Electrons in Oxygen Vacancies and Oxygen Atoms Activated by Ce3+/Ce4+ Promote High-Sensitive Electrochemical Detection of Pb(II) over Ce-Doped α-MoO3 Catalysts

The title compounds exhibit a K2NiF4-type layered perovskite structure; they are based on the La1.2Sr0.8InO4+δ oxide, which was found to exhibit excellent features as fast oxide-ion conductor via an interstitial oxygen mechanism. These new Ba-containing materials were designed to present a more open framework to enhance oxygen conduction. The citrate-nitrate soft-chemistry technique was used to synthesize such structural perovskite-type materials, followed by annealing in air at moderate temperatures (1150 °C). The subtleties of their crystal structures were investigated from neutron powder diffraction (NPD) data. They crystallize in the orthorhombic Pbca space group. Interstitial O3 oxygen atoms were identified by difference Fourier maps in the NaCl layer of the K2NiF4 structure. At variance with the parent compound, conspicuous oxygen vacancies were found at the O2-type oxygen atoms for x = 0.2, corresponding to the axial positions of the InO6 octahedra. The short O2–O3 distances and the absence of steric impediments suggest a dual oxygen-interstitial mechanism for oxide-ion conduction in these materials. Conductivity measurements show that the activation energy values are comparable to those typical of ionic conductors working by simple vacancy mechanisms (~1 eV). The increment of the total conductivity for x = 0.2 can be due to the mixed mechanism driving both oxygen vacancies and interstitials, which is original for these potential electrolytes for solid-oxide fuel cells.

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Comparation of Cu-Co-Mn Mixed Oxides and Hopcalite as Support in Synthesis of Diphenyl Carbonate by Oxidative Carbonylation of Phenol

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.750-752.1287 ◽

2013 ◽

Vol 750-752 ◽

pp. 1287-1291 ◽

Cited By ~ 2

Author(s):

Hong Xia Guo ◽

Jing De Lü ◽

Hui Qiang Wu ◽

Shu Juan Xiao ◽

Jie Han

Keyword(s):

Electron Microscopy ◽

Oxygen Vacancies ◽

Mixed Oxides ◽

Particle Diameter ◽

Oxidative Carbonylation ◽

Average Particle ◽

Diphenyl Carbonate ◽

X Ray ◽

The Difference ◽

Oxygen Atoms

The difference of Cu-Co-Mn mixed oxides and hopcalite as support in synthesis of diphenyl carbonate by oxidative carbonylation of phenol was studied. The catalysts were characterized by transmission electron microscopy, scanning electron microscopy, X-ray power diffraction, and X-ray photoelectron spectroscopy. The results show that the average particle diameter of the former catalyst is about 40 nm, whereas the other catalyst is about 0.5 μm. The main crystal phase in the former catalyst is Co2MnO4and Pd0.5Pd3O4, which in the latter catalyst is CuMn2O4, CoMn2O4and Pd0.5Pd3O4.The oxygen atoms lose electrons and form oxygen vacancies in.Pd0.5Pd3O4and Co2MnO4of the former catalyst, which destroys the crystal integrity and prompts the oxygen adsorption on the crystal surface. The oxygen atoms lose electrons and form oxygen vacancies in.Pd0.5Pd3O4of the latter catalyst. Finally, it was found that the difference of the yield and selectivity of the both catalysts was not remarkable.

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XAS STUDY OF (BaCuO2)2/(CaCuO2)n SUPERLATTICES

International Journal of Modern Physics B ◽

10.1142/s0217979200002521 ◽

2000 ◽

Vol 14 (25n27) ◽

pp. 2628-2633

Author(s):

S. COLONNA ◽

F. ARCIPRETE ◽

A. BALZAROTTI ◽

G. BALESTRINO ◽

P. G. MEDAGLIA ◽

...

Keyword(s):

Fine Structure ◽

Oxygen Vacancies ◽

Fluorescence Yield ◽

Octahedral Coordination ◽

Apical Oxygen ◽

Edge Structure ◽

X Ray ◽

Local Bonding ◽

X Ray Absorption ◽

Oxygen Atoms

EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-Ray Absorption Near Edge Structure) spectroscopies have been used to probe the local bonding of the artificially layered superconducting (BaCuO2)2/(CaCuO2)n (n = 2, 3, 4) superlattices. Fluorescence-yield measurements have been performed above the Cu and Ba K-edges. This study shows that the charge reservoir (CR) block of the Ba/Ca superlattice contains oxygen vacancies randomly distributed in the CuO2 planes and that the two apical oxygen atoms are displaced out of the Ba plane giving rise to buckled BaO planes. These oxygen atoms have a distorted pyramidal and octahedral coordination around Cu at Ba/Ca interface and in the (BaCuO2) block, respectively.

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Conditions for atomic imaging of mullite

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154068 ◽

1989 ◽

Vol 47 ◽

pp. 418-419

Author(s):

T. A. Epicier ◽

G. Thomas

Keyword(s):

Oxygen Vacancies ◽

High Resolution Electron Microscopy ◽

Ceramic Materials ◽

Work Conditions ◽

Real Space ◽

Potential Candidate ◽

Silicate Mineral ◽

Resolution Electron ◽

The Subject ◽

Aluminium Silicate

Mullite is an aluminium-silicate mineral of current interest since it is a potential candidate for high temperature applications in the ceramic materials field.In the present work, conditions under which the structure of mullite can be optimally imaged by means of High Resolution Electron Microscopy (HREM) have been investigated. Special reference is made to the Atomic Resolution Microscope at Berkeley which allows real space information up to ≈ 0.17 nm to be directly transferred; numerous multislice calculations (conducted with the CEMPAS programs) as well as extensive experimental through-focus series taken from a commercial “3:2” mullite at 800 kV clearly show that a resolution of at least 0.19 nm is required if one wants to get a straightforward confirmation of atomic models of mullite, which is known to undergo non-stoichiometry associated with the presence of oxygen vacancies.Indeed the composition of mullite ranges from approximatively 3Al2O3-2SiO2 (referred here as 3:2-mullite) to 2Al2O3-1SiO2, and its structure is still the subject of refinements (see, for example, refs. 4, 5, 6).

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