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Velinova R, Todorova S, Kovacheva D, Kolev H, Karakirova Y, Markov P, Tumbalova K, Ivanov G, Naydenov A. Effect of TiO 2 on Pd/La 2O 3-CeO 2-Al 2O 3 Systems during Catalytic Oxidation of Methane in the Presence of H 2O and SO 2. MATERIALS (BASEL, SWITZERLAND) 2023; 16:6784. [PMID: 37895766 PMCID: PMC10608221 DOI: 10.3390/ma16206784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 10/10/2023] [Accepted: 10/18/2023] [Indexed: 10/29/2023]
Abstract
New results on the effect of TiO2 on Pd/La2O3-CeO2-Al2O3 systems for catalytic oxidation of methane in the presence of H2O and SO2 have been received. Low-temperature N2-adsorption, XRD, SEM, HRTEM, XPS, EPR and FTIR techniques were used to characterize the catalyst. The presence of Ce3+ on the catalytic surface and in the volume near the lantana was revealed by EPR and XPS. After aging, the following changes are observed: (i) agglomeration of the Pd-clusters (from 8 nm to 12 nm); (ii) transformation of part of the TiO2 from anatase to larger particles of rutile; and (iii)-the increase in PdO/Pd-ratio above its optimum. The modification by Ti of the La2O3-CeO2-Al2O3 system leads to higher resistance towards the presence of SO2 most likely due to the prevailing formation of unstable surface sulfites instead of thermally stable sulfates. Based on kinetic model calculations, the reaction pathway over the Pd/La2O3-CeO2-TiO2-Al2O3 catalyst follows the Mars-van Krevelen mechanism. For evaluation of the possible practical application of the obtained material, a sample of Pd/La2O3-CeO2-TiO2-Al2O3, supported on rolled aluminum-containing stainless steel (Aluchrom VDM®), was prepared and tested. Methane oxidation in an industrial-scale monolithic reactor was simulated using a two-dimensional heterogeneous reactor model.
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Affiliation(s)
- Ralitsa Velinova
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Silviya Todorova
- Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Daniela Kovacheva
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Hristo Kolev
- Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Yordanka Karakirova
- Institute of Catalysis, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Pavel Markov
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Katerina Tumbalova
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Georgi Ivanov
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
| | - Anton Naydenov
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria
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Reaction Kinetics and Mechanism of VOCs Combustion on Mn-Ce-SBA-15. Catalysts 2022. [DOI: 10.3390/catal12060583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A propane combustion catalyst based on Mn and Ce and supported by SBA-15 was prepared by the “two-solvents’’ method aiming at the possible application in catalytic converters for abatement of alkanes in waste (exhaust) gases. The catalyst characterization was carried out by SAXS, N2-physisorption, XRD, TEM, XPS, EPR and H2-TPR methods. The catalysts’ performance was evaluated by tests on the combustion of methane, propane and butane. The reaction kinetics investigation showed that the reaction orders towards propane and oxygen were 0.7 and 0.1, respectively. The negative reaction order towards the water (−0.3) shows an inhibiting effect on the water molecules. Based on the data from the instrumental methods, catalytic experiments and mathematic modeling of the reaction kinetics, one may conclude that the Mars–van Krevelen type of mechanism is the most probable for the reaction of complete propane oxidation over single Mn and bi-component Mn–Ce catalysts. The fine dispersion of manganese and cerium oxide and their strong interaction inside the channels of the SBA-15 molecular sieve leads to the formation of difficult to reduce oxide phases and consequently, to lower catalytic activity compared to the mono-component manganese oxide catalyst. It was confirmed that the meso-structure was not modified during the catalytic reaction, thus it can prevent the agglomeration of the oxide particles.
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Abstract
Reported here are new data on the structural and catalytic properties of a series of mono-component cobalt and bi-component Co–Ce catalysts supported on SBA-15 (Santa Barbara Amorphous-15)). The catalysts performance has been evaluated by tests on combustion of methane, propane, and n-hexane. It was established that the preparation of the Co–Ce catalysts by the ‘two-solvent’ technique does not significantly change the mesoporous structure, however, its pores are clogging with the Co and Ce guest species. Cobalt and cerium are uniformly distributed and preferentially fill up the channels of SBA-15, but oxide agglomerates located on the surface are observed as well. The highest activity of the mono-component cobalt sample is explained by its higher reducibility as a result of lower interaction of the cobalt oxide with the SBA-15. The fine dispersion of cobalt and cerium oxide and their strong interaction in the channels of the SBA-15 molecular sieve, leads to the formation of difficult-to-reduce oxide phases and, consequently, to lower catalytic activity compared to monocomponent cobalt oxide catalyst. The synthesised mesoporous structure can prevent the agglomeration of the oxide particles, thus leading to the successful development of a new and stable catalyst for decreasing greenhouse gas emissions.
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Kardash TY, Derevyannikova EA, Slavinskaya EM, Stadnichenko AI, Maltsev VA, Zaikovskii AV, Novopashin SA, Boronin AI, Neyman KM. Pt/CeO 2 and Pt/CeSnO x Catalysts for Low-Temperature CO Oxidation Prepared by Plasma-Arc Technique. Front Chem 2019; 7:114. [PMID: 30931295 PMCID: PMC6424011 DOI: 10.3389/fchem.2019.00114] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 02/13/2019] [Indexed: 11/13/2022] Open
Abstract
We applied a method of plasma arc synthesis to study effects of modification of the fluorite phase of ceria by tin ions. By sputtering active components (Pt, Ce, Sn) together with carbon from a graphite electrode in a helium ambient we prepared samples of complex highly defective composite PtCeC and PtCeSnC oxide particles stabilized in a matrix of carbon. Subsequent high-temperature annealing of the samples in oxygen removes the carbon matrix and causes the formation of active catalysts Pt/CeOx and Pt/CeSnOx for CO oxidation. In the presence of Sn, X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HRTEM) show formation of a mixed phase CeSnOx and stabilization of more dispersed species with a fluorite-type structure. These factors are essential for the observed high activity and thermic stability of the catalyst modified by Sn. X-Ray Photoelectron Spectroscopy (XPS) reveals the presence of both Pt2+ and Pt4+ ions in the catalyst Pt/CeOx, whereas only the state Pt2+ of platinum could be detected in the Sn-modified catalyst Pt/CeSnOx. Insertion of Sn ions into the Pt/CeOx lattice destabilizes/reduces Pt4+ cations in the Pt/CeSnOx catalyst and induces formation of strikingly high concentration (up to 50% at.) of lattice Ce3+ ions. Our DFT calculations corroborate destabilization of Pt4+ ions by incorporation of cationic Sn in Pt/CeOx. The presented results show that modification of the fluorite lattice of ceria by tin induces substantial amount of mobile reactive oxygen partly due to affecting geometric parameters of ceria by tin ions.
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Affiliation(s)
- Tatyana Y Kardash
- Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | - Elizaveta A Derevyannikova
- Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Elena M Slavinskaya
- Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | - Andrey I Stadnichenko
- Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | - Vasiliy A Maltsev
- Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Alexey V Zaikovskii
- Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Sergey A Novopashin
- Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Andrei I Boronin
- Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.,Novosibirsk State University, Novosibirsk, Russia
| | - Konstantin M Neyman
- Departament de Ciència dels Materials i Química Física, Universitat de Barcelona, Barcelona, Spain.,Institut de Química Teòrica i Computacional, Universitat de Barcelona, Barcelona, Spain.,ICREA (Institució Catalana de Recerca i Estudis Avançats), Barcelona, Spain
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Schaefer A, Hagman B, Höcker J, Hejral U, Flege JI, Gustafson J. Thermal reduction of ceria nanostructures on rhodium(111) and re-oxidation by CO 2. Phys Chem Chem Phys 2018; 20:19447-19457. [PMID: 29998237 DOI: 10.1039/c8cp01505h] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The thermal reduction of cerium oxide nanostructures deposited on a rhodium(111) single crystal surface and the re-oxidation of the structures by exposure to CO2 were investigated. Two samples are compared: a rhodium surface covered to ≈60% by one to two O-Ce-O trilayer high islands and a surface covered to ≈65% by islands of four O-Ce-O trilayer thickness. Two main results stand out: (1) the thin islands reduce at a lower temperature (870-890 K) and very close to Ce2O3, while the thicker islands need higher temperature for reduction and only reduce to about CeO1.63 at a maximum temperature of 920 K. (2) Ceria is re-oxidized by CO2. The rhodium surface promotes the re-oxidation by splitting the CO2 and thus providing atomic oxygen. The process shows a clear temperature dependence. The maximum oxidation state of the oxide reached by re-oxidation with CO2 differs for the two samples, showing that the thinner structures require a higher temperature for re-oxidation with CO2. Adsorbed carbon species, potentially blocking reactive sites, desorb from both samples at the same temperature and cannot be the sole origin for the observed differences. Instead, an intrinsic property of the differently sized CeOx islands must be at the origin of the observed temperature dependence of the re-oxidation by CO2.
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Affiliation(s)
- Andreas Schaefer
- Department of Chemistry and Chemical Engineering - Competence Centre for Catalysis, Chalmers University of Technology, Gothenburg, 412 96, Sweden.
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Mukherjee D, Devaiah D, Venkataswamy P, Vinodkumar T, Smirniotis PG, Reddy BM. Superior catalytic performance of a CoOx/Sn–CeO2 hybrid material for catalytic diesel soot oxidation. NEW J CHEM 2018. [DOI: 10.1039/c8nj01184b] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A Co3O4/Sn–CeO2 hybrid catalyst exhibited superior soot oxidation activity due to the existence of synergism among the multivalent cations and the stepped surface of the hybrid catalyst.
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Affiliation(s)
- Deboshree Mukherjee
- Inorganic and Physical Chemistry Division
- CSIR – Indian Institute of Chemical Technology
- Uppal Road
- Hyderabad 500 007
- India
| | - Damma Devaiah
- Chemical Engineering
- College of Engineering and Applied Science
- University of Cincinnati
- Cincinnati
- USA
| | | | - T. Vinodkumar
- Department of Chemistry
- Indian Institute of Technology
- Hyderabad 502 285
- India
| | - Panagiotis G. Smirniotis
- Chemical Engineering
- College of Engineering and Applied Science
- University of Cincinnati
- Cincinnati
- USA
| | - Benjaram M. Reddy
- Inorganic and Physical Chemistry Division
- CSIR – Indian Institute of Chemical Technology
- Uppal Road
- Hyderabad 500 007
- India
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7
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You R, Zhang X, Luo L, Pan Y, Pan H, Yang J, Wu L, Zheng X, Jin Y, Huang W. NbO x /CeO 2 -rods catalysts for oxidative dehydrogenation of propane: Nb–CeO 2 interaction and reaction mechanism. J Catal 2017. [DOI: 10.1016/j.jcat.2016.12.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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8
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9
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Neitzel A, Kovács G, Lykhach Y, Tsud N, Kozlov SM, Skála T, Vorokhta M, Matolín V, Neyman KM, Libuda J. Steering the formation of supported Pt–Sn nanoalloys by reactive metal–oxide interaction. RSC Adv 2016. [DOI: 10.1039/c6ra18801j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The thermodynamically favorable bulk and surface Pt/Sn stoichiometries drive the growth of the Pt–Sn nanoalloy upon Pt deposition onto a Sn–CeO2 substrate at 300 K under ultra-high vacuum conditions.
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10
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Mysliveček J, Matolín V, Matolínová I. Heteroepitaxy of Cerium Oxide Thin Films on Cu(111). MATERIALS 2015; 8:6346-6359. [PMID: 28793567 PMCID: PMC5512914 DOI: 10.3390/ma8095307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 09/12/2015] [Accepted: 09/14/2015] [Indexed: 01/09/2023]
Abstract
An important part of fundamental research in catalysis is based on theoretical and modeling foundations which are closely connected with studies of single-crystalline catalyst surfaces. These so-called model catalysts are often prepared in the form of epitaxial thin films, and characterized using advanced material characterization techniques. This concept provides the fundamental understanding and the knowledge base needed to tailor the design of new heterogeneous catalysts with improved catalytic properties. The present contribution is devoted to development of a model catalyst system of CeO2 (ceria) on the Cu(111) substrate. We propose ways to experimentally characterize and control important parameters of the model catalyst—the coverage of the ceria layer, the influence of the Cu substrate, and the density of surface defects on ceria, particularly the density of step edges and the density and the ordering of the oxygen vacancies. The large spectrum of controlled parameters makes ceria on Cu(111) an interesting alternative to a more common model system ceria on Ru(0001) that has served numerous catalysis studies, mainly as a support for metal clusters.
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Affiliation(s)
- Josef Mysliveček
- Department of Surface and Plasma Science, Charles University in Prague, V Holešovičkách 2, 18000 Prague 8, Czech Republic.
| | - Vladimir Matolín
- Department of Surface and Plasma Science, Charles University in Prague, V Holešovičkách 2, 18000 Prague 8, Czech Republic.
| | - Iva Matolínová
- Department of Surface and Plasma Science, Charles University in Prague, V Holešovičkách 2, 18000 Prague 8, Czech Republic.
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11
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Photoemission Study of Methanol Adsorption and Decomposition on Pd/CeO2(111)/Cu(111) Thin Film Model Catalyst. Catal Letters 2015. [DOI: 10.1007/s10562-015-1557-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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12
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Gougis M, Pereira A, Ma D, Mohamedi M. Simultaneous deposition of cerium oxide and gold nanostructures-characterization and analytical properties toward glucose electro-oxidation and sensing. RSC Adv 2014. [DOI: 10.1039/c4ra05374e] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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13
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Neitzel A, Lykhach Y, Skála T, Tsud N, Johánek V, Vorokhta M, Prince KC, Matolín V, Libuda J. Hydrogen activation on Pt–Sn nanoalloys supported on mixed Sn–Ce oxide films. Phys Chem Chem Phys 2014; 16:13209-19. [DOI: 10.1039/c4cp01632g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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Epitaxial CeO2 thin films for a mechanism study of resistive random access memory (ReRAM). J Solid State Electrochem 2013. [DOI: 10.1007/s10008-013-2200-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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15
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Albrecht PM, Mullins DR. Adsorption and reaction of methanol over CeO(X)(100) thin films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:4559-4567. [PMID: 23484654 DOI: 10.1021/la400295f] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Methanol was adsorbed on oxidized and reduced CeOX(100) thin films to probe the active sites and reaction selectivity of these surfaces compared to those of CeOX(111). Roughly twice as much methoxy was formed on oxidized CeO2(100) compared to that formed on CeO2(111). In addition to more methoxy, hydroxyl is also more stable on CeO2(100). Unlike on CeO2(111), however, methanol on CeO2(100) produced CO, CO2, and H2 in addition to water and formaldehyde. The behavior of CeO2(100) is related to its surface structure, which provides greater access to Ce cations and therefore more active adsorption sites and more highly undercoordinated Ce and O. The undercoordinated O may explain the enhanced dehydrogenation activity leading to CO and H2 formation. The reduction of ceria leads to increased methanol uptake on both CeO2 - X(100) and CeO2 - X(111). However, although the uptake doubled on reduced CeO2 - X(111) compared to the oxidized surface, it increased by only 10% on reduced CeO2 - X(100) compared to that on fully oxidized CeO2(100). Reduction of both surfaces leads to a greater production of CO and H2. Reaction on all surfaces progresses rapidly from methoxy to products. There is no spectroscopic evidence of formyl or formate intermediates. On CeOX(100), carbonate is detected that decomposes into CO2 at high temperature.
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Affiliation(s)
- Peter M Albrecht
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6201, USA
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16
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Schernich S, Laurin M, Lykhach Y, Steinrück HP, Tsud N, Skála T, Prince KC, Taccardi N, Matolín V, Wasserscheid P, Libuda J. Functionalization of Oxide Surfaces through Reaction with 1,3-Dialkylimidazolium Ionic Liquids. J Phys Chem Lett 2013; 4:30-35. [PMID: 26291207 DOI: 10.1021/jz301856a] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Practical applications of ionic liquids (ILs) often involve IL/oxide interfaces, but little is known regarding their interfacial chemistry. The unusual physicochemical properties of ILs, including their exceptionally low vapor pressure, provide access to such interfaces using a surface science approach in ultrahigh vacuum (UHV). We have applied synchrotron radiation photoelectron spectroscopy (SR-PES) to the study of a thin film of the ionic liquid [C6C1Im][Tf2N] prepared in situ in UHV on ordered stoichiometric CeO2(111) and partially reduced CeO2-x. On the partially reduced surface, we mostly observe decomposition of the anion. On the stoichiometric CeO2(111) surface, however, a layer of surface-anchored organic products with high thermal stability is formed upon reaction of the cation. The suggested acid-base reaction pathway may provide well-defined functionalized IL/solid interfaces on basic oxides.
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Affiliation(s)
| | | | | | | | - Nataliya Tsud
- ‡Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 18000 Prague 8, Czech Republic
| | - Tomáš Skála
- ‡Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 18000 Prague 8, Czech Republic
| | - Kevin C Prince
- §Sincrotrone Trieste SCpA, Strada Statale 14, km163.5,34149 Basovizza-Trieste, Italy
| | | | - Vladimír Matolín
- ‡Faculty of Mathematics and Physics, Department of Surface and Plasma Science, Charles University, V Holešovičkách 2, 18000 Prague 8, Czech Republic
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17
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Matolín V, Matolínová I, Dvořák F, Johánek V, Mysliveček J, Prince K, Skála T, Stetsovych O, Tsud N, Václavů M, Šmíd B. Water interaction with CeO2(111)/Cu(111) model catalyst surface. Catal Today 2012. [DOI: 10.1016/j.cattod.2011.05.032] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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18
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Lykhach Y, Staudt T, Vorokhta M, Skála T, Johánek V, Prince KC, Matolín V, Libuda J. Hydrogen spillover monitored by resonant photoemission spectroscopy. J Catal 2012. [DOI: 10.1016/j.jcat.2011.09.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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19
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Tabet-Aoul A, Mohamedi M. Interrelated functionalities of hierarchically CNT/CeO2/Pt nanostructured layers: synthesis, characterization, and electroactivity. Phys Chem Chem Phys 2012; 14:4463-74. [DOI: 10.1039/c2cp24069f] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Scurtu M, Mihaiu S, Caldararu M, Zaharescu M. Surface evolution of the Sn–Ce–O powders in various atmospheres. REACTION KINETICS MECHANISMS AND CATALYSIS 2011. [DOI: 10.1007/s11144-011-0394-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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21
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Skála T, Tsud N, Prince KC, Matolín V. Interaction of tungsten with CeO2(111) layers as a function of temperature: a photoelectron spectroscopy study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:215001. [PMID: 21555841 DOI: 10.1088/0953-8984/23/21/215001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The interaction of tungsten with CeO(2)(111) layers grown on Cu(111) was studied in the temperature range between 300 and 870 K by photoelectron spectroscopy of the core levels and resonant valence band spectroscopy. The interaction was found to be very strong even at 300 K, leading to the formation of cerium tungstate Ce(6)WO(12) in which the metal atoms were in Ce(3+) and W(6+) chemical states. The growth was limited by the diffusion of W atoms into the ceria layer, so subsequent tungsten deposition led to formation of W suboxides with consecutively lower chemical oxidation states, i.e. W(4+), W(2+) and metallic W(0) with an almost negligible contribution of W(5+). Step-wise annealing of the layer showed that due to stimulated diffusion of tungsten into ceria at higher temperature, Ce(6)WO(12) was formed more easily. Larger W overlayer thicknesses needed higher annealing temperature to promote diffusion. The thickest sample studied, 1.4 nm W/CeO(2), was transformed by annealing to 870 K to the Ce(6)WO(12)/W system with a tungsten monoxide (WO) interface, whereas the rest of the tungsten was converted to the W(6 + ) oxidation state.
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Affiliation(s)
- T Skála
- Sincrotrone Trieste SCpA, Strada Statale 14, Basovizza (TS), Italy.
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22
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Vayssilov GN, Lykhach Y, Migani A, Staudt T, Petrova GP, Tsud N, Skála T, Bruix A, Illas F, Prince KC, Matolín V, Neyman KM, Libuda J. Support nanostructure boosts oxygen transfer to catalytically active platinum nanoparticles. NATURE MATERIALS 2011; 10:310-315. [PMID: 21423188 DOI: 10.1038/nmat2976] [Citation(s) in RCA: 459] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 01/27/2011] [Indexed: 05/30/2023]
Abstract
Interactions of metal particles with oxide supports can radically enhance the performance of supported catalysts. At the microscopic level, the details of such metal-oxide interactions usually remain obscure. This study identifies two types of oxidative metal-oxide interaction on well-defined models of technologically important Pt-ceria catalysts: (1) electron transfer from the Pt nanoparticle to the support, and (2) oxygen transfer from ceria to Pt. The electron transfer is favourable on ceria supports, irrespective of their morphology. Remarkably, the oxygen transfer is shown to require the presence of nanostructured ceria in close contact with Pt and, thus, is inherently a nanoscale effect. Our findings enable us to detail the formation mechanism of the catalytically indispensable Pt-O species on ceria and to elucidate the extraordinary structure-activity dependence of ceria-based catalysts in general.
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Lykhach Y, Staudt T, Tsud N, Skála T, Prince KC, Matolín V, Libuda J. Enhanced reactivity of Pt nanoparticles supported on ceria thin films during ethylenedehydrogenation. Phys Chem Chem Phys 2011; 13:253-61. [DOI: 10.1039/c0cp00345j] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Matolín V, Matolínová I, Václavů M, Khalakhan I, Vorokhta M, Fiala R, Pis I, Sofer Z, Poltierová-Vejpravová J, Mori T, Potin V, Yoshikawa H, Ueda S, Kobayashi K. Platinum-doped CeO2 thin film catalysts prepared by magnetron sputtering. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:12824-12831. [PMID: 20608706 DOI: 10.1021/la100399t] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The interaction of Pt with CeO(2) layers was investigated by using photoelectron spectroscopy. The 30 nm thick Pt doped CeO(2) layers were deposited simultaneously by rf-magnetron sputtering on a Si(001) substrate, multiwall carbon nanotubes (CNTs) supported by a carbon diffusion layer of a polymer membrane fuel cell and on CNTs grown on the silicon wafer by the CVD technique. The synchrotron radiation X-ray photoelectron spectra showed the formation of cerium oxide with completely ionized Pt(2+,4+) species, and with the Pt(2+)/Pt(4+) ratio strongly dependent on the substrate. The TEM and XRD study showed the Pt(2+)/Pt(4+) ratio is dependent on the film structure.
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Affiliation(s)
- V Matolín
- Charles University, Faculty of Mathematics and Physics, Department of Surface and Plasma Science V Holesovickách 2, 18000 Prague 8, Czech Republic.
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Matolín V, Khalakhan I, Matolínová I, Václavů M, Veltruská K, Vorokhta M. Pt2 + , 4+ ions in CeO2 rf-sputtered thin films. SURF INTERFACE ANAL 2010. [DOI: 10.1002/sia.3327] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Matolín V, Matolínová I, Sedlácek L, Prince KC, Skála T. A resonant photoemission applied to cerium oxide based nanocrystals. NANOTECHNOLOGY 2009; 20:215706. [PMID: 19423945 DOI: 10.1088/0957-4484/20/21/215706] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Cerium 4f level occupation determines the properties of cerium oxide based catalysts in a significant way. The Ce 4f level of nanosized cerium oxide particles was investigated with the use of resonant photoelectron spectroscopy in the Ce 4d-4f photoabsorption region. A strong interaction of ceria with different additives, e.g. Pd and Sn, led to a partial Ce4+-->Ce3+ transition that was observed as a significant resonance enhancement of 4f photoemission intensity. Increases of the CO oxidation catalytic activity were observed simultaneously. The ratio of resonance enhancement of Ce photoemission intensity DCe(3+)/DCe(4+) was used to monitor Ce(3+) and Ce(4+) state occupation. The relative parameter DCe(3+)/DCe(4+) was found to be particularly useful in the case of photoemission studies of nanopowder ceria catalysts.
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Affiliation(s)
- V Matolín
- Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University in Prague, Prague 8, Czech Republic.
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Skála T, Sutara F, Skoda M, Prince KC, Matolín V. Palladium interaction with CeO(2), Sn-Ce-O and Ga-Ce-O layers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:055005. [PMID: 21817292 DOI: 10.1088/0953-8984/21/5/055005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Using photoemission, we have studied the interaction of palladium with thin layers of stoichiometric ceria (Ce(4+) character) and two mixed oxides, Ga-Ce-O and Sn-Ce-O, where cerium in the Ce(3+) oxidation state is present. Palladium was found to partially reduce the CeO(2) layer by introducing oxygen vacancies most probably in the vicinity of the growing Pd particles. In mixed oxide systems palladium very strongly interacts with both added metals-gallium and tin-leading to a breaking of metal-ceria bonds and the establishment of Pd-Ga(Sn) intermetallic compounds. As a consequence the ceria reoxidizes back to a Ce(4+) oxidation state.
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Affiliation(s)
- T Skála
- Sincrotrone Trieste, Strada Statale 14, km 163.5, I-34012 Basovizza-Trieste, Italy
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Škoda M, Cabala M, Matolínová I, Prince KC, Skála T, Šutara F, Veltruská K, Matolín V. Interaction of Au with CeO2(111): A photoemission study. J Chem Phys 2009; 130:034703. [DOI: 10.1063/1.3046684] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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