- Synthesis, characterisation and catalytic performance of nanocrystalline Co3O4 for gas-phase chlorinated VOC abatement
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Several nanocrystalline Co3O4 catalysts were investigated for their activity and selectivity during the oxidation of 1,2-dichloroethane, which was selected as a model chlorinated volatile organic compound. A wide number of synthesis routes starting from cobalt(II) nitrate were examined, namely calcination of the precursor salt, solid-state reaction, precipitation and sol-gel. The catalysts prepared by precipitation decomposed the chlorinated feed at the lowest temperatures. Activity was observed to be chiefly governed by a small crystallite size which may give rise to more easily accessible active sites (oxygen -O- or O2-- species), which were not present on the more highly crystalline Co3O 4 catalysts. Additionally, surface Lewis acidity played a relevant catalytic role. Interestingly, the behaviour of some of the nanocrystalline oxides was superior to that of supported noble metal catalysts and other bulk oxide catalysts. Conversion to deep oxidation products was complete (CO 2, HCl and Cl2), and no appreciable deactivation with time on stream was noticed.
- De Rivas, Beatriz,Lopez-Fonseca, Ruben,Jimenez-Gonzalez, Cristina,Gutierrez-Ortiz, Jose I.
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- Thermogravimetric study of the kinetics of Co3O4 reduction by hydrogen
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Cobalt(II,III) oxide (Co3O4), synthesized by gel-combustion method, thermally treated in air at temperatures 400, 600 and 800 °C, was subjected to the reduction to metallic state in hydrogen atmosphere. The reduction was carried out
- Tomi?-Tucakovi?, Biljana,Majstorovi?, Divna,Jeli?, Dijana,Mentus, Slavko
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- Co nanoparticles embedded in a 3D CoO matrix for electrocatalytic hydrogen evolution
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Earth-abundant and highly efficient electrocatalysts for the hydrogen evolution reaction (HER) are desired for hydrogen production from water-splitting. Here, Co nanoparticles were embedded in the 3D CoO matrix via a template-free method, including cobalt hydroxy-carbonate nanowire arrays grown on Ni foam and the following non-contact Al-reduction process. The as-prepared 3D hierarchical structured Co/CoO nanowires possess good charge transfer and mass transport properties, and a synergistic effect at the Co/CoO interface can hugely facilitate the HER kinetics. A suitable balance between Co and CoO in the catalyst is crucial for high catalytic activity. And the optimal Co/CoO array exhibited outstanding HER activities in 1 M NaOH, achieving nearly zero onset potential, and a current density of 100 mA cm-2 with a small overpotential of 167 mV. They also showed good long-term stabilities. This hybrid Co/CoO nanowire array is a promising material for large-scale hydrogen production from water-splitting.
- Liu, Xiangye,Dong, Chenlong,Dong, Wujie,Wang, Xin,Yuan, Xiaotao,Huang, Fuqiang
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- Electrochemical deposition of co under the influence of high magnetic fields
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The effect of uniform, vertically oriented high magnetic fields up to 13 T on the electrodeposition of Co has been investigated in dependence on the cell and electrode geometry as well as the orientation and strength of the magnetic flux density by means of cyclic voltammetry, chronoamperometric measurements, and atomic force microscopy investigations. In the majority of cases, the limiting current density ilim increases with increasing magnetic flux densities independent of the cell geometry and orientation. The current efficiency of Co increases with increasing magnetic flux densities only in magnetic fields aligned parallel to the electrodes due to the magnetohydrodynamic (MHD) effect. The morphology of the deposits exhibits randomly oriented round-shaped grains. The electrochemical behavior of horizontal electrodes with magnetic fields oriented perpendicular to the surface is strongly dependent on the electrode geometry. The current efficiency of the Co deposition on flat electrodes increases for low magnetic flux densities and keeps constant for high magnetic fields. In contrast, for wall electrodes the current efficiency decreases strongly even for low magnetic fields. These results are caused by overlapping effects of two types of convection, macro-MHD- and micro-magneto convection due to gradients of the concentration and the magnetic susceptibility. This leads to a modified morphology.
- Uhlemann,Krause,Chopart,Gebert
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- Highly crystalline anisotropic superstructures via magnetic field induced nanoparticle assembly
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A magnetic field is successfully utilized to induce the fabrication of size controllable one-dimensional (1-D) supercrystals which are composed of a highly crystalline assembly of fcc-packed cobalt nanoparticles; the anisotropy associated supercrystal magnetism is enhanced with four times higher coercivity than that of randomly aggregated nanoparticles. The Royal Society of Chemistry.
- Park, Jong-Il,Jun, Young-Wook,Choi, Jin-Sil,Cheon, Jinwoo
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- Synthesis, characterization, and tunable optical properties of hollow gold nanospheres
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Nearly monodisperse hollow gold nanospheres (HGNs) with tunable interior and exterior diameters have been synthesized by sacrificial galvanic replacement of cobalt nanoparticles. It is possible to tune the peak of the surface plasmon band absorption betwe
- Schwartzberg, Adam M.,Olson, Tammy Y.,Talley, Chad E.,Zhang, Jin Z.
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- Effect of temperature on Co electrodeposition in the presence of boric acid
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The electrodeposition of cobalt from sulphate solutions containing boric acid was investigated using EQCM technique coupled with potentiostatic measurements. The boric acid was added to electrolyte as a buffer to avoid the local pH rise caused by parallel hydrogen evolution reaction (HER). The results showed that the buffer contribution of boric acid is effective in the cobalt electrodeposition at 25 °C; however, cobalt hydroxide is formed simultaneously with cobalt deposition at 48 °C. The M/z values calculated using the Sauerbrey equation and the Faraday Law showed that in the initial stages of deposition at 48 °C, only cobalt deposits were detected, but after 2 s, an important amount of Co(OH)2 started to be formed.
- Santos,Matos,Trivinho-Strixino,Pereira
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- Paramagnetic alkyl, hydride, and alkene complexes of the Tpt-Bu,MeCo moiety
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The paramagnetic 15-electron alkyls Tpt-Bu,MeCo(R) (R = Me, Et, n-Bu) have been prepared, and the closely related Tpt-BuCo(Me) has been structurally characterized. Hydrogenation of Tpt-Bu,MeCo(N2) produced the a
- Jewson, Jennifer D.,Liable-Sands, Louise M.,Yap, Glenn P. A.,Rheingold, Arnold L.,Theopold, Klaus H.
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- Preparation and Properties of Cobalt(II) Hydroxide-(Sodium Fluoride Tetrasilicic Mica) Intercalation Complexes and of Highly Dispersed Cobalt on Mica
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Cobalt(II) hydroxide-(sodium fluoride tetrasilicic mica) intercalation complexes were prepared by titrating cobalt(II) nitrate solutions in the presence of mica with sodium hydroxide under oxygen-free conditions.These complexes were characterized by chemical analysis, XRD, DTA-TGA, IR, and surface area measurements.These confirmed that the brucite-like cobalt(II) hydroxyde sheet developed within the interlayer of the silicate.Cobalt atoms reduced at 400-700 deg C by H2 migrated from the interlayer of the silicate to the external surface of these where highly dispersed cobalt particles were formed.Ultra-fine cobalt metals (50-200 Angstroem) with a hexagonal close-packed form were prepared at 400 deg C by H2.The degree of reduction and the grain diameter of cobalt increased with an increase of the reducing temperature and/or the reducing time.
- Ohtsuka, Kunio,Koga, Johji,Suda, Mitsuru,Ono, Mikiya,Takahashi, Minoru
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- Effects of heat treatments on the ductility of cobalt electrodeposits
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The effects of annealing treatments on the structure and mechanical properties of cobalt electrodeposits have been studied. Annealing temperatures range from 250-800°C, i.e. below, as well as above, the allotropic α-h c p ? β-f c c transformation temperature (417°C). The structural characterization included hydrogen content measurement, relative volume fraction of α and β phases determination by X-ray diffraction, and microstructural investigations by optical and electron microscopy. The results showed that an annealing is a very effective means to optimize the ductility of cobalt electrodeposits. The increase of ductility observed after annealing is essentially due to a decrease of the stacking fault density in the deposits. Annealing treatment above the allotropic transformation temperature also produces, in some deposits, an increase of the ductile β-f c c phase content, but this fact does not lead to supplementary improvements of ductility. This is due to the detrimental influence of hydrogen that always exists in these deposits.
- Dille,Charlier,Winand
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- Preparation and magnetic properties of anisotropic (Sm,Pr)Co5/Co composite particles
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Anisotropic (Sm,Pr)Co5/Co nanocomposite particles have been fabricated by chemical coating the 2 h ball milled (Sm,Pr)Co5 flakes with Co nanoparticles. The Co nanoparticles were synthesized with mean particle sizes in the range of 2050 nm. The nanocomposite particles present [0 0 1] out-of-plane texture and improved magnetic properties, e.g., an enhanced remanent magnetization of 72 emu/g for (Sm,Pr)Co5/Co and 66 emu/g for (Sm,Pr)Co5. In addition, by using the 8 h ball milled powders (much smaller than the 2 h ball milled powders) as the starting materials, Co nanoparticles can also be successfully coated on the surface of the flakes. A plausible mechanism for the formation of Co nanoparticles on the surface of (Sm,Pr)Co5 flakes is discussed.
- Wang, Xiaoliang,He, Huanlong,Wang, Fengqing,Chen, Yan,Xu, Lei,Li, Xiaohong,Zhang, Xiangyi
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- A study on electrochemical growth behavior of the Co-Ni alloy nanowires in anodic aluminum oxide template
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This study shows the growth behavior of Co-Ni alloy nanowires in AAO template. Growth of nanowires consists of four different stages namely electronucleation, steady state growth, filling of pores, and coverage of filled nanowires and forming of a film on
- Ghahremaninezhad,Dolati
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- Highly conformal deposition of pure Co films by MOCVD using Co2 (CO)8 as a precursor
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Highly conformal Co thin films were deposited on Si O2 trenches with an aspect ratio of 13 by metallorganic chemical vapor deposition (MOCVD) using Co2 (CO)8 as a precursor in a low-temperature regime of 50-70°C where the growth rate was 3.5-7.0 nmmin. Lowering the pressure of the process reduces the number of collisions in the gas phase and, thus, widens the temperature regime in which the surface reaction controls the growth rate. A processing pressure of 26.7 Pa (0.2 Torr) allows for conformal deposition only at 50°C, whereas deposition at a reduced pressure of 4.0 Pa (0.03 Torr) widens the temperature regime (50-70°C) in which excellent conformality can be obtained. The conformal Co thin film, produced at 50°C and 4.0 Pa, showed a resistivity of 10-12 μ cm and contained 1.0 atom % oxygen and less than 1.0 atom % carbon. After annealing this film at 600°C, its resistivity was reduced to 6 μ cm, which is close to the bulk resistivity (5.7 μ cm) of Co. Therefore, this low-temperature process, which allows for the excellent conformal deposition of pure Co films, can be utilized to produce silicided contacts for advanced devices which require a low contact resistance and good electrical performance.
- Lee,Yang,Lee,Kim,Nam,Shin,Ko,Lee,Lee,Kim
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- Partial oxidation of methane to synthesis gas using LnCoO3 perovskites as catalyst precursors
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In this work a series of cobalt-containing perovskites LnCoO3 (Ln = La, Pr, Nd, Sm, and Gd) has been studied as catalyst precursors for the partial oxidation of methane to synthesis gas. All the perovskite precursors were prereduced in situ, producing cobalt metal finely dispersed over the rare earth sesquioxide support described here as Ln-Co-O. Of the catalyst tested the system Gd-Co-O showed exceptionally better performance for CO and H2 production (with methane conversion of 73% and selectivities of 79 and 81% for CO and H2, respectively, at 1009 K). The production of synthesis gas over the other catalysts decreased in the following order: Sm-Co-O ? Nd-Co-O > Pr-Co-O. The catalyst La-Co-O was active for methane combustion and only traces of CO and H2 were observed under the reaction conditions. XRD and XPS analyses of the catalyst La-Co-O showed that under the reaction conditions the cobalt metal is completely reoxidized, regenerating the original LnCoO3 perovskite structure. For the reaction over Nd-Co-O the cobalt is only partially reoxidized to NdCoO3. For Gd-Co-O and Sm-Co-O, the most stable and active catalysts for the partial oxidation of methane no reoxidation to LnCoO3 was observed. TPR and XRD studies showed that the perovskite NdCoO3 is reduced in two steps, first to NdCoO2.5 and further to Co°/Nd2O3 and in both stages it was demonstrated that the reoxidation with O2 is capable of recovering the perovskite structure. TPO experiments with reduced La-Co-O, Nd-Co-O, Sm-Co-O, and Gd-Co-O catalysts indicated that reoxidation of cobalt also takes place in two steps: first by oxidation of the supported Co° to the spinel Co3O4 (Co2+Co3+2O4) followed by a further oxidation of the Co2+ to Co3+ with a simultaneous solid state reaction with Ln2O3, regenerating the perovskite structure. It was observed that the temperature for the second oxidation step is strongly dependent on the nature of the lanthanide. Based on these results it is proposed that the deactivation of the catalysts Ln-Co-O by reoxidation of cobalt metal is related to the thermodynamic stability of the parent perovskite structure. We also present evidence that hydroxyl groups on the rare earth oxide, specially in the La-Co-O system, might make some contribution to the reoxidation of cobalt metal during the reaction via a reverse spillover process.
- Lago,Bini,Pena,Fierro
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- Synthesis of Co submicrospheres self-assembled by Co nanosheets via a complexant-assisted hydrothermal approach
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Co submicrospheres with the typical diameter of ca. 500 nm, and possessing beautiful morphologies composed of dense Co nanosheets ca. 10 nm thick, were synthesized by a facile and low-cost complexant-assisted hydrothermal approach. Magnetic measurement at room temperature indicated the coercivity of the submicrospheres reached 268 Oe, which was much higher than that of bulk Co and of some microstructure cobalt materials reported previously. Hexagonal close-packed (hcp) and face-centered cubic (fcc) cobalt phases in the materials were identified by X-ray diffractometer (XRD). It was revealed that the addition of the complexant sodium tartrate played a crucial role in the formation of the hierarchical architectures of the Co submicrospheres. We believe that the high coercivity of the synthesized submicrospheres may result from their special nano-micro structure, and we suggest that this low-cost and facile synthesis approach can be used for large-scale production of Co magnetic materials with special structures and morphologies, as well as excellent magnetic properties.
- Li, Hao,Jin, Zhen,Song, Huiyu,Liao, Shijun
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- Homogeneous WC-Co-cemented carbides from a cobalt-coated WC powder produced by a novel solution-chemical route
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A solution chemical route to cobalt-coated WC-powder is described that allows for the preparation of WC-Co powders and compacts having a carbon content very close to the desired carbon content even under an inert atmosphere. The microstructural homogeneity in the sintered WC-Co composites when using the Co-coated grains was found to be superior as compared with conventionally mill-mixed powders, and the structural changes in the individual WC-grains were found to be much smaller, which is ascribed mainly to the fact that the coated grains do not require a grinding step leading to the formation of a tail of smaller WC grain sizes.
- Ekstrand, Asa,Westin, Gunnar,Nygren, Mats
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- Magnetic and microwave absorbing properties of Co-Fe thin films plated on hollow ceramic microspheres of low density
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Conductive and magnetic microspheres are fabricated by plating of Co-Fe alloy thin films on hollow ceramic microspheres of low density for the application to lightweight microwave absorbers. Metal plating was carried out in a two-step electroless plating process (pre-treatment of sensitizing and subsequent plating). Uniform coating of the film with about 2μm thickness was identified by SEM. High-frequency magnetic and microwave absorbing properties were determined in the rubber composites containing the metal-coated microspheres. Due to the conductive and ferromagnetic behavior of the Co-Fe thin films, high dielectric constant and magnetic loss can be obtained in the microwave frequencies. In particular, the magnetic loss increases with Fe content in the alloy films and its frequency dispersion can be explained by ferromagnetic resonance theory. Due to the electromagnetic properties, high absorption rate and thin matching thickness are predicted in the composite layers containing the metal-coated microspheres of low density (about 0.8g/cc) for the electromagnetic radiation in microwave frequencies.
- Kim, Sung-Soo,Kim, Seon-Tae,Ahn, Joon-Mo,Kim, Keun-Hong
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- Ion beam induced chemical vapor deposition (IBICVD) of cobalt particles
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A novel method aiming at fabricating submicron-scale particles utilizing dicobalt octacarbonyl as a precursor for cobalt, formed upon localized ion beam induced decomposition, is presented. Patterns of deposited particles are fabricated through vector scan rastering. Measurements of cumulative magnetic properties (arrays of 2 μm-size dots) show coercivity of about 100 Oe and the saturation magnetization of approximately 1000 emu/cm3.
- Lapicki, Adam,Ahmad, Ehsan,Suzuki, Takao
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- Surfactant-assisted hydrothermal synthesis of chains self-assembled by cobalt microspheres
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Magnetic cobalt chains, self-assembled by microspheres of hexagonal-phase cobalt, have been synthesized at 100 °C via a hydrothermal reduction route in the presence of cobalt chloride, the surfactant sodium dodecylsulfate (SDS) (or cetyltrimethylammonium bromide CTAB) and the complex reagent sodium tartrate. As-synthesized, the chains are 100-300 μm in length and the cobalt microspheres, which consist of nanosheets with an average thickness of about 60 nm, are 5-10 μm in diameter. The magnetic hysteresis loops at 5 K and 300 K of the chains of microspheres show ferromagnetic characteristics. The morphologies of the microspheres can be controlled by adjusting the concentrations of the surfactant and the complex reagent and also the reaction temperature.
- Zhang,Ma,Li,Wang,Zhang
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- Structure and properties of layered perovskites Ba1-xLnxFe1-yCoyO3-δ (Ln = Pr, Sm, Gd)
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A series of samples of overall composition Ba1-xLnxFe1-yCoyO3-δ (Ln = Pr, Sm, Gd) with x = 0.3–0.4; y = 0–0.5 were prepared by glycerin nitrate technique in air. The crystal structure of single-phase Ba1-xLnxFe1-yCoyO3-δ (Ln = Pr, Sm, Gd) determined by XRD was described as cubic (sp. gr. Pm3ˉm). However, transmission electronic microscopy revealed that both Sm- and Gd-doped oxides possess tetragonal structure with 5-fold and 3-fold increased c parameter respectively. Oxygen content in the complex oxides has been determined in air over wide temperature range by means of thermogravimetry and iodometric titration. The change in oxygen content with temperature for the phases with five-layered ordering was significantly smaller than for the disordered phases.
- Volkova,Mychinko, M. Yu.,Golovachev,Makarova,Bazueva,Zyaikin,Gavrilova, L. Ya.,Cherepanov
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- The structure and mechanical properties of thick cobalt electrodeposits
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Cobalt electrodeposits have been produced in chloride solutions. Depending on the electrolysis parameters applied, two different structures for the electrodeposits, namely α and β cobalt were observed. Their characterization included hydrogen content measurement, the relative volume fraction of the α and β phases determined by X-ray diffraction, X-ray diffraction line profile analysis and microstructural investigation by optical microscopy, scanning electron microscopy and transmission electron microscopy. The influence of structure on mechanical properties was examined. The results showed that the ductility properties of the cobalt electrodeposits were highly sensitive to the structure. A higher β phase content that was measured in some deposits did not improve the ductility due to the existence of trapped hydrogen which always exists in such deposits. However, annealing treatments seem to be a promising route to optimize the ductility of cobalt electrodeposits.
- Dille,Charlier,Winand
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- Redox energetics and enthalpy increments of GdBaCo2O6-δ
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The enthalpy increments for the GdBaCo2O6-δ double perovskite were determined by means of drop calorimetry in air in the temperature range between 365.4 K and 1272.4 K. The heats of orthorhombic I→orthorhombic II phase transition at 347.2 K and orthorhombic II→tetragonal transition at 745.8 K are equal to (2.95 ± 0.07) kJ·mol?1 and (2.40 ± 0.09) kJ·mol?1, respectively, as measured with differential scanning calorimetry for GdBaCo2O6-δ. These calorimetric data were used to determine the heat capacity of GdBaCo2O6-δ and the high-temperature ‘chemical’ contribution to the enthalpy increments, caused by the oxygen exchange. The differentiation of the ‘chemical’ contribution with respect to oxygen nonstoichiometry yielded the partial molar enthalpy of oxygen in the GdBaCo2O6-δ, which agrees well with the previously reported results. The enthalpy increment data of nonstoichiometric oxides have proven itself as a valuable source of redox energetics information.
- Tsvetkov,Sednev-Lugovets,Sereda,Malyshkin,Ivanov,Zuev, A.Yu
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- Crystal Structure of Solid Solutions in the Sm2 O3 –CaO–MO and Ln2 O3 –SrO–MO Systems (Ln = Sm, Gd; M = Fe, Co)
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Abstract: Complex oxides in the Sm2O3–CaO–MO and Ln2O3–SrO–MO systems (Ln = Sm, Gd; M = Fe, Co) were prepared via the glycerol-nitrate technique at 1100°С in air. The homogeneity ranges for the solid solutions w
- Khvostova,Galayda,Maklakova,Baten’kova,Startseva,Volkova,Gavrilova, L. Ya.,Cherepanov
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- Preparation of large Co nanosheets with enhanced coercivity by a magnetic-field-assisted solvothermal approach free of surfactants, complexants or templates
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We presented a magnetic-field-assisted solvothermal route to prepare hexagonal close-packed (hcp) large Co nanosheets free of any surfactants, complexants or templates. Scanning electron microscope (SEM) images showed that the typical size and thickness o
- Li, Hao,Liao, Shijun
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- Electrodialytic recovery of cobalt(II) with liquid membranes based on di(2-ethylhexyl)phosphoric acid
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Electrodialytic transfer of cobalt(II) from sulfuric acid solutions across liquid membranes containing di(2-ethylhexyl)phosphoric acid with addition of tri-n-octylamine in 1,2-dichloroethane was studied, with the metal electrodeposited from dilute solutio
- Sadyrbaeva
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- Synthesis of "solid solution" and "core-shell" type cobalt-platinum magnetic nanoparticles via transmetalation reactions
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In this article, we report the synthesis of "solid solution" and "core-shell" types of well-defined Co-Pt nanoalloys smaller than 10 nm. The formation of these alloys is driven by redox transmetalation reactions between the reagents without the need for a
- Park,Cheon
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- Complexant-assisted fabrication of flowery assembly of hexagonal close-packed cobalt nanoplatelets
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Flowery assembly of hexagonal close-packed (hep) cobalt nanoplatelets was fabricated in high yield via a simple one-pot method without any surfactants. The process involved the reduction of the precursor of cobalt dimethylglyoximate with hydrazine in a basic medium. Thus-prepared cobalt flowers exhibited a ferromagnetic characteristic with the coercivity of 308 Oe at room temperature, much higher than that of bulk counterpart. Copyright
- Ni, Xiaomin,Li, Dongguo,Zhang, Yongfeng,Zheng, Huagui
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- The origin of triple conductivity and water uptake in layered double perovskites: A case study on lanthanum-substituted GdBaCo2O6?δ
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Some layered double perovskite cobaltites have been shown recently to absorb water and exhibit increasing electrical conductivity in humid atmospheres. However, the assumptions that their crystal lattice is capable of proton uptake, and that these oxides really possess triple (oxide ion, protonic and electronic) conductivity, have already been brought into question. We investigated in detail the crystal structure and phase composition of various lanthanum-substituted GdBaCo2O6?δ and came to several important conclusions. Firstly, in oxidative conditions (e.g. in air), the substitution of La for either only Gd or only Ba in GdBaCo2O6?δ results in formation of multiphase materials. For example, BaCo1–xGdxO3?δ exsolves from Gd1–xLaxBaCo2O6?δ due to the redistribution of La between Gd and Ba sites in Gd1–xLaxBaCo2O6?δ lattice. Secondly, a single-phase double perovskite can be synthesized in air only by simultaneously substituting, within certain limits, both Gd and Ba in GdBaCo2O6?δ with La. Finally, using Gd0.8La0.2Ba0.95La0.05Co2O6?δ and BaCo0.8Gd0.2O3?δ as examples, we demonstrated that while single-phase double perovskite does not hydrate, in the same conditions, the cubic perovskite BaCo0.8Gd0.2O3?δ (BaCo1–xGdxO3?δ is encountered in Gd1–xLaxBaCo2O6?δ as an impurity) absorbs significant amount of water. Thus, the water uptake by lanthanum-substituted GdBaCo2O6?δ is most likely to occur due to the impurities, and not the main double perovskite phase.
- Ivanov, Ivan,Malyshkin, Dmitry,Novikov, Andrey,Sereda, Vladimir,Tsvetkov, Dmitry,Zuev, Andrey
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- Field emission from well-aligned zinc oxide nanowires grown at low temperature
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Field electron emission from vertically well-aligned zinc oxide (ZnO) nanowires, which were grown by the vapor deposition method at a low temperature of 550°C, was investigated. The high-purity ZnO nanowires showed a single crystalline wurtzite structure. The turn-on voltage for the ZnO nanowires was found to be about 6.0 V/μm at current density of 0.1μA/cm2. The emission current density from the ZnO nanowires reached 1mA/cm2 at a bias field of 11.0 V/μm, which could give sufficient brightness as a field emitter in a flat panel display. Therefore, the well-aligned ZnO nanowires grown at such low temperature can promise the application of a glass-sealed flat panel display in a near future.
- Lee,Lee,Lyu,Zhang,Ruh,Lee
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- Magnetic properties and structure of electrodeposited ZnCo alloys granular thin films
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We present several results concerning the preparation by means of electrolysis and characterization of ZnCo alloys thin films. Films of Zn, Co and ZnCo with various compositions (816 at% Co) were prepared in sulfate baths, using potentiostatic control, envisaging applications in the domain of corrosion resistant magnetic sensors. The effects of applied voltage on the magnetic properties, microstructure and phase content of the electrodeposited ZnCo films were investigated. The applied voltage significantly influenced the film composition and their magnetic properties. These films, when deposited at an applied voltage of 4.5 V exhibited multiphase behavior due to the inclusion of new phases (cobalt hydroxide), whereas at 3.0 V, only ZnCo alloys were deposited. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).
- Vlad,Pascariu,Tanase,Pinzaru,Dobromir,Nica,Georgescu
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- Organic colloid method to prepare ultrafine cobalt nanoparticles with the size of 2?nm
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Ultrafine Co nanoparticles with the size of ca. 2 nm were prepared by an organic colloid method, in which sodium formate acted as reducing agent, ethylene glycol acted as solvent, sodium citrate acted as both complexing agent and stabilizing agent, respectively. X-ray diffraction (XRD) analysis indicated that the as-prepared Co nanoparticles were in hexagonal close-packed phase, and transmission electron microscope (TEM) images revealed that the size of the well-dispersed Co nanoparticles was as small as 2 nm, and the sizes were distributed in a very narrow region. The hysteresis loop of the as-prepared Co sample measured at room temperature showed a superparamagnetic behavior due to the extremely small size of the products. It was revealed that sodium citrate played a crucial role in decreasing the particle size and narrowing the size distribution.
- Li, Hao,Liao, Shijun
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- Designed synthesis of cobalt and its alloys by polyol process
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The role of polyol, precursor and reaction promoting agents in the synthesis of metal and alloy nanoparticles using polyol process has been investigated by analyzing the reaction steps involved in the synthesis of cobalt in Co ion-polyol-[OH-] ion system in detail. The reducing potential of polyols and the easiness with which any metal salt can react to form reducible complexes has been evaluated using the orbital molecular theory and the results were experimentally verified. The reduction limit of polyol and their extension using reaction promoting agents such as [OH-] ions is also explained. The reduction of cobalt is preceded by various reaction stages of complex/compound formation, which has been fully identified. Furthermore, the reducing form of cobalt has been identified as either cobalt alkoxide or cobalt hydroxide. The results confirmed that the complex forming reactions that take place prior to the formation of the precursor, which finally get reduced to metal, play a decisive role in determining the physical properties of the nanoparticles. The approach can be extended to reduce any metals or alloys using polyol process.
- Joseyphus,Matsumoto,Takahashi,Kodama,Tohji,Jeyadevan
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- A novel strategy to synthesize anisotropic SmCo5 particles from Co/Sm(OH)3 composites with special morphology
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In this study, we report a new strategy for preparing magnetically anisotropic SmCo5 single crystal particles by reductive annealing of precursors with specially designed nanostructures. The precursors containing urchin-shaped Co clusters and Sm(OH)3 nanorods were synthesized by a hydrothermal process. Then we coated these precursors of Co/Sm(OH)3 nanocomposites with Ca(OH)2, and the following thermal reduction generated SmCo5 particles, where the original size and morphology of the precursor were basically preserved after undergoing high temperature annealing. The single crystalline SmCo5 particles exhibit strong magnetic anisotropy and excellent room temperature magnetic properties: remanence of 8.1 kG, coercivity of 25.7 kOe, and a maximum energy product of 15.8 MGOe, which is one of the highest maximum energy products for chemically synthesized nanostructured SmCo5 particles presently reported.
- Li, Chenglin,Wu, Qiong,Ma, Zhenhui,Xu, Huanhuan,Cong, Liying,Yue, Ming
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- Characterization and testing of silica-supported cobalt-palladium catalysts for conversion of syngas to oxygenates
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Silica-supported Co-Pd catalysts were prepared by co-impregnation using 2 wt% Pd and two different cobalt loadings: 2 wt% (2Co-2Pd) and 10 wt% (10Co-2Pd). They were characterized by ICP-OES, H2-TPR, in situ XRD, DRIFTS, and activity/selectivity
- Kumar, Nitin,Smith, Miranda L.,Spivey
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- Surface modification of metallic Co nanoparticles
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Monodisperse Co nanoparticles were synthesized by thermal decomposition in the presence of aluminium alkyls yielding air-stable Co nanoparticles after surface passivation. Several procedures for surface modification of these pre-stabilized, metallic Co nanoparticles are presented, including direct anchoring of surface-active functional groups and biocompatible dextran layers as well as silica and polymer coatings. As a result, individually coated nanoparticles as well as microspheres can be obtained.
- Matoussevitch, Nina,Gorschinski, Angelika,Habicht, Wilhelm,Bolle, Jens,Dinjus, Eckhard,B?nnemann, Helmut,Behrens, Silke
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- Reactive deposition of ultrafine cobalt powders part I electrochemical investigation
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During the reactive deposition of cobalt powders, Co(OH)2 colloidal layers are formed at the electrode surface; the individual cobalt crystals are isolated by the Co(OH)2 colloid around the grain boundaries so that growth is inhibite
- Cui,Tseung
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- Investigation of Cu and Co multilayer deposition in aqueous ambient
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Electrochemical preparation of multilayers of Cu/Co(Cu) has been investigated using cyclic voltammetry and in situ atomic force microscopy. Potentiostatic pulse deposition of Copper and Cobalt has been shown to reduce the surface roughness of the electrodeposits. Multilayers of Cu/Co(Cu) have been grown electrochemically using pulse deposition technique. Formation of coherent multilayers has been demonstrated using grazing angle X-ray diffraction studies. Published by Elsevier Ltd.
- Gupta, Dhirendra,Nayak,Kaushik,Pandey
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- Phase equilibria, structure and properties of intermediate phases in the Sm2O3 – Fe2O3 – CoO and Sm2O3 – CaO – CoO systems
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Phase equilibria in the Sm2O3 – Fe2O3 – CoO and Sm2O3 – CaO – CoO systems were systematically studied at 1100 °C in air. The following solid solutions: SmFe1-xCoxOsub
- Galayda,Volkova,Gavrilova, L. Ya.,Balymov,Cherepanov
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- CVD synthesis of carbon nanotubes using a finely dispersed cobalt catalyst and their use in double layer electrochemical capacitors
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Carbon nanotubes (CNT) were obtained by chemical vapour deposition (CVD), decomposing turpentine oil over finely dispersed Co metal as a catalyst at 675°C. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images reveal that the nanotubes are densely packed and of 10-50 nm in diameter. The XRD pattern of purified CNT shows that they are graphitic in nature. Resistivity measurements of these CNT indicate that they are highly conducting. Hall measurements of CNT reveal that electrons are the majority carriers with a carrier concentration of 1.35×1020 cm-3. Cyclic voltammetry (CV) and constant current charging/discharging was used to characterise the behaviour of electrochemical double layer capacitors of purified CNT with H2SO4. For CNT/2 M H2SO4/CNT, a capacitance of 12 F g-1 (based on the weight of the active material) was obtained.
- Chatterjee,Sharon, Maheshwar,Banerjee, Rangan,Neumann-Spallart, Michael
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- Rethinking Co(CO3)0.5(OH)·0.11H2O: A new property for highly selective electrochemical reduction of carbon dioxide to methanol in aqueous solution
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Co(CO3)0.5(OH)·0.11H2O is usually acknowledged and used as a precursor to synthesize other nanomaterials. However, some important properties of Co(CO3)0.5(OH)·0.11H2O have not been discovered yet. Herein, we report an important new property of hollow urchin-like Co(CO3)0.5(OH)·0.11H2O for highly selective electrochemical reduction of carbon dioxide to methanol in NaHCO3 aqueous solution at -0.98 V versus saturated calomel electrode (SCE) with Faradaic efficiency of up to 97.0% under ambient conditions, which is superior to most of the electrocatalysts reported to date. Finally, this low-cost electrocatalyst shows great potential in CO2 conversion industry for practical application in the future.
- Huang, Jianzhi,Hu, Qiong,Guo, Xinrong,Zeng, Qiang,Wang, Lishi
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- The effect of cobalt and zinc precursors on Co (10%)/Zn (x%)/TiO 2 (x=0, 5) Fischer-Tropsch catalysts
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Co/Zn/TiO2 catalysts prepared from zinc/cobalt nitrate produced larger Co particles and more wax (>C16) when compared to the other catalyst combinations. A series of Co (10%)/Zn (x%)/TiO2 (x = 0, 5) catalysts were prepared from different nitrate and acetate precursors. TPR and chemisorption techniques revealed that a mixture of cobalt precursors (cobalt acetate and cobalt nitrate) on titania were more easily reduced when compared to Co (10%)/TiO2 catalysts prepared from either cobalt acetate or cobalt nitrate alone. By contrast, after addition of zinc, catalysts prepared from zinc acetate and cobalt nitrate had the most highly dispersed cobalt species when compared to catalysts prepared from the other combinations of nitrate and acetate precursors of zinc and cobalt. Mixed precursors of zinc and cobalt were also more active and had higher CO conversion in Fischer-Tropsch synthesis (FTS) when compared to catalysts prepared from: (i) both nitrate precursors or (ii) both acetate precursors of zinc and cobalt. However, the catalyst prepared from zinc nitrate and cobalt nitrate produced more wax (>C16) when compared to the other catalysts studied (50% versus 12-32% wax). Data suggest that larger Co particles correlate with wax production as well as reduced CO conversion. CO chemisorption data correlated better with the FT activity data than did Co XPS data.
- Madikizela-Mnqanqeni, Nobuntu N.,Coville, Neil J.
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- Kinetic features of thermal decomposition of cobalt acetylacetonate and development of catalysts for the oxidation of carbon monoxide, based on the decomposition products
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The kinetic features of thermal decomposition of cobalt acetylacetonate in a vacuum were elucidated, and the volatile thermolysis products were identified. The homogeneous-heterogeneous character of the process was shown. Catalysts for the oxidation of CO to CO2 were developed on the basis of cobalt acetylacetonate decomposition products and synthetic cellular ceramics, and the kinetic and activation parameters of the oxidation were determined. 2004 MAIK Nauka/Interperiodica .
- Tsyganova,Didenkulova,Shekunova,Faerman,Aleksandrov
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- Modeling of single phase electrocrystallization processes growth of paraboloids with concurrent evolution of hydrogen
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A generalized form of the current time transient (CTT) has been derived for the charge transfer controlled model of growth of paraboloids. The transient current is shown to pass through a single maximum before approaching a steady-state value. The maximum is estimated to be coincidental with 77% of the substrate coverage in the case of instantaneous micleation and with 90% coverage for the progressive nucleation and growth of paraboloids. The dependence of the surface area of the paraboloidal growth forms on time is formulated and, consequently, the kinetics of the concurrent evolution of hydrogen has been incorporated in the formulation of the CTTs. A particular CTT equation is thereby derived for the growth of paraboloids that are instantaneously formed on a monolayer of deposit. It is shown that the exact shape of some of the CTTs recorded during the electrocrystallization of cobalt can be reproduced by the derived CTT.
- Abyaneh
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- Magnetism of single-crystalline Co nanorods
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We report on the synthesis and preparation of oriented nanomaterials of single crystalline metallic Co nanorods of 6 nm in diameters and two different aspect ratios (7 and 15). They display optimized magnetic properties, with a spontaneous magnetization j
- Soulantica,Wetz,Maynadi,Falqui,Tan,Blon,Chaudret,Respaud
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- Signatures of spin-glass freezing in Co/CoO nanospheres and nanodiscs
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We present a study of the magnetic properties of Co nanoparticles having a combination of both spherical and disk shapes. The hcp Co nanospheres with an average diameter of 11 nm and nanodiscs of dimensions ~2.5×15 nm 2 were prepared by thermal decomposition of di-cobalt octacarbonyl in the presence of an amine surfactant. The as-synthesized nanoparticles were oxidized to grow an antiferromagnetic layer. High resolution transmission electron microscopy showed the presence of a ferromagnet/antiferromagnet (Co/CoO) interface with a 2.2-nm thick CoO shell on the spherical nanoparticles and 0.5 nm thick on nanodiscs. We report the temperature and field dependent DC magnetization, frequency, field, and temperature dependent AC susceptibility, and the radio frequency transverse susceptibility. A low temperature paramagnetic behavior was observed in the DC magnetization at high fields and is assigned to defects in the CoO shell that are not coupled to the antiferromagnetic lattice. Our results support the existence of a low temperature frozen, disordered magnetic state, characterized by a strong exchange coupling between the structurally disordered, spin-glass CoO shell and Co core.
- Srikala,Singh,Mehta,Patnaik
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- Catalytically active nano-porous cobalt-palladium alloys
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The potential advantages of nano-alloys and particularly, nano-porous alloys, place them at the “spotlight” of heterogeneous catalysis. Nevertheless, controlling the precise compositions of these materials is still a synthetic challenge. Previous research introduced the fabrication of metals and alloys with a high nano-scale porosity and controllable compositions, via a hydrogen-mediated chemical reduction process of metal complex salts. We have used this procedure to obtain two magnetic nano-porous Co-Pd alloys, pure porous palladium and pure porous cobalt. Single crystal X-ray diffraction studies enabled structural determination of the two Co-Pd bi-complex salts that were used as precursors for these alloys. Powder X-ray diffraction studies determined the crystalline phases of the alloys and indicated the nanometric size of their crystallites. High-resolution scanning electron microscopy indicated that these alloys assemble as highly porous clusters of interconnected nano-crystallites. It also indicated that each alloy cluster preserves the micrometric morphologies of its salt precursor. Energy dispersive X-ray spectroscopy showed that the alloys exhibit uniform composition down to the micro-level, which preserved the Co/Pd ratio within the salts. Focused ion beam tomography enabled 3D structural representation of the alloys and metals. Geometrical analysis of the 3D reconstructed data determined 90% porosity and a specific surface area of ~100 m2/g for the alloys. In addition, the alloys showed improved catalytic activity in the semi-hydrogenation of phenylacetylene, compared to the pure metals and commercial Pd/C. Moreover, their magnetic properties enabled facile recovery at the end of the reaction. The yield for styrene in this reaction was increased using “design of experiments” (DOE), a method for optimization of reaction conditions. Furthermore, our experiments implied that a highly porous structure significantly improves the selectivity of styrene in the reaction. These results demonstrated the advantage of fabricating nano-porous alloys with uniform compositions that may exhibit special properties and serve as new and efficient catalysts.
- Abu-Reziq, Raed,Avisar, Shay,Bino, Avi,Popov, Inna,Shner, Yahel
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- Effect of spark plasma sintering temperature on microstructure and thermoelectric properties of the cermet composites consisting of Bi2Te2.1Se0.9 matrix and Co@CoTe2 inclusions
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Novel cermet Bi2Te2.1Se0.9+0.33 ?wt% Co composite has been prepared via spark plasma sintering (SPS) the starting Bi2Te2.1Se0.9 and Co powders at different SPS-temperatures (TS ?= ?598, 623, 648 and 673 ?K). During the sintering, initial Co inclusions transform into final filler Co@CoTe2 (“core”-“shell”) inclusions, randomly distributed inside textured grained Bi2Te2.1Se0.9 matrix. Forming these inclusions is originated from high-temperature chemical interaction between Bi2Te2.1Se0.9 and Co. Main features in microstructure and thermoelectric properties of the cermet composite found with increasing TS are: (i) a texturing degree of grained Bi2Te2.1Se0.9 matrix gradually decreases that is attributed to reducing in ability of initial nanometer Co particles to act as lubricant; (ii) a fraction of the Co core decreases, and a fraction of the CoTe2 shell increases that is related to acceleration of Co→CoTe2 reaction at higher temperatures; (iii) the specific electrical resistivity and the Seebeck coefficient reduce, whereas the total thermal conductivity increases that can be originated from growth of electron concentration due to local Co doping. Highest value of the thermoelectric figure-of-merit equal to ~0.8 was observed for the composite, SPS-treated at 673 ?K.
- Ivanov, Oleg,Novikov, Vseslav,Vasil'ev, Alexei,Yaprintsev, Maxim,Zhezhu, Marina
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- Theoretical and Experimental Evaluation of the Reduction Potential of Straight-Chain Alcohols for the Designed Synthesis of Bimetallic Nanostructures
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Recently, the development of bimetallic nanoparticles with functional properties has been attempted extensively but with limited control over their morphological and structural properties. The reason was the inability to control the kinetics of the reduction reaction in most liquid-phase syntheses. However, the alcohol reduction technique has demonstrated the possibility of controlling the reduction reaction and facilitating the incorporation of other phenomena such as diffusion, etching, and galvanic replacement during nanostructure synthesis. In this study, the reduction potential of straight-chain alcohols has been investigated using molecular orbital calculations and experimentally verified by reducing transition metals. The alcohols with a longer chain exhibited higher reduction potential, and 1-octanol was found to be the strongest among alcohols considered. Furthermore, the experimental evaluation carried out via the synthesis of metallic Cu, Ni, and Co particles was consistent with the theoretical predictions. The reaction mechanism of metallic particle formation was also studied in detail in the Ni-1-octanol system, and the metal ions were confirmed to be reduced via the formation of nickel alkoxide. The results of this investigation were successfully implemented to synthesize Cu-Ni bimetallic nanostructures (core-shell, wire, and tube) via the incorporation of diffusion and etching besides the reduction reaction. These results suggest that the designed synthesis of a wide range of bimetallic nanostructures with more refined control has become possible.
- Ishijima, Masanao,Matsumoto, Takatoshi,Cuya Huaman, Jhon L.,Shinoda, Kozo,Uchikoshi, Masahito,Matsuo, Kohei,Suzuki, Kazumasa,Miyamura, Hiroshi,Balachandran, Jeyadevan
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p. 9432 - 9441
(2021/05/06)
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- In Situ Study of Reduction of MnxCo3- xO4Mixed Oxides: The Role of Manganese Content
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A series of Mn-Co mixed oxides with a gradual variation of the Mn/Co molar ratio were prepared by coprecipitation of cobalt and manganese nitrates. The structure, chemistry, and reducibility of the oxides were studied by X-ray diffraction (XRD), X-ray absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR). It was found that at concentrations of Mn below 37 atom %, a solid solution with a cubic spinel structure is formed. At concentrations above 63 atom %, a solid solution is formed on the basis of a tetragonal spinel, while at concentrations in a range of 37-63 atom %, a two-phase system, which contains tetragonal and cubic oxides, is formed. To elucidate the reduction route of mixed oxides, two approaches were used. The first was based on a gradual change in the chemical composition of Mn-Co oxides, illustrating slow changes in the TPR profiles. The second approach consisted in a combination of in situ XRD and pseudo-in situ XPS techniques, which made it possible to directly determine the structure and chemistry of the oxides under reductive conditions. It was shown that the reduction of Mn-Co mixed oxides proceeds via two stages. During the first stage, (Mn, Co)3O4 is reduced to (Mn, Co)O. During the second stage, the solid solution (Mn, Co)O is transformed into metallic cobalt and MnO. The introduction of manganese cations into the structure of cobalt oxide leads to a decrease in the rate of both reduction stages. However, the influence of additional cations on the second reduction stage is more noticeable. This is due to crystallographic peculiarities of the compounds: the conversion from the initial oxide (Mn, Co)3O4 into the intermediate oxide (Mn, Co)O requires only a small displacement of cations, whereas the formation of metallic cobalt from (Mn, Co)O requires a rearrangement of the entire structure.
- Bulavchenko, Olga A.,Afonasenko, Tatyana N.,Ivanchikova, Anastasya V.,Murzin, Vadim Yu.,Kremneva, Anna M.,Saraev, Andrey A.,Kaichev, Vasily V.,Tsybulya, Sergey V.
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p. 16518 - 16528
(2021/11/04)
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- Synthesis, spectral characterization, density functional theory studies, and biological screening of some transition metal complexes of a novel hydrazide–hydrazone ligand of isonicotinic acid
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Novel Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) complexes (1–7) of hydrazide–hydrazone ligand (H2L) derived from the condensation of isonicotinic acid hydrazide with (Z)-N′-(2-nitrobenzylidene)-3-oxobutanehydrazide have been prepared. The ligand and its chelates were characterized based on elemental analysis, spectral, thermal analysis, molar conductance, and magnetic moment measurements. Besides, density functional theory (DFT) computations have been conducted to study structures and energetics of the ligand and its complexes. The IR spectra showed that the ligand was chelated with the metal ion in a monobasic tridentate manner using ONO donors in all complexes except Zn(II) complex (5) where the ligand binds with Zn(II) ion as a dibasic tridentate utilizing ONO donors. The magnetic moment and electronic spectral data revealed octahedral and square pyramidal geometries for complexes (1, 7) and (2, 4, 5), respectively, whereas a square planar geometry was suggested for 3. DFT studies show that the Cd(II) center reveals interesting structural deviations from regular octahedral geometry in the resulting hexa-coordinated complex [Cd(H2L)2].2H2O (6) assumes a trigonal prismatic (TP) structure for this complex. The antibacterial and antifungal activities of the ligand and its complexes have been investigated with different bacterial and fungal strains. The data revealed that Hg(II) complex (7) demonstrated a very good antibacterial and antifungal activity than others. Highlights: A new hydrazide–hydrazone ligand of isonicotinic acid was synthesized. Seven mononuclear Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) complexes of the new ligand were prepared and characterized by different tools. DFT studies have been carried out to study the structure of the ligand and its complexes. Antimicrobial activities of the ligand and its complexes were studied against a variety of bacterial and fungal strains by using disk diffusion method and results were compared with standard drugs.
- El-Nahas, Ahmed M.,Kashar, Tahani I.,Tolan, Dina A.,Yoshizawa, Kazunari
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- Synthesis, dft calculations, antiproliferative, bactericidal activity and molecular docking of novel mixed-ligand salen/8-hydroxyquinoline metal complexes
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Despite the common use of salens and hydroxyquinolines as therapeutic and bioactive agents, their metal complexes are still under development. Here, we report the synthesis of novel mixed-ligand metal complexes (MSQ) comprising salen (S), derived from (2,2′-{1,2-ethanediylbis [nitrilo(E) methylylidene]}diphenol, and 8-hydroxyquinoline (Q) with Co(II), Ni(II), Cd(II), Al(III), and La(III). The structures and properties of these MSQ metal complexes were investigated using molar conductivity, melting point, FTIR,1H NMR,13C NMR, UV–VIS, mass spectra, and thermal analysis. Quantum calculation, analytical, and experimental measurements seem to suggest the proposed structure of the compounds and its uncommon monobasic tridentate binding mode of salen via phenolic oxygen, azomethine group, and the NH group. The general molecular formula of MSQ metal complexes is [M(S)(Q)(H2O)] for M (II) = Co, Ni, and Cd or [M(S)(Q)(Cl)] and [M(S)(Q)(H2O)]Cl for M(III) = La and Al, respectively. Importantly, all prepared metal complexes were evaluated for their antimicrobial and anticancer activities. The metal complexes exhibited high cytotoxic potency against human breast cancer (MDA-MB231) and liver cancer (Hep-G2) cell lines. Among all MSQ metal complexes, CoSQ and LaSQ produced IC50 values (1.49 and 1.95 μM, respectively) that were comparable to that of cisplatin (1.55 μM) against Hep-G2 cells, whereas CdSQ and LaSQ had best potency against MDA-MB231 with IC50 values of 1.95 and 1.43 μM, respectively. Furthermore, the metal complexes exhibited significant antimicrobial activities against a wide spectrum of both Gram-positive and-negative bacterial and fungal strains. The antibacterial and antifungal efficacies for the MSQ metal complexes, the free S and Q ligands, and the standard drugs gentamycin and ketoconazole decreased in the order AlSQ > LaSQ > CdSQ > gentamycin > NiSQ > CoSQ > Q > S for antibacterial activity, and for antifungal activity followed the trend of LaSQ > AlSQ > CdSQ > ketoconazole > NiSQ > CoSQ > Q > S. Molecular docking studies were performed to investigate the binding of the synthesized compounds with breast cancer oxidoreductase (PDB ID: 3HB5). According to the data obtained, the most probable coordination geometry is octahedral for all the metal complexes. The molecular and electronic structures of the metal complexes were optimized theoretically, and their quantum chemical parameters were calculated. PXRD results for the Cd(II) and La(III) metal complexes indicated that they were crystalline in nature.
- Abdalla, Ehab M.,Abdel Rahman, Laila H.,Al-Farhan, Badriah Saad,Basha, Maram T.,El-Ezz, Doaa Abou,El-Saghier, Ahmed M. M.,Marzouk, Adel A.,Shehata, Mohamed R.
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- Thermal stability and reduction mechanism of LiNi0.8Co0.1Mn0.1O2 and LiNi0.5Co0.2Mn0.3O2 cathode materials studied by a Temperature Programmed Reduction
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The temperature Programmed Reduction method was applied to analyze the structural and thermal behavior of LiNixCoyMnzO2 (x = 0.5 and 0.8). All reduction phases of LiNi0.5Co0.2Mn0.3O2 powder were transitioned above 843 K. For LiNi0.8Co0.1Mn0.1O2 powder, three reduction steps are starting at 661 K. It contributes to the transition to Ni2+, Co2+, Ni0, and Co0 phases, respectively. It was consistent with the reduction mechanism of LiNiO2 and LiCoO2. In delithiated NCM523, only a structural change from H1 to M is observed, which does not significantly affect thermal stability. For delithiated NCM811, the TPR result was sharply reduced to 536 K in the H2-H3 structural transition. When charged to 4.4 V, it decomposes into a NiO-like phase at 507 K. The reducing phase was verified through X-ray diffraction after all decomposition steps of the TPR results. As a result, the TPR method can confirm the reduction mechanism and thermal stability of the cathode material.
- Bakenov, Zhumabay,Kim, Jun-Sik,Kim, Sung-Soo,Lim, Seong-Hyeon,Umirov, Nurzhan,Yeon, Seon-Young
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- Enhanced electromagnetic wave absorption of hybrid-architectures Co? SiOxC
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Rational design on the well wrapped core-shell microstructure of Co? SiOxC composites was successfully conducted through reduction process of cobalt, efficient condensation reaction of KH-550 silane coupling agent as well as high temperature calcination. The SiOxC shell possessed 3D cross-linked network structure consisting of dielectric carbon and silicon composition for optimal electromagnetic matching. The microstructure, morphology, elements distribution, electromagnetic property and microwave absorption performance were fully characterized, respectively. This SiOxC shell effectively inhibited the agglomeration of cobalt particles, and regulated the complex electromagnetic parameters by decreasing permittivity and introducing polarization relaxation, all of which determined the efficient reflection loss with RLmin value of ?60.3 dB at 16.2 GHz and matching thickness of only 2.05 mm. Meanwhile, the effective absorption band is up to 7.1 GHz at 2.3 mm. By optimizing of core-shell structure and material components, the high-absorption performance was obtained through impedance matching, multi-interfacial polarizations, dipole (or defects) polarization and magnetic loss. Therefore, the Co? SiOxC composites present a facile and promising route toward the design of large-scale-preparation and excellent microwave absorbing materials.
- Cui, Yu,Ge, Jianwen,Li, Rui,Liu, Li,Meng, Fandi,Wang, Fuhui
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- Crystal Structure of the New Ordered Phases Based on Y2Ba3Fe3Co2O13 + δ
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Abstract: New phases with an ordered structure of the composition Y2Ba3Fe5 – yCoyO13 + δ (1.7 ≤ y ≤ 2.1) were obtained via the glycerol-nitrate technique. The regions of existence of two ty
- Bryuzgina, A. V.,Cherepanov, V. A.,Dyakova, A. V.,Mychinko, M. Yu.,Urusova, A. S.
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- Phase Equilibria and Structure of Complex Oxides in the 1/2 Nd2O3–CaO–CoO System in Air at 1373 K
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Abstract: X-ray powder diffraction and Rietveld full-profile analysis are used to establish the homogeneity ranges and crystalline structure of solid solutions Nd2?zCazO3?z/2 (0.0 ≤ z ≤ 0.1, space group (Formula presented.
- Aksenova, T. V.,Cherepanov, V. A.,Urusova, A. S.
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p. 2495 - 2501
(2020/12/07)
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- Thermal Expansion and Conductivity of Sm0.9Ca1.1Fe1 –yCo yO4 – δ Solid Solutions
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Abstract: Complex oxides Sm0.9Ca1.1Fe1 ? yCoyO4 ? δ (y = 0, 0.7) are synthesized in air at 1100°С using the glycerol-nitrate technique. The temperature dependences of the total electrical c
- Cherepanov, V. A.,Dyagileva, A. I.,Galayda, A. P.,Gavrilova, L. Ya.,Volkova, N. E.
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p. 2522 - 2526
(2020/12/07)
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- COMPOUND
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A purpose of the invention is to provide a novel compound. The novel compound is represented by M[i-C3H7NC(R)N-i-C3H7]2 (where, M=Co or Fe; R=n-C3H7 or i-C3H7) that is a liquid under 25° C. (at 1 atmospheric pressure).
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Paragraph 0128-0129
(2020/10/31)
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- Impact of gamma-ray irradiation on some aryl-amide-bridged Schiff-base complexes: spectral, TGA, XRD, and antioxidant properties
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Some aryl amide Schiff base Co(II), Ni(II) and Cu(II) distance between Cu(II) and complexes (1–7) have been obtained and identified by various analytical and spectroscopic tools. To through a light on the probability of structure changes with γ-irradiation, powder samples of complexes 1, 3, 5 and 6 were irradiated with 60Co γ-rays at dose of 100 kGy (hereafter referred to as 1F, 3F, 5F and 6F). Spectral, molar conductance, magnetic susceptibility, thermal, X-ray diffraction and antioxidant activity for the irradiated complexes were gained using similar methods used for the non-irradiated complexes. The data revealed that the irradiated complexes were not seriously affected by the utilized γ-irradiation dose.
- El-Boraey,El-Gammal,Abdel Sattar
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p. 241 - 252
(2019/12/09)
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- Porous amorphous FeCo alloys as pre-catalysts for promoting the oxygen evolution reaction
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The design and development of efficient electrocatalysts composed of earth-abundant elements for oxygen evolution have gained significant attention. In this study, a FeCo alloy electrocatalyst with an amorphous and porous structure was designed and prepared. The electrochemical test results showed that the amorphous alloy product with a Co:Fe molar ratio of 2:1 showed an optimal intrinsic catalytic activity for oxygen evolution. At a current density of 10 mA cm?2, only a small overpotential of 290 mV was required in a KOH solution (1 mol L?1), which is much lower than that for the monometallic catalyst (428 mV for amorphous cobalt for the same current density). The bimetal composition of this catalyst induced a strong synergistic effect. Moreover, it exhibited an amorphous and porous structure with a large number of exposed active sites along with high conductivity. These factors contributed to the excellent catalytic performance of this catalyst. This study provides an insight into the design of advanced oxygen evolution reaction catalysts.
- Zhu, Wenjuan,Zhu, Guoxing,Yao, Chengli,Chen, Hu,Hu, Jing,Zhu, Yi,Liang, Wenfu
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- Preparation of bimetallic metal-organic framework microflowers by spray method
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The NiCo-MOF microflowers are fabricated by a rapid spray method, which are assembled by 2D NiCo-MOF nanosheets with uniform crystal morphology and homogeneous dispersion of Ni and Co. Because of their large exposed active sites and nanoscale thickness, the NiCo-MOF microflowers exhibit good catalytic performance for the reduction of 4-nitrophenol.
- Zhang, Liying,Li, Linlin,Bai, Xiaojue,Xia, Mingjian,Shao, Lei,Wang, Tieqiang,Zhang, Xuemin,Li, Yunong,Qi, Xuan,Fu, Yu
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supporting information
p. 175 - 177
(2019/01/29)
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- A Study of the Crystal Structure of SmCaCo1?xFexO4?δ and Sm0.9Ca1.1Fe1?yCoyO4?δ Solid Solutions
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Complex oxides with general compositions SmCaCo1?xFexO4?δ and Sm0.9Ca1.1Fe1?yCoyCO4?δ are synthesized using the glycerol-nitrate technique at 1100 °C in air. By powder X-ray diffraction it is determined that SmCaCo1?xFexO4?δ solid solutions exist in a composition range 0 ≤ x ≤ 0.3 and Sm0.9Ca1.1Fe1?yCoyO4?δ solid solutions exist in a composition range 0 ≤ y ≤ 0.7. The samples with high concentrations of cobalt ions are found to crystallize in the tetragonal unit cell (space group I4/mmm), whereas the solid solutions enriched with iron ions have the orthorhombic structure (space group Bmab). For all single phase samples the unit cell parameters and volume and the structural parameters (atomic coordinates and bond lengths) are calculated by the full-profile Rietveld method.
- Galayda,Volkova,Startseva,Gavrilova, L. Ya.,Cherepanov
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p. 789 - 795
(2019/06/20)
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- Selective hydrogenation of quinolines over a CoCu bimetallic catalyst at low temperature
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Quinoline derivatives are widely exist in the environment, and mainly separated from the coal tar pitch fraction. Hydrogenation of these compounds to 1,2,3,4-tetrahydroquinolines, an important class of natural products and medicinal agents, is a significant transformation of waste to valuable chemicals. In the present work, we developed a cheap and highly efficient Co3Cu1Ox bimetallic catalyst and used it for the hydrogenation of quinolines at a temperature down to 60 °C. The introduction of Cu into Co catalyst changed the physical and chemical features of Co catalyst, which was characterized by Raman spectra, N2-adsorption/desorption isotherms, H2-TPR and H2-TPD tests. The recycling experiments indicated the catalyst was stable and possessed good reusability. Importantly, the gram-scale experiment provided a high yield (92%) to the target product, demonstrating that the catalytic system has a potential practical application.
- He, Zhen-Hong,Li, Na,Wang, Kuan,Wang, Wei-Tao,Liu, Zhao-Tie
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p. 120 - 126
(2019/04/10)
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- Hydrangea-like NiCo-based Bimetal-organic Frameworks, and their Pros and Cons as Supercapacitor Electrode Materials in Aqueous Electrolytes
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Hydrangea-like NiCo-based bimetal-organic frameworks (NiCo-MOF) are synthesized in DMF-EtOH solution via a solvothermal method, using 4,4′-biphenyldicarboxylic acid as a ligand. NiCo-MOF having a highest capacity of 1056.6 F·g–1 at 0.5 A·g–1 and 457.7 F·g–1 even at 10 A·g–1 is achieved at a Ni/Co/BPDC molar ratio of 1:1:1, a temperature of 170 °C and a reaction time of 12 hours. It exhibits secondary 3D microsphere structures assembled by primary 2D nanosheet structures, good crystalline structure and good thermal stability below 350 °C in air. All the electrochemical data show that NiCo-MOF has the pros and cons as supercapacitor electrode materials in aqueous electrolytes. On the one hand, NiCo-MOF has a high capacity even at a high current density, low internal resistance, charge-transfer resistance and ion diffusion impendence, owing to the ordered coordination structure, 2D nanosheet structure and 3D assembled microsphere structure of NiCo-MOF. On the other hand, the cycling stability and rate capability are not ideal enough due to the hydrolysis of coordination bonds in aqueous electrolytes, especially, in alkaline solution. The good dispersion and high electrochemical activity of metal ions bring a high capacity for NiCo-MOF, but they result in the poor stability of NiCo-MOF. In the future work, finding a suitable organic electrolyte is an effective way to enhance the cycling stability of NiCo-MOF as well as deriving more stable skeleton materials from NiCo-MOF.
- Li, Qiaoqin,Wang, Xiaoqin,Yang, Nana,He, Fan,Yang, Yufei,Wu, Bohua,Chu, Jia,Zhou, Anning,Xiong, Shanxin
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p. 1022 - 1030
(2019/08/07)
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- Noble Metal-free Bimetallic Cobalt/Manganese Oxide Catalyst for Hydrogen Generation by Decomposition of Hydrous Hydrazine
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Bimetallic cobalt and manganese oxide (Co/MnO) is prepared by annealing the spinel structure of CoMn2O4 under hydrogen environment. This noble metal-free catalyst is applied for hydrogen generation from aqueous hydrazine solution. X-ray powder diffraction, transmission electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy results indicated that the phase separation of metallic cobalt and manganese monoxide from CoMn2O4 occurs during annealing process. Co/MnO exhibits catalytic activity with the TOF value of 14.2 h?1 and 100% selectivity without generation of ammonia at 343 K. It is found that metallic cobalt plays role on the active site for hydrogen generation.
- Kim, Youngyong,Kwon, Ki-Young
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p. 1167 - 1171
(2019/11/13)
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- Highly improved acetone oxidation activity over mesoporous hollow nanospherical Mn:XCo3- xO4 solid solutions
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Hierarchical bimetal oxide solid solutions with mesoporous hollow-interior architecture have greatly promising applications in environmental catalysis due to their exceptional catalytic performances, while facile synthesis of such a unique architecture is still challenging. Herein, mesoporous hollow nanospherical (MHS) MnxCo3-xO4 solid solutions with tunable Mn/Co molar ratios in the spinel-type cubic crystal phase, fabricated by a facile solvothermal alcoholysis approach, have been developed to catalyze acetone oxidation for the first time. Experimental results confirm that MHS Mn1.20Co1.80O4 gave the optimal acetone oxidation activity, achieving 100% acetone conversion and 100% CO2 selectivity at 140 °C under the reaction conditions of acetone concentration = 1000 ppm, 20%O2/N2 and WHSV = ca. 93000 mL gcat-1 h-1. This superior activity of MHS Mn1.20Co1.80O4 can be mainly ascribed to the strong synergetic effect of the unique mesoporous hollow nanospherical feature, abundant oxygen vacancies and surface active oxygen species, the enhanced chemical nature resulting from the presence of more Mn4+, Mn3+ and Co3+ reactive sites, and the improved redox capacities. Kinetics studies provide direct evidence to validate the finding that the strong synergetic effect rather than individual factors played the critical role in determining the acetone oxidation activity. Meanwhile, a plausible catalytic mechanism of acetone oxidation over MHS MnxCo3-xO4 solid solutions has been proposed and elaborated in detail by elucidating the structure-activity relationship. Furthermore, MHS Mn1.20Co1.80O4 also presented excellent long-term stability and good water tolerance due to its highly stable crystal phase and robust morphological structure, showing good potential in eliminating volatile organic compounds.
- Wang, Jinguo,Zhang, Chi,Yang, Shuaifeng,Liang, Hao,Men, Yong
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p. 6379 - 6390
(2019/11/20)
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- Compound, thin film-forming material, and thin film manufacturing method
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A novel compound represented by the general formula (I) or (II) below: [in the formula, each of R1 and R2 independently represent a C1?12 hydrocarbon group, and Si(R3)3 is optionally substituted for a hydrogen atom in the hydrocarbon group; however, R1 and R2 are different groups; R3 represents a methyl or ethyl group; M represents a metal atom or silicon atom; and n is an integer from 1 to 4].
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-
Page/Page column 30-31
(2019/04/26)
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- Sustainable fixation of CO2 into epoxides to form cyclic carbonates using hollow marigold CuCo2O4 spinel microspheres as a robust catalyst
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The present work demonstrates the chemical fixation of CO2 for the synthesis of organic carbonates using mesoporous hollow marigold CuCo2O4 spinel microspheres as a catalyst prepared using the solvothermal method. The synthesized microspheres were characterized using contemporary analytical and spectroscopic tools. The CuCo2O4 spinel microspheres with the best morphological behaviour obtained after solvothermal treatment for 3 h were employed as a heterogeneous catalyst for the solvent-free conversion of epoxides and CO2 to generate cyclic carbonates. As a result, the model reaction of styrene oxide and CO2 revealed 94% conversion, 88% yield and 94% selectivity towards styrene carbonate in the presence of TBAI as a base under mild reaction conditions (80 °C, 20 bar, 3 h). Notably, the enhanced catalytic activity was attributed to the cooperative effect of the exposed Lewis acidic sites of CuCo2O4 and the efficient basic nature of TBAI. The effects of different reaction variables such as catalyst loading, temperature, pressure and time were investigated and discussed. Additionally, the effect of different bases was also experimentally determined. Further, the substrate scope using the CuCo2O4 and TBAI catalytic system revealed good performance towards CO2 fixation with a variety of terminal and internal epoxides. The catalyst was easily separated out after the reaction and tested for its recyclability. Results showed good recyclability up to five cycles without a substantial loss of catalytic activity. Based on the results obtained from XPS, XRD, and TPD and the available literature, an effort to predict a plausible mechanism was made in order to support the cycloaddition reaction. The present protocol is the first report of hollow marigold CuCo2O4 spinel microspheres as an outstanding and efficient catalyst with high selectivity towards fixation of CO2 into epoxides for cyclic carbonate formation.
- Prasad, Divya,Patil, Komal N.,Bhanushali, Jayesh T.,Nagaraja, Bhari Mallana,Jadhav, Arvind H.
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p. 4393 - 4412
(2019/08/22)
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- Ice Melting to Release Reactants in Solution Syntheses
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Aqueous solution syntheses are mostly based on mixing two solutions with different reactants. It is shown that freezing one solution and melting it in another solution provides a new interesting strategy to mix chemicals and to significantly change the reaction kinetics and thermodynamics. For example, a precursor solution containing a certain concentration of AgNO3 was frozen and dropped into a reductive NaBH4 solution at about 0 °C. The ultra-slow release of reactants was successfully achieved. An ice-melting process can be used to synthesize atomically dispersed metals, including cobalt, nickel, copper, rhodium, ruthenium, palladium, silver, osmium, iridium, platinum, and gold, which can be easily extended to other solution syntheses (such as precipitation, hydrolysis, and displacement reactions) and provide a generalized method to redesign the interphase reaction kinetics and ion diffusion in wet chemistry.
- Wei, Hehe,Huang, Kai,Zhang, Le,Ge, Binghui,Wang, Dong,Lang, Jialiang,Ma, Jingyuan,Wang, Da,Zhang, Shuai,Li, Qunyang,Zhang, Ruoyu,Hussain, Naveed,Lei, Ming,Liu, Li-Min,Wu, Hui
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supporting information
p. 3354 - 3359
(2018/02/21)
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- Structurally Ordered Intermetallic Cobalt Stannide Nanocrystals for High-Performance Electrocatalytic Overall Water-Splitting
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The synthesis of structurally ordered non-noble intermetallic cobalt stannide (CoSn2) nanocrystals and their utilization for high-performance electrocatalytic overall water-splitting is presented. The structurally and electronically beneficial properties of the tetragonal CoSn2 exhibit a considerably low overpotential for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) on fluorine-doped tin oxide (FTO) and Ni foam (NF). Loss of Sn from the crystal lattices and oxidation of Co under strongly alkaline conditions furnishes highly disordered amorphous active CoOx(H), the catalytically active structure for OER. The Co0 atoms in the CoSn2 act as active sites for HER and the presence of Sn provides efficient electrical conductivity. This intermetallic phase is a novel type of cost-effective and competitive bifunctional electrocatalysts and predestinated for overall water-splitting devices: A two-electrode electrolyzer with CoSn2 on NF delivers a cell voltage of merely 1.55 V at 10 mA cm?2 maintaining long-term stability.
- Menezes, Prashanth W.,Panda, Chakadola,Garai, Somenath,Walter, Carsten,Guiet, Amandine,Driess, Matthias
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supporting information
p. 15237 - 15242
(2018/10/26)
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- Robust cobalt oxide catalysts for controllable hydrogenation of carboxylic acids to alcohols
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The selective catalytic hydrogenation of carboxylic acids is an important process for alcohol production, while efficient heterogeneous catalyst systems are still being explored. Here, we report the selective hydrogenation of carboxylic acids using earth-abundant cobalt oxides through a reaction-controlled catalysis process. The further reaction of the alcohols is completely hindered by the presence of carboxylic acids in the reaction system. The partial reduction of cobalt oxides by hydrogen at designated temperatures can dramatically enhance the catalytic activity of pristine samples. A wide range of carboxylic acids with a variety of functional groups can be converted to the corresponding alcohols at a yield level applicable to large-scale production. Cobalt monoxide was established as the preferred active phase for the selective hydrogenation of carboxylic acids.
- Song, Song,Wang, Dong,Di, Lu,Wang, Chuanming,Dai, Weili,Wu, Guangjun,Guan, Naijia,Li, Landong
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p. 250 - 257
(2018/02/20)
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- Phenolic resin as a carbon source for the synthesis of monometallic Mo and bimetallic CoMo carbides via carbothermal reduction route
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It was the first time that phenolic resin (PR) was used as a carbon source for the synthesis of nanostructured monometallic Mo and bimetallic CoMo carbides via carbothermal reduction route. The results showed that phase-pure β-Mo2C can be formed under an Ar atmosphere at 900°C or a H2 atmosphere above 700°C. However, almost pure CoMo carbides (Co3Mo3C and Co6Mo6C) can be obtained only under a H2 atmosphere at a low temperature of 630°C for 24 and 48?h, respectively. The role of PR in the preparation process has been investigated and a detailed formation mechanism was proposed based on the experimental results.
- Gao, Liang,Shi, Yan,Yao, Zhiwei,Gao, Haifeng,Sun, Yue,liang, Feixue,Jiang, Baojiang
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p. 267 - 272
(2018/01/04)
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- Ammonolysis of Cobalt Molybdenum Oxides - In Situ XRD Study
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The reduction of cobalt molybdenum oxide under an ammonia atmosphere resulting in the formation of ternary interstitial nitride Co3Mo3N was studied. Intermediate phases were identified by an in situ powder X-ray diffraction using a reaction chamber. It was supplemented by a thermogravimetric analysis of the process. The presence of intermediate phases, CoMoO4, Co2Mo3O8, Mo2N, metallic cobalt, and Co2Mo3N, was observed. A synthesis route of Co3Mo3N by an ammonolysis method was proposed.
- Adamski, Pawe?,Moszyński, Dariusz,Komorowska, Agata,Nadziejko, Marlena,Sarnecki, Adam,Albrecht, Aleksander
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p. 9844 - 9850
(2018/08/28)
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- Improved structural stability, electron transport and defect formation in PrBaCo2–xAlxO6–δ
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The double perovskite-like solid solutions PrBaCo2–xAlxO6–δ are obtained via combustion of glycerol-nitrate organo-metallic precursors. The aluminum doping occurs favorable for mitigation of thermal expansion and stabilization of the tetragonal structure in a wide range of temperature changes. The variations of equilibrium oxygen content in PrBaCo1.9Al0.1O6–δ are measured with a coulometric titration technique, and analyzed in terms of defect chemistry. It is shown that aluminum incorporation is accompanied by formation of rigid AlO6 octahedra in the crystal structure and enhanced disproportionation of Co3+ cations. The developed defect model is successfully applied in order to explain the data for conductivity and thermopower. The structural stability, moderate thermal expansion and high conductivity represent an advantageous properties combination for the using of PrBaCo1.9Al0.1O6–δ cobaltite in various high-temperature solid state electrochemical devices.
- Marshenya,Politov,Suntsov, A. Yu,Leonidov,Petrova,Patrakeev,Kozhevnikov
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p. 1041 - 1047
(2018/07/29)
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- Unraveling the Chemical State of Cobalt in Co-Based Catalysts during Ethanol Steam Reforming: An in Situ Study by Near Ambient Pressure XPS and XANES
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The steam reforming of ethanol (ESR) has been studied by near ambient pressure XPS (NAP-XPS), extended X-ray absorption fine structure (EXAFS), and X-ray absorption near edge structure (XANES) under in situ conditions in the ALBA synchrotron facility at 200-580 °C and S/C = 3 over different cobalt-based catalysts that showed different catalytic performances: Co3[Si2O5]2(OH)2 (Co-talc), [Co2Mg4Al2(OH)16]CO3·4H2O (Co-hydrotalcite shortened to Co-HT) calcined at 550 °C, and Co3O4 (Co-spinel). Both Co-spinel and Co-talc yield to a greater or lesser degree metallic cobalt under ESR conditions. While Co-spinel shows a complete reduction to metallic cobalt under the conditions used for the XANES measurements, the more bulk-sensitive Co-talc sample exhibits only a partial reduction. On the other hand, under the ESR conditions used with the NAP-XPS, a more surface sensitive technique, the results indicate a higher reduction degree for the Co-talc sample in comparison to the Co-spinel sample. In contrast, the catalyst prepared from the Co-HT does not show metallic cobalt traces under the experimental conditions used with both techniques. On comparison of these three cobalt-based catalysts, the stable operation exhibited by Co-HT under ESR reaction conditions is justified by the absence of metallic cobalt formation under in situ conditions, which is identified as being responsible for the carbon deposition phenomenon that triggers the deactivation suffered by most cobalt-based catalysts during ESR.
- Huck-Iriart, Cristián,Soler, Lluís,Casanovas, Albert,Marini, Carlo,Prat, Jordi,Llorca, Jordi,Escudero, Carlos
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p. 9625 - 9636
(2018/10/02)
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- Low Temperature Formation of Ruddlesden–Popper-Type Layered La2CoO4±δ Perovskite Monitored via In Situ X-ray Powder Diffraction
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In this contribution low temperature formation of Ruddlesden–Popper (RP)-type layered La2CoO4±δ perovskite was optimized via in situ X-ray powder diffraction (XRPD). Starting from LaCoO3 a stoichiometric transformation to La2CoO4±δ and CoO can be achieved by controlled reduction with H2. The challenge of this reaction is the use of appropriate amounts of H2 in a defined temperature region. If the amount of H2 is too high, complete reduction of the perovskite occurs. If temperatures are not appropriate, intermediate phases seem to hinder the transformation to La2CoO4±δ or lead to a complete decomposition to simple oxides. Based on in situ XRPD experiments, the temperature window and required amount of H2 for the transformation of LaCoO3 to La2CoO4±δ were determined. Systematic experiments reveal that 650 °C is the optimal temperature for the complete transformation of LaCoO3 into La2CoO4±δ and CoO/Co0. The information was then transferred to realize bulk synthesis of La2CoO4±δ at 650 °C in a tube furnace without extended heat treatments at elevated temperatures.
- Ortatatl?, ?eyma,Ternieden, Jan,Weidenthaler, Claudia
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p. 5238 - 5245
(2019/01/04)
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- Phase equilibria, crystal structure at 1373 K and properties of complex oxides in the Nd–Co–Fe–O system
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Phase equilibria in the Nd–Co–Fe–O system were systematically studied at 1373 K in air. The homogeneity range and crystal structure of solid solution NdCo1–xFexO3 (0.0 ≤ x ≤ 1.0) have been studied by the X-ray powder diffraction method. The structural parameters of complex oxides have been refined by the full-profile Rietveld method. It was shown that all oxides reveal practically stoichiometric oxygen composition within the entire temperature range under investigation. The values of thermal expansion coefficients for the cobaltites NdCo1–xFexO3 (x = 0.3, 0.7) have been calculated within the wide temperature range in air. Chemical stability of NdCo1–xFexO3 (x = 0.3, 0.7) in respect to the solid electrolyte materials (Ce0.8Sm0.2O2–δ and La0.88Sr0.12Ga0.82Mg0.18O3-δ) was examined. Electrical conductivity of NdCo1–xFexO3 (x = 0.3, 0.7) was measured as a function of temperature within the range 300–1373 K in air. It was shown that substitution of cobalt for iron leads to the decrease of conductivity. The isothermal-isobaric cross-section of the phase diagram for the Nd–Co–Fe–O system at 1373 K in air has been presented.
- Aksenova,Elkalashy, Sh. I.,Urusova,Cherepanov
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p. 1090 - 1098
(2017/09/05)
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- Heterogeneous Cobalt-Catalyzed Direct N-Formylation of Isoquinolines with CO2 and H2
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Isoquinolines (IQs) are an abundant feedstock, and N-formyl-1,2,3,4-tetrahydroisoquinolines (FTHIQs) are valuable fine chemicals and key intermediates. Herein, we report for the first time the Co0/ZnCl2-catalyzed direct N-formylation of IQs by using CO2 with H2 to produce FTHIQs. It was discovered that the Co catalyst and ZnCl2 worked synergistically in catalyzing the N-formylation reactions, and moderate to high yields of the desired products could be obtained, depending on the nature of the substrates. The Co0 catalyst could be reused at least five times without a notable decrease in activity. A possible reaction mechanism is proposed on the basis of control experiments.
- He, Zhenhong,Liu, Hangyu,Liu, Huizhen,Qian, Qingli,Meng, Qinglei,Mei, Qingqing,Han, Buxing
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p. 1947 - 1952
(2017/06/13)
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- Catalytic performance of cobalt oxide-supported gold-palladium nanocatalysts for the removal of toluene and o-xylene
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Using the molten salt and polyvinyl alcohol-protected reduction method, we fabricated Co3O4 octahedron-supported Au-Pd (x(AuPdy)/Co3O4; x = (0.18, 0.47, and 0.96) wt%; y (Pd/Au molar ratio) = 1.85?1.97) nanocatalysts. The molten salt-derived Co3O4 sample possessed well-defined octahedral morphology, with an edge length of 300 nm. The Au-Pd nanoparticles, with sizes of 2.7?3.2 nm, were uniformly dispersed on the surface of Co3O4. The 0.96 (AuPd1.92)/Co3O4 sample showed the highest catalytic activity for toluene and o-xylene oxidation, and the temperature required for achieving 90% conversion of toluene and o-xylene was 180 and 187 °C, respectively, at a space velocity of 40000 mL/(g–h). The high catalytic performance of Co3O4 octahedron-supported Au-Pd nanocatalysts was associated with the interaction between Au-Pd nanoparticles and Co3O4 and high concentration of adsorbed oxygen species.
- Wang, Zhiwei,Liu, Yuxi,Yang, Tao,Deng, Jiguang,Xie, Shaohua,Dai, Hongxing
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p. 207 - 216
(2017/03/16)
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- Preparation process and mechanism of ultra-fine spherical cobalt powders by hydrogen reduction of calcium cobaltite
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For the improvement of the properties of cemented carbides, ultra-fine spherical cobalt powders as binder were prepared using calcium cobaltite. The effects of the ratio of CaO to CoO, the calcination temperature and the reduction temperature on particle
- Wu, Jiajing,Tang, Jiancheng,Wei, Xiaoxiao,Ye, Nan,Yu, Fangxin
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p. 1119 - 1123
(2017/08/21)
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- One-step synthesis of magnetically recyclable Co@BN core-shell nanocatalysts for catalytic reduction of nitroarenes
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We present a facile one-step synthesis of chemically stable and magnetic Co@BN core-shell nanoparticles. We found that Co@BN nanoparticles acted as excellent catalysts with high stability and magnetic recyclability for reduction of nitroarenes to aminoarenes under mild reaction conditions. The sample 13.6 wt% Co@BN showed the best catalytic activity for reduction of 4-nitrophenol (4-NP). In addition, a significant synergistic effect of the h-BN support was observed during the catalytic reaction by effectively adsorbing/concentrating and ionizing the reactant nitroaromatics. Moreover, the kinetics of the catalytic reaction were investigated at different reaction temperatures, 4-nitrophenol concentrations, sodium borohydride concentrations, metal loadings and catalyst amounts. The activation energy of the catalytic reduction of 4-nitrophenol for 13.6 wt% Co@BN was determined to be 102.93 kJ mol-1. This work provides a clear example of Co@BN core-shell nanoparticles as nanocatalysts.
- Du, Man,Liu, Qiuwen,Huang, Caijin,Qiu, Xiaoqing
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p. 35451 - 35459
(2017/07/25)
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- Highly efficient hydrolysis of ammonia borane by anion (-OH, F-, Cl-)-tuned interactions between reactant molecules and CoP nanoparticles
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The CoP nanoparticle catalyst had excellent catalytic activity and a short catalytic induction period in the presence of anions, and high sustainability in ammonia borane hydrolysis, with an initial turnover frequency of 72.2 mol(H2) mol(CoP)-1 min-1 at ambient temperature. This value is unprecedented for noble-metal-free catalytic systems.
- Fu, Zi-Cheng,Xu, Yong,Chan, Sharon Lai-Fung,Wang, Wei-Wei,Li, Fang,Liang, Fei,Chen, Yong,Lin, Zhe-Shuai,Fu, Wen-Fu,Che, Chi-Ming
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supporting information
p. 705 - 708
(2017/01/13)
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- B-cation partial substitution of double perovskite La2NiTiO6 by Co2 +: Effect on crystal structure, reduction behavior and catalytic activity
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La2NiTi0.9Co0.1O6 and La2Ni0.9Co0.1TiO6 perovskites were obtained by partial substitution of either Ti4 + or Ni2 + from double perovskite La2NiTiO6 by Co2 +. The Rietveld analysis demonstrated that all as-synthesized samples have orthorhombic symmetry and space group Pbnm. Quantitative phase analysis using Rietveld refinement of XRD profiles after temperature programmed reduction showed that the reduction of La2NiTiO6 was modified by partial substitution of either Ni2 + or Ti4 + by Co2 +, being more evident for the La2NiTi0.9Co0.1O6. The activity of all catalysts for steam reforming of methane was attributed to both the reduction degree of two-valence metals and the metal-support interaction.
- Tuza, Pablo V.,Souza, Mariana M.V.M.
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- Metal organic framework-derived Co3O4 microcubes and their catalytic applications in CO oxidation
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Metal-organic framework (MOFs)-derived metal oxides with diverse morphologies and microporous structures have shown potential applications in heterogeneous catalysis. In this study, two types of porous Co3O4 catalysts, Co3O4-MA and Co3O4-DMA (MA = methylamine and DMA = dimethylamine), were successfully synthesized via a one-step pyrolysis of Co-based metal-formate frameworks, [Amine][Co(HCOO)3] (Amine = methylamine, dimethylamine), in air. The obtained porous Co3O4 catalysts were systematically characterized by XRD, SEM, TEM, XPS, H2-TPR, and N2 adsorption-desorption analysis. The results show that the obtained porous Co3O4 catalysts are composed of nanoparticles and inherit the morphology from the precursor [Amine][Co(HCOO)3]. Co3O4-MA and Co3O4-DMA exhibit an excellent catalytic activity for CO oxidation, with both of them reaching a 100% CO conversion at 170 °C.
- Zhang, Chi,Zhang, Li,Xu, Guan-Cheng,Ma, Xin,Li, Ying-Hai,Zhang, Chu-Yang,Jia, Dian-Zeng
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p. 1631 - 1636
(2017/02/23)
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- Si/Co-CoSi2/reduced graphene oxide ternary nanocomposite anodes for Li-Ion batteries with enhanced capacity and cycling stability
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Silicon (Si) is a promising anode material for high-performance Li-ion batteries (LIBs), but it undergoes rapid capacity fading through severe volumetric expansion during Li insertion/extraction. Although alloying Si with various metal sources has been pursued to mitigate the structural deterioration, the resulting materials have shown the intrinsic problem of low electrical conductivity. To address this conflicting issue, here we describe a novel ternary nanocomposite of Si/Co-CoSi2/reduced graphene oxide (rGO) made using a facile process of mechanical mixing of Si nanoparticles, Co3O4 microparticles, and rGO nanosheets, followed by carbothermal reduction. Specifically, rGO, which has high electrical conductivity and structural integrity, could work as both a conductive matrix and a reducing agent in forming the Co-CoSi2 phase inside the Si domains during thermal treatment. The proposed ternary nanocomposites exhibited a noteworthy specific capacity of 952 mA h g?1 with 79.3% capacity retention after 80 cycles at a current density of 100 mA g?1. We attribute the improved electrochemical performance to the increased structural stability offered by the Co-CoSi2 phase and the interconnected conductive framework of the rGO nanosheets. Therefore, we expect our design process for Si/Co-CoSi2/rGO ternary nanocomposites to be applicable to other materials that can eventually be used as high-performance anodes for the next generation LIBs.
- Park, A Reum,Nam, Myeong Gyun,Kim, A-Young,Kim, Kwang Su,Sher Shah, Md. Selim Arif,Lee, Jun Young,Kim, Woo-Jae,Lee, Joong Kee,Yoo, Pil J.
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p. 1134 - 1142
(2017/07/22)
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- Structural Changes of Binary/Ternary Spinel Oxides During Ethanol Anaerobic Decomposition
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Several M-modified iron oxides of the spinel family have proven to be effective electron and O2? vectors for the production of hydrogen in the chemical-loop reforming of bio-alcohols. The present work is specifically focused on investigation of ethanol anaerobic decomposition over spinel oxides, which results in significant structural changes of the oxygen carrier material itself and corresponds to a first step of the chemical-loop reforming process. In particular, a series of binary/ternary M-modified ferrospinels were prepared by a co-precipitation method and tested in terms of both redox properties and intrinsic catalytic activity in addition to a complex ex situ study that encompasses the solid-state chemistry investigations of the fresh and reduced oxygen carrier materials. It was found that Co/Cu incorporation facilitates total/partial oxidation of ethanol, giving rise to high yields of H2, COx, and H2O; whereas Mn incorporation predominantly favored dehydrogenation and condensation reactions, leading to the formation of acetaldehyde and acetone. In addition, the incorporation of Mn contributed to significantly reduce the amount of coke formed; however, it caused a lower intrinsic reducibility, which was explained by the formation of a thermodynamically stable and hardly reducible layer of MnxFeyO solid solution.
- Vozniuk, Olena,Bazzo, Cristian,Albonetti, Stefania,Tanchoux, Nathalie,Bosselet, Fran?oise,Millet, Jean-Marc M.,Di Renzo, Francesco,Cavani, Fabrizio
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p. 2219 - 2230
(2017/06/27)
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- CoO microspheres and metallic Co evolved from hexagonal α-Co(OH)2 plates in a hydrothermal process for lithium storage and magnetic applications
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CoO microspheres and metallic Co could be successfully synthesized by simply reacting cobalt acetate with a mixture solvent of ethylene glycol and deionized water in a hydrothermal process for different times. As the reaction proceeded, α-Co(OH)2, CoO and metallic Co were produced. To understand the phase evolution processes from α-Co(OH)2 to CoO and then metallic Co, a range of time-dependent experiments were carried out, and the intermediate products obtained at different reaction times were investigated in detail. The investigation revealed that CoO microspheres were actually evolved from α-Co(OH)2 as a precursor. Just elongating the reaction time, CoO microspheres could be further reduced to metallic Co. With a pure ethylene glycol medium for the same reaction, only α-Co(OH)2 could be generated, indicating an important role of water. When the obtained CoO microspheres were used as anode materials for lithium-ion batteries, they delivered a specific capacity of 803 mA h g-1 at 0.1 A g-1 with a retention of 453 mA h g-1 after 70 cycles. Meanwhile, the magnetic properties of the obtained CoO microspheres and metallic Co were investigated, with the CoO microspheres showing an antiferromagnetic behavior and the metallic Co exhibiting ferromagnetic characteristics. This study suggested a novel method for synthesizing CoO with a uniform microsphere morphology and bulk metallic Co easily.
- Ma, Keyuan,Liu,Yuan,Liu,Wang, Jun,Xie,Cheng
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p. 595 - 604
(2018/01/03)
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- Reaction intermediate/product-induced segregation in cobalt-copper as the catalyst for hydrogen generation from the hydrolysis of sodium borohydride
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Cobalt is the most attractive catalyst for hydrogen generation from the hydrolysis of sodium borohydride, NaBH4, but its potential is further improved when it is combined with an inactive element like copper. Accordingly, several cobalt-copper catalysts (CoxCu1-x, with x as a mole ratio equal to 0, 0.1, 0.25, 0.5, 0.75, 0.9 or 1) were prepared. Under our conditions, Co0.9Cu0.1 shows the best performance, being able to complete H2 evolution in 0.9Cu0.1 is not as stable as expected; after the first cycle, the catalytic activity in terms of the H2 generation rate halves, and then remains quite constant for additional cycles (up to five under our conditions). XPS measurements show that the surface composition of Co0.9Cu0.1 is subject to changes during hydrolysis; the anti-segregation of copper concomitantly takes place with the segregation of cobalt. This is explained through the occurrence of borate-induced segregation, favored due to the well-known strong affinity of cobalt for borate species. In other words, the catalytic activity of cobalt can be improved through combination with copper but, under our conditions, it cannot be stabilized. This is evidenced and discussed in detail herein.
- Kahri,Flaud,Touati,Miele,Demirci
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p. 102498 - 102503
(2016/11/11)
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