Cobalt Acetate Research Articles

PANI-g-C3N4 grafted on cobalt acetate as an efficient precursor for synthesis of N-doped carbon contains cobalt composite: A versatile catalyst for reduction of nitro compounds

In this study, a novel nano catalyst consisted of Co oxide particles incorporated in N-doped porous carbon, named Co3O4@N-C-600, was synthesized in the one-step pyrolysis of polyaniline-graphitic carbon nitride composite grafted cobalt acetate at 600 °C. The resulting Co3O4@N-C-600 catalyst was characterized using different identification methods. In addition, specific surface area and the size of the porous carbon cavities were measured using Brunauer-Emmett-Teller (BET) analyzer. The catalytic performance of this novel nano-catalyst was examined for reduction of aromatic and aliphatic nitro-compounds using water as green solvent at 75 °C. Also the as prepared carbon catalyst resulted corresponding amine compounds in high yields and short reaction times. After the end of the reaction, the nano catalyst was easily separated using centrifuge and the recycle studies showed that it reused in five continuous runs in the model reaction without appreciable loss of its catalytic activity.

Co3O4-doped two-dimensional carbon nanosheet as an electrode material for high-performance asymmetric supercapacitors

Transition metal oxide-doped two-dimensional (2D) carbon nanosheets are attractive for the preparation of supercapacitors. However, the synthesis of the composites involves complex steps and multiple reagents. Herein, we demonstrate a simple and effective method for the fabrication of 2D carbon nanosheets with highly dispersed cobalt oxide nanoparticles on their surface. Gelatin and melamine were used as the carbon sources, while cobalt acetate (Co(CH3COO)2) was used as the source of Co3O4. After the hydrothermal reaction and carbonization, Co3O4 was well anchored on the surface of the 2D carbon nanosheets. Interestingly, the morphology could be tuned by varying the amount of cobalt acetate added to the gelatin and melamine co-polymer. A 2D carbon nanosheet formed when more than 1 g of cobalt acetate was used along with 1 g of gelatin and 0.3 g of melamine has excellent electrochemical properties. When used in an asymmetric supercapacitor, high energy density, and long stability could be achieved, which is promising for the development of high-performance supercapacitors.

Adsorption and Photo-catalytic Properties of Congo Red by Cobalt Doped Porous ZnO Prepared Through Hydrothermal Method

ZnO and cobalt doped ZnO were prepared by hydrothermal method with zinc acetate dihydrate, cobalt acetate tetrahydrate and urea as raw materials and sodium citrate as surface modifier. Congo red (CR) was used as the pollutant model for adsorption and photo-catalytic experiments. Under the same conditions, the adsorption effect of cobalt doped ZnO with different urea content on CR was investigated, and the optimum urea content was determined. Under the same conditions, the adsorption and photocatalytic properties of cobalt doped ZnO prepared with the best urea content at different annealing temperatures were studied. According to the analysis of experimental data, the adsorption effect of Co doped ZnO with urea content of 8mmol and annealing temperature of 300℃ is the best, and the photocatalytic effect is also the best under the same conditions.

Self-template formation of porous Co3O4 hollow nanoprisms for non-enzymatic glucose sensing in human serum.

A novel type of porous Co3O4 hollow nanoprism (HNP) was successfully prepared using tetragonal cobalt acetate hydroxide [Co5(OH)2(OAc)8·2H2O] as precursor by a facile solvothermal process and a subsequent calcination treatment. The morphology and structure of the Co3O4 HNPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD) and N2 adsorption–desorption measurements. An enzyme-free glucose sensor was constructed based on the Co3O4 HNPs, and the electrochemical performance was tested by cyclic voltammetry (CV) and chronoamperometry. The as-prepared sensor exhibited a good electrocatalytic activity for glucose oxidation at the applied potential of 0.6 V in alkaline solution, with a high sensitivity of 19.83 μA mM−1 cm−2 and a high upper limit of 30 mM, which provide the potential for direct determination of blood glucose without any dilution pretreatment. The Co3O4 HNPs had a porous and tubular structure with a large amount of accessible active sites, which enhanced the mass diffusion and accelerated the electron transfer. Moreover, the sensor also demonstrated a desirable stability, selectivity and reproducibility, and could verify the non-enzymatic analysis of glucose in real samples.

Sub-ppm H2S sensing by tubular ZnO-Co3O4 nanofibers

Tubular ZnO – Co3O4 nanofibers were co-electrospun from polymer solution containing zinc and cobalt acetates. Phase composition, cobalt electronic state and element distribution in the fibers were investigated by XRD, SEM, HRTEM, HAADF-STEM with EDX mapping, and XPS. Bare ZnO has high selective sensitivity to NO and NO2, while ZnO-Co3O4 composites demonstrate selective sensitivity to H2S in dry and humid air. This effect is discussed in terms of transformation of cobalt oxides into cobalt sulfides and change in the acidity of ZnO oxide surface upon cobalt doping. Reduction in response and recovery time is attributed to the formation of a tubular structure facilitating gas transport through the sensitive layer.

Structural, textural and electrochemical relationships in HF etched cobalt-silicon micro/mesoporous oxycarbides

Cobalt-silicon oxycarbide materials (Co–SiOC) have been produced through the polymer-derived ceramic route by incorporating Cobalt acetate in different proportions. HF etching of the obtained materials leads to obtaining C-rich Co–SiOC materials where the constituent phases present different characteristics. The SiO2 units that were the most vulnerable to the chemical attack were the most tensioned ones which are connected at the edges of the graphitic planes. The carbonaceous nanostructures in the HF-etched materials present a different ordering degree which is related with the microstructural characteristics of the pyrolyzed precursors. In addition, the electrochemical performance turns out to be dependent not solely on the Co content but also to the graphitization degree of the carbonaceous phase.

New thiosemicarbazone Schiff base ligands: Synthesis, characterization, catecholase study and hemolytic activity

Two novel thiosemicarbazones ligands have been synthesized and characterized by FT-IR, ESI-MS, 1H NMR, and also by single-crystal X-ray diffraction for L1. The crystal structure shows that L1 molecules are planar and are connected via N-H----S and O-H----S interactions. The catecholase activity of is situ copper and cobalt complexes of this ligands has been investigated against 3,5-di-tert-butylcatechol. The progress of the oxidation reactions was closely monitored over time following the strong peak of 3,5-DTBC using UV–Vis. Oxidation rates were determined from the initial slope of absorbance vs. time plots, then analyzed by Michaelis-Menten equations. Catechol oxidation reactions were realized using different concentrations of copper and cobalt acetate and ligands (L/Cu: 1/1, 1/2, 2/1). The results show that all complexes were able to catalyze the oxidation of 3,5-DTBC. Acetate complexes have the highest activity. CuL1 and CoL1 complexes act as a catalyst and inhibitor. While copper and cobalt complexes obtained from ligand L2 illustrate concentration-independent oxidation activation. The hemolysis study performed by L1 increases as a function of its concentration. However, ligand L2 has no hemolytic effect.

Promotional Effect of Preparation Methods on Catalytic Reduction of NO by CO over CoCeOx Catalysts

In this study, a series of CoCeOx catalysts were prepared by template, solid-state grinding with cobalt sulfate or cobalt acetate as the precursor and the oil bath method for catalytic reduction of...

PVA membranes with a surface layer of magnetically-patterned cobalt-containing multiwall carbon nanotubes

Composite membranes 15 to 40 µm thick are prepared by mixing aqueous solutions of polyvinyl alcohol (PVA) with dimethyl sulfoxide solutions of multiwall carbon nanotubes (MWNT) at various concentrations. MWNT are synthesized with a microwave-assisted technique from graphite and cobalt acetate powders and exhibit residual Co nanoparticles of less than 100 nm inside MWNTs and at MWNT tip terminations (MWNT-Co). Due to attached Co nanoparticles, MWNT-Co can be pulled by an external magnetic field gradient which induces segregation and clustering in the composite with PVA producing self-organized stripe (or laning) MWNT-Co density pattern along the direction of an applied magnetic field as low as 2.5 mT. These patterns occur within concentrations in the 0.15 to 0.30 wt% range of MWNT-Co in the PVA matrix. Membranes with preserved magnetically-induced MWNT-Co patterns are obtained by curing the solutions under an applied magnetic field. For all assayed concentrations and due to magnetophoretic diffusive segregation effects, the MWNT-Co emerge in the composite membranes as an upper surface layer of MWNT-Co covered only by a thin skin of PVA. This particular arrangement of MWNT-Co makes these membranes good candidates as active elements in devices with applications in many fields. We study structural, optical, and electrical properties of both disordered and magnetically-patterned MWNT-Co/PVA membranes.

Catalytic promiscuity of two novel cobalt(III) complexes derived from redox non-innocent Schiff base ligands: Unraveling the role of methyl groups in the ligand backbone on catalytic efficiency

Two Schiff base ligands namely (E)-4-bromo-2-(((1-hydroxy-2-methylpropan-2-yl)imino)methyl)-6-methoxyphenol(H2L1) and (E)-4-bromo-2-(((2-hydroxyethyl)imino)methyl)-6-methoxyphenol (H2L2) were designed and synthesized by varying methyl groups to prepare cobalt(III) complexes [Co(HL1)(L1)](1) and [Co(HL2)(L2)](2) using cobalt(II) acetate as metal precursor. Complexes 1 and 2 were characterized by usual physicochemical techniques and solid state structure of complex 2 was determined by X-Ray crystal structure analysis. The electrospray ionization-mass spectrometry (ESI-MS) analysis proved that complexes 1 and 2 were present as mononuclear entity in solution phase. The newly synthesized complexes were used to exploit their catalytic promiscuity. Catecholase like activity of both complexes 1 and 2 was carried out in N, N-dimethylformamide (DMF) medium using 3,5-di-tert-butyl catechol (3,5-DTBC) as model substrate (substrate : complex = 100:1) and the rate of the activity followed the trend, 1 > 2. Phosphatase like activity was studied by using disodium salt of 4-nitrophenylphosphate (4-NPP) as model substrate in DMF-H2O (substrate: complex = 20:1) mixture, indicating that the complexes were enormously accelerated the rate of phosphate monoester hydrolysis and the rate of the activity followed the reverse trend of catecholase like activity i.e.2 > 1. The role of methyl groups in the ligand backbone of H2L1 is supposed to be the determining factor to differentiate the catalytic efficiency of complexes 1 and 2 and the experimental observation has been supported by DFT calculations.

Simple synthesis of hierarchical porous carbon with developed graphene domains for high performance supercapacitors

Hierarchical porous carbons with localized graphene structure, high specific surface area and large pore volume are simply synthesized by the means of short-time pyrolysis at moderate temperatures and acid-washing. Citric acid and cobalt acetate were used as carbon source and template precursor, the effect of mass ratio of citric acid/cobalt acetate on the microstructures of the hierarchical porous carbon, including morphology, crystal structure, porosity, specific surface area and surface chemistry, have been investigated. The resultant hierarchical porous carbons possess high specific surface area of 1411 m2/g, a large pore volume of 2.34 cm3/g. Both three-electrode and two-electrode test were conducted to evaluate capacitive performance of the hierarchical porous carbon. The test of three-electrode system with 6 M KOH aqueous solution as electrolyte, the hierarchical porous carbon shows superior specific capacitance up to 239 F/g at 0.1 A/g. In 1 M Na2SO4 aqueous electrolyte. Moreover, the hierarchical porous carbon based two-electrode supercapacitors presents gravimetric energy density of 11.6 Wh/kg and power density of 250 W/kg. This work developed a facile way for high surface areas and large pore volume electrode materials for energy storage devices.

Microstructure and Optical Bandgap of Cobalt Selenide Nanofilms

The purpose of this research is to explore the properties of CoSe nanostructured thin films on glass substrates prepared by a chemical solution deposition method. Special attention is given to study the effects of precursor concentrations (Cobalt(II) acetate, Ammonia and Sodium Selenosulphite), fixing the Co:Se concentration ratio, on the grainy structure and optical properties of the resulting thin films. The structural, chemical composition and morphological characteristics were investigated by X-ray diffraction (XRD), energy dispersive X-ray microanalysis (EDX) and scanning electron microscopy (SEM), respectively. The optical properties were determined by UV–visible spectroscopy determining the optical band gap energy (Eg). According to these results, the average particle diameter was decreased from 119 to 42 nm as the precursor salt concentration was decreased from 0.3 to 0.1 M, being the bigger nanoparticles more spherical. With the reduction of the particle size, a blue shift in the absorption peaks of the UV–visible spectra and an increment of their optical band gap energy (from 1.8 to 3.6 eV) occurred due to confinement effects.

Identifying properties of low-loaded CoOX/CeO2 via X-ray absorption spectroscopy for NO reduction by CO

The speciation and catalytic activity of ceria supported transition metal oxides synthesized via incipient wetness impregnation are highly dependent on synthesis parameters such as the choice of metal precursor and the concentration of defects such as oxygen vacancies in the support. Here, cobalt oxide domains were synthesized on cerium oxide nanorods and commercial nanopowder via incipient wetness impregnation of cobalt (II) nitrate hexahydrate, cobalt (II) acetate, cobalt (III) acetylacetonate, and disodium cobalt (II) ethylenediaminetetraacetic acid at surface densities below monolayer coverage. Their reactivity was tested in the catalytic reduction of NO by CO. The steady-state deNOx activity at 250 °C of the catalyst prepared with cobalt (III) acetylacetonate and ceria nanorods was nearly three times greater than that of the control catalyst. From X-ray absorption spectroscopy it was seen that as-deposited cobalt precursors on a nanorod support were more highly coordinated than were cobalt precursors on comparable commercial ceria nanoparticles, possibly indicating anchoring at defects on the nanorods. A relationship was found between catalyst activity and the cobalt oxidation state of the fully calcined catalysts that suggests that deNOx activity is separately dependent on the cobalt oxide distribution and the presence of defects in the support. Overall, here it is shown that the two critical synthesis parameters of ligand choice and defected supports combine additively to improve reactivity of the supported cobalt oxide.

A One‐Pot Method to Synthesize a Co‐Based Graphene‐Like Structure Doped Carbon Material for the Oxygen Reduction Reaction

AbstractThe performance of the oxygen reduction reaction (ORR) is a core issue in of fuel cells. ORR is a slow kinetic process; platinum normally is used to accelerate the reaction. This is a bottleneck for further development of fuel cells. Transition metal and heteroatom co‐doped carbon materials have great potential in ORR catalysis. However, one‐step synthesis of high activity and stability transition metal and heteroatom co‐doped electrocatalysts is still a challenge. In this work, nitrogen, fluorine, and cobalt co‐doped carbon catalyst, MPCo‐950‐5, is prepared from melamine, polytetrafluoroethylene, and cobalt acetate by a one‐step method. MPCo‐950‐5 with a graphene‐like structure and its specific surface area is 642 m2 g−1. The ORR half‐wave potential of MPCo‐950‐5 is positively shifted by 35 mV compared to that of commercial Pt/C. In addition, MPCo‐950‐5 also shows excellent stability and methanol tolerance. This work serves as a simple and feasible method for preparing high ORR active transition metal and heteroatom co‐doped carbon materials.

Dinuclear cobalt and nickel complexes of a mercaptoacetic acid substituted 1,2,4-triazole ligand: syntheses, structures and urease inhibitory studies.

Because of its versatile coordination modes and strong coordination ability, the mercaptoacetic acid substituted 1,2,4-triazole 2-{[5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetic acid (H2L) was synthesized and characterized. Treatment of H2L with cobalt and nickel acetate afforded the dinuclear complexes {μ-3-[(carboxylatomethyl)sulfanyl]-5-(pyridin-2-yl)-4H-1,2,4-triazol-4-ido-κ2N1,N5:N2,O}bis[aqua(methanol-κO)cobalt(II)] methanol disolvate, [Co2(C9H6N4O2S)2(CH3OH)2(H2O)2]·2CH3OH (1), and {μ-3-[(carboxylatomethyl)sulfanyl]-5-(pyridin-2-yl)-4H-1,2,4-triazol-4-ido-κ2N1,N5:N2,O}bis[diaquanickel(II)] methanol disolvate dihydrate, [Ni2(C9H6N4O2S)2(H2O)4]·2CH3OH·2H2O (2), respectively. Complex 1 crystallized in the monoclinic space group P21/c, while 2 crystallized in the tetragonal space group I41/a. Single-crystal X-ray diffraction studies revealed that H2L is doubly deprotonated and acts as a tetradentate bridging ligand in complexes 1 and 2. For both of the obtained complexes, extensive hydrogen-bond interactions contribute to the formation of their three-dimensional supermolecular structures. Hirshfeld surface analysis was used to illustrate the intermolecular interactions. Additionally, the urease inhibitory activities of 1, 2 and H2L were investigated against jack bean urease, where the two complexes revealed strong urease inhibition activities.

Investigation of the inhibition efficiencies of novel synthesized cobalt complexes of 1,3,4-thiadiazolethiosemicarbazone derivatives for the acidic corrosion of carbon steel

Two novel thiosemicarbazone linked with 1,3,4-thiadiazole ligands were synthesized through the condensation reaction of the acetyl group at position 5 of 1,3,4-thiadiazole derivatives with thiosemicarbazide in acidic ethanol solution in addition to their Co(II)-complexes. The divalent cobalt complexes of both ligands have been synthesized through the reaction of cobalt acetate with each ligand leading to the formation of the two complexes [(LH)Co(OAc)]0.5H2O and [(LCl)Co(OAc) (H2O)2]; where LH and LCl are 1,3,4-thiadiazolethiosemicarbazone ligands. The two complexes have been proved to have tetrahedral and octahedral geometry from the results of UV–Vis spectra and magnetic moment. Analysis of the IR spectra of both ligands and complexes ascertained that the ligands behaved as monobasic tridentate coordinating to the metal ion center through azomethine-nitrogen atoms and thiadiazole ring in addition to deprotonated SH group. The synthesized ligands and their complexes were also investigated as inhibitors for the corrosion of carbon steel in 1.0 M HCl using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy and scanning electron microscopy techniques. The obtained results revealed that the inhibition efficiencies of the tested derivatives were found to depend on the concentrations and structures of such derivatives, and were decreased with raising temperature. At the same inhibitors concentration, the inhibition efficiencies are slightly increased in the order: LH > LCl > LH-Co > LCl-Co. The results derived from all applied techniques are harmonious with each other.

Mechanochemical synthesis of carbon-stabilized Cu/C, Co/C and Ni/C nanocomposites with prolonged resistance to oxidation

Metal-carbon nanocomposites possess attractive physical-chemical properties compared to their macroscopic counterparts. They are important and unique nanosystems with applications including in the future development of nanomaterial enabled sensors, polymer fillers for electromagnetic radiation shields, and catalysts for various chemical reactions. However, synthesis of these nanocomposites typically employs toxic solvents and hazardous precursors, leading to environmental and health concerns. Together with the complexity of the synthetic processes involved, it is clear that a new synthesis route is required. Herein, Cu/C, Ni/C and Co/C nanocomposites were synthesized using a two-step method including mechanochemical treatment of polyethylene glycol and acetates of copper, nickel and cobalt, followed by pyrolysis of the mixtures in an argon flow at 700 °C. Morphological and structural analysis of the synthesized nanocomposites show their core-shell nature with average crystallite sizes of 50 (Cu/C), 18 (Co/C) and 20 nm (Ni/C) respectively. The carbon shell originates from disordered sp2 carbon (5.2–17.2 wt.%) with a low graphitization degree. The stability and prolonged resistance of composites to oxidation in air arise from the complete embedding of the metal core into the carbon shell together with the presence of surface oxide layer of metal nanoparticles. This approach demonstrates an environmentally friendly method of mechanochemistry for controllable synthesis of metal-carbon nanocomposites.

Shape-Memory Metallopolymer Networks Based on a Triazole-Pyridine Ligand.

Shape memory polymers represent an interesting class of stimuli-responsive polymers. With their ability to memorize and recover their original shape, they could be useful in almost every area of our daily life. We herein present the synthesis of shape-memory metallopolymers in which the switching unit is designed by using bis(pyridine–triazole) metal complexes. The polymer networks were synthesized via free radical polymerization of methyl-, ethyl- or butyl-methacrylate, tri(ethylene glycol) dimethacrylate and a methacrylate moiety of the triazole–pyridine ligand. By the addition of zinc(II) or cobalt(II) acetate it was possible to achieve metallopolymer networks featuring shape-memory abilities. The successful formation of the metal-ligand complex was proven by Fourier transform infrared (FT-IR) spectroscopy and by 1H NMR spectroscopy. Furthermore, the shape-recovery behavior was studied in detailed fashion and even triple-shape memory behavior could be revealed.

TETRASUBSTITUTED (4-CHLOROPHENOXY)- AND (2,4,5-TRICHLOROPHENOXY)PHTHALOCYANINE METAL(II) COMPLEXES AND THEIR SULPHONATED DERIVATIVES: SYNTHESIS AND PROPERTIES

By template condensation of 4-(4-chlorophenoxy)- and 4-(2,4,5-trichlorophenoxy)phthalonitriles with cobalt(II), copper(II) and zinc(II) acetates, the corresponding metal(II) phthalocyaninates were synthesized, and some of their sulfonic acid derivatives were also isolated after sulphonation reactions. The spectroscopic characteristics and some physicochemical properties of the synthesized compounds were also given.

Selective removal of anionic dyes with exceptionally high adsorption capacity and removal of dichromate (Cr2O72-) anion using Ni-Co-S/CTAB nanocomposites and its adsorption mechanism

An adsorbent Ni-Co-S/CTAB nanocomposites have been synthesized at low temperature in aqueous medium using nickel acetate, cobalt acetate, thioacetamide and hexadecyltrimethyl ammonium bromide (CTAB) as reagents. The nanocomposites exhibited exceptionally high adsorption capacity towards anionic adsorbates with high selectivity. The maximum adsorption capacity of nanocomposites were 1995.02 mg g−1 for Congo red (CR), 2223.15 mg g−1 for Methyl orange (MO) anionic dyes and 790.69 mg g−1 for Cr2O72- metal anion. They exhibit negligible adsorption ability towards cationic dyes 2.33 mg g−1 for MB and 42.05 mg g−1 for RhB. The nanocomposite is able to adsorb anionic dyes from a binary mixture of cationic and anionic dyes with high separation factor. It also shows good results with synthetic effluents. The removal of adsorbates followed modified Zhu and Gu isotherm model. FTIR and Zeta-potential measurement confirmed that electrostatic interactions are predominating factor for the adsorption of anionic adsorbates followed by hydrophobic interactions between adsorbates. Moreover, ethanol is used to regenerate the adsorbent and reused up to five times with good adsorption capacities. Thus, the nanocomposite can be used as an efficient adsorbent for the removal and seperation of anionic adsorbates from binary mixtures as well as synthetic effluents.