TEM study of supported catalyst clusters

1991 ◽  
Vol 49 ◽  
pp. 1030-1031
Author(s):  
M. H. Yao ◽  
David J. Smith ◽  
I. E. Wachs
Keyword(s):  
Metal Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Supported Catalyst ◽  
High Resolution Electron Microscopy ◽  
Support Materials ◽  
Direct Observations ◽  
Resolution Electron ◽  
Oxide Substrate ◽  
Surface Metal

In the present work we have studied two-dimensional metal oxide overlayers (Re2O7, WO3, etc) deposited on a second high-surface-area metal oxide substrate (TiO2, Al2O3, etc). The molecular structure of these surface metal oxide species has been extensively studied in the past decade by Raman spectroscopy and EXAFS because of their importance in catalytic applications. However, direct observations of these overlayers are still needed in order to better understand the basic properties of the overlayer species. High resolution electron microscopy(HREM) is one of the most commonly used methods for direct characterization of small catalyst particles. It can provide particle size distributions and information about particle disposition over the support materials. But it is generally believed that bright field imaging is only well suited for particles sizes larger than about 10 Å. For smaller metal particles on typical supports, HAADF in STEM has been proposed as a better choice.

scholarly journals The Role of Surface Hydroxylation, Lattice Vacancies and Bond Covalency in the Electrochemical Oxidation of Water (OER) on Ni-Depleted Iridium Oxide Catalysts

2020 ◽  
Vol 234 (5) ◽  
pp. 787-812 ◽  
Author(s):  
Hong Nhan Nong ◽  
Hoang Phi Tran ◽  
Camillo Spöri ◽  
Malte Klingenhof ◽  
Lorenz Frevel ◽  
...  
Keyword(s):  
Metal Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Oxide Shell ◽  
Mixed Metal Oxide ◽  
Support Materials ◽  
Oxide Support ◽  
Rich Alloy ◽  
Surface Hydroxylation

AbstractThe usage of iridium as an oxygen-evolution-reaction (OER) electrocatalyst requires very high atom efficiencies paired with high activity and stability. Our efforts during the past 6 years in the Priority Program 1613 funded by the Deutsche Forschungsgemeinschaft (DFG) were focused to mitigate the molecular origin of kinetic overpotentials of Ir-based OER catalysts and to design new materials to achieve that Ir-based catalysts are more atom and energy efficient, as well as stable. Approaches involved are: (1) use of bimetallic mixed metal oxide materials where Ir is combined with cheaper transition metals as starting materials, (2) use of dealloying concepts of nanometer sized core-shell particle with a thin noble metal oxide shell combined with a hollow or cheap transition metal-rich alloy core, and (3) use of corrosion-resistant high-surface-area oxide support materials. In this mini review, we have highlighted selected advances in our understanding of Ir–Ni bimetallic oxide electrocatalysts for the OER in acidic environments.

Structure and Composition of Supported Pt-Sn Electrocatalysts

1999 ◽  
Vol 5 (S2) ◽  
pp. 702-703
Author(s):  
V. Radmilovic ◽  
T. Richardson ◽  
SJ. Chen ◽  
P.N. Ross
Keyword(s):  
Electron Microscopy ◽  
Electrode Materials ◽  
High Surface ◽  
High Surface Area ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Alloy Particles ◽  
Composition And Structure ◽  
Resolution Electron

Bimetallic alloy particles supported on high-surface area carbon are widely used as electrode materials. Because of their stability, Pt-Sn alloys are of particulate interest for a variety of applications. Although the reasons for the superior properties of these catalysts are not fully understood, the dispersion, structure, and compositional homogeneity of the alloy clusters, are clearly important factors in determining their catalytic activity. In order to identify the composition and structure of Pt-Sn base nanoparticles, various characterization techniques, mainly X-ray diffraction (XRD) and transmission electron microscopy (TEM) [1], have been applied. However, very often conflicting conclusions regarding to the structure of Pt-Sn particles have been reported. The focus of the present work is to examine a commercially available carbon supported bimetallic Pt-Sn catalyst, with a nominal Pt:Sn wt. ratio of 2:1 (500N and 900N samples) and 3:1 (E270 sample), using high resolution electron microscopy (HREM), electron and X-ray diffraction techniques, and microchemical analysis by energy dispersive X-ray spectroscopy (EDS).

Design of Transition Metal Oxide and Hybrid Mesoporous Materials

2002 ◽  
Vol 728 ◽  
Author(s):  
Clément Sanchez ◽  
Eduardo L. Crepaldi ◽  
Anne Bouchara ◽  
Florence Cagnol ◽  
David Grosso ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Directed Assembly ◽  
Optical Quality ◽  
Hybrid Thin Films ◽  
Poly Ethylene ◽  
Inorganic Framework ◽  
Hybrid Mesoporous Materials

AbstractMesostructured transition metal (Ti, Zr, V, Al and Ce-Zr) oxide-based hybrid thin films, templated by poly(ethylene oxide)-based surfactants or block copolymers, have been prepared reproducibly, displaying 2D-hexagonal (p6m) or 2D-centred rectangular (c2m) structure. By carefully adjusting the variables involved it is possible to combine both high organisation and excellent optical quality. TiO2 and ZrO2-based materials show thermal stability up to 400-550°C. The elimination of the template can be conducted efficiently and gives rise to high surface area mesoporous films. For the other metal oxide hybrids the inorganic framework is much more fragile, and requires a precise sequence of post-treatments to be stabilised. In addition, original and homogeneous macrotextures shaped with coral-like, helical or macroporous sieves morphologies have been obtained following a nanotectonic approach based on the template-directed assembly by poly-γ-benzyl-L-glutamate (PBLG) of organically functionalised CeO2 crystalline nanoparticles.

scholarly journals Oxidation of alkyl benzenes by a flavin photooxidation catalyst on nanostructured metal-oxide films

2017 ◽  
Vol 114 (35) ◽  
pp. 9279-9283 ◽  
Author(s):  
Prateek Dongare ◽  
Ian MacKenzie ◽  
Degao Wang ◽  
David A. Nicewicz ◽  
Thomas J. Meyer
Keyword(s):  
Metal Oxide ◽  
Surface Area ◽  
Aromatic Hydrocarbons ◽  
High Surface ◽  
High Surface Area ◽  
Oxide Films ◽  
Flavin Mononucleotide ◽  
Metal Oxide Films ◽  
Alkyl Benzenes ◽  
Nanostructured Metal

We describe here a surface-bound, oxide-based procedure for the photooxidation of a family of aromatic hydrocarbons by a phosphate-bearing flavin mononucleotide (FMN) photocatalyst on high surface area metal-oxide films.

A Green and Sustainable Approach for Acetalization of Benzaldehyde Using Tungstophosphoric Acid Loaded on Metal Oxide Catalysts

2019 ◽  
Vol 41 (5) ◽  
pp. 805-805
Author(s):  
Li Fanghao Li Fanghao ◽  
Li Chenjie Li Chenjie ◽  
Chen Junyi Chen Junyi ◽  
Wang Kuiwu Wang Kuiwu ◽  
Zhang Haijiang Zhang Haijiang ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Condensation Reaction ◽  
High Surface ◽  
High Surface Area ◽  
Synergetic Effect ◽  
Reaction Model ◽  
Oxide Catalysts ◽  
Tungstophosphoric Acid ◽  
Impregnation Method ◽  
Metal Oxide Catalysts

A series of tungstophosphoric acid (H3PW12O40; HPW) loaded on metal oxide catalysts, namely H3PW12O40/M (M= TiO2, CeO2, ZrO2) was prepared by initial wetting impregnation method and their catalytic performances were also investigated during the condensation reaction of benzaldehyde with glycol. Among them, the 20 wt% H3PW12O40/TiO2 catalyst demonstrated highly active with superior acetal yield (90.1 %) and excellent durability. The high activity of the catalyst derived from high surface area, ultra-strong Brand#248;nsted acidity and synergetic effect of Brand#248;nsted-Lewis acid. Response surface methodology (RSM) based on Box-Behnken design (BBD) was used to optimize the course of the condensation reaction of benzaldehyde with glycol, and the optimal benzaldehyde glycol acetal yield (93.4 %) could be obtained. The optimized yield and the experimental results are similar. Moreover, under optimal reaction conditions, the activation energy (Ea) of reaction could be obtained through the kinetic study of the irreversible parallel reaction model, and the Ea was 23.24 kJ/mol.

GROWTH, MORPHOLOGY, INTERFACIAL EFFECTS AND CATALYTIC PROPERTIES OF Au ON TiO2

2001 ◽  
Vol 08 (01n02) ◽  
pp. 73-93 ◽  
Author(s):  
F. COSANDEY ◽  
T. E. MADEY
Keyword(s):  
Surface Science ◽  
Ultrathin Films ◽  
Room Temperature ◽  
Catalytic Properties ◽  
High Surface ◽  
High Surface Area ◽  
Model System ◽  
Growth Morphology ◽  
Oxide Substrate ◽  
Planar Films

We survey recent studies and present new data on the growth, interactions, structure and chemistry of gold deposited on TiO 2(110) surfaces. The noble metal Au on TiO 2(110) is a model system for weak interaction of a metal with an oxide substrate; it is also of interest because Au on TiO 2 has unusually high activity as a catalyst for CO oxidation at room temperature. In this review, we present results on the growth of ultrathin films of Au on TiO 2(110), as well as the morphology, interface formation, epitaxy, structure and electronic properties of Au on TiO 2 single crystal and planar films. The results are compared to studies of Au on high-surface-area TiO 2 catalysts in an attempt to bridge the gap between surface science experiments and the high pressure conditions of catalyst operation.

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