Reversible changes in the Pt oxidation state and nanostructure on a ceria-based supported Pt

Hatanaka, Miho; Takahashi, Naoki; Takahashi, Naoko; Tanabe, Toshitaka; Nagai, Yasutaka; Suda, Akihiko; Shinjoh, Hirofumi

doi:10.1016/j.jcat.2009.06.005

Cited by 144 publications

(103 citation statements)

References 23 publications

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“…[10] It was found that these microstructures can be preserved during thermal aging which explains the better resistance of Pt/LaFeO 3 to deactivation in comparison with Pt/Al 2 O 3 . [10] Similar tendencies were recently reported on Pt/CeO 2 [11] with strong metal/support interactions that involve the formation of a Pt-O-Ce bond which stabilizes Pt against sintering. This study shows that the thermal sintering/redispersion processes of Pd particles on LaFeO 3 also depend on the nature of the precursors before activation thermal treatments.…”

Section: Introductionsupporting

confidence: 73%

Pd characterization by XPS in perovskite catalysts for NO_x reduction: influence of thermal aging

Miquel

Yamin

Lombaert

et al. 2010

Surface & Interface Analysis

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This study reports surface characterizations of Pd/LaFeO 3 catalysts after aging in diesel engine simulated conditions. Thermal aging and support-induced effects on the nature of Pd species were investigated. LaFeO 3 was prepared via a sol-gel method to promote relatively high specific surface area (19 m 2 g −1 ). Subsequent impregnation from solutions using Pd(NO 3 ) 2 , Pd(acac) 2 or Pd(NH 3 ) 4 (NO 3 ) 2 precursor salts was examined by means of XPS and infrared spectroscopy on pre-activated catalysts under reductive atmosphere and aged ones under reactive conditions overnight at 500• C. Both techniques reveal that the degree of Pd dispersion and the reducibility of oxidic palladium species are correlated to the oxidation state of oxidic palladium species and depend on the nature of the precursor salt. Hence, impregnated samples using Pd(NH 3 ) 4 (NO 3 ) 2 and Pd(acac) 2 precursor salts, after calcination, lead to highly dispersed Pd 4+ species strongly interacting with the support. On the other hand, it was found that both the catalysts suffer from stronger deactivation phenomena than those affecting the catalysts prepared via Pd(NO 3 ) 2 .

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Section: Introductionsupporting

confidence: 73%

Pd characterization by XPS in perovskite catalysts for NO_x reduction: influence of thermal aging

Miquel

Yamin

Lombaert

et al. 2010

Surface & Interface Analysis

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“…The latter may be associated with changes in the gas composition or, in the case of the fuel cell catalysts, in response to changes of the electrode potential. Reversible changes in the oxidation state of Pt particles supported on nanostructured ceria have previously been monitored by Hatanaka et al 154 The presence of oxidized Pt species was explained by the formation of Pt-O-Ce bonds in an oxidative atmosphere at high temperature. It was proposed that the formation of such bonds drives the redispersion of Pt particles into smaller clusters.…”

Section: Structural Flexibility Of Sub-nanometer Metal Particlesmentioning

confidence: 89%

“…It was proposed that the formation of such bonds drives the redispersion of Pt particles into smaller clusters. 155 These studies 154,155 suggested the formation of a monolayer of oxidized Pt on the surface of a ceria-based material after treatment in an oxygen atmosphere. Based on the binding energy of the corresponding species in Pt 4f spectra, we speculate that the species described in that work are similar to Pt 2+ species anchored at {100} facets described above.…”

Section: Structural Flexibility Of Sub-nanometer Metal Particlesmentioning

confidence: 99%

Oxide-based nanomaterials for fuel cell catalysis: the interplay between supported single Pt atoms and particles

Lykhach

Bruix

Fabris

et al. 2017

Catal. Sci. Technol.

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The concept of single atom catalysis offers maximum noble metal efficiency for the development of lowcost catalytic materials. Among possible applications are catalytic materials for proton exchange membrane fuel cells. In the present review, recent efforts towards the fabrication of single atom catalysts on nanostructured ceria and their reactivity are discussed in the prospect of their employment as anode catalysts.The remarkable performance and the durability of the ceria-based anode catalysts with ultra-low Pt loading result from the interplay between two states associated with supported atomically dispersed Pt and subnanometer Pt particles. The occurrence of these two states is a consequence of strong interactions between Pt and nanostructured ceria that yield atomically dispersed species under oxidizing conditions and sub-nanometer Pt particles under reducing conditions. The square-planar arrangement of four O atoms on {100} nanoterraces has been identified as the key structural element on the surface of the nanostructured ceria where Pt is anchored in the form of Pt 2+ species. The conversion of Pt 2+ species to subnanometer Pt particles is triggered by a redox process involving Ce 3+ centers. The latter emerge due to either oxygen vacancies or adsorption of reducing agents. The unique properties of the sub-nanometer Pt particles arise from metal-support interactions involving charge transfer, structural flexibility, and spillover phenomena. The abundance of specific adsorption sites similar to those on {100} nanoterraces determines the ideal (maximum) Pt loading in Pt-CeO x films that still allows reversible switching between the atomically dispersed Pt and sub-nanometer particles yielding high activity and durability during fuel cell operation.

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“…Other bands were assigned to CO adsorbed on-top on Pt in different oxidation (charge) states: Pt 2+ (2102-2120 cm In some of Pt/CeO 2 systems mononuclear Pt species were reported (no Pt-Pt bonds were detected). 31 Those Pt species were considered to be either ionic or neutral Pt atoms (in oxidation state zero). Daniel 24 assigned the bands at 2122 and 2128 cm -1 to CO on Pt 2+ and Pt 4+ , respectively.…”

Section: Introductionmentioning

confidence: 99%

Can the state of platinum species be unambiguously determined by the stretching frequency of an adsorbed CO probe molecule?

Aleksandrov

Neyman

Hadjiivanov

et al. 2016

Phys. Chem. Chem. Phys.

140

128

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Electronic Supplementary Information (ESI) available: Information includes sketches of all modeled Pt8(CO) complexes in gas phase and some of their energetic and structural characteristics, structure of e-reg/(CO)2 complex, and figure with the changes of the CO stretching frequency versus oxidation state and Bader charge of mononuclear platinum species. See DOI: 10.1039/x0xx00000x The paper addresses possible ambiguities in determination of the state of platinum species by the stretching frequency of a CO probe, which is a common technique for characterization of platinum-containing catalytic systems. We present a comprehensive comparison of the available experimental data with our theoretical modeling (density functional) results of pertinent systems -platinum surface, nanoparticles and clusters as well as reduced or oxidized platinum moieties on ceria support. Our results for CO adsorbed on-top on metallic Pt . This trend corroborates the Kappers-van der Maas correlation derived from analysis of experimental stretching frequency of CO adsorbed on platinum-containing samples on different supports. We also analyzed the effect of the charge of platinum species on the CO frequency. Based on the calculated vibrational frequencies of CO in various model systems, we concluded that the actual state of the platinum species may be mistaken based only on the measured value of the C-O vibrational frequency due to overlapping regions of frequencies corresponding to different types of species. In order to identify the actual state of platinum species one has to combine this powerful technique with other approaches.

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Reversible changes in the Pt oxidation state and nanostructure on a ceria-based supported Pt

Cited by 144 publications

References 23 publications

Pd characterization by XPS in perovskite catalysts for NO_x reduction: influence of thermal aging

Pd characterization by XPS in perovskite catalysts for NO_x reduction: influence of thermal aging

Oxide-based nanomaterials for fuel cell catalysis: the interplay between supported single Pt atoms and particles

Can the state of platinum species be unambiguously determined by the stretching frequency of an adsorbed CO probe molecule?

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Reversible changes in the Pt oxidation state and nanostructure on a ceria-based supported Pt

Cited by 144 publications

References 23 publications

Pd characterization by XPS in perovskite catalysts for NOx reduction: influence of thermal aging

Pd characterization by XPS in perovskite catalysts for NOx reduction: influence of thermal aging

Oxide-based nanomaterials for fuel cell catalysis: the interplay between supported single Pt atoms and particles

Can the state of platinum species be unambiguously determined by the stretching frequency of an adsorbed CO probe molecule?

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Product

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Pd characterization by XPS in perovskite catalysts for NO_x reduction: influence of thermal aging

Pd characterization by XPS in perovskite catalysts for NO_x reduction: influence of thermal aging