Dissertations / Theses on the topic 'Platinum adsorption'
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Newell, Helen E. "Alkane adsorption on metal surfaces." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243748.
Full textCruz, C. I. de la. "Infrared spectroscopic studies of adsorption on platinum/silica surfaces." Thesis, University of East Anglia, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377696.
Full textRobinson, 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.
Full textReichelt, M. A. "Structure and adsorption studies on the Pt-W(100) system." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235226.
Full textOakes, Darren J. "Dissociative adsorption of simple alkanes induced by hyperthermal collisions with platinum." Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384811.
Full textWartnaby, Charles. "Adsorption and reaction microcalorimetry on nickel and platinum single crystal surfaces." Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/275355.
Full textWelch, Philip Colin Charles. "Infrared characterisation of adsorbed species on platinum and silver surfaces." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262625.
Full textGee, Adam Timothy. "The role of steps in the dynamics of dissociative adsorption at surfaces." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310485.
Full textLim, Seng Woon. "Surface reactions, solvation, and adsorption phenomena of electrolytic adlayers on metal surfaces /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9837.
Full textYeo, Yee Yen. "Adsorption and reaction calorimetry on platinum, palladium and nickel single crystal surfaces." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627248.
Full textFayemi, Omolola Esther. "The development of platinum and palladium-selective polymeric materials." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1002964.
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Janin, Emmanuelle. "Adsorption and bonding on platinum : influence of the surface structure and chemical composition." Doctoral thesis, KTH, Physics, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3079.
Full textThis thesis deals with the influence of the structure andchemical composition of platinum surfaces on the adsorption ofsome molecules. Three main lines can be distinguished : 1) thecharacterisation of clean/modified surfaces, 2) the adsorptionof some simple atoms and molecules on these surfaces andfinally 3) the adsorption of 2-butenal, a bi-functionalmolecule containing a C=C group conjugated with a C=O group.The main tools used in this work are scanning tunnellingmicroscopy, photoelectron spectroscopy and high-resolutionelectron energy loss spectroscopy, in combination with quantumchemical calculations.
The platinum (111)(1× 1) and (110)(1× 2) surfacesare chosen as substrates. Pt(111) is a non-reconstructedclose-packed surface, while the Pt(110) surface is open, due toits missing row (MR) reconstruction, which results in thealternation of ridges, {111} microfacets and valleys. Titaniumgrows on Pt(111) in a Volmer-Weber mode. Pronounced reactionsbetween Pt and Ti are detected already at room temperature asthe Ti2p and Pt4f7/2core-level shifts are characteristic of the Pt3Ti alloy. Carbon segregated on the (110) surfaceappears as extended graphitic regions, which smoothen thesubstrate. Sn deposition at room temperature on Pt(110) resultsin the appearance of small islands, randomly spread over thesurface. The presence of mobile Sn ad-atoms and Pt-Sn-Ptalloyed chains in the valley of the MR reconstruction is alsoevidenced. Annealing the surface results in the rearrangementof the tin in the surface layer, together with a globalshortening of the terraces in the [110]direction and anincreased density of (1× n) (n>2) defects.
The adsorption of atomic hydrogen and oxygen has beenperformed on the Pt(111)( √ 3x √3)R30º surfacealloy and on Pt(110)(1× 2) respectively. The adsorptionsite of these atoms is changed as compared to the onedetermined on the clean Pt(111) surface (i.e. fcc hollow site): H is adsorbed on-top site on the (√3× √3)surface alloy, and O sits on the ridge of the missing rowreconstruction in bridge site. Carbon monoxide adsorption wasperformed on Pt(111) and Pt(110)(1× 2) surfaces, modifiedor not by tin. On the unmodified (111) surface, CO adsorbsfirst in top site, thenin bridge. Changing the geometry of thesurface to the (110) results in the vanishing of the bridgesite population. Modifying these surfaces by Sn does not changethe CO adsorption site.
Finally, 2-butenal (CH3-CH=CH-CH=O) has been adsorbed at 100 K on thePt(111) surface and the Sn/Pt(111) surface alloys. On theunmodified Pt surface, comparison with results obtained forpropene (CH2=CH-CH3) adsorption evidences the involvement of the C=Cgroup of the 2-butenal molecule in the bonding to the Ptsurface. The carbonyl group is also suggested to take part inthe bonding, through a σccη1(O) configuration. This carbonyl group bondingdisappears when Sn is alloyed to the surface, and the formationof a new physisorbed phase is detected.
Li, Nanhai. "Ionic and molecular adsorption at the single crystal surfaces of platinum and gold." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/NQ55630.pdf.
Full textPyshnov, Elizabeth. "Electrochemical studies of the adsorption of bovine serum albumin on a platinum surface." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81558.
Full textThe adsorption of BSA at anodic potentials has been found to be a competitive process occurring in parallel with platinum oxide formation. It has been found that the adsorption charge is directly proportional to the amount of protein adsorbed. With the increase in temperature, the maximum amount of adsorbed BSA (saturated surface concentration) also increases. This dependence has been found to be linear. It has also been shown that the adsorption process is dependent on the electrode surface charge.
Cook, Alexander C. "A study of the adsorption and enantioselective reaction of methyl pyruvate on platinum." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/13457.
Full textKarmazyn, Andrew Daniel. "Single crystal adsorption calorimetry on iron and high-Miller-index platinum and nickel surfaces." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613998.
Full textLoh, 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.
Full textSnyders, Cornelius Albert. "The adsorption and elution of Pt-, Pd- and Au cyanide using activated carbon." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96993.
Full textENGLISH ABSTRACT: In order to exploit lower grade and complex platinum group metal resources, cheaper and more efficient alternatives to the conventional mill-float-smelt-refine route are being sought. Leaching of platinum and palladium with cyanide has been proposed a number of times as a promising precious group metals (PGM) process option, and although platinum extractions are problematic, progress into the understanding of cyanide leaching of PGM containing ore and concentrate has been made. The platinum and palladium leaching will typically take place at elevated temperatures, which can range from 55°C on heaps to 180°C in autoclaves, with a better degree of leaching occurring with higher temperatures. Although this process for Pt and Pd extraction is a promising process option, research regarding the feasibility of the subsequent upgrading and recovery of the pregnant PGM leach solution, however, has been lacking. Since the carrier-phase extraction of gold using activated carbon offers significant advantages over other processes in terms of simplicity, the high pre-concentration factor, rapid phase separation, and relatively low capital and operating costs, activated carbon was deemed the most suitable sorbent for a Pt and Pd adsorption and stripping process. Very little is published on the adsorption of PGM cyanides onto activated carbon and when the effect of impurities such as base metals and thiocyanate together with a suitable elution method, are considered, no information could be found in the open literature. This study was launched and in general it was found that the activated carbon process does seem to be a viable process consideration for the upgrading of PGMs in a cyanide leach stream. Adsorption rates for dilute PGM solutions (0.15mg/L Pt, 0.38 mg/L Pd, 0.1 mg/L Au) in a stirred vessel indicated a high rate of adsorption within the first 60 minutes (giving more than 98% recovery of precious metals). A comparison of the Pt isotherm (25°C) to Au isotherms from literature indicated a similar loading capacity, while that of Pd was found to be significantly lower. In common with most diffusion controlled processes, an increase in the adsorption rate of platinum, palladium and gold cyanide with an increase in temperature was observed, while experiments with consecutive contacts of the PGM cyanide solution onto the activated carbon revealed that with an increase in temperature, the amount of PGMs that were adsorbed, decreased with each loading. In the absence of free cyanide and base metals, it was found that after 4 consecutive contacts, 99% of the total amount of platinum and palladium adsorbed at 25°C, compared to 85% of the platinum and 83% of the palladium at 50°C. No difference could be seen between the adsorption of gold cyanide at 25 and 50°C after 4 contacts. It has also been established that the detrimental effect of free cyanide on the adsorption of PGMs will increase as the temperature increases. The detrimental effect of the presence of Cu and Ni was found to depend on the amount of these base metals adsorbed, which in turn will depend on the cyanide concentration and the solution temperature. Adsorption of Pt and Pd has been found to be significantly more affected by temperature, cyanide and base metals than the adsorption of gold and needs to be carefully taken into consideration with the design of a PGM adsorption circuit to ensure sufficient Pt and Pd recovery. It is therefore highly likely that an activated carbon recovery process for Pt and Pd cyanide will not be as robust as the gold CIS (carbon-in-solution) process, which is considered to be one of its main advantages. The feasibility of eluting platinum and palladium cyanide complexes from activated carbon was investigated. It was found that platinum and palladium elute from activated carbon almost to completion in 4 to 5 bed volumes (BV) at 80°C, while the elution of gold at this temperature is slow, with a significant amount of gold (≈ 55 %) still to be eluted after 16 bed volumes. An increase in Pt and Pd elution kinetics was demonstrated with an increase in temperature with 99% recovery achieved at 4 BVs with an elution temperature of 95°C. Cyanide pre-treatment has been found to have a large influence on PGM elution. The effect of the NaCN concentration shows an increase in the recovery of Pt, Pd and Au as the cyanide increases from 0 to 2 %, after which the recovery starts decreasing again as the NaCN concentration increases from 2 to 4%. The NaOH concentration was also found to affect the PGM recovery and at 0% NaCN, an increase in the recovery is seen, while at a higher cyanide concentration (2 and 3% NaCN) a decrease in the PGM recovery occurs when the NaOH concentration is increased from 0.22% to 1.65%. A general decrease in Pt, Pd and Au recovery was seen as the ionic strength of the elution water increased and is consistent with literature on Au elution. The effect of a hydrochloric acid pre-treatment, which forms part of the process to remove calcium build-up from the activated carbon, was investigated, and for all the cases the Pt and Pd recovery increased when an acid pre-treatment was performed, compared to no acid pre-treatment. In none of the cases did any of the Pt, Pd or Au elute with the acid or the following rinsing water. The acid pre-treatment performed at 70°C removed a significant 64% to 75% of the Ni present and an additional 9.1% to 10.5% in the following rinsing water step. In the presence of copper cyanide, the elution order has been found to be copper, palladium, platinum and gold, which is the opposite order of adsorption preference. The cyanide pre-treatment has also been found to have a major influence on the elution of Cu and can be explained by the difference in the absorbance strength between the different copper cyanide complexes. The presence of Cu did not have a negative effect on the elution of the PGMs at strong pre-treatment (2% NaCN and 0.55% NaOH) conditions, but at weak pre-treatment conditions (0% NaCN) the recovery of Pt and Pd was reduced by between 10 and 18% after 5 BVs when Cu was present. The presence of 100 mg/L KSCN salt added to the leach solution during the adsorption stage, reduces the elution recovery of the PGMs at 4 BVs from 90% for Pt and Pd, when not present, to approximately 70% when present. The addition of the additional K+ ions reduced the recovery by less that 4% at 4 BV, which indicates that the possible formation of a PGM bonding with thiocyanate ([Pt(SCN)4]2- and [Pd(SCN)4]2-), which adsorb onto carbon, but doesn’t adsorb with water, cannot be ruled out completely. A maximum amount of 0.15% for Pt, 0.28% Pd and 0.6% Au was found to report to the pre-treatment solution at 25°C. For higher pre-treatment temperatures, the amount of Pt and Pd reporting to the pre-treatment solution increased significantly to approximately 8% at 80°C, while the increase in gold was marginal to 0.8% at 80°C. For the higher loading on the activated carbon (7000 mg/kg Pt and Pd), which is expected to be a better representation of plant conditions, 0.07% Pt, 0.11% Pd and 0.12% Au reported to the pre-treatment solution. The PGMs reporting to the pre-treatment solution is attributed to the distribution of the PGMs on the carbon particle, and even though very small, a certain amount of these PGMs would readily desorb or wash off the carbon. It has thus been established here that the stripping of adsorbed platinum cyanide complexes from activated carbon consists of a two step batch process, which involves the pre-treatment of the metal-loaded activated carbon with a relatively strong sodium cyanide and sodium hydroxide solution, prior to the elution step with de-ionized water at 80°C. Through the development of a mathematical model to describe this process, it was found that the rate of release of the platinum ions is governed by the amount of platinum and sodium on the activated carbon and the concentrations of these ions in the bulk of the liquid. This is mathematically described by a modified Freundlich isotherm equation and the mass transfer diffusion equation. The dependency of the platinum elution rate on the sodium concentration on the activated carbon, as suggested by gold related literature (Van Der Merwe and Van Deventer, 1990, Stange, 1990), is confirmed. Furthermore it has been found that the rate of platinum elution interchangeably depends on the equilibrium of the Pt ions at the carbon-liquid interface and the mass transfer of these Pt ions from the interface to the bulk liquid. As both of these rate-limiting factors were found to depend on the sodium concentration, the dominant platinum elution rate limiting factor shifts as the sodium concentrations change as the elution progresses. Four main time periods are used to simplify and to describe this process. The benefits of fundamentally understanding this process can ultimately lead to improved elution, better process control, shorter elution times, smaller elution columns or assist in the development of a continuous elution process.
AFRIKAANSE OPSOMMING: Nuwe prosesse om komplekse laer graad waardevolle metaal ertse te onwikkel in plaas van die konventionele maal-flotasie-smelt-raffineer proses word tans ondersoek. Loging van platinum en palladium met sianied is verskeie kere al voorgestel as n belowende proses opsie en alhoewel die ekstraksie van platinum nog 'n probleem is, is vordering al gemaak om die logings proses beter te verstaan. Die loging van platinum en palladium met sianied sal tipies plaasvind by hoër temperature wat kan wissel van 55°C in n hoop logins proses tot 180°C onder druk. Beter loging vind plaas soos wat die temperatuur styg. Alhoewel hierdie proses belowend is, is daar nog geen navorsing beskikbaar t.o.v die volgende stap in die proses wat die opgradering van die logings oplossing behels. Aangesien die gebruik van geaktiveerde koolstof in die goud industrie baie voordele inhou soos die eenvoudigheid van die proses, hoë opgraderings faktor, relatiewe vinnige adsorpsie en lae kapitaal en operationele kostes, mag hierdie tegnologie ook geskik wees vir Pt en Pd. Baie min is gepubliseer oor die adsorpsie van waardevolle metale (PGMs) met geaktiveerde koolstof en wanneer die effek van onsuiwerhede soos basis metale en thiosianied saam met n afstropings metode in ag geneem word, kon geen informasie in the literatuur gvind word nie. Hierdie studie is dus geloots en in die algemeen is daar bevind dat die geaktiveerde koolstof metode wel n geskikte oplossing bied vir die opgradering van PGMs in 'n sianied logings stroom. Adsorpsie snelheid vir verdunde PGM oplossings (0.15mg/L Pt, 0.38 mg/L Pd, 0.1 mg/L Au) in bekers wat geroer is, was vinnig vir die eerste 60 minutte (98% herwinning van die PGMs) en 'n vergelyking tussen die Pt adsorpsie isoterm en gepubliseerde Au isoterms wys op n relatiewe soorgelyke ladings kapasiteit. Die isotherm van Pd was egter laer. Soortgelyk aan meeste diffusie beheerde prosesse, het 'n verhoging van temperatuur gelei tot vinniger adsorpsie snelhede vir Pt, Pd en Au. Indien oplossings egter herhaaldelik met dieselfde koolstof in kontak gebring word, is bevind dat met 'n verhoging in temperatuur, die totale hoeveelheid PGMs wat absorbeer, met elke kontak verminder. In die afwesigheid van sianied en enige basis metale, het die totale hoeveelheid Pt en Pd wat geabsobeer is na 4 opeenvolgende kontake verminder van 99% by 25°C tot 85% adsorpsie van Pt en 83% Pd by 50°C. Daar was geen veskil tussen die adsorpsie van Au by 25°C en 50°C na 4 kontakte nie. Dit is ook vasgestel dat die negatiewe effek van vrye sianied in die oplossing, groter word soos wat die temperatuur verhoog. Die negatiewe effek van die teenwoordigheid van Cu en Ni, hang af van die hoeveelheid van hierdie metale wat absorbeer word wat weer bepaal word deur die sianied konsentrasie asook die temperatuur van die oplossing. Die mate waar in Pt en Pd ge-absorbeer word deur koolstof, word aansienlik meer beïnvloed deur temperatuur, sianied konsentrasie en die teenwoordigheid van basis metale as wat die adsorpsie van Au beïnvloed word. Met die ontwerp van n PGM adsorpsie proses, sal dit sterk in aanmerking geneem moet word, om seker te maak dat so min as moontlik Pt en Pd verlore gaan. Dit wys ook dat 'n geaktiveerde koolstof proses vir Pt en Pd, nie so onvatbaar vir proses veranderings sal wees soos wat die Au proses is nie, wat as een van die groot voordele van die Au proses beskou word. Die afstropery van die Pt en Pd sianied komplekse is ondersoek en gevind dat by 80°C, amper al die Pt en Pd binne 4 to 5 bed volumes (BV) van die geaktiveerde koolstof gestroop kan word. Die afstropery van Au by hierdie temperatuur is stadig en sowat 55% van die Au bly nog oor op die koolstof na 16 BVs. Die snelheid waarteen die Pt en Pd afgestroop word verhoog indien die temperatuur verhoog word en by 95°C is 99% van die Pt en Pd herwin na 4 BVs. Voorafbehandeling van die gelaaide koolstof met sianied, het 'n groot uitwerking op die PGM afstroping. Soos wat die NaCN konsentrasie verhoog word vanaf 0 tot by 2%, verhoog die PGM herwinning maar daal ook weer indien die NaCN konsentrasie verder verhoog word vanaf 2% tot by 4%. Die NaOH konsentrasie het ook n invloed gehad. By 0% NaCN, het die PGM herwinning verhoog soos wat die NaOH konsentrasie verhoog is maar by hoër sianied konsentrasies van 2 en 3%, is n daling in die herwinning waargeneem soos wat die NaOH verhoog is vanaf 0.22% tot by 1.65%. N algemene daling in die Pt, Pd and Au herwinning is waargeneem soos wat die ioniese sterkte van die stropings water toegeneem het. Dit stem ooreen met gepubliseerde navorsing oor die afstroping van Au. Om kalsium van die geaktiveerde koolstof te verwyder, word die koolstof vooraf met soutsuur gewas. Hierdie stap is vir Pt en Pd ondersoek en daar is bevind dat vir al die gevalle, die herwinning hoër was wanneer die gelaaide koolstof met soutsuur behandel is teenoor geen behandeling nie. In geen van die gevalle, is Pt, Pd of Au saam met die soutsuur of die daaropvolgende was water afgestroop nie. Voorafbehandeling met soutsuur teen 70°C lei wel daartoe dat tussen 64 en 75% Ni afgestroop word saam met die soutsuur en n verdere 9.1 to 10.5% saam met die daaropvolgende was water. In die teenwoordigheid van koper sianied, word Cu eerste afgestroop met Pd, Pt en dan Au wat daarop volg. Dit is presies die teenoorgestelde orde waarin die metale geabsorbeer word. Die voorafbehandeling met sianied, het ook 'n beduidende effek op die stroping van Cu. Dit kan verduidelik kan word aan die hand van die verskillende koper sianied komplekse wat vorm wat elkeen 'n verskillende affiniteit het vir adsorpsie. Wanneer 2% NaCN en 0.6% NaOH in die vooraf behandeling stap gebruik word, het die teenwoordigheid van koper geen negatiewe invloed op die afstroping van die PGMs gehad nie maar die herwinning is wel met 10% en 18% verlaag by 5 BVs wanneer geen sianied in die voorafbehandeling stap gebruik is nie. Wanneer 100 mg/L KSCN sout by die adsorpsie stap gevoeg word, daal die herwinning van die PGMs in die stropings stap van 90% tot 70% by 4 BVs. Die addisionel K+ katione verminder die herwinning met slegs 4% by 4 BVs wat beteken dat die vorming van adisionele komplekse soos [Pt(SCN)4]2- en [Pd(SCN)4]2-, wat nie op die normale metode afgestroop kan word, 'n moontlikheid mag wees. N maksimum van 0.15% vir Pt, 0.28% Pd en 0.6% Au word in die vooraf behandelings stap af gestroop. Indien die temperatuur van hierdie stap verhoog word na 80°C, verhoog die hoeveelheid Pt en Pd wat na hierdie stroom raporteer na 'n beduidende 8% tewyl Au basies onveranderd bly by 0.8%. Vir geaktiveerde koolstof wat hoër gelaai is (7000 mg/Kg Pt en Pd) en dus 'n beter verteenwoordiging van aanleg kondisies is, het 0.07% Pt, 0.11% Pd en 0.12% Au raporteer na die vooraf behandelings stap. Dit word toegeskryf aan die verspreiding van die PGMs op die koolstof wat hoofsaaklik op die oppervlakte voorkom en alhoewel die hoeveelheid klein is, word 'n sekere hoeveelheid slegs afgewas. Dit is dus vasgestel hier, dat die afstroping van Pt 'n twee stap proses is. Die eerste stap is die voorabehandeling van die koolstof met 'n sianied oplossing en daarna volg die afstroping van die Pt met suiwer water teen ongeveer 80°C. Met die ontwikkeling van n wiskundige model, is bevind dat die snelheid waarteen die Pt afgestroop word, beïnvloed word deur die hoeveelheid Pt en Na wat op die koolstof oppervlakte is, asook die konsentrasies van die metale in die vloeistof. Dit word wiskundig beskryf deur n gemodifiseerde Freundlich isotherm vergelyking asook deur die massa diffusie vergelyking. Die Pt afstropings snelheid wat afhanklik is van die Na konsentrasie kan vergelyk word met die afstroping snelheid van Au wat ook afhanklik is van die Na konsentrasie (Van Der Merwe and Van Deventer, 1990, Stange, 1990). Verder is bevind dat die snelheid van Pt stroping afhanklik is van beide die ewewig van Pt ione by die koolstof-vloeistof grens asook die massa beweging van Pt ione van die koolstof-vloeistof grens na die vloeistof. Beide hierdie snelheids bepalende faktore word bepaal deur die Na konsentrasie en skuif soos wat die Na konsentrasie verander soos wat die afstroping plaasvind. Vier hoof tyd periodes word gebruik om hierdie verskynsel te verduidelik. Deur die proses fundamenteel te verstaan, kan uiteindelik lei tot 'n beter proses, beter beheer, korter afstropings tye, kleiner toerusting of die ontwikkeling van 'n kontinue proses.
Baily, Christopher John. "UHV studies of the adsorption of small adsorbate molecules on low index platinum single crystals." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288413.
Full textYim, 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.
Full textMatengaifa, R. "Adsorption of oxygen molecules on platinum surfaces modified with subsurface atoms of vanadium : a DFT study." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13302.
Full textThe aim of this work was to investigate changes in the electronic structure of platinum as a result of alloying with vanadium, and the effects of these changes on O2 adsorption. This is important for the further development of hydrogen fuel cells, because the oxygen reduction reaction (ORR) presently requires O2 adsorption to occur on pure platinum, which is a prohibitively expensive material. A computational study has therefore been undertaken on alloying platinum (which reduces cost) with vanadium (for which there is plentiful experimental data) and the consequences for O2 adsorption. The first moment of the d-band of platinum alloy DOS was used to represent the d-band centre. The d-band centre of Pt-PDOS became lower as a result of hybridisation between platinum and vanadium. The d-band centre of a pure platinum surface with respect to the Fermi level is -1.99eV, but it is shifted to -3.23eV when vanadium atoms are added to the subsurface layer. The adsorption energies of O2 are sensitive to a combination of calculation parameters used. In this work, the calculations were executed using the CASTEP code. This is a plane wave pseudo potential code. The most stabilised geometry of an adsorbed molecule on pure Pt (111) was at the fcc site and had an adsorption energy of -1,91eV. The adsorption energy at the bridge site of Pt (111) is -1.81eV. When subsurface vanadium atoms were introduced, the equilibrium surface-molecule bond lengths increased. The adsorption energy at the fcc site shifted to -1.37eV, -1.43 for the bridge site and -1.45eV for the hcp site. It was concluded that the presence of vanadium atoms in the surface region destabilises an adsorbed oxygen molecule but a more detailed study is needed to show the effect of the solute atoms on the thermodynamics and kinetics of the whole oxygen reduction reaction chain.
Daramola, Oludamilola A. "Theoretical Characterization of Ammonia Oxidation Species on Platinum Clusters." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1321547233.
Full textWinski, David Nathaniel. "Design and construction of a polarization modulated infrared reflection absorption spectrometer and validation with carbon monoxide adsorption on a platinum (100) surface." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 96 p, 2009. http://proquest.umi.com/pqdweb?did=1889078511&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full textBetancourt, Angel E. "First principles calculations of the interaction of rare-gas atoms with transition metal surfaces." Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341150.
Full textJunior, Jaldyr de Jesus Gomes Varela. "Teoria do funcional da densidade aplicada ao estudo da interação entre oxigênio molecular e nanoclusters de platina dopados com Al, Cr e V." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-06102011-144550/.
Full textThis work presents a study applying the Density Functional Theory (DFT) using the B3LYP functional to study the electronic structure of platinum nanoclusters doped with Al, Cr and V and their interactions with molecular oxygen. The analysis of Mulliken populations and NBO for the interaction between O2 and Pt2, Pt-Cr and Pt-V showed that charge transfer occurs orbital sed metals for the p orbitals of oxygen, resulting in the filling of the antibonding orbitals of the molecule oxygen, causing the cleavage of O-O and bond forming hybridized Metal - O, bond dissociation energy of O - O on Pt2 about 1.0 eV. On Pt-Cr and Pt-V, this value decreases to 0.56 eV and 0.20 eV, respectively. Studies of the interaction between molecular oxygen and the Pt3 clusters, Pt2Al, Pt2Cr and Pt2V show that no dissociative adsorption occurs for molecular oxygen on the cluster Pt3 where we observe a second adsorption model bridge while on clusters Pt2Al and Pt2V dissociative adsorption occurs of molecular oxygen. Moreover, with the cluster Pt2Cr adsorption follows the model of Pauling, with molecular oxygen adsorbed on only one site in the cluster, which was the Pt atom, without the cleavage of the O-O. Curves of potential energy surface for dissociation of molecular oxygen on Pt2Al and Pt2V showed a value of about 0.21 eV for the bond dissociation barrier of the O-O adsorbed on the cluster Pt2Al approximately 0.30 eV and for the barrier The bond dissociation O-O adsorbed on the cluster Pt2V. Studies of the interaction between molecular oxygen and clusters Pt4, Pt3Al, Pt3Cr and Pt3V show that no dissociative adsorption occurs for molecular oxygen on clusters Pt4 and Pt3Cr where it was observed that the adsorption follows the model of the bridge. On the other hand, on clusters Pt3Al and Pt3V adsorption of molecular oxygen also followed the model bridge, with bond dissociation O - O. We found a value of 0.46 eV for the barrier to bond dissociation to O-O adsorbed on the cluster Pt3Al and approximately 0.28 eV for bond dissociation of the O-O adsorbed on the cluster Pt3V. Studies on the interaction between molecular oxygen and clusters Pt5, Pt4Al, Pt4Cr and Pt4V revealed that occurs dissociative adsorption of molecular oxygen on clusters Pt4Al and Pt4V, where we observe an adsorption model that follows the bridge while on the adsorption cluster Pt5 follows the bridge model without the bond dissociation. Moreover, adsorption is modeled on Pt4Cr Pauling with oxygen adsorbed on only one site of the cluster, without the cleavage of the O-O. Curves of potential energy surface showed a value of about 0.62 eV for the bond dissociation barrier of the O-O adsorbed on the cluster Pt4Al and approximately 0.20 eV energy barrier for bond dissociation of the O-O adsorbed on the Pt4V cluster.
Pierozynski, Boguslaw. "Adsorption and reactivity of resonant guanidonium-type cations and aliphatic oximes in the hydrogen UPD region at single-crystal surfaces of platinum." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9378.
Full textFeltovich, Susanne D. "Influence of solvent on the infared spectrum of carbon monoxide adsorbed on platinum electrodes." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09292009-020247/.
Full textFugivara, Cecílio Sadao. "Cinética de adsorção do n-propanol sobre eletrodo de platina platinizada em solução de ácido sulfúrico." Universidade de São Paulo, 1989. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-19022009-145126/.
Full textThe kinetics and mechanism of n-propanol adsorption on a platinized platinum electrode was studied in 1 N H2SO4 at several temperatures, by means of the potential pulse method. Between 0.30 V and 0.60 V (RHE), the adsorption occurs via a dehydrogenation of the α-carbon, followed by a rapid ionization of the adsorbed hydrogen atoms. The kinetic isotherms obtained by integration of the chronoamperograms show a linear variation of the surface coverage, θ, with logarithm of the adsorption time, tads, in the range 0.25 ≤ θ ≤ 0.80. This indicates that the adsorption rate can be expressed in tems of an Elovich equation. It is shown that the relation Eads vs log Ii, where Eads is the adsorption potential and Ii is the maximum non-stationary current at t = 0, is a straight line with a slope equal to 2.3[2RT/F], independently of the temperature. These data show that the initial adsorption step envolves a monoelectronic charge transfer, and can be represented by the following equation: R-CH2-OH j1→ R-.CH-OH + H+ + e- ( 1 ) Therefore, it is assumed that the adsorption occurs via a two step consecutive reaction, given by equations (1) and (2): R-.CH-OH j2→ R-..C-OH + H+ + e- ( 2 ) with the two adsorbed species R-.CH-OH and R-..C-OH characterized by their degree of coverage θ1 and θ2, respect ively. The non-stationary anodic current, j, is then the sum of currents j1 and j2 resulting from reactions described by equations (1) and (2). When the adsorption time is very short, it can be assumed that j = j1 + j2 ≈ j1, and that θ = θ 1 + θ2 ≈ θ1. From those assumptions, the following equation relating θ1 with t was obtained: θ1 = -Qmáx . B/[k2.t (1-A-B). ln t ] + k1/k2 (3) where Qmáx is the charge related with the maximum surface coverage, k1 and k2 the apparent rate constants of reactions (1) and (2), respectively, and A and B are constants from the Elovich equation. Equation (3) permitted the evaluation of the rate constants k1 and k2 for distinct Eads values. From the data at different temperatures, the apparent activation energies of both reactions were calculated.
Mack, Cherie-Lynn. "Biosorption of precious metals from synthetic and refinery wastewaters by immobilized saccharomyces cerevisiae." Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1006977.
Full textLghouzouani, Larbi. "Effet du souffre, du cuivre et du plomb sur l'activité et la sélectivité des catalyseurs au platine." Poitiers, 1987. http://www.theses.fr/1987POIT2319.
Full textLi, Rui. "Theoretical investigation of electronic properties of atomic clusters in their free forms and adsorbed on functionalized graphene support." Thesis, Pau, 2016. http://www.theses.fr/2016PAUU3018/document.
Full textA sub-nanometer sized metal cluster consists of only several to tens of atoms. Due to its small size and quantum effects, it can have very specific electronic, optical, magnetic and catalytic properties as compared with their bulk behaviors . From an experimental point of view, it is still a big challenge to realize size-controlled synthesis for (sub) nanoclusters. From a theoretical point of view, benefiting from the development of faster high-performance computational sources, more efficient electronic structure modelling software and more reliable global search methods for the determination of the most stable structures, the chemical and physical properties of clusters can be determinate more accurately. As it is experimentally a big challenge to realize size-controlled synthesis for (sub) nanoclusters, theoretical studies can provide detailed information on their geometric structure, electronic structure, as well as adsorption and reaction properties . The example chosen to be treated in this study is inspired by the fuel cell, in which the Platinum (Pt) is a typical and most commonly used precious metal catalyst for the production of energy by the oxidation of dihydrogene . Graphene is a recently discovered 2D carbon net structure, has several special properties, such as: low weight, high strength, high surface area, high electrical conductivity, etc. With these properties and their novel combinations, graphene might prove a promising candidate to be used as catalyst supports. The first part of this study is devoted to the search of the doping elements which permit both enhance the adsorption capacity of Pt clusters on the surface and prevent their migration. The aim here is propose one substrate which can avoid the problems of cluster agglomeration, dissolution and detachment, which reduce the performance of the catalysts . The ways of doping of the surface, which have already been experimentally realized , such as Nitrogen, Boron, and N-B patches substitution of Carbon atoms with or without introducing the vacancy on the pristine graphene, are studied. The second part corresponds to the implementation of some new features into the code GSAM (Global Search Algorithm of Minima) developed in our laboratory , , , which permit the search of the most stable structures of the molecular clusters adsorbed on substrate, such as the complex systems of [H2-Ptn-doped Graphene]. The third part is to evaluate the reliabilities of the global search method used, as well as the DFT and the empirical (GUPTA) potential energy surface. Thus, the main discussion appears as a comparison with the results of the literature concerning the Pt clusters. The fourth part consists of the structural investigation of [H2-Ptn] and [H2-Ptn-doped Graphene] systems for different sizes of Pt clusters with n=6 to n=20. The variation of the adsorption energy of H2 on the free and supported Ptn clusters, and the adsorption energy of (H2+Ptn) system on the surface with respect to the size of the cluster is discussed
Tainon, Yannick. "Etude par méthodes électrochimiques et spectroscopiques "in situ" de catalyseurs au platine partiellement désactives par adsorption de composés soufres." Poitiers, 1988. http://www.theses.fr/1988POIT2265.
Full textRicoux, Quentin. "Extraction sélective de métaux du groupe platine par sorption sur des polymères fonctionnels à base de phosphines." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS283.
Full textThe objective of this work consists in studying and implementing innovative functional polymer materials under powder form for the selective extraction of platinum group metals (PGM) from industrial effluents. The main interest of the polymeric materials studied in this work relies on their shaping powder, avoiding the use of inert support, and their binding functions: phosphine (MP-101) and phosphine oxide (MP-102).It has been shown that Pd2 + sorption (target metal ion) occurs by chelation through the phosphine functionalities onto the MP-101 and through the phosphine oxides functionalities on the MP-102. This binding mode induces higher sorption energies and selectivity toward Pd than the currently ion exchange mode. While the operating parameters such as pH, ionic strength and composition of the effluent were shown to affect the Pd sorption onto the MP-102, sorption onto MP-101 is less affected by these operating parameters since the interactions phosphine-palladium are very strong. Consequently, the Pd sorption onto MP-102 is completely reversible by elution with thiourea and sorption onto MP-101 lead to sorption capacities up to 8 mmol.g-1 in solutions representative of industrial effluents where the concentration of sulfuric acid can reach several moles per liter. The MP-102 has been implemented in a continuous process coupling a sorption stage with microfiltration. This system allowed using the polymer during successive sorption-desorption cycles without loose of sorption efficiency. This coupled process allowed the selective extraction of palladium and platinum from a leach solution with catalysts. The MP-101 was implemented in a system coupling sorption with a flocculation-decantation stage followed by the incineration of the sludge, allowing the recovery of metals in metallic form. This method has been successfully applied to mining effluents to the selective extraction of Pd and Pt
Garnier, Anaïs. "Platine sur silice : exemples réussis de synthèse par voie organométallique pour la catalyse hétérogène : validation par l'adsorption et la réactivité du CO." Thesis, Strasbourg, 2013. http://www.theses.fr/2013STRAF040/document.
Full textOrganometallic chemistry resonates with homogeneous catalysis, and surface chemistry with heterogeneous catalysis. But the frontier between these two fields is very thin. In the 90’s, these fields approached each other and led to the development of a new science: organometallic surface chemistry, which underlines their complementarity. The goal of this science, with which this work is associated, is to create heterogeneous catalysts from organometallic compounds. Our goal is to contribute to the understanding of platinum nanoparticle formation - platinum being an important metal in heterogeneous catalysis - onto amorphous silica supports, thanks to organometallic chemistry. During this work, various Pt/SiO2 catalysts were prepared fromthree platinum precursors: the classical one, H2PtIVCl6.xH2O and two organometallic compounds PtII(η 4-C8H12)Cl2 et Pt0(η2-C7H10)3, and involved three supports: a commercial silica (Davison), a mesoporous silica SBA-15 synthesized in the laboratory, and a natural silica, the diatomite. Moreover, the study of the standard platinum reference catalyst “EuroPt-1” lead to the development of a methodology of operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) of carbon monoxide (CO) adsorption on the different sites of a platinum nanoparticle. Catalysts prepared from Pt0(η 2-C7H10)3 are more active than EuroPt-1 for the CO oxidation reaction, and this work shows the potential of organometallic precursors in the domain of heterogeneous catalysis
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.
Full textArmand, Dominique. "Etude du rôle des structures cristallines intrinsèque et induite du platine sur l'électrosorption de l'hydrogène et de l'oxygène en milieu acide." Paris 6, 1986. http://www.theses.fr/1986PA066073.
Full textCarpentier, Pascal. "Etude de la sorption des oxydes de soufre par des masses regenerables a base d'oxyde de magnesium." Paris 6, 1987. http://www.theses.fr/1987PA066296.
Full textMalki, Abdelhafid. "Transformation électrocatalytique de produits issus de la biomasse : oxydation du fructose sur électrodes d'or et de platine." Poitiers, 1988. http://www.theses.fr/1988POIT2274.
Full textNordlund, Dennis. "Core Level Spectroscopy of Water and Ice." Doctoral thesis, Stockholm : Fysikum, Univ, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-181.
Full textChassary, Philippe. "Adsorption de métaux précieux (palladium, platine) sur chitosane." Montpellier 2, 2004. http://www.theses.fr/2004MON20001.
Full textSchlapka, Andreas. "Adsorption von CO und O2 auf Pt-Ru(001)- Bimetalloberflächen." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=966110072.
Full textBlais, Sonia. "Étude du comportement électrochimique de couches inorganiques ultra-fines sur l'électrode de platine (111)." Sherbrooke : Université de Sherbrooke, 2000.
Find full textRadovic, 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.
Find full textChollier, Marie-Josée. "Adsorption et oxydation catalytique d'acides carboxyliques en milieu aqueux." Poitiers, 1997. http://www.theses.fr/1997POIT2293.
Full textMatic, Nikola. "SURFACE SCIENCE ASPECTS OF ELECTROCATALYSIS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1397794046.
Full textTakky, Driss. "Effet de la structure moléculaire en electrocatalyse : étude mécanistique de l'oxydation des isomères du butanol en milieu aqueux sur diverses électrodes de metaux nobles." Poitiers, 1987. http://www.theses.fr/1987POIT2008.
Full textBenmansour, Moncef. "Application de l'analyse par réactions nucléaires à l'étude de l'adsorption de l'hydrogène et du benzène sur des monocristaux de nickel et d'alliage Pt50 Ni50." Lyon 1, 1992. http://www.theses.fr/1992LYO10032.
Full textVASSILAKIS, DESPINA. "Adsorption et reactivite de diolefines en presences d'hydrogene et de sulfure d'hydrogene sur platine." Paris 6, 1990. http://www.theses.fr/1990PA066350.
Full textBOURDIN, JEAN-PIERRE. "Contribution a l'etude de la structure electronique et des proprietes d'adsorption des surfaces des metaux de transition." Nantes, 1987. http://www.theses.fr/1987NANT2024.
Full textMoussounda, Paul Sand. "Adsorption et activation du méthane et du méthanol sur la surface (100) du platine : Une étude par la fonctionnelle de la densité." Université Louis Pasteur (Strasbourg) (1971-2008), 2006. https://publication-theses.unistra.fr/public/theses_doctorat/2006/MOUSSOUNDA_Paul_Sand_2006.pdf.
Full textThe activation of methane (CH4) and methanol (CH3OH) on Pt(100) surface has been investigated using density functional theory calculations based on plane-wave basis and pseudo-potential. We optimised CH4/Pt(100) system. The calculated adsorption energies over the top, bridge and hollow sites are small, weakly dependent on the molecular orientation. The nature of the CH4-Pt interaction was examined through the electronic structure changes. The adsorption of methyl (CH3) and hydrogen (H) and the coadsorption of CH3+H were also calculated. From these results, we examined the dissociation of CH4 to CH3+H, and the activation energies found are in good agreement with the experimental and theoretical values. The activation of CH3OH/Pt(100) has been studied. All the sites have almost the same adsorption energy. The adsorption of oxygen (O) and the coadsorption of CH4 and O were also examined. In addition, the formation of CH3OH assuming a one-step mechanism step via the coadsorption of CH4+O has been studied and the barrier height was found to be high