The prevalence of surface oxygen vacancies over the mobility of bulk oxygen in nanostructured ceria for the total toluene oxidation

López, José Manuel; Gilbank, Alexander; Garcı́a, Tomás; Solsona, Benjamín; Agouram, Saïd; Torrente‐Murciano, Laura

doi:10.1016/j.apcatb.2015.03.017

Cited by 350 publications

(194 citation statements)

References 33 publications

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“…The first band is assigned to lattice oxygen. While, the latter is associated with oxygen vacancies or defects[31,32]. The results of ESR and XPS analyses confirmed the existence of oxygen vacancy surface defect in our samples.…”

supporting

confidence: 85%

Fibrous silica mesoporous ZSM-5 for carbon monoxide methanation

Teh

Triwahyono

Jalil

et al. 2016

Applied Catalysis A: General

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supporting

confidence: 85%

Fibrous silica mesoporous ZSM-5 for carbon monoxide methanation

Teh

Triwahyono

Jalil

et al. 2016

Applied Catalysis A: General

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“…The data in these speciation diagrams allow some significant inferences concerning the events that take place when CeO 2−x is immersed in water under atmospheric conditions. Since particulate CeO 2−x is known to exhibit oxygen vacancies at the surface [46], then it is clear that the surface contains some fraction of Ce 3+ species associated with the oxygen vacancies while the bulk volume consists predominantly of Ce 4+ species. Consequently, the surface contains both Ce 3+ and Ce 4+ species that can be leached when the solid is immersed in water.…”

Section: Speciation Diagramsmentioning

confidence: 99%

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

et al. 2017

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Abstract:The present work describes the effects of water on Fe-doped nanoparticulate CeO 2 , produced by flame spray pyrolysis, which represent a critical environmental issue because CeO 2 is not stable in typical atmospheric conditions. It is hygroscopic and absorbs~29 wt % water in the bulk when exposed to water vapor but, more importantly, it forms a hydrated and passivating surface layer when immersed in liquid water. In the latter case, CeO 2 initially undergoes direct and/or reductive dissolution, followed by the establishment of a passivating layer calculated to consist of~69 mol % solid CeO 2 ·2H 2 O and~30 mol % gelled Ce(OH) 4 . Under static flow conditions, a saturated boundary layer also forms but, under turbulent flow conditions, this is removed. While the passivating hydrated surface layer, which is coherent probably owing to the continuous Ce(OH) 4 gel, would be expected to eliminate the photoactivity, this does not occur. This apparent anomaly is explained by the calculation of (a) the thermodynamic stability diagrams for Ce and Fe; (b) the speciation diagrams for the Ce 4+ -H 2 O, Ce 3+ -H 2 O, Fe 3+ -H 2 O, and Fe 2+ -H 2 O systems; and (c) the Pourbaix diagrams for the Ce-H 2 O and Fe-H 2 O systems. Furthermore, consideration of the probable effects of the localized chemical and redox equilibria owing to the establishment of a very low pH (<0) at the liquid-solid interface also is important to the interpretation of the phenomena. These factors highlight the critical importance of the establishment of the passivating surface layer and its role in photocatalysis. A model for the mechanism of photocatalysis by the CeO 2 component of the hydrated phase CeO 2 ·2H 2 O is proposed, explaining the observation of the retention of photocatalysis following the apparent alteration of the surface of CeO 2 upon hydration. The model involves the generation of charge carriers at the outer surface of the hydrated surface layer, followed by the formation of radicals, which decompose organic species that have diffused through the boundary layer, if present.

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“…While the analysis of the XPS spectra of Ce 3d is very complex due to the presence of several overlapping peaks, a reasonably accurate deconvolution of the peaks can be made following previously reported methods. 50,51 The Ce 3d XPS spectra for Au-Pd/Ce-NR and Au-Pd/CeO 2 are presented in 15 The concentration of Ce 3+ in the ceria supports and catalysts was determined from the deconvoluted XPS spectra, and is given in Table S2 † and Table 2, respectively. The assynthesised ceria nanorods displayed a higher concentration of Ce 3+ (31%) in comparison with the ceria nanopowder (27%).…”

mentioning

confidence: 99%

Au–Pd NPs immobilised on nanostructured ceria and titania: impact of support morphology on the catalytic activity for selective oxidation

Khawaji

Chadwick

2018

Catal. Sci. Technol.

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Bimetallic Au-Pd nanoparticles supported on different ceria and titania nanostructures have been prepared by sol-immobilisation, and evaluated in the solvent-less selective oxidation of benzyl alcohol. The catalysts were characterised by TEM, STEM, XRD, XPS, ICP-AES, and nitrogen adsorption-desorption measurements.The activity of the catalysts was found to be strongly related to the morphology, structure and physiochemical properties of the supports. Au-Pd/ceria nanorods exhibited remarkably high catalytic activity (TOF > 35 900 h −1 ), and was found to be considerably more active than Au-Pd/titanate nanotubes, and Au-Pd catalysts supported on conventional ceria and titania nanopowders. The outstanding catalytic performance of Au-Pd/ceria nanorods is attributed to the unique surface chemistry of ceria nanorods, and the ability of catalyst preparation method (i.e. sol-immobilisation) to control the metal particle size and the bimetallic alloy formation. The presence of surface defects and high concentration of oxygen vacancies and Ce 3+ in ceria nanorods is likely responsible for the stabilisation of Au-Pd NPs during sol-immobilisation, which led to a very small mean particle size (2.1 nm) corresponding to a dispersion of approximately 52%, and a high surface metal concentration.

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The prevalence of surface oxygen vacancies over the mobility of bulk oxygen in nanostructured ceria for the total toluene oxidation

Cited by 350 publications

References 33 publications

Fibrous silica mesoporous ZSM-5 for carbon monoxide methanation

Fibrous silica mesoporous ZSM-5 for carbon monoxide methanation

Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

Au–Pd NPs immobilised on nanostructured ceria and titania: impact of support morphology on the catalytic activity for selective oxidation

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