Cobalt Acetate Research Articles

Effect of synthesis conditions on the bifunctional electrocatalytic properties of Co3O4/N-rGO for ORR and OER

The design of bifunctional non-precious metal catalyst with good ORR and OER activity is of great significance for the development and commercialization of fuel cells. However, the sluggish and strong irreversible nature of the oxygen electrochemical kinetics makes it difficult to manufacture single bifunctional material. Therefore, we prepared a bifunctional catalyst (Co3O4/N-rGO) with different particle diameters through a one-pot synthesis method, and studied the dependence of the electrocatalytic performance of the catalyst on the particle size of Co3O4. The results showed that Co3O4/N-rGO with 27–31 nm particle size prepared by using N-rGO as the carrier, cobalt acetate concentration of 0.075 M, hydrothermal temperature of 190 °C, and hydrothermal time of 3 h takes a 4e-reaction pathway, which exhibited better ORR and OER activity, excellent current stability and methanol tolerance than JM 20% Pt/C and JM 5% RuO2/C.

Transformations of Cobalt(II) Trifluoroacetates in 1,4-Dioxane: Solvent Effect on the Composition, Structure, and Crystal Packing of the Molecules

The reaction of aqueous cobalt(II) acetate with trifluoroacetic acid in methanol affords complex [Co(OOCF3)2(OH2)4] (I). The same reaction in a methanol–benzene–dioxane mixture of solvents gives mononuclear complex [Co(OOCF3)2(OH2)6] ∙ O(CH2CH2)2O (II) in which the solvate dioxane molecule forms a single crystal by the formation of hydrogen bonds with coordinated water molecules. A similar reaction in pure dioxane affords trinuclear complex {Co3(OOСCF3)4(OH2)2(OOСCF3)2[O(CH2CH2)2O]2} ∙ 2HOOСCF3 ∙ 2O(CH2CH2)2O (III) containing both solvate and coordinated dioxane molecules. The crystallization of complex III from an isopropanol–dioxane mixture leads to complex [Co(OOСCF3)2(OH2)4] ∙ 2O(CH2CH2)2O (IV). The reaction of complex III with pyrazole (HРz) affords mononuclear complex [Co(OOСCF3)2(HРz)4] ∙ 2O(CH2CH2)2O (V). The reaction of complex I with HРz in methylene dichloride leads to mononuclear complex [Co(OOСCF3)2(HРz)4] (VI). The structures of coordination compounds I–VI are determined by X-ray diffraction analysis (СIF files CCDC nos. 1985667 (I), 1985666 (II), 1985671 (III), 1985670 (IV), 1985665 (V), and 1985669 (VI) at Т = 296(2) K and 1985668 (VI) at Т = 150(2) K).

CoNiMo/Al2O3 sulfide catalysts for dibenzothiophene hydrodesulfurization: Effect of the addition of small amounts of nickel

Trimetallic CoNiMo hydrodesulfurization (HDS) catalysts were herein synthesized on Al2O3 support through an incipient wetness co-impregnation procedure using ammonium heptamolybdate and cobalt (and nickel) acetate as precursors. CoNiMo catalysts were obtained by adding in a small proportion of nickel with a molar amount representing between 1 and 10% of the total Co atomic loading. This addition of low amounts of nickel allows keeping the (Co + Ni)/(Co + Ni + Mo) molar ratio close to the optimum value of 0.3. The as-formed catalysts were labeled as CoNixMo/Al2O3 with x the relative stoichiometry of Ni compared to Co. Catalysts were then characterized by N2 adsorption-desorption isotherms, X-ray diffraction, ICP-OES spectroscopy, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalysts were tested in the HDS of dibenzothiophene (DBT). Results show a significant impact of adding small amounts of nickel to alumina-supported Co-promoted MoS2 on the final HDS activity. While up to CoNi0.03Mo/Al2O3, the resulting HDS activity is hardly influenced by the addition of nickel, a strong beneficial effect is observed for CoNi0.05Mo/Al2O3 with activity reaching a value of 7.2 × 10−7 mol.gcat−1.s−1. Increasing further, the amount of nickel abruptly decreased the DBT HDS activity. Interpretation of these results is then provided considering the additional role of nickel for improving the intrinsic activity of the HDS sites.

Ethylene glycol assisted solvo-hydrothermal synthesis of NGr-Co3O4 nanostructures for ethanol electrooxidation

Different morphologies of Co3O4 nanostructures grown on nanographitic flakes have been synthesized based on the decomposition of cobalt acetate precursor in water, ethylene glycol and water (50%)-ethylene (50%) solution at 180 °C for 18 h via a solvo-hydrothermal process. A subsequent electrophoretic deposition process is used to form composite layers on stainless steel plates. The composite layer fabricated in the water (50%)-ethylene (50%) solution is found to have the best electrocatalytic performance for ethanol electrooxidation due to the hierarchical nanoporous microstructures of Co3O4 exhibiting the lowest onset voltage for ethanol electrooxidation (around −0.3 V vs. Ag/AgCl) among the fabricated electrocatalyst layers. Moreover, the ethanol electrooxidation current for the electrode fabricated in the water (50%)-ethylene glycol (50%) reaches roughly 6.6 mA/cm2, while it is about 3.3 mA/cm2 at 0.5 V (vs. Ag/AgCl) for the electrode fabricated in pure ethylene glycol (values obtained after 1-h stability tests). The electrode fabricated in pure water is confirmed to not exhibit significant ethanol electrooxidation.

Development of Greener D-Metal Inorganic Crosslinkers for Polymeric Gels Used in Water Control in Oil and Gas Applications

Crosslinkable polymers, such as polyacrylamide (PAM), are widely applied for water control in oil and gas reservoirs. Organic and inorganic crosslinkers are used to formulate a gel with PAM. Although chromium has a high level of toxicity, it has been implemented as an effective crosslinker combined with carboxylates because of the controllability of crosslinking time at low temperatures. The objective of this work was to develop greener d-metal inorganic crosslinkers based on cobalt, copper, and nickel to replace chromium for application at reservoir conditions. The obtained results showed that the gelation chemistry of the developed systems depends on the metal charge density. The gelation of PAM with d-metals depends on pH and temperature for low- and high-charge density, respectively. Cobalt (II) acetate (CoAc) was effective at high temperatures (130–150 °C) and forms (4% CoAc + 9%PAM) stable, and strong gels at a pH > 7 with a storage modulus exceeding 4300 Pa. However, Nickel Acetate and Cupper Acetate formed stable weak gels at low temperatures (50–70 °C) and a pH > 6 and gel decomposition was observed upon increasing the temperature. The developed formulations were compatible with low-salinity water (1000 ppm NaCl).

Synthesis and electrochemical properties of calcium cobaltate as novel anode material

The calcium cobaltate (Ca3Co4O9) is synthesized through rheological phase reaction method using calcium gluconate (Ca(C6H12O6)2), citric acid (C6H8O7) and cobalt acetate tetrahydrate (CoAc2·4H2O) as raw materials. The germanium dioxide (GeO2) and bismuth nitrate pentahydrate (Bi (NO3)3·5 H2O) or both of them are used as precursors to synthesize Ge and Bi cation-doped calcium cobaltate (Ca3Co4O9) to improve its electrochemical properties. At first, the precursors were formed at 120 °C for 12 h using rheological phase mixtures of designed raw materials. Then, precursors were heated at different temperatures to obtain calcium cobaltate (Ca3Co4O9) samples. Because of doping of Ge4+ or Bi3+ or both of them, the conductivity and electrochemical performances for Ca3Co4O9 could be improved to a certain degree. The electrochemical tests showed that its electrochemical performances are depended on its calcination temperature and different kinds of doping. When calcined temperature was set at 750 °C, sample doped by both Ge4+ and Bi3+ (such as designed expected compound Ca2.85Bi0.15Co3.85Ge0.15O9) exhibited high reversible capacity at current density of 100 mAg−1 in voltage range of 0.01–3.0 V, and its reversible capacity could maintain at 550 mAhg−1 after 50 cycles. The reasons for Ca2.85Ge0.15Co3.85Bi0.15O9 to exhibit outstanding electrochemical properties were discussed also. The calcium cobaltate (Ca3Co4O9) doped by both Ge4+ and Bi3+ is a promising anode material for lithium ion battery application.

Rationally Designed Synthesis of Metal–Organic Framework-Derived Cobalt Oxide with Abundant Surface Active Sites for Efficient Catalytic Oxidation Performance

In this paper, Co3O4 was synthesized using pyrolysis of Co-L3, which was prepared by a solvothermal method at different temperatures using a naphthalimide derivative (L3) and cobaltous acetate. The L3 ligands were synthesized using a precursor of naphthalene-1,4,5,8-tetracarboxylic acid and p-aminobenzoic acid. Co-L3-120, Co-L3-160, and Co-L3-200 displayed respectively a one-dimensional (1D) rod structure, a two-dimensional sheet structure, and a 1D spindle structure due to the different structure units. After pyrolysis, the Co3O4 catalysts maintained the same morphologies of the corresponding Co-L3, which was made up of granulum. The Co3O4-160 catalyst presented superior catalytic performance for catalytic combustion of toluene due to the higher redox properties, abundant surface active sites and active oxygen species, higher oxygen vacancies, and higher surface acidities. Further, Co3O4-160 had excellent repetitiveness in three cycling tests and outstanding stability of thermal and moisture resistance.

Oxidative Desulfurization of Dibenzothiophene Using Cobalt (II) Complexes with Substituted Salen-Type Ligands as Catalysts in Model Fuel Oil

Three cobalt(II)-salen complexes (CoL1, CoL2 and CoL3) were synthesized via the reaction of the three tetradentate ligands as N,N′-ethylenebis(salicylimine) L1, N,N′-ethylenebis(3-tert-butylsalicylimine) L2 and N,N′-ethylenebis(3,5-di-tert-butylsalicylimine) L3, with a stoichiometric amount of cobalt(II) acetate tetrahydrate, respectively. All the three complexes were studied as oxidative desulfurization catalyst on dibenzothiophene taken in model fuel oil n-dodecane. The acetonitrile used as an extracting solvent and H2O2 as an oxidant. Comparatively CoL3 proved to be the best catalyst which showed the 76% DBT removal at the optimized conditions. The nth-order kinetic model is the best way to represent oxidation kinetics of complexes. This cobalt(II) Schiffs base complexes were studied as catalyst for oxidative desulfurization of dibenzothiphene (DBT) taken as model sulphur compounds in fuel model oil (n-dodecane) using H2O2 as oxidant and acetonitrile as extracting solvent for DBT sulfone in a batch experiment.

Study of the Products of the Interaction of Cobalt(II) Acetate with 2-Iodoterephthalic Acid and 1,10-Phenanthroline

A B S T R A C TIn the present work, the interaction of cobalt(II) acetate with 2-iodoterephthalic acid and 1,10-phenanthroline (phen) in N,N-dimethylformamide (DMF) was studied. The reaction leads to the formation of two products: hexa­kis­(N,N-di­methyl­formamide-κO)cobalt(II) bis­­(iodide) (compound 1) and MOF [Co(TP)(phen)·2DMF·2H2O] (compound 2), where TP is terephthalate dianion. Compound 1 crystallizes in the monoclinic space group Р2 1/с with cell parameters a = 14.2974(4) A, b = 10.7983(4) A, c = 20.6437(9) A, V = 3183.23 A3. The MOF was characterized by elemental analysis, infrared spectrometry, X-ray diffraction, scanning electron microscopy, thermogravimetry and volumetric nitrogen adsorption/desorption. The sample has permanent porosity and a microporous structure with a large surface area corresponding to the adsorption type I. Thermolysis of MOF leads to the formation of nitrogen-doped carbon nanomaterials Co/CoO@C.

Bulky-substituted phthalodinitriles and cobalt and copper phthalocyanines based on them: synthesis, thermal analysis and spectroscopic properties

By the nucleophilic substitution of the nitro group in 4-nitrophthalononitrile for the residues of alkoxy-substituted phenols, the synthesis of alkoxyphenoxyphthalonitriles was carried out. By template condensation of the substituted phthalonitriles obtained with copper and cobalt acetates at 200 °C, the corresponding phthalocyaninates were obtained. The conditions for the isolation and purification of the complexes synthesized were selected. The stability of substituted phthalonitriles and phthalocyaninates synthesized based on them regarding to heating in an argon–oxygen medium was evaluated (1:1 ratio). It was found the compounds obtained are thermally stable, and the destruction of phthalocyanines begins at lower temperatures compared to the corresponding phthalonitriles. For the complexes synthesized, the spectroscopic properties in organic solvents and concentrated sulfuric acid were studied. The influence of the nature of the substituent, metal complexing agent and solvent on the nature of the spectroscopic curves and the position of the main absorption band of phthalocyanine complexes has been established. It is noted passing from polar aprotic solvents to nonpolar ones, a shift of the maximum of the Q absorption band for the studied macrocycles was observed. Electronic absorption spectra in sulfuric acid show a significant bathochromic shift of the absorption band. An increase in the length of the alkyl substituent practically was found not to affect the position of the absorption maximum. Passing from complexes with Co(II) to Cu(II), a bathochromic shift of the absorption maximum was observed.

Catalytic Asymmetric Electrochemical α-Arylation of Cyclic β-Ketocarbonyls with Anodic Benzyne Intermediates.

Asymmetric catalysis with benzyne remains elusive because of the highly fleeting and nonpolar nature of benzyne intermediates. Reported herein is an electrochemical approach for the oxidative generation of benzynes (cyclohexyne) and its successful merging with chiral primary aminocatalysis, formulating the first catalytic asymmetric enamine-benzyne (cyclohexyne) coupling reaction. Cobalt acetate was identified to stabilize the in situ generated arynes and facilitate its coupling with an enamine. This catalytic enamine-benzyne protocol provides a concise method for the construction of diverse α-aryl (α-cyclohexenyl) quaternary carbon stereogenic centers with good stereoselectivities.

Direct Thermal Pyrolysis Enabling the Use of Cobalt Oxides Nanoparticles from Commercial Acetates as High-Capacity Anodes for Lithium-Ion Batteries

An unprecedentedly facile, cheap, green, and scalable approach to fabricate cobalt oxides nanoparticles has been developed in this work. By directly annealing cobalt acetate tetrahydrate, Co3O4 wit...

Catalytic Asymmetric Electrochemical α‐Arylation of Cyclic β‐Ketocarbonyls with Anodic Benzyne Intermediates

AbstractAsymmetric catalysis with benzyne remains elusive because of the highly fleeting and nonpolar nature of benzyne intermediates. Reported herein is an electrochemical approach for the oxidative generation of benzynes (cyclohexyne) and its successful merging with chiral primary aminocatalysis, formulating the first catalytic asymmetric enamine–benzyne (cyclohexyne) coupling reaction. Cobalt acetate was identified to stabilize the in situ generated arynes and facilitate its coupling with an enamine. This catalytic enamine‐benzyne protocol provides a concise method for the construction of diverse α‐aryl (α‐cyclohexenyl) quaternary carbon stereogenic centers with good stereoselectivities.

A cobalt(II) coordination polymer constructed with the 2-carboxy-phenoxyacetate linker showing a corrugated layer structure: synthesis, structure analysis and magnetic properties

Abstract A new binary CoII coordination polymer, [Co(2-cpa)2(H2O)] n (1) has been synthesized by a hydrothermal reaction of cobalt(II) acetate tetrahydrate and 2-carboxy-phenoxyacetic acid (2-H2cpa) in the presence of potassium hydroxide. Structural analysis revealed that the central CoII ion is in an octahedral geometry coordinated with one aqua and five oxygen atoms of three 2-carboxy-phenoxyacetate (2-cpa) ligands. The 2-cpa anions function as pentadentate double bridging chelate-μ 3 linkers binding neighboring CoII ions together, to form an unusual corrugated (4,4)-connected layer. Variable-temperature magnetic susceptibility data in the 2–300 K temperature range indicates a weak antiferromagnetic coupling between adjacent cobalt(II) ions.

Laser Irradiation in Liquid to Release Cobalt Single-Atom Sites for Efficient Electrocatalytic N2 Reduction

We synthesize Co single atoms anchored on N-doped carbon (Co-SAs/NC) by carbonizing a mixture of cobalt acetate, tartaric acid, and polyvinylpyrrolidone. The Co-SAs/NC exhibits nitrogen reduction r...

Electroplated $${\hbox {Co}_{3}}{\hbox {O}_{{4}}}$$ selective coatings for high-temperature solar thermal applications

This communication presents the optical characterization of $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ films electroplated on Cu- and Ni-coated Cu substrates. $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ films were successfully deposited by using the electrochemical deposition method with cobalt acetate tetrahydrate as a cobalt precursor followed by annealing at $$350^{\circ }\hbox {C}$$. The as-prepared films were characterized using X-ray diffraction, UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and stagnation temperature test. The characterization shows the presence of only the cubic spinal $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ phase in all films. The morphological analysis revealed the generation of unique fish-shaped $$\hbox {Co}_{{3}}\hbox {O}_{{4}}$$ particles with uniform size distribution for the films obtained on the Ni-coated Cu substrate. The Cu substrate with and without nickel plating used for deposition has shown a profound effect on the optical characteristics of films. The solar absorbance as high as 0.96 and thermal emittance as low as 0.02 were obtained for the films deposited on the Ni-coated Cu substrate. The highest value of the figure of merit $$(F_{{1}})$$ of $$\sim $$0.34 and extrapolated stagnation temperature of $$\sim $$362$$^{\circ }\hbox {C}$$ were realized for films having better optical characteristics. The results obtained indicate very good potential of the deposited films for solar thermal applications.

Металлосодержащие нанокомпозиты на основе солей насыщенных монокарбоновых кислот кобальта(II)

Синтезированы соли кобальта(II) насыщенных монокарбоновых кислот – муравьиной, масляной, валериановой, капроновой, энантовой, каприловой. Полученные соединения охарактеризованы с помощью элементного анализа, ИК-спектроскопии, термогравиметрии и дифференциально-сканирующей калориметрии. В результате термического разложения синтезированных карбоксилатов, а также ацетата кобальта получены кобальтсодержащие нанокомпозиты. Полученные нанокомпозиты исследованы методами элементного анализа, ИК-спектроскопии, сканирующей и просвечивающей электронной микроскопии, энергодисперсионной рентгеновской спектроскопии и рентгенофазового анализа. Проведены магнитные исследования полученных нанокомпозитов.

Electrophoretic deposition of nanographitic flakes/Co3O4 nanocomposite layers synthesized by solvothermal process for improved lithium-ion-battery anode

Different morphologies of Co3O4 nanopoarticles formed on nanographitic flakes are synthesized based on the decomposition of cobalt acetate precursor in ethylene glycol at 180 ​°C for 18 ​h by a solvothermal process followed with a heat treatment at the different temperatures of 350, 450, and 550 ​°C. Then, an electrophoretic deposition process is used to form the composite layers on the stainless steel plates. Among those temperatures, the layer prepared at 450 ​°C shows superior morphology and less aggregated nanoparticles, which is consistent with the electrochemical battery experiments. The electrode fabricated at 450 ​°C shows a charge capacity of 428 ​mA/g after 50 cycles at 1 A/g with a total retention of 90% which is higher than the charge capacities of the other electrodes heated at 350 and 550 ​°C. The cycling and rate performance results for the fabricated electrode heated at 450 ​°C manifest the superior distribution of the Co3O4 nanoparticles on the nanographitic flakes.

Eco-friendly synthesis, structural properties and morphology of cobalt hydroxide and cobalt oxide nanoparticles using extract of Litchi chinensis

Cobalt hydroxide and cobalt oxide nanoparticles (NPs) were prepared using extract of Litchi cinensis via a simple boiling of a solution of the extract and cobalt acetate tetrahydrate; and also by a rapid microwave-assisted method. Structural and morphological characterization of the synthesized NPs were carried out using X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FTIR). The XRD patterns revealed that the cobalt hydroxide obtained via the two approaches were the β form, with space group of P-3ml, and the product from the microwave route yielded particles with higher crystallinity. TEM analysis showed that the Co(OH)2 nanoparticles have similar spherical morphologies and monodispersity. Cobalt oxide (Co3O4) nanoparticles, were obtained by the calcination of the hydroxide species and resultant loss of both the water molecule and the phytochemical component of the particles, and showed elongated rod like morphology. The diffraction peaks of the Co3O4 nanoparticles were indexed as Face-centered cubic phase with a space group of Fd-3m. This green approach, without the use of any chemical reagent, proves to be an efficient, simple, fast and cost effective route for the synthesis of Co(OH)2 and Co3O4NPs which may be used in various applications.

CO2 hydrogenation and ethanol steam reforming over Co/SiO2 catalysts: Deactivation and selectivity switches

Two 20 wt.% Co/SiO2 catalysts have been prepared using silica gel as a support and cobalt acetate or nitrate as precursors. They were characterized before and after reaction using XRD, skeletal IR and DR-UV–vis-NIR spectroscopies and FE-SEM microscopy. Fresh catalysts are active in CO2 methanation at atmospheric pressure but rapidly deactivate at 623–673 K, due to formation of encapsulating carbon. However, they retain a more stable activity in producing CO by the reverse water gas shift (rWGS) reaction. Methanation and rWGS appear to occur on independent sites. The Co/SiO2 catalyst produced from Co-acetate precursor shows stable activity in Ethanol Steam Reforming (ESR) at 873−973 K, producing also carbon whiskers (nanotubes) that, however, do not cause catalyst deactivation at the laboratory conditions and timescale. The catalyst produced starting with Co-nitrate is even more active in ESR but it deactivates fast. At lower temperature or when deactivated with respect to ESR, both catalysts shift to high activity in ethanol dehydrogenation to acetaldehyde, showing that the ability to activate water is mostly lost. The differences observed among catalysts produced from cobalt acetate and cobalt nitrate precursors can be associated to the different pH of the impregnating solution. The higher pH of cobalt acetate solution results in surface dissolution / hydrolysis of silica and this may be at the origin of the formation of cobalt silicate surface species, which can also stabilize the support against high temperature reactivity. This might favor larger Co particles formation, less active, but also giving rise to inert cobalt species.