Xn:Harmful;
7440-48-4Relevant articles and documents
Synthesis, characterisation and catalytic performance of nanocrystalline Co3O4 for gas-phase chlorinated VOC abatement
De Rivas, Beatriz,Lopez-Fonseca, Ruben,Jimenez-Gonzalez, Cristina,Gutierrez-Ortiz, Jose I.
, p. 88 - 97 (2011)
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.
Thermogravimetric study of the kinetics of Co3O4 reduction by hydrogen
Tomi?-Tucakovi?, Biljana,Majstorovi?, Divna,Jeli?, Dijana,Mentus, Slavko
, p. 15 - 24 (2012)
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
Co nanoparticles embedded in a 3D CoO matrix for electrocatalytic hydrogen evolution
Liu, Xiangye,Dong, Chenlong,Dong, Wujie,Wang, Xin,Yuan, Xiaotao,Huang, Fuqiang
, p. 38515 - 38520 (2016)
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.
Electrochemical deposition of co under the influence of high magnetic fields
Uhlemann,Krause,Chopart,Gebert
, p. C817-C826 (2005)
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.
Highly crystalline anisotropic superstructures via magnetic field induced nanoparticle assembly
Park, Jong-Il,Jun, Young-Wook,Choi, Jin-Sil,Cheon, Jinwoo
, p. 5001 - 5003 (2007)
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.
Synthesis, characterization, and tunable optical properties of hollow gold nanospheres
Schwartzberg, Adam M.,Olson, Tammy Y.,Talley, Chad E.,Zhang, Jin Z.
, p. 19935 - 19944 (2006)
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
Effect of temperature on Co electrodeposition in the presence of boric acid
Santos,Matos,Trivinho-Strixino,Pereira
, p. 644 - 649 (2007)
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.
Paramagnetic alkyl, hydride, and alkene complexes of the Tpt-Bu,MeCo moiety
Jewson, Jennifer D.,Liable-Sands, Louise M.,Yap, Glenn P. A.,Rheingold, Arnold L.,Theopold, Klaus H.
, p. 300 - 305 (1999)
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
Preparation and Properties of Cobalt(II) Hydroxide-(Sodium Fluoride Tetrasilicic Mica) Intercalation Complexes and of Highly Dispersed Cobalt on Mica
Ohtsuka, Kunio,Koga, Johji,Suda, Mitsuru,Ono, Mikiya,Takahashi, Minoru
, p. 2843 - 2848 (1987)
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.
Effects of heat treatments on the ductility of cobalt electrodeposits
Dille,Charlier,Winand
, p. 2771 - 2779 (1998)
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.
