A compact furnace for in situ X-ray absorption spectroscopy: design, fabrication and study of cationic oxidation states in Pr6O11 and NiO

A well designed compact furnace has been designed for in situ X-ray absorption spectroscopy (XAS). It enables various heat ramps from 300 K to 1473 K. The furnace consists of heaters, a quartz tube, a circulated refrigerator and a power controller. It can generate ohmic heating via an induction process with tantalum filaments. The maximum heating rate exceeds 20 K min−1. A quartz tube with gas feedthroughs allows the mixing of gases and adjustment of the flow rate. The use of this compact furnace allows in situ XAS investigations to be carried out in transmission or fluorescence modes under controlled temperature and atmosphere. Moreover, the furnace is compact, light and well compatible to XAS. The furnace was used to study cationic oxidation states in Pr6O11 and NiO compounds under elevated temperature and reduced atmosphere using the in situ X-ray absorption near-edge structure (XANES) technique at beamline 5.2 SUT-NANOTEC-SLRI of the Synchrotron Light Research Institute, Thailand. At room temperature, Pr6O11 contains a mixture of Pr3+ and Pr4+ cations, resulting in an average oxidation state of +3.67. In situ XANES spectra of Pr (L 3-edge) show that the oxidation state of Pr4+ cations was totally reduced to +3.00 at 1273 K under H2 atmosphere. Considering NiO, Ni2+ species were present under ambient conditions. At 573 K, the reduction process of Ni2+ occurred. The Ni0/Ni2+ ratio increased linearly with respect to the heating temperature. Finally, the reduction process of Ni2+ was completely finished at 770 K.

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Probing the variability in oxidation states of magnetite nanoparticles by single-particle spectroscopy

Journal of Materials Chemistry C ◽

10.1039/c7tc03010j ◽

2018 ◽

Vol 6 (4) ◽

pp. 875-882 ◽

Cited By ~ 4

Author(s):

A. Fraile Rodríguez ◽

C. Moya ◽

M. Escoda-Torroella ◽

A. Romero ◽

A. Labarta ◽

...

Keyword(s):

Oxidation State ◽

Absorption Spectroscopy ◽

Magnetite Nanoparticles ◽

Single Particle ◽

Cation Distribution ◽

Oxidation States ◽

Magnetic Response ◽

X Ray ◽

Single Particle Spectroscopy ◽

X Ray Absorption

Single-particle X-ray absorption spectroscopy reveals that the oxidation state and cation distribution of individual magnetite nanoparticles may be largely heterogeneous even when the macroscopic structural and magnetic response of the ensembles is uniform.

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Insights into sulfur poisoning and regeneration of Cu-SSZ-13 catalysts: In situ Cu and S K-edge XAS studies

Catalysis Science & Technology ◽

10.1039/d1cy00975c ◽

2021 ◽

Author(s):

Vitaly Mesilov ◽

Sandra Dahlin ◽

Susanna Liljegren Bergman ◽

Peter Sams Hammershøi ◽

Shibo Xi ◽

...

Keyword(s):

Selective Catalytic Reduction ◽

Oxidation State ◽

Absorption Spectroscopy ◽

Catalytic Reduction ◽

Sulfur Poisoning ◽

X Ray ◽

Scr Catalysts ◽

X Ray Absorption

In situ Cu and S K-edge X-ray absorption spectroscopy (XAS) was used for the investigation of sulfur-poisoned and regenerated Cu-SSZ-13 selective catalytic reduction (SCR) catalysts. Sulfur in the oxidation state...

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Oxygen Reduction Effect on T’-Pr2-xCexCuO4 Nanopowders in the Underdoped Regime Studied by X-Ray Absorption near Edge Structure

Materials Science Forum ◽

10.4028/www.scientific.net/msf.936.93 ◽

2018 ◽

Vol 936 ◽

pp. 93-97 ◽

Cited By ~ 3

Author(s):

Irfanita Resky ◽

Putu Eka Dharma Putra ◽

Triono Bambang ◽

Saiyasombat Chatree ◽

Kamonsuangkasem Krongthong ◽

...

Keyword(s):

Oxidation State ◽

Oxidation States ◽

Edge Structure ◽

X Ray ◽

Reduction Annealing ◽

Gas Atmosphere ◽

Reduction Effect ◽

Ar Gas ◽

X Ray Absorption ◽

Cu Ions

This research is aimed to examine oxidation state of Copper (Cu) in both as-synthesized and reduced T’-Pr2-xCexCuO4 (T’-PCCO) with x = 0, 0.10, and 0.15 using Cu K-edge x-ray absorption near edge structure (XANES). The T‘-PCCO nanopowders were successfully synthesized by the chemically dissolved method with HNO3 as a dissolving agent continued by calcination at 1000°C for 15 h. The reduced T’-PCCO nanopowders were obtained by reduction annealing process at 700°C for 5 h under Ar gas atmosphere. The analyses of XANES spectra show that oxidation states of the Cu ions in all of the T'-PCCO nanopowders have values between +1 and +2. This indicates the existence of electron doping in the CuO2 planes, even in the undoped T’-structure. It is found that the oxidation states of the Cu ions change after reduction annealing depending on the existence of apical oxygen in the T'-structure. Based on the XANES analyses, it is revealed that the change of oxidation state is influenced by the presence of both electron and hole carriers in the two-carrier model of T’-structure.

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In Situ X-Ray Diffraction and In Situ X-Ray Absorption Spectroscopy for Investigation of Intercalation Batteries: Application to the Alkaline H+/γ-MnO2 system.

MRS Proceedings ◽

10.1557/proc-210-387 ◽

1990 ◽

Vol 210 ◽

Cited By ~ 2

Author(s):

C. Lévy-Clèment ◽

C. Mondoloni ◽

C. Godart ◽

R. Cortès

Keyword(s):

Charge Transfer ◽

Oxidation State ◽

Absorption Spectroscopy ◽

Crystallographic Structure ◽

X Ray Diffraction ◽

Alkaline Batteries ◽

X Ray ◽

In Situ Techniques ◽

X Ray Absorption

AbstractThis paper presents applications of in situ X-ray diffraction and absorption techniques to the study of H+/MnO2 alkaline batteries. The two complementary in situ techniques are described. Investigation of the electrochemical insertion and deinsertion of H+ has been made through its influence on the evolution of the crystallographic structure of γ-MnO2, while investigation of the transfer of e has been undertaken through the variation of the oxidation state of the manganese during the discharging and charging process of a battery. New insights in the understanding of the mechanisms of proton insertion and charge transfer into γ-MnO2 are discussed.

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Oxidation State of Ti Atoms and Ti-O Bond Length on Natural Sapphire Gem-Materials Probed by X-Ray Absorption Spectroscopy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.737.585 ◽

2017 ◽

Vol 737 ◽

pp. 585-589 ◽

Cited By ~ 3

Author(s):

Natthapong Monarumit ◽

Wiwat Wongkokua ◽

Somruedee Satitkune

Keyword(s):

Bond Length ◽

Oxidation State ◽

Absorption Spectroscopy ◽

Germanium Detector ◽

Blue Color ◽

Edge Structure ◽

X Ray ◽

Fe Content ◽

X Ray Absorption ◽

Exafs Spectra

Sapphire, an inorganic gem-material in a variety of corundum, mainly consists of alpha-alumina (α-Al2O3) structure. The geological origins of sapphire are related to either basaltic or metamorphic rocks. The causes of the color on sapphire are some trace elements such as Cr, Fe, and Ti. It could be mentioned that Ti atoms have cooperated with Fe atoms for creating the blue color. In this study, X-ray absorption spectroscopy (XAS) technique focused on the x-ray absorption near edge structure (XANES) and the extended x-ray absorption fine structure (EXAFS) is employed to identify the oxidation state of Ti atoms and Ti-O bond length on sapphire samples. The Ti K-edge XANES and EXAFS spectra of natural sapphires were carried out using the 13-channel array germanium detector in fluorescence mode. The XANES spectra showed that the oxidation state of Ti was Ti4+ regardless of Fe content. Moreover, the Ti-O bond length on a-Al2O3 was equal to the Ti-O bond length on rutile (TiO2) analyzed from the EXAFS spectra. From these results, it could be concluded that the oxidation state of Ti atoms on natural sapphires was Ti4+ which substitutes Al3+ on the sapphire structure.

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Vanadium K-edge X-ray-absorption spectroscopy of the functioning and thionine-oxidized forms of the VFe-protein of the vanadium nitrogenase from Azotobacter chroococcum

Biochemical Journal ◽

10.1042/bj2580733 ◽

1989 ◽

Vol 258 (3) ◽

pp. 733-737 ◽

Cited By ~ 35

Author(s):

J M Arber ◽

B R Dobson ◽

R R Eady ◽

S S Hasnain ◽

C D Garner ◽

...

Keyword(s):

Absorption Spectra ◽

Absorption Spectroscopy ◽

Azotobacter Chroococcum ◽

Vanadium Atom ◽

Oxidation States ◽

Edge Structure ◽

X Ray ◽

Vanadium Nitrogenase ◽

Enzyme Turnover ◽

X Ray Absorption

Vanadium K-edge X-ray-absorption spectra were collected for samples of thionine-oxidized, super-reduced (during enzyme turnover) and dithionite-reduced VFe-protein of the vanadium nitrogenase of Azotobacter chroococcum (Acl*). Both the e.x.a.f.s and the x.a.n.e.s. (X-ray-absorption near-edge structure) are consistent with the vanadium being present as part of a VFeS cluster; the environment of the vanadium is not changed significantly in different oxidation states of the protein. The vanadium atom is bound to three oxygen (or nitrogen), three sulphur and three iron atoms at 0.215(3), 0.231(3) and 0.275(3) nm respectively.

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Manganese speciation in soils using X-ray absorption spectroscopy

10.5194/egusphere-egu2020-942 ◽

2020 ◽

Author(s):

Teresa Zahoransky ◽

Christian Mikutta

Keyword(s):

Absorption Spectroscopy ◽

Chemical Reactivity ◽

Mixed Valence ◽

Oxidation States ◽

Plant Residues ◽

Edge Structure ◽

Coordination Environment ◽

X Ray ◽

Local Coordination ◽

X Ray Absorption

<p>Being one of Earth&#180;s most redox-active elements, manganese participates in a great variety of environmental processes and is recognized as a key player controlling carbon turnover and oxidative transformation of organic and inorganic pollutants in soils. Moreover, Mn(III), Mn(IV) or mixed-valence Mn(III/IV) oxides and (oxy)hydroxides are highly effective sorbents for metal pollutants and nutrients in soils. Chemical reactivity, mobility, and bioavailability of Mn depend crucially on its speciation (chemical form). Yet, speciation studies on soil Mn are scarce. Therefore, we employed Mn K-edge (6,539 eV) X-ray absorption spectroscopy (XAS) to determine the oxidation states and local coordination environment (<5 &#197;) of Mn in oxic bulk soils (Cambisols, Luvisols, Stagnosol) from various field sites in Germany. Our XAS analyses cover 23 soil L, O, A, B, and C horizons exhibiting total Mn concentrations of between 200 and 2,300&#160;mg/kg. For comparison, we also analyze a suite of 31 Mn reference compounds, including Mn carbonate, phosphate, oxides and (oxy)hydroxides, silicates, organic Mn compounds as well as clay and hydroxide minerals with adsorbed Mn(II). X-ray absorption near-edge structure (XANES) spectra are evaluated for the oxidation states of soil Mn using linear combination fit (LCF) analysis. In addition, the average local coordination environment of Mn in the soil samples is assessed by shell-fitting of extended X-ray absorption fine structure (EXAFS) spectra. Based on our XAS results, we will test the following hypotheses: (1) Soil L/O horizons comprise predominantly organically complexed Mn(II) and Mn(III), dominated by the former Mn species; (2) soil A horizons are dominated by Mn(III/IV) in Mn(III/IV)-oxide structures owing to high microbial activity, release of Mn(II) from primary silicates and/or plant residues, and its subsequent (a)biotic oxidation and precipitation as Mn(III/IV) oxides; (3) soil B horizons of different genesis differ in their bulk Mn speciation; Bt horizons of Luvisols are dominated by Mn(II) associated with phyllosilicates, whereas the Stagnosol Bg horizon is dominated by layer-type Mn(III/IV) oxides. In summary, our study will provide first comprehensive data on bulk Mn speciation in three major European soil types. This knowledge is a prerequisite for a better understanding of the biogeochemical Mn cycle in soils.</p>

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The State of Trace Elements (In, Cu, Ag) in Sphalerite Studied by X-Ray Absorption Spectroscopy of Synthetic Minerals

Minerals ◽

10.3390/min10070640 ◽

2020 ◽

Vol 10 (7) ◽

pp. 640 ◽

Cited By ~ 1

Author(s):

Nikolay D. Trofimov ◽

Alexander L. Trigub ◽

Boris R. Tagirov ◽

Olga N. Filimonova ◽

Polina V. Evstigneeva ◽

...

Keyword(s):

Solid Solution ◽

Oxidation State ◽

Absorption Spectroscopy ◽

Atomic Structure ◽

Salt Flux ◽

Ionic Radii ◽

Edge Structure ◽

X Ray ◽

X Ray Absorption ◽

Exafs Spectra

The oxidation state and local atomic environment of admixtures of In, Cu, and Ag in synthetic sphalerite crystals were determined by X-ray absorption spectroscopy (XAS). The sphalerite crystals doped with In, Cu, Ag, In–Cu, and In–Ag were synthesized utilizing gas transport, salt flux, and dry synthesis techniques. Oxidation states of dopants were determined using X-ray absorption near edge structure (XANES) technique. The local atomic structure was studied by X-ray absorption fine structure spectroscopy (EXAFS). The spectra were recorded at Zn, In, Ag, and Cu K-edges. In all studied samples, In was in the 3+ oxidation state and replaced Zn in the structure of sphalerite, which occurs with the expansion of the nearest coordination shells due to the large In ionic radius. In the presence of In, the oxidation state of Cu and Ag is 1+, and both metals can form an isomorphous solid solution where they substitute for Zn according to the coupled substitution scheme 2Zn2+ ↔ Me+ + In3+. Moreover, Ag K-edges EXAFS spectra fitting, combined with the results obtained for In- and Au-bearing sphalerite shows that the Me-S distances in the first coordination shell in the solid solution state are correlated with the ionic radii and increase in the order of Cu < Ag < Au. The distortion of the atomic structure increases in the same order. The distant (second and third) coordination shells of Cu and Ag in sphalerite are split into two subshells, and the splitting is more pronounced for Ag. Analysis of the EXAFS spectra, coupled with the results of DFT (Density Function Theory) simulations, showed that the In–In and Me+–In3+ clustering is absent when the metals are present in the sphalerite solid solution. Therefore, all studied admixtures (In, Cu, Ag), as well as Au, are randomly distributed in the matrix of sphalerite, where the concentration of the elements in the “invisible” form can reach a few tens wt.%.

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