Influence of Supported Gold on the Dynamics of Reduction and Crystallization of Iron Oxides: A Dispersive X-ray Absorption Near Edge Structure Spectroscopy and X-ray Diffraction Study

Jimenez‐Lam, Sergio A.; Cárdenas‐Galindo, María‐Guadalupe; Handy, Brent E.; Gómez, Sergio; Fuentes, Gustavo A.; Fierro-Gonzalez, Juan C.

doi:10.1021/jp208936r

Cited by 13 publications

(7 citation statements)

References 66 publications

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“…The reduction of Fe 2 O 3 to Fe 3 O 4 in the pure oxide-support occurred at 345 °C, while it shifted to around 200 °C in the Au/Fe 2 O 3 catalyst, suggesting that the Au particles facilitated the reduction of Fe 2 O 3 via the hydrogen spillover effect. H 2 was adsorbed and activated on the Au particles, and the dissociated hydrogen atoms diffused from the Au particle to the surface of Fe 2 O 3 , accelerating the reduction of Fe 2 O 3 . , …”

Section: Resultsmentioning

confidence: 99%

Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe₂O₃ Interface

et al. 2021

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The effect of water on CO oxidation over a Au/Fe 2 O 3 catalyst, fabricated by dispersing 2.3 nm Au particles on a rod-shaped Fe 2 O 3 , was examined comprehensively. Under the dry gas condition (a CO/O 2 mixture), the reaction occurred via a redox mechanism at the Au−Fe 2 O 3 interface, where CO was adsorbed by Au and O 2 was activated by Fe 2 O 3 . However, adding an appropriate amount of H 2 O to the feed stream has altered the reaction pathway and promoted the activity substantially. The Au particles showed a reaction rate of 0.64 mmol CO g Au −1 s −1 at 30 °C with a dry feed gas of 1.0% CO/20.0% O 2 /He, but the addition of 3.0% H 2 O to the reaction gas dramatically enhanced the reaction rate to 5.27 mmol CO g Au −1 s −1 . Detailed spectroscopic characterizations have identified that CO oxidation in the presence of H 2 O followed a water-assisted pathway rather than the conventional redox route. H 2 O promoted the activation of O 2 pronouncedly at the Au−Fe 2 O 3 interface; it might react with O 2 over Fe 2 O 3 , and the generated hydroxyl (−OH) species further interacted with CO, adsorbed on Au particles, forming carboxylate (−COOH) species. Finally, the carboxylate decomposed into CO 2 via a proton transfer to H 2 O.

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Section: Resultsmentioning

confidence: 99%

Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe₂O₃ Interface

et al. 2021

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“…Zacl et al have reported that the problem of deactivation is likely to be universal for all noble metal/ceria system in which a significant fraction of hydrogen in the feed creates a reducing environment facilitates the over-reduction of the support. Recently, Jimenez-Lam et al used an in situ dispersive XANES probe to determine that in the case of Au/Fe 2 O 3 the reduced gold provides sites for H 2 adsorption and dissociation, which is then spillover from the gold to the support, favoring its reduction and restructuring. Our results for Au/CeO 2 seem to agree with those of Jimenez-Lam et al .…”

Section: Resultsmentioning

confidence: 99%

Insight into the Deactivation of Au/CeO₂ Catalysts Studied by In Situ Spectroscopy during the CO-PROX Reaction

Hernández¹,

Gómez

Zepeda³

et al. 2015

ACS Catal.

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The activity and deactivation of Au/CeO2 catalysts in the PROX reaction were measured during long-term experiments (TOS = 160 h) by in-situ DRS-UV-Vis spectroscopy. During the reaction, the support showed a decrease in band gap energy. The activity and selectivity to CO2 were closely linked to the reduction of Au n+ species, the sintering of the reduced Au species and to changes in the Ce 3+ /Ce 4+ ratio. This ratio increased during long-term PROX experiments, showing a decrement of surface oxygen atoms from the CeO2 phase which in the reaction, after which the total oxygen fed to the reaction was wholly consumed. Also, almost all of the Au 3+ species initially present in the catalysts were reduced to Au + and Au 0 . Results suggest that the activity loss is connected to the fast reduction of Au species and is also linked to changes in the redox properties of ceria, breaking the cycle that provides oxygen to the reaction. Sintering of the Au nanoparticles occurs in a longer time scale. On the other hand, in the case of fresh Au/CeO2 catalysts, the Au n+ /Au 0 ratio decreased with increasing Au content. This initial ratio affects CO2 selectivity as a function of temperature.

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“…Interestingly, the amount of surface oxygen species, which might be removable during the redox cycles, varied with the size of Au NPs: 27 % on Au‐573, 20 % on Au‐673 and 17 % on Au‐723 (Table S2). These surface oxygen species might be located at the Au‐Fe 2 O 3 interfacial perimeters and actively participated in the strong metal–support interactions …”

Section: Figurementioning

confidence: 99%

Geometrical Structure of the Gold–Iron(III) Oxide Interfacial Perimeter for CO Oxidation

et al. 2018

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The geometrical structure of the Au‐Fe2O3 interfacial perimeter, which is generally considered as the active sites for low‐temperature oxidation of CO, was examined. It was found that the activity of the Au/Fe2O3 catalysts not only depends on the number of the gold atoms at the interfacial perimeter but also strongly depends on the geometrical structure of these gold atoms, which is determined by the size of the gold particle. Aberration‐corrected scanning transmission electron microscopy images unambiguously suggested that the gold particles, transformed from a two‐dimensional flat shape to a well‐faceted truncated octahedron when the size slightly enlarged from 2.2 to 3.5 nm. Such a size‐induced shape evolution altered the chemical bonding environments of the gold atoms at the interfacial perimeters and consequently their catalytic activity. For Au particles with a mean size of 2.2 nm, the interfacial perimeter gold atoms possessed a higher degree of unsaturated coordination environment while for Au particles with a mean size of 3.5 nm the perimeter gold atoms mainly followed the atomic arrangements of Au {111} and {100} facets. Kinetic study, with respect to the reaction rate and the turnover frequency on the interfacial perimeter gold atom, found that the low‐coordinated perimeter gold atoms were intrinsically more active for CO oxidation. 18O isotopic titration and Infrared spectroscopy experiments verified that CO oxidation at room temperature occurred at the Au‐Fe2O3 interfacial perimeter, involving the participation of the lattice oxygen of Fe2O3 for activating O2 and the gold atoms for CO adsorption and activation.

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Influence of Supported Gold on the Dynamics of Reduction and Crystallization of Iron Oxides: A Dispersive X-ray Absorption Near Edge Structure Spectroscopy and X-ray Diffraction Study

Cited by 13 publications

References 66 publications

Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe₂O₃ Interface

Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe₂O₃ Interface

Insight into the Deactivation of Au/CeO₂ Catalysts Studied by In Situ Spectroscopy during the CO-PROX Reaction

Geometrical Structure of the Gold–Iron(III) Oxide Interfacial Perimeter for CO Oxidation

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Influence of Supported Gold on the Dynamics of Reduction and Crystallization of Iron Oxides: A Dispersive X-ray Absorption Near Edge Structure Spectroscopy and X-ray Diffraction Study

Cited by 13 publications

References 66 publications

Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe2O3 Interface

Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe2O3 Interface

Insight into the Deactivation of Au/CeO2 Catalysts Studied by In Situ Spectroscopy during the CO-PROX Reaction

Geometrical Structure of the Gold–Iron(III) Oxide Interfacial Perimeter for CO Oxidation

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Product

Resources

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Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe₂O₃ Interface

Water-Assisted Low-Temperature Oxidation of CO at the Au–Fe₂O₃ Interface

Insight into the Deactivation of Au/CeO₂ Catalysts Studied by In Situ Spectroscopy during the CO-PROX Reaction