Ceria Catalysts at Nanoscale: How Do Crystal Shapes Shape Catalysis?

Trovarelli, Alessandro; Llorca, Jordi

doi:10.1021/acscatal.7b01246

Cited by 610 publications

(510 citation statements)

References 190 publications

(517 reference statements)

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“…61 Furthermore, oxygen vacancies have been found to play a highly important role in oxidation reactions over ceria and metal NPs supported on ceria. 37 For example, in the oxidation of toluene oxygen vacancies contribute to the activation of the substrate via surface oxygen vacancies, and the migration of bulk oxygen to the surface. 53 The concentration of Ce 3+ has also been correlated with the adsorption of molecular oxygen by ceria and formation of superoxide species on the surfaces of ceria, and has been linked to the observed high catalytic oxidation activity of ceria in some oxidation reactions.…”

Section: Catalytic Activity Measurementmentioning

confidence: 99%

“…It is generally observed that ceria nanorods grow along the [100] direction with exposed {100} and {110} surfaces 28,37 although recent literature suggests that the {110} surfaces of ceria nanorods can reconstruct exposing large fractions of {111} nanofacets on the {110} planes. 38 The presence of defects and imperfections in the lattices of ceria nanorods is a consequence of the different plane exposures, 37 and play a vital role in the stabilization of metal NPs, which grow preferentially on surface defects sites where the contact area with the support is maximised.…”

mentioning

confidence: 99%

“…38 The presence of defects and imperfections in the lattices of ceria nanorods is a consequence of the different plane exposures, 37 and play a vital role in the stabilization of metal NPs, which grow preferentially on surface defects sites where the contact area with the support is maximised. 39 Hence, the presence of a high number of oxygen vacancies and surface defects in ceria supports, and in Ce-NRs in particular, likely have stabilised the Au-Pd NPs and contributed to high and uniform metal dispersion observed in the TEM and STEM images.…”

mentioning

confidence: 99%

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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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Section: Catalytic Activity Measurementmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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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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“…It is not an easy task to provide an explanation for the observed behavior of mixed Mn x Ce 1−x oxides compared to pure CeO 2 or MnO x . Trovarelli and Llorca have stressed the importance of size, shape, and degree of exposure of specific facets of ceria-based particles on their catalytic performance [30]. The distribution of specific nanofacets of ceria depends on its size and shape and leads to different reactivity in CO adsorption, for example [31].…”

Section: Discussionmentioning

confidence: 99%

Intrinsic Activity of MnOx-CeO2 Catalysts in Ethanol Oxidation

Delimaris

Ioannides

2017

Catalysts

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MnO x -CeO 2 mixed oxides are considered efficient oxidation catalysts superior to the corresponding single oxides. Although these oxides have been the subject of numerous studies, their fundamental performance indicators, such as turnover frequency (TOF) or specific activity, are scarcely reported. The purpose of the present work is to investigate the effect of catalyst composition on the concentration of active sites and intrinsic activity in ethanol oxidation by the employment of temperature-programmed desorption and oxidation of isotopically-labelled ethanol, 12 CH 3 13 CH 2 OH.The transformation pathways of preadsorbed ethanol in the absence of gaseous oxygen refer to dehydrogenation to acetaldehyde followed by its dissociation combined with oxidation by lattice oxygen. In the presence of gaseous oxygen, lattice oxygen is rapidly restored and the main products are acetaldehyde, CO 2 , and water. CO 2 forms less easily on mixed oxides than on pure MnO x . The TOF of ethanol oxidation has been calculated assuming that the amount of adsorbed ethanol and CO 2 produced during temperature-programmed oxidation (TPO) is a reliable indicator of the concentration of the active sites.

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“…By combining advanced acquisition and processing techniques, timeresolved HRTEM will enable new insights into the structural evolution of nanoparticle surfaces. In this work, we use time-resolved HRTEM to achieve high spatial and temporal resolution of surface atom migration on CeO2 nanoparticles, a material that is used extensively in catalysis applications due to its oxygen exchange properties [4].An aberration-corrected FEI Titan ETEM equipped with a Gatan K2 IS direct detection camera (with high detection quantum efficiency) was used to image CeO2 nanoparticles at 400 frames/second and 10 4 e -/(Å 2 s) in vacuum. A single frame of 1/400 second exposure is shown in Figure 1a), and due to the fast acquisition rate, the signal-to-noise ratio of the image was low.…”

mentioning

confidence: 99%

Determination of Surface Dynamics on CeCh Nanoparticles Using Time-Resolved High-Resolution TEM

Lawrence

Barnaby

Miller³

et al. 2018

Microsc Microanal

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Characterizing the structural evolution of catalyst nanoparticle surfaces can provide insights into the active motifs responsible for catalysis. High-resolution transmission electron microscopy (HRTEM) has been used extensively to study surface dynamics on nanoparticles using in situ imaging techniques [1]. Recent advances in imaging detector technology, namely direct detection cameras with fast acquisition modes, have enabled many new materials phenomena to be investigated, such as the imaging of each sequential step of the synthesis of Ni silicide nanostructures within Si nanowires [2]. With the advent of fast image acquisition, large datasets, otherwise known as "big data", are becoming increasingly common and new developments in data storage, data mining, and processing methods are necessary [3]. Thus, batch processing techniques are essential for reducing processing time and extracting useful information from large, often noisy image datasets. By combining advanced acquisition and processing techniques, timeresolved HRTEM will enable new insights into the structural evolution of nanoparticle surfaces. In this work, we use time-resolved HRTEM to achieve high spatial and temporal resolution of surface atom migration on CeO2 nanoparticles, a material that is used extensively in catalysis applications due to its oxygen exchange properties [4].An aberration-corrected FEI Titan ETEM equipped with a Gatan K2 IS direct detection camera (with high detection quantum efficiency) was used to image CeO2 nanoparticles at 400 frames/second and 10 4 e -/(Å 2 s) in vacuum. A single frame of 1/400 second exposure is shown in Figure 1a), and due to the fast acquisition rate, the signal-to-noise ratio of the image was low. To reduce noise in each individual frame, a Kalman filter was applied to an image stack of ~9000 frames and Figure 1b) shows the resulting filtered image from Figure 1a). For each pixel in the image, the Kalman filter uses a prediction step to produce an estimate of the pixel intensity and its uncertainty. The prediction is then averaged with the measured value from the image through a weighted average, with more weight given to estimates with higher certainty, producing a "filtered" value. The "filtered" value is then used to update the prediction for the next image frame. Thus, the Kalman filter is a computationally light, recursive filtering technique which adapts at each time step to significantly reduce noise in each frame. MIPAR, a commercially available software with a recipe-based image processing method, was used to identify atomic column positions and quantify column intensities [5]. Using MIPAR's batch processing feature, each image from the ~9000 image stack was analyzed with the same recipe. Figure 2a) shows the resulting mask of atomic columns (shown in red) that was detected from a single frame during processing. The mask was then used to generate measurements, including the position, area, intensity mean, and integrated intensity of each atomic column, from the unfiltered image frames. The in...

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Ceria Catalysts at Nanoscale: How Do Crystal Shapes Shape Catalysis?

Cited by 610 publications

References 190 publications

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

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

Intrinsic Activity of MnOx-CeO2 Catalysts in Ethanol Oxidation

Determination of Surface Dynamics on CeCh Nanoparticles Using Time-Resolved High-Resolution TEM

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