Operando X-ray absorption investigations into the role of Fe in the electrochemical stability and oxygen evolution activity of Ni1−xFexOy nanoparticles

2018 ◽  
Vol 6 (47) ◽  
pp. 24534-24549 ◽  
Author(s):  
Daniel F. Abbott ◽  
Emiliana Fabbri ◽  
Mario Borlaf ◽  
Francesco Bozza ◽  
Robin Schäublin ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Oxygen Evolution ◽  
Rock Salt ◽  
Electrochemical Stability ◽  
Rock Salt Structure ◽  
X Ray ◽  
Structural And Electronic Properties ◽  
Salt Structure ◽  
X Ray Absorption

The structural and electronic properties of rock salt-type Ni–Fe oxides are investigated under OER conditions. The inclusion of Fe in the rock-salt structure is shown to inhibit the transformation to more layered and disordered polymorphs.

Local structure study of dilute Er in III–V semiconductors by fluorescence EXAFS

1998 ◽  
Vol 5 (3) ◽  
pp. 1061-1063 ◽  
Author(s):  
H. Ofuchi ◽  
D. Kawamura ◽  
J. Tsuchiya ◽  
N. Matsubara ◽  
M. Tabuchi ◽  
...  
Keyword(s):  
Fine Structure ◽  
Rock Salt ◽  
Growth Temperature ◽  
Local Structure ◽  
Structure Study ◽  
Rock Salt Structure ◽  
X Ray ◽  
Local Structures ◽  
Salt Structure ◽  
X Ray Absorption

For understanding the luminescence of Er atoms in III–V semiconductors, OMVPE-grown InP doped with Er has been investigated by fluorescence EXAFS (extended X-ray absorption fine structure) in order to study the local structure around Er atoms. The local structures around the Er atoms doped in InP, with doping as dilute as 3 × 1012 Er atoms in a 1.5 mm × 1.0 mm spot, were successfully measured by fluorescence EXAFS. The EXAFS analysis revealed that the Er atoms doped in InP above 853 K (which showed low luminescence) formed the rock-salt-structure ErP, while the Er atoms doped in InP below 823 K (which showed high luminescence) substituted on the In site of InP. The dependence of the local structure on growth temperature was observed for the samples doped with 3 × 1012 atoms and 1.2 × 1013 atoms of Er.

Properties of Pure and Sulfided NiMoO4 and CoMoO4 Catalysts: Tpr, Xanes and Time-Resolved XRD Studdzs

1997 ◽  
Vol 497 ◽  
Author(s):  
S. Chaturvedi ◽  
J. A. Rodriguez ◽  
J. C. Hanson ◽  
A. Albornoz ◽  
J. L. Brito
Keyword(s):  
Electronic Properties ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
Direct Transformation ◽  
X Ray ◽  
Β Phase ◽  
Structural And Electronic Properties ◽  
X Ray Absorption ◽  
Kinetics Of ◽  
Cobalt And Nickel

ABSTRACTX-ray absorption near-edge spectroscopy (XANES) was used to characterize the structural and electronic properties of a series of cobalt- and nickel-molybdate catalysts (AMoO4.nH20, α-AMoO4, β-AMoO4; A= Co or Ni). The results of XANES indicate that the Co and Ni atoms are in octahedral sites in all these compounds, while the coordination of Mo varies from octahedral in the a-phases to tetrahedral in the β-phases and hydrate. Time-resolved x-ray diffraction shows a direct transformation of the hydrates into the β-AMoO4 compounds (following a kinetics of first order) at temperatures between 200 and 350 °C. This is facilitated by the similarities that the AMoO4.nH20 and β-AMoO4 compounds have in their structural and electronic properties. The molybdates react with H 2 at temperatures between 400 and 600 °C, forming gaseous water and oxides in which the oxidation state of Co and Ni remains +2 while that of Mo is reduced to +5 or +4. After exposing α-NiMoO4 and P-NiMoO4 to H2S, both metals get sulfided and a NiMoSx phase is formed. For the β phase of NiMoO4 the sulfidation of Mo is more extensive than for the a phase, making the former a better precursor for catalysts of hydrodesulfurization reactions.

Assessing nickel oxide electrocatalysts incorporating diamines and having improved oxygen evolution activity using operando UV/visible and X-ray absorption spectroscopy

2021 ◽  
Author(s):  
Takafumi Miura ◽  
Shun Tsunekawa ◽  
Sho Onishi ◽  
Toshiaki Ina ◽  
Kehsuan Wang ◽  
...  
Keyword(s):  
Nickel Oxide ◽  
Water Splitting ◽  
Oxygen Evolution ◽  
Absorption Spectroscopy ◽  
Spectroscopic Techniques ◽  
X Ray ◽  
Uv Visible ◽  
X Ray Absorption

The role of diamines incorporated in a nickel oxide electrocatalyst for water splitting was examined using operando UV/XAFS spectroscopic techniques.

scholarly journals Role of Synthetic Parameters on the Structural and Optical Properties of N,Sn-Copromoted Nanostructured TiO2: A Combined Ti K-Edge and Sn L2,3-Edges X-ray Absorption Investigation

Nanomaterials ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 1224
Author(s):  
Martina Fracchia ◽  
Paolo Ghigna ◽  
Alessandro Minguzzi ◽  
Alberto Vertova ◽  
Francesca Turco ◽  
...  
Keyword(s):  
Optical Properties ◽  
Visible Light ◽  
Electronic Properties ◽  
Synergistic Effects ◽  
Sol Gel ◽  
Nanostructured Tio2 ◽  
X Ray ◽  
Light Activity ◽  
X Ray Absorption

Sn-modification of TiO2 photocatalysts has been recently proposed as a suitable strategy to improve pollutant degradation as well as hydrogen production. In particular, visible light activity could be promoted by doping with Sn2+ species, which are, however, thermally unstable. Co-promotion with N and Sn has been shown to lead to synergistic effects in terms of visible light activity, but the underlying mechanism has, so far, been poorly understood due to the system complexity. Here, the structural, optical, and electronic properties of N,Sn-copromoted, nanostructured TiO2 from sol-gel synthesis were investigated: the Sn/Ti molar content was varied in the 0–20% range and different post-treatments (calcination and low temperature hydrothermal treatment) were adopted in order to promote the sample crystallinity. Depending on the adopted post-treatment, the optical properties present notable differences, which supports a combined role of Sn dopants and N-induced defects in visible light absorption. X-ray absorption spectroscopy at the Ti K-edge and Sn L2,3-edges shed light onto the electronic properties and structure of both Ti and Sn species, evidencing a marked difference at the Sn L2,3-edges between the samples with 20% and 5% Sn/Ti ratio, showing, in the latter case, the presence of tin in a partially reduced state.

scholarly journals Is Configurational Entropy the Main Stabilizing Term in Rock-Salt Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O High-Entropy Oxide?

2021 ◽  
Author(s):  
Martina Fracchia ◽  
Mauro Coduri ◽  
Maela Manzoli ◽  
Paolo Ghigna ◽  
Umberto Anselmi-Tamburini
Keyword(s):  
Solid Solution ◽  
Rock Salt ◽  
Single Phase ◽  
Configurational Entropy ◽  
Rock Salt Structure ◽  
High Entropy ◽  
Reversible Transformation ◽  
Salt Structure ◽  
Cubic Structure

We question the conclusions reported in the paper "Entropy-stabilized Oxides, by C. Rost et al., by looking into the role of configurational entropy as the stabilization of the rock-salt cubic structure of the Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O (HEO) solid solution (SS). First, we demonstrate that configurational entropy can be reduced from 1.61R for HEO to 0.5R for a two-member SS, still obtaining a single-phase material if the molar fractions of ZnO and CuO are 0.2. These SSs behave identically as HEO regarding the reversible transformation between a multi- and single-phase states when temperatures are cycled between 800 and 1000 °C. Second, we demonstrate that the different SSs presenting a configurational entropy significantly lower than HEO, are less prone to the cubic to tetragonal structural distortion, suggesting that the configurational entropy has not the central role as stabilizing factor of the rock-salt structure.<br>

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