An Investigation of the Chromium Oxidation State of a Monoanionic Chromium Tris(catecholate) Complex by X-ray Absorption and EPR Spectroscopies

2001 ◽  
Vol 40 (2) ◽  
pp. 214-217 ◽  
Author(s):  
David I. Pattison ◽  
Aviva Levina ◽  
Michael J. Davies ◽  
Peter A. Lay
Keyword(s):  
Oxidation State ◽  
X Ray ◽  
Catecholate Complex ◽  
Chromium Oxidation ◽  
X Ray Absorption

scholarly journals Changes of Pd Oxidation State in Pd/Al2O3 Catalysts Using Modulated Excitation DRIFTS

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 116
Author(s):  
Gian Luca Chiarello ◽  
Ye Lu ◽  
Miren Agote-Arán ◽  
Riccardo Pellegrini ◽  
Davide Ferri
Keyword(s):  
Particle Size ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Oxidation State ◽  
Diffuse Reflectance ◽  
X Ray ◽  
Spectral Changes ◽  
Diffuse Reflectance Infrared ◽  
X Ray Absorption ◽  
Reversible Reduction

Infrared spectroscopy is typically not used to establish the oxidation state of metal-based catalysts. In this work, we show that the baseline of spectra collected in diffuse reflectance mode of a series of Pd/Al2O3 samples of increasing Pd content varies significantly and reversibly under alternate pulses of CO or H2 and O2. Moreover, these baseline changes are proportional to the Pd content in Pd/Al2O3 samples exhibiting comparable Pd particle size. Similar measurements by X-ray absorption spectroscopy on a different 2 wt.% Pd/Al2O3 confirm that the baseline changes reflect the reversible reduction-oxidation of Pd. Hence, we demonstrate that changes in oxidation state of metal-based catalysts can be determined using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and that this behavior is part of the spectral changes that are returned by experiments under operando conditions.

scholarly journals Magnetic spectroscopy of nanoparticulate greigite, Fe3S4

2017 ◽  
Vol 81 (4) ◽  
pp. 857-872 ◽  
Author(s):  
Richard A. D. Pattrick ◽  
Victoria S. Coker ◽  
Masood Akhtar ◽  
M. Azad Malik ◽  
Edward Lewis ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Oxidation State ◽  
Magnetic Circular Dichroism ◽  
Covalent Character ◽  
X Ray ◽  
Positive Feature ◽  
A Site ◽  
Intermediate Oxidation ◽  
X Ray Absorption ◽  
Ferrite Spinel

AbstractSynthesis of Ni and Zn substituted nano-greigite, Fe3S4, is achieved from single source diethyldithiocarbamato precursor compounds, producing particles typically 50–100 nm in diameter with plate-like pseudohexagonal morphologies. Up to 12 wt.% Ni is incorporated into the greigite structure, and there is evidence that Zn is also incorporated but Co is not substituted into the lattice. The FeL3X-ray absorption spectra for these materials have a narrow single peak at 707.7 eV and the resulting main X-ray magnetic circular dichroism (XMCD) has the same sign at 708.75 eV. All XMCD spectra also have a broad positive feature at 711 eV, a characteristic of covalent mixing. The greigite XMCD spectra contrast with the three clearly defined XMCD site specific peaks found in the ferrite spinel, magnetite. The FeL2,3X-ray absorption spectra and XMCD spectra of the greigite reflect and reveal the high conductivity of greigite and the very strong covalency of the Fe–S bonding. The electron hopping between Fe3+and Fe2+on octahedral sites results in an intermediate oxidation state of the Fe in the Ohsite of Fe2.5+producing an effective formula of [Fe3+↑]A-site[2Fe2.5+↓]B-siteS42–]. The NiL2,3X-ray absorption spectra and XMCD reveal substitution on the Ohsite with a strongly covalent character and an oxidation state <Ni1.5+in a representative formula [Fe3+↑]A[[(2 – x)Fe2.5+↓][Nix1.5+]]BS42–.

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

2018 ◽  
Vol 6 (4) ◽  
pp. 875-882 ◽  
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.

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

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...

scholarly journals Changes in u(VI) SPeciation Upon Sorption onto Montmorillonite from Aqueous and Organic Solutions

1991 ◽  
Vol 257 ◽  
Author(s):  
Catherine Chisholm-Brause ◽  
Steven D. Conradson ◽  
P. Gary Eller ◽  
David E. Morris
Keyword(s):  
Oxidation State ◽  
Aqueous Systems ◽  
X Ray ◽  
Ph Values ◽  
Uranium Oxidation ◽  
Organic Solutions ◽  
X Ray Absorption ◽  
Hydrolysis Of ◽  
Uranium Species ◽  
Lines Of Evidence

ABSTRACTThe speciation of UO22+ and UO22+/ TBP mixtures has been investigated in solution and intercalated with the reference smectite clay SAz-1 using x-ray absorption, Raman, andluminescence spectroscopies. Neither aquated UO22+ nor its TBP complex undergoes any detectable changes in uranium oxidation state on intercalation. Further, at the pH values employed in this work, there is no evidence for hydrolysis of the uranium species to generate dimeric or higher order uranium oligomers. However, we do find indications that the structures of the solution complexes are altered on intercalation, particularly for the UO22+TBP system and for more dilute UO22+/aqueous systems. In addition, several lines of evidence suggest that, at the loading levels used in this study, the uranyl species is interacting with two or more spectroscopically distinguishable sites on SAz-1.

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

2018 ◽  
Vol 936 ◽  
pp. 93-97 ◽  
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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