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D. Duprez - One of the best experts on this subject based on the ideXlab platform.
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ceria supported au cuo and au co3o4 catalysts for co oxidation an 18o 16o Isotopic Exchange study
Applied Catalysis B-environmental, 2015Co-Authors: Nadiakarina Gamboarosales, Nicolas Bion, D. Duprez, J L Ayastuy, Zouhair Boukha, J A Perezomil, E Del Rio, M A GutierrezortizAbstract:Abstract In this work Isotopic Exchange of 18 O 2 with 16 O and oxidation of C 16 O were investigated at 130 °C on ceria-supported Au–CuO and Au–Co 3 O 4 catalysts. Oxygen storage capacity (OSC) was measured at 400 °C to check the influence of the metals in the catalysts, resulting in an enhancement of OSC for gold-containing catalysts compared to monometallic catalysts. The reactivity of surface oxygen atoms and the oxygen availability from the samples were studied by two isothermal experiments, both feeding C 16 O (anaerobic oxidation C 16 O/Ar and aerobic oxidation C 16 O/O 2 ) to the 18 O pre-Exchanged samples. Exchange leads to C 18 O formation and oxidation leads to C 16 O 2 , C 16 O 18 O and C 18 O 2 formation. In anaerobic conditions the predominant reaction at the beginning is the Exchange: a rapid Exchange of C 16 O with the surface can be observed for all the samples except for CoCe that inhibits the Exchange and the CO oxidation. In aerobic conditions, the predominant reaction is CO oxidation with the rapid increase of C 16 O 2 due to the relatively high 16 O coverage in reaction as a result of the C 16 O Exchange and from Exchange between 18 O surface species and 16 O bulk atoms. At 130 °C, bare ceria shows null activity in both aerobic and anaerobic oxidation.
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a study of 15n 14n Isotopic Exchange over cobalt molybdenum nitrides
ACS Catalysis, 2013Co-Authors: Stuart M Hunter, D. Duprez, Duncan H Gregory, J S J Hargreaves, Melissandre Richard, Nicolas BionAbstract:The 14N/15N Isotopic Exchange pathways over Co3Mo3N, a material of interest as an ammonia synthesis catalyst and for the development of nitrogen transfer reactions, have been investigated. Both the homomolecular and heterolytic Exchange processes have been studied, and it has been shown that lattice nitrogen species are Exchangeable. The Exchange behavior was found to be a strong function of pretreatment with ca. 25% of lattice N atoms being Exchanged after 40 min at 600 °C after N2 pretreatment at 700 °C compared to only 6% following similar Ar pretreatment. This observation, for which the potential contribution of adsorbed N species can be discounted, is significant in terms of the application of this material. In the case of the Co6Mo6N phase, regeneration to Co3Mo3N under 15N2 at 600 °C occurs concurrently with 14N15N formation. These observations demonstrate the reactivity of nitrogen in the Co–Mo–N system to be a strong function of pretreatment and worthy of further consideration.
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direct evidence of the role of dispersed ceria on the activation of oxygen in nax zeolite by coupling the 17o 16o Isotopic Exchange and 17o solid state nmr
Journal of Catalysis, 2013Co-Authors: Irene Maupin, D. Duprez, Jerome Mijoin, T Belin, Claudia Morais, Valerie Montouillout, Nicolas BionAbstract:Abstract The possibility to understand the phenomena of oxygen diffusion in the solids may be decisive to explain the role of framework oxygen atoms in a catalytic mechanism or in catalyst regeneration steps. In this work, two highly efficient characterization techniques have been associated: the 17 O/ 16 O Isotopic Exchange and the 17 O high field solid-state NMR spectroscopy. This combination leads to a powerful tool to investigate the interaction between gaseous dioxygen molecule and lattice oxygen atoms. Here, it permits to demonstrate the enhancement of the participation of zeolitic oxygen atoms in the Exchange with the gas phase when ceria is simply mixed with NaX.
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study of surface reaction mechanisms by 16o 18o and h d Isotopic Exchange
Catalysis Today, 2006Co-Authors: D. DuprezAbstract:Abstract Surface diffusion of active species is a general phenomenon in catalysis: rates of migration often being much higher than turnover frequencies of reaction, surface species can migrate and visit a great number of active sites in between two successive catalytic cycles. 16O/18O and H/D Isotopic Exchange is a very useful technique to elucidate reaction mechanisms involving mobility steps of O- and H-containing reactive species. The method is based on the measurement of the rates of Exchange between gaseous 18O2 (or D2) and 16O species (or OH) species of the support via metal particles, small metallic clusters acting as porthole of O or H on the support. Simple kinetic models allow to calculate surface and bulk diffusivities on the oxide used as support. As a rule, a significant O mobility can only be observed above 200 °C for most oxides. Furthermore, very great differences of diffusivity (five orders of magnitude) are recorded between silica (on which OH groups are virtually immobile) and oxides like ceria exhibiting a very high oxygen mobility. Differences of diffusivity (two orders of magnitude) are much less for hydrogen than for oxygen. This method can give useful information about reactions catalyzed by metal/oxide systems in which surface diffusion can play a decisive role in the mechanism: steam reforming, water gas shift, hydrocarbon oxidation, aromatic hydrogenation, methanol synthesis, coke formation). For oxides such as CexZr1−xO2 mixed oxides, O mobility is so high that surface and bulk mobility can no longer be distinguished. More complex kinetic models requiring computer simulation of all the steps of adsorption, desorption, diffusion and Exchange simultaneously have been developed.
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characterization of the dynamic oxygen migration over pt ceo2 zro2 catalysts by 18o 16o Isotopic Exchange reaction
Catalysis Today, 2004Co-Authors: Fei Dong, C. Descorme, Akihiko Suda, Toshitaka Tanabe, Yasutaka Nagai, Hideo Sobukawa, H Shinjoh, Masahiro Sugiura, D. DuprezAbstract:Abstract To characterize the oxygen mobility over metal supported catalysts on a dynamic and in situ base, 18 O / 16 O Isotopic Exchange reaction combined with CO oxidation was designed and exemplified on three kinds of three way catalysts of Pt/CeO2-ZrO2 (CZ-O, CZ-D and CZ-R). The obtained oxygen diffusion coefficients, oxygen release rate, and oxygen storage capacity were discussed and correlated with XRD spectra and other physical parameters. It was found that the oxygen mobility and oxygen storage capacity were parallel to the structural homogeneity of Zr introduction into the CeO2 frame work, and decreased as: CZ-R > CZ-D > CZ-O. These results indicated that this combined Isotopic Exchange technique could be used to quantify the surface and bulk oxygen mobility, the oxygen storage capacity and oxygen release rate over the metal supported catalysts, and could be employed as a meaningful probe into the nature of CeO2-ZrO2 oxygen storage material. The oxygen mobility is also another important indicator for the development of oxygen storage materials.
Nicolas Bion - One of the best experts on this subject based on the ideXlab platform.
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Operando Isotopic Exchange on SOFC cells: oxygen transport dependency on applied potential
ChemPhysChem, 2020Co-Authors: Alexandre Nau, Clément Comminges, Nicolas BionAbstract:The oxygen Isotopic Exchange technique is a powerful tool to investigate the oxygen transport kinetics in an oxide solid. In a solid oxide fuel cell, Isotopic surface Exchange and diffusion coefficients are classically determined by using the Isotopic Exchange Depth Profiling method followed by ex situ SIMS characterizations. Despite its relevance, the utilization of in situ or operando techniques to measure the Isotopic Exchange under an electrical bias remains marginal. We developed here a setup which enables operando monitoring of oxygen Exchange in SOFC type cells under polarization. The system has been used for studying the oxygen mobility dependency upon polarization on a symmetrical Pt/YSZ/Pt cell. Homomolecular and heterolytic Exchange reactions were undertaken to investigate the oxygen activation step and discriminate the limiting step among the sequence of elementary steps which constitute the oxygen transport process in the SOFC system. Oxygen ions incorporation into the dense ionic conductor was identified to be the rate determining step, and its first order rate constant dependency on applied potential was established.
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ceria supported au cuo and au co3o4 catalysts for co oxidation an 18o 16o Isotopic Exchange study
Applied Catalysis B-environmental, 2015Co-Authors: Nadiakarina Gamboarosales, Nicolas Bion, D. Duprez, J L Ayastuy, Zouhair Boukha, J A Perezomil, E Del Rio, M A GutierrezortizAbstract:Abstract In this work Isotopic Exchange of 18 O 2 with 16 O and oxidation of C 16 O were investigated at 130 °C on ceria-supported Au–CuO and Au–Co 3 O 4 catalysts. Oxygen storage capacity (OSC) was measured at 400 °C to check the influence of the metals in the catalysts, resulting in an enhancement of OSC for gold-containing catalysts compared to monometallic catalysts. The reactivity of surface oxygen atoms and the oxygen availability from the samples were studied by two isothermal experiments, both feeding C 16 O (anaerobic oxidation C 16 O/Ar and aerobic oxidation C 16 O/O 2 ) to the 18 O pre-Exchanged samples. Exchange leads to C 18 O formation and oxidation leads to C 16 O 2 , C 16 O 18 O and C 18 O 2 formation. In anaerobic conditions the predominant reaction at the beginning is the Exchange: a rapid Exchange of C 16 O with the surface can be observed for all the samples except for CoCe that inhibits the Exchange and the CO oxidation. In aerobic conditions, the predominant reaction is CO oxidation with the rapid increase of C 16 O 2 due to the relatively high 16 O coverage in reaction as a result of the C 16 O Exchange and from Exchange between 18 O surface species and 16 O bulk atoms. At 130 °C, bare ceria shows null activity in both aerobic and anaerobic oxidation.
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a study of 15n 14n Isotopic Exchange over cobalt molybdenum nitrides
ACS Catalysis, 2013Co-Authors: Stuart M Hunter, D. Duprez, Duncan H Gregory, J S J Hargreaves, Melissandre Richard, Nicolas BionAbstract:The 14N/15N Isotopic Exchange pathways over Co3Mo3N, a material of interest as an ammonia synthesis catalyst and for the development of nitrogen transfer reactions, have been investigated. Both the homomolecular and heterolytic Exchange processes have been studied, and it has been shown that lattice nitrogen species are Exchangeable. The Exchange behavior was found to be a strong function of pretreatment with ca. 25% of lattice N atoms being Exchanged after 40 min at 600 °C after N2 pretreatment at 700 °C compared to only 6% following similar Ar pretreatment. This observation, for which the potential contribution of adsorbed N species can be discounted, is significant in terms of the application of this material. In the case of the Co6Mo6N phase, regeneration to Co3Mo3N under 15N2 at 600 °C occurs concurrently with 14N15N formation. These observations demonstrate the reactivity of nitrogen in the Co–Mo–N system to be a strong function of pretreatment and worthy of further consideration.
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direct evidence of the role of dispersed ceria on the activation of oxygen in nax zeolite by coupling the 17o 16o Isotopic Exchange and 17o solid state nmr
Journal of Catalysis, 2013Co-Authors: Irene Maupin, D. Duprez, Jerome Mijoin, T Belin, Claudia Morais, Valerie Montouillout, Nicolas BionAbstract:Abstract The possibility to understand the phenomena of oxygen diffusion in the solids may be decisive to explain the role of framework oxygen atoms in a catalytic mechanism or in catalyst regeneration steps. In this work, two highly efficient characterization techniques have been associated: the 17 O/ 16 O Isotopic Exchange and the 17 O high field solid-state NMR spectroscopy. This combination leads to a powerful tool to investigate the interaction between gaseous dioxygen molecule and lattice oxygen atoms. Here, it permits to demonstrate the enhancement of the participation of zeolitic oxygen atoms in the Exchange with the gas phase when ceria is simply mixed with NaX.
D. Duprez - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the dynamic oxygen migration over Pt/CeO2-ZrO2 catalysts by O-18/O-16 Isotopic Exchange reaction
Catalysis Today, 2004Co-Authors: Fei Dong, Akihiko Suda, Toshitaka Tanabe, Yasutaka Nagai, Hideo Sobukawa, H Shinjoh, A. Sugiura, C. Descorme, D. DuprezAbstract:To characterize the oxygen mobility over metal supported catalysts on a dynamic and in situ base, O-18/O-16 Isotopic Exchange reaction combined with CO oxidation was designed and exemplified on three kinds of three way catalysts of Pt/CeO2-ZrO2 (CZ-O, CZ-D and CZ-R). The obtained oxygen diffusion coefficients, oxygen release rate, and oxygen storage capacity were discussed and correlated with XRD spectra and other physical parameters. It was found that the oxygen mobility and oxygen storage capacity were parallel to the structural homogeneity of Zr introduction into the CeO2 frame work, and decreased as: CZ-R > CZ-D > CZ-O. These results indicated that this combined Isotopic Exchange technique could be used to quantify the surface and bulk oxygen mobility, the oxygen storage capacity and oxygen release rate over the metal supported catalysts, and could be employed as a meaningful probe into the nature of CeO2-ZrO2 oxygen storage material. The oxygen mobility is also another important indicator for the development of oxygen storage materials. (C) 2004 Elsevier B.V. All rights reserved.
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A novel dynamic kinetic model of oxygen Isotopic Exchange on a supported metal catalyst
Applied Surface Science, 2004Co-Authors: A. Galdikas, D. Duprez, C. DescormeAbstract:A time-resolved kinetic analysis has been developed for modeling experimental results of (18)O/(16)O Isotopic Exchange over oxide-supported metal catalysts. Model is based on two very important points: (1) the parallel calculation of surface and bulk diffusion and (2) the implication of certain 0 species such as superoxides. The model includes adsorption-desorption processes on metal clusters and oxygen spillover from the metal to the surface of support and vice versa. Different mechanisms of Exchange were also taken into account via mononuclear (O atoms, O(-), OB) or binuclear (superoxides) oxygen species. A refined model taking into account surface diffusion, direct Exchange on surface of support by binuclear oxygen species and bulk diffusion was also developed. Kinetic (reaction rates and diffusion coefficients) as well as thermodynamic parameters (activation energies) were derived by fitting theoretical and experimental curves of (18)O(2), (18)O(18)O and (16)O(2) gas phase concentrations versus time. The experimental results of Pt/CeZrO(2) catalyst samples obtained in the 200-450 degreesC range of temperatures are examined. The refined model provides a very good fitting of the kinetic curves recorded with ceria-zirconia-supported catalysts. Moreover, values of diffusion coefficients and activation energies are in good agreement with already published values found by other methods. For a better understanding of all the steps of Exchange, the kinetics of 180 and 160 distribution on the surface of metal clusters and on the surface of support are calculated and analyzed. On the basis of this model, a computer code is developed for analysis and calculations of kinetic and thermodynamic parameters of automotive catalysts. (C) 2004 Elsevier B.V. All rights reserved.
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Oxygen surface mobility and Isotopic Exchange on oxides: role of the nature and the structure of metal particles
Applied Catalysis A : General, 2000Co-Authors: C. Descorme, D. DuprezAbstract:Oxygen surface mobility on oxides-supported metals has been studied for many years in our laboratory. The first step of the process is the activation of the oxygen molecule on the metal particle. Measurements of the kinetics of the adsorption-desorption of oxygen on metal surfaces were possible by the way of Isotopic Exchange studies. The influence of the nature of the metal, of the accessibility of the metal, of the oxide support are reviewed. (C) 2000 Elsevier Science B.V. All rights reserved.
C. Descorme - One of the best experts on this subject based on the ideXlab platform.
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characterization of the dynamic oxygen migration over pt ceo2 zro2 catalysts by 18o 16o Isotopic Exchange reaction
Catalysis Today, 2004Co-Authors: Fei Dong, C. Descorme, Akihiko Suda, Toshitaka Tanabe, Yasutaka Nagai, Hideo Sobukawa, H Shinjoh, Masahiro Sugiura, D. DuprezAbstract:Abstract To characterize the oxygen mobility over metal supported catalysts on a dynamic and in situ base, 18 O / 16 O Isotopic Exchange reaction combined with CO oxidation was designed and exemplified on three kinds of three way catalysts of Pt/CeO2-ZrO2 (CZ-O, CZ-D and CZ-R). The obtained oxygen diffusion coefficients, oxygen release rate, and oxygen storage capacity were discussed and correlated with XRD spectra and other physical parameters. It was found that the oxygen mobility and oxygen storage capacity were parallel to the structural homogeneity of Zr introduction into the CeO2 frame work, and decreased as: CZ-R > CZ-D > CZ-O. These results indicated that this combined Isotopic Exchange technique could be used to quantify the surface and bulk oxygen mobility, the oxygen storage capacity and oxygen release rate over the metal supported catalysts, and could be employed as a meaningful probe into the nature of CeO2-ZrO2 oxygen storage material. The oxygen mobility is also another important indicator for the development of oxygen storage materials.
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surface diffusion upon oxygen Isotopic Exchange on oxide supported metal nanoclusters
Solid State Ionics, 2004Co-Authors: A. Galdikas, C. Descorme, D. DuprezAbstract:Abstract A newly developed real-time kinetic model is presented. The model was used for the characterization of supported metal catalysts' properties in the oxygen Isotopic Exchange reaction. This model is based on rate equations and includes several elementary processes: adsorption on the metal nanoclusters, reactions on the metal nanoclusters, desorption from the metal nanoclusters, surface and bulk diffusion on/in the oxide support and direct Exchange with the gas phase. On the basis of this model, a computer code was developed to determine the kinetic and thermodynamic parameters of the oxygen Isotopic Exchange reactions. The characteristics of a Rh/CeO2 catalyst were examined in the temperature range between 200 and 450 °C.
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Surface diffusion upon oxygen Isotopic Exchange on oxide-supported metal nanoclusters
Solid State Ionics, 2004Co-Authors: A. Galdikas, C. Descorme, D. DuprezAbstract:A newly developed real-time kinetic model is presented. The model was used for the characterization of supported metal catalysts' properties in the oxygen Isotopic Exchange reaction. This model is based on rate equations and includes several elementary processes: adsorption on the metal nanoclusters, reactions on the metal nanoclusters, desorption from the metal nanoclusters, surface and bulk diffusion on/in the oxide support and direct Exchange with the gas phase. On the basis of this model, a computer code was developed to determine the kinetic and thermodynamic parameters of the oxygen Isotopic Exchange reactions. The characteristics of a Rh/CeO2 catalyst were examined in the temperature range between 200 and 450 degreesC. (C) 2003 Elsevier B.V. All rights reserved.
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oxygen surface mobility and Isotopic Exchange on oxides role of the nature and the structure of metal particles
Applied Catalysis A-general, 2000Co-Authors: C. Descorme, D. DuprezAbstract:Abstract Oxygen surface mobility on oxides-supported metals has been studied for many years in our laboratory. The first step of the process is the activation of the oxygen molecule on the metal particle. Measurements of the kinetics of the adsorption–desorption of oxygen on metal surfaces were possible by the way of Isotopic Exchange studies. The influence of the nature of the metal, of the accessibility of the metal, of the oxide support are reviewed.
C. Descorme - One of the best experts on this subject based on the ideXlab platform.
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Characterization of the dynamic oxygen migration over Pt/CeO2-ZrO2 catalysts by O-18/O-16 Isotopic Exchange reaction
Catalysis Today, 2004Co-Authors: Fei Dong, Akihiko Suda, Toshitaka Tanabe, Yasutaka Nagai, Hideo Sobukawa, H Shinjoh, A. Sugiura, C. Descorme, D. DuprezAbstract:To characterize the oxygen mobility over metal supported catalysts on a dynamic and in situ base, O-18/O-16 Isotopic Exchange reaction combined with CO oxidation was designed and exemplified on three kinds of three way catalysts of Pt/CeO2-ZrO2 (CZ-O, CZ-D and CZ-R). The obtained oxygen diffusion coefficients, oxygen release rate, and oxygen storage capacity were discussed and correlated with XRD spectra and other physical parameters. It was found that the oxygen mobility and oxygen storage capacity were parallel to the structural homogeneity of Zr introduction into the CeO2 frame work, and decreased as: CZ-R > CZ-D > CZ-O. These results indicated that this combined Isotopic Exchange technique could be used to quantify the surface and bulk oxygen mobility, the oxygen storage capacity and oxygen release rate over the metal supported catalysts, and could be employed as a meaningful probe into the nature of CeO2-ZrO2 oxygen storage material. The oxygen mobility is also another important indicator for the development of oxygen storage materials. (C) 2004 Elsevier B.V. All rights reserved.
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A novel dynamic kinetic model of oxygen Isotopic Exchange on a supported metal catalyst
Applied Surface Science, 2004Co-Authors: A. Galdikas, D. Duprez, C. DescormeAbstract:A time-resolved kinetic analysis has been developed for modeling experimental results of (18)O/(16)O Isotopic Exchange over oxide-supported metal catalysts. Model is based on two very important points: (1) the parallel calculation of surface and bulk diffusion and (2) the implication of certain 0 species such as superoxides. The model includes adsorption-desorption processes on metal clusters and oxygen spillover from the metal to the surface of support and vice versa. Different mechanisms of Exchange were also taken into account via mononuclear (O atoms, O(-), OB) or binuclear (superoxides) oxygen species. A refined model taking into account surface diffusion, direct Exchange on surface of support by binuclear oxygen species and bulk diffusion was also developed. Kinetic (reaction rates and diffusion coefficients) as well as thermodynamic parameters (activation energies) were derived by fitting theoretical and experimental curves of (18)O(2), (18)O(18)O and (16)O(2) gas phase concentrations versus time. The experimental results of Pt/CeZrO(2) catalyst samples obtained in the 200-450 degreesC range of temperatures are examined. The refined model provides a very good fitting of the kinetic curves recorded with ceria-zirconia-supported catalysts. Moreover, values of diffusion coefficients and activation energies are in good agreement with already published values found by other methods. For a better understanding of all the steps of Exchange, the kinetics of 180 and 160 distribution on the surface of metal clusters and on the surface of support are calculated and analyzed. On the basis of this model, a computer code is developed for analysis and calculations of kinetic and thermodynamic parameters of automotive catalysts. (C) 2004 Elsevier B.V. All rights reserved.
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Oxygen surface mobility and Isotopic Exchange on oxides: role of the nature and the structure of metal particles
Applied Catalysis A : General, 2000Co-Authors: C. Descorme, D. DuprezAbstract:Oxygen surface mobility on oxides-supported metals has been studied for many years in our laboratory. The first step of the process is the activation of the oxygen molecule on the metal particle. Measurements of the kinetics of the adsorption-desorption of oxygen on metal surfaces were possible by the way of Isotopic Exchange studies. The influence of the nature of the metal, of the accessibility of the metal, of the oxide support are reviewed. (C) 2000 Elsevier Science B.V. All rights reserved.