Scanning Probe Microscopy of Cleaved Molybdates: α-MoO3(010), Mo18O52(100), Mo8O23(010), and η-Mo4O11(100)

Smith, Richard L.; Rohrer, Gregory S.

doi:10.1006/jssc.1996.0213

Cited by 80 publications

(58 citation statements)

References 13 publications

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“…Hence, both contain a van der Waals gap between the individual layers, in contrast to other molybdenum oxides possessing crystallographic-shear structures such as Mo 8 O 23 and Mo 9 O 26 . [19] A comparison of the radial distribution functions of MoO 3 and Mo 18 O 52 for a 1 nm cluster is shown in Figure 9.…”

Section: Resultsmentioning

confidence: 99%

Evolution of Defects in the Bulk Structure of MoO₃ During the Catalytic Oxidation of Propene

et al. 2002

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The evolution of characteristic defects in the bulk structure of MoO3 under propene oxidation conditions was investigated by in situ X-ray absorption spectroscopy and X-ray diffraction.Under the reaction conditions employed (273 K to 773 K, and propene to oxygen ratio from 1:1 to 1:5), orthorhombic MoO3 remains the only crystalline phase detected by XRD. The onset temperature of the reaction of propene and oxygen in the presence of MoO3 coincides with the onset of the reduction of MoO3 in He, H2 and propene (~ 620 K). At temperatures below ~720 K and independent of the atmosphere used, partial reduction of MoO3 is observed resulting in the formation of "Mo18O52" type defects in the layer structure of aMoO3. At temperatures above ~720 K and in oxygen or in an oxidizing atmosphere, the "Mo18O52" type defects are re-oxidized to MoO3. Evidently, the catalytically active molybdenum oxide phase develops under partial oxidation conditions at temperatures below 720 K and does not possess the undisturbed ideal layer structure of orthorhombic a-MoO3.The results presented clearly show the necessity and the large potential of bulk structural investigations of heterogeneous catalysts under reaction conditions. The bulk structure and particularly the type and amount of defects in the material ("real" structure) considerably affect the catalytic properties. Hence, in order to rationally design a most active heterogeneous catalyst, both structure and reactions of the surface, and structure, defects, and reactions of the bulk need to be known in detail and carefully considered.

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Section: Resultsmentioning

confidence: 99%

Evolution of Defects in the Bulk Structure of MoO₃ During the Catalytic Oxidation of Propene

et al. 2002

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“…All the lattice parameters corresponded to space group Pbnm (no. 62) [40] of α-MoO 3 for the various sintering temperatures. Furthermore, both lattice parameters, a and b, increased when the MoO 3 powder was subjected to increasing sintering temperatures, which means that the powder’s growth was to the (101) direction.…”

Section: Resultsmentioning

confidence: 99%

The Synthesis of α-MoO3 by Ethylene Glycol

Chiang

Yeh

2013

Materials

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This study investigated the use of ethylene glycol to form α-MoO3 (molybdenum trioxide) from ammonium molybdate tetrahydrate at various sintering temperatures for 1 h. During the sintering process, the morphologies of the constituents were observed using scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy was used to explain the reaction process. In this work, the results obtained using X-ray photoelectron spectroscopy (XRD) demonstrated that, when the molybdenum trioxide powder was treated thermally at 300 °C, the material exhibited crystallinity. The peaks were indexed to correspond with the (110), (040), (021), (111), and (060) crystallographic planes, and the lattice parameters of a, b, and c were about 3.961, 13.876, and 3.969 Å. Using these observations, we confirmed that orthorhombic α-MoO3 was formed for sintering temperatures from 300 to 700 °C. Pattern images were obtained by the selected area electron diffraction pattern (SAED) technique, and the d distance of the high resolution transmission electron microscopy (HRTEM) images were almost 0.39 and 0.36 nm, and the Mo 3d5/2, Mo 3d3/2, and O 1s of X-ray photoelectron spectroscopy (XPS) were located at 233.76, 237.03, and 532.19 eV, which also demonstrated that α-MoO3 powder had been synthesized.

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“…6 For example, the ͑643͒ and (6 4 3 ) surfaces of an face-centered-cubic ͑fcc͒ crystal can be related by reflection through a plane normal to the surfaces, but the two surfaces cannot be superimposed. 8 The only experiments that examine the possibility of enantiospecific adsorption on naturally chiral surfaces to date have been a series of temperature programmed desorption ͑TPD͒ experiments measuring the desorption energy and reaction kinetics of (R)-and (S)-2-butanol on Ag͑643͒ and Ag(6 4 3 ). 7 Naturally chiral surfaces do not only occur for metal surfaces; chiral surfaces have also been observed in studies of low Miller index metal oxide surfaces such as Mo 18 O 52 ͑100͒.…”

Section: Introductionmentioning

confidence: 99%

Enantiospecific adsorption of chiral hydrocarbons on naturally chiral Pt and Cu surfaces

Power

Sholl

1999

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Articles you may be interested inInsight into the description of van der Waals forces for benzene adsorption on transition metal (111) surfacesStepped surfaces of face-centered-cubic crystals are naturally chiral if the step edges include asymmetric steps. These surfaces can, in principle, exhibit enantiospecific adsorption properties if chiral molecules adsorb on them. To provide theoretical characterizations of these enantiospecific properties, we have used Monte Carlo simulations to examine adsorption of two chiral hydrocarbons, trans-1,2-dimethyl-cyclopropane and trans-1,2-dimethyl-cyclobutane, on Pt͑643͒ and Cu͑921͒, two naturally chiral surfaces. These simulations are the first to include the effects of intramolecular relaxations. We also present a simple procedure for predicting the low pressure enantioselectivity of adsorption from a racemic gas phase mixture based on simulations of individual enantiomers.

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Scanning Probe Microscopy of Cleaved Molybdates: α-MoO3(010), Mo18O52(100), Mo8O23(010), and η-Mo4O11(100)

Cited by 80 publications

References 13 publications

Evolution of Defects in the Bulk Structure of MoO₃ During the Catalytic Oxidation of Propene

Evolution of Defects in the Bulk Structure of MoO₃ During the Catalytic Oxidation of Propene

The Synthesis of α-MoO3 by Ethylene Glycol

Enantiospecific adsorption of chiral hydrocarbons on naturally chiral Pt and Cu surfaces

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Scanning Probe Microscopy of Cleaved Molybdates: α-MoO3(010), Mo18O52(100), Mo8O23(010), and η-Mo4O11(100)

Cited by 80 publications

References 13 publications

Evolution of Defects in the Bulk Structure of MoO3 During the Catalytic Oxidation of Propene

Evolution of Defects in the Bulk Structure of MoO3 During the Catalytic Oxidation of Propene

The Synthesis of α-MoO3 by Ethylene Glycol

Enantiospecific adsorption of chiral hydrocarbons on naturally chiral Pt and Cu surfaces

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Product

Resources

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Evolution of Defects in the Bulk Structure of MoO₃ During the Catalytic Oxidation of Propene

Evolution of Defects in the Bulk Structure of MoO₃ During the Catalytic Oxidation of Propene