Thermal Decomposition Of Co Research Articles

On the synthesis and characterization of bimagnetic CoO/NiFe2O4 heterostructured nanoparticles

Bimagnetic nanoparticles show promise for applications in energy efficient magnetic storage media and magnetic device applications. The magnetic properties, including the exchange bias of nanostructured materials can be tuned by variation of the size, composition, and morphology of the core vs overlayer of the nanoparticles (NPs). The purpose of this study is to investigate the optimal synthesis routes, structure and magnetic properties of novel CoO/NiFe2O4 heterostructured nanocrystals (HNCs). In this work, we aim to examine how the size impacts the exchange bias, coercivity and other magnetic properties of the CoO/NiFe2O4 HNCs. The nanoparticles with sizes ranging from 10 nm to 24 nm were formed by synthesis of an antiferromagnetic (AFM) CoO core and deposition of a ferrimagnetic (FiM) NiFe2O4 overlayer. A highly crystalline magnetic phase is more likely to occur when the morphology of the core-overgrowth is present, which enhances the coupling at the AFM-FiM interface. The CoO core NPs are prepared using thermal decomposition of Co(OH)2 at 600 °C for 2 hours in a pure argon atmosphere, whereas the HNCs are obtained first using thermal evaporation followed by hydrothermal synthesis. The structural and morphological characterization made using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), and scanning electron microscopy (SEM) techniques verifies that the HNCs are comprised of a CoO core and a NiFe2O4 overgrowth phase. Rietveld refinement of the XRD data shows that the CoO core has the rocksalt (Fd3 m) crystal structure and the NiFe2O4 overgrowth has the spinel (C12/m1) crystal structure. SEM-EDS data indicates the presence and uniform distribution of Co, Ni and Fe in the HNCs. The results from PPMS magnetization measurements of the CoO/NiFe2O4 HNCs are discussed herein.

Synthesis of metal oxide nanoparticles by facile thermal decomposition of new Co(II), Ni(II), and Zn(II) Schiff base complexes- optical properties and photocatalytic degradation of methylene blue dye

Three new Co(II), Ni(II), and Zn(II) complexes of tridentate ONN ligand were synthesized from the reaction of 2-amino-3-hydroxypyridine and pyrole-2-carboxyaldehyde and characterized using physio-chemical and analytical methods such as NMR, elemental analyzer, FT-IR, ESI-MS, and magnetic moment measurement. The collected data indicated that prepared complexes have metal:ligand ratio of 1:1 and octahedral geometry for Co(II) and Ni(II) while tetrahedral geometry for Zn(II) complex. The synthesized complexes are utilized as precursors for synthesizing Co3O4, NiO, and ZnO NPs by thermal decomposition at 600 °C, and their structures were defined by PXRD, SEM, UV-DRS, FT-IR, and EDAX. By using Scherrer equation, the average crystallite size calculated for Co3O4, NiO, and ZnO nanoparticles are 22, 18, and 24 nm, respectively. The energy band gap of Co3O4, NiO, and ZnO nanoparticles are 1.67, 3.34, and 3.12 eV, respectively, according to the Tauc baseline calculation, revealing their semiconducting nature. Co3O4, NiO, and ZnO nanoparticles were employed for photocatalytic degradation of methylene blue dye in sunlight. After 105 min., the maximum percentage of MB dye degradation for Co3O4, NiO, and ZnO was found to be 80 %, 81.2 %, and 86.68 %, respectively.

Thermal Decomposition of Co–Cu Double Salicylate Complex under Argon Atmosphere Resulting in Metal–Carbon Compositions

Thermal Decomposition of Co–Cu Double Salicylate Complex under Argon Atmosphere Resulting in Metal–Carbon Compositions

Facile synthesis of ZnO and Co3O4 nanoparticles by thermal decomposition of novel Schiff base complexes: Studying biological and catalytic properties

In this paper, a novel Zn(II) and Co(II) Schiff base complexes were synthesized by template method via refluxing 2,3-Naphthalenedicarboxaldehyde, Metal(II) chloride (Metal = Zn or Co), and L-phenylalanine. ZnO and Co 3 O 4 nanoparticles were synthesized by thermal decomposition of Zn(II) and Co(II) complexes, respectively. The products were characterized using different instruments such as CHN, Conductivity, FT-IR, XRD, HR-TEM, and UV–Vis spectrophotometer. The experimental results of elemental analysis for Zn(II) and Co(II) complexes, agree with the calculated results, indicating that the Zn(II) and Co(II) complexes have 1:1 ligand/metal ratios. The molar conductance of the Zn(II) and Co(II) complexes, is less than 5 Ω −1 cm −1 mol −1 , confirming the non-electrolytic nature of the synthesized complexes. The average crystallite diameter of the ZnO and Co 3 O 4 samples is 39.64 and 30.38 nm, respectively. The optical energy gap of the ZnO and Co 3 O 4 samples are 2.75 and 3.25 eV, respectively. Methylene blue dye was utilized to examine the photocatalytic properties of the synthesized nanoparticles using UV irradiations in the absence and presence of hydrogen peroxide. The % degradation of the methylene blue dye in the presence of hydrogen peroxide using ZnO and Co 3 O 4 samples after 40 min is 94.55 and 98.98, respectively. Six pathogenic microbes were utilized to examine the antimicrobial properties of the synthesized Schiff base complexes and their nanoparticles: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Streptococcus species, Aspergillus species, and Candida species. Zn(II) and Co(II) complexes display inhibition towards all the studied microbes. Besides, ZnO and Co 3 O 4 nanoparticles exhibit less inhibition towards Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Streptococcus species. Moreover, ZnO and Co 3 O 4 nanoparticles have no activity towards Aspergillus and Candida species.

Facile synthesis of Co3O4 and ZnO nanoparticles by thermal decomposition of novel Co(II) and Zn(II) Schiff base complexes for studying their biological properties and photocatalytic degradation of crystal violet dye

Utilizing the metal complexes as low-cost precursors for the synthesis of metal oxide nanoparticles has been regarded as one of the most suitable and practical techniques that produce nanoparticles with low crystallite sizes. So, in this paper, Co3O4 and ZnO nanoparticles were facilely synthesized by thermal decomposition of novel Co(II) and Zn(II) Schiff base complexes. The Schiff bases, which were abbreviated as E1 and E2, were synthesized by condensation of 4-amino-5-ethyl-4H-1,2,4-triazole-3-thiol with 4-(dimethylamino)benzaldehyde and 2,4-dihydroxybenzaldehyde, respectively. The Co(II) and Zn(II) complexes were synthesized by condensation of Schiff bases with CoCl2•6H2O and ZnCl2, respectively. The Schiff bases, complexes, and nanoparticles were characterized using different tools such as 1HNMR, FT-IR, CHNS elemental analysis, TGA thermal analysis, XRD, HR-TEM, and UV–Vis spectrophotometer. The average crystallite size of ZnO samples, which were synthesized from the ignition of ZnE1 and ZnE2 complexes, is 34 and 44 nm, respectively. The average crystallite size of Co3O4 samples, which were synthesized from the ignition of CoE1 and CoE2 complexes, is 33 and 45 nm, respectively. The Co3O4 and ZnO nanoparticles were utilized for the photocatalytic degradation of crystal violet dye in aqueous media under UV illumination in the presence of hydrogen peroxide. The maximum% degradation of crystal violet dye using ZnO in the absence and presence of H2O2 is 78 and 98%, respectively. The maximum% degradation of crystal violet dye using Co3O4 in the absence and presence of H2O2 is 67 and 95%, respectively. Furthermore, the biological activities of the synthesized samples were studied against some bacterial and fungal strains. The complexes show moderate effect against bacterial strains whereas did not show any effect against fungal strains except ZnE1, CoE2, and ZnE2 which have moderate effect against Candida albicans fungi. The Co3O4 and ZnO nanoparticles show moderate effect against bacterial strains and did not show any effect against fungal strains.

Efficient and sustainable Co3O4 nanocages based nickel catalyst: A suitable platform for the synthesis of quinoxaline derivatives

The Co 3 O 4 nanocages has been synthesized based on the Kirkendall effect involving the thermal decomposition of prussian blue analogue Co 3 [Co(CN) 6 ] 2 nanocubes. Thereafter, the hollow cavity of Co 3 O 4 cages was loaded with Ni nanoparticles to synthesize the final nanocatalyst (Ni@Co 3 O 4 ). Highly versatile Co 3 O 4 nanocages based nickel catalytic system has been effectively exploited for the condensation of 1,2-diamines with α-diketones for the synthesis of quinoxaline derivatives. • 3D hollow architecture of Co 3 O 4 cages permits the integration of multiple catalytic active sites. • The synthesized nanocatalyst showed high catalytic efficacy with high conversions and TON of targeted products. • The developed nanomaterial exhibits excellent durability and reusability for 6 subsequent runs. • It is anticipated thatNi@Co 3 O 4 nanocatalyst would open new avenues in the field of catalysis. Engineered nanocages have emerged at the forefront of nanomaterial investigation as they possess tremendous potential to boost key chemical processes owing to their hollow architectures that can help in achieving high reactivity. With an intention to make profitable use of their morphological features guided chemical activity, we developed dispersable Co 3 O 4 nanocages decorated with nickel nanoparticles for accessing a broad spectrum of pharmaceutically and biologically active N-heterocyclic quinoxaline nuclei using α-dicarbonyls and 1,2-diamines as precursor reagents. For designing Co 3 O 4 nanocages, we employed a simple and scalable method involving Kirkendall effect in which thermal decomposition of Co 3 [Co(CN) 6 ] 2 was carried out thereafter, nanocages were loaded with Ni nanoparticles to obtain the final Ni@Co 3 O 4 catalyst. Results revealed that Ni@Co 3 O 4 catalyst possesses immense potential to accelerate condensation of diamines and di-carbonyls in absence of any additives under mild reaction conditions. The superior catalytic efficiency has been attributed to the hollow architecture of the nanocatalyst comprising of abundant catalytic sites. This protocol exhibits several remarkable attributes such as mild reaction conditions outstanding functional group tolerance, high yield, immense durability and reusability for six subsequent runs.

Кинетические параметры процесса термического разложения нанопорошка гидроксида кобальта при изотермических условиях

The paper focuses on the kinetic parameters of synthesizing Co3O4 nano-powder by thermal decomposition of hydroxide Co(OH)2 under isothermal conditions. The thermal decomposition of Co(OH)2 nano-powder under isothermal conditions was carried out in a tube furnace in the temperature range from 150 to 200 °C. Findings of research show that the thermal decomposition rate constant at 200 °C is approximately 2.7 times higher than that at 150 °C. Accordingly, for 80 min of thermal decomposition, the process accelerates 1.8 times. The activation energy of this process is approximately 33 kJ/mol, which indicates a mixed reaction mode. The study shows that Co3O4 nanoparticles obtained at the temperature of the maximum thermal decomposition rate, i.e. 180 °C, mainly consist of elongated ovoid and acicular aggregates with an average particle value of 47 nm and the length of up to 200 nm.

Variation of the Chain Geometry in Isomeric 1D Co(NCS)2 Coordination Polymers and Their Influence on the Magnetic Properties.

Two different isomers of [Co(NCS)2(4-chloropyridine)2]n (3C and 3L) were synthesized from solution and by thermal decomposition of Co(NCS)2(4-chloropyridine)2(H2O)2 (2), which show a different metal coordination leading to corrugated chains in 3C and to linear chains in 3L. Solvent mediated conversion experiments prove that 3C is thermodynamically stable at room temperature where 3L is metastable. Magnetic measurements reveal that the magnetic exchange in 3L is comparable to that observed for previously reported related chain compounds, whereas in 3C with corrugated chains, the ferromagnetic interaction within the chains is strongly suppressed. The magnetic ordering takes place at 2.85 and 0.89 K, for 3L and 3C, respectively, based on specific heat measurements. For 3L the field dependence of magnetic relaxations in antiferromagnetically ordered ferromagnetic chains is presented. In addition, 3L is investigated by FD-FT THz-EPR spectroscopy, revealing a ground to first excited state energy gap of 14.0 cm-1. Broken-symmetry DFT calculations for 3C and 3L indicate a ferromagnetic intrachain interaction. Ab initio CASSCF/CASPT2/RASSI-SO computational studies reveal significantly different single-ion anisotropies for the crystallographically independent cobalt(II) centers in 3C and 3L. Together with the geometry of the chains this explains the magnetic properties of 3C and 3L. The ab initio results also explain the weaker exchange interaction in 3C and 3L as compared to previously reported [Co(NCS)2(L)2]n compounds with linear chains.

Preparation of nano-Co3O4-coated Albizia procera-derived carbon by direct thermal decomposition method for electrochemical water oxidation

It is obtained that nano-Co3O4-coated carbon prepared by thermal decomposition of Co(NO3)2·6H2O at 300 °C on home-made Albizia procera (Roxb.) leaves derived carbon is an efficient electrocatalyst for electrochemical water oxidation in 0.1 M NaOH (aq.) solution. The loading of nano-Co3O4 on the carbon was changed by varying the amount of precursor of cobalt (100–1000 mg) and using a constant amount of the carbon (200 mg) during thermal decomposition. The prepared samples were characterized by physical techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), thermo-gravimetric analysis (TGA), fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS). XRD, TEM, FESEM, and EDS confirmed the formation of uniformly distributed nanoparticles of single-phase Co3O4 on the surface of carbon. The XRD data reveals formation of nano-Co3O4 with average particle sizes in the range of 9–17 nm. The FESEM micrographs demonstrate that Co3O4 nanoparticles, having irregular morphology, are uniformly and densely covered on the surface of supporting carbon.. The prepared samples were immobilized on the filter paper derived carbon electrode (FPCE) to study their electrocatalytic properties toward water oxidation. The cyclic voltammetric studies showed that the nano-Co3O4-C prepared using 400 mg of Co(NO3)2·6H2O (nano-Co3O4-C-400), which possesses meso- and macropores with BET surface area of 192.4 m2/g, reaches a current density of 28 mAcm−2 at 1.5 V and electrochemical water oxidation starting potential of 0.7 V. In this work, it is also shown that the current densities, at 1.5 V, increase by increasing the amount of cobalt oxide in the prepared samples though. The nano-Co3O4-C-400 catalyst shows optimum performance for electrochemical water oxidation in terms of starting water oxidation potential, reasonable amount of Co3O4 and moderate level of current density at 1.5 V.

Unsupported cobalt nanoparticles as catalysts: Effect of preparation method on catalytic activity in CO2 methanation and ethanol steam reforming

Cobalt nanoparticles (10–50 nm) have been prepared by different procedures. Materials produced by reduction of cobalt chloride and nitrate by NaBH4 contain B impurities as borates or borides. They are very active in ethanol steam reforming at 673–773 K with up to 85% hydrogen yield at 773 K. B-free samples obtained by thermal decomposition of Co2(CO)8 is slightly less selective to hydrogen, due to its activity in ethanol cracking to methane which is probably poisoned by boron impurities on the other catalysts. B-containing samples are inactive in CO2 methanation and have weak activity in the reverse water gas shift (RWGS) reaction to CO. B-free nanoparticles have high activity in both CO2 methanation and RWGS. However, methanation activity is reduced fast by growth of encapsulating carbon species. These particles however also show quite stable activity in RWGS to CO, attributed to CoO impurities.

Effect of Co(NO3)2·6H2O thermal decomposition temperature on the nano-Co3O4 product morphology and electrocatalysis of water oxidation

Herein, we report the electrochemical water oxidation efficiency of nano-Co3O4 catalyst samples obtained by the thermal decomposition of Co(NO3)2·6H2O at various temperatures (320, 420, 520, and 620 °C). The structural and morphological details of the synthesized samples were determined by employing X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. These studies revealed the formation of well-dispersed nano-Co3O4 particles with sizes, shapes, and crystallinity levels that differed for the different decomposition temperatures. The prepared catalysts were immobilized on filter-paper-derived carbon electrodes for checking their electrochemical properties. The electrochemical efficiency levels of the Co3O4 catalyst samples were evaluated by employing each of them as an anode to study the water oxidation reaction. The nano-Co3O4 sample prepared at 420 °C yielded the highest efficiency and good stability towards the water oxidation reaction. The higher efficiency of this sample was attributed to the relatively small average size and low level of agglomeration of its nanoparticles, and to the high electrochemically active surface area of its electrode. Different morphology and crystallinity of nano-Co3O4 were prepared by simple and straightforward thermal decomposition of Co(NO3)2·6H2O for electrochemical water oxidation. The nano-Co3O4 prepared at 420 °C showed the highest efficiency and good stability towards water oxidation.

INFLUENCE OF FORMATION CONDITIONS OF THE SURFACIAL CATALYTICALLY ACTIVE CО3O4 COMPOUNDS ON THE DEGREE OF TOXIC GAS EMISSIONS NEUTRALIZATION

The catalytic purification of industrial plan and transport exhaust gases is present day the most effective mean to protect the environment and human health from toxic gas impurities exposure. A method of the Co3O4 catalytically active centers synthesis is described on the surface of a ceramic bulk corundum α-Аl2O3 carrier (3.4 mm corundum fraction), there is a process of neutralizing harmful gas emissions.The influence of temperature is investigated when Cо3O4 catalytically active compounds are formed during the thermal decomposition of the crystalline hydrate Co(NO3)2·6H2O on the conversion degree of vapor toxic impurities.Diffraction patterns made it possible todetermine that the surface compound of Cо3O4 on corundum agglomerates with growth of temperature. This agglomerationis a ordering measure of the catalytically active centers structure. It has been found experimentally that than higher is the heat treatment temperature, the more sophisticated and aggregative become formed compounds.The influence of surface concentration of the catalytically active centers on the value of purification degree during the heterogeneous catalytic process in the external diffusion region was studied. This influence is described by the Frendlich adsorption equation.

Shell-dependent antimicrobial efficiency of cobalt ferrite nanoparticles

Uniformly shaped and sized superparamagnetic nanoparticles (NPs) have recently received increasing attention due to their prospective applications in theranostics, sensing and as antimicrobials. However, utilization of magnetic NPs in nanomedicine largely depends on their properties, which, in turn, are influenced by the size, structure and composition of the core and the nature of stabilization shell. This paper highlights the significant influence of stabilizing shell of superparamagnetic cobalt ferrite NPs on the antimicrobial efficacy against several kinds of pathogenic microorganisms. Two very popular preparation methods of biocompatible magnetic NPs, namely, co-precipitation from alkaline solutions containing Co(II) and Fe(III) salts and L-lysine (Lys) as well as thermal decomposition of organometallic Co(II) and Fe(III) precursors in the presence of oleic acid were applied. The properties of resulting NPs are characterized and discussed herein. Surprisingly, highly efficient bactericidal behaviour of cobalt ferrite NPs capped with oleine shell compared to that of CoFe2O4@Lys, was ascribed to the differences in their surface charge and more grained structure of the former.

INVESTIGATION OF THE INFLUENCE OF ELECTROMAGNETIC FIELD AND ENERGY-MECHANICAL PROCESSING ON THE PRODUCTION OF METALLIC COBALT NANOPOWDER BY HYDROGEN REDUCTION

Nanopowders (NP) based on cobalt have significant prospects for use in various fields of science, engineering, industry and medicine. In this work the authors have studied the kinetics of the production of metallic cobalt nanopowder by hydrogen reduction of oxide material Co 3 O 4 in an electromagnetic field, an d with an energy-mechanical pro cessing (EMP) in eddy layer created by ferromagnetic bodies subjected to such field. Cobalt oxide Co 3 O 4 N P was obtained by thermal decom position of the hydroxide compound Co(OH) 2 chemical-precipitated from 10 % aqueous solutions of nitrate cobalt Co(NO 3 ) 2 and sodium hydroxide NaOH under the conditions of pH = 9 and t = 20 °C. The production of metallic cobalt nanoparticles by the hydr ogen reduc tion of Co 3 O 4 NP was carried out on the apparatus of eddy layer (AED) of UAP-3 model modified with an internal hea ting furnace and a flow reactor . The amplitude value of induction of magnetic field inside the reactor was 0.16 T. The experimental temperatures of the reduction process were chosen based on the result of a thermo gravimetric analysis (TGA) of the initial cobalt hydroxide sample. The kinetic parameters of hydroge n reduction processes under li near heating and in isothermal conditions were calculated using the Freeman-Carroll and McKewan models, respectively. The authors have found a decrease in the rate of obtaining Co nanopowder in the electromagnetic field (up to 14 % at 250 °C) due to the decrease in the adsorption ability of hydrogen atoms on the surface of the formed metallic nanoparticles. EMP in the eddy layer leads to an increase in the reduction rate by 4 – 5 times due to the effect of mechanical activation of the material. The properties of the initial material and the obtained products were investigated using the methods of thermogra vimetry, X-ray diffractometry, electron microscopy and measurement of the specific surface area by low-temperature nitrogen adsorption. It was shown that reduction of the samples in the electromagnetic field facilitate the formation of mo re finer-dispersed Co nanoparti cles, than in the case without the field. The EMP in the eddy layer leads to the aggregation of the formed metallic nanoparticles and the formation of granules of micron size.

Microstructure and Electrochemical Performance of Co₃O₄ Nanopillars Calcinated at Various Temperatures.

One-dimensional (1D) Co3O4 nanopillars were prepared by a facile hydrothermal-calcination method, which involved low thermal decomposition of Co(OH)y(CO3)0.5(2-y) · 11H2O at different temperatures. Microstructure, lithium-storage performance and the conductivity of the Co3O4 nanopillars calcined at different temperatures were systematically investigated. It was revealed that the calcined temperature has an effect on the particle size, crystallinity, and morphology of the Co3O4 nanopillars, which further influenced its electrochemical performance. It was found that when the calcined temperature and time were 450 °C and 2 h, respectively, the obtained Co3O4 nanopillars with the length of 60-100 nm and width of 30-40 nm, presented good lithium-storage performance with a high reversible capacity of 805.8 mAh g-1 after 30 cycles at a current density of 100 mA g-1. In addition, the Co3O4 nanopillars electrode possessed the smallest semicircle diameter, which implied that Co3O4 nanopillars presented the lowest contact and charge-transfer impedances, originating from its good crystallinity and 1D nanocolumnar structure.

Influence of a Rotary Electromagnetic Field and Mechanical Stimulation on the Production of Cobalt Nanopowder by Reduction with Hydrogen

Cobalt nanopowder is very promising for use in science, engineering, industry, and medicine. The present study focuses on the kinetics of nanopowder production by the reduction of cobalt oxide with hydrogen in an electromagnetic field, under the action of a bed of ferromagnetic particles rotating in the electromagnetic field. Cobalt oxide (Co3O4) nanopowder is obtained by the thermal decomposition of cobalt hydroxide Co(OH)2 deposited from 10% ionic solutions of cobalt nitrate Co(NO3)2 and sodium hydroxide NaOH at 20°C, with pH 9. Cobalt nanoparticles are produced from Co3O4 nanopowder in a modified UAP-3 vortical bed system with a built-in furnace and flow-through reactor. The amplitude of the magnetic induction within the reactor is 0.16 T. The experimental reduction temperature is selected on the basis of thermogravimetric analysis of the initial Co(OH)2 sample. The kinetic parameters of hydrogen reduction with linear heating and in isothermal conditions are calculated on the basis of the Freeman–Carroll and McKewan models, respectively. The rate of cobalt- nanopowder production slows in an electromagnetic field (by up to 14% at 250°C), on account of hindrance to the adsorption of hydrogen atoms at the surface of the metallic nanoparticles formed. However, mechanical stimulation in a vortical bed increases the rate of the process by a factor of 4–5 as a result of activation. The properties of the initial material and the products are studied by thermogravimetric analysis, X-ray diffraction analysis, scanning electron microscopy, and measurement of the specific surface by low-temperature nitrogen absorption. In the reduction of the samples, smaller cobalt nanoparticles are produced in the presence of an electromagnetic field. Mechanical stimulation in a vortical bed results in aggregation of the cobalt nanoparticles and the formation of microgranules.

3D Heterogeneous Co3O4@Co3S4 Nanoarrays Grown on Ni Foam as a Binder‐Free Electrode for Lithium‐Ion Batteries

AbstractCo3O4@Co3S4 nanoarrays on Ni foam (abbreviated as Co3O4@Co3S4 NAs) were prepared by using a facile synthesis method, which involves hydrothermal preparation, low‐temperature thermal decomposition of Co(OH)y(CO3)0.5(2‐y) ⋅ 11H2O, and sulfurization. The material exhibited good electrical conductivity, high specific capacity, and cycling stability with a reversible capacity of 1050 mAh g−1 at 200 mA g−1 after 40 cycles and an initial coulombic efficiency of 82.25 %. At a high current density (1500 mA g−1), the capacity reached up to 808.1 mAh g−1. The excellent lithium‐storage performance of Co3O4@Co3S4 NAs can be ascribed to the synergistic effect between Co3O4 and Co3S4, along with the contribution of the Ni foam. The method described in this paper can be extended to enhance the electrochemical performance of other metal oxides.

Synthesis of Co3O4/Ag/TiO2 nanotubes arrays via photo-deposition of Ag and modification of Co3O4 (311) for enhancement of visible-light photoelectrochemical performance

Abstract A composite Co 3 O 4 /Ag/TiO 2 nanotubes (NTs) electrode, that subsequently photo-reduction of Ag and thermal decomposition of Co 3 O 4 nanoparticles onto electrochemical anodized TiO 2 -NTs, was synthesized for enhancement of visible light photoelectrochemical (PEC) performance. The visible light response of Co 3 O 4 /Ag/TiO 2 -NTs with highest photocurrent of 0.54 mA/cm 2 was obtained under calcination temperature of 400 °C for Co 3 O 4 (311) crystal formation. The Co 3 O 4 /Ag/TiO 2 -NTs electrode provided a remarkable photoconversion efficiency of 0.18% at an on-set potential of 0.44 V which was twice than that of Co 3 O 4 /TiO 2 -NTs electrode (0.06%). The synergetic effect for degradation of nitrobenzene (NB) and reduction of Cr(VI) was studied to analyze the possible mechanism of Co 3 O 4 /Ag/TiO 2 -NTs. It was proposed that Ag nanoparticle acted as bridge transferred the photo-induced electrons from Co 3 O 4 to TiO 2 -NTs and then largely facilitated the electron-holes separation to enhance the PEC activity.

Sol-gel synthesis of CoFe2O4:SiO2 nanocomposites – insights into the thermal decomposition process of precursors

Succinate precursors dispersed in the silica matrix were obtained by sol-gel synthesis using Co and Fe nitrates, 1,4-butanediol and tetraethyl orthosilicate. The thermal decomposition of Co and Fe succinates into cobalt ferrite (CoFe2O4) at different CoFe2O4:SiO2 molar percentages was studied by thermal analysis, Fourier transformed infrared spectrometry (FT-IR) and X-ray diffraction. The morphology of nanoparticles was identified by transmission and scanning electron microscopy. The formation of succinates in the pores of the silica matrix and their decomposition to CoFe2O4 spinel was confirmed by the FT-IR spectra. The nanocrystallites size (7–33nm) increases with the decrease of SiO2 content, suggesting that the growth process of nanoparticles is reduced in the presence of silica matrix.

ONE STEP SYNTHESIS OF WATER-DISPERSIBLE CoFe2O4 MAGNETIC NANOPARTICLES USING TRIETHYLENETETRAMINE AS SOLVENT AND STABILISING LIGAND

Magnetic CoFe2O4 nanoparticles were synthesised by one step synthetic method through thermal decomposition of Co and Fe precursors in triethylenetetramine solvent at high temperature. The advantage of this method is the ability to make monodisperse nanoparticles with high water-dispersibility and stability. The particle size can be tuned in the range of 7-11.3 nm by varying synthetic conditions. The obtained particles with small DLS size (less than 21 nm) are ready to disperse and stable in aqueous solution for weeks without any surface modification.