Local atomic configurations, energy structure, and optical properties of implantation defects in Gd-doped silica glass: An XPS, PL, and DFT study

Zatsepin, A. F.; Zatsepin, D. A.; Boukhvalov, Danil W.; Kuznetsova, Yu. A.; Гаврилов, Н. В.; Shur, V. Ya.; Есин, А. А.

doi:10.1016/j.jallcom.2019.04.303

Cited by 13 publications

(9 citation statements)

References 31 publications

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“…The peak corresponding to the Si 2p orbital always has the expected position at 103.4 eV, which corresponds the expected position for SiO 2 [38,39]. The binding energies (BE) of the Ta 4f 7/2 orbital falls around 26.9 eV for 4Ta IMP Si-2Ag, very close to the position found for pure Ta 2 O 5 [40,41].…”

Section: Sample S Betsupporting

confidence: 70%

Ag- and Cu-Promoted Mesoporous Ta-SiO2 Catalysts Prepared by Non-Hydrolytic Sol-Gel for the Conversion of Ethanol to Butadiene

2019

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The direct catalytic conversion of bioethanol to butadiene, also known as the Lebedev process, is one of the most promising solution to replace the petro-based production of this important bulk chemical. Considering the intricate reaction mechanism—where a combination of acid-catalyzed dehydration reactions and metal-catalyzed dehydrogenation have to take place simultaneously—tailor-made bifunctional catalysts are required. We propose to use non-hydrolytic sol-gel (NHSG) chemistry to prepare mesoporous Ta-SiO2 materials which are further promoted by Ag via impregnation. An acetamide elimination route is presented, starting from silicon tetraacetate and pentakis(dimethylamido)tantalum(V), in the presence of a Pluronic surfactant. The catalysts display advantageous texture, with specific surface area in the 600–1000 m² g−1 range, large pore volume (0.6–1.0 mL g−1), an average pore diameter of 4 nm and only a small contribution from micropores. Using an array of characterization techniques, we show that NHSG allows achieving a high degree of dispersion of tantalum, mainly incorporated as single sites in the silica matrix. The presence of these monomeric TaOx active sites is responsible for the much higher dehydration ability, as compared to the corresponding catalyst prepared by impregnation of Ta onto a pristine silica support. We attempt to optimize the butadiene yield by changing the relative proportion of Ta and Ag and by tuning the space velocity. We also demonstrate that Ag or Cu can be introduced directly in one step, during the NHSG process. Copper doping is shown to be much more efficient than silver doping to guide the reaction towards the production of butadiene.

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Section: Sample S Betsupporting

confidence: 70%

Ag- and Cu-Promoted Mesoporous Ta-SiO2 Catalysts Prepared by Non-Hydrolytic Sol-Gel for the Conversion of Ethanol to Butadiene

2019

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“…Congruently with the theoretical model, XPS spectra did not evidence any modification of Ga‐3d and Se‐3d core levels after dosing 10 10 L (1 L=10 −6 Torr⋅s) of O 2 and H 2 O at room temperature on GaSe (Figure 4a–b) [56,70–74] . To further verify the role of Se vacancies, the surface of GaSe were modified by ion bombardment, so as to introduce a density of Se vacancies of ∼10 16 cm −2 , estimated by quantitative XPS [75,76] . After ion bombardment, two new components in Ga‐3d (Figure 4c) were observed, assigned to Ga(0), [56] and Ga 2 Se 3 species , [72] respectively.…”

Section: Resultssupporting

confidence: 61%

“…[56,[70][71][72][73][74] To further verify the role of Se vacancies, the surface of GaSe were modified by ion bombardment, so as to introduce a density of Se vacancies of ~10 16 cm À 2 , estimated by quantitative XPS. [75,76] After ion bombardment, two new components in Ga-3d (Figure 4c) were observed, assigned to Ga(0), [56] and Ga 2 Se 3 species , [72] respectively. Correspondingly, in the Se-3d (Figure 4d) a new component corresponding to both Se(0) and Ga 2 Se 3 species [77] emerges.…”

Section: Experimental Validation Of the Theoretical Modelmentioning

confidence: 99%

III–VI and IV–VI van der Waals Semiconductors InSe, GaSe and GeSe: A Suitable Platform for Efficient Electrochemical Water Splitting, Photocatalysis and Chemical Sensing

Boukhvalov

D’Olimpio

Nappini

et al. 2022

Israel Journal of Chemistry

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Here, we discuss the physicochemical properties of both bulk and nanosheets of III-VI and IV-VI metal chalcogenides and their application capabilities in electrocatalysis, photocatalysis, and gas sensing by combining density function theory with surface-science experiments. In particular, GaSe, InSe, and GeSe are van der Waals semiconductors stable in water media and robust against CO poisoning, which make them suitable candidates for application as low-cost (photo)catalysts in liquid media. Both bulk and exfoliated III-VI and IV-VI metal chalcogenides are prone to oxidation, with the formation of an oxide skin in oxidative environments. The self-assembled heterostructure formed by the oxide skin and the underlying bulk of metal chalcogenides makes the Heyrovsky step of HER energeti-cally favourable. Both metal and Se vacancies are necessary to decrease the energy barrier for HER in acid media. The oxidation modified the band gap, enabling the activation of photocatalytic process with different wavelengths. Moreover, the self-assembled metal-oxide/metal-chalcogenide heterostructure also enables sensing of NO 2 , NH 3 and CO for an operational temperature up to 600 °C. Thus, III-VI and IV-VI semiconductors represent a suitable platform for electrochemistry, photocatalysis, and chemical sensing, owing to their low costs as raw materials and the superior application capabilities activated just exploiting the natural interaction with air, which is beneficial for improving the (photo)electrocatalyst activity and the gas-sensing performances.

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“…Energies of the chemical processes were discussed as the differences between total energies of products and reactants. Our recent work demonstrated the feasibility of this model for the description of defects in quartz . For SnO 2 , SnI 2 , SnI 4 , we calculated the electronic structure and total energies for the structures corresponding with ground states.…”

Section: Experimental and Calculation Detailsmentioning

confidence: 99%

Influence of Ion Migration from ITO and SiO₂ Substrates on Photo and Thermal Stability of CH₃NH₃SnI₃ Hybrid Perovskite

et al. 2020

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The influence of light soaking and heat stress on the degradation of indium tin oxide (ITO)/CH3NH3SnI3 and SiO2/CH3NH3SnI3 hybrid perovskite is studied. The measurements of X-ray photoelectron survey spectra (XPS) showed an increase in the concentration of substrate ions in the surface layer of ITO/CH3NH3SnI3 and reduction of N:Sn and I:Sn ratios after 500 h of white light irradiation and 200 h of annealing at 90 °C. The high-energy-resolved XPS Sn three-dimensional (3d) spectra of ITO/CH3NH3SnI3 indicated a consistent increase in the contribution of Sn4+ ions at these exposure times under light soaking and heat stress. Scanning electron microscopy (SEM) measurements show a violation of the continuity of the perovskite layer with the exposure time and an increase in the size of the voids, which is consistent with the indicated changes in the XPS spectra. On the other hand, we consider the effect of irradiation and annealing on the diffusion of the substrate elements and their chemical interaction with the overlying perovskite layers. The XPS Sn 3d, O 1s, and valence band (VB) measurements and density functional theory (DFT) calculations reveal that at the initial stages of CH3NH3SnI3 degradation, the SnI4 phase separation occurs and with a further increase in exposure time, tin is oxidized to form a SnO2 phase. In addition, we found that CH3NH3SnI3 perovskite prepared on a SiO2 substrate is more stable than on an ITO substrate, and the effect of the oxidation of tin atoms due to the migration of oxygen ions is very weak. The theoretical modeling demonstrates that the formation of SnI2 defects in CH3NH3SnI3 became irreversible due to the oxidation by the migration of the oxygen ions from the substrate. The calculated formation energy of an oxygen vacancy in ITO is about 2 times smaller than in SiO2 that explains the instability of ITO/CH3NH3SnI3.

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Local atomic configurations, energy structure, and optical properties of implantation defects in Gd-doped silica glass: An XPS, PL, and DFT study

Cited by 13 publications

References 31 publications

Ag- and Cu-Promoted Mesoporous Ta-SiO2 Catalysts Prepared by Non-Hydrolytic Sol-Gel for the Conversion of Ethanol to Butadiene

Ag- and Cu-Promoted Mesoporous Ta-SiO2 Catalysts Prepared by Non-Hydrolytic Sol-Gel for the Conversion of Ethanol to Butadiene

III–VI and IV–VI van der Waals Semiconductors InSe, GaSe and GeSe: A Suitable Platform for Efficient Electrochemical Water Splitting, Photocatalysis and Chemical Sensing

Influence of Ion Migration from ITO and SiO₂ Substrates on Photo and Thermal Stability of CH₃NH₃SnI₃ Hybrid Perovskite

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Local atomic configurations, energy structure, and optical properties of implantation defects in Gd-doped silica glass: An XPS, PL, and DFT study

Cited by 13 publications

References 31 publications

Ag- and Cu-Promoted Mesoporous Ta-SiO2 Catalysts Prepared by Non-Hydrolytic Sol-Gel for the Conversion of Ethanol to Butadiene

Ag- and Cu-Promoted Mesoporous Ta-SiO2 Catalysts Prepared by Non-Hydrolytic Sol-Gel for the Conversion of Ethanol to Butadiene

III–VI and IV–VI van der Waals Semiconductors InSe, GaSe and GeSe: A Suitable Platform for Efficient Electrochemical Water Splitting, Photocatalysis and Chemical Sensing

Influence of Ion Migration from ITO and SiO2 Substrates on Photo and Thermal Stability of CH3NH3SnI3 Hybrid Perovskite

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Influence of Ion Migration from ITO and SiO₂ Substrates on Photo and Thermal Stability of CH₃NH₃SnI₃ Hybrid Perovskite