The Influence of Metal Cluster Size on Adsorption Energies:  CO Adsorbed on Au Clusters Supported on TiO2

2004 ◽  
Vol 126 (6) ◽  
pp. 1892-1899 ◽  
Author(s):  
Douglas C. Meier ◽  
D. Wayne Goodman
Keyword(s):  
Cluster Size ◽  
Metal Cluster ◽  
Au Clusters ◽  
Adsorption Energies

Effects of cluster size and substrate temperature on the homoepitaxial deposition of Au clusters

2002 ◽  
Vol 242 (3-4) ◽  
pp. 463-470 ◽  
Author(s):  
S.-C. Lee ◽  
B.D. Yu ◽  
D.-Y. Kim ◽  
Nong M. Hwang
Keyword(s):  
Substrate Temperature ◽  
Cluster Size ◽  
Au Clusters

Metal cluster size distributions during nozzle jet expansion

1986 ◽  
Vol 48 (17) ◽  
pp. 1122-1124 ◽  
Author(s):  
S.‐N. Yang ◽  
T.‐M. Lu
Keyword(s):  
Cluster Size ◽  
Metal Cluster ◽  
Size Distributions

Synthesis of Aerogel-Metal Cluster Composites by Gamma Radiolysis

2002 ◽  
Vol 740 ◽  
Author(s):  
Massimo F. Bertino ◽  
Jared F. Hund ◽  
Guohui Zhang ◽  
Chariklia Sotiriou-Leventis ◽  
Nicholas Leventis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Metal Ion ◽  
Gamma Ray ◽  
Metal Clusters ◽  
Metal Cluster ◽  
Surface Oxidation ◽  
Colloidal Suspensions ◽  
X Ray ◽  
Au Clusters

ABSTRACTNoble metal clusters (Ag, Au) were formed in a silica aerogel matrix by gamma irradiation of hydrogel precursors loaded with aqueous solutions containing Ag+ or [AuCl4]- ions. Hydrogels exposed to gamma rays assumed the color expected for colloidal suspensions of Ag (respectively Au) clusters. The hydrogels were subsequently washed and supercritically dried, without any evident change in color, indicating that the metal clusters were not removed during drying. Typical gamma ray doses were between 3 and 3.5 kGy, and achieved complete reduction of hydrogels containing metal ion concentrations in the 10-4-10-3 M range. Metal clusters in the aerogel monoliths were characterized with optical absorption, transmission electron microscopy, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. These techniques have shown that the clusters have a crystalline fcc structure. Au clusters consist of pure Au, while surface oxidation of Ag clusters was observed with XPS.

scholarly journals Influence of preparation method on the metal cluster size of platinum/ZSM-5 catalysts as studied with EXAFS

1990 ◽  
Vol 94 (23) ◽  
pp. 8574-8578 ◽  
Author(s):  
F. W. H. Kampers ◽  
C. W. R. Engelen ◽  
J. H. C. Van Hooff ◽  
D. C. Koningsberger
Keyword(s):  
Cluster Size ◽  
Preparation Method ◽  
Metal Cluster

scholarly journals Associative and Dissociative Adsorption of N2O Molecule Over C24 Fullerene Doped With V, Mn, Ru, Pd and Rh: A DFT Investigation

2021 ◽  
Author(s):  
Meryem DERDARE ◽  
ABDELGHANI BOUDJAHEM
Keyword(s):  
Catalytic Properties ◽  
Decomposition Reaction ◽  
Dissociative Adsorption ◽  
Activation Energies ◽  
The Other ◽  
High Catalytic Activity ◽  
Metal Site ◽  
Au Clusters ◽  
Catalytically Active ◽  
Adsorption Energies

Abstract DFT calculations using the PBE-D3 level of theory were conducted on the C24 and MC23 (M = V, Mn, Ru, Pd, Rh and Au) clusters in order to determine their stability and electronic and magnetic properties. The interaction of the N2O molecule with the above clusters has also been examined in order to assess their adsorption and catalytic properties. The results show that the reactivity of the C24 fullerene was greatly improved after doping with a TM atom, and the metal atom which was replaced the carbon atom in the pure C24 fullerene is considered as the most favorable site to adsorb and dissociate the N2O molecule. The molecular adsorption of the N2O on the surface of the MC23 clusters from its oxygen atom was found to be less energetically favorable than by nitrogen atom, and the calculated adsorption energies (Eads) are in the range of - 6.5 to - 24.7 kcal mol-1. The N2O adsorption on the metal site of the clusters could also lead to the dissociation of the N2O into O* and N2 molecule with adsorption energies which vary from - 2.3 to - 86.8 kcal mol-1. The mechanism of the N2O dissociation on the clusters surface was studied, and the activation energies for each system were calculated in order to find the most catalytically active clusters in the N2O decomposition. The results indicate that the activation energies of the VC23 and MnC23 clusters are much lower than those obtained for the other clusters, reflecting high catalytic activity of the two clusters in the N2O decomposition reaction compared to the other studied clusters. The values of Eac of the reaction over the VC23 and MnC23 cluster are 9.3 and 7.9 kcal mol-1, respectively, indicating that both clusters could be employed as greatly active and efficient nanocatalysts for the N2O decomposition reaction.

CO Adsorption on the AunS(n=1~6) Clusters: The First-Principles Study

2011 ◽  
Vol 341-342 ◽  
pp. 42-47
Author(s):  
Shui Lian Chi ◽  
Ming Chen ◽  
Song Lin Peng
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Population Analysis ◽  
Co Adsorption ◽  
Bimetallic Clusters ◽  
Mulliken Population Analysis ◽  
Mulliken Population ◽  
Functional Theory ◽  
Au Clusters ◽  
Adsorption Energies

Density functional theory (DFT) calculations are performed to investigate CO bonded on the AunS (n=1~6) bimetallic clusters. It is found that the adsorption energies of CO on the AunS(n=1~6) clusters are greater than those on the pure Au clusters of corresponding sizes. This means that doped S atom can enhance CO adsorption on the Au clusters. Furthermore, through the Mulliken population analysis, we can see that charges transfer from the Au clusters to S atom, while charges donate to the Au clusters from the CO in CO/AunS sytem.

scholarly journals Quantifying Enhancement of Metal-Supported Zeolites Due to Hydrogen Spillover

2018 ◽  
Vol 43 (2) ◽  
pp. 157-165
Author(s):  
Shrivanand M. Pai ◽  
Barat L. Newalkar ◽  
Parimal A. Parikh
Keyword(s):  
Cluster Size ◽  
Zeolite Y ◽  
Metal Cluster ◽  
Temperature Programmed Desorption ◽  
Acid Sites ◽  
Acid Strength ◽  
Hydrogen Spillover ◽  
Bifunctional Catalysts ◽  
Temperature Programmed

As bifunctional catalysts, metal-supported zeolites play an important role in refining and petrochemical processes, e.g. isomerisation, alkylation, etc. Reduction in acidity and acid strength of zeolites upon their impregnation with metals have been widely reported. Also hydrogen spillover vis-a-vis the closeness of two catalyst functions (acid and metal) has been discussed at length. Hydrogen spillover has been claimed to give rise to formation of additional acid sites on supports. Here quantification of acid sites for two zeolites, zeolite Y and ZSM-5, impregnated with different metals in various proportions after exposing them to hydrogen, has been attempted using ammonia temperature programmed desorption. The observed acidity values have been explained on the basis of metal cluster size.

scholarly journals Atomic Structure and Mass-Production of Supported Size-Selected Nanoclusters

2014 ◽  
Vol 70 (a1) ◽  
pp. C733-C733
Author(s):  
Richard Palmer
Keyword(s):  
Atomic Structure ◽  
Scanning Transmission Electron Microscopy ◽  
Metal Cluster ◽  
Magic Number ◽  
Au Clusters ◽  
Potential Energy Landscape ◽  
Transmission Electron ◽  
Imaging Results ◽  
Scanning Transmission ◽  
3D Information

Deposition of size-selected nanoclusters assembled from atoms in the gas phase is a novel route to the fabrication of <10nm surface features. I will focus on the creation and atomic structure of monodispersed metal cluster arrays which enable new model catalysts and protein biochips. The atomic structure of the clusters – previously the province of theory - is revealed experimentally [1] by aberration-corrected scanning transmission electron microscopy (STEM) in the HAADF imaging regime; we can "count" atoms and obtain 3D information not just 2D projections. Results include mass spectrometry of thiolated Au clusters, adatom dynamics on Au923 magic-number nanoclusters [2], first atomic imaging results for Au55 and Au20 and a method to explore the potential energy landscape of (Au923) clusters via cluster transformations [3], presenting a reference system for theory. A new kind of cluster beam source, to allow super-abundant generation of size-selected nanoclusters, will also be demonstrated.

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