition method used to prepare the catalyst films. Unfortunately this procedure has a limited film thicknesses so higher loadings could not be achieved. Higher loadings of other non-noble electrocatalysts were made possible with addition of a PVDF binder to the catalyst film. Physical analysis through XRD was performed on the most promising catalysts for the oxygen evolution reaction to confirm their composition. A blend of α-Ni(OH)2 and 4Ni(OH)2•NiOOH•xH2O formed through the chemical bath deposition technique produced higher current densities (104 mA cm-2 at 0.8 V vs. Hg/HgO) than another non-noble metal catalyst, NiCo2O4 (97 mA cm-2) II in 1 M NaOH at 25°C. An alkaline polymer electrolyser free from noble metals was developed with a membrane electrode assembly that utilised a partially fluorinated membrane, a PVBC/PVC ionomer in the catalyst layers, 1.0 mg NiMoO4 cm-2 in the cathode and 0.7 mg NiCo2O4 cm-2 in the anode. It produced 0.4 A cm-2 in 1 M KOH at 25° at a potential of 1.9 V.
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Palaniappan, Ramasamy. "Improving The Efficiency Of Ammonia Electrolysis For Hydrogen Production". Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1386341476.
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Jiang, Tao. "Development of Alkaline Electrolyzer Electrodes and Their Characterization in Overall Water Splitting". Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCA006.
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La décomposition électrolytique de l’eau en hydrogène et oxygène à l’aide d’électricité renouvelable générée par les courants marins ou à partir d’énergie éolienne ou solaire, constitue l’une des voies les plus propres et directes pour produire de l’hydrogène. Toutefois, la production de grands volumes d’hydrogène par décomposition électrolytique de l’eau comporte un verrou technologique qui réside dans la forte surtension à vaincre à l’anode où de l’oxygène est dégagé. Ce travail de thèse s’est attaché donc à mettre au point des matériaux d’électrodes capables de catalyser de l’eau en oxygène de façon efficace et stable, en utilisant des éléments chimiques suffisamment abondants sur terre. Pour cela nous avons exploré des composés présentant des porosités à structures hiérarchiques et des procédés de préparation efficaces, aisées à mettre en œuvre et susceptibles d’un usage à l’échelle industrielle. Nous avons développé deux types d’électrocatalyseurs d’oxydation de l’eau en oxygène en mettant au point deux voies de préparation impliquant chacune une phase d’activation in situ. Le premier type est une mousse de nickel dopée à la fois avec des cristaux de nickel, des nanoparticules de tétroxyde de tricobalt et des nanofeuilles d’oxyde de graphène via nickelage électrolytique, suivi d’une activation électrochimique in situ pour former de l’hydroxyde de nickel et des nano-plaques d’oxy-hydroxyde du même métal. Ce catalyseur hybride s’est avéré avoir des performances électrocatalytiques de bon niveau, comparables à celles des électrodes à base de métaux nobles qui sont disponibles dans l’état actuel de la technique ; il a en outre fait preuve d’une excellente stabilité en fonctionnement. Ces propriétés remarquables semblent liées à la fois aux dépôts formés sur la mousse de nickel par les différentes phases actives citées, aux nanoparticules d’oxy-hydroxyde de nickel, ainsi qu’aux effets de synergie qu’elles y induisent. Le second type d’électrocatalyseurs a été obtenu en combinant la projection thermique (HVOF) et un processus d’activation chimique puis électrochimique. Le matériau résultant possède de nanocouches du type jamborite formée in situ, sur la matrice poreuse à structure hiérarchique. Le catalyseur développé dans ce travail présente non seulement une surtension et une pente de Tafel exceptionnellement faibles, mais également une stabilité remarquable. Ces performances sont dues à un puissant effet de synergie dans laquelle interviennent la grande activité intrinsèque des nanofeuilles de jamborite et la grande rapidité des transports d’électrons et d’ions assurée par l'architecture poreuse hiérarchique. Il convient de noter que cette nouvelle méthodologie a le potentiel de produire des électrodes de grandes tailles apte à l’électrolyse alcaline de l'eau et crée ainsi de nouvelles perspectives dans le cadre de la conception d'électrocatalyseurs à la fois très actifs et stables. Nous avons également développé, initialement, des électrocatalyseurs destinés à la réduction de l’eau en hydrogène, qui impliquent également une activation électrochimique in situ. Ces électrodes peuvent être ainsi couplées aux électrodes précitées d’oxydation de l’eau en oxygène pour former des cellules électrochimiques complètes à deux électrodes, dont les performances rivalisent avec celles développées par le couple dioxyde de ruthénium/platine qui représente le meilleur état de la technique dans le cadre de la production d’hydrogène et d’oxygène par électrolyse de l’eau. En résumé, en combinant des techniques conventionnelles de revêtement et d’activation électrochimique in situ, ce travail a permis de développer une méthodologie de préparation d'électrodes catalytiques offrant de hautes performances et susceptibles de commercialisation. La technique d’activation électrochimique in situ exploite un comportement d'auto-optimisation dynamique qui est aisé à mettre en œuvre, facilement adaptable, efficace et respectueux de l'environnementSplitting water into hydrogen and oxygen by electrolysis using electricity from intermittent ocean current, wind, or solar energies is one of the easiest and cleanest routes for high-purity hydrogen production and an effective way to store the excess electrical power without leaving any carbon footprints. The key dilemma for efficient large-scale production of hydrogen by splitting of water via the hydrogen and oxygen evolution reactions is the high overpotential required, especially for the oxygen evolution reaction. Hence, engineering highly active and stable earth-abundant oxygen evolution electrocatalysts with three-dimensional hierarchical porous architecture via facile, effective and commercial means is the main objective of the present PhD study. Finally, we developed two kinds of good performance oxygen evolution electrocatalysts through two different way combined with in situ electrochemical activation.For the first oxygen evolution electrocatalyst, we report a codoped nickel foam by nickel crystals, tricobalt tetroxide nanoparticles, graphene oxide nanosheets, and in situ generated nickel hydroxide and nickel oxyhydroxide nanoflakes via facile electrolytic codeposition in combination with in situ electrochemical activation as a promising electrocatalyst for oxygen evolution reaction. Notably, this hybrid catalyst shows good electrocatalytic performance, which is comparable to the state-of-the-art noble catalysts. The hybrid catalyst as an electrocatalytically-active and robust oxygen evolution electrocatalyst also exhibits strong long-term electrochemical durability. Such a remarkable performance can be benefiting from the introduced active materials deposited on nickel foam, in situ generated nickel oxyhydroxide nanoflakes and their synergistic effects. It could potentially be implemented in large-scale water electrolysis systems.For the second oxygen evolution electrocatalyst, a facile and efficient means of combining high-velocity oxy-fuel spraying followed by chemical activation, and in situ electrochemical activation based on oxygen evolution reaction has been developed to obtain a promising self-supported oxygen evolution electrocatalyst with lattice-distorted Jamborite nanosheets in situ generated on the three-dimensional hierarchical porous framework. The catalyst developed in this work exhibits not only exceptionally low overpotential and Tafel slope, but also remarkable stability. Such a remarkable feature of this catalyst lies in the synergistic effect of the high intrinsic activity arising from the lattice-dislocated Jamborite nanosheets as the highly active substance, and the accelerated electron/ion transport associated with the hierarchical porous architecture. Notably, this novel methodology has the potential to produce large-size-electrode for alkaline water electrolyzer, which can provide new dimensions in design of highly active and stable self-supported electrocatalysts.Furthermore, we have also initially developed good hydrogen evolution electrocatalysts upon in situ electrochemical activation, coupled with the obtained superior oxygen evolution electrocatalysts forming two-electrode configurations, respectively, both of which rivalled the integrated state-of-the-art ruthenium dioxide-platinum electrode in alkaline overall water splitting.In summary, a methodology of fabricating easy-to-commercial, high performance catalytic electrodes by combining general coating processes with in situ electrochemical activation has been realized and well developed. The in situ electrochemical activation mentioned above is a dynamic self-optimization behavior which is facile, flexible, effective and eco-friendly, as a strategy of fabricating self-supported electrodes for efficient and durable overall water splitting. We hope our work can promote advanced development toward large-scale hydrogen production using excess electrical power whenever and wherever available
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SIRACUSANO, 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.
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Gli argomenti di questa tesi hanno riguardato l’elettrolisi cloro-soda e l’elettrolisi dell’acqua mediante sistemi basati su membrane a scambio protonico (PEM).
• Elettrolisi cloro-soda.
Il cloro è oggi essenzialmente ottenuto mediante i processi industriali di elettrolisi di cloro-soda ed, in minore quantità, dall’elettrolisi dell’acido cloridrico. Il principale problema di questi processi è l’elevato consumo di energia elettrica che, solitamente, rappresenta una parte sostanziale del costo totale di produzione. Per l’ottimizzare di tale processo è necessario, quindi, ridurre il consumo energetico. La sostituzione del tradizionale catodo ad evoluzione di idrogeno, con un elettrodo a diffusione gassosa ad ossigeno, comporta una nuova reazione che riduce il potenziale termodinamico di cella e questo si traduce in un risparmio energetico del 30-40%.
L’attività di ricerca è stata indirizzata verso lo studio di elettrodi a diffusione gassosa per la reazione di riduzione di ossigeno con particolare attenzione all’analisi superficiale e morfologica degli elettrocatalizzatori. In particolare l’attenzione è stata focalizzata sui fenomeni di deattivazione che coinvolgono questo tipo di elettrodi. Test di durata sono stati condotti sugli elettrodi in cella cloro-soda. Analisi di tipo comparativo sugli stessi sono state condotte, prima e dopo il loro funzionamento, nelle condizioni operative di interesse. La superficie degli elettrodi è stata analizzata mediante microscopio elettronico a scansione e spettroscopia fotoelettronica a raggi X. Analisi di bulk sono state effettuate mediante diffrattometria a raggi X ed analisi termogravimetrica.
• Elettrolisi dell’acqua (PEM).
L’idrogeno può essere prodotto a partire da sorgenti energetiche rinnovabili come fotovoltaico, eolico mediante l’elettrolisi dell’acqua. In particolare, l’elettrolisi, mediante l’utilizzo di un elettrolita polimerico (PEM), è considerata una promettente metodologia per la produzione di idrogeno, alternativa al convenzionale processo di elettrolisi il cui elettrolita è un liquido alcalino, altamente tossico e corrosivo. Un elettrolizzatore PEM possiede certamente dei vantaggi confrontato con il classico processo alcalino in termini di semplicità, sicurezza ed alta efficienza energetica. Questo sistema utilizza la già affermata tecnologia delle celle a combustibile ad elettrolita polimerico. Sfortunatamente il processo di scissione elettrochimica dell’acqua è associata ad un elevato consumo energetico, principalmente dovuto agli alti sovrapotenziali nella reazione anodica di evoluzione di ossigeno. Risulta quindi di fondamentale importanza trovare elettrocatalizzatori per l’evoluzione di ossigeno ottimali in modo da minimizzare le perdite.
Il platino è utilizzato al catodo per la reazione di evoluzione di idrogeno (HER) e gli ossidi di iridio o rutenio sono usati all’anodo per la reazione di evoluzione di ossigeno (OER). Questi ossidi metallici sono richiesti perché, confrontati al platino metallico, offrono alta attività catalitica, una migliore stabilità a lungo termine ed una minore perdita di efficienza dovuta alla corrosione o all’inquinamento.
Il lavoro è stato principalmente indirizzato verso: 1) la sintesi e caratterizzazione di anodi a base di RuO2 e IrO2; 2) la sintesi di supporti conduttori a base di subossidi di titanio con alta area superficiale.
1) Catalizzatori nanostrutturati a base di RuO2 e IrO2 sono stati preparati mediante un processo colloidale a 100°C; gli idrossidi così ottenuti sono stati calcinati a differenti temperature. L’attenzione è stata focalizzata sugli effetti che il trattamento termico produce sulla struttura cristallografica e sulla dimensione delle particelle di questi catalizzatori e come queste proprietà possono influenzare le performance degli elettrodi per la reazione di evoluzione di ossigeno. Caratterizzazioni elettrochimiche sono state fatte mediante curve di polarizzazioni, spettroscopia d’impedenza, e misure di crono-amperometria.
2) Una nuova metodologia di sintesi per la preparazione dei subossidi di titanio con fase Magneli (TinO2n-1) è stata sviluppata. Le caratteristiche di questi materiali sono state valutate sotto condizioni operative, in elettrolizzatori di tipo SPE, e confrontate con la polvere commerciale Ebonex. La stessa fase attiva a base di IrO2 è stata usata, come elettrocatalizzatore, per entrambi i sistemi.The 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.
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Fan, Kaicai. "Development of High Performance Electrocatalyst for Water Splitting Application". Thesis, Griffith University, 2018. http://hdl.handle.net/10072/382229.
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With increasing global demand for energy, rapid depletion of fossil fuels and intensification of environmental concerns, exploring clean and sustainable energy carriers to replace fossil fuel is becoming critical. Among the various alternatives, hydrogen has been intensively regarded as a promising energy carrier to fulfill the increasing energy demand due to its large energy density per unit mass and eco-friendly production possibilities. However, hydrogen does not exist in molecular structure in nature, and it is essential to obtain efficient and sustainable H2 production technologies. Alkaline water electrolysis is an effective, clean and sustainable process to produce high-quality hydrogen. In this process, highly active electrocatalysts for the hydrogen evolution reaction (HER) are required to accelerate the sluggish kinetics and lower the overpotentials (η) for efficient hydrogen evolution. To date, a noble metal, platinum (Pt), is the state-of-art electrocatalyst for HER. However, exploration of alternative electrocatalysts with low cost and excellent electrocatalytic activity is of vital importance to realize large-scale hydrogen production through water electrolysis. Generally, an electrochemically active catalyst should have an optimal hydrogen adsorption free energy to allow efficient catalytic hydrogen adsorption/desorption. In alkaline solution, dissociation of water onto the electrocatalyst determines the overall HER efficiency.
This thesis focuses on rational design and synthesis of different earth-abundant electrocatalysts for electrocatalytic HER in alkaline media. Through facile anion or cation doping strategies, electrocatalysts with abundant accessible active sites, enhanced electronic conductivity and accelerated HER kinetics have been systematically fabricated, characterized and evaluated.
First, an efficient HER electrocatalyst in alkaline media was fabricated by incorporating sulfur atoms into a cobalt (hydro)oxide crystal structure. The resultant catalyst exhibits a remarkably enhanced HER activity with a low-overpotential of 119 mV at 10 mA/cm2 and an excellent durability. The results suggest that cobalt hydroxide benefits water adsorption and cleavage, while the negatively charged sulfur ligands facilitate hydrogen adsorption and desorption on the surface of electrocatalysts, leading to significantly promoted Volmer and Heyrovsky steps for HER in alkaline media.
Second, exploring bifunctional electrocatalysts which can simultaneously accelerate the HER and oxygen evolution reaction (OER) activities plays a key role in alkaline water splitting. Here, sulfur atoms were incorporated into the mixed transition metal hydroxide with high OER performance to render excellent HER activity. The enhanced catalytic activity towards HER was confirmed by a synergistic effect between the retained metal hydroxide host and the incorporated sulfur atoms. In addition, the full water splitting electrolyzer equipped with fabricated bifunctional electrocatalysts as anode and cathode materials exhibited remarkable overall water splitting performance comparable to that with benchmark Pt and RuO2 electrocatalysts.
The S/Se co-doped Co3O4 nanosheets on carbon cloth were fabricated by a facile room temperature chalcogen atom incorporation methodology and were applied as the electrocatalyst for HER in alkaline media. The sulfur and selenium atoms were homogeneously distributed on the surface by forming Co-S or Co-Se bonds which play a key role in the structural change in electrochemical activation. The obtained electrocatalysts demonstrated remarkably improved HER activity compared to that of the original Co3O4.
Finally, molybdenum doped cobalt hydroxide was fabricated with significantly accelerated HER kinetics. The introduced Mo sites not only effectively facilitate water dissociation process and desorption of the OHads intermediates, but also simultaneously optimize the hydrogen adsorption free energy. Therefore, the in situ-generated Mo-doped amorphous cobalt hydroxide exhibited a remarkable HER performance in alkaline media with an overpotential of only -80 mV at a current density of 10 mA/cm2.
This thesis innovatively explores strategies to improve the catalytic activity towards HER of metal (hydro)oxide in alkaline media. The surface foreign atom doping was demonstrated to manipulate the surface structure of catalysts, thus not only improving the water dissociation processes, but also facilitating the hydrogen adsorption/desorption on the catalysts. The demonstrated facile and effective strategies could be adopted for the fabrication of cost-effective and highly active catalysts for other important chemical reactions for energy conversion applications.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Bick, Daniel S. [Verfasser], Manfred [Akademischer Betreuer] Martin e Rainer [Akademischer Betreuer] Waser. "Performance and degradation of BaCoO$_3}$ based Perovskite catalysts during oxygen evolution in alkaline water electrolysis / Daniel Sebastian Bick ; Manfred Martin, Rainer Waser". Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1210862654/34.
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Sundin, Camilla. "Environmental Assessment of Electrolyzers for Hydrogen Gas Production". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-260069.
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Hydrogen has the potential to become an important energy carrier in the future with many areas of applications, as a clean fuel for transportation, heating, power generation in places where electricity use is not fit, etc. Already today hydrogen plays a key role in numerous industries such as petroleum refineries and chemical industries. There are different production methods for hydrogen. Today, natural gas reforming is the most commonly used. With the growing importance of green production paths, hydrogen production by electrolysis is expected to grow. Two main electrolyzer technologies are used today; alkaline and polymer electrolyte membrane electrolyzer. High-temperature electrolyzers are also interesting techniques, where solid oxide is under development and molten carbonate electrolyzers is researched. In this thesis, a comparative life cycle analysis was performed on the alkaline and molten carbonate electrolyzer. Due to inaccurate inventory data for the molten carbonate electrolyzer, those results are excluded from the published thesis. The environmental performance of the alkaline electrolyzer technology was compared to that of the solid oxide and the polymer electrolyte membrane electrolyzers. The system boundaries were set as cradle to gate. Thereby, the life cycle steps included in the study are raw material extraction, electrolyzer manufacturing, hydrogen production, and transports in between these steps. The functional unit was chosen as 100 kg produced hydrogen gas. The results show that the polymer electrolyte membrane electrolyzer has the lowest environmental impact out of the compared technologies. It is also determined that the lifetime and the current density of the electrolyzers have significant impact on their environmental performance. Moreover, it is established that electricity for hydrogen production has the highest environmental impact out of the electrolyzers life cycle steps. Therefore, it is important to make sure that the electricity used for hydrogen production derives from renewable sources.Vätgas har potential att spela en viktig roll som energibärare i framtiden med många användningsområden, såsom ett rent bränsle för transporter, uppvärmning, kraftförsörjning där elproduktion inte är lämpligt, med mera. Redan idag är vätgas ett viktigt inslag i flera industrier, där ibland raffinaderier och kemiska industrier. Det finns flera metoder för att producera vätgas, där reformering av naturgas är den största produktionsmetoden idag. I framtiden spås vätgasproduktion med elektrolys bli allt viktigare, då hållbara produktionsprocesser prioriteras allt mer. Idag används främst två elektrolysörtekniker, alkalisk och polymerelektrolyt. Utöver dessa är högtemperaturelektrolysörer också intressanta tekniker, där fastoxidelektrolysören är under utveckling och smältkarbonatelektrolysören är på forskningsstadium. I det här examensarbetet har en jämförande livscykelanalys utförts på alkalisk- och smältkarbonatelektrolysören. På grund av felaktiga indata för smältkarbonatelektrolysören har dessa resultat uteslutits från den publika rapporten. Miljöpåverkan från den alkaliska elektrolysören har sedan jämförts med miljöpåverkan från fastoxid- och polymerelektrolytelektrolysörerna. Systemgränserna sattes till vagga till grind. De livscykelsteg som inkluderats i studien är därmed råmaterialutvinning, elektrolysörtillverkning, vätgasproduktion och transporter mellan dessa steg. Den funktionella enheten valdes till 100 kg producerad vätgas. Resultaten visar att polymerelektrolytteknologin har den lägsta miljöpåverkan utav de tekniker som jämförts. Resultaten påvisar också att livstiden och strömtätheten för de olika teknikerna har signifikant påverkan på teknikernas miljöpåverkan. Dessutom fastslås att elektriciteten för vätgasproduktion har högst miljöpåverkan utav de studerade livscykelstegen. Därför är det viktigt att elektriciteten som används för vätgasproduktionen kommer ifrån förnybara källor.
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Byrne, Philip. "Mathematical modelling and experimental simulation of chlorate and chlor-alkali cells". Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3182.
Texto completo da fonte
28
Kunovjánek, Miroslav. "Studium vodivosti PVA membrán, obsahujících alkalické hydroxidy". Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-234580.
Texto completo da fonteResumo:
Thesis deals with study of separators and membranes, suitable for using in alkali electrochemical applications like fuel cells or electrolysis. As basic material for membranes production is used polyvinylalkohol (PVA). Various methods of PVA cross linking are introduced in the thesis. PVA membranes are also doped by various types of additives to improve the attributes of the membranes like mechanical stability and or conductivity. The aim of the work is verification of parameters of membranes, doped by alkali hydroxides KOH, NaOH and LiOH at various temperatures. These hydroxides are added to the membrane especially for increasing of membrane conductivity.
29
Rodene, Dylan D. "Engineering of Earth-Abundant Electrochemical Catalysts". VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6106.
Texto completo da fonteResumo:
Alternative energy research into hydrogen production via water electrolysis addresses environmental and sustainability concerns associated with fossil fuel use. Renewable-powered electrolyzers are foreseen to produce hydrogen if energy and cost requirements are achieved. Electrocatalysts reduce the energy requirements of operating electrolyzers by lowering the reaction kinetics at the electrodes. Platinum group metals (PGMs) tend to be utilized as electrocatalysts but are not readily available and are expensive. Ni1-xMox alloys, as low-cost and earth-abundant transition metal nanoparticles (NPs), are emerging as promising electrocatalyst candidates to replace expensive PGM catalysts in alkaline media. Pure-phase cubic and hexagonal Ni1-xMox alloy NPs with increasing Mo content (0–11.4%) were synthesized as electrocatalysts for the hydrogen evolution reaction (HER). In general, an increase in HER activity was observed with increasing Mo content. The cubic alloys were found to exhibit significantly higher HER activity in comparison to the hexagonal alloys, attributed to the higher Mo content in the cubic alloys. However, the compositions with similar Mo content still favored the cubic phase for higher activity. To produce a current density of -10 mA/cm2, the cubic and hexagonal alloy NPs require over-potentials ranging from -62 to -177 mV and -162 to -242 mV, respectively. The cubic alloys exhibited over-potentials that rival commercial Pt-based electrocatalysts (-68 to -129 mV at -10 mA/cm2). The cubic Ni0.934Mo0.066 alloy NPs showed the highest alkaline HER activity of the electrocatalysts studied and therefore a patent application was submitted.
Bulk Ni–Mo phases have been known as electrocatalysts for the HER for decades, while recently transition metal phosphides (TMPs) have emerged as stable and efficient PGM alternatives. Specifically, Ni2P has demonstrated good HER activity and improved stability for both alkaline and acidic media. However, Ni2P electrocatalysts are a compromise between earth-abundance, performance (lower than Ni–Mo and PGMs) and stability. For the first time Ni–Mo–P electrocatalysts were synthesized with varying atomic ratios of Mo as electrocatalysts for alkaline HER. Specific phases, compositions and morphologies were studied to understand the intrinsic properties of TMPs leading to high HER activity. The Ni1.87Mo0.13P and Ni10.83Mo1.17P5 NPs were shown to be stable for 10 h at –10 mA cm-2 with over-potentials of –96 and –82 mV in alkaline media, respectively. The Ni1.87Mo0.13P and Ni10.83Mo1.17P5 NPs exhibited an improved performance over the synthesized Ni2P sample (–126 mV at –10 mA cm-2), likely a result of the overall phosphorous content and hetero-structured morphologies. A strong correlation between phase dependence and the influence of Mo on HER activity needs to be further investigated.
Furthermore, understanding the intrinsic properties of electrocatalysts leading to high water splitting performance and stability can apply electrocatalysts in other research applications, such as photoelectrochemical (PEC) water splitting, water remediation and sustainable chemical processing applications. Contributions to photocatalytic water remediation and electrochemical chlorinated generation to halogenate pyridone-based molecules are reported. Electrochemical techniques were developed and reported herein to aid in understanding electrochemical performance, chemical mechanisms and the stability of electrocatalysts at the electrode-electrolyte interfaces.
30
Feynerol, Vincent. "Traitement de minerais de fer par lixiviation alcaline suivi de leur électrolyse en milieu alcalin". Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0163.
Texto completo da fonteResumo:
Un procédé innovant de production de fer par électrolyse d’une suspension d’oxydes de fer en milieu alcalin concentré est développé au centre de recherche d’ArcelorMittal de Maizières-lès-Metz. Ce procédé s’il atteignait la maturité industrielle permettrait de réduire significativement les émissions de dioxyde de carbone associées à l’industrie sidérurgique, en remplaçant le carbone utilisé comme agent réducteur dans les hauts-fourneaux par de l’électricité. Bien que ce procédé permette la production de fer à partir d’hématite commerciale (Fe2O3) à une densité de courant de l’ordre de 1000 A.m-2 avec une efficacité faradique supérieure à 80%, une dégradation des performances est systématiquement constatée lors de l’électrolyse de minerais de fer. Les impuretés majoritaires de ces minerais sont les oxydes et hydroxydes d’aluminium et de silicium, des composés solubles dans la soude concentrée. Ces composés pourraient donc être à l’origine de la baisse de réactivité observée lors de l’alimentation du procédé par des minerais de fer. Ainsi afin de tenter d’améliorer les performances de l’électrolyse alcaline à partir de minerais, des traitements de lixiviation alcaline sur un minerai défini ont été effectués dans cette thèse. La réactivité des minerais avant et après traitement a été comparée par chronoampérométrie. Bien que suite à l’élimination de ses composés alumineux, le minerai traité ait vu son rendement faradique réhaussé à environ 80% pour une valeur avant pré-traitement de 65%, sa densité de courant est restée deux fois moins élevée que celle de l’hématite pour une même tension électrique appliquée. Des expériences d’ajout d’ions aluminates et d’ions silicates lors de l’électrolyse d’hématite pure n’ont de plus eu pratiquement aucun effet indésirable sur son électrolyse. Les diverses expériences conduites dans cette thèse laissent supposer que les impuretés traitées n’ont que peu d’influence sur la réactivité des minerais. Le procédé est en revanche très sensible à la granulométrie des particules de minerais. Par ailleurs de forts phénomènes d’agglomération, qui n’ont pas lieu avec les oxydes de fer purs, ont été constatés lors de mesure de granulométrie du minerai étudié. Ainsi les expériences réalisées laissent supposer qu’un autre phénomène, probablement lié à la granulométrie secondaire des minerais en milieu alcalin concentré, soit à l’origine de la baisse de réactivité observée lors de leur électrolyse. Parallèlement une analyse thermodynamique avancée a été menée afin de déterminer les meilleures conditions théoriques de pression, de température et de concentration en NaOH pour effectuer l’électrolyse de l’hématite. La solubilité des composés de la gangue a été représentée avec des équations de Pitzer, et de nouveaux paramètres ont été calculés pour les interactions Na-SiO3-Al(OH)4. Cette étude thermodynamique a permis la conception et le pré-dimensionnement d’une étape de traitement des minerais par lixiviation alcalineAn innovative ironmaking process by alkaline electrolysis of suspended iron oxides is being developed at ArcelorMittal Global R&D Maizières-lès-Metz. Were it to achieve industrial maturity, this process would permit a significant reduction of steelmaking CO2 emissions. Indeed, the use of carbon as a reducing agent in blast furnace would be replaced by electricity. Although this process enables iron production from commercial hematite (Fe2O3) at current density of 1000 A.m-2 with faradaic efficiency higher than 80%, these performances are systematically lower when using iron ore instead. The main impurities in these ores are aluminium and silicon oxides and hydroxides, these compounds are soluble in concentrated sodium hydroxide solutions. These compounds could be the source of the decrease in reactivity observed when feeding the process with iron ores. To raise the electrolysis performance with iron ores, alkaline leaching treatments were conducted on a defined iron ore. Reactivity of iron ores before and after treatment was compared by chronoamperometry. Although the elimination of aluminous compounds resulted in the ore gaining a faradaic yield increase to a value of 80%, compared with 65% before treatment, its current density remained twice as low as the one of hematite for a same applied voltage. Furthermore, complementary experiments of aluminate and silicate ions addition during pure hematite electrolysis did not have any deleterious effect on its electrolysis. Based on all the experiments undertaken in this PhD, it seems unlikely that siliceous and aluminous impurities hold an important effect on iron ore reactivity in alkaline electrolysis. The process is nonetheless very sensitive to iron ores granulometry. On this subject, strong agglomeration phenomena were witnessed when measuring iron ores granulometry but did not occur with pure iron oxides. Therefore, it would seem that other phenomena may be the main cause of reactivity loss, these phenomena may well be linked to secondary granulometry of iron ores in concentrated alkaline media. In parallel, an advanced thermodynamic analysis was carried out to describe the best theoretical conditions for pressure, temperature and NaOH concentration to realize hematite electrolysis. Gangue compounds solubility was represented with Pitzer equations, and new parameters were calculated for Na-SiO3-Al(OH)4 interactions. This thermodynamic study enabled the design and pre-sizing of a treatment step for iron ores by alkaline leaching
31
Feynerol, Vincent. "Traitement de minerais de fer par lixiviation alcaline suivi de leur électrolyse en milieu alcalin". Electronic Thesis or Diss., Université de Lorraine, 2018. http://www.theses.fr/2018LORR0163.
Texto completo da fonteResumo:
Un procédé innovant de production de fer par électrolyse d’une suspension d’oxydes de fer en milieu alcalin concentré est développé au centre de recherche d’ArcelorMittal de Maizières-lès-Metz. Ce procédé s’il atteignait la maturité industrielle permettrait de réduire significativement les émissions de dioxyde de carbone associées à l’industrie sidérurgique, en remplaçant le carbone utilisé comme agent réducteur dans les hauts-fourneaux par de l’électricité. Bien que ce procédé permette la production de fer à partir d’hématite commerciale (Fe2O3) à une densité de courant de l’ordre de 1000 A.m-2 avec une efficacité faradique supérieure à 80%, une dégradation des performances est systématiquement constatée lors de l’électrolyse de minerais de fer. Les impuretés majoritaires de ces minerais sont les oxydes et hydroxydes d’aluminium et de silicium, des composés solubles dans la soude concentrée. Ces composés pourraient donc être à l’origine de la baisse de réactivité observée lors de l’alimentation du procédé par des minerais de fer. Ainsi afin de tenter d’améliorer les performances de l’électrolyse alcaline à partir de minerais, des traitements de lixiviation alcaline sur un minerai défini ont été effectués dans cette thèse. La réactivité des minerais avant et après traitement a été comparée par chronoampérométrie. Bien que suite à l’élimination de ses composés alumineux, le minerai traité ait vu son rendement faradique réhaussé à environ 80% pour une valeur avant pré-traitement de 65%, sa densité de courant est restée deux fois moins élevée que celle de l’hématite pour une même tension électrique appliquée. Des expériences d’ajout d’ions aluminates et d’ions silicates lors de l’électrolyse d’hématite pure n’ont de plus eu pratiquement aucun effet indésirable sur son électrolyse. Les diverses expériences conduites dans cette thèse laissent supposer que les impuretés traitées n’ont que peu d’influence sur la réactivité des minerais. Le procédé est en revanche très sensible à la granulométrie des particules de minerais. Par ailleurs de forts phénomènes d’agglomération, qui n’ont pas lieu avec les oxydes de fer purs, ont été constatés lors de mesure de granulométrie du minerai étudié. Ainsi les expériences réalisées laissent supposer qu’un autre phénomène, probablement lié à la granulométrie secondaire des minerais en milieu alcalin concentré, soit à l’origine de la baisse de réactivité observée lors de leur électrolyse. Parallèlement une analyse thermodynamique avancée a été menée afin de déterminer les meilleures conditions théoriques de pression, de température et de concentration en NaOH pour effectuer l’électrolyse de l’hématite. La solubilité des composés de la gangue a été représentée avec des équations de Pitzer, et de nouveaux paramètres ont été calculés pour les interactions Na-SiO3-Al(OH)4. Cette étude thermodynamique a permis la conception et le pré-dimensionnement d’une étape de traitement des minerais par lixiviation alcalineAn innovative ironmaking process by alkaline electrolysis of suspended iron oxides is being developed at ArcelorMittal Global R&D Maizières-lès-Metz. Were it to achieve industrial maturity, this process would permit a significant reduction of steelmaking CO2 emissions. Indeed, the use of carbon as a reducing agent in blast furnace would be replaced by electricity. Although this process enables iron production from commercial hematite (Fe2O3) at current density of 1000 A.m-2 with faradaic efficiency higher than 80%, these performances are systematically lower when using iron ore instead. The main impurities in these ores are aluminium and silicon oxides and hydroxides, these compounds are soluble in concentrated sodium hydroxide solutions. These compounds could be the source of the decrease in reactivity observed when feeding the process with iron ores. To raise the electrolysis performance with iron ores, alkaline leaching treatments were conducted on a defined iron ore. Reactivity of iron ores before and after treatment was compared by chronoamperometry. Although the elimination of aluminous compounds resulted in the ore gaining a faradaic yield increase to a value of 80%, compared with 65% before treatment, its current density remained twice as low as the one of hematite for a same applied voltage. Furthermore, complementary experiments of aluminate and silicate ions addition during pure hematite electrolysis did not have any deleterious effect on its electrolysis. Based on all the experiments undertaken in this PhD, it seems unlikely that siliceous and aluminous impurities hold an important effect on iron ore reactivity in alkaline electrolysis. The process is nonetheless very sensitive to iron ores granulometry. On this subject, strong agglomeration phenomena were witnessed when measuring iron ores granulometry but did not occur with pure iron oxides. Therefore, it would seem that other phenomena may be the main cause of reactivity loss, these phenomena may well be linked to secondary granulometry of iron ores in concentrated alkaline media. In parallel, an advanced thermodynamic analysis was carried out to describe the best theoretical conditions for pressure, temperature and NaOH concentration to realize hematite electrolysis. Gangue compounds solubility was represented with Pitzer equations, and new parameters were calculated for Na-SiO3-Al(OH)4 interactions. This thermodynamic study enabled the design and pre-sizing of a treatment step for iron ores by alkaline leaching
32
Carnieletto, Renata. "Aproveitamento de energia vertida turbinável para produção de hudrogênio e geração distribuída". Universidade Federal de Santa Maria, 2011. http://repositorio.ufsm.br/handle/1/8486.
Texto completo da fonteResumo:
Conselho Nacional de Desenvolvimento Científico e TecnológicoIn many hydroelectric power plants, while the water inflows are greater than demand, part of this water that could be used to generate energy is spilled by the dam gates and literally wasted. This dissertation discusses the use of this wasted hydroelectric potential for hydrogen (H2) generation through water electrolysis. The usage of this hydrogen can happen not only in vehicle engines or industrial applications, but in energy generation through fuel cells and behaving as an energy vector. The H2 production by electrolysis requires an energy source for its processing. This dissertation aims at to mitigate this issue by the use of the secondary energy. Besides the H2 generation aspects, it is presented the complete mathematic model of alkaline electrolyzers. With respect to the wasted hydroelectric potential approach it must be taken into account that alternative sources of energy are settled onto three bases: the energy source itself, the distribution grid and the interconnection energy source-to-grid (or source-to-load). Looking at this fact, the source connection and disconnection from the grid is a challenge for systems engineering. For this dissertation the simulation of Voltage Source Inverters (VSI) was selected to represent the islanded and grid tied conditions. For that, it is proposed an anti-islanding algorithm used to protect the system against faults that may occur in the grid. A reconnection algorithm is also included to obtain the synchronism of the alternative source with the electric grid. To control these inverters, two control techniques are presented along this text: DQ-frame and the proportional and resonant (P+Resonant) control. These control techniques are simulated to evaluate the application efficiency of such controllers. Additionally a smart control in perspectives of the smart grid was also developed and it is proposed in this dissertation. A smart grid integrated to the distribution system allows aggregation of efficient actions of all agents related to electricity services and so strategically making available the electricity goods and services. In this context, based on real-time spot pricing of the electricity obtained from the utility using an advanced metering device, the inverter control algorithm determines the optimal operating mode. This algorithm enables the inverter to: a) schedule local loads; b) determine either to local storage or selling of energy to the grid. Finally, it is shown that on-line fault detection in the system can also make possible a fast restoration of most contingence situations.
Em muitas Usinas Hidrelétricas, quando as afluências de água são maiores que a demanda, uma parcela desta água que ainda poderia ser utilizada para gerar energia é desviada para o vertedouro e literalmente desperdiçada. Esta energia recebe a denominação de Energia Vertida Turbinável (EVT). Essa dissertação discute o aproveitamento da EVT para produção de hidrogênio através da eletrólise da água. O uso desse hidrogênio pode ocorrer não apenas em motores de veículos ou aplicações industriais, mas na própria geração de energia elétrica em células a combustível, agindo como vetor energético. A produção de H2 por eletrólise da água convencionalmente necessita de uma fonte de energia para o processo. Essa dissertação sugere a mitigação deste problema pela utilização de energia secundária. Além de aspectos para produção de H2, é apresentada uma modelagem matemática completa de todo este processo envolvendo os eletrolisadores alcalinos. Na abordagem da EVT há que se levar em conta que as fontes alternativas em geral estão assentadas em três fundamentos: a fonte de energia, a rede de distribuição e a interconexão fonte de energia-rede (ou fonte-carga). Com vistas a este fato, a desconexão e re-conexão entre a fonte e a rede pode ser um problema desafiador para a engenharia de sistemas. Para esta dissertação, selecionou-se a simulação dos Inversores VSI (Voltage Source Inverters) como resposta para as condições de ilhamento e conexão à rede elétrica. Para isto, propõe-se um algoritmo anti-ilhamento que visa a proteção contra as faltas que possam ocorrer na rede e um algoritmo de re-conexão à rede, incluindo o meio de sincronismo da fonte alternativa com a rede. Para controlar tais inversores, duas técnicas são apresentadas ao longo deste texto: utilizando as transformações DQ e controle proporcional e ressonante (P+Resonant). Essas duas técnicas de controle são simuladas para se avaliar a eficiência da aplicação de tais controladores. Em adicional, foi desenvolvido um controle inteligente diferenciado com perspectivas ao Smart Grid. O Smart Grid integrado aos sistemas de distribuição permite agregar de forma eficiente as ações de todos os agentes ligados a ele para que, de forma estratégica, sejam disponibilizados bens e serviços de eletricidade. Neste contexto, o controle inteligente proposto para inversores de conexão com rede a utiliza técnicas de gerenciamento pelo lado da demanda e ainda determina automaticamente o ponto ótimo de operação do inversor, possibilitando assim o planejamento e arranjo de cargas locais e a determinação de quando deve ser armazenada energia ou vendida para a rede. Mostra-se finalmente que a detecção das falhas no sistema também poderá ser praticada de forma a se poder atuar rapidamente no restabelecimento das situações de contingência.
33
Gillespie, Malcolm Ivor. "Evaluation of performance influencing parameters on alkaline water electrolysis systems". Thesis, 2016. http://hdl.handle.net/10539/20024.
Texto completo da fonteResumo:
Alkaline Water Electrolysis (AWE) has shown to be an effective method of producing
hydrogen from renewable sources of energy. However this process accounts for only 4-5% of
the global hydrogen production. Challenges abound for water electrolysis technologies that
presents the traditional methods as comparably favourable.
This research focuses on investigating the relevant performance influencing parameters for
alkaline water electrolysers, their contribution to compromising or enhancing cell
performance and the various interdependencies that exist between variables. Hydrox
Holdings Ltd., in partnership with Demcotech Engineering, provided permission to analyse
the performance of a membraneless alkaline water electrolysis pilot plant.
Using pure nickel for the anode and cathode electrodes yielded current densities of 51.9
mA.cm-2 (at 1.8VDC, 82% HHV efficiency) and 242.9mA.cm-2 (at 2 VDC, 73% HHV
efficiency) at an electrode gap of 2.5mm, temperature of 70°C and a flow velocity of
0.075m.s-1. At these same experimental conditions, employing Ir-RuO2 on a Ti substrate for
the anode and Pt on a Ti substrate for the hydrogen evolution reaction, current densities of
220 mA.cm-2 (at 1.765VDC) and 474 mA.cm-2 (at 2 VDC) was achieved.
Marini et al., (2012), notes that performance for conventional alkaline water electrolysers
should be in the order of > 100 mA.cm-2 when operating at a cell potential of 2 VDC. The
performance of the membraneless technology has therefore exceeded this benchmark by
more than 2 times with the use of basic nickel electrodes and being more than 4 times with
the use of PGM catalytic materials, and hence could be described to very comparable as
advanced methods of alkaline water electrolysis. The ability to obtain high current density
thresholds implies that the membrane less technology has potential for a substantial reduction
in scale and hence, in the total capital cost of the technology.
34
HSIEH, WEN-HAO, e 解文浩. "Fabrication of nanostructured electrodes via AAO templates for alkaline water electrolysis". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/84295272112523001373.
Texto completo da fonteResumo:
碩士南臺科技大學
光電工程系
104
In order to decrease the operating voltage and increase the efficiency of water electrolysis, we produced nanostructured materials as the electrodes. We electroplated nickel/platinum into the pores of anodic aluminum oxide (AAO) templates to form electrodes with high specific surface area which can increase the catalytic activity. The experimental procedures were as follows: using electron beam evaporator to deposit titanium film on glass substrate as the buffer layer, and nickel or gold strips on the buffer layer as the conducting layer; using thermal evaporator to deposit aluminum film on the conducting layer and then anodically oxidizing the aluminum film to form porous AAO; using chemical dissolution to remove barrier oxide to form barrier-free AAO template; using nickel aminosulfonate or hexachloroplatinic acid as the plating solution to electroplate nickel or platinum into the AAO pores. After removing the AAO, nickel nanopillar arrays or platinum nanopillar arrays were obtained. According to the experimental results, the quality of aluminum film influences the quality of AAO template significantly. After using two-step deposition, the surface property and crystallinity of aluminum film were highly improved. A high quality AAO template was successfully prepared. With this template, nickel nanopillar arrays or platinum nanopillar arrays with pillar diameter of 150~250 nm were electroplated, and the length of nanopillars could be adjusted by the plating time. The results of alkaline water electrolysis showed that the efficiency of hydrogen evolution and oxygen evolution were obviously increased by the nanopillar array electrodes. It also demonstrated that the platinum nanopillar electrode has higher catalytic activity than nickel nanopillar electrode in the process of cathodic hydrogen production, but lower catalytic activity in the process of anodic oxygen production. By analyzing the electrochemical characteristics of electrodes, we found that the thickness of conducting layer under the nanopillars affects the performance of water electrolysis. By increasing the thickness of conducting layer, the efficiency of water electrolysis using nanopillar-array electrodes can be further improved.
35
Huang, Da-Yun, e 黃大勻. "The Study of the Zinc Flake Produced by Alkaline Electrolysis with Pulse". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/87427406755527683917.
Texto completo da fonteResumo:
碩士國立高雄應用科技大學
機械與精密工程研究所
102
In this research is to use alkaline electrolysis with the pulse current to produce zinc flake. Experimental reaction system equipment is 500ml, the processing via pre-experiment that choose the anode is stainless steel, the cathode is magnesium plate, the anode and cathode plates are processed through the grinding and polishing. In this experiment, 6M NaOH as the electrolyte, through to change frequency, duty ratio, voltage, zinc in the electrolyte concentration of 6M NaOH and cathode plate to experiment that which parameter can be produced zinc flake thickness from 0.1 to 0.3μm. Changing in the current frequency are respectively 50Hz, 60Hz, 70Hz, 80Hz, 90Hz, 100Hz and 250Hz. The frequency range from 50Hz to 100Hz is the lower of the frequency that the zinc grow slower of grain growth and smaller particle. The frequency range from 100Hz to 250Hz are the higher of the frequency that the zinc rapid grow grain growth, but easily to reunite and large power; The duty ratio of pulse setting are respectively 0.025, 0.1, 0.2, 0.5, 0.8, the duty ratio in 0.5 is the best in another parameters, because of less reunite. The duty ratio range from 0.025 to 0.2 has the larger of the zinc surface pores. Changing in the voltage are respectively 100V, 150V, 200V, 250V and 300V, the voltage range from 100V to 200V is the lower of the voltage that produce zinc slowly and small of the particle, but reunion caused from resistance. the voltage range from 200V to 300V is the higher of the voltage that produce zinc fast and thick of the particle; Zinc in the electrolyte concentration are respectively 4, 6, 8, 12, 18, 24, 30 and 36 g-Zn/L. Zinc concentration range from 12 to 36 g-Zn/L are the higher of the zinc concentration that the zinc grains grew larger and thick; Zinc concentration range from 4 to 12 g-Zn/L are the lower of the zinc concentration that the zinc grains grew small. When the zinc concentration below 6 g-Zn/L or less, due to the small grains of zinc binding ability, resulting in agglomeration and thick. Conditions for the optimal parameters can be learned from the experimental and data statistics, voltage is 200V, the duty ratio is 0.5, frequency is 50Hz, anode plate is stainless steel, cathode plate is magnesium plate, plates spacing are 90mm, zinc in the electrolyte concentration is 4 g-Zn/L, electrolysis time is 30min, producing zinc flake thickness is 0.3μm.
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Cheng, Yi-Sheng, e 鄭逸聖. "A Study on Recovery of Lead and Zinc from Strongly Alkaline Wastewaters by Electrolysis". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/52765938753275416472.
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碩士國立中山大學
環境工程研究所
87
The recovery of lead from strongly alkaline wastewaters by electrowining using an electrolytic cell of fluidized-bed type and subsequent recovery of zinc by an electrolytic cell of Cu-Zn cell─fluidized-bed type were investigated. The fluidized-bed medium was nonconductive glass beads of 0.5 mm in diameter. Sheets of stainless steel and lead were used for recovery of lead as the anode and cathode, respectively in the electrolytic cell of the fluidized-bed type. On the other hand, sheets of copper and zinc were used for recovery of zinc as the anode and cathode, respectively in the electrolytic cell of Cu-Zn cell─fluidized-bed type. For the study of electrolytic recovery of lead, the experiments were carried out based on 23 full factorial design using current density, surface area of electrode, and operating temperature as the experimental factors. For the study of electrolytic recovery of zinc, current density, surface area of electrode, and stirring were selected as the experimental factors. The electrolytes include : (1) synthetical solutions containing single metal of lead, (2) synthetical solutions containing lead and zinc, (3) simulated wastewaters for the synthesis of zeolites from two municipal incinerator fly ashes (designated MIFA S and MIFA T, respectively) , and the actual wastewaters due to the synthesis of zeolites from MIFA S and MIFA T. It was determined that operating at a lower current density and a larger surface area of electrode would result in a better recovery of lead, a lower energy consumption, and a better current efficiency. The effect of operating temperature, however, was found to be insignificant. For zinc, operating at a higher current density, a smaller surface area of electrode, and stirring would result in a better current efficiency and improve its removal efficiency. 97.98 % and 98.56 % of lead were recovered from the actual wastewaters due to the synthesis of zeolites from MIFA S and MIFA T when 1.44 Amp-hr and 1.68 Amp-hr were applied, respectively. The energy consumption for these two cases were determined to be 8.065 Kwh/Kg and 3.970 Kwh/Kg, respectively. On the other hand, 97.62 % and 97.37 % of zinc were recovered from the actual wastewaters due to the synthesis of zeolites from MIFA S and MIFA T when 4.8 Amp-hr were applied. The energy consumption for these two cases were determined to be 141.0 Kwh/Kg and 167.8 Kwh/Kg, respectively. Lead of 79.74 % and 88.81 % in purity and zinc of 96.53 % and 91.06 % in purity were recovered from the actual wastewaters due to the synthesis of zeolites from MIFA S and MIFA T, respectively.
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Silva, João Fernando de Andrade Cardoso da. "Study of Dimensionally Stable Anodes for chlor-alkali electrolysis". Doctoral thesis, 2016. https://hdl.handle.net/10216/95969.
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Silva, João Fernando de Andrade Cardoso da. "Study of Dimensionally Stable Anodes for chlor-alkali electrolysis". Tese, 2016. https://hdl.handle.net/10216/95969.
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39
Azevedo, Daniela de Aguiar e. "Influence of the atmospheric plasma spray coating in electrodes properties to use in alkaline electrolysis". Master's thesis, 2017. https://hdl.handle.net/10216/106753.
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Azevedo, Daniela de Aguiar e. "Influence of the atmospheric plasma spray coating in electrodes properties to use in alkaline electrolysis". Dissertação, 2017. https://hdl.handle.net/10216/106753.
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Wu, Wei-Hua, e 伍偉華. "The analysis of efficiency on the acido-alkaline proton exchange membrane water electrolysis by using multi-electrode and pulse". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/g7q67b.
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碩士國立中央大學
能源工程研究所
106
In this experiment, multiple sets of nickel electrodes were used to produce hydrogen by proton exchange membrane water electrolysis (PEMWE) under the action of pulses and potassium hydroxide and sulfuric acid electrolytes. The relevant data were measured by potentiostat, and effects of applied voltage, number of electrode groups,base potential and pulses on the efficiency were investigated. Results show that dual cells and electrolytes can reduce the electrolysis voltage to 0.7V, and improve the efficiency of hydrogen production. Multi-electrode reduces the overall resistance and impedance, thereby improves the energy efficiency. finally as the pulse is added, the instantaneous current value is increased, and the generating hydrogen gas deviates rapidly from the surface of the electrode, accelerates the diffusion speed of the ions, and reduces the polarization phenomenon on the electrode. The efficiency of hydrogen production is thus improved. As the electrode spacing is 10 mm, the acid and alkali concentration is 30% by weight, and the frequency is 100Hz, The energy efficiency at 4V is about 15% higher than no pulse is used. and five groups of electrodes at 2V have the best efficiency of 98.6%.
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Wang, Li-Yeh, e 王儷曄. "Preparation of Ru and Ir Films on the Ni Inverse Opal as Cathodes for Hydrogen Evolution Reaction in Alkaline Electrolysis". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/33620036419403396838.
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碩士國立交通大學
材料科學與工程學系
98
The catalysts for hydrogen evolution reaction（HER）using Ru or Ir coated half-layer Ni inverse opal in 1 M KOH aqueous solution was investigated. RuO2 and IrO2 thin films were deposited by electroless plating and reduced subsequently to Ru and Ir at 200˚C under hydrogen treatment. The resulting electrode combined the advantage of large surface area and reasonable electro-catalytic activity. Variables such as deposition time, annealing temperature, and various annealing environments played critical roles. From SEM images, ICP-MASS and i-V polarization measurements, we determined the optimized processing condition. The reason is the surface area was decreased by the increased deposition time. According to the result of XRD and the thermal expansion coefficient of different materials on the substrate, the electro-catalytic activity was increased with the crystallinity but suffered from poor adhesion. Comparing both oxidative and metallic states of Ru and Ir films, we concluded that the metallic state revealed better catalytic ability.
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Langels, Hanna, e Oskar Syrjä. "Hydrogen Production and Storage Optimization based on Technical and Financial Conditions : A study of hydrogen strategies focusing on demand and integration of wind power". Thesis, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-435176.
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There has recently been an increased interest in hydrogen, both as a solution for seasonal energy storage but also for implementations in various industries and as fuel for vehicles. The transition to a society less dependent on fossil fuels highlights the need for new solutions where hydrogen is predicted to play a key role. This project aims to investigate technical and economic outcomes of different strategies for production and storage of hydrogen based on hydrogen demand and source of electricity. This is done by simulating the operation of different systems over a year, mapping the storage level, the source of electricity, and calculating the levelized cost of hydrogen (LCOH). The study examines two main cases. The first case is a system integrated with offshore wind power for production of hydrogen to fuel the operations in the industrial port Gävle Hamn. The second case examines a system for independent refueling stations where two locations with different electricity prices and traffic flows are analyzed. Factors such as demand, electricity prices, and component costs are investigated through simulating cases as well as a sensitivity analysis. Future potential sources of income are also analyzed and discussed. The results show that using an alkaline electrolyzer (AEL) achieves the lowest LCOH while PEM electrolyzer is more flexible in its operation which enables the system to utilize more electricity from the offshore wind power. When the cost of wind electricity exceeds the average electricity price on the grid, a higher share of wind electricity relative to electricity from the grid being utilized in the production results in a higher LCOH. The optimal design of the storage depends on the demand, where using vessels above ground is the most beneficial option for smaller systems and larger systems benefit financially from using a lined rock cavern (LRC). Hence, the optimal design of a system depends on the demand, electricity source, and ultimately on the purpose of the system. The results show great potential for future implementation of hydrogen systems integrated with wind power. Considering the increased share of wind electricity in the energy system and the expected growth of the hydrogen market, these are results worth acknowledging in future projects.