Magnesium oxide as a catalyst I. Acid-base properties of magnesium oxide surface

Malinowski, S.; Szczepańska, S.; Słoczyński, J.

doi:10.1016/0021-9517(65)90308-8

Cited by 22 publications

(4 citation statements)

References 4 publications

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“…For the Ru coverage of 1 ML, we observed two discrepancies and two similarities [1]. The major O valence bands of MgO were below but above the Fermi level for the stoichiometric and nonstoichiometric models, respectively [2]. The majority 4dorbital electrons of Ru were mostly across the Fermi level from −3 to 2 eV with respect to the Fermi level for both models [3].…”

Section: Electronic Structure Properties Of Ru On Stoichiometric and ...mentioning

confidence: 81%

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Do stoichiometric or nonstoichiometric models of a polar surface affect their structural, energetic and electronic structure properties? A DFT case study of Ru/MgO(111)

Thang¹,

Chen²

2022

J. Phys.: Condens. Matter

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The structural, energetic and electronic structure properties of stoichiometric and nonstoichiometric slab models of bare MgO(111) and Ru/MgO(111) with different coverages of 1 monolayer (ML), 1/4 ML and 1/16 ML have been investigated using spin-polarized density functional theory. Calculated results show that the structural, energetic properties and charge transfer of both bare MgO(111) and Ru/MgO(111) are independent of the stoichiometric and nonstoichiometric models. In contrast, their density of state profiles demonstrate metal and half-metal for the stoichiometric and nonstoichiometric bare MgO(111) surfaces, respectively. The Ru-O orbital coupling characters of these two types of Ru/MgO(111) models are also different. This work indicates that for a polar surface model, the calculated features and trends of the structural and energetic properties, charge distributions and magnetic structures might not be affected by their stoichiometric and nonstoichiometric models; however, the detailed features of their density of state features would strongly depend on the models constructed.

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Section: Electronic Structure Properties Of Ru On Stoichiometric and ...mentioning

confidence: 81%

“…MgO crystals with a rock salt cubic structure has been widely used as catalysts, catalytic supports [1,2], electronic devices * Author to whom any correspondence should be addressed. [3], and optical instruments [4].…”

Section: Introductionmentioning

confidence: 99%

Do stoichiometric or nonstoichiometric models of a polar surface affect their structural, energetic and electronic structure properties? A DFT case study of Ru/MgO(111)

Thang¹,

Chen²

2022

J. Phys.: Condens. Matter

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“…The structural change of the surface molybdate on MgO could be induced by a change of the surface pH. However, it has been shown that the surface pH of MgO remains >8 after firing Mg(OH) 2 at 600 °C, and under this net pH the molybdate should still be isolated tetrahedral. , Moreover, while the net surface pH of the MgO/OH changes from >11 to >8, this effect cannot be totally separated from the underlying structural change of the Mg(OH) 2 to MgO. More importantly the concept of comparing the species obtained under dehydrated conditions to those in aqueous solution breaks down.…”

Section: Resultsmentioning

confidence: 99%

Surface Structure of Highly Dispersed MoO₃ on MgO Using in Situ Mo L₃-Edge XANES

Bare

1998

Langmuir

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The evolution of the dispersed surface molybdate phase on high-surface-area magnesium oxide is studied as a function of weight loading of MoO3 and calcination temperature using in situ Mo L3-edge X-ray absorption near edge spectroscopy, in situ laser Raman spectroscopy, and thermogravimetry−mass spectroscopy. Under ambient, hydrated conditions, the magnesium support is present as magnesium hydroxide, rather than MgO, and the molybdate species is present on the surface as an isolated tetrahedral species for weight loadings of 5−20 wt % MoO3. Under these hydrated conditions the form of the molybdate species is controlled by the net surface pH at the point of zero charge and is the same as that observed in aqueous solution. As the catalyst is calcined in air, the molybdate species transforms from a tetrahedral species, MoO4, to an octahedral one, MoO6. This transformation occurs at the same temperature, ∼450 °C, as that at which the support changes from hydroxide to oxide. This transformation temperature is independent of the MoO3 loading. It is suggested that it is this support-induced structural change that drives the change in the form of the surface molybdate species and not the desorption of adsorbed water.

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“…The goal of this study is to further understand surface reactions between alumina and fluorinated species from decomposing fragments of fluoropolymers. Not only will this understanding contribute toward new strategies to functionalize aluminum particles toward greater reactivity but also the fundamental kinetics may be applied to fuel particles with oxide shells that may produce reactions similar to alumina, such as oxides of magnesium, boron, and silicon. − …”

Section: Introductionmentioning

confidence: 99%

Fluorination of an Alumina Surface: Modeling Aluminum–Fluorine Reaction Mechanisms

Padhye¹,

Aquino

Tunega

et al. 2017

ACS Appl. Mater. Interfaces

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Density functional theory (DFT) calculations were performed to examine exothermic surface chemistry between alumina and four fluorinated, fragmented molecules representing species from decomposing fluoropolymers: F, HF, CHF, and CF. The analysis has strong implications for the reactivity of aluminum (Al) particles passivated by an alumina shell. It was hypothesized that the alumina surface structure could be transformed due to hydrogen bonding effects from the environment that promote surface reactions with fluorinated species. In this study, the alumina surface was analyzed using model clusters as isolated systems embedded in a polar environment (i.e., acetone). The conductor-like screening model (COSMO) was used to mimic environmental effects on the alumina surface. Four defect models for specific active -OH sites were investigated including two terminal hydroxyl groups and two hydroxyl bridge groups. Reactions involving terminal bonds produce more energy than bridge bonds. Also, surface exothermic reactions between terminal -OH bonds and fluorinated species produce energy in decreasing order with the following reactant species: CF > HF > CHF. Additionally, experiments were performed on aluminum powders using thermal equilibrium analysis techniques that complement the calculations. Consistently, the experimental results show a linear relationship between surface exothermic reactions and the main fluorination reaction for Al powders. These results connect molecular level reaction kinetics to macroscopic measurements of surface energy and show that optimizing energy available in surface reactions linearly correlates to maximizing energy in the main reaction.

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Magnesium oxide as a catalyst I. Acid-base properties of magnesium oxide surface

Cited by 22 publications

References 4 publications

Do stoichiometric or nonstoichiometric models of a polar surface affect their structural, energetic and electronic structure properties? A DFT case study of Ru/MgO(111)

Do stoichiometric or nonstoichiometric models of a polar surface affect their structural, energetic and electronic structure properties? A DFT case study of Ru/MgO(111)

Surface Structure of Highly Dispersed MoO₃ on MgO Using in Situ Mo L₃-Edge XANES

Fluorination of an Alumina Surface: Modeling Aluminum–Fluorine Reaction Mechanisms

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Magnesium oxide as a catalyst I. Acid-base properties of magnesium oxide surface

Cited by 22 publications

References 4 publications

Do stoichiometric or nonstoichiometric models of a polar surface affect their structural, energetic and electronic structure properties? A DFT case study of Ru/MgO(111)

Do stoichiometric or nonstoichiometric models of a polar surface affect their structural, energetic and electronic structure properties? A DFT case study of Ru/MgO(111)

Surface Structure of Highly Dispersed MoO3 on MgO Using in Situ Mo L3-Edge XANES

Fluorination of an Alumina Surface: Modeling Aluminum–Fluorine Reaction Mechanisms

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Surface Structure of Highly Dispersed MoO₃ on MgO Using in Situ Mo L₃-Edge XANES