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Furman, Scott Anthony. "Surface chemistry of iodine on platinum (111)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ36639.pdf.
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Sun, Grace Siswanto. "Simulations of platinum growth on Pt(111) using density functional theory and kinetic monte carlo simulations /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9672.
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Shiller, Paul Joseph. "Reactions of methanol and carbon monoxide on ad-atom modified platinum(111) and molybdenum(110) surfaces: Molecular orbital study." Case Western Reserve University School of Graduate Studies / OhioLINK, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=case1055946339.
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Zheng, Chaozhi. "Coverage, step and quantum effects on surface diffusion of H on Pt(111) surfaces /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202004%20ZHENG.
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Loh, Andrea. "Study of the adsorption and reaction of 1-epoxy-3-butene on platinum(111)." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447652.
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Yim, Chi Ming. "LEEM investigations of adsorption and diffusion of CO on the Pt(111) surface /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202007%20YIM.
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Ihm, Hyeran. "Thermal activation and intermediates of six-membered cyclic hydrocarbons and alkyl nitrites on Pt(111) and Cu(100) /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.
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Ridley, Paul. "Underpotential deposition of lead on gold and platinum (111) electrode surfaces investigated by scanning tunnelling microscopy." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343615.
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Gómez, Marín Ana María. "Role of Surface Species at Pt(111) in Electrochemical Oxygen Reduction." Doctoral thesis, Universidad de Alicante, 2014. http://hdl.handle.net/10045/42320.
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Den, Boef Martinus. "Assessment of the national DSM potential in mine underground services / M. den Boef." Thesis, North-West University, 2003. http://hdl.handle.net/10394/111.
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ESKOM is moving towards a price structure for electricity which reflects, as far as
possible, the real cost of generation. It is called real time pricing (RTP). ESKOM
developed this cost structure to coax customers to use more electricity in off-peak
periods (low cost of generation) and less electricity in peak periods (high cost of
generation). However, many industries do not effectively use these price offerings
from ESKOM to the detriment of themselves and ESKOM.
In previous research improvements to this situation for the South African mining
industry were investigated. ESKOM funded research to find the potential for load
shifting on mines using RTP. The RTP investigation focused on the supply side
management (SSM) in the mining context of underground services on gold and
platinum mines. Elements investigated included the ventilation, cooling and pumping
(VCP) systems. (Except for pumps, these plants are generally installed
aboveground.)
Previous research showed a national RTP and SSM potential to shift 500 MW of
electrical load for a period of 5 hours. Through the previous research it became clear that the mines were previously able to
react partially to the price signals. However, it was proved by the research that the
full load shift potential can only be realised through the use of integrated dynamic
simulation and optimisation.
An even higher potential exists for load shift and electricity efficiency through demand
side management (DSM) on the underground services. Therefore, if underground
DSM strategies are combined with SSM strategies, a further and much bigger
potential can be exploited to the benefit of ESKOM and the mines. Due to these
factors this study was undertaken.
Three case study mines were identified for this study. They are Kopanang and
Target, both gold mines, and Amandelbult, a platinum mine. The DSM potential on
each of these mines was calculated using simulation, calibration, verification and
optimisation.
These results were presented to mine management to negotiate the implementation
of the proposed strategies on one of the mines. Kopanang's management agreed to
the implementation of these strategies for a trial period of 3 months after which the
success would be evaluated.
The results of the implementation, together with the case study results, were used to
calculate the national DSM potential in the mining sector through extrapolation. The
DSM potential amounts to 650 MW of load per day as well as 5% on electricity
consumption. This amounts to a potential saving of R72.1 million per year using
current tariffs. This means that ESKOM can save about R5000 million on the
building of a new power station to supply the equivalent load to the DSM potential.
Now that the national impact has been calculated and discussed, all these findings
must be used to motivate the implementation of these strategies throughout the
mining sector. A similar project can be undertaken to look at possible DSM
strategies in the industrial sector.
This might prove to be more difficult as the electricity intensive systems are mostly all
linked to the final production. In the mind of management this out-weighs the
possible cost savings that can be achieved.
ESKOM and the NER will have to rethink their strategy. Through DSM and load
shifting actions alone the pending electricity crisis will not be averted. The current tariff structures should be amended to not only reflect the true cost of electricity but
also provide incentive for DSM and load shifting.
Another problem that must be addressed to achieve the DSM targets set for 2007 is
the time that it takes to complete the study as well as the implementation time.
Software can easily be created to help in the speeding up of the case study itself, as
the process and steps followed, as well as models used, are very generic (at least in the gold and platinum mining sector).Thesis (Ph.D. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.
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Mane, Mane. "Adsorption des hydrocarbures insaturés (éthylène et propylène) sur la surface Pt(111) nue et en présence de coadsorbats (alcalins, oxygène, alcalins oxydés) : étude par AES, TDS, UPS, XPS et NEXAFS." Nancy 1, 1993. http://www.theses.fr/1993NAN10062.
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Nous avons étudié l'influence de la température d'adsorption et des coadsorbats (atomes alcalins, oxygène atomique, alcalins oxydés) sur les modes d'adsorption des hydrocarbures éthyléniques (éthylène, propylène) sur Pt(111). Ces différents modes d'adsorption ont été identifiés sous ultravide par des méthodes spectroscopiques complémentaires (UPS, XPS, NEXAFS, TDS). L'étalonnage des quantités d'alcalins déposes a été obtenu par la spectrométrie des électrons Auger et les mesures de potentiel de sortie en UPS. Les oxydes de potassium ont été préparés et identifiés en utilisant la technique UPS et en comparant le nombre et les positions des orbitales moléculaires dans le régime de la sous-monocouche d'alcalin aux résultats en couches épaisses de la littérature et aux prédictions théoriques. Les résultats expérimentaux obtenus sont interprétés sur la base de modèles théoriques existants. Des conséquences probables de l'utilisation des oxydes d'alcalins comme promoteurs des catalyseurs utilises dans la synthèse catalytique des hydrocarbures ont été soulignées
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EL, ACHI RAMAL. "Oxydation electrocatalytique du methanol en milieu acide sur des surfaces de platine a marches pt(s)n(111)(111)=pt(s)(n-1)(111)(110)." Paris 6, 1993. http://www.theses.fr/1993PA066083.
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Ce travail porte sur le role de la structure cristalline superficielle du platine (pt) en regard de l'oxydation electrocatalytique du methanol. On etudie essentiellement les surfaces de type pt(n,n,n-2) (n est le nombre de rangees d'atomes) constituant la terrasse. Ces surfaces ont ete preparees et decontaminees par traitement thermique par la methode de j. Clavilier. Elles ont ete caracterisees par l'adsorption electrochimique de l'hydrogene. Les charges electriques des etats d'hydrogene sont conformes a celles deduites du modele de spheres dures de ces surfaces. On a etudie deux aspects de la reaction d'electrooxydation du methanol: formation du poison et oxydation directe. Le resultat le plus significatif montre que la reaction d'oxydation est sensible a la structure superficielle de l'electrode et que l'activite electrochimique reperee par la mesure de la densite de courant reste stable au cours des cycles successifs pour les surfaces avec n<9 alors qu'elle decroit pour les terrasses avec n>10. Nous avons confirme electrochimiquement que l'intermediaire poison pouvait etre une molecule de co bloquant en moyenne plus d'un site d'adsorption d'hydrogene ce qui correspondrait a l'existence d'un melange de molecules co lineairement et doublement liees a la surface des electrodes. L'etude de l'electrooxydation du methanol en presence d'adatomes d'etain sur le pt polyoriente et sur pt(111) a permis de montrer, selon le recouvrement en etain, une inhibition des deux reactions paralleles contrairement aux effets rapportes anterieurement avec l'etain, present dans la solution depose en sous-potentiel
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Brunat, William-Luc. "Cristallographie de surface par diffraction de photoélectrons de haute énergie cinétique (XPD) : CoSi2(111), Pt(110) et Pt50Ni50(110)." Lyon 1, 1992. http://www.theses.fr/1992LYO10188.
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La diffraction de photoelectrons de haute energie cinetique (xpd) constitue une sonde a la fois chimique comme l'esca dont elle derive et structurale comme toutes les techniques de diffraction. Cette methode d'analyse de surface a ete appliquee a 3 cas: l'analyse par xpd de cosi#2(111) a montre que le cristal, contrairement aux films minces de cosi#2 sur si(111), qu'une seule couche de silicium en surface. Ce resultat confirme l'hypothese de la migration du silicium en surface dans le cas des films minces; la face (110) du platine est consideree comme un modele de reconstruction (21) du type missing row. La comparaison des courbes experimentales avec des simulations effectuees pour 3 modeles possibles (missing row, vertical buckling et lateral pairing) a montre que la reconstruction est bien du type missing row et qu'elle est de plus accompagnee d'une contraction de 30% du plan de surface; l'etude par xpd de l'alliage pt#5#0ni#5#0(110) a permis de mettre en evidence une segregation du nickel a 75% dans le premier plan
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Aumer, Andreas. "Summenfrequenzerzeugungsspektroskopie an Metallen,Oxiden und oxidgeträgerten Metallpartikeln." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2010. http://dx.doi.org/10.18452/16158.
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Die vorliegende Arbeit widmet sich der Untersuchung von 4 Modellsystemen der Oberflächenforschung. Die verwendeten experimentellen Methoden sind Summenfrequenzerzeugungsspekroskopie (SFG), Thermische Desorptionsspektroskopie (TDS), Beugung niederenergetischer Elektronen (LEED), Augerelektronenspektroskopie (AES), Infrarotadsorptionsspektrokopie (IRAS) und Rastertunnelmikroskopie (STM). Durch die Verwendung von SFG waren Messungen bis zu 50 mbar möglich. Die untersuchten Systeme sind: CO auf Pt(111), Wasser auf Ag(001) und MgO/Ag(001), CO auf Au/MgO/Ag(001) und CO auf Au-Pd/MgO/Ag(001). Bei den Messungen von CO auf Pt(111) tritt unter bestimmten Druck- und Temperaturbedingungen eine bisher nicht näher untersuchte Doppelpeakstruktur auf, die genauer charakterisiert wurde. Die Untersuchungen von Wasser auf MgO/Ag(001) und Ag(001) zeigen, dass sich auf MgO/Ag(001) zuerst eine Monolage Wasser mit einer darauffolgenden Multilage ausbildet, wohingegen es auf Ag(001) von Beginn an in einer Multilagenschicht wächst. Die Monolage kann unter der Multilage gemessen werden und einige Resonanzen identifiziert werden. Für Au/MgO/Ag(001) zeigte sich mittels STM eine Abhängigkeit des Au-Wachstums von der Schichtdicke, die allerdings nicht spektroskopisch in Erscheinung tritt. Bei den Messungen an gemischten Au-Pd-Teilchen auf MgO/Ag(001) zeigen sich Unterschiede im Adsorptionsverhalten zwischen reinen Metallteilchen und gemischten Teilchen, die auf eine Wechselwirkung zwischen den beiden Metallen zurückzuführen ist. Nach Heizschritten auf 600 K reichern sich die Au-Atome im Mantel des Teilchens an, das Pd bildet den Kern. Die Ergebnisse aller Messungen werden unter Berücksichtigung neuer Veröffentlichungen diskutiert.This thesis focuses on 4 different model systems of surface science. The experimental techniques used for the measurements include sum frequency generation (SFG), thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), infrared adsorption spectrosocopy (IRAS) and scanning tunneling microscopy (STM). By using SFG, measurements could be performed up to a pressure of 50 mbar. The systems under investigation were: CO on Pt(111), water on Ag(001) and on MgO/Ag(001), CO on Au/MgO/Ag(001), and CO on Au-Pd/MgO/Ag(001). The system of CO on Pt(111) exhibits a two peak-pattern under certain pressure and temperature conditions which has not been studied so far. Various experiments helped to elucidate the origin of this distinct behaviour. The measurements of water on Ag(001) and MgO/Ag(001) show that on MgO, water first adsorbs as a monolayer with a following multilayer, whereas on Ag(001) it adsorbs as a multilayer from the beginning. The monolayer can be studied below the multilayer and some resonances can be identified. For the case of Au/MgO/Ag(001), STM shows that the growth mode of Au depends on the thickness of the supporting MgO film, which can not be seen with spectroscopic methods. For mixed Au-Pd particles on MgO/Ag(001) a clear difference in the adsorption behaviour between pure metal particles and mixed particles can be seen, which is explained by an interaction between these metals. Annealing the mixed particles to 600 K leads to a segregation of the metals, where the Au atoms diffuse to the shell and the Pd atoms make up the core. The results of all these measurements are discussed in the light of recent publications.
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Sachs, Christian. "Untersuchung von Reaktionsmechanismen auf Oberflächen mittels Rastertunnelmikroskopie: zur Wasserstoffoxidation auf den Oberflächen Platin(111) und Rhodium(111)." [S.l.] : [s.n.], 2001. http://www.diss.fu-berlin.de/2001/253/index.html.
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Niedermayer, Thomas Philipp. "Nichtthermische und thermische Desorption von Helium auf Pt(111)." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965396592.
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Battirola, Liliane Cristina. "Modificação de membranas de Nafion® 117 com nanopartículas de \'PT\' e \'PT\'-\'RU\' para aplicação em células a combustível." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-21072011-103643/.
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Além da necessidade do desenvolvimento de novos eletrocatalisadores para aplicação em células à combustível, há também a necessidade da diminuição do crossover, que compromete a eficiência da reação de oxidação do combustível. Sendo assim, foi realizada neste trabalho a dopagem das membranas de Nafion® 117 com nanopartículas de \'PT\' e \'PT\'/\'RU\', em duas concentrações diferentes de platina, pelo método de absorção-redução. Os resultados de Absorção Atômica e a coloração das amostras comprovaram a absorção da solução de precursores metálicos pela membrana. Os dados de FTIR-ATR e DRX mostraram que houve a formação de nanopartículas. Pelos testes em células unitárias (PEMFC, DMFC e DEFC), observou-se que tanto a PEMFC como a DEFC apresentaram uma melhora na eficiência. Apesar de ter havido um ganho significativo de densidade de potência, de até 50%, com membranas dopadas, não foi possível eliminar o crossover. Entretanto, no caso da DEFC, encontrou-se uma alta porcentagem de produtos oxidados com dois átomos de carbono na saída do cátodo. Os principais produtos formados foram acetaldeído e ácido acético, sendo que o ácido acético foi o produto majoritário. Também foram detectados traços de ácido fórmico comprovando que houve, em menor escala, a quebra da ligação C-C. Além disso, os resultados mostraram que a dopagem das membranas de Nafion® parece ter conferido uma melhora na durabilidade das amostras, já que estas, quando comparadas à membrana sem partículas metálicas, alcançaram maiores densidades de correntes. Finalmente, a dopagem da membrana e a elevação de temperatura provocaram um melhor desempenho nas DEFCs testadas.Beyond the necessity of the development of new electrocatalysts for fuel cell application, there is also the necessity of diminishing of the crossover that compromises the oxidation efficiency of the fuel. So, in this work was carried out the doping of the Nafion® 117 membranes with \'PT\' and \'PT\'/\'RU\' nanoparticles in two different platinum concentrations by using the absorption-reduction method. The Atomic Absorption results and the color of the samples proved that the absorption of the metallic precursor solutions by the membrane happened. FTIR-ATR and XRD data showed the formation of nanoparticles. It was observed that in unitary fuel cells (PEMFC, DMFC and DEFC) tests the PEMFC and DEFC showed an improvement in the efficiency. Although a significant increase in the power density, up to 50 % by using doped membranes, it was not possible to eliminate the crossover. However, in the case of the DEFC, a high percentage of oxidized products with two carbon atoms was found in the cathode exit. The main formed products were acetaldehyde and acetic acid, being the acetic acid the majority product. Traces of formic was also detected demonstrating that, in lesser scale, the break of the C-C bond is feasible. Moreover, the results showed that the durability of the doped Nafion® membranes is higher than the membrane without metallic particles, since bigger current densities were reached in the former case. Finally, the membrane doping and the temperature rise led the DEFC to the best performance.
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Paulino, Marcia Elizangela. "\"Estudo da reação de eletro-oxidação de metanol sobre eletrodos monocristalinos de platina modificados com eletrodepósitos de cobre e estanho\"." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-12042007-094545/.
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A eletro-oxidação de metanol foi estudada em eletrodos de platina monocristalina de índices de Miller (100) e (111) modificados superficialmente com metais cobre e estanho nas condições de UPD (Underpotential Deposition) e OPD (Overpotential Deposition). Os experimentos foram conduzidos em EDRMP (Eletrodo de Disco Rotatório com Menisco Pendente) em conjunto com as técnicas eletroquímicas. Os depósitos de cobre foram realizados em condições de UPD e OPD enquanto que estanho em OPD, dada as limitações de rearranjo estrutural da superfície cristalográfica do eletrodo. As análises dos resultados indicaram que o grau de recobrimento dos metais sobre o suporte é menor que uma monocamada, cerca de 10% desta. Tais resultados comparados com a literatura indicam a formação de aglomerados, ilhas, em estruturas bi e tridimensionais no caso do cobre. Em estanho foi atingido maior grau de recobrimento. No entanto, comparando os resultados para estanho com o da literatura, este não se depositou na forma de adátomos, mas como hidróxido ou sulfato. Esta forma de interação do estanho com a platina é a responsável pela diminuição do potencial de oxidação do metanol sobre o substrato. Na eletro-oxidação do metanol os melhores resultados foram obtidos na presença de estanho, no entanto ressalta-se que neste caso a influência da rotação não foi significante e as medidas de cronoamperometria indicaram melhor atividade nesta situação com o eletrodo modificado.Methanol oxidation reaction was studied with copper and tin modified single-crystal electrodes. This study was carried out using UPD and OPD techniques using the EDRMP configurations the results showed that the coverage degree of copper and tin on platinum single-crystal as less than one monolayer (_ 10% monolayer) and possible with the formation of islands in bi and tridimenision. The deposition of copper was not good to the methanol oxidation reaction, possible due to a higher solvatation by anions at the Cu sites, conducting to a blocking effect on the Pt neighboring atoms. The tin deposition have shown a higher activity for methanol oxidation reaction. This ascribed to the hydroxides formation at tin sites, which increase the kinetics of CO oxidation following the bifunctional mechanism.
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Robinson, Andrew William. "Adsorption on platinum (110) : reflection-absorption infra-red studies." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379555.
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Grant, Ann W. "Surface studies of model catalysts using metal atoms and particles on ZnO(0001)-Zn and -O and TiO₂(110) /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/8499.
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Völkening, Stephan. "Untersuchungen von Reaktionsmechanismen auf Oberflächen mittels Rastertunnelmikroskopie die atomar aufgelösten Oxidationsreaktionen von Kohlenmonoxid und Wasserstoff auf Platin(111) /." [S.l. : s.n.], 1999. http://www.diss.fu-berlin.de/1999/10/index.html.
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Beccat, Pierre. "Structure et composition superficielles de l'alliage Pt80Fe20(111) en liaison avec ses propriétés catalytiques." Grenoble 1, 1990. http://www.theses.fr/1990GRE10043.
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Des mesures de reactivite sur des particules ptfe/c ont montre que, pour 80% de platine, la vitesse d'hydrogenation du cinnamaldehyde est maximum. Afin de supprimer le role eventuel du support, du solvant, et les facettes complexes des petites particules, nous avons a la fois, dans ce travail de these, mesure les proprietes catalytiques de l'alliage monocristallin pt#8#0fe#2#0(111) lors de l'hydrogenation du crotonaldehyde et du methylcrotonaldehyde, et nous avons determine avec precision la structure et la composition de la surface par diffraction d'electrons lents et spectroscopie auger. Les resultats sont les suivants: le premier plan atomique est un plan pur de platine et le profil de composition est monotone: c#1=96%pt, c#2=88, c#3=85. De plus, dans le plan de surface, un atome sur les quatre composants la maille elementaire est deplace hors du plan de 0,1 a. Des mesures de reactivite, on peut conclure que l'addition de fer provoque une augmentation notable d'activite et que la presence d'un groupement methyl supplementaire dans le methylcrotonaldehyde induit une augmentation importante de la selectivite en alcool insature. D'apres des mesures de spectroscopie de pertes d'energie electronique et des previsions theoriques, la molecule est liee a la fois par les fonctions c=c et c=o. L'addition du groupement methyl provoquerait l'abaissement de l'interaction c=c/pt, entrainant l'apparition de selectivite en alcool insature. La presence du fer dans le deuxieme plan atomique peut modifier les proprietes electroniques des atomes de pt du premier plan, modifications a l'origine de l'augmentation d'activite
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Moré, Sam Dylan. "Untersuchungen von Adsorbaten auf Einkristalloberflächen mittels Beugung niederenergetischer Elektronen Koadsorption von K und CO auf Pt(111) ; Li, Na, K auf Pt111) ; N auf Cu(110) sowie Untersuchungen von der reinen Ga(001)-Oberfläche /." [S.l. : s.n.], 1998. http://www.diss.fu-berlin.de/1998/14/index.html.
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Blais, Sonia. "Étude du comportement électrochimique de couches inorganiques ultra-fines sur l'électrode de platine (111)." Sherbrooke : Université de Sherbrooke, 2000.
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Berner, Ulrich. "Struktur und Reaktivität ultradünner Ceroxidschichten auf Pt(111)-Einkristalloberflächen Untersuchungen mit Rastertunnelmikroskopie, Photoemission und IR-Reflexions-Absorptions-Spektroskopie /." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964801884.
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Ostermann, Dieter. "STM-, XPS-, LEED- und ISS-Untersuchungen an reinen und Pd-bedeckten ultradünnen Titanoxidschichten auf Pt(111)." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97774292X.
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Röder, Holger. "Microscopic processes in heteroepitaxial growth : nucleation, growth and alloying of silver on the (111) surface of platinium /." [S.l.] : [s.n.], 1994. http://library.epfl.ch/theses/?nr=1288.
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Peronio, Angelo. "A closer look at heterogeneous catalysis: reaction intermediates at the single-molecule level." Doctoral thesis, Università degli studi di Trieste, 2013. http://hdl.handle.net/10077/8577.
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2011/2012The present work pertains to the surface science approach to heterogeneous catalysis. In particular model systems for CO2 hydrogenation to methanol, and NO selective catalytic reduction, are investigated by means of a combined approach, where the molecular-level insight provided by a low-temperature scanning tunneling microscope is complemented by density functional theory (DFT) calculations of their electronic structure. To this end, the Inelastic Electron Tunneling Spectroscopy (STM-IETS) technique was introduced for the first time in our laboratory, a recent development which allows to measure the vibrational spectrum of individual molecules adsorbed on a surface. Regarding CO2, we provide single molecule imaging and characterization of CO2/Ni(110), chemisorbed with high charge transfer from the substrate, in an activated state that plays a crucial role in the hydrogenation process. We obtain a detailed characterization of the adsorption geometries and an estimate of the energies corresponding to the different adsorbed states. A consistent picture of CO2 chemisorption on Ni(110) is provided on the basis of the newly available information, yielding a deeper insight into the previously existing spectroscopic and theoretical data. In the Selective Catalytic Reduction (SCR) process, nitrogen oxide is selectively transformed to N2 by reductants such as ammonia. The specificity of this reaction was tentatively attributed to the formation of NH3-NO coadsorption complexes, as indicated by several surface science techniques. Here we characterize the NH3-NO complex at the atomic scale on the (111) surface of platinum, investigating the intermolecular interactions that tune the selectivity. The structures that arise upon coadsorption of NH3 and NO are analyzed in terms of adsorption sites, geometry, energetics and charge rearrangement. An ordered 2 × 2 adlayer forms, where the two molecules are arranged in a configuration that maximizes mutual interactions. In this structure, NH3 adsorbs on top and NO on fcc-hollow sites, leading to a cohesional stabilization of the extended layer by 0.29 eV/unit cell. The calculated vibrational energies of the individually-adsorbed species and of the coadsorption structure fit the experimental values found in literature within less than 6%. The characterizations and optimizations that had to be tackled in order to successfully perform STM-IETS measurement are eventually presented, focusing in particular on an original method which allows to increase the achieved resolution. Namely, the modulation broadening associated to phase-sensitive detection is reduced by employing a tailored modulation function, different from the commonly-used sinusoid. This method is not limited to STM-IETS, but can be easily applied whenever a lock-in amplifier is used to measure a second derivative.
XXV Ciclo
1984
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THIELE, JORG. "Structure et proprietes magnetiques de couches minces de cobalt sur la face (111) du platine." Paris 11, 1995. http://www.theses.fr/1995PA112292.
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Cette these presente une etude des films ultra mince de cobalt co evapores a temperature ambiante sur la face (111) de platine pt par spectroscopie des niveaux de cur, spectroscopie auger aes, diffraction des electrons lents del, des experiences de extended x-ray absorption fine structure sur le seuil k de co, et par dichroisme circulaire magnetique dcm en absorption sur les seuils l#2#,#3 du co. L'ensemble des caracterisations montre que le co croit de maniere bien ordonnee avec des distances interatomiques proches de celles observees dans le cobalt massif, malgre une grande difference du parametre de maille entre le substrat pt et le co 10%. L'interface co/pt(111) montre seulement une tres faible interdiffusion. Parallelement, il a ete observe, que le depot d'une couche supplementaire du pt sur un depot de co n'induit pas de changement dans le co. Le depouillement des spectres de photoemission montre que l'interface pt/co ainsi formee est moins abrupte que celle entre le co et le substrat pt monocristallin. Du cote des proprietes magnetiques des couches minces de co, l'etude en dcm met en evidence que les couches de co non recouvertes par du pt possedent une forte anisotropie perpendiculaire a la surface. En relation avec la caracterisation de la structure des couches minces du co/pt(111), il est ainsi possible de cerner l'origine de cette anisotropie, car ni la formation d'une alliage a l'interface ni des contraintes induites par la difference de parametre de maille entre pt et co n'ont ete observes. C'est donc une variation de la structure electronique par hybridation a l'interface co/pt(111) qui est le facteur determinant pour l'explication de l'anisotropie. L'etude de l'influence des recuits sur les films de co non recouverts montre la possibilite d'une formation d'alliages de surface magnetiques possedant une anisotropie perpendiculaire a la surface
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Donev, Jason Matthew Kaiser. "Non-contact atomic force microscopy studies of amorphous solid water deposited on Au(111) /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9779.
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Pollmann, Michael. "Musterbildung bei der CO-Oxidation auf Pt(110) unter gezielter Beeinflussung." [S.l.] : [s.n.], 2002. http://www.diss.fu-berlin.de/2002/71/index.html.
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Folkuenig, Engelbert de Souza. "Investigação teórica da quimisssorção do ânion metanossulfonato em eletrodos de platina (111) e (100) via método semi-empírico." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2010. http://tede2.uepg.br/jspui/handle/prefix/2085.
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Previous issue date: 2010-05-10Several electrochemical processes, such as electrocatalysis of organic substrates, make use of mediators. One of the mediators is the most commonly used anion methanesulfonate, CH3SO3, which has several advantages for such use, and chemical stability considered one of them. However, experimental studies indicate the possibility of this compound suffer the adsorption and decomposition on platinum electrodes. To get an understanding at the molecular level these processes, computer simulations were performed with the aid of the semi-empirical PM6. The cluster approach was used in the modeling of platinum surfaces with crystallographic orientations (111) and (100). The symmetries of most stable adsorption calculated for the anion in these areas correspond to the experimental data: C3V symmetry in (111) surface and C1 in (100) surface. To simulate the potential applied to the electrode, external electric fields with a positive sign and perpendicular to the surface of the clusters were applied. Changes in the lengths and angles of bonds adsorbed anion, as well as its values of dipole moment were observed. The infrared spectra of the systems anion-clusters were calculated and the values for the Stark tunning rate (Δstark) of mode δs CH3 were compared with the experimental value. Both for the free anion and for systems where the anion is adsorbed, it was found that the values of Δstark assumed negative values (indicating that the frequency of the vibrational mode δs CH3 diminished with increasing external eletric field), opposite to the experimental positive value (frequency mode δs CH3 increases with the increase in potential). Only with the addition of water molecules in the systems studied, in order to simulate the aqueous solvent is that the values of Δstark started to assume a positive value. The comparison showed the importance of the presence of water molecules in the simulation of an electrochemical system and prompted a detailed analysis of the frontier orbitals involved in this process. It was found that the dipole-dipole coupling between water molecules and the adsorbed anion is responsible for the Stark effect, while the electrostatic interactions between various molecules adsorbed anion affect the intensity of the absorption band mode δs CH3 in the spectra calculated. In (100) surfaces, the joint action of external field and water molecules, lead the anion molecule to adopt the adsorption geometries more inclined to systems without water molecules, indicating that this may be an important factor in explaining the greater reactivity of the anion on the surface.
Vários processos eletroquímicos, como por exemplo a eletrocatálise de substratos orgânicos, fazem uso de mediadores. Um dos mediadores mais utilizados é o ânion metanossulfonato, CH3SO3¯, que apresenta várias vantagens para tal uso, sendo a estabilidade química considerada uma delas. No entanto, estudos experimentais apontam para a possibilidade desse ânion sofrer processos de adsorção e decomposição em eletrodos de platina. Para se obter uma compreensão em nível molecular desses processos, simulações computacionais foram efetuadas com auxílio do método semi-empírico PM6. A aproximação de cluster foi utilizada na modelagem de superfícies de platina com orientações cristalográficas (111) e (100). As simetrias de adsorção mais estáveis calculadas para o ânion nessas superfícies correspondem aos dados experimentais: simetria C3v em superfície (111) e C1 em superfície (100). Para simular o potencial aplicado ao eletrodo, campos elétricos externos de sinal positivo e perpendiculares à superfície dos clusters foram aplicados. Alterações nos comprimentos e ângulos de ligações do ânion adsorvido, bem como em seus valores de momento dipolar foram observados. Os espectros de infravermelho dos sistemas ânion-clusters foram calculados e os valores para a taxa de variação Stark (Δstark) do modo δs CH3 foram comparados com o valor experimental. Tanto para o ânion livre quanto para os sistemas onde o ânion se encontra adsorvido, verificou-se que os valores de Δstark assumiam valores negativos (indicando que a frequência vibracional do modo δs CH3 diminuía com o aumento da intensidade do campo externo), ao contrário do valor experimental, positivo (frequência do modo δs CH3 aumenta com o aumento do potencial). Apenas com a adição de moléculas de água aos sistemas estudados, de modo a simular o solvente aquoso, é que os valores de Δstark passaram a assumir um valor positivo. Essa comparação revelou a importância da presença de moléculas de água na simulação de um sistema eletroquímico e motivou uma análise pormenorizada dos orbitais de fronteira envolvidos nesse processo. Verificou-se que a interação dipolo-dipolo entre as moléculas de água e o ânion adsorvido é o responsável pelo efeito Stark, enquanto as interações eletrostáticas entre várias moléculas do ânion adsorvidas afetam a intensidade da banda de absorção do modo δs CH3 nos espectros calculados. Nas superfícies (100), a ação conjunta do campo externo e das moléculas de água, levam a molécula do ânion a adotar geometrias de adsorção mais inclinadas em relação aos sistemas sem as moléculas de água, indicando que este pode ser um fator importante para explicar a maior reatividade do ânion sobre esse tipo de superfície.
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Radovic, Zorana. "Étude du comportement électrochimique du monoxyde de carbone chimisorbé sur les électrodes platine(hkl) et étude de la déposition sous-nernstienne de l'argent et du cuivre sur l'électrode platine(111)." Sherbrooke : Université de Sherbrooke, 2001.
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Wolff, Janpeter. "Lokale Kontrolle der Musterbildung bei der CO-Oxidation auf einer Pt(110)-Oberfläche." [S.l. : s.n.], 2002. http://www.diss.fu-berlin.de/2003/13/index.html.
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ZAMAKCHARI, MOHAMED AZZEDDINE. "Etude des surfaces monocristallines de platine ptn(111)x(100) en vue de l'oxydation electrocatalytique du methanol en milieu acide." Paris 6, 1993. http://www.theses.fr/1993PA066280.
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L'adsorption-desorption electrochimique de l'hydrogene sur platine est un processus sensible a la structure cristalline de la surface. Dans le but de l'identification de la contribution des sites introduits deliberement sur la surface, on a entame l'etude voltammetrique d'une serie de surfaces a marches de platine ptn(111)x(100) (autre notation pt (n+1, n-1, n-1). La charge electrique correspondant aux differents etats d'adsorption d'hydrogene est associee a la densite de chaque type de site. La charge de l'etat qui se developpe quand la largeur de terrasse diminue correspond a la charge des sites de marche. Le reste de la charge contient la contribution des sites de terrasse plus la double couche. On sait que l'oxydation du methanol sur des surfaces monocristallines de platine se fait suivant deux voies. Les deux voies ont ete etudiees dans ce travail sur la serie de surface caracterisee dans la premiere partie. L'intermediaire poison i. P, provenant de l'adsorption dissociative du methanol, a ete isole et etudie. D'apres les resultats obtenus, on a pu determiner le recouvrement en i. P et obtenir des informations sur le mode de liaison de co avec les sites de chaque surface. L'oxydation directe du methanol est une reaction de surface sensible a la structure superficielle du platine. Les resultats obtenus avec les surfaces monocristallines a marches font apparaitre les contributions caracteristiques observees avec les plans de base. La vitesse d'oxydation augmente avec la concentration du reactif dans le domaine etudie (1,5 m). Les deux voies de cette reaction confirmees par l'etude de l'effet d'especes coadsorbees comme les anions (h#2so#4 et clo#-#4) nous ont permis d'aboutir au choix de l'electrocatalyseur de platine pour le developpement de la reaction electrocatalytique
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Bocquet, Marie-Laure. "Interpretation d'images obtenues par microscopie à effet tunnel (STM) de petites molécules isolées, adsorbées sur une surface 111 de platine." Lyon, École normale supérieure (sciences), 1996. http://www.theses.fr/1996ENSL0021.
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Les travaux presentes ici concernent l'elucidation theorique d'images stm a l'echelle atomique, en particulier celles de molecules isolees adsorbees sur une surface de platine, comme le benzene, le monoxyde de carbone et l'oxygene. Tout d'abord, un code existant de simulation appele esqc-stm a ete utilise. Outre une reproduction semi-quantitative des images experimentales du benzene et du monoxyde de carbone, notre travail a permis de proposer une interpretation chimique de l'origine des differents contrastes moleculaires. En effet, nous avons developpe cet outil theorique en introduisant une decomposition orbitalaire du courant calcule. Ainsi, nous avons montre que l'aspect stm d'une molecule adsorbee resulte d'abord d'une competition avec effet d'interference, entre deux contributions au courant tunnel: celle des orbitales de la molecule et celle des orbitales du substrat metallique en interaction avec l'adsorbat. De cette competition depend crucialement le relief global de la molecule imagee (protuberance ou depression). De plus, les decompositions du courant via la molecule, ont prouve que les orbitales moleculaires significatives pour la conduction tunnel ne sont pas necessairement les orbitales frontieres proches du niveau de conduction du metal. En effet, la geometrie d'adsorption de la molecule et la force de l'interaction adsorbat-substrat restreignent la selection aux orbitales convenablement orientees pour pouvoir bien interagir a la fois avec la surface et avec la pointe. Enfin, nous avons trouve que les modes de recombinaison de ces contributions individuelles au courant dependent aussi singulierement de la position de la molecule relativement a la surface (sites) et se schematisent, a l'aide d'un modele analytique simple, en interferences destructives entre les orbitales sigma et pi. Nous avons donc pu interprete et justifie la multiplicite des contrastes obtenus, en observant avec le microscope le benzene ou le monoxyde de carbone sur differents sites d'adsorption
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RADOSAVKIC, DENIS. "Etude de la structure atomique et electronique de surfaces (111) mixtes platine-palladium et effet de la chimisorption du monoxyde de carbone." Paris 11, 1998. http://www.theses.fr/1998PA112040.
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Ma these a porte sur l'etude et la caracterisation au niveau atomique de surfaces mixtes platine-palladium, principalement par photoemission des niveaux de cur 4f#7#/#2 du pt et des bandes de valence sous rayonnement synchrotron (lure). D'abord, les surfaces d'alliages monocristallins pt#xpd#(#1#-#x#)(111) avec x = 0,1 ; 0,5 ; 0,9 ont ete etudiees. Ensuite, la croissance du pt/pd(111) a temperature ambiante a ete caracterisee par photoemission et par diffraction d'atomes d'helium neutres. Une fois ces surfaces caracterisees, nous avons effectue des adsorptions de monoxyde de carbone pour determiner l'effet d'une chimisorption de co sur une surface ptpd. Pour les surfaces d'alliages (111), la determination des concentrations par plans a permis de montrer la segregation naturelle du pd en surface, ainsi que l'enrichissement en pt du plan sous-jacent. Ces concentrations confirment les profils de segregation calcules. Lors de la croissance du pt/pd(111) a temperature ambiante, une zone d'interdiffusion limitee au premier plan de surface se forme pendant le depot de la premiere monocouche puis est progressivement detruite. Elle conduit a la formation d'une interface abrupte a 2 mc de pt deposees. Les adsorptions de co, effectuees sur ces surfaces ptpd, entrainent une modification importante de la concentration en pt du plan de surface. Nous avons mis en evidence une segregation non thermique du pt provoquee par la chimisorption du co.
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Croci, Mirko. "Chimisorption et diffusion de surface du monoxyde de carbone et chimisorption du monoxyde d'azote sur le platine (111) : étude par jet d'hélium thermique /." [S.l.] : [s.n.], 1992. http://library.epfl.ch/theses/?display=detail&nr=1100.
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Fleming, Thomas P. "Medium energy ion scattering investigation of the structures formed by deposition of sub-monolayer platinum group metals on the copper(110) surface." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/9329.
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This thesis reports a medium energy ion scattering investigation (MEIS) of platinum, palladium, and rhodium deposited upon the copper (110) surface using 100 keV hydrogen ions. The Daresbury National MEIS facility was used to take blocking curve and energy profiles of the structure formed by e-beam deposition of various thicknesses of platinum, palladium, and rhodium upon an atomically clean and ordered copper (110) crystal face. Quantitative analysis was conducted using an in-house version of the IGOR macro widely used within the MEIS community, adapted to analyse these systems. Sub-monolayer deposits of palladium and platinum were found to preferentially occupy subsurface sites, predominantly in the second layer below a copper first layer. This process occurred at room temperature. The interlayer separation between the deposited species and first layer copper were found in all three cases, being 1.21±0.04 Å for platinum, 1.17±0.06 Å for palladium and 1.16±0.06 Å for rhodium. These are contractions when compared to bulk interlayer spacing for copper which is 1.278 Å but are comparable to the first interlayer spacing from literature for relaxed copper which is 1.18 Å. A c(2x2) LEED pattern was observed in the case of the 0.3 ML platinum deposit which is an interesting comparison to the (1x2) reconstruction observed for sub-monolayer palladium in some literature sources. Upon annealing, the deposited species were observed to occupy third and fourth layer sites despite the temperature not being sufficient for diffusion deeper into the copper substrate. A process of burying through substrate adatom diffusion upward onto step edges is suggested as an energetically favoured process.
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Fernandes, Gomes Janaina. "Etude de l'adsorption et électro-oxydation de l'éthanol sur électrodes de platine par spectroscopie de génération de la fréquence somme." Paris 11, 2007. http://www.theses.fr/2007PA112222.
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L'application de l’éthanol comme combustible pour les piles à combustible directes d’alcool continue à motiver la recherche sur les mécanismes de l’électro-oxydation de l’éthanol. Dans ce travail, l’interface éthanol-platine en milieu acide est étudiée par la spectroscopie SFG infrarouge–visible afin de documenter les intermédiaires de l’électro-oxydation de l’éthanol. De nouvelles évidences sur les intermédiaires adsorbés de l’oxydation de l’éthanol sur le platine, jamais observés auparavant avec la spectroscopie infrarouge, sont rapportées. Nos résultats montrent qu’un dérivé de l’éthanol secondaire, précédemment suggéré, mais jamais documenté précédemment, et des espèces acétate mono et bidentée, eta2-acetaldehyde, acétyle et un dérivé d’acide acétique moléculaire sont les intermédiaires actifs de l’oxydation de l’éthanol en milieu acide. De plus, nous rapportons de nouvelles évidences pour la présence d’un intermédiaire d’ethoxy. Les résultats obtenus confirment également la présence des intermédiaires précédemment observées de l’oxydation de l’éthanol: CO adsorbé et un dérivé d’éthanol tertiaire. D’autre part, nous avons exploité les effets de la structure atomique de l’électrode, de la concentration de l’alcool et du potentiel de l’électrode sur le mécanisme de l’adsorption et de l’électro-oxydation de l’éthanol sur le platine. Ces effets sont analysés par les spectres vibrationnels des intermédiaires adsorbés. La comparaison avec l’adsorption d’autres réactifs simples (méthanol, acétaldéhyde, acide acétique) en milieu acide indique que, même à bas potentiel, la surface de platine est très réactive, produisant des intermédiaires semblables pour tous les réactifsThe possible application of ethanol as a fuel for direct alcohol fuel cells continues to motivate research on the mechanisms of electro-oxidation of ethanol. In this work, the ethanol-platinum interface in acidic medium is investigated using infrared-visible SFG spectroscopy in order to document the intermediates present during the electro-oxidation of ethanol. New evidences of adsorbed intermediates of ethanol oxidation on platinum, never before observed with conventional IR spectroscopy, are reported. Our results show that a secondary ethanol derivative, previously suggested, but never before unambiguously documented, and mono and bidentate acetate, eta2-acetaldehyde, acetyl and a molecular acetic acid derivative are active intermediates of ethanol oxidation in acidic medium. In addition, we report new evidences for the presence of an ethoxy intermediate. The results obtained here also confirm the presence of previously observed ethanol oxidation intermediates: adsorbed CO and a tertiary ethanol derivative. Moreover, we explored the effects of the atomic surface structure of the electrode, alcohol concentration and electrode potential on the mechanism of the adsorption and electro-oxidation of ethanol on platinum. These effects are analyzed through the vibrational spectra of interfacial adsorbed intermediates. Comparison with the adsorption of other simple reactants (methanol, acetaldehyde and acetic acid) in acid medium indicate that even at low potential the platinum surface is highly reactive, producing similar intermediates for all reactants
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Barolo, Andrea. "Studio di catalizzatori a base di film sottili di ossidi metallici di transizione su substrato metallico monocristallino." Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3427523.
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This work discuss thin solid films of transition metal oxides on crystalline metal substrate morpholgy and reactivity toward gases. In particular the systems analyzed are: CoO on Pd(100), SnO on Pt(110) and NiO on Pd(100).Questo lavoro discute in proposito di film sottili di ossidi di metalli di transizione su substrato metallico cristallino in riferimento alla loro morfologia e reattività verso i gas. In particolare i sistemi analizzati sono CoO su Pd(100), SnO su Pt(110) and NiO su Pd(100).
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Behafarid, Farzad. "Structure, stability, vibrational, thermodynamic, and catalytic properties of metal nanostructures: size, shape, support, and adsorbate effects." Doctoral diss., University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5121.
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Recent advances in nanoscience and nanotechnology have provided the scientific community with exciting new opportunities to rationally design and fabricate materials at the nanometer scale with drastically different properties as compared to their bulk counterparts. In this dissertation, several challenges have been tackled in aspects related to nanoparticle (NP) synthesis and characterization, allowing us to make homogenous, size- and shape-selected NPs via the use of colloidal chemistry, and to gain in depth understanding of their distinct physical and chemical properties via the synergistic use of a variety of ex situ, in situ, and operando experimental tools. A variety of phenomena relevant to nanosized materials were investigated, including the role of the NP size and shape in the thermodynamic and electronic properties of NPs, their thermal stability, NP-support interactions, coarsening phenomena, and the evolution of the NP structure and chemical state under different environments and reaction conditions.Ph.D.
Doctorate
Physics
Sciences
Physics
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Po-Chun, Kuo, and 郭博駿. "Platinum Formation on Si(111)-7x7 Surface." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/4z2e4r.
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碩士國立中興大學
物理學系所
103
The Formation of metal silicide has attracted much attention because of its low resistivity and ohmic contact in semiconductor devices. As semiconductor device get smaller, the size effect becomes more and more important. The effect of size variation in nanoscale has also led to various physical in materials. In this work, the effect of deposited time on the structure and electronic property of platinum atoms deposited on silicon (111) surface are investigated by thermal evaporation .UHV-STM was used to check the surface morphology, the results show that the platinum atoms is self-assembled as a atomic chain with irregular arrangement the results show that on the surface. In the following, the sample was annealed at high temperature, low evaporation amount of the sample rearrange to the irregular atomic long-chain structure with [1 ̅1 ̅2] direction, and which the high amount of sample deposition will form a large island structure covers the surface. We infer that the difference between the two results, is caused by different deposited amount, the attraction between the platinum atoms and the substrate surface are affected. Finally, by use STS measurements, measuring the dI / dV curve, and to explore the relationship between the energy gap and the surface structure. The original 7 × 7 reconstructed surface energy gap of 1.17eV, disorder region is 0.97eV, and long chain structure significantly improves band gap becomes 1.68eV, and a large island structure is reduced to 1.04eV.
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Tu, Hsun-Ta, and 杜訓達. "Dynamical Investigation of Platinum Atoms on Si(111)-7x7 surface." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35123511389318567329.
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碩士國立中興大學
物理學系所
97
The adsorption and the dynamics of platinum atoms on the Si(111)-7x7 surface were studied by using a ultra high vacuum scanning tunneling microscope .It covered high coverage and low coverage experiments . In low coverage experiment ,it covered room temperature and high temperature experiments . We conferred the adsorption site of single platinum atom and inferred the hopping path of single platinum atom by using profile to analyze in room temperature experiment. We took down the time of single platinum stay in half unit cells to get the activation energy and pre-ponential factor for the platinum atoms crossing the cell boundary by Arrhenius plot. The activation energy are Ea(F→U)= 0.77±0.09eV and Ea(U→F)= 0.62±0.04eV,respectively. The pre-ponential factor are Ro(F→U)=109.85±2.73Hz and Ro(U→F)=108.77±0.54Hz,respectively. When the temperature increase to 350K,platinum atoms and silicon surface found to form a new adsorption site. When the temperature up to 360K,single platinum atom hopping could not be found any more and only the new adoption site. In high coverage experiment, we found the island structure of platinum atoms and silicon atoms. The structure were Pt silicide island(6.28x6.28).
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Yang, Chou-Min, and 楊朝閔. "Direct Observation of Single Platinum Atomson Si(111)-7x7 Surface." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/46947098141122771541.
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碩士中興大學
物理學系所
95
The dynamics and the adsorption of single platinum atoms on Si(111) - 7x7 were studied by a variable temperature ultrahigh vacuum scanning tunneling microscope. The thesis divides parts: room temperature(RT) study and high Temperature(HT) study. (1)RT experiment: we observed the dynamics and the adsorption of single platinum atoms at room temperature and use profile to analyze the interaction between single platinum atoms, corner adatoms, rest atoms and center atoms. We proposed the hopping paths for platinum atoms hopping within a half unit cell, compared with silver atoms.[7] (2)HT experiment: Activation energy and pre-exponential factor for platinum atoms crossing the cell boundary were estimated by Arrhenius plot. They are 1.08±0.12eV，1015.26±1.87Hz for platinum atoms jumping out of faulted half unit cells(FHUCs); and，0.61±0.08eV，108.79±1.18Hz for platinum atoms jumping out of unfaulted half unit cells(UFHUCs) respectively. Because Ea(F->uF) is bigger than Ea(UF->F) ,the time platinum atoms staying in FHUCs should be longer than in UFHUCs. When the temperature increase to 332K, platinum atoms and silicon found to form a new stable adsorption pieces. They looked like clusters. The formation of new stable site could be Pt2Si or PtSi[2]. At temperature up to 340K, only new adsorption pieces were found on surfaces.
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Hoheisel, Martin. "Oxygen and CO on the Pt3Sn(111) and Pt3Sn(110) surfaces." Doctoral thesis, 2002. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2002111520.
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The high temperature adsorption of oxygen and the room temperature adsorption of CO on the Pt3Sn(111) and Pt3Sn(110) surfaces have been investigated by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). Beforehand the structure of the clean surfaces has been reviewed.
After exposure to several 1000 L O2 at sample temperatures of about 750 K on both Pt3Sn(111) and (110) an ultra-thin Sn-O surface layer is formed. For the (111) X-ray photoelectron spectroscopy (XPS) indicates that this layer does not yet exhibit oxide properties. STM topographs of the Sn-O phase show on both surfaces meshes of highly corrugated protrusions commensurate with the substrate. In the case of the (111), after additional thermal annealing with STM and LEED a (4 × 4) reconstruction is observed, that is due to a (2 × 2) supermesh of depressions in the p(2 × 2) mesh of protrusions. This structure is similar to findings reported for the oxidation of Sn/Pt(111) surface alloys. X-ray photoelectron diffraction (XPD) measurements in comparison with simulations yield a tentative model for the (111) Sn-O layer.
On the Pt3Sn(110) surface after oxygen exposure a c(2 × 2) hexagonal grid of protrusions with regard to the (2 × 1) substrate is observed with STM and LEED. STM reveals the existence of domains due to two equivalent positions of the Sn-O layer relative to the substrate. The domain boundaries zigzag around the [1-10] direction. The Sn-O layer can on both surfaces be removed by thermal annealing to more than 1050 K.
After CO adsorption at room temperature on both Pt3Sn(111) and (110) adsorbate structures are observable with the STM. On the (111) two different types of structures are found: ordered patches of protrusions and unordered clusters. These structures are seen only on (√3 × √3)R30° substrate regions, not on p(2 × 2) regions. Surprisingly on the (110) the CO molecules mostly arrange in dimers. For both (111) and (110) saturation coverage is already reached at about 30% of a closed monolayer. The CO can be desorbed by slightly heating the samples to about 400 K. STM topographs show that on both surfaces CO adsorbes in Pt sites, not on Sn.
It was possible to observe the CO adsorption on the (110) directly live with the STM. The observed adsorption processes hint to a dimer formation mechanism where a preadsorbed monomer and a CO molecule form the gas phase or a precursor phase stick together.
When on partially Sn-O phase covered Pt3Sn(111) and (110) surfaces CO is adsorbed at room temperature, the respective structures coexist. Neither is CO observed on the Sn-O phase nor does a reaction between CO and O occur.
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"Hyperchanneling of low energy ions on the platinum(111) and gold(110) surfaces and ion scattering spectrometry of ferroelectric lithium tantalate." 2002. http://library.cuhk.edu.hk/record=b6073461.
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"May 2002."Thesis (Ph.D.)--Chinese University of Hong Kong, 2002.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.
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Kim, Yong-ju. "The growth of epitaxial iron oxides on platinum (111) as studied by x-ray photoelectron diffraction, scanning tunneling microscopy, and low energy electron diffraction." Thesis, 1995. http://hdl.handle.net/10125/9524.
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Cummins, Kyle. "Interfacial Properties of Ultrathin- Film Metal Electrodes: Studies by Combined Electron Spectroscopy and Electrochemistry." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-05-11199.
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A pair of studies investigating the deposition and surface chemical properties of ultrathin metal films were pursued: (i) Pt-Co alloys on Mo(110); and (ii) Pd on Pt(111). Experimental measurement was based on a combination of electron spectroscopy (low energy ion scattering spectroscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, and low energy electron diffraction) and electrochemistry (voltage efficiency, voltammetry, and coulometry).
Mixed-metal preparation of Pt-Co films by thermal vapor deposition (TVD) resulted in a thin-film binary alloy. Careful analysis revealed a substantial divergence between the composition at the interface and that in the interior. This outcome was observed for all compositions and allowed for the construction of a ?surface phase diagram?. The proclivities of the alloys of pre-selected compositions towards enhanced catalysis of the oxygen-reduction reaction were assessed in terms of their voltage efficiencies, as manifested by the open-circuit potential (OCP) in O2-saturated dilute sulfuric acid electrolyte. The particular alloy surface, Pt3Co (XPt=3,XCo=1), whether from the thin film or a bulk single crystal, exhibited the highest OCP, a significant improvement over pure Pt but still appreciably lower than the thermodynamic limit. Under test conditions, the degradation of thusly-prepared films was primarily due to Co corrosion.
Ultrathin Pd films on well-defined Pt(111) surfaces, with coverages from 0.5 to 8 monolayers (ML), were prepared by surface-limited redox replacement reaction (galvanic exchange) of underpotentially deposited Cu. Spectroscopic data revealed that films prepared in this manner are elementally pure, pseudomorphic to the substrate, and stable, independent of the surface coverage (?) of palladium. Analysis of the voltammetric profiles in the hydrogen evolution region revealed unique properties of hydrogen adsorption unseen in bulk electrodes. Notably, at 1 ML coverage, a step-free film was produced that did not exhibit hydrogen absorption. At higher coverages, digital (layer-by-layer) deposition gave way to 3D islands in a Stranski- Krastanov growth mode; under these conditions, onset of bulk-like behavior was observed. This method makes possible the synthesis of well-ordered noble-metal films in the absence of high-temperature treatment
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Aulická, Marie. "Modelové katalyzátory na bázi oxidu ceru." Doctoral thesis, 2016. http://www.nusl.cz/ntk/nusl-352075.
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This work deals with the preparation of thin cerium oxide films on the Cu(110) single crystal. Physico-chemical properties of this system were studied by surface science techniques (XPS, UPS, ARUPS, LEED, LEEM and STM). The first part of the work concerns interaction of Cu(110) single crystal with oxygen. Condi- tions for formation of O(2x1) and Oc(6x2) oxygen reconstructions were found. Various methods of preparation of CeOx films were discussed. A novel method for continuous control of ceria stoichiometry from CeO2 to Ce2O3 through variation of oxygen vacancy concentration has been developed. Ceria facilitated oxygen spill-over was observed on copper substrate. It was found that a restructuring of copper substrate occurs at the copper-ceria interface with subsequent formation of Cu(13 13 1) facets, which support a Carpet-like ceria overlayer. Interaction of this system with platinum was studied. Finally, high temperature growth of CeOx films was studied and creation of ceria islands exposing the (110) plane was observed. 1