Cobalt Nitrate Hexahydrate Research Articles

The effect of support morphology on CoOX/CeO2 catalysts for the reduction of NO by CO

When using nanocrystalline oxides as catalytic supports, different nanoshapes have different numbers of oxygen vacancy defects, surface energies, and surface terminations; these properties may affect the dispersion, oxidation state, and therefore catalytic activity of a second supported metal oxide. Here, cobalt oxide domains were synthesized on cerium oxide nanorods, nanocubes, and commercial nanopowder via incipient wetness impregnation of cobalt (II) nitrate hexahydrate at several surface coverages. The resulting materials were examined for their reducibility under CO and H2 and their reactivity in the catalytic reduction of NO by CO from 200 to 450 °C. Activity per total mass of catalyst is highest at intermediate loadings, while activity per Co atom is maximized at the lowest loadings, implicating highly dispersed Co-O-Ce sites as the active species. Across all Co loadings, catalysts with nanorod supports have higher activity than catalysts made with ceria nanoparticles or nanocubes. From X-ray absorption spectroscopy, it was found that the more-active nanorod supports are better able to maintain Co in a partially reduced state under reaction conditions after initial calcination. This stabilization appears to be further correlated with the high number of defects on the ceria nanorods observed via Raman spectroscopy, rather than with properties of the exposed crystal plane, as has been traditionally reported for these materials. These insights may lead to new generations of selective catalysts based on nanocrystal-supported oxides for emissions abatement and other important reactions.

Preparation of Mn-Co/Ceramic Honeycomb Catalyst and Its Performance on Catalytic Ozonation of Hydroquinone

In order to improve the activity and working life of metal catalysts in the heterogeneous catalytic ozonation of organic wastewater, four kinds of Mn-Co/ceramic honeycomb (CH) catalysts with different mass ratios of Mn and Co were prepared by coating method using cobalt nitrate hexahydrate [Co(NO3)2·6H2O] and manganese nitrate [Mn(NO3)2] as precursors, respectively, and CH as the carrier. The structure of the catalysts was analyzed via X-ray diffraction (XRD), N2 adsorption/desorption, field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The mechanical properties of the catalysts were studied. The reaction kinetics model of O3 alone and catalytic ozonation of the hydroquinone were established and catalytic ozonation performance of catalysts was investigated. The results showed that the crystal phase of Mn0Co1/CH belonged to CoAl2O4 and that the crystal phase of the Mn-Co/CH catalyst (Mn1Co1, Mn2Co1, and Mn3Co1) mainly belonged to Mn3O4 and CoO. In particular, the Mn1Co1/CH catalyst had a large specific surface area of 190 m2·g-1, high pore volume of 0.25 cm3·g-1, and pore size of 4.8 nm. The highest catalytic activity was obtained when Mn∶Co was 1∶1 (Mn1Co1/CH catalyst). The catalytic activity of the Mn1Co1/CH catalyst was the highest, and removal efficiencies of hydroquinone and COD were 78% and 54%, respectively, using Mn1Co1/CH catalytic ozonation. The Mn-Co/CH catalyst had a high compressive strength (15.89-16.94 MPa). The degradation efficiency of hydroquinone decreased significantly after the addition of tert-butanol, which indicated that·OH played an important role in the Mn1Co1/CH catalytic ozonation. The catalytic ozonation process fitted the first-order kinetic model. The apparent rate constant k for O3 alone was only 0.0306. Furthermore, the Mn1Co1/CH catalyst had the highest rate, with an apparent rate constant k of 0.0535 min-1. The Mn-Co/CH catalyst was easy to industrialize owing to its lower consumption, excellent catalytic characteristics, and long working life.

Hexamine Role on Pseudocapacitive Behaviour of Cobalt Oxide (Co₃O₄) Nanopowders.

Influence of hexamine surfactant concentration on crystallite size, structure, morphology, vibrational and optical properties of cobalt oxide nanopowders were explored. The cobalt oxide nanopowders were synthesized by employing a simple chemical reduction method using cobalt (II) nitrate hexahydrate (Co(NO3)2 ·6H2O) as precursor and sodium borohydride (NaBH4) as reducing agent along with hexamine as surfactant. XRD studies revealed the formation of face-centered cubic (Fd3m) crystalline structure of Co3O4 with an average crystallite size of 8-18 nm. The observed prominent characteristic Raman active modes of A1g, Eg, and F2g revealed the formation of Co3O4 nanopowders. The optical properties of Co3O4 nanopowders are examined by photoluminescence spectra. The obtained IR results confirmed the formation of Co3O4 nanopowders. The band observed 569 cm-1 is the characteristic of the Co3+ ions in the octahedral hole vibration and the 665 cm-1 band is attributable to the Co2+ ions in the tetrahedral hole vibration in the cubic lattice. The estimated specific capacitance of the obtained Co3O4 nanopowders was 291 F/g at 10 mV/s which could be a potential candidate for pseudo capacitive nature of the active materials.

Cobalt-Catalyzed C-H Nitration of Indoles by Employing a Removable Directing Group.

A mild and efficient C(sp2 )-H nitration of 3-substituted indoles, by using the economical and non-toxic cobalt nitrate hexahydrate [Co(NO3 )2 ⋅6 H2 O] as a catalyst and tert-butyl nitrite (TBN) as the nitro source, is reported. This approach provides a unique methodology involving a site-selective C-N bond formation for preparation of C-2 substituted nitro indoles. Utilization of the tBoc as the removable directing group enhances the synthetic utility of the method.

Preparation of Nano-Co3O4 by Direct Thermal Decomposition of Cobalt(II) Nitrate Hexahydrate for Electrochemical Water Oxidation

Background: Nano-Co3O4 has been used in various technological areas and applications such as electrochemical sensors and electrochemical water splitting. Even though many efforts have been expended to prepare nano-Co3O4, the development of novel methods to prepare Co3O4 using simple processes and at low cost remain a topic of interest. Besides, it could be economic and useful if the synthesized nanoparticle could be applied as efficient electrocatalyst upon its immobilization on a cheap base electrode material by very simple method for various practical applications including renewable energy. Method: We prepared nano-Co3O4 by a direct thermal decomposition of an inexpensive, simple and widely available cobalt inorganic precursor, such as Co(NO3)2·6H2O without any type of prereaction or processing. The nano-Co3O4 was immobilized on filter-paper-derived carbon electrode by drop-drying method for applying as electrode materials toward water electrooxidation. Results: The X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy analysis confirmed the formation of short nanorods of single-phase Co3O4 upon thermal decomposition of Co(NO3)2·6H2O at 520°C. The electrocatalytic properties of the nano- Co3O4 were evaluated after immobilizing it on a cheap carbon electrode derived from normal filter paper. The modified electrode showed good electrocatalytic properties toward water oxidation in an alkaline solution. Conclusion: In conclusion, we developed a very simple, straight-forward and economic method for preparation of nano-Co3O4 and immobilized it on very cheap carbon electrode for evaluating its electrocatalytic properties. Due to the high electrocatalytic properties, the prepared nano-Co3O4 could potentially play an important role in various practical fields.

Size and crystallinity control of two-dimensional porous cobalt oxalate thin sheets: tuning surface structure with enhanced performance for aqueous asymmetric supercapacitors.

With excellent layered structures, abundant pores and a high specific surface area, two-dimensional (2D) porous nanostructured materials have been demonstrated to show great potential in supercapacitors. At present, it is highly desirable but remains challenging to prepare different sizes and crystallinity of 2D porous thin sheets so as to further improve the performance of supercapacitors. Herein, 2D porous cobalt-oxalate (Co-OA) thin sheets with different sizes and crystallinity assembled by interconnected nanosheet array frameworks have been successfully synthesized, using cobalt nitrate hexahydrate as a cobalt source and oxalic acid dihydrate as a ligand, through a simple hydrothermal strategy at 220 °C for different reaction times. The as-prepared sample at 220 °C for 20 h, has a high area specific capacitance (1.631 F cm-2 at the current density of 1.2 mA cm-2), good rate capability (80.6% retention upon increasing the current density from 1.2 to 12 mA cm-2) and excellent cycling performance (1.5% attenuation at 6.0 mA cm-2 for 2000 cycles). In addition, one aqueous asymmetric supercapacitor (ASC) is constructed based on the sample synthesised at 220 °C for 20 h as positive electrodes and activated carbon (AC) as negative electrodes. This ASC effectively provides a maximum energy density of 17.675 Wh kg-1 at 900 W kg-1, still maintaining 8.25 Wh kg-1 at 9000 W kg-1, which demonstrates it may be a promising candidate in energy storage for supercapacitors. It is worth emphasizing that this strategy could be extended to fabricate other materials with different sizes and crystallinity.

Influencia del grupo alcoxi en la síntesis de óxido cobaltosico para la reducción de óxidos de nitrógeno

Presentamos una nueva metodología para la síntesis de óxido cobaltosico (Co3O4). Los materiales se prepararon haciendo reaccionar alcoholes de un carbono (C1) a cuatro carbonos (C4) de cadena lateral con sodio metálico y nitrato de cobalto hexahidrato, respectivamente a 600 ºC con flujo de helio. Como efecto de los hidrocarburos de cadena larga, C4 es el mejor precursor de Co3O4, debido a su área superficial más alta que la obtenida por precursores C1, C2, C3. Y todos los catalizadores alcanzaron la conversión de NO a 400 º C en el intervalo de 69.9 % a 97.5 %. Los materiales se caracterizaron por difracción de rayos X (XRD), tamaño promedio de los cristales, área superficial, espectroscopia de dispersión de energía (EDS) y microscopía electrónica de barrido (SEM).

Nitrogen-Doped Carbon Nanotubes Encapsulated Cobalt Nanoparticles Hybrids for Highly Efficient Catalysis of Oxygen Reduction Reaction

In this work, a nitrogen doped carbon nanotubes encapsulated cobalt nanoparticles (Co@N-CNTs) catalyst was prepared by assembling the precursors of melamine and cobalt nitrate hexahydrate, followed by gradient temperature carbonization in the presence of glucose as a reducing agent. The as prepared Co@N-CNTs composite exhibited electroactivity and long-term stability toward oxygen reduction reaction (ORR) in both alkaline and acidic solutions. It was found that the gradient temperature synthesis and reduction of the gels in the presence of glucose played an important role in the formation of a thin carbon shell on the Co nanoparticles, which protected it from being destroyed during the electrochemical procedures. These processes also facilitated to the ordered arrangement of nitrogen-carbon precursors and the formation of enriched pyridinic, pyrrolic and quaternary nitrogen functional groups that led to the highly activity of Co@N-CNTs. In addition, the catalyst also presented tolerance to methanol oxidation. This synthetic method and mechanism enlighten the future design of state-of-the-art nanostructured materials as an alternation for precious metal based catalysts for highly efficient ORR.

Cobalt Catalysts Preparation and Characterization over Alumina Support for Fischer Tropsch Synthesis

Abstract An investigation was done to develop and characterize the alumina supported cobalt catalyst for Fischer-Tropsch Synthesis to produce biodiesel from biomass with the aim to produce alumina-supported cobalt catalysts containing 7 to 19 wt.% cobalt content. By using incipient wetness impregnation of γ-Al2O3 supports with cobalt nitrate hexahydrate with ethanol and distilled water solutions; the 14 wt.% cobalt content in catalyst was achieved. Nitrogen adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray fluorescence (XRF), H2temperature programmed reduction (H2-TPR), temperature programmed desorption (TPD), temperature programmed oxidation (TPO) and carbon monoxide chemisorption were used for the characterization of the catalysts to attain an appropriate cobalt catalyst. In order to investigate the effect of the impregnation on the crystalline size, surface area and cobalt content, three different impregnation methods with various durations were investigated. In addition, increasing the impregnation duration increased the cobalt content and its dispersion. Based on results, positive effect of the alumina support and impregnation duration on the crystallite size, surface area, and pore diameter, reducibility of the catalyst and cobalt dispersion were investigated. Thus, cobalt catalyst for using in fixed bed reactor to produce biodiesel from biomass through Fischer-Tropsch Synthesis was prepared and characterized.

Partition of metallic cations between aqueous solutions and mixed crystals of hydrated cobalt and nickel nitrates: Modelling of the influence of temperature and composition

Abstract A systematic study of the solid-liquid equilibria of the H2O-Co(NO3)2-Ni(NO3)2 ternary system enabled to define the liquidus and the solidus curves of the isotherms at 287.15 K and 313.5 K. Two widespread solid solutions, Co(1-σ)Niσ(NO3)2.6H2O and Ni(1-ω)Coω(NO3)2.6H2O, were observed. They were formed by the substitution of Co2+ cations by Ni2+ cations in the monoclinic structure of the cobalt nitrate hexahydrate and the substitution of Ni2+ by Co2+ in the triclinic structure of the nickel nitrate hexahydrate. Two series of tie-lines for each crystallographic structure of these hexahydrates were obtained. The analyses of these tie-lines and those of the previous studies at 258.15 K and 303.15 K enabled a thermodynamic modelling of the solid-liquid equilibria within a temperature range from 258.15 K to 313.15 K. The simple equation system obtained allows to calculate the accurate composition of the mother solution, at a defined temperature, to reach the appropriate cationic ratio in the crystallised solid solution.

Structural elucidation, EPR and magnetic property of a Co(III) complex salt incorporating 4,4′-bipyridine and 5-sulfoisophthalate

The cobalt(III) derivative [Co3(sip)4(bipy)2(H2O)10][Co(bipy)2(H2O)4]3(sip)2·20H2O (1) has been hydro(solvo) thermally synthesized by combining sodium 5-sulfoisophthalate (sipH2Na) as organic linker, divalent cobalt nitrate hexahydrate as metal salt and the flexible N-donor ancillary ligand bipy (4,4′-bipyridine). Compound 1 is an ionic solid consisting of both cobalt containing cations and anions and also in addition 5-sulfoisophthalate anions. Cobalt containing cations in the crystal structure are mononuclear complex while cobalt containing anion is a discrete trinuclear species. The π–π interaction present in 1 results in chain supramolecular structure. The encapsulation of the cobalt compound displays a moderate luminescent property. On temperature dependent magnetic study, it is revealed that the corresponding effective magnetic moment is 5.27 B.M. at 300 K, which suggests isolated Co(III) species with S = 2 (theoretical value is 4.90 B M.) and thus 1 shows a rare paramagnetic behavior.

Synthesis of Nanocrystalline Cobalt Ferrite by the Sonochemical Method in Highly Basic Aqueous Solution

This study reported the preparation of nanocrystalline CoFe2O4 in single step by the sonochemical method in highly basic aqueous solution without requiring of high temperature calcination process. To prepare nanocrystalline CoFe2O4, the mixed solution of the required molar ratio of cobalt nitrate hexahydrate (Co (NO3).6H2O) and ferric nitrate nonahydrate (Fe (NO3).9H2O) was precipitated in high concentration of sodium hydroxide medium solution (NaOH) under high intensity ultrasonic irradiation (20 kHz, 150 W/cm2). The effect of NaOH concentration (5, 10, 15 and 20 M) on phase formation, microstructure and magnetic property of CoFe2O4 was investigated. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA) results showed that the as-prepared powders were single phase CoFe2O4 with cubic spinel structure. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) study showed that nanocrystalline CoFe2O4 had monosized distorted spherical morphology and an agglomeration of the nanocrystalline CoFe2O4 into nanoparticles was observed when increasing the NaOH concentration. The nanocrystalline CoFe2O4 exhibited superparamagnetic property and the saturation magnetization (Ms) obtained from vibrating sample magnetometry (VSM) was found to correlate with the crystallite size and varied from 39-45 emu/g.

家庭用電子レンジを用いた無機固体水和物の脱水反応の再検討 : 硫酸銅(II)五水和物と硝酸コバルト(II)六水和物を例として

家庭用電子レンジを用いた無機固体水和物の脱水反応の再検討 : 硫酸銅(II)五水和物と硝酸コバルト(II)六水和物を例として

Hydrothermal synthesis of Co3O4 nanosheets and its application in photoelectrochemical water splitting

ABSTRACTIn this study, Co3O4 nanosheets were synthesized through hydrothermal method using cobalt nitrate hexahydrate. X-ray diffraction, diffuse reflectance spectra, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and field emission scanning electron microscopy were applied to investigate the properties of as-synthesized samples. Ultimately, the electrochemical and photoelectrochemical properties were evaluated by Mott–Schottky analysis and measuring photoconversion efficiency of Co3O4 nanosheets. The results indicated that Co3O4 nanosheets exhibited a maximum efficiency of 0.92% for water electrolysis under simulated 1.5 global sunlight air mass, which further suggests the excellent potential of Co3O4 nanosheets for application in hydrogen generation through photocatalytic water splitting.

Green and eco-friendly synthesis of cobalt-oxide nanoparticle: Characterization and photo-catalytic activity

Cobalt-oxide nanoparticles (NPs) were fabricated using Punica granatum peel extract from cobalt nitrate hexahydrate at low temperature. The synthesized cobalt-oxide NPs were characterized using X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray, atomic force microscopy, fourier transform infrared spectroscopy and UV-visible techniques. The cobalt-oxide NPs were in highly uniform shape and size was in the size of 40–80nm. Photo-catalytic activity (PCA) of the synthesized NPs was evaluated by degrading Remazol Brilliant Orange 3R (RBO 3R) dye and a degradation of 78.45% was achieved (dye conc. 150mg/L) using 0.5g cobalt-oxide NPs for 50min irradiation time. In view of eco-benign and cost-effective nature, the present investigation revealed that P. granatum could be used for the synthesis of cobalt-oxide NPs for photo-catalytic applications.

Efficient Synthesis of 5-Carboxanilide-Dihydropyrimidinones Using Cobalt(II) Nitrate Hexahydrate

5-Carboxanilide-dihydropyrimidinone derivatives were synthesized in good yield in a three-component and efficient process by the condensation reaction of acetoacetanilide, aldehyde and urea/thiourea in the presence of cobalt(II) nitrate hexahydrate as catalyst in ethanol at ambient condition.

Co3O4-graphene nanoflowers as anode for advanced lithium ion batteries with enhanced rate capability

Abstract The practical application of Co 3 O 4 base anode material is severely limited by its extremely low electrical conductivity and large specific volume changes during lithium ion insertion/extraction. Herein, an effective strategy is being implemented to mitigate the capacity fading of Co 3 O 4 at high-rate by embedding Co 3 O 4 nanomaterial under the reduced graphene oxide (CGF). The CGF composite has been synthesized through a two-step process, involving a hydrothermal reaction of cobalt nitrate hexahydrate and CTAB in the presence of graphene oxide (GO) and a subsequent calcination. When tested as the anode in lithium ion batteries (LIBs), the CGF composite exhibits an obvious enhancement in electrochemical performance, especially in rate capability. Under current density of 1.0 A g -1 , the CGF composite could deliver reversible capacity as high as 1120.8 mAh g −1 after 250 cycles. The superior performance of CGF composite may be ascribed to the unique hybrid microstructure, which can alleviate the stresses caused by volume variations, reduce charge transfer resistance, improve the accessibility of anode to electrolyte and increase the tapping density. The results clearly demonstrate that this unique electrode architecture is ideally suited for LIBs.

Simple route for preparation cobalt tungstate nanoparticles with different amino acids and its photocatalyst application

Nanoparticles sphere-like cobalt tungstate (CoWO4) have been successfully synthesized via the co-precipitation method process by using cobalt (II) nitrate hexahydrate and Na2WO4⋅2H2O. Capping agents are frequently used in colloidal synthesis to inhibit nanoparticle overgrowth and aggregation as well as to control the structural characteristics of the resulted nanoparticles in a precise manner; therefore, valine, glycine, and alanine were applied as capping agents. Besides, the effect of valine, glycine, and alanine on the morphology and size of final products were investigated by SEM analysis. According to the vibrating sample magnetometer, cobalt tungstate nanoparticles indicated a paramagnetic behavior at room temperature. The morphology and particle size of products were investigated by SEM images, XRD patterns, UV–Vis and EDS spectroscopy. The photocatalytic characteristics of as-obtained nanocrystalline cobalt tungstate were also examined by degradation of methyl orange (MeO) dye as water contaminant.

Synthesis of Co3O4 macrocubes catalyst using novel chitosan/urea template for hydrogen generation from sodium borohydride

Co3O4 catalyst with porous macrocubes structure were one pot formulated by hydrothermal treatment of chitosan/urea/Co(NO3)2·6H2O mixtures at 180 °C for 8 h and then calcined at different temperatures for 4 h. Chitosan and urea are both compounds containing amino group, which made them different from the previous supporting materials. In this study, chitosan was the major template in the solution and determined the shape of the Co3O4 catalyst while urea played a major support to cobalt (II) nitrate hexahydrate during crystal growth of the catalyst. The prepared materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), UV–vis Absorption Spectrum and BET technique. A remarkably high hydrogen generation rate of 1497.55 mlH2 min−1 gcat−1 was obtained from the hydrolysis of 2 wt % NaBH4 solution with 0.02 g catalyst at 25 °C. The catalytic activity of the as-prepared sample was examined for hydrolysis reaction of sodium borohydride (NaBH4) at different temperatures, catalyst amount and NaBH4 concentration. The results reveal that the average crystallite size, macrocubes thickness, surface properties and catalytic activity of Co3O4 macrocubes could be controlled by varying the mass ratio of chitosan/urea to cobalt concentration.

Investigating the effect of cobalt loading on thermal conductivity and hydrogen storage capacity of hollow glass microspheres (HGMs)

In present study, cobalt loaded hollow glass microspheres (HGMs) were fabricated from amber colored glass powder blended with cobalt nitrate hexahydrate salt, by flame spheroidisation method. The morphology of the samples was observed using field emission-scanning electron microscope (FE-SEM), environmental SEM (ESEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy and X-ray diffraction (XRD) techniques. The results showed that HGMs with surface coating of cobalt oxide can be successfully synthesized using this single step process. Effect of cobalt loading percentage (0-10%) in the glass feed on the formation of cobalt loaded HGMs were studied. A continuous thin coating of cobalt oxide on the HGMs surface was obtained when the cobalt content in the feed glass powder was up to 2%. Further increase of the cobalt in the feed glass led to uneven coating on the surface of HGMs. A clear cut diffraction pattern for crystalline CoO was observed at the thick patches observed on the HGMs samples with 10% loading of cobalt. The thermal conductivity of HGMs increased when the cobalt loading increased from 0 to 10 wt.%. The hydrogen storage experiments done on all the prepared samples at 200 °C and 10-bar pressure showed that the hydrogen storage capacity increased when the Co percentage in the sample increased from 0 to 2%. The percentage of cobalt was increased beyond 2 wt.% showed a decline in the hydrogen storage capacity.