Defect Chemistry of Ceria Nanorods

Agarwal, Shilpa; Zhu, Xue‐Qing; Hensen, Emiel Emiel; Lefferts, Leon; Mojet, BL Barbara Louise

doi:10.1021/jp409989y

Cited by 120 publications

(96 citation statements)

References 59 publications

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“…In particular, two peaks can be resolved at higher Raman shifts, around 580 and 601 cm −1 for CeO 2 and Ce 80 Zr 20 , at 785 nm, which are usually observed as a single convoluted band for more energetic excitation wavelengths [27, 29]. These peaks arise from Frenkel type anion defects, in which an oxygen ion occupies an interstitial position, leaving a vacancy at its original lattice site [31]. A single broad band centered around 567 cm −1 is observed for Pr-doped ceria, which was previously suggested to be the convolution of three contributions due to Pr-induced (~545 and ~570 cm −1 ) and intrinsic oxygen vacancies (~595 cm −1 ) [32].…”

Section: Resultsmentioning

confidence: 99%

Catalytic Oxidation of CO and Soot over Ce-Zr-Pr Mixed Oxides Synthesized in a Multi-Inlet Vortex Reactor: Effect of Structural Defects on the Catalytic Activity

et al. 2016

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In the present work, ceria, ceria-zirconia (Ce = 80 at.%, Zr = 20 at.%), ceria praseodymia (Ce = 80 at.%, Pr = 20 at.%) and ceria-zirconia-praseodymia catalysts (Ce = 80 at.%, Zr = 10 at.% and Pr = 10 at.%) have been prepared by the multi-inlet vortex reactor (MIVR). For each set of samples, two inlet flow rates have been used during the synthesis (namely, 2 ml min−1 , and 20 ml min−1) in order to obtain different particle sizes. Catalytic activity of the prepared materials has been investigated for CO and soot oxidation reactions. As a result, when the catalysts exhibit similar crystallite sizes (in the 7.7–8.8 nm range), it is possible to observe a direct correlation between the Ov/F2g vibrational band intensity ratios and the catalytic performance for the CO oxidation. This means that structural (superficial) defects play a key role for this process. The incorporation of Zr and Pr species into the ceria lattice increases the population of structural defects, as measured by Raman spectroscopy, according to the order: CeO2 < Ce80Zr20 < Ce80Zr10Pr10 < Ce80Pr20. On the other hand, the presence of zirconium and praseodymium into the ceria lattice does not have a direct beneficial effect on the soot oxidation activity for these catalysts, in contrast with nanostructured ones (e.g., Ce–Zr–O nanopolyhedra, Ce–Pr–O nanocubes) described elsewhere (Andana et al. Appl. Catal. B 197: 125–137, 2016; Piumetti et al., Appl Catal B 180: 271-282, 2016).

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Section: Resultsmentioning

confidence: 99%

Catalytic Oxidation of CO and Soot over Ce-Zr-Pr Mixed Oxides Synthesized in a Multi-Inlet Vortex Reactor: Effect of Structural Defects on the Catalytic Activity

et al. 2016

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“…The first and the third ones can be assigned to the higher order modes of ceria, namely to the second order transverse acoustic mode, that is, 2TA [24] (although a different assignment to a Ce-OH related vibration has recently been suggested [26]), and to the second overtone of the longitudinal optical band (2LO) [26]. The Raman peak at 598 cm −1 is instead a disorder induced mode arising from Frenkel-type anion defects, consisting of a vacancy, originated by the motion of an O 2− ion to an interstitial octahedral site [17,23]. Defect related bands around 550 cm −1 , due to oxygen vacancies at a Ce 3+ site [23], cannot be resolved, thus pointing out that this set of ceria NPs mainly contains oxidized Ce 4+ .…”

Section: Reducibility and Defective Sitesmentioning

confidence: 98%

Nanostructured Ceria-Based Materials: Effect of the Hydrothermal Synthesis Conditions on the Structural Properties and Catalytic Activity

et al. 2017

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Abstract:In this work, several nanostructured ceria catalysts were prepared by means of a hydrothermal procedure, in which the synthesis conditions (i.e., temperature and pH values) were varied. CeO 2 samples of different shapes and structural properties were obtained, namely cubes, rods, cube and nanorod mixtures, and other polyhedra. The prepared materials were tested using four probe catalytic reactions: CO oxidation, NO oxidation, NO x -free soot oxidation, and NO x -assisted soot oxidation. The physicochemical properties of the prepared catalysts were studied by means of complementary techniques (i.e., XRD, N 2 -physisorption at −196 • C, CO-TPR (temperature-programmed reduction), field emission scanning electron microscopy (FESEM), micro-Raman spectroscopy). The abundance of defects of the catalysts, measured through in-situ Raman spectroscopy at the typical temperatures of each catalytic process, was correlated to the CO and NO oxidation activity of the prepared catalysts, while the soot oxidation reaction (performed in loose conditions), which was hindered by a poor soot-catalyst contact, was found to be less sensitive to the observed structural defects.

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“…Bands at 540-560 cm -1 and 562 to 599 cm -1 have been assigned to vacancies in doped and pure ceria, respectively [53,54]. Recently, our group suggested that shoulders at 404 and 487 cm -1 arise due to formation of defects, as studied by UV Raman spectroscopy [55]. Without going into the depth, we used Raman spectroscopy as a finger print technique to detect the degree of reduction of catalysts after EB dehydrogenation.…”

Section: Characterization Of the Spent Ceria Catalysts With Raman Spementioning

confidence: 99%

The effects of morphology of cerium oxide catalysts for dehydrogenation of ethylbenzene to styrene

Kovacevic

Agarwal

Mojet

et al. 2015

Applied Catalysis A: General

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Defect Chemistry of Ceria Nanorods

Cited by 120 publications

References 59 publications

Catalytic Oxidation of CO and Soot over Ce-Zr-Pr Mixed Oxides Synthesized in a Multi-Inlet Vortex Reactor: Effect of Structural Defects on the Catalytic Activity

Catalytic Oxidation of CO and Soot over Ce-Zr-Pr Mixed Oxides Synthesized in a Multi-Inlet Vortex Reactor: Effect of Structural Defects on the Catalytic Activity

Nanostructured Ceria-Based Materials: Effect of the Hydrothermal Synthesis Conditions on the Structural Properties and Catalytic Activity

The effects of morphology of cerium oxide catalysts for dehydrogenation of ethylbenzene to styrene

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