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1
Chen, Dayi. "Nickel-based anodic electrocatalysts for fuel cells and water splitting". Thesis, The University of Utah, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10157943.
Testo completoAbstract (sommario):
Our world is facing an energy crisis, so people are trying to harvest and utilize energy more efficiently. One of the promising ways to harvest energy is via solar water splitting to convert solar energy to chemical energy stored in hydrogen. Another of the options to utilize energy more efficiently is to use fuel cells as power sources instead of combustion engines. Catalysts are needed to reduce the energy barriers of the reactions happening at the electrode surfaces of the water-splitting cells and fuel cells. Nickel-based catalysts happen to be important nonprecious electrocatalysts for both of the anodic reactions in alkaline media. In alcohol fuel cells, nickel-based catalysts catalyze alcohol oxidation. In water splitting cells, they catalyze water oxidation, i.e., oxygen evolution. The two reactions occur in a similar potential range when catalyzed by nickel-based catalysts. Higher output current density, lower oxidation potential, and complete substrate oxidation are preferred for the anode in the applications.
In this dissertation, the catalytic properties of nickel-based electrocatalysts in alkaline medium for fuel oxidation and oxygen evolution are explored. By changing the nickel precursor solubility, nickel complex nanoparticles with tunable sizes on electrode surfaces were synthesized. Higher methanol oxidation current density is achieved with smaller nickel complex nanoparticles. DNA aggregates were used as a polymer scaffold to load nickel ion centers and thus can oxidize methanol completely at a potential about 0.1 V lower than simple nickel electrodes, and the methanol oxidation pathway is changed. Nickel-based catalysts also have electrocatalytic activity towards a wide range of substrates. Experiments show that methanol, ethanol, glycerol and glucose can be deeply oxidized and carbon-carbon bonds can be broken during the oxidation. However, when comparing methanol oxidation reaction to oxygen evolution reaction catalyzed by current nickel-based catalysts, methanol oxidation suffers from high overpotential and catalyst poisoning by high concentration of substrates, so current nickel-based catalysts are more suitable to be used as oxygen evolution catalysts. A photoanode design that applies nickel oxides to a semiconductor that is incorporated with surface-plasmonic metal electrodes to do solar water oxidation with visible light is proposed.
2
Terry, Alexandre. "New mixed 3d metal-based oxyfluorinated materials as anodic catalysts for water splitting : from elaboration to mechanistic study". Electronic Thesis or Diss., Le Mans, 2024. https://cyberdoc-int.univ-lemans.fr/Theses/2024/2024LEMA1029.pdf.
Testo completoAbstract (sommario):
Si l'hydrogène est un vecteur énergétique prometteur pour le stockage durable de l'énergie, sa production doit reposer sur des technologies sans carbone. L’électrolyse de l’eau qui consiste à dissocier l'eau via un courant électrique issu d’énergies renouvelables est idéal pour produire un hydrogène vert. Toutefois, ce processus est entravé par une cinétique lente de la réaction OER (Oxygen Evolution Reaction, 2H2O ⇋ O2 + 4H+ + 4e-) à l'anode, nécessitant un apport d’énergie supplémentaire pour assurer un rendement énergétique satisfaisant. Ainsi, des catalyseurs, généralement des oxydes d'iridium et de ruthénium, sont utilisés pour réduire cette énergie en facilitant le transfert d'électrons et de protons impliqués dans la réaction OER. Toutefois, l’utilisation de ces métaux de plus en plus rares freine l'évolution de cette technologie. Pour y remédier, des catalyseurs à base d'oxydes et d'oxyhydroxydes de métaux de transition 3d, économiques et abondants, ont été mis au point pour l’électrolyse de l’eau en milieu alcalin et présentent des performances élevées. Ce travail de thèse présente la synthèse de nouveaux composés oxyfluorés à base d’éléments éco-compatibles et abordables en utilisant une voie d’élaboration simple et directe en deux étapes pour une application en tant qu'électrocatalyseur anodique dans un électrolyseur alcalin.L'étude initiale porte sur des catalyseurs oxyfluorés enrichis en fer, issus de la décomposition thermique à l'air ambiant de (Co1-xFex)2+Fe3+F5(H2O)7 (0 ≤ x ≤ 0,72). Les résultats montrent que la teneur en cobalt peut être réduite de 20% sans affecter les performances OER, permettant d'atteindre un surpotentiel de 320 mV à 10 mA.cm-2, une activité massique de 110 A.g-1 à 1,55 V vs. RHE et une grande stabilité. La deuxième partie de la thèse vise à améliorer les propriétés catalytiques du composé référence Co0,5Fe0,5O0,5F1,5 en remplaçant le cobalt par du nickel, connu pour son activité OER. La solution solide (Co(1-x)/2Nix/2)2+Fe0,5O0,5F1,5-y(OH)y (y ≤ 0.3) a été obtenue par décomposition thermique (Co1-xNix)2+FeF5(H2O)7 (0 ≤ x ≤ 1). La dernière partie vise à évaluer les performances de ces matériaux ainsi que d’étudier leur mécanisme de réaction. La composition x = 0,5 présente les meilleures performances, avec un faible surpotentiel de 290 mV à 10 mA.cm-2 et une activité spécifique de 3,9 A.m-2 de surface BET à 1,5 V vs. RHE. L'origine des propriétés catalytiques exceptionnelles de (Co0.25Ni0.25)2+Fe3+0.5O0,5F1,3(OH)0,2, mis en évidence via entre autres des analyses in-situ/operando ont été employées, proviendrait de la synergie entre Co et Ni, et l’implication d’oxygènes du réseau dans le mécanisme (LOM), contournant les limites théoriques liées au mécanisme conventionnelIf hydrogen is a promising energy vector for sustainable energy storage, its production must rely on carbon-free technologies. Water splitting powered by green electricity is ideal for producing a decarbonized energy carrier from water. However, this process is hampered by the sluggish kinetics of the oxidation evolution reaction (OER, 2H2O ⇋ O2 + 4H+ + 4e-) at the anode, requiring extra energy to ensure a suitable production rate. Catalysts, usually iridium and ruthenium oxides, are employed to reduce the energy requirement by facilitating electron and proton transfer involved in OER, but these metals are scarce, limiting the scalability of this technology. To overcome this, oxides and oxyhydroxides catalysts based on cost-effective and abundant 3d transition metal-based have been developed for alkaline water splitting, presenting high performance. In this way, this work presents the synthesis of new oxyfluorides with eco-compatible and affordable elements using a simple and straightforward two-step synthetic route for application as OER electrocatalyst in alkaline electrolyte.The initial study focuses on iron-enriched oxyfluoride catalysts from thermal decomposition under ambient air of (Co1-xFex)2+Fe3+F5(H2O)7 (0 ≤ x ≤ 0.72). Results show that cobalt content can be reduced by 20% without affecting OER performance, achieving an overpotential of 320 mV at 10 mA.cm-2, a mass activity of 110 A.g-1 at 1.55 V vs. RHE and high stability. The second part aims to enhanced the catalytic properties of Co0.5Fe0.5O0.5F1.5 reference by substituting cobalt with nickel, known for its OER activity. The (Co(1-x)/2Nix/2)2+Fe0.5O0.5F1.5-y(OH)y (y ≤ 0.3) solid solution have been obtained by thermal decomposition (Co1-xNix)2+FeF5(H2O)7 (0 ≤ x ≤ 1). The final section assesses the performance of these materials and studies their reaction mechanism. The x = 0.5 composition shows the best performance, with a low overpotential of 290 mV at 10 mA.cm-2 and a specific activity of 3.9 A.m-2 of BET surface area at 1.5 V vs. RHE. The origin of the exceptional catalytic properties of (Co0.25Ni0.25)2+Fe3+0.5O0.5F1.3(OH)0.2, highlighted via in-situ/operando analyses, among others, were employed, would stem from the synergy between Co and Ni, and the involvement of lattice oxygens in the mechanism (LOM), circumventing the theoretical limits linked to the conventional mechanism
3
McIntyre, Dale R. "Non-noble electrocatalysts for anodes in fuel cells with acidic electrolytes". Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620481.
Testo completo
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St, John Samuel. "Hierarchical Electrocatalyst Structure Control to Study Cathodic and Anodic Overpotential in Proton Exchange Membrane Fuel Cells". University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1384334674.
Testo completo
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Gcilitshana, Oko Unathi. "Electrochemical Characterization of Platinum based anode catalysts for Polymer Exchange Membrane Fuel Cell". Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5972_1266961431.
Testo completoAbstract (sommario):
In this study, the main objective was to investigate the tolerance of platinum based binary anode catalysts for CO poisoning from 10ppm up to1000ppm and to identify the
best anode catalysts for PEMFCs that tolerates the CO fed with reformed hydrogen.
6
Zellner, Michael. "Tungsten carbides as potential alternative direct methanol fuel cell anode electrocatalysts". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 213 p, 2006. http://proquest.umi.com/pqdweb?did=1172119451&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Testo completo
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Ren, Qiao. "Tungsten carbides as anode electrocatalyst of direct methanol fuel cell". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 97 p, 2007. http://proquest.umi.com/pqdweb?did=1400426011&sid=12&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Delaware, 2007.Principal faculty advisors: Jingguang G. Chen, Dept. of Chemical Engineering; and Thomas P. Beebe, Jr., Dept. of Chemistry & Biochemistry. Includes bibliographical references.
8
Kavanagh, R. J. "A computational study of anode electrocatalysis in direct ethanol fuel cells". Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678702.
Testo completoAbstract (sommario):
Density Functional Theory calculations are employed in the investigation of the ethanol oxidation reaction (EOR) at the anode of Direct Ethanol Fuel Cells (DEFC), with a view to mechanistic understanding of the reaction pathways, determination of the factors governing the onset potential of activity and selectivity towards C02, and ultimately the design of an optimal electrocatalyst in these regards. The lowest energy pathway of ethanol decomposition on platinum is identified and it is found that the reaction kinetics do not significantly vary with catalyst morphology. The aqueous medium is found to somewhat facilitate all reaction pathways. Surface hydroxyl is found to oxidise ethanol to acetaldehyde. Surface atomic oxygen is found to selectively oxidise adsorbed carbon monoxide to carbon dioxide. The onset potentials of surface hydroxyl and atomic oxygen on platinum are calculated to be in good agreement with experimental data. It is determined that onset potentials of < 0.1 V vs. SHE will result in inactive hydroxyls, while an onset potential of < 0.2 V results in inactive surface atomic oxygen, providing a target for catalyst optimisation. Onset of EOR is found to occur at potentials between 0.4 V and 0.5 V earlier on a range of platinum tin catalysts than on platinum, and Pt3Sn is found to be kinetically the best example of such a catalyst These findings are in good agreement with experimental observations. The addition of rhodium to platinum is found to result in a hydroxyl onset potential below the 0.1 V threshold for activity, and the near-optimal onset potential of surface atomic oxygen, resulting in excellent selectivity towards C02. However, the stability of the hydroxyl species delays the formation of atomic oxygen and so delays the onset of ethanol oxidation activity to an unacceptably high degree. This effect is believed to be general to metallic systems.
9
Shingleton, Anthony. "An electrochemical and physical study of chlorine electrocatalysis on commercial RuO₂/TiO₂ anodes". Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307129.
Testo completo
10
Gu, Ping. "Behaviour of the adsorbed chloride intermediate in electrocatalysis of anodic chlorine evolution at oxide film surfaces at platinum and ruthenium". Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5847.
Testo completoAbstract (sommario):
In this thesis, the investigation of the mechanism of chlorine evolution reaction at (i) both freshly reduced and pre-oxidized Pt electrodes; (ii) RuO$\sb2$-TiO$\sb2$ electrodes (DSA); (iii) other noble metals such as Pd, Ir, Ru and Rh by means of computer controlled anodic polarization, potential-relaxation transients and a.c. impedance measurements, will be presented. As described in Chapter V, the influence of co-deposited OH and O species in the surface oxidation process on the extent of chemisorption of the Cl$\sp-$ intermediate in the Cl$\sb2$ evolution reaction has been carefully examined. Experimental results reveal that the reaction rate at reduced Pt surfaces is much greater than that at pre-oxidized ones. This is because the oxide species have a significant effect in blocking the Cl$\sb2$ evolution kinetics. The detectable surface adsorption pseudocapacitance, which is associated with the "overpotential deposited" Cl$\sp-$ intermediate, at freshly reduced Pt and oxide free Pt surfaces in non-aqueous trifluoroacetic acid (TFA) medium supports this conclusion. In Chapter VI, some exploratory experiments at other noble metal (e.g., Pd, Ir, Ru, and Rh) electrodes in non-aqueous TFA solution have shown very interesting interfacial capacitance information, which must be interpreted probably in terms of more than one adsorbed reaction intermediate being present. In Chapter VII, a possible mechanism of recombination kinetically control has been proposed for the Cl$\sb2$ evolution reaction at RuO$\sb2$-TiO$\sb2$ electrodes, based on the observations of their steady-state behaviour, and electrochemical data from potential relaxation and a.c. impedance measurements. Local supersaturation of Cl$\sb2$ in the microstructure of the oxide film appears to make a contribution to the pseudocapacitance behaviour. Some of the results in this work have been published or in press, as listed below: (1) "Surface electrochemistry of the anodic chlorine evolution reaction at Pt influence of co-deposition of the Cl$\sp-$ intermediate", P. Gu and B. E. Conway, J. Chem. Soc. Farada Trans. 86(6) (1990) 923. (2) "Behaviour of the adsorbed Cl$\sp-$ intermediate in anodic chlorine evolution at thin-film RuO$\sb2$ surfaces", P. Gu and B. E. Conway, J. Appl. Electrochem., in press. (3) "Evaluation of Cl$\sp-$ adsorption in anodic chlorine evolution at Pt by means of a.c. impedance and potential relaxation experiments: role of the state of surface oxidation", P. Gu and B. E. Conway, J. Chem. Soc. Faraday Trans., in press.
11
SILVA, DIONISIO F. da. "Preparacao de eletrocatalisadores PtRu/C e PtSn/C utilizando feixe de eletrons para aplicacao como anodo na oxidacao direta de metanol e etanol em celulas a combustivel de baixa temperatura". reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9475.
Testo completoAbstract (sommario):
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
12
Olu, Pierre-Yves. "Etude de l'anode pour la pile à combustible directe aux borohydrures". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI101/document.
Testo completoAbstract (sommario):
Le travail présenté dans cette thèse porte sur l'anode de la pile à combustible directe aux borohydrures (DBFC, selon l'acronyme anglais). Une première approche pour développer l'anode de la DBFC est d'étudier cette anode à l'intérieur du système global de la DBFC. Dans cette optique, des anodes composées des catalyseurs Pt/C et Pd/C ont été caractérisée en banc de test DBFC. D'autres facteurs ont aussi été étudiés, tels que la morphologie de l'anode et la stabilité des nanoparticules des catalyseurs.Le catalyseur d'anode de la DBFC doit idéalement exhiber une activité catalytique suffisante pour la réaction d'oxydation des borohydrures (BOR), tout en minimisant la production et l'échappement d'hydrogène gazeux durant la BOR. Ces aspects sont relativement difficiles à étudier en raison des nombreuses variables ne dépendant pas de l'anode dans un système DBFC réel. Une solution à ce problème consiste à isoler l'anode de la DBFC et de l'étudier en configuration demi-pile, avec un environnement d'étude mieux contrôlé. Les différentes méthodes pour évaluer un catalyseur d'anode de DBFC en demi-pile sont discutées, et des marqueurs sont proposés pour l'évaluation pertinente d'un catalyseur d'anode de DBFC par rapport aux résultats de la littérature.Une autre stratégie possible pour développer des catalyseurs adéquats d'anode de DBFC est de mieux comprendre le mécanisme de la BOR. Dans cette optique, la BOR est étudiée sur des électrodes modèles à base de platine. Chaque type d'électrode modèle permet de contrôler un paramètre précis de la surface catalytique, menant ainsi à différentes études de la BOR. La sensibilité de la BOR à la structure de surface catalytique est étudiée sur des électrodes massives de platine (polycristallin et monocristallin). L'empoisonnement de la surface active de Pt durant la BOR est étudié sur nanoparticules de Pt déposées sur substrat carbone vitreux plan. Des électrodes à trois dimensions ont également été réalisées : nanoparticules de Pt déposées sur nanofibres de carbone verticalement alignées. Le dépôt de différentes quantité de Pt a permis d'étudier l'influence de la densité en sites actifs de Pt sur la BOR. Les résultats obtenus sur ces électrodes modèles sont discutés avec ceux de la littérature, et un mécanisme pour la BOR sur Pt est proposé. Ce mécanisme est simulé en utilisant une modélisation de micro-cinétiques de type champs moyens. Les courbes simulées reproduisent les caractéristiques majeures des résultats expérimentauxThe present work focuses on direct borohydride fuel cell (DBFC) anodes. A first approach to develop a suitable anode design for the DBFC consists in the study of the anode within the real DBFC system. In that frame, carbon-supported platinum and palladium nanoparticles are characterized and compared as anode electrocatalyst in DBFC configuration. Other variables such as the morphology of the anode and the stability of the catalyst nanoparticles are considered.The ideal DBFC anode catalyst should show a suitable electrocatalytic activity towards the borohydride oxidation reaction (BOR), without quantitative production/escape of gaseous hydrogen during the reaction. Studying these aspects is not straightforward using a real DBFC system, as the global behavior of the DBFC depends on numerous experimental variables external to the anode. In order to overcome this issue, a prospective anode catalyst can be isolated and specifically studied in half-cell configuration in a more controlled environment. The different methods possible for the evaluation of an electrocatalyst for the anode of the DBFC are discussed in this work, and benchmarks are proposed to compare a given material with the DBFC literature.Another strategy to develop suitable DBFC anode catalysts is to further understand the BOR mechanism. In that frame, the BOR is studied on model platinum-based electrodes with different levels of complexity. Bulk polycrystalline and single-crystals Pt flat electrodes enable to study the structure sensitivity of the BOR. The poisoning of the Pt active surface is investigated using Pt nanoparticles supported on flat glassy carbon substrate. Three-dimensional electrodes are also surveyed: Pt nanoparticles supported on vertically-aligned carbon nanofiber electrodes. The deposition of various amounts of Pt nanoparticles on the VACNF substrate enables to study the influence of the density of Pt active sites towards the BOR. The findings obtained using these model electrodes are gathered with previous results from the literature in order to propose a BOR mechanism on Pt. This mechanism is used in a mean-field microkinetics model. The simulated curves of this mechanism reproduce the main experimental features
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Yu, Zhiqiang. "Transient Studies of Ni-, Cu-Based Electrocatalysts in CH4 Solid Oxide Fuel Cell". Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1194625466.
Testo completoAbstract (sommario):
Dissertation (Ph. D.)--University of Akron, Dept. of Chemical Engineering, 2007."December, 2007." Title from electronic dissertation title page (viewed 03/12/2008) Advisor, Steven S. C. Chuang; Committee members, Lu-Kwang Ju, Edward Evans, W. B. Arbuckle, Stephen Z. D. Cheng; Department Chair, Lu-Kwang Ju; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
14
ROSESTOLATO, Davide. "Chemical and Physical Characterization of Electrocatalysts based on Iridium Oxide and prepared by Sol-Gel and Physical Vapor Deposition". Doctoral thesis, Università degli studi di Ferrara, 2014. http://hdl.handle.net/11392/2389035.
Testo completo
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ANTONIASSI, RODOLFO M. "Desempenho elétrico e distribuição dos produtos da célula a combustível com etanol direto utilizando Pt/C, PtSn/C(liga) e PtSnO2/C como eletrocatalisadores anódicos". reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10515.
Testo completoAbstract (sommario):
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Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Xaba, Nqobile. "Development of Anode Materials Using Electrochemical Atomic Layer Deposition (E-ALD) for Energy Applications". University of the Western Cape, 2018. http://hdl.handle.net/11394/6390.
Testo completoAbstract (sommario):
Philosophiae Doctor - PhD (Chemistry)Nanomaterials have been found to undeniably possess superior properties than bulk structures across many fields of study including natural science, medicine, materials science, electronics etc. The study of nano-sized structures has the ability to address the current world crisis in energy demand and climate change. The development of materials that have various applications will allow for quick and cost effective solutions. Nanomaterials of Sn and Bi are the core of the electronic industry for their use in micro packaging components. These nanomaterials are also used as electrocatalysts in fuel cells and carbon dioxide conversion, and as electrodes for rechargeable sodium ion batteries. There are various methods used to make these nanostructures including solid state methods, hydrothermal methods, sputtering, and vacuum deposition techniques. These methods lack the ability to control the structure of material at an atomic level to fine tune the properties of the final product. This study aims to use E-ALD technique to synthesis thin films of Sn and Bi for various energy applications, and reports the use of E-ALD in battery applications for the first time. Thin films were synthesised by developing a deposition sequence and optimising this deposition sequence by varying deposition parameters. These parameters include deposition potential, and concentration of precursor solution. The thin films were characterised using cyclic voltammetry, linear sweep voltammetry, chronoamperometry for electrochemical activity. These were also characterised using scanning electron microscope for morphology, x-ray diffraction for crystal phases, energy dispersive spectroscopy for elemental mapping, and focused ion beam scanning electron microscope for thickness. The elemental content was analysed using electron probe micro analysis and inductively coupled plasma mass spectrometry. The electrochemical impedance charge and discharge profile were used for electrochemical battery tests.
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Oliveira, Gustavo Rodrigues de. "Concilia??o entre modelos de mecanismos avan?ados de oxida??o eletroqu?mica". Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/17674.
Testo completoAbstract (sommario):
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Previous issue date: 2012-07-27Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Many pollutants dumped in waterways, such as dyes and pesticides, have become so ubiquitous that they represent a serious threat to human health. The electrochemical oxidation is presented as an alternative clean, efficient and economic degradation of wastewater containing organic compounds and a number of advantages of this technique is to just not make use of chemical reagents, since only electrical energy is consumed during the removal of pollutants organic. However, despite being a promising alternative, still needs some tweaking in order to obtain better efficiency in the elimination of persistent pollutants. Thus, this study sought a relationship between a recently discovered phenomenon that reflects the participation of dissolved oxygen in solution in the electrochemical oxidation process, as an anomaly, present a kinetic model that shows instantaneous current efficiency (ICE) above 100% limited by theory, manifested for some experiments with phenolic compounds with H2SO4 or HClO4 as supporting electrolyte with electrodes under anodic oxidation on boron doped diamond (BDD). Therefore it was necessary to reproduce the data ICE exposes the fault model, and thus the 2-naphthol was used as phenolic compound to be oxidised at concentrations of 9, 12 and 15 mmol L-1, and H2SO4 and HClO4 to 1 mol L-1 as a supporting electrolyte under a current density of 30 mA cm-2 in an electrochemical reactor for continuous flow disk configuration, and equipped with anodes DDB at room temperature (25 oC). Experiments were performed using N2 like as purge gas for eliminate oxygen dissolved in solution so that its influence in the system was studied. After exposure of the anomaly of the ICE model and investigation of its relationship with dissolved O2, the data could be treated, making it possible for confirmation. But not only that, the data obtained from eletran?lise and spectroscopic analysis suggest the involvement of other strongly oxidizing species (O3 (ozone) and O radicals and O2 -), since the dissolved O2 can be consumed during the formation of new strong oxidizing species, not considered until now, something that needs to be investigated by more accurate methods that we may know a little more of this system. Currently the performance of the electrocatalytic process is established by a complex interaction between different parameters that can be optimized, so it is necessary to the implementation of theoretical models, which are the conceptual lens with which researchers see
Muitos poluentes jogados em cursos d'?gua, como corantes e pesticidas, tornaram-se t?o onipresentes que representam uma s?ria amea?a a sa?de humana. A oxida??o eletroqu?mica se apresenta como uma alternativa limpa, eficiente e econ?mica ? degrada??o de efluentes contendo compostos org?nicos e uma das v?rias vantagens desta t?cnica ? justamente n?o fazer uso de reagentes qu?micos, uma vez que apenas a energia el?trica ? consumida durante a elimina??o dos poluentes org?nicos. Por?m, apesar de ser uma alternativa promissora, ainda necessita de alguns ajustes a fim de se obter melhor efici?ncia na elimina??o de poluentes persistentes. Assim este trabalho procurou alguma rela??o entre um fen?meno descoberto recentemente que evidencia a participa??o do oxig?nio dissolvido em solu??o no processo de oxida??o eletroqu?mica, com uma anomalia, presente no modelo cin?tico que apresenta corrente efetiva instant?nea (CEI) acima dos 100% delimitados pela teoria, que se manifesta para alguns experimentos realizados com compostos fen?licos tendo H2SO4 ou HClO4 como eletr?lito suporte sob oxida??o an?dica com eletrodos de diamante dopado em boro (DDB). Para tanto foi preciso reproduzir os dados de CEI que exp?e a anomalia do modelo, sendo assim, o 2-naftol serviu como composto fen?lico modelo, a ser oxidado nas concentra??es de 9, 12 e 15 mmol L-1, tendo H2SO4 ou HClO4 ? 1 mol L-1 como eletr?lito de suporte, sob uma densidade de corrente de 30 mA cm-2 em um reator eletroqu?mico de fluxo cont?nuo em configura??o de disco e equipado com ?nodos de DDB, ? temperatura ambiente (25 oC). Experimentos semelhantes foram realizados utilizando N2 como g?s de purga para eliminar o oxig?nio dissolvido em solu??o para que sua influ?ncia no sistema fosse estudada. Ap?s a exposi??o da anomalia do modelo da CEI e da investiga??o de sua rela??o com O2 dissolvido, os dados puderam ser tratados, o que tornou poss?vel sua confirma??o. Mas n?o ? s? isso, os dados obtidos da eletroan?lise e de an?lises espectrofotom?tricas sugerem a participa??o de outras esp?cies fortemente oxidantes, (O3 (oz?nio) e radicais O e O2 -), uma vez que o O2 dissolvido pode ser consumido durante a forma??o das novas esp?cies fortemente oxidantes, n?o consideradas at? agora, algo que precisa ser investigado por m?todos mais precisos para que possamos conhecer um pouco mais deste sistema. Atualmente o desempenho do processo eletrocatal?tico ? estabelecido por uma intera??o complexa entre diferentes par?metros que podem ser otimizados, por isso faz-se necess?rio a implementa??o de modelos te?ricos, que s?o as lentes conceituais com que os pesquisadores enxergam
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Silva, Dionisio Furtunato da. "Preparação de eletrocatalisadores PtRu/C e PtSn/C utilizando feixe de elétrons para aplicação como anodo na oxidação direta de metanol e etanol em células a combustível de baixa temperatura". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-23092011-155927/.
Testo completoAbstract (sommario):
Foram preparados eletrocatalisadores PtRu/C e PtSn/C utilizando feixe de elétrons para a redução dos íons metálicos em solução. Neste procedimento submeteu-se ao feixe de elétrons, sob agitação, soluções de água/etileno glicol (EG) e água/2- propanol, ambas contendo íons dos metais precursores e o suporte de carbono. Foram variadas as razões volumétricas água/2-propanol e água/etileno glicol, a razão atômica entre os metais, o tempo de irradiação e a taxa de dose. Os eletrocatalisadores obtidos foram caracterizados por análise de raios X por energia dispersiva (EDX), por difração de raios X (DRX), por voltametria cíclica (VC) e por espectroscopia Mössbauer. A atividade destes eletrocatalisadores na oxidação eletroquímica do metanol e do etanol foi avaliada por voltametria cíclica e cronoamperometria, utilizando a técnica do eletrodo de camada fina porosa, e pelas curvas de polarização obtidas em células a combustível unitárias operando diretamente com metanol e etanol. Os eletrocatalisadores PtRu/C preparados no meio reacional água/etileno glicol(EG) apresentaram razões atômicas diferentes das razões atômicas nominais. Os resultados sugerem que parte dos íons Ru(III) presentes no meio reacional não foram reduzidos. Os materiais obtidos apresentaram a fase cúbica de face centrada (cfc) da Pt e suas ligas e tamanhos de cristalito na faixa de 2 a 3 nm. Os eletrocatalisadores PtRu/C preparados em água/2- propanol apresentaram razões atômicas Pt:Ru similares às razões nominais. Os materiais obtidos apresentaram as fases cfc da platina e suas ligas e tamanhos de cristalito entre 3 e 4 nm. Os eletrocatalisadores PtSn/C preparados no meio reacional água/EG e água/2-propanol apresentaram razões atômicas Pt:Sn similares às razões nominais. Os materiais obtidos apresentaram as fases cfc da platina com tamanho de cristalitos na faixa de 2 a 4 nm e SnO2 (cassiterita). Os estudos sobre a oxidação eletroquímica de metanol e etanol mostraram que foi possível obter materiais com atividades similares e/ou superiores às atividades dos eletrocatalisadores comerciais PtRu/C (E-TEK) e PtSn/C (BASF), tidos como referência na área.PtRu/C and PtSn/C electrocatalysts were prepared using electron beam irradiation. The metal ions were dissolved in water/2-propanol and water/ethylene glycol solutions and the carbon support was added. The resulting mixtures were irradiated under stirring. The effect of water/ethylene glycol and water/2-propanol (v/v) ratio, Pt:Ru and Pt:Sn atomic ratios, the irradiation time and dose rate were studied. The obtained materials were characterized by Energy dispersive analysis of X-rays (EDX), X-ray diffraction (XRD), cyclic voltammetry (CV) and Mössbauer spectroscopy. The electro-oxidation of methanol and ethanol were studied by cyclic voltammetry and chronoamperometry using the thin porous coating technique. The electrocatalysts were also tested on the Direct Methanol and Ethanol Fuel Cells. PtRu/C electrocatalysts prepared in water/ethylene glycol showed Pt:Ru atomic ratios different from the nominal ones. The results suggested that part of the Ru(III) ions were not reduced. The obtained materials showed the face-centered cubic (fcc) structure of Pt and Pt alloys with crystallite sizes of 2-3 nm. PtRu/C electrocatalysts prepared in water/2-propanol showed Pt:Ru atomic ratios similar to the nominal ones. The obtained materials also showed the fcc structure of platinum and platinum alloys with crystallite sizes of 3-4 nm. PtSn/C electrocatalysts prepared in water/ethylene glycol and water/2-propanol showed Pt:Sn atomic ratios similar to the nominal ones. The obtained materials showed the platinum (fcc) phase with crystallite sizes in the range of 2 - 4 nm and a SnO2 (cassiterite) phase. The obtained PtRu/C and PtSn/C electrocatalysts showed similar or superior performance for methanol and ethanol electro-oxidation compared to commercial PtRu/C (E-TEK) and PtSn/C (BASF) electrocatalysts.
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ANTONIASSI, RODOLFO M. "Preparação de nanopartículas de platina com diferentes morfologias nos materiais Pt/C e PtSnO2/C para aplicação como ânodo em células a combústível de etanol direto". reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28036.
Testo completoAbstract (sommario):
Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T16:42:40Z
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Neste trabalho foi estudado o efeito da adição de íons haletos (Cl-, Br- e I-) sobre a morfologia das nanopartículas de Pt na produção de catalisadores de Pt/C e PtSnO2/C. Foi desenvolvida uma metodologia de síntese simples capaz de produzir nanopartículas de Pt predominantemente cúbicas com orientação preferencial Pt(100), diretamente suportadas em carbono sem o uso de agentes estabilizantes. Brometo de potássio foi utilizado como agente direcionador de superfície para obtenção do material preferencialmente orientado. O controle de adição do precursor de Pt e de KBr foi crucial para obter nanocubos de Pt de 8 nm bem dispersos sobre o suporte. Na preparação dos catalisadores de PtSnO2/C, o processo de adição do SnCl2 também foi decisivo na obtenção das nanopartículas de Pt com tamanho e morfologia de interesse. Nanocubos de Pt coexistindo com SnO2 disperso foram exclusivamente obtidos ao adicionar o SnCl2 na etapa final da síntese, quando as nanopartículas cúbicas de Pt já estavam formadas. Enriquecidos de domínios Pt(100), os materiais em forma cúbica de Pt/C e PtSnO2/C se mostraram menos afetados pelo acúmulo dos intermediários indesejados provenientes da reação de eletro-oxidação de etanol e foram mais tolerantes ao envenenamento por monóxido de carbono. Resultados similares foram observados para a oxidação de CO e metanol, utilizados como apoio para compreensão da eletro-oxidação de etanol. O efeito morfológico destes materiais no desempenho elétrico em célula a combustível de etanol direto foi avaliado. Pt/C e PtSnO2/C contendo nanopartículas de Pt com orientação preferencial Pt(100) forneceram maiores valores de densidade de potência e de seletividade para CO2 comparados aos catalisadores de Pt/C e PtSnO2/C com nanopartículas de Pt sem orientação preferencial.
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Lyke, Stephen Erwin. "Anodic oxidation of sulfur dioxide electrocatalysis and reactor performance analysis /". 1991. http://catalog.hathitrust.org/api/volumes/oclc/24296873.html.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Wisconsin--Madison, 1991.Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 261-278).
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Li, Hua-Wun, e 李華文. "Experimental Study on Hull Biofouling Prevention Using Dimensional Stable Anode Electrocatalyst". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/42tjwn.
Testo completoAbstract (sommario):
碩士國立高雄海洋科技大學
輪機工程研究所
106
Abstract Hull fouling will increase the resistance of the ship while driving, and the increase in fuel consumption will also cause hull corrosion. Electro-Catalytic electrolysis of seawater to produce chlorine (Cl) or hypochlorite ions (ClO-), strong oxidizing forces to eliminate bacteria and micro-oganism, inhibit the growth of micro-oganism, the low voltage electrode method is applies direct current, the use of low voltage electrode method transfer electronic and catalytic between the hydroxyl radical, destroy or reduce the adhesion of microbial, inhibit the parasite of microbial mucosa. This study explores commercial dimensionally stable anode DSA (Dimensionally Stable Anode, DSA), known for good conductivity and excellent corrosion resistance, potential application to biofouling prevention. The use of DSA has a good conductivity, excellent corrosion resistance. Simultaneously, DSA itself processes the use of non-toxic gases and substances, effective to inhibit microbial attachment, and does not destroy the marine ecology. The experiment of this study places firstly immerse uncoated blank titanium and DSA sheets in seawater, for observation of marine growth. Electro-Catalytic DSA in seawater is performed at 0.7-0.8 V vs. SCE, which is determined by initiation of gas evolution of the electric catalyst. And then select the appropriate voltage (DSA0.7~0.8V). The experi-mental results show that, uncoated and non-powered titanium sheets immersed in seawater for 10 days began to grow hydroid and algae. The electric-driven DSA shows no biological growth for 30 days in seawater, proving the feasibility of DSA to prevent hull fouling. Keywords: Hull Biofouling, Electro-Catalytic, Hydroxyl Radical, Dimensionally Stable Anode
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Wong, Chee-Yong, e 黃致榮. "Effect of organic acid on the electrocatalyst activity of PEMFC anode". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/09315054437572459686.
Testo completoAbstract (sommario):
碩士逢甲大學
綠色能源科技碩士學位學程
102
A comprehensive study has been made to explore the role of organic acids on electrocatalytic performances of platinum (Pt) nanoparticles supported on carbon porous materials (CPMs) in proton exchange membrane fuel cells (PEMFCs). In particular, the effects of carboxylic acids (R-COOH), viz. formic acid, acetic acid, propionic acid, and butyric acid on catalytic activity, stability, and durability of anodic Pt/CPM electrocatalyst in direct methanol fuel cells (DMFCs) were investigated. In the presence of doped carboxylic acids, the electrooxidative activity of Pt/CPM follows the trend: Formic acid (HCOOH) < Acetic acid (CH3COOH) < Propionic acid (C2H5COOH) < Butyric acid (C3H7COOH), revealing a consistent increase in the severity of catalyst deactivation with the number of carbons on the alkyl chain of the dopant. The Pt/CPM was found to exhibit electrocatalytic performances and tolerance for poisoning than a commercial Pt/XC-72 catalyst with a similar Pt loading (20 wt%). Moreover, a notable increase in mass activity up to ca. 150% over the spent Pt/CPM catalyst was observed up on removing the organic acid in the feed stream, indicating that catalyst poisoning by deactivation may be revived, even to its “intrinsic” activity.
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Guo, Mann-Charn, e 郭蔓嬋. "Adding metal oxides in Pt anode electrocatalysts for enhancing CO tolerance in proton exchange membrane fuel cells". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/81445252234693930210.
Testo completoAbstract (sommario):
碩士國立中興大學
環境工程學系所
100
The aim of this study is to discuss the preparation of the membrane-electrode assembly (MEA) by using carbon nanotubes (CNTs) in proton exchange membrane fuel cell (PEMFC). Different pretreatment procedures of carbon supports are also considered to evaluate the catalytic activity with various catalysts. Besides, the addition of metal oxides such as CeO2、ZrO2 and SnO2 are investigated to enhance the electrocatalytic activity and the tolerance of different CO concentrations. All catalysts are characterized by means of FESEM, TEM, XRD, BET and ESCA. The experimental results show that the effects of various preparation methods on the MEA to determine the best operating parameters. The 240 seconds hot-press with temperature is 135 oC has been selected for further experiments. Additionally, the investigation of the catalytic activity compared with different pretreatment procedures for catalyst support indicates that CNTs pretreated with nitric acid at 50 oC for two days (CNTs-50 oC-2d) that are supported active metals has higher catalytic activity than others. It is supposed that CNTs-50oC-2d supports have higher surface area provided more active sites and the gas molecules may easily diffuse into the pores to be reacted. Moreover, the electrocatalytic activities by using several catalysts included 5%SnO2-5%Pt/C, 5%ZrO2-5%Pt/C at the same voltage are higher than those without adding any MOx, and 5%SnO2-5%Pt/C is the effectiveness catalyst found after testing .On the other hand, it was reported that the CO tolerance of electrocatalyst was also enhanced by the addition of SnO2 and ZrO2 under the CO concentration is 100 ppm. The CO tolerance are in the following order as 5%ZrO2-5%Pt/C > 5%SnO2-5%Pt/C > 5%Pt/C > 5%CeO2-5%Pt/C. The effect of various concentrations of CO (0、50 and 100 ppm) shows that 5%ZrO2-5%Pt/C catalyst displays a better CO tolerance than the others. Consequently, the electrocatalytic activity and CO tolerance of catalysts are both enhanced while MOx added with Pt.
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Lee, Eungje. "Development of anode catalysts for direct alcohol fuel cells". Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1708.
Testo completoAbstract (sommario):
Direct alcohol fuel cells (DAFC) are attracting considerable interest to meet a variety of energy needs as they offer higher efficiency with less pollution compared to other conventional energy-conversion devices. However, the sluggish alcohol oxidation reaction kinetics and durability problems of the conventional Pt-Ru anode catalyst hamper the commercialization of the DAFC systems. With an aim to overcome these problems, there have been intensive efforts to alloy Pt-Ru with other metals. Although such strategies have led to some enhancement in activity, the durability problem caused by the instability of Ru could still not be alleviated. In this regard, this dissertation focuses on the development of non-Ru electrocatalysts with high activity and durability for DAFC applications. First, Ru-free, Pt-based bimetallic electrocatalysts for methanol oxidation reaction (MOR) were studied. Particularly, Pt-Sn and Pt-CeO₂ catalysts were synthesized, respectively, by a polyol method and a one-step reverse microemulsion (RME) method. The prepared samples are investigated for phase and morphological evaluations by various material-characterization techniques. Cyclic voltammetry and accelerated durability tests revealed that these alternative catalysts have much higher stability with a catalytic activity for MOR comparable to that of Pt-Ru. In the case of Pt-CeO₂, an improved particle morphology is obtained by the RME synthesis, and the advantage of the RME method is reflected by a higher catalytic activity in comparison to that of Pt-CeO₂ synthesized by the conventional synthesis method. It has been known that Pt-Sn is better than Pt-Ru for ethanol oxidation reaction (EOR), and the direct ethanol fuel cells (DEFC) employing Pt-Sn as the anode catalyst have better durability than the DMFC system employing a Pt-Ru anode catalyst. Therefore, this dissertation then focused on the enhancement of the catalytic activity for EOR by incorporating a third metal M to the Pt-Sn catalyst. Following the synthesis and characterization of the Pt-Sn-M (M = Mo and Pd) alloys, the effect of M on the enhanced catalytic activity of Pt-Sn-M is presented. The activity enhancement of the above catalysts is based on the promoting effect of the second or third elements added to Pt. However, in the final chapter of this dissertation, the activity enhancement of Pt nanoparticle itself through the formation of low energy surfaces is investigated. Carbon-supported Pt nanoparticles are synthesized in mixed water-ethylene glycol solvent, and the positive effect of the mixed solvent on both the morphology and surface structure of the Pt nanoparticles for COad oxidation is discussed.text
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Ke, Hsin-Yu, e 柯心喻. "Preparation of PtRuTa/C electrocatalysts for improving the stability of Pt-Ru based anodes for use in direct methanol fuel cell". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/50608101586068757478.
Testo completoAbstract (sommario):
碩士國立高雄應用科技大學
化學工程與材料工程系
100
PtRuTa/C tri-metal electrocatalysts were prepared by impregnation method for use as anode catalysts, with an attempt to improve the stability and electrocatalytic activity of the PtRu for methanol oxidation reaction (MOR). The lattice parameters, composition, and particle size distribution of catalysts were characterized by the means of X-ray diffractometer (XRD), X-ray energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), and scanning electron microscope (SEM), respectively. The electrochemical behaviors of the electrodes were studied by cyclic voltammetry (CV), chronoamperometry (CA), and CO-stripping voltammetry. The inductively coupled plasma-mass spectrometer (ICP-MS) was used to detect the dissolved species in the immersing solutions (0.5 M H2SO4 + 2.0 M CH3OH), used for examining the degradation and dissolution of the PtRu catalysts during the out-of-service time. The results show that the atomic ratios of Pt, Ru, and Ta in the PtRuTa/C catalysts are approximately equal to the known values in the original precursor solutions, indicating the successful preparation of the PtRuTa catalysts. The particle size of the PtRuTa/C catalysts is 4.3 to 6.1 nm with a spherical structure. The catalysts are well dispersed on the carbon black supports; however, the distributions of Pt atoms decrease, while the agglomeration increases, with the increase of Ta content. On the other hand, the exact methanol oxidation on-set potential (VMOSP) at various PtRu based catalysts are obtained accurately by extrapolation at a scan rate of zero. The results show that the optimum ratio of Pt: Ru is ca. 1:1, and the dependence of VMOSP on the Ta content in the catalyst is insignificant。In addition, the stability of the catalysts for MOR increases significantly with the increase of Ta contents, while the specific activity of the catalysts increases when the Ta content is less than 5 atom %. Additionally, the degradation and dissolution of the PtRu catalysts during the out-of-service time examined by immersing tests shows that, as well as that in the operation time, the dissolution of Ru on the catalysts is effectively depressed in the presence of Ta due to the formation of Ta2O5.
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Yu-WeiHuang e 黃裕暐. "Syntheses and Characterizations of Electrocatalyst of Pt Loaded on a Three Dimensional Graphene Grown with Carbon Nanotubes for Anode of DMFCs". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/66207964662607920022.
Testo completo
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Coletti, Kathryn. "Development of a model for the investigation of the role of mixed conduction in a solid oxide fuel cell anode to enable effectiveness of electrocatalyst infiltration". Thesis, 2020. https://hdl.handle.net/2144/41469.
Testo completoAbstract (sommario):
Despite their potential for high efficiency energy production, the high temperature at which solid oxide fuel cells (SOFCs) must operate places significant restraints on materials selection which in turn limits the power density. Liquid infiltration of nickel nanoparticle catalysts into the anode can produce a higher density of reaction sites and has been shown to improve cell performance at significantly lower operating temperatures. Not all of these nanoparticles are connected to the Ni web network that provides a pathway for electron conduction to the external circuit, yet they improve the performance of the cell. Simulation provides an opportunity to gain an understanding of this physical phenomena where the scale of the regions in which the interaction between isolated Ni nanoparticle and connected Ni web take place makes direct experimental observation impossible. The purpose of this work is to develop a numerical model for charge transport in the electrolyte and around the Ni reaction sites. In Wolfram Mathematica 11.3 Student Edition, a 1-D model is established first, then built upon with increasing complexity to a 2-D model in which the Ni interfaces are scaled up to microns in size. Analytical solutions and dimensional analysis are used where possible to ensure the accuracy of the model results. Preliminary results from a micron-scale model indicate the existence of a favorable electric potential gradient between the isolated Ni particle and Ni web to drive current flow. The results also show a decrease in the magnitude of the electric potential measured on the isolated Ni particle as it is moved closer to the Ni web, and thus its position can be optimized. However, further work is needed to bring the scale of the Ni interfaces to their realistic dimensions in nanometers.