XPS study of the supported phase — SiO2 interaction in Mo/SiO2 and CoMo/SiO2 hydrodesulphurization catalysts in their oxidic precursor form

Gajardo, P.; Pirotte, D.; Defossé, C.; Grange, Paul; Delmon, B.

doi:10.1016/0368-2048(79)85033-1

Cited by 51 publications

(17 citation statements)

References 4 publications

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“…In addition, the Si(2p) peak position is nearly 1 eV higher in binding energy for the 780 K deposition vs that at lower temperature. A binding energy of ∼103 eV is consistent with literature values for the Si(2p) peak position in SiO 2 . ,,,,, Surface oxygen, which was always present on the Mo(100) crystal (see above), can be observed as the low-binding-energy shoulder in Figure B. The fwhm of the O(1s) signal is greater than 4 eV, indicating the presence of two types of oxygen, such that peaks at ∼532 and ∼530 eV can be readily resolved.…”

Section: Resultssupporting

confidence: 87%

“…Under some conditions surfaces that initially show anisotropies can be smoothed using reflow techniques. , TEOS is one of a class of molecules called alkoxysilanes, which are of the form (RO) 3 SiOR‘ (where R, R‘ = C 2 H 5 in TEOS). Films deposited by alkoxysilanes are also utilized in protective layer coatings, electronic sensors, chemically modified electrodes, thin film optics, and antireflection coatings. − Interactions between Mo and SiO 2 are also of interest in order to better understand ceramic/metal interface properties, coating operations, , and reactions in heterogeneous catalysis, since SiO 2 is often used a catalyst support material. − …”

Section: Introductionmentioning

confidence: 99%

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Pyrolysis of Tetraethoxysilane on Mo(100) at Low Temperatures

Jurgens-Kowal

Rogers

1998

J. Phys. Chem. B

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Deposition of ultrathin silicon dioxide films on Mo(100) substrates by pyrolysis of tetraethoxysilane (TEOS) vapor has been investigated at temperatures between 300 and 860 K with X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption (TPD), low-energy electron diffraction (LEED), and infrared reflection−absorption spectroscopy (IRRAS). Up to temperatures of ∼600 K, TEOS adsorbs on the Mo surface forming an ethoxysilyl intermediate, whereas at higher temperatures SiO2 is formed during the initial exposure, as evidenced by both XPS and IRRAS data. Deposition of silicon dioxide is reaction-limited in the temperature range studied with roughly a monolayer forming on the surface at 860 K. Heating the TEOS-exposed Mo(100) surfaces to ∼1000 K yields ethylene as the predominant gas-phase decomposition product and improves both the stoichiometry and order of the films as indicated by an increase in the stretching frequency of the Si−O IRRAS peaks. A decrease in the amount of desorbed ethylene is observed as the deposition temperature increases from 300 to ∼600 K, and no significant desorption of any other decomposition products was detected at higher deposition temperatures. Carbon contamination is minimal in these SiO2 films.

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Section: Resultssupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Pyrolysis of Tetraethoxysilane on Mo(100) at Low Temperatures

Jurgens-Kowal

Rogers

1998

J. Phys. Chem. B

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“…The diffraction pattern of SEP appears broad peaks around 2θ = 17.7°, 19.8°, 26.7°, 34.9°, and 45.6°, corresponding to crystal structure of SEP. Interestingly, the intensity of these peaks attenuated evidently and even disappeared for the three Mo/SEP catalysts, which implies that molybdenum oxide species covered part of SEP and diluted its diffraction peaks or Mo species fiercely interacted with skeletal Si or Al in SEP framework to form some amorphous species such as Al 2 (MoO 4 ) 3 and SiMo x species. 45,46 This is consistent with the appearance of rough particles on SEP surface as displayed by SEM analysis. The FTIR technology was further carried out to detect the effect of reductive treatments on the skeleton structure of Mo/SEP catalyst.…”

Section: Resultssupporting

confidence: 81%

Effect of Reduction Treatments of Mo/Sepiolite Catalyst on Lignin Depolymerization under Supercritical Ethanol

Chen

Wang

et al. 2020

Energy Fuels

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Depolymerization of lignin to produce high yield lignin oil is one of the prospective methods to achieve the sustainable and economic development for human society. Molybdenum-based sepiolite (Mo/SEP) catalyst presented a promising performance for lignin depolymerization under supercritical ethanol (LDSE). Herein, the influence of reductive treatments for calcined Mo/SEP (C-Mo/SEP) catalyst on lignin depolymerization was systematically investigated under supercritical ethanol. Two reduced catalysts N-Mo/SEP and H-Mo/SEP was obtained respectively through the reduction process by NaBH4 and 10 vol % H2/N2 flow. The characterizations such as N2 adsorption–desorption, SEM, XRD, FTIR, XPS, NH3-TPD, and Py-FTIR were employed to investigate the variation of microcosmic structure and property of Mo/SEP affected by reductive treatments. The results exhibited that reduction treatment optimized the distributions of Mo5+ species and B/L acidic sites of Mo/SEP catalysts. During the LDSE process at 290 °C under N2 atmosphere for 3 h, lignin oil produced over N–Mo/SEP catalyst gave a higher heating value of 34.92 MJ/kg, which slightly decreased from 36.07 MJ/kg that was obtained over C-Mo/SEP. But N-Mo/SEP catalyst generated the highest yields of lignin oil (112.0%) and petroleum ether soluble (PES) product (74.6%). According to the GC-MS results, the possible mechanism of N-Mo/SEP catalytic LDSE was proposed. The synergistic effect between Mo5+ species and B/L acid sites promoted the cracking of the Caryl–OCH3 bond, and the moderate acid amounts enhanced the alkylation reaction.

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“…Two peaks are found that are attributable to O species as shown in Figure D. One peak has a position at 530.8 ± 0.15 eV, which is attributed to O in MoO 3 and does not shift during the air exposure, supporting that MoO 3 is not changing oxidation states because of the exposure to moisture. The binding energy of the second peak is 532.1 ± 0.15 eV for the nonexposed sample.…”

Section: Resultsmentioning

confidence: 81%

Influence of Moisture on the Energy-Level Alignment at the MoO₃/Organic Interfaces

Yin

Lewis

Andersson

2018

ACS Appl. Mater. Interfaces

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MoO 3 is widely used in polymer-based organic solar cells as an anode buffer layer because of its high workfunction and formation of a strong dipole at the MoO 3 /polymer interface facilitating charge transfer across the MoO 3 /polymer interface. In the present work, we show that exposure of the MoO 3 /polymer interface to moisture attracts water molecules to the interface via diffusion. Because of their own strong dipole, water molecules counter the dipole at the MoO 3 /polymer interface. As a consequence, the charge transfer across the MoO 3 /polymer will reduce and affect the charge transport across the interface. The outcome of this work thus suggests that it is critical to keep the MoO 3 /polymer interface moisture-free, which requires special precautions in device fabrications. The composition of the MoO 3 /P3HT:PC 61 BM interface is analyzed with X-ray photoelectron spectroscopy and the depth profiling technique, neutral impact collision ion scattering spectroscopy. The results show that the concentration of oxygen increases upon exposure but leaves the oxidation state of Mo unchanged. The valence electron spectroscopy technique shows that the dipole across the MoO 3 /P3HT:PC 61 BM interface decreases even for short-time exposure to atmosphere because of the diffusion of water molecules to the interface. The far-ranging consequences for organic electronic devices are discussed.

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XPS study of the supported phase — SiO2 interaction in Mo/SiO2 and CoMo/SiO2 hydrodesulphurization catalysts in their oxidic precursor form

Cited by 51 publications

References 4 publications

Pyrolysis of Tetraethoxysilane on Mo(100) at Low Temperatures

Pyrolysis of Tetraethoxysilane on Mo(100) at Low Temperatures

Effect of Reduction Treatments of Mo/Sepiolite Catalyst on Lignin Depolymerization under Supercritical Ethanol

Influence of Moisture on the Energy-Level Alignment at the MoO₃/Organic Interfaces

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XPS study of the supported phase — SiO2 interaction in Mo/SiO2 and CoMo/SiO2 hydrodesulphurization catalysts in their oxidic precursor form

Cited by 51 publications

References 4 publications

Pyrolysis of Tetraethoxysilane on Mo(100) at Low Temperatures

Pyrolysis of Tetraethoxysilane on Mo(100) at Low Temperatures

Effect of Reduction Treatments of Mo/Sepiolite Catalyst on Lignin Depolymerization under Supercritical Ethanol

Influence of Moisture on the Energy-Level Alignment at the MoO3/Organic Interfaces

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Influence of Moisture on the Energy-Level Alignment at the MoO₃/Organic Interfaces