Experimental methods in chemical engineering: X‐ray photoelectron spectroscopy‐XPS

Lefebvre, Josianne; Galli, F.; Bianchi, Claudia L.; Patience, Gregory S.; Boffito, Daria C.

doi:10.1002/cjce.23530

Cited by 48 publications

(23 citation statements)

References 43 publications

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“…This theory is confirmed also by the fact that the weight gain usually is 1.3 mg which corresponds to the quantity of oxygen necessary to oxidizes about 10 % of the all metallic copper (see Supporting Information, Figure S5). XPS reports a surface enrichment of aluminum, as also reported in [67]. Its concentration reaches the maximum in the first layers of the particles (XPS measures from 38 % to 40 % atomic percentage of Al) and decreases after few micrometers depth (SEM-EDX measures from 7 % to 8 % atomic percentage of Al).…”

Section: Resultssupporting

confidence: 74%

Low pressure conversion of CO2 to methanol over Cu/Zn/Al catalysts. The effect of Mg, Ca and Sr as basic promoters

Previtali

Longhi

Galli

et al. 2020

Fuel

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Carbon dioxide concentration level is reaching a non-returning point. Carbon capture technologies are immature and short-term actions are necessary. The conversion of CO 2 into methanol is a technical challenge. Commercial copper-zinc-alumina catalysts convert maximum 7 % carbon dioxide in syngas at high pressures (5 MPa to 10 MPa) and moderate temperatures (473 K to 573 K) into methanol. However, there are not records on the synthesis of methanol at low pressure (P < 2.5 MPa) and without a large excess of hydrogen in the feed. Here, we tested three new catalysts prepared by co-precipitation of copper, zinc and aluminum nitrates (CZA), with strontium, magnesium or calcium as basic promoters to enhance CO 2 conversion to methanol. We discussed the microstructure of the catalysts according to the supersaturation of the relative carbonates formed during the co-precipitation synthesis. Compared to the benchmark, the sample doped with Ca showed higher carbon conversion with all the feed compositions tested (syngas, synthetic biosyngas and CO 2 with H 2 ). CZA doped with Sr is inactive in this reaction.

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Section: Resultssupporting

confidence: 74%

Low pressure conversion of CO2 to methanol over Cu/Zn/Al catalysts. The effect of Mg, Ca and Sr as basic promoters

Previtali

Longhi

Galli

et al. 2020

Fuel

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“…VOSViewer groups the keywords into four research clusters [ 19 ] : the blue cluster to the left of the map with the most keywords includes surface enhanced Raman spectroscopy (SERS), nanoparticles, and Au nanoparticles (Figure 5); films, optical properties, and photoluminescence are major keywords in the red cluster at the top; graphene, carbon nanotubes, and nanocomposites are part of the green cluster to the left; and the smallest cluster (yellow at the bottom) has photocatalysis, degradation, and TiO 2 as the major key words. This classification resembles that of many of the other spectroscopic techniques like FTIR, [ 7 ] x‐ray diffraction, [ 20 ] x‐ray photoelectron spectroscopy, [ 21 ] and transmission electron microscopy. [ 22 ]…”

Section: Applicationsmentioning

confidence: 82%

Experimental methods in chemical engineering: Raman spectroscopy

2020

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When photons impinge on a substrate, most scatter with the same frequency (elastic scattering or Rayleigh dispersion) and only 10 −7 scatter with a different energy (inelastic scattering). This inelastic interaction (Raman scattering) exchanges energy in the region of molecular vibrational transitions for crystalline and amorphous materials. Raman bands in a spectra represent vibrational transitions, like infrared, however the selection rules are different. Typically, the vibrations that are intense in Raman are weak in infrared and vice versa. A remarkable feature of the Raman effect is that it is highly sensitive to nanocrystals, even below 4 nm, which are too small to generate XRD patterns. Plasmonic enhancement, like surface-enhanced Raman spectroscopy (SERS) boost the Raman signal by 10 4 , providing single-molecule detection capability. Glass, quartz, and sapphire are transparent to Raman effect (depending on the energy of the incident excitation radiation), which makes it ideal to examine materials under reaction conditions (in-situ cells and operando reactors that operate over a broad range of temperature, pressures, and environments). Raman spectroscopy emerged in the 1930s; however, infrared spectrometry displaced it. With the advent of powerful lasers in the 1970s, more researchers began to apply Raman routinely. In 2019, the Web of Science indexed 20 400 articles mentioning Raman against 50 000 articles mentioning infrared. Chemical engineers apply Raman less frequently than in material science, physical chemistry, and applied physics, with 887 articles vs 6250, 3700, and 3510 for the other disciplines. A bibliometric analysis identified four research clusters centred on thin films and optics, graphene and nanocomposites, nanoparticles and SERS, and photocatalyst. K E Y W O R D S operando, Raman, Rayleigh, Stokes bands, surface enhanced Raman spectroscopy 1 | INTRODUCTION Raman spectroscopy has become an important and popular analytical tool since it is non-destructive and identifies molecular structure properties and how they change under reactive environments. The technique is based on the Raman effect that C.V. Raman described in 1928 [1] : when electromagnetic radiation (typically monochromatic laser light; near ultraviolet, visible, or near infrared) interacts with a materials molecular vibrations, the incident energy of the photons are scattered with a predominantly lower energy (inelastic scattering). However,

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“…According to the measured photoelectron kinetic energy, almost all elements can be detected except for H and He, and the lowest detection limitation is 0.1 at.%. XPS can also provide valuable information on the chemical state, electronic state, chemical bonding, and depth profiling [65] . Vacancies change the coordination state around the atoms, which leads to the shift of the signal peak or the appearance of a new characteristic peak in the XPS spectrum [66] .…”

Section: Characterizationmentioning

confidence: 99%

Oxygen Vacancy Engineering in Titanium Dioxide for Sodium Storage

Wang

Zhang

et al. 2020

Chemistry An Asian Journal

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Titanium dioxide (TiO2) is a promising anode material for sodium‐ion batteries (SIBs) due to its low cost, natural abundance, nontoxicity, and excellent electrochemical stability. Oxygen vacancies, the most common point defects in TiO2, can dramatically influence the physical and chemical properties of TiO2, including band structure, crystal structure and adsorption properties. Recent studies have demonstrated that oxygen‐deficient TiO2 can significantly enhance sodium storage performance. Considering the importance of oxygen vacancies in modifying the properties of TiO2, the structural properties, common synthesis strategies, characterization techniques, as well as the contribution of oxygen‐deficient TiO2 on initial Coulombic efficiency, cyclic stability, rate performance for sodium storage are comprehensively described in this review. Finally, some perspectives on the challenge and future opportunities for the development of oxygen‐deficient TiO2 are proposed.

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Experimental methods in chemical engineering: X‐ray photoelectron spectroscopy‐XPS

Cited by 48 publications

References 43 publications

Low pressure conversion of CO2 to methanol over Cu/Zn/Al catalysts. The effect of Mg, Ca and Sr as basic promoters

Low pressure conversion of CO2 to methanol over Cu/Zn/Al catalysts. The effect of Mg, Ca and Sr as basic promoters

Experimental methods in chemical engineering: Raman spectroscopy

Oxygen Vacancy Engineering in Titanium Dioxide for Sodium Storage

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