Tesis sobre el tema "Non-noble catalyst"
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Binny, Dustin. "Plasma functionalization of graphene nanoflakes for non-noble catalyst in fuel cells". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117182.
Texto completoDeux obstacles majeurs limitent présentement la viabilité commerciale des piles à combustibles à membrane électrolyte polymérique (PEMFC), leurs prix et durée d'opération. La contribution la plus importante au coût élevé de ces systèmes est l'utilisation du platine (Pt) en tant que catalyseur, en particulier au niveau de la réaction de réduction de l'oxygène (ORR). Une activité de recherche intense à l'échelle internationale est en cours pour trouver une alternative de remplacement pour le platine; cette thèse s'inscrit dans cet effort. Certains matériaux tels les nanostructures à base de carbone fonctionalisées semblent prometteurs en tant que catalyseur pour la réaction ORR, en particulier de par leur bonne conductivité électrique et leur résistance à la dégradation en milieux acides ou alkalins. Les sites catalytiques dans ces matériaux sont établis par une fonctionalization spécifique à l'azote sur laquelle une coordination d'atomes de fer est ajoutée, formant ainsi des sites catalytiques dispersés à l'échelle atomique. Une poudre nanocrystalline a récemment été développée au Laboratoire de procédés plasmas (LPP) de l'Université McGill. Les particules formant cette poudre ont la forme de nanoflocons de graphene (NFG) formés par la superposition d'une dizaine de plans de graphène en moyenne, et ayant une extension spatiale de l'ordre de la centaine de nanomètres. Les bords de ces plans ont la réactivité et la structure nécessaire pour incorporer des fonctionalités à l'azote tout en maintenant la cristallinité des plans intacte. La grande cristallinité de ces matériaux leur donne une très bonne résistance à la corrosion et au milieux acide des PEMFC, et en font un candidat prometteur pour remplacer le platine.L'objectif de cette thèse et d'insérer une quantité important de fonctionalization à l'azote de forme pyridinique et quaternaire sur les bords des NFG afin de créer les sites catalytiques nécessaires pour la réaction ORR. Un plasma thermique à couplage inductif (ICP) est utilisé pour la dissociation du méthane à haute température, suivi d'une nucléation homogène des NFG dans les zones de trempe rapide du jet de plasma. La fonctionalization à l'azote est effectuée dans une deuxième phase du traitement en modifiant les paramètres d'opération du plasma afin de mettre à profit les espèces exitées et dissociés d'un plasma d'azote.Une fonctionalization à l'azote jusqu'à 33.4 at.%Ntotal est obtenue dans ce projet, cette valeur étant 2.6 fois supérieure au meilleur résultat obtenu dans la littérature pour le graphène fonctionalizé à l'azote, et même 67% supérieure au meilleur matériau carboné avec fonctionalité azote. Les fonctionalités à l'azote pyridinique et quaternaire constituent respectivement 8.2 at.%Npyrid et 4.9 at.%Nquat. Ces résultats sont obtenus en maintenant la structure NFG intacte, en particulier en maintenant leur crystallinité et sans l'introduction de défauts de structure ou d'impuretés pouvant diminuer la performance du matériau au niveau des applications. Une déposition in situ des NFG à l'intérieur du réacteur de synthèse sur une membrane de carbone telle qu'utilisée dans les piles à combustible a également été démontrée. Un bon ancrage du dépôt de NFG est observé sur la membrane, et une croissance colonnaire avec porosité ouverte du film montre des épaisseurs du film de NFG de l'ordre du micromètre. Ces films montrent également les propriétés requises pour la RRO, soit la porosité, l'homogénéité sur une grande surface, un bon contact dans tout le réseau de particules pour le transport électrique, et l'accessibilité aux sites catalytiques. Les propriétés obtenues semblent en fait inégalée par les encres de particules catalytiques utilisées couramment pour la fabrication de la couche catalytique. Cette déposition in situ semble donc prometteuse et originale pour établir une nouvelle méthode de production de l'assemblage membrane-électrodes dans la fabrication des piles à combustibles du type PEM.
PEZZOLATO, LORENZO. "Fe-N-C non-noble catalysts for applications in Fuel Cells and Metal Air Batteries". Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2809320.
Texto completoBiddinger, Elizabeth Joyce. "Nitrogen-Containing Carbon Nanofibers as Non-Noble Metal Cathode Catalysts in PEM and Direct Methanol Fuel Cells". The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274389015.
Texto completoPascone, Pierre. "Synthesis, characterization, and performance of graphene nanoflakes as a non-noble metal catalyst in polymer electrolyte membrane fuel cells". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117071.
Texto completoUn des objectifs de la recherche sur les catalyseurs pour les piles à combustible à membrane électrolyte polymérique (PCMEP) est de trouver une alternative moins coûteuse au platine. En raison d'une cinétique lente, le platine est surtout utilisé dans la couche de catalyseur au niveau de la cathode pour la réaction de réduction de l'oxygène (RRO). Les nanomatériaux de carbone fonctionnalisés se présentent comme de bons candidats pour le remplacement du platine en raison de leur faible coût, d'une excellente conductivité électrique et d'une résistance chimique aux milieux acides et basiques. Dans ce travail, les nanoflocons de graphène (NFG) constitués en moyenne d'une dixaine de plans de graphène empilées, ont été utilisés comme support aux atomes de fer pour créer un catalyseur métallique non noble. Lors d'une première étape, le catalyseur à base de fer a été synthétisé. Les étapes de synthèse comprennent la production des NFG dans le plasma de méthane, l'adsorption de l'acétate ferrique, et la pyrolyse dans une atmosphère riche en ammoniac. La structure du catalyseur a été caractérisée tout au long des étapes de synthèse, et il a été constaté qu'un pourcentage de 0,28 % en atomes de fer ont été incorporé aux structures NFG. Cependant, la méthode de synthèse utilisée a provoqué une baisse générale de tous les paramètres cristallins calculés: la pureté a diminué de 28%, la taille des cristallites a diminué d'un facteur 2, et la taille moyenne des plans de graphène d'un facteur 4. La caractérisation a été également effectuée sur la couche de catalyseur après avoir été exposée à l'environnement PCMEP, révélant que les paramètres cristallins sont effectivement améliorés avec la durée d'exposition. Au bout de 100 heures, la pureté a augmenté de 32%, la taille des cristallites de 25%, et la taille moyenne des plans de graphène de 107%. L'exposition à l'environnement de PCMEP a réduit les dommages causés aux NFG pendant les étapes de synthèse. Le catalyseur synthétisé a été utilisé pour la RRO dans un PCMEP avec une surface active de 1 cm2. Un courant de 150 mA/cm2 a été observé pour une tension appliquée de 0,5 volts et une masse de catalyseur de 1 mg. Lorsque le courant est normalisé par rapport à la quantité de métal présent, le résultat de 11,8 A/mg de métal surpasse les catalyseurs à base de platine les plus utilisés dans l'industrie. Les catalyseurs au platine ont des valeurs allant de 3 à 14 A/mg de platine. Dans les expériences de stabilité, pour une tension appliquée de 0,5 Volts, aucune perte de courant n'a été observée à la fin des 100 heures de l'expérience. Cela représente une grande amélioration par rapport aux autres catalyseurs à base de fer, qui montrent une perte de 45% dans des conditions expérimentales identiques. La stabilité accrue de la structure du catalyseur démontre l'avantage d'utiliser des NFG par rapport à d'autres nanomatériaux de carbone, grâce à leurs cristallinité élevée et leurs grandes longueurs cristallines.
Tricàs, Rosell Núria. "Plasma modification on carbon black surface: From reactor design to final applications". Doctoral thesis, Universitat Ramon Llull, 2007. http://hdl.handle.net/10803/9288.
Texto completoEls sistemes de plasma a baixa pressió utilitzats han estat un reactor down-stream i un reactor de llit fluiditzat. Ambdós sistemes utilitzen un generador de radio freqüències a 13,56MHz per tal de general el plasma. Tots dos sistemes han estat optimitzats per la modificació de materials en pols. En el cas del reactor down-stream, s'ha estudiat a posició d'entrada del gas reactiu, la potència del generador i el temps de modificació per a tres tipus de tractament: oxigen, nitrogen i amoníac. En el cas del reactor de llit fluiditzat, els paràmetres que s'han estudiat han estat la distància entre la pols i la zona de generació de plasma, la mida de la partícula i la porositat de la placa suport.
Pel que fa a la modificació mitjançant la utilització de plasma atmosfèric, s'ha dissenyat un sistema que permet utilitzar una torxa de plasma atmosfèric comercial (Openair® de Plasmatreat GmbH) per tal de modificar materials en pols. Aquest sistema consisteix en un reactor adaptable a la torxa de plasma atmosfèric on té lloc la modificació, un sistema d'introducció de la pols dins de la zona de reacció així com també un sistema de refredament i col·lecció del material modificat que conjuntament permeten un funcionament quasi-continu del tractament.
S'ha utilitzat el reactor down-stream i el reactor a pressió atmosfèrica per tal de modificar tres tipus diferents de negre de carboni (N134, XPB 171 i Vulcan XC-72). D'altra banda, s'ha grafititzat i extret el N134 prèviament a la modificació per tal de realitzar un estudi sobre la influència de l'estructura superficial així com també de la presència d'impureses sobre la superfície del NC. L'oxidació i l'augment de nitrogen en superfície han estat les dues modificacions que s'han estudiat principalment per tal de comparar el resultat obtingut per les tècniques presentades.
El NC s'ha caracteritzat mitjançant diverses tècniques analítiques per tal de poder obtenir informació sobre els canvis produïts durant la modificació per plasma. Aquestes tècniques inclouen superfície específica, XRD, WAXS, STM per tal d'estudiar els canvis en la seva morfologia i estructura de la superfície. D'altra banda, per tal d'estudiar els canvis en la composició química s'han emprat mesures de pH, valoracions àcid/base i XPS.
Finalment, alguns dels negres de caboni modificats han estat seleccionats per tal de ser avaluats en aplicacions finals tal i com són el reforçament d'elastòmers i la seva activitat vers la reducció d'oxigen utilitzada en les PEMFC per tal d'eliminar els metalls nobles. En el primer cas, s'ha estudiat l'efecte sobre la cinètica i el mecanisme de vulcanització del negre de carboni modificat mitjançant el plasma atmosfèric. Aquest estudi s'ha dut a terme utilitzant dues tècniques complementaries com són les corbes reomètriques i la vulcanització de molècules model (MCV). També s'han realitzat mesures d'adsorció de polímer sobre el NC i Bound Rubber per tal d'estudiar la interacció polímer-càrrega la qual presenta una gran influència en les propietats finals dels materials. D'altra banda, s'ha estudiat també la capacitat del NC modificat vers a la reducció d'oxigen a partir de voltametria cíclica i s'han determinat les propietats del NC que poden influir de manera rellevant en l'activitat cataítica final del NC per a aquesta reacció. Tot i que es necessari fer una preparació posterior al tractament de plasma per a aquesta aplicació, el material final pot contribuir notablement a la eliminació de metalls nobles com a catalitzadors de reducció d'oxigen en les Piles de Combustible.
The present works deals with plasma modification of carbon black (CB). Although this type of treatment is widely used on flat surfaces handling problems should be overcome in order to treat powders as CB. In this study CB has been modified both by means of low-pressure and atmospheric pressure non-equilibrium plasmas. In order to accomplish this objective three different plasma reactors have been set-up; two at low pressure and one at atmospheric pressure working conditions.
Low pressure plasma reactors utilised in this work consist in a down-stream and a fluidised bed system working at Radio Frequency generation power (RF 13,56 MHz). Both reactors have been optimized to treat powder materials. For the down-stream reactor, position of the reactive gas inlet, and treatment conditions such as generator power and time have been studied for oxygen, nitrogen and ammonia treatments. For the fluidized bed reactor the distance of the powder sample to the plasma generation zone, particle size and support porosity have been taken into account.
Concerning atmospheric plasma, a device has been set up in order to adapt a commercial plasma torch (Openair® from Plasmatreat GmbH), for powder modification. An adaptable reactor, a method to introduce the powder in the plasma zone as well as a collecting system had been developed in order to obtain a quasi-continuous modification treatment.
Three types of CBs, N134, XPB 171 and Vulcan XC-72 have been modified in both the down-stream and the atmospheric plasma system. Graphitization and extraction of N134 were also carried out before plasma modification in order to study the effect of both impurities and surface structure of the CB during plasma modification. Surface oxidation and nitrogen enrichment were the two main studied treatments in both systems which allowed comparing their performances.
Unmodified and Modified CBs have been characterised from several points of view. Specific surface area, XRD, WAXS and STM have been used in order to study morphological and surface structure changes. On the other hand, pH measurements, acid/base titration and XPS were employed in order to study the surface chemistry composition changes that had taken place during plasma modification.
Some of the modified CB grades were selected in order to be tested in final applications such as rubber reinforcement and oxygen reduction non-noble metal catalyst for PEMFC. In the first case, the effect of atmospheric plasma treatment on the vulcanization kinetics and mechanism has been evaluated both by rheometre curves and the model compounding approach. Studies about the polymer-filler interaction have been also carried out by calculating bound rubber and adsorption from polymer solution. Last but not least, plasma modification capacity to enhance the oxygen reduction activity to obtain non-noble metal catalysts for PEMFC has been evaluated after the correspondent preparation. Oxygen reduction activity has been studied by means of cyclic voltammetry. The main CB properties which could play an important role in such applications have been analyzed.
Wang, Zhao. "Selective Hydrogenation of Butadiene over Non-noble Bimetallic Catalysts". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066102/document.
Texto completoThis work investigates the preparation and characterization of titania-supported non-noble bimetallic Cu-Zn, Ni-Zn and Fe-Zn catalysts with various atomic ratios and their catalytic properties for the selective hydrogenation of polyunsaturated hydrocarbons. Co-deposition-precipitation with urea (DPu) and co-deposition-precipitation at fixed pH (DP8) methods were employed for the samples preparation. The metal ions were sequentially deposited onto the TiO2 surface (the sequence of pH for ions deposition being CuII < ZnII ≈FeII < NiII) during the DPu, while they were simultaneously deposited using DP8 method. After sample reduction at proper temperature (350 °C for Cu-Zn, 450 °C for Ni-Zn and 500 °C for Fe-Zn), XRD and STEM-HAADF coupled with EDS showed that bimetallic nanoparticles were formed in Cu-Zn/TiO2 (Cu3Zn1 or Cu0.9Zn0.1 alloy) and Ni-Zn systems (Ni1Zn1 or Ni4Zn1 alloy) with average particle size smaller than 5 nm. Only metallic Fe was detected by XRD in Fe-Zn/TiO2. Zn is inactive for butadiene selective hydrogenation, and acts as a modifier of the monometallic catalysts whose activity follows the sequence: Cu < Fe < Ni. The addition of Zn slightly decreases the activity and influences the selectivity to butenes, but provides much more stable catalysts. The higher stability of the bimetallic catalysts was ascribed to the formation of lower amount of carbonaceous species during the reaction, resulting from the change in the size of the active metal surface ensembles by alloying with Zn
Jonsson, Daniel. "Evaluation of Non-Noble Metal Catalysts for CO Oxidation". Thesis, KTH, Skolan för kemivetenskap (CHE), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207363.
Texto completoWan, Abu Bakar Wan Azelee. "Non-noble metal environmental catalysts : synthesis, characterisation and catalytic activity". Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262524.
Texto completoOSMIERI, LUIGI. "Non-noble metal catalysts for oxygen reduction reaction in low temperature fuel cells". Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2640183.
Texto completoBlake, John. "Tungsten based electrocatalysts as non-noble alternatives to common platinum based fuel cell catalysts". Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/360211/.
Texto completoWatkins, Luke. "Development of non-noble catalysts for hydrogen and oxygen evolution in alkaline polymer electrolyte membrane electrolysis". Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2296.
Texto completoWang, Xinde [Verfasser], Regina [Akademischer Betreuer] Palkovits y Marcel [Akademischer Betreuer] Liauw. "Hydrogenolysis of biomass-derived platform chemicals to glycols over non-noble metal catalysts / Xinde Wang ; Regina Palkovits, Marcel Liauw". Aachen : Universitätsbibliothek der RWTH Aachen, 2020. http://d-nb.info/1217256792/34.
Texto completoLiu, Hongrui. "CO2 Chemical Utilization through Dry Reforming of Methane : Development of Non-Noble Metals Catalysts Supported on Natural and Synthetic Clays". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS480.
Texto completoThe development strategy of “growth-at-any-cost” has not been applied to the current development with the increased attention of various countries to environmental issues. But the dependence on fossil fuels such as petroleum will be still high in a short period of time based on the consideration of economic and social development. Thus, the focus on the production of hydrogen, syngas or other products using CO2 and/or CH4 that has attracted more attention in chemical products is the process of dry reforming of methane. Thus, this research focuses on proposing new supports loaded with different promoters to enhance the catalytic selectivity and stability of nickel-based catalysts for dry reforming of methane, and analyze the catalytic performance of prepared catalysts by associating temperature effects with multiple characterizations such as Brunauer-Emmett-Teller, X-ray diffraction, and CO2-temperature programmed desorption. First, different promoters with nickel are impregnated on natural clay or Fe/Cu-modified clay from Tunisia. Second, the synthetic clay derived catalysts are prepared by co-precipitation method to research the influences of structure on the DRM. In the end, the catalysts having the same composition as excellent Ni-hydrotalcite derived catalysts are further synthesized by ball milling to compare the effect of rotational speed and preparation
Ranjbar, Sahraie Nastaran [Verfasser], Peter [Akademischer Betreuer] Strasser y Christina [Akademischer Betreuer] Roth. "Synthesis and characterization of novel non noble metal catalysts for the electrocatalytic oxygen reduction reaction / Nastaran Ranjbar Sahraie. Gutachter: Peter Strasser ; Christina Roth. Betreuer: Peter Strasser". Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1066163839/34.
Texto completoJaouen, Frédéric. "Electrochemical characterisation of porous cathodes in the polymer electrolyte fuel cell". Doctoral thesis, KTH, Chemical Engineering and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3498.
Texto completoPolymer electrolyte fuel cells (PEFC) convert chemicalenergy into electrical energy with higher efficiency thaninternal combustion engines. They are particularly suited fortransportation applications or portable devices owing to theirhigh power density and low operating temperature. The latter ishowever detrimental to the kinetics of electrochemicalreactions and in particular to the reduction of oxygen at thecathode. The latter reaction requires enhancing by the verybest catalyst, today platinum. Even so, the cathode isresponsible for the main loss of voltage in the cell. Moreover,the scarce and expensive nature of platinum craves theoptimisation of its use.
The purpose of this thesis was to better understand thefunctioning of the porous cathode in the PEFC. This wasachieved by developing physical models to predict the responseof the cathode to steady-state polarisation, currentinterruption (CI) and electrochemical impedance spectroscopy(EIS), and by comparing these results to experimental ones. Themodels account for the kinetics of the oxygen reduction as wellas for the transport of the reactants throughout the cathode,i.e. diffusion of gases and proton migration. The agglomeratestructure was assumed for the description of the internalstructure of the cathode. The electrochemical experiments wereperformed on electrodes having a surface of 0.5 cm2 using alaboratory fuel cell.
The response of the cathode to various electrodecompositions, thickness, oxygen pressure and relative humiditywas experimentally investigated with steady-state polarisation,EIS and CI techniques. It is shown that a content in thecathode of 35-43 wt % of Nafion, the polymer electrolyte, gavethe best performance. Such cathodes display a doubling of theapparent Tafel slope at high current density. In this region,the current is proportional to the cathode thickness and to theoxygen pressure, which, according to the agglomerate model,corresponds to limitation by oxygen diffusion in theagglomerates. The same analysis was made using EIS. Moreover,experimental results showed that the Tafel slope increases fordecreasing relative humidity. For Nafion contents lower than 35wt %, the cathode becomes limited by proton migration too. ForNafion contents larger than 40 wt %, the cathode performance athigh current density decreases again owing to an additionalmass transport. The latter is believed to be oxygen diffusionthroughout the cathode. The activity for oxygen reduction ofcatalysts based on iron acetate adsorbed on a carbon powder andpyrolysed at 900°C in ammonia atmosphere was alsoinvestigated. It was shown that the choice of carbon has atremendous effect. The best catalysts were, on a weight basis,as active as platinum.
Keywords:polymer electrolyte fuel cell, cathode, masstransport, porous electrode, modelling, agglomerate model,electrochemical impedance spectroscopy, current interrupt,transient techniques, non-noble catalysts
Rêgo, Ulisses Alves do. "Catalisadores à base de metais não nobres formados por carbeto de tungstênio/carbono com estruturas FeNx e N/C para reação de redução do oxigênio". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-25072018-081311/.
Texto completoThis work aims to investigate low cost electrocatalysts based on tungsten carbide, carbon and iron submitted to different nitriding processes for the catalytic activity for the oxygen reduction reaction (ORR) in acid and alkaline electrolytes. The catalysts were divided into three distinct series, the first one comprising those with different tungsten carbide loads with respect to the carbon support, which were impregnated with the Fe2+ (2,4,6-Tris (2-pyridyl) - 1,3,5-triazine)2, [Fe (TPTZ)]2+, complex and treated at two different temperatures, 700 and 800 oC in nitrogen atmosphere. In the second series, the tungsten carbide load (30% W/C, m/m) was kept constant but this mixture was prepared using previously doped carbons using three different sources of nitrogen (HNO3, NH3 and HNO3/NH3); this was followed by the incorporation of the Fe[TPTZ]2+ complex and by the same heat treatments as mentioned above. In the third series, the electrocatalysts were prepared with three carbon types (Vulcan, Ketjenblack and Monarch), to which the Fe[TPTZ]2+ complex was added, followed by heat treatment at 800 °C under nitrogen and then by nitriding using a flow of ammonia at 950 °C. The three series of electrocatalysts synthesized in this work were carefully characterized by infra-red and UV-Visible spectroscopy, x-ray diffraction, transmission electron microscopy, x-ray energy dispersive, Raman spectroscopy, x-ray photoelectron spectroscopy. The electrochemical investigations were performed by cyclic voltammetry (CV) and by measurements of steady-state polarization curves for ORR using rotating ring-disc electrode technique, with catalytic materials forming thin films deposited on the disc. In the three catalyst series, materials with good performance for the ORR were developed. In the studies of the first series of catalysts, it was seen that the most active material was that formed by WC-FeNx/C with 30%W/C and 5% Fe pyrolyzed at 800 ° C. In the second series it was observed that the performances of the catalysts varied according to the type of nitriding protocol, presence of iron and temperature of heat treatment. The electrocatalysts showed higher performances in alkaline electrolyte, which were very close to that of a reference Pt/C catalyst. In the third series of electrocatalysts, the best performance was obtained with the Monarch carbon catalyst heat-treated with ammonia, whose catalytic activity was higher than all others, due to the greater number of FeNx and N/C active structures formed by the treatment with ammonia. The results in acidic and alkaline conditions for the first and second series of electrocatalysts suggest the occurrence of an indirect ORR mechanism (2e- + 2e-), that is, in acid (alkaline) media first O2 is reduced to H2O2 (HO2) followed by the reduction of H2O2 (HO2). The active sites predominantly involved in the reaction electrocatalysis are WC and FeNx in acid media and WC e N/C in alcaline media. Finally, for the third series of electrocatalysts, the acidic reaction involves a direct 4e- mechanism, having important participation of the Fe-N2 active sites.
Millan, Cabrera Reisel. "Computational study of heterogeneous catalytic systems. Kinetic and structural insights from Density Functional Theory". Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/161934.
Texto completo[CA] En aquest treball estudiem dues reaccions catalítiques rellevants per a la indústria i la localització de l'anió fluorur en la zeolita RTH, sintetitzada al mig fluorur. El capítol 3 és el primer capítol de resultats, on s'estudia la reducció quimioselectiva del nitroestireno en les superfícies Ni(111), Co(111), Cu(111) i Pd(111). El mecanisme generalment acceptat d'aquesta reacció està basat en l'esquema proposat per Haver-hi en 1898, en el qual la reacció pot transcórrer per dues rutes, la directa i la de condensació. En aquest capítol explorem totes dues rutes, i observem que la ruptura dels enllaços N-O i la conseqüent formació d'enllaços metall-O està més afavorida que la formació d'enllaços N-H en les superfícies Ni(111) i Co(111), a causa del caràcter oxofílico de tots dos metalls. Les etapes més lentes involucren la formació d'enllaços N-H. En les superfícies de metalls nobles com Pt(111) i Pd(111) s'observa el comportament contrari. La superfície Cu(111) és un cas intermedi comparat amb els metalls nobles i no nobles. A més, el nitroestireno interactua amb els àtoms de Cu de la superfície sol a través de grup nitre, amb la qual cosa és un candidat ideal per a aconseguir selectivitats prop del 100%. No obstant això, la superfície Cu(111) no és capaç d'activar la molècula d'H2. En aquest sentit, proposem un catalitzador bimetàl·lic basat en Cu, dopat amb un altre metall capaç d'activar a l'H2, com ara el Pd o el Ni. En els capítols 4 i 5 hem estudiat la reducció catalítica selectiva dels òxids de nitrogen (SCR, en anglés) amb amoníac. Usant mètodes de DFT, hem trobat rutes per a l'oxidació de NO a NO2, nitrits i nitrats amb energies d'activació relativament baixes. També, hem trobat que la reducció de Cu2+ a Cu+ requereix la participació simultània de NO i NH3. Posteriorment, hem estudiat la influència del NH3 en aquest sistema amb mètodes de dinàmica molecular. El NH3 interacciona fortament amb el Cu+ de manera que dues molècules d'aquest gas són suficients per a trencar la coordinació del catió Cu+ amb els oxígens de l'anell 6r, i formar el complex lineal [Cu(NH3)2]+. A més, els cations Cu2+ poden ser estabilitzats fora de la xarxa mitjançant la formació del complex tetraamincobre(II). A causa de la presència dels cations Cu+ i Cu2+ coordinats a la xarxa de la zeolita, apareixen bandes a la regió entre 800-1000 cm-1 de l'espectre infraroig. L'anàlisi de les freqüències IR de diversos models amb Cu+ i Cu2+ coordinats a l'anell 6r, o formant complexos amb amoníac indica que quan els cations Cu+ i Cu2+ estan coordinats als oxígens de l'anell 6r apareixen vibracions entre 830 i 960 cm-1. Freqüències en aquesta zona també s'obtenen en els casos en què NO, NO2, O2 i combinacions de dues d'ells estan adsorbidos en Cu+ i Cu2+. No obstant això, quan els cations Cu+ i Cu2+ estan fora de l'anell (no hi ha enllaços entre els cations de coure i els oxígens de l'anell 6r) no s'obtenen vibracions d'IR en aquesta regió de l'espectre. Aquests resultats indiquen que amb el seguiment de l'espectre IR durant la reacció SCR és possible determinar si els cations Cu+ i Cu2+ estan coordinats o no a l'anell de 6r en les etapes d'oxidació i reducció. Finalment, hem simulat el desplaçament químic de 19F, δiso, en la zeolita sintetitzada RTH. L'anàlisi del δiso dels diferents models utilitzats ens ha permés reconéixer la simetria del material sintetitzat, el qual pertany al grup espacial P1 i la nova cel·la unitat ha sigut confirmada experimentalment per difracció de raigs X. Finalment, hem assignat el senyal experimental que apareix en l'espectre de 19F a -67.2 ppm, al F- localitzat en un lloc T2, el qual és al seu torn la posició més estable. A més, el senyal a -71.8 ppm s'ha assignat a l'anió F- localitzat en un lloc T4.
[EN] In this work, we have studied two heterogeneous catalytic reactions and the localization of the fluoride anion in the as-made RTH framework, synthesized in fluoride medium. The first results, included in chapter 3, correspond to the chemoselective reduction of nitrostyrene on different metal surfaces, i.e, Ni(111), Co(111), Cu(111) and Pd(111). Until very recently, the reduction of the nitro group was explained on the basis of the general mechanism proposed by Haber in 1898 where the reaction can follow two routes, the direct and condensation route. We have explored the relevant elementary steps of both routes and found that because of the oxophilic nature of Ni and Co, the steps involving the dissociation of N-O bonds and formation of metal-O bonds are significantly favored compared with the other steps on both metal surfaces. In addition, the most demanding steps in terms of energy involve the formation of N-H bonds. These findings are in contrast to those of noble metals such as Pt and Pd, where the opposite behavior is observed. The behavior of Cu(111) lies in between the aforementioned cases, and also no chemical bonds between the carbon atoms of the aromatic ring of nitrostyrene and the Cu(111) surface is formed. For this reason, it might be an ideal candidate to achieve nearly 100 % selectivity. However, the Cu(111) surface does not seem to activate the H2 molecule. In this regard, we propose a bimetallic Cu-based catalyst whose surface is doped with atoms of a H2-activating metal, such as Ni or Pd. On another matter, we have also investigated the selective catalytic reduction of nitrogen oxides (SCR-NOx) and the main results are presented in the following two chapters, 4 and 5. By using static DFT methods, we found pathways for the oxidation of NO to NO2, nitrites and nitrates with relatively low activation energies. We also found, in agreement with experimental reports, that the reduction of Cu2+ to Cu+ requires the simultaneous participation of NO and NH3. Later, molecular dynamics simulations allowed us to assess the influence of NH3. The strong interaction of NH3 with the Cu+ cation is evidenced by its ability to detach Cu+ from the zeolite framework and form the mobile linear complex [Cu(NH3)2]+. Cu+ is no longer coordinated to the zeolite framework in the presence of two NH3 molecules. This observation and the fact that the T-O-T vibrations of the framework produce bands in the 800-1000 cm-1 region of the IR spectrum when perturbed by the coordination of Cu+ and Cu2+ cations, indicate that bands in the 800-1000 cm-1 regions should be observed when both copper cations are bonded to the framework oxygens. Finally, we have also studied NMR properties of the as-made pure silica RTH framework, aiming at locating the compensating fluoride anion. The calculation of the 19F chemical shift in different T sites and comparison with the experimental NMR spectra shows that the as-made RTH belongs to the P-1 space group with 16 Si, 32 O atoms, one fluoride anion and one OSDA cation. These results have been confirmed experimentally by XRD. In addition, we have assigned the experimental signal of 19F at -67.2 ppm to the fluoride anion in a T2 site, which in turn is the most stable location found, and the signal of -71.8 ppm to a fluoride anion sitting in a T4 site.
My acknowledgements to “La Caixa foundation” for the financial support through “La Caixa−Severo Ochoa” International PhD Fellowships (call 2015), to the Spanish Supercomputing Network (RES), to the Centre de Càlcul de la Universitat de València, to the Flemish Supercomputer Center (VSC) of Ghent University for the computational resources and technical support, and to the Spanish Government through the MAT2017-82288-C2-1-P programme
Millan Cabrera, R. (2021). Computational study of heterogeneous catalytic systems. Kinetic and structural insights from Density Functional Theory [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/161934
TESIS
Tu, Meng-Hsiu y 杜孟修. "Synthesis and Characterization of Non-noble Metal Catalyst in Oxygen Reduction Reaction of Fuel Cells". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/18947953440590826523.
Texto completo國立臺灣大學
化學研究所
100
The performance of fuel cell mainly determine by activity of catalyst for fuel decomposition. It’s usually using Pt-based catalyst due to high efficiency. However, Pt is a noble metal; expensive remained a major problem for development fuel cell commercialization. Recent research in cathode catalyst of fuel cell focused on non-noble metal catalyst substitution for Pt-based catalyst, it’s one of solutions to overcome this obstacle. However oxygen reduction reaction (ORR) activity of non-noble metal catalyst is lower than Pt-based catalyst. Thus, improve activity of non-noble metal catalyst become an important issue. Generally, catalytic structure and activity affect by heat treatment which will further influence nitrogen-doped structure in catalyst surface. Different types of nitrogen have different activity for oxygen reduction. Due to the role of heat treatment and carbon support are not fully understood yet, research on these two factors will assist in development fuel cell. In the present study, synthesis catalyst by impregnation method with various heat temperatures in ammonia condition. Used several analytic techniques to optimize synthesis factors and study formation mechanism with 0 dimension and 2 dimension carbon support. Both catalytic series used X-ray powder diffraction to prove crystal structure. X-ray absorption spectroscopy by using synchrotron radiation was applied for oxidation number of iron. Practical size and morphology studied by transmission electron microscopy. X-ray photoelectron spectroscopy characterized structure of nitrogen in catalyst. Surface area analyzer measured specific surface area. ORR and methanol poison tested by cyclic voltammery. Confirm iron nitride of catalyst change with temperature increase. The best ORR activity is Fe2N phase from 700℃ heat treatment. The carbon support dimension induces diverse loading mode, furthermore control practical size and catalytic activity.
Shain, Huang Yao y 黃耀賢. "Development of non-noble metal alloy Ni-Co-P electrode materials catalyst for proton exchange membrane fuel cells". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/29997009835752898343.
Texto completo國立聯合大學
化學工程學系碩士班
102
This study aims to develop a suitable non-noble metal of catalyst for proton exchange membrane fuel cell. It used carbon as the support and, used electroless plating to prepare Ni-Co-P alloy catalysts for better catalyst dispersion and reaction activity. To find the best catalyst preparation condition, experimental factors under investigation were:temperature、pH value and concentration of the plating bath, etc. Precious metals salts, such as hexachloroplatinate was then added on the plating bath. These catalysts were expected to have high activity, high corrosion resistance, and low platinum loading. The Ni-Co-P alloy catalyst from this study was examined by FE-SEM for surface morphology, EDS for element analysis, XRD for crystal phase identification, and RDE for electrochemical activity. The catalyst paste was coated on the carbon paper by doctor blade method. The membrane electrode assembly was obtained by laminated membrane and electrodes under proper hot-pressing condition. The performance of this single cell (voltage-current, power-current) was measured. The result suggested that he performance of Ni-Co-P alloy catalysts was obtained by calcination of the electroless plated XC-72R carbon powder. After calcinations of 1 hours at 450℃, the catalyst activity was evaluated by rotating disk electrode with electrode potential scan rate at 5mV/s in 0.5 M sulfuric acid saturated with oxygen. At electrode rotating speed of 900 rpm. The maximum specific current density of 16.58 mA/(cm2‧mg catalyst) was obtained.
Lin, Yu-Chuan y 林郁娟. "Synergistic effect of N and S incorporated non-noble metal catalyst for oxygen reduction reaction in acid and alkaline media". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/ppeb7y.
Texto completo國立臺灣科技大學
材料科學與工程系
103
The growing of greenhouse gases, deteriorating oils and energy issues realize people for the importance of environmental protection. Therefore, the fuel cell is significantly important due to a high efficiency, low pollution and renewable green energy. Fuel cells usually use platinum as catalyst. Unfortunately, the cost of platinum is expensive and it is not economically applied. Moreover, the resources of platinum in the world are getting scarce. Based on this view, the developing of non-noble catalysts become an attractive research topic in recent years. This study attempts to use precursors of nitrogen and sulfur as the dual doping by mixing with iron precursors as non-noble catalyst to replace the platinum catalyst. The prepared catalyst demonstrates good oxygen reduction ability after the pyrolysis with the electron transfer number of 3.99, which is very close to the ideal electron transfer number of 4.00. From the structure analysis, the graphene-like structure is found in the outer layer, which improves the oxygen reduction activity. In XPS spectrum for nitrogen and sulfur analysis, the high amount of pyridinic-N, quaternary-N and thiophene-S structure can significantly enhance the oxygen reduction activity. From XAS analysis, we can understand the bonding of element in the catalyst and speculate catalyst structure. In addition, the catalyst has an excellent stability after 30,000 cycles of stability test. It confirms that dual-doped containing nitrogen and sulfur can enhance the oxygen reduction ability by the synergistic effect.
Duan, Jingjing. "Advanced non-noble catalysts for electrocatalytic energy conversion processes". Thesis, 2016. http://hdl.handle.net/2440/112821.
Texto completoThesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Chemical Engineering, 2016.
Shaikh, Ali Anaam. "Development of Non-Noble Metal Ni-Based Catalysts for Dehydrogenation of Methylcyclohexane". Diss., 2016. http://hdl.handle.net/10754/621931.
Texto completoKo, Yi-An y 柯怡安. "Study on Catalytic Performance and Redox Reaction Analysis of Non-noble Perovskite as the Three-way Catalysts". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/8n9e49.
Texto completo國立交通大學
環境工程系所
106
For automotive emission control, CO and HCs would be oxidized to CO2 and H2O while NOx would be reduced to N2. The catalysts are referred as three-way catalysts (TWCs) since they can simultaneously remove three different types of air pollutants (CO, HCs and NOx). However, whether these three pollutants are interact at the same time or not, and also the relationship of redox reaction between these three pollutants were still not clear in the past research. On the other hand, due to the well-defined crystalline structure and high thermal stability, perovskite-type oxides (ABO3) have high potential for vehicle emission control catalysts. The commercial TWCs usually employ precious metals as the activated species. But in order to reduce the catalysts costs non-noble metals were selected and the characteristics of each metal were clarified in this study. In this study La, Ce or Sr were selected as the A site, while the B site was considered to be Mn, Fe, Co, Ni or Cu. Perovskite catalysts were prepared by precipitation method and the activities of fresh and thermal aged catalysts were tested in a wide temperature range of 70-450 oC under GHSV of 60,000 h-1. In addition, the physicochemical properties of the products were characterized by XRD, TEM, N2 physisorption measurement and NH3-TPD analysis. The results showed that CeMnO3 catalyst had the best overall performance among all tested catalysts. It has the best NO conversion efficiency of 42% at temperature of 215 oC. In addition, the T50 (temperature at 50% conversion) for C3H8 and CO were 294 oC and 197 oC, respectively; while the T90 for C3H8 and CO were 352 oC and 204 oC, respectively, for fresh CeMnO3 catalyst. Besides, the redox reaction analysis results showed that the increase of O2 concentration tends to increase the NO conversion at high temperature. And the addition of CO reductant can enhance the ability of NO reduction at low temperature.
"Development of Transition Metal Macrocyclic-Catalysts Supported on Multi-Walled Carbon Nanotubes for Alkaline Membrane Fuel Cell". Master's thesis, 2012. http://hdl.handle.net/2286/R.I.14848.
Texto completoDissertation/Thesis
M.S.Tech Technology 2012