Mean Inner Potential of Nanostructured Noble Metal Catalysts - Pt/TiO2 Catalyst -

2003 ◽  
Vol 788 ◽  
Author(s):  
S. Ichikawa ◽  
T. Akita ◽  
K. Okazaki ◽  
M. Okumura ◽  
K. Tanaka ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Noble Metal ◽  
Gold Particle ◽  
Gold Catalysts ◽  
Metal Catalysts ◽  
Electron Holography ◽  
Gold Particles ◽  
Noble Metal Catalysts ◽  
The Mean ◽  
The Difference

ABSTRACTCatalytic properties of noble metal catalysts are often caused by their nanostructures. Gold catalysts are typical cases. It is especially interesting that the catalytic property of gold suddenly changes to resemble that of platinum when the mean size of gold dispersed on certain oxides is <2nm. This phenomenon should be owing to the change of the local electronic structure of the gold particle or the interface between the gold and the oxides, however its detail has not been cleared yet. We measured the mean inner potential of gold particles supported on TiO2 using electron holography and HREM, and found that the mean inner potential of gold depend largely on the size of the gold particles. When the size is >5nm, the mean inner potential is the same as the reported values of bulk gold (experimental: 21–23V, calculated: 25–30V). When the size is <5nm, it begins to increase >30V, and it begins to increase suddenly >40V at the size <2nm. It indicates that the electronic structure of the gold particle varies from that of the bulk state as the size of the gold reduces due to the nano-size effect or the interaction at the interface, since the mean inner potential is sensitive to the electronic state of the outer valence electron. On the other hand, the behavior of the platinum catalysts is different from that of gold catalysts. When the size of the platinum particle on the TiO2 support is >1.5nm, the mean inner potential of platinum is the same as that of the bulk (∼25V). In case of the particle with the size <1.5nm, it begins to increase and the increase rate is lower than that of the gold particles with the size <2nm. It is suggested to be due to the difference of the interaction with TiO2.

How Recyclability can Reduce Induction Period of Gold Nanocatalysts

2019 ◽  
Vol 57 ◽  
pp. 1-6 ◽  
Author(s):  
Sedigheh Ghadamgahi
Keyword(s):  
Catalytic Activity ◽  
Reaction Time ◽  
Gold Particle ◽  
Particle Diameter ◽  
Gold Catalysts ◽  
Gold Particles ◽  
Transmission Electron ◽  
The Mean ◽  
Full Conversion ◽  
Catalytic Test

The effect of recyclability on the catalytic activity of supported Au101(PPh3)21Cl5 nanoparticles (1.0 wt% Au101/AC) was investigated for benzyl alcohol oxidation under mild conditions. The influence of recyclability on the catalytic activity of activated Au101/AC nanocatalysts was studied trough a comparison of gold particle diameter and also catalysts conversion between the fresh (as synthesized) and recycled gold catalysts. The monitoring of gold particle diameters by transmission electron microscopy (TEM) showed that the gold particles size gradually increased during the catalytic reaction. The mean diameter of the fresh gold catalysts increased from approximately 3 to 3.2, 5.1 and 5.3 nm after 1, 2 and 3 h reaction time, respectively. Whereas the average gold particle diameter of the recycled samples were slightly enlarged from approximately 5.3 (the sample recycled after 3 h of the first catalytic test) to 5.7, 5.9 and 6.2 nm with durations of 1, 2 and 3 h reaction time, respectively. Therefore, larger gold particles gradually formed for fresh and also recycled gold catalysts during reaction tests. Meanwhile, the catalytic activity of activated 1.0 wt% Au101/AC catalysts jumped to full conversion when the recycled gold catalysts were utilized due to removing ligand stabilizer from gold particles and so bigger particles had formed.

Atomic and Electronic Structures of Nano-Interface In Au/TiO2 Catalyst - Electron Microscopic Approach -

2002 ◽  
Vol 738 ◽  
Author(s):  
S. Ichikawa ◽  
K. Okazaki ◽  
T. Akita ◽  
M. Okumura ◽  
K. Tanaka ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Catalytic Property ◽  
Size Dependence ◽  
Volume Fraction ◽  
Gold Catalysts ◽  
High Resolution Electron Microscopy ◽  
Electron Microscopic ◽  
Gold Particles ◽  
The Mean ◽  
Bulk Gold

ABSTRACTThe size dependence of the catalytic property of the gold catalysts has been reported. It is especially interesting that the catalytic property of gold suddenly changes to show a platinum-like behavior when the mean size of gold is below 2nm. This phenomenon should be owing to the change of the electronic structure of the gold, however its detail has not been cleared yet. We investigated the size dependence of the mean inner potential of gold catalysts supported on TiO2, which is affected by the outer valence electron, using electron holography and high-resolution electron microscopy. We found the following tendency. When the size of the gold particle is over 5nm, the values of the mean inner potential are the same level as the reported experimental values of the bulk gold (21–23V) and the calculated values of the bulk gold (25–30V). When the size is below 5nm, the mean inner potential begins to increase over 30V, and it begins to increase suddenly over 40V at the size below about 2nm. It indicates that the electronic structure of the gold particles varies from that of the bulk state as the size of the gold particles reduces. Due to the size reduction, the volume fraction of the surface atoms and the interface atoms increases, e.g., almost half of the atoms locate on the surfaces or at the interface in case of the top half of the octahedron particle with the size 1.6nm. The surface dipole and the interface dipole should be formed owing to the electron out of the surface to the vacuum and the local charge transfer from the gold particles to the TiO2 surface. These dipole effects might be effective and one of the reasons for the increase of the mean inner potential of gold particles.

Electron Holographic Nano-Characterization of Gold Catalyst at Interface

2002 ◽  
Vol 727 ◽  
Author(s):  
S. Ichikawa ◽  
T. Akita ◽  
M. Okumura ◽  
M. Haruta ◽  
K. Tanaka
Keyword(s):  
Contact Angle ◽  
Titanium Oxide ◽  
Gold Catalyst ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Electron Holography ◽  
Gold Particles ◽  
Oxide Support ◽  
The Mean ◽  
A Charge

AbstractThe catalytic properties of nanostructured gold catalyst are known to depend on the size of the gold particles and to be activated when the size decreases to a few nanometers. We investigated the size dependence of the three-dimensional nanostructure on the mean inner potential of gold catalysts supported on titanium oxide using electron holography and high-resolution electron microscopy (HREM). The contact angle of the gold particles on the titanium oxide tended to be over 90° for gold particles with a size of over 5 nm, and below 90° for a size of below 2 nm. This decreasing change in the contact angle (morphology) acts to increase the perimeter and hence the area of the interface between the gold and titanium oxide support, which is considered to be an active site for CO oxidation. The mean inner potential of the gold particles also changed as their size decreased. The value of the inner potential of gold, which is approximately 25 V in bulk state, rose to over 40 V when the size of the gold particles was less than 2 nm. This phenomenon indicates the existence of a charge transfer at the interface between gold and titanium oxide. The 3-D structure change and the inner potential change should be attributed to the specific electronic structure at the interface, owing to both the “nano size effect” and the “hetero-interface effect.”

Styrene-divinylbenzene polymer oxidation catalyst

1981 ◽  
Vol 46 (11) ◽  
pp. 2657-2662
Author(s):  
Zdeněk Prokop ◽  
Karel Setínek
Keyword(s):  
Functional Groups ◽  
Noble Metal ◽  
Additional Data ◽  
Catalytic Properties ◽  
Metal Catalysts ◽  
Oxidation Catalyst ◽  
Noble Metal Catalysts ◽  
Polymer Catalyst ◽  
Styrene Divinylbenzene ◽  
Polymer Oxidation

Some additional data about properties and applicability of a styrene-divinylbenzene polymer catalyst containing acidic and redox functional groups are reported. It is shown that the catalysts of this type can be prepared reproducibly and exhibit catalytic properties comparable to the properties of noble metal catalysts.

scholarly journals Sulfur Tolerance of Noble Metal Catalysts for Steam Methane Reforming

2017 ◽  
Vol 60 (3) ◽  
pp. 137-145 ◽  
Author(s):  
Fumihiro Watanabe ◽  
Ikuko Kaburaki ◽  
Naohiro Shimoda ◽  
Akira Igarashi ◽  
Shigeo Satokawa
Keyword(s):  
Noble Metal ◽  
Metal Catalysts ◽  
Methane Reforming ◽  
Sulfur Tolerance ◽  
Steam Methane Reforming ◽  
Noble Metal Catalysts ◽  
Steam Methane

ChemInform Abstract: Alternatives to Noble Metal Catalysts for Automotive Exhaust Purification.

ChemInform ◽  
2010 ◽  
Vol 24 (27) ◽  
pp. no-no
Author(s):  
F. KAPTEIJN ◽  
S. STEGENGA ◽  
N. J. J. DEKKER ◽  
J. W. BIJSTERBOSCH ◽  
J. A. MOULIJN
Keyword(s):  
Noble Metal ◽  
Metal Catalysts ◽  
Automotive Exhaust ◽  
Noble Metal Catalysts ◽  
Exhaust Purification ◽  
Automotive Exhaust Purification

Hydrodeoxygenation of Methyl Heptanoate over Noble Metal Catalysts: Catalyst Screening and Reaction Network

2013 ◽  
Vol 52 (33) ◽  
pp. 11544-11551 ◽  
Author(s):  
Yuwei Bie ◽  
Andrea Gutierrez ◽  
Tuula R. Viljava ◽  
Jaana M. Kanervo ◽  
Juha Lehtonen
Keyword(s):  
Noble Metal ◽  
Reaction Network ◽  
Metal Catalysts ◽  
Noble Metal Catalysts ◽  
Catalyst Screening ◽  
Methyl Heptanoate

General promoting effect of polydopamine on supported noble metal catalysts

2017 ◽  
Vol 5 (39) ◽  
pp. 20789-20796 ◽  
Author(s):  
Mingwei Zhang ◽  
Guozhu Li ◽  
Xiaoqing Sun ◽  
Yujiao Jiang ◽  
Xiangwen Zhang
Keyword(s):  
Noble Metal ◽  
Theoretical Study ◽  
Metal Catalysts ◽  
Promoting Effect ◽  
Noble Metal Catalysts

A joint experimental–theoretical study has been conducted to investigate the role of polydopamine as an interface facilitator for supported noble metal catalysts.

Surface Atomic Regulation of Core–Shell Noble Metal Catalysts

2019 ◽  
Vol 25 (20) ◽  
pp. 5113-5127 ◽  
Author(s):  
Jingjie Ge ◽  
Zhijun Li ◽  
Xun Hong ◽  
Yadong Li
Keyword(s):  
Noble Metal ◽  
Metal Catalysts ◽  
Core Shell ◽  
Noble Metal Catalysts
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