Some recent results on metal/support interaction effects in NM/CeO2 (NM: noble metal) catalysts

Bernal, S.; Calvino, José J.; Cauqui, M.A.; Gatica, José M.; Larese, C.; Pérez-Omil, Jose A.; Pintado, José

doi:10.1016/s0920-5861(98)00503-3

Cited by 439 publications

(315 citation statements)

References 180 publications

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“…On the other hand, the reversal of the S MSI state has been observed after CO hydrogenation reactions on Pt/TiO 2 [10,11]. Also, partial recovering of CO uptake (as a test for the metal encapsulation) upon oxidative treatments of Pt/TiO 2 (110) and Pt/CeO 2 (111) model catalysts has been reported [12,13]. Reversible wetting-dewetting behaviour induced by ambient conditions has recently been demonstrated by in situ STM on vanadia overlayer on Pd(111) [14].…”

Section: Introductionmentioning

confidence: 95%

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Sun

Qin

Lewandowski

et al. 2009

Journal of Catalysis

219

236

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Abstract. CO oxidation on a clean Pt(111) single crystal and thin iron oxide films grown on Pt(111) was studied at different CO:O 2 ratios (between 1:5 and 5:1) and partial pressures up to 60 mbar at 400 -450 K. Structural characterization of the model catalysts was performed by scanning tunneling microscopy, low energy electron diffraction, Auger electron spectroscopy and temperature programmed desorption. It is found that monolayer FeO (111) films grown on Pt(111) are much more active than clean Pt(111) and nm-thick Fe 3 O 4 (111) films at all reaction conditions studied. Post-characterization of the catalysts revealed that at CO:O 2 >1 the FeO(111) film dewets the Pt surface with time, ultimately resulting in highly dispersed iron oxide particles on Pt(111). The film dewetting was monitored in situ by polarisation-modulated infrared reflection absorption spectroscopy. The reaction rate at 450 K exhibited first order for O 2 and non-monotonously depended on CO pressure. In O 2 -rich ambient the films were enriched with oxygen while maintaining the long range ordering.Based on the structure-reactivity relationships observed for the FeO/Pt films, we propose that the reaction proceeds through the formation of a well-ordered, oxygen-rich FeO x (1 < x < 2) film that reacts with CO through the redox mechanism. The reaction induced dewetting in fact deactivates the catalyst. The results may aid in our deeper understanding of reactivity of metal particles encapsulated by thin oxide films as a result of strong metal support interaction.

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Section: Introductionmentioning

confidence: 95%

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Sun

Qin

Lewandowski

et al. 2009

Journal of Catalysis

219

236

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“…This phenomenon, the so-called strong metal-support interaction (SMSI) effect, has been explained as due to both geometric and electronic effects. Particularly, electronic effects prevail after reduction at temperatures below 773 K on M-CeO 2 systems, while at higher temperatures geometric effects, caused by migration of partially reduced CeO 2-x species from the support to the metal particle surface, seem to be more important [6].…”

Section: Introductionmentioning

confidence: 98%

Effect of the presence of chlorine in bimetallic PtZn/CeO2 catalysts for the vapor-phase hydrogenation of crotonaldehyde

Silvestre-Albero

Coloma

Sepúlveda-Escribano

et al. 2006

Applied Catalysis A: General

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The effect of the reduction temperature has been studied on ceria-supported bimetallic platinum-zinc catalysts prepared from H 2 PtCl 6 and Pt(NH 3 ) 4 (NO 3 ) 2 as the platinum precursors and Zn(NO 3 ) 2 as the zinc precursor. The catalysts have been characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS), and their catalytic behavior has been evaluated in the vapor-phase hydrogenation of toluene and of crotonaldehyde (2-butenal) after reduction at low (473 K) and high (773 K) temperatures. The increase in the reduction temperature produces a strong decrease in the catalytic activity for toluene hydrogenation in both systems, but an important increase of activity for crotonaldehyde hydrogenation, which is more evident for the chlorine-free catalyst. The selectivity towards the hydrogenation of the carbonyl bond to yield the unsaturated alcohol (crotyl alcohol, 2-buten-1-ol) also increases after reduction at high temperature, being somewhat higher for the Cl-containing catalyst. The results are discussed in terms of differences in surface composition of the catalysts.

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“…6 The formation of the Pt 5 Ce alloy was also detected by Bernal et al for Pt/CeO 2 samples reduced at 1173 K. 7 The hypothesis that the real catalytic site results from the interaction of platinum with the support surface found experimental evidence in the work of Fu et al, who observed that Pt supported on ceria continued to be active for the water gas-shift reaction also after leaching the metal phase by CN -and concluded that the catalytic sites are constituted by Pt 2+ and Pt 4+ species atomically dispersed in the oxide matrix. 10 The possibility that some kind of strong metal-support interaction (SMSI) is operative in TWCs and affects the catalytic properties was put forth by different authors, 2,3,[11][12][13] although there is not a general agreement about the beneficial or detrimental effect of such an interaction. Aiming at a structural characterization of the metal-support interface, we carried out in situ XAS experiments on the Pt L III edge of a Pt/ceria-zirconia catalyst.…”

Section: Introductionmentioning

confidence: 99%

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

Deganello¹,

Giannici²,

Martorana³

et al. 2006

J. Phys. Chem. B

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The catalyst Pt(1 wt %)/Ce 0.6 Zr 0.4 O 2 is studied by CO-temperature programmed reduction (CO-TPR), isothermal oxygen storage complete capacity (OSCC), X-ray absorption spectroscopy (XAS) at the Pt L III edge, and in situ X-ray diffraction (in situ XRD), with the aim of elucidating the role of supported metal in CO oxidation by ceria-based three-way catalysts (TWC). The redox behavior of Pt(1 wt %)/Ce 0.6 Zr 0.4 O 2 is compared to that of bare ceria-zirconia. OSCC of redox-aged Pt/ceria-zirconia is twice that of bare ceria-zirconia, and the maximum of CO consumption occurs at a temperature about 300 K lower than redox-aged ceria-zirconia. XAS analysis allows one to evidence the formation of a platinum-cerium alloy in redox-aged samples and the stability of the metal particles toward oxidation and sintering during high-temperature treatments. Under CO flux at 773 K, bare ceria-zirconia shows a continuous drift of diffraction peaks toward smaller Bragg angles, due to a progressive increase of Ce(III) content. Under the same treatment, the structural rearrangement of Pt-supported ceria-zirconia starts after an induction time and takes place with an abrupt change of the lattice constant. The experimental evidence points to the role of supported Pt in modifying the redox properties of ceria-zirconia with respect to the bare support. It is proposed that the much faster bulk reduction observed by in situ XRD for redox-aged Pt/ceria-zirconia can be attributed to an easier release of reacted CO 2 , producing a more effective turnover of reactants at the catalyst surface.

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Some recent results on metal/support interaction effects in NM/CeO2 (NM: noble metal) catalysts

Cited by 439 publications

References 180 publications

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Effect of the presence of chlorine in bimetallic PtZn/CeO2 catalysts for the vapor-phase hydrogenation of crotonaldehyde

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂

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Some recent results on metal/support interaction effects in NM/CeO2 (NM: noble metal) catalysts

Cited by 439 publications

References 180 publications

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Monolayer iron oxide film on platinum promotes low temperature CO oxidation

Effect of the presence of chlorine in bimetallic PtZn/CeO2 catalysts for the vapor-phase hydrogenation of crotonaldehyde

Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce0.6Zr0.4O2

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Metal−Support Interaction and Redox Behavior of Pt(1 wt %)/Ce_0.6Zr_0.4O₂