Kinetics of hydrogen evolution reaction (HER) is studied on nickel and cobalt-containing electrocatalysts. CoMo, NiMo, and ReNi alloys are obtained by electrodeposition, while NiReP catalysts are ...prepared by electroless deposition under open-circuit conditions using hypophosphite ions as a reducing agent.
The prepared materials are characterized by a complex of modern physical methods; namely, SEM, XPS, XRD, and X-ray absorption spectroscopy. No long-range order was found for all electrodeposited alloys whereas NiReP alloys prepared by electroless deposition contain nickel phosphides. A certain amount of molybdenum or rhenium in the CoMo and ReNi alloys is in the oxidized states. CoMo and ReNi coatings contain 15–20 at. % of oxygen in the form of O2−.
Molybdenum containing alloys are unstable in the alkaline solutions under electrolysis conditions. In opposite, NiRe electrodeposits are promising candidates for hydrogen evolution catalysis in alkaline solutions due to their high catalytic activity and stability under electrolysis conditions.
NiReP alloys can be used for HER catalysis in acidic solutions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Reprocessing of spent nuclear fuel (SNF) is an important task in a frame of ecology and rational use of natural resources. Uranium, as the main component of SNF (>95%), can be recovered for further ...use as fresh nuclear fuel. To minimize an amount of solid radioactive waste generated during SNF reprocessing, new extractants are under investigation. Diamides of 1,10-phenanthroline-2,9-dicarboxylic acid are perspective tetradentate N-donor ligands that form strong complexes with f-elements, which are soluble in polar organic solvents. As an example of three ligands of this class, we conducted a comparative study and showed how the substituent in the amide functional group affects the extraction ability toward uranyl nitrate from nitric acid media. We have performed a careful study (NMR, FT-IR, XRD, RMC-EXAFS) of the structures of synthesized complexes of new ligands with uranyl nitrate and used quantum mechanical calculations to explain the discovered regularities through.
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IJS, KILJ, NUK, PNG, UL, UM
A novel approach to synthesis of PtM/C nanoparticulate catalysts based on thermolysis of heterometallic Pt complexes is proposed. Several new heterometallic platinum (II)-based acetate complexes ...(clusters) with divalent transition metals PtII(OOCMe)4MII(OH2) (M = Co, Mn, Zn, Ni) were synthesized and structurally characterized with X-ray crystallography, IR and NMR spectroscopies. The synthesized clusters were used as precursors of bimetallic supported phase for the fuel cell oxygen reduction reaction. After thermal decomposition of the clusters deposited on carbon black, intermetallics with a Pt: M ≈ 1: 1 ratio were formed. Physico-chemical and electrochemical characteristics of the prepared bimetallic catalysts PtСo/C, PtMn/C PtZn/C and PtNi/C have been investigated. The bimetallic nanoparticles are uniformly distributed over the carbon carrier surface, and grain size in the catalysts is 2–5 nm. The PtZn/C, PtCo/C, PtMn/C and PtNi/C catalysts synthesized from the bimetallic clusters of corresponding metals show advantages over a commercial Pt/C catalyst in the oxygen reduction reaction, PtZn/C in particular, and are promising for use in hydrogen-air fuel cells.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The samples with the CaFe2O4-type crystal structure were obtained by the solid-state reaction method at 1000 °C in the air and the helium atmosphere for the first time. We investigated the ...modification of the structural and electronic properties of the obtained samples. Mössbauer, XAFS-, XPS-spectroscopies, and dc-, ac-conductivity measurements were carried out. Mössbauer and XAFS-spectroscopies showed that the local environment of Fe and Ca cations does not change in the case of the inert atmosphere synthesis. Nevertheless, a sharp six-order increase in the electrical resistance observed at room temperature for the sample obtained in the in the helium atmosphere. Moreover, calculated from dc-conductivity data activation energy rises from 0.327 for the air-synthesized sample to 0.585 eV for helium-obtained one. This behavior indicates significant modification of in-band-gap energy structure, which correlated with thermally activated charge carriers. Our ac-conductivity measurements in the frequency range of 1 kHz–2 MHz for the CaFe2O4 obtained in the air showed the presence of defect levels in the energy band structure. Oxygen pressure reduction during the synthesis results in levels vanishing. Therefore, we suppose the key role of oxygen atoms in the transport properties of the material, which is indirectly confirmed by XPS data. In prospect, CaFe2O4 can be used in promising gas analyzers.
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•First synthesis of CaFe2O4 in a helium atmosphere with a low oxygen pressure (10−5–10−9 kPa).•It is shown that CaFe2O4 structure is very stable for selected synthesis conditions.•We show a key role of the oxygen atoms in the formation of the additional levels in the bandgap.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Valence tautomer transition occurs mainly in 3d metalorganic complexes with redox-active ligands and makes them potential candidates for single-molecular switches. The transition occurs under ...temperature, pressure, or light-induced stimuli and is strongly affected by the intermolecular interactions. However single-crystal x-ray diffraction is not always applicable to such systems when crystal structure is destroyed upon transition or system is studied in the solution. Such an example is bis(o-semiquinonato) cobalt complex with TEMPO-functionalized iminopyridine ancillary ligand. In this work we apply two complementary techniques-ligand-sensitive Fourier transform infrared spectroscopy (FTIR) and metal sensitive Co K-edge x-ray absorption spectroscopy (XAS). In a solid state, a temperature hysteresis of magnetization larger than 40 K was observed upon cyclic cooling-heating. So, the temperature of phase transition upon cooling is about 40 K lower than that upon heating. In solution, the x-ray absorption spectra for high-temperature and low-temperature states were similar to that in the solid form, but the hysteresis was absent. Two methods are can probe valence tautomer transition, but XAS has an advantage for the liquid phase analysis and FTIR has larger sensitivity to the ligand related interactions in solid.
Egorova et al discuss their study on a novel pyridine-containing azacrownethers for the chelation of therapeutic bismuth radioisotopes. The materials used in the study includes aqueous solutions, ...reagents, and fetal bovine sterile serum produced by HyClone. Competitive extraction techniques were used which are based on the separation of uncomplexed cations wherein complexed cations remain in aqueous solution.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Electrochemical reduction of pertechnetate ions is studied in acetate solutions on both mercury dropping and solid electrodes. It is found that electroreduction of TcO4− ions on the mercury dropping ...electrode occurs stepwise via the following route Tc(VII) → Tc(IV) → Tc(III) → Tc(0). Ammonium ions affect the reduction of pertechnetate ions by shifting potentials of polarographic waves in a positive direction.
Diffusion coefficients of Tc(VII) species in acetate solutions decreased from ~1 · 10−5 cm2 s−1 in a solution containing 2 mol dm−3 acetate ions to ~1.2 · 10−6 cm2 s−1 in a solution containing 8 mol dm−3 acetate ions. The Stokes radius of pertechnetate ion is 0.19 ± 0.01 nm.
Technetium coatings were characterized using X-ray absorption spectroscopy (XANES/EXAFS). It is shown that technetium is in the metallic state in the electrolytic deposits; however, the obtained metal is amorphous. The Tc-Tc interatomic distances and coordination numbers of Tc atoms in the deposits are determined. The distance between technetium atoms in the electrodeposits is slightly less (0.262 nm) compared to technetium foil (0.272 nm).
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•Metallic technetium can be electrodeposited from aqueous ammonia-acetate solutions.•Electroreduction of pertechnetate ions proceeds stepwise via the route Tc(VII) → Tc(IV) → Tc(III) → Tc(0).•The obtained technetium coatings are amorphous.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The characterization of quaternary alloys is a particularly complex task. However, EXAFS is a powerful method, suitable to obtain information about the local atomic structure of a sample and to ...analyze the ion distributions within any defined configuration. In the truly quaternary InAsPSb alloy we collected EXAFS spectra at different atomic edges and their Fourier Transform were analyzed using the multivariate Partial Least Square Regression method. The InAsPSb structure and its ion distributions within the twelve multinary configurations were determined together with site occupation preferences. The sphalerite structured InAsPSb alloy is characterized in the metastable range, by preferences with a significantly attenuated value, a condition that enhances the populations of its three symmetrical binary configurations. The attenuations, respect to Bernoulli distributions, for the metastable growth region and beyond this region were also evaluated for the first time.
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•Deviation from random of the ion distribution in a set of quaternary InAsPSb alloys.•Selection of reliable FT-EXAFS spectra by multivariate statistical analysis.•Determination of CN for the 12 multinary configurations in InAsPSb alloys.•Ion distribution evaluation in metastable & miscibility regions of quaternary alloys.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
9.
First cage-like pentanuclear Co(ii)-silsesquioxane Bilyachenko, A N; Yalymov, A I; Levitsky, M M ...
Dalton transactions : an international journal of inorganic chemistry,
01/2016, Volume:
45, Issue:
35
Journal Article
Peer reviewed
A new pentanuclear "cylinder"-like cobalt(ii) phenylsilsesquioxane (PhSiO1.5)10(CoO)5(NaOH) exhibits a slow relaxation of the magnetization and a high catalytic activity and stereoselectivity in the ...oxidation of alkanes and alcohols.
