NH3 Decomposition Kinetics on Supported Ru Clusters: Morphology and Particle Size Effect

Zheng, Weiqing; Zhang, Jian; Xu, Hengyong; Li, Wenzhao

doi:10.1007/s10562-007-9237-z

Cited by 97 publications

(74 citation statements)

References 33 publications

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“…But it is clear that Ru particles grow forming crystallites that contain special surface sites. In this line we experimentally demonstrate, for our catalytic systems, that the Ru particles with size between 3 and 5 nm presents an improved catalytic activity, this range being in agreement with recent publications [17]. These values are something higher that those previously reported and coincide pretty well with that determined for RuCA-2 catalyst reduced at 973 K.…”

Section: Resultssupporting

confidence: 93%

Role of B5-Type Sites in Ru Catalysts used for the NH3 Decomposition Reaction

2009

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A series of activated carbon supported Ru catalysts have been reduced at different temperatures under hydrogen flow, and in some cases under ammonia flow, in order to modify the morphology and the particle size of the metallic active sites. CO chemisorption and transmission electron microscopy have been applied to follow the variations of these particles. The samples have been tested in the ammonia decomposition reaction, where systematic differences in catalytic activities as consequence of the support modification as well as due to the changes in the Ru particle sizes have been detected. Furthermore when potassium is added as catalyst promoter the sintering of Ru particles is significantly diminished and thus the changes in catalytic activities are inhibited. The electronic states of the Ru particles have been evaluated by determination of the chemisorption heats of the CO probe molecule. A part of other promoter or support effects it seems to exit a critical mean size for Ru particles on where maximum of catalytic activity is achieved. This behavior can be rationalized by the presence of surface highly active B5 sites, which consist of an arrangement of three Ru atoms in one layer and two further Ru atoms in an internal layer. These especial surface sites are expected to be in a higher proportion over Ru crystallites of those critical sizes, namely for Ru diameter sizes in the rage of 3-5 nm.

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Section: Resultssupporting

confidence: 93%

Role of B5-Type Sites in Ru Catalysts used for the NH3 Decomposition Reaction

2009

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“…Romain Berthoud et al [30] have studied hydrogen and oxygen adsorption stoichiometries on silica supported ruthenium nanoparticles. Zheng et al [31] have investigated NH 3 decomposition kinetics on supported Ru clusters. Tu et al [32] have studied the interaction of oxygen with ruthenium clusters by density functional study.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Hydrogen Adsorption on Ruthenium Clusters

Yan

Jing

et al. 2011

J Clust Sci

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The geometries, stabilities, electronic, and magnetic properties of hydrogen adsorption on Ru n clusters have been systematically investigated by using density functional theory with generalized gradient approximation. The result indicates the absorbed species does not lead to a rearrangement of the basic cluster. For n [ 2, three different adsorption patterns are found for the Ru n H 2 complexes: One H atom binds to the Ru top site, and another H binds to the bridge site for n = 3, 5, 6, 8; bridge site adsorption for n = 4; hollow site and top site adsorption for n = 7. The adsorption energies display oscillation and reach the peak at n = 2, 4, 7, implying their high chemical reactivity. The small electron transferred number between H atoms and Ru n clusters indicates that the interaction between H atoms and Ru n clusters is small. When H 2 is absorbed on the Ru n clusters, the chemical activity of corresponding clusters is dramatically increased. The absorbed H 2 can lead to an oscillatory behavior of the magnetic moments, and this behavior is rooted in the electronic structure of the preceding cluster and the changes in the magnetic moment are indicative of the relative ordering of the majority and minority LUMO's. The second order difference indicates 5 is magic number in Ru n H 2 and Ru n clusters.

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“…The local structure of the Ru/Ca(NH 2 ) 2 catalyst was investigated to clarify the large increase in TOF shown in Figure d, because ammonia decomposition over Ru catalysts is well known to be a structure‐sensitive reaction ,. Figures and show representative HAADF‐STEM images and histograms of the Ru size distributions for Ru/Ca(NH 2 ) 2 after the catalytic reaction, respectively.…”

Section: Resultsmentioning

confidence: 99%

Large Oblate Hemispheroidal Ruthenium Particles Supported on Calcium Amide as Efficient Catalysts for Ammonia Decomposition

Kishida

Kitano

Inoue

et al. 2018

Chemistry A European J

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Ammonia decomposition is an important technology for extracting hydrogen from ammonia toward the realization of a hydrogen economy. Herein, it is reported that large oblate hemispheroidal Ru particles on Ca(NH ) function as efficient catalysts for ammonia decomposition. The turnover frequency of Ru/Ca(NH ) increased by two orders of magnitude when the Ru particle size was increased from 1.5 to 8.4 nm. More than 90 % ammonia decomposition was achieved over Ru/Ca(NH ) with large oblate hemispheroidal Ru particles at 360 °C, which is comparable to that of alkali-promoted Ru catalysts with small Ru particle sizes. XAFS analyses revealed that Ru particles are immobilized on Ca(NH ) by Ru-N bonds formed at the metal/support interface, which lead to oblate hemispheroidal Ru particles. Such a strong metal-support interaction in Ru/Ca(NH ) is also substantiated by DFT calculations. The high activity of Ru/Ca(NH ) with large Ru particles primarily originates from the shape and appropriate size of the Ru particles with a high density of active sites rather than the electron-donating ability of Ca(NH ) .

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NH3 Decomposition Kinetics on Supported Ru Clusters: Morphology and Particle Size Effect

Cited by 97 publications

References 33 publications

Role of B5-Type Sites in Ru Catalysts used for the NH3 Decomposition Reaction

Role of B5-Type Sites in Ru Catalysts used for the NH3 Decomposition Reaction

Theoretical Study of Hydrogen Adsorption on Ruthenium Clusters

Large Oblate Hemispheroidal Ruthenium Particles Supported on Calcium Amide as Efficient Catalysts for Ammonia Decomposition

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