Nano-sized Cobalt Oxide Research Articles

Radiation-induced preparation of nanoscale CoO@graphene oxide for activating peroxymonosulfate to degrade emerging organic pollutants

In this study, ionizing radiation was used to induce the in-situ formation of highly dispersed nanosized cobalt oxide on the surface of graphene oxide (R-Co-GO), which was highly effective for activating PMS to degrade sulfamethoxazole (SMX). R-Co-GO had the highest catalytic activity when 150 μL cobalt chloride hexahydrate solution was used in the precursor, and the pseudo first-order kinetic constant of SMX degradation was 0.07 min−1 with high mineralization efficiency (63.1 %) and high PMS utilization efficiency. The sulfate radicals and high-valent cobalt oxo were mainly responsible for SMX degradation. Mechanism analysis showed that cobalt active site dominated in PMS activation, which was responsible for the formation of sulfate radicals and high-valent cobalt oxo; while the carbon framework contributed to the formation of singlet oxygen. The R-Co-GO-150 had good catalytic activity and stability in five cycling experiments, in which SMX was completely degraded and the concentration of dissolved Co was below 0.1 mg/L. In addition, the R-Co-GO-150/PMS system could also degrade phenol, bisphenol A, atrazine and nitrobenzene effectively, confirming its wide applicability. This study provided a facile method to uniformly disperse the metal oxides on the surface of carbon materials, and an effective system for the removal of emerging organic pollutants from the actual wastewater.

Hierarchical Co3O4 decorated nitrogen-doped graphene oxide nanosheets for energy storage and gas sensing applications

Nano-sized cobalt oxide decorated nitrogen-doped graphene oxide (Co3O4@NGO) composite was produced by a feasible and cost-effective hydrothermal route for electrochemical supercapacitors and gas sensor applications. The composite materials formation was ascertained by Raman spectroscopy, X-ray diffraction, and X-ray photo electron spectroscopy analyses. Field emission scanning electron microscopy (FE-SEM) and field emission transmission electron microscopy (FE-TEM) results explored the controlled nanoscale-sized sheet-like morphology for the prepared composite materials. Electrochemical storage properties were studied by cyclic voltammetry (CV), galvanostatic charge–discharge process (GCD), and electrochemical impedance spectroscopy analyses using three-electrode configuration with 3 M KOH electrolyte. The observed results showed ~466 F/g specific capacitance at a current density of 1 A/g for Co3O4@NGO composite structure with the capacity retention of 96 % after 5000 cycles. Further, the synthesized Co3O4@NGO composite revealed improved detection response, cyclability, and linearity for dimethyl methyl phosphonate vapor gas sensing. The synthesized composite also demonstrated excellent selectivity, stability, sensitivity, and rapid response time.

Ammoxidation of Ethane to Acetonitrile and Ethylene: Reaction Transient Analysis for the Co/HZSM-5 Catalyst.

Ethane ammoxidation to acetonitrile and ethylene over the Co/HZSM-5 catalysts was revisited based on both transient and steady-state performance evaluation to elucidate the structure/reactivity relationships. We suggested that the exchanged Co2+ cation encapsulated in the zeolite favors the formation of acetonitrile and ethylene, whereas nanosized cobalt oxide particles without close proximity with the HZSM-5 only favor CO2 formation. Excess Brønsted acid sites of the zeolites may act as a reservoir for NH3, which inhibits the CO2 formation through the NH3-mediated oxidative dehydrogenation mechanism. According to the transient kinetic analysis, the time constants τ from the back-transient decay for NH3 and CO2 are both 7.7 min, which decreased to 2.7 min for acetonitrile and further decreased to 3–4 s for ethane, ethylene, and O2. Assuming first-order reaction kinetics, the rate constants for the formation of acetonitrile and CO2 are 0.37 and 0.13 min–1, respectively, from their corresponding reactive intermediates.

Synthesis, Characterization and Anti-Microbial Activity of Oxalate-Assisted CO3O4 Nanoparticles Derived from Homogeneous Co-Precipitation Method

Nano-sized cobalt oxide particles exhibit unique and fascinating physical, chemical and anti-microbial activity owing to their large surface to volume ratio. The study of metal oxide nanoparticles interaction with pathogenic microorganisms is great importance for various biomedical applications. The main purpose of this work is to study the anti-bacterial and anti-fungal behavior of cobalt oxide (CO3O4) nanoparticles against gram-positive and gram-negative bacterial strains and different fungi. The structure and morphology of CO3O4 nanoparticles were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and UV-Visible Spectroscopy, respectively. The CO3O4 nanoparticles showed a significant anti-bacterial activity against two gram-positive bacteria, Staphylococcusaureus (G[Formula: see text]), Streptococcus mutans (G[Formula: see text]), and two gram-negative bacteria, Klebsilla pneumonia (G[Formula: see text]), E. coli (G[Formula: see text]), and it shows a good anti-fungal activity against the two different fungal i.e., Aspergillus flavus (F) and Aspergillus niger (F), at different solvents. It was noted that synthesized CO3O4 nanoparticles exhibited the solvent-dependent anti-bacterial activity against all tested bacterial strains. CO3O4 NPs could be employed effectively for anti-microbial applications.

Electrochemical Preparation of Copper-Cobalt Oxide Nanosheets Array on Nickel Foam As the Catalyst for Oxygen Evolution Reaction

Development of sustainable energy has recalled highly efficient energy storage technology because it generates the electricity stochastically from the sources such as solar and wind. The water electrolysis has been considered as the one of the promising options to convert and store electrical energy as the form of hydrogen. However, relatively large overpotential from anodic half reaction, that is, oxygen evolution reaction (OER) has hindered commercial use of hydropower. The recent studies about OER have focused on finding out non-noble metal catalyst because the RuO2 and IrO2, ideal catalysts for OER, are scarce and expensive. Among the non-noble metal oxides, cobalt (III, IV) oxide has been received great attention since it is anticipated to be second best ideal catalyst for OER from theoretical calculations. With this respect, the number of nano-sized cobalt oxide electrodes with different morphologies have been prepared and utilized as the anode of electrolytic water splitting system. In this work, copper-cobalt oxides nanosheets catalyst layer was electrochemically prepared on the nickel foam substrate. To achieve nano-porous morphology of deposit, cobalt oxide was co-deposited with copper oxide. The structural and spectroscopic analyses revealed that cobalt-copper oxides nanosheet array consists of mixture of Co3O4 and CuxCo3-xO4. As the catalyst for OER, the resulting catalyst showed exceptional catalytic activity thanks to its nano- to micro-porous structure, which allows facile transport of active species. Furthermore, it showed great long-term stability. In this presentation, the catalytic activity of cobalt-copper oxides will be discussed in terms of electrochemical properties. In particular, several electrochemical parameters such as anodic Tafel slopes and overpotentials at different current densities will be suggested and compared to that of other nanostructured catalysts reported in literature. Furthermore, the effect co-deposition of copper and cobalt oxides on growth habit of overall deposit and its OER performance will be discussed.

Nanoheterogeneous Catalytic Cotransformation of Polyatomic Alcohols and Carbamides

The interaction of ethylene glycol and glycerol with carbamide in the presence of nanosized cobalt oxide obtained by the decomposition of cobalt(II) acetylacetonate in diphenyl ether is studied. The average size of the nanosized catalyst particles is 8–10 nm. The effect of nanoheterogeneous catalysis on the cyclocondensation of polyatomic alcohols with carbamide is investigated. A high capacity of the nanosized catalyst in this process is found 150 g(cyclic carbonate)/(g(catalyst) h), which is more than 100 times higher than the capacity of conventional catalysts.

분무열분해 공정에 의한 코발트 산화물 나노 분체 제조에 미치는 노즐 팁 크기의 영향

분무열분해 공정에 의한 코발트 산화물 나노 분체 제조에 미치는 노즐 팁 크기의 영향

Vpliv dodatka nanodelcev kobaltovega oksida na zgradbo in električne lastnosti NTC termistorjev na osnovi nikljevega manganita

Vpliv dodatka nanodelcev kobaltovega oksida na zgradbo in električne lastnosti NTC termistorjev na osnovi nikljevega manganita

Effect of Inflow Rate of Raw Material Solution on the Fabrication of Nano-Sized Cobalt Oxide Powder by Spray Pyrolysis Process

In order to identify changes in the nature of the particles due to changes in the inflow rate of the raw material solution, the present study was intended to prepare nano-sized cobalt oxide (Co3O4) powder with an average particle size of 50 nm or less by spray pyrolysis reaction using raw cobalt chloride solution. As the inflow rate of the raw material solution increased, droplets formed by the pyrolysis reaction showed more divided form and the particle size distribution was more uneven. As the inflow rate of the solution increased from 2 to 10 ml/min, the average particle size of the formed particles increased from about 25 nm to 40 nm, while the average particle size did not show significant changes when the inflow rate increased from 10 to 50 ml/min. XRD analysis showed that the intensity of the XRD peaks increased remarkably when the inflow rate of the solution increased from 2 to 10 ml/min. On the other hand, the peak intensity stayed almost constant when the inflow rate increased from 10 to 50 ml/min. With the increase in the inflow rate from 2 to 10 ml/min, the specific surface area of the particles decreased by approximately 20 %. On the contrary, the specific surface area stayed constant when the inflow rate increased from 10 to 50 ml/min.

CNT/Co3O4 Based Air Electrode Selectively Wrapped By Polyaniline for High Performance Air Electrode

Li-Air battery is one of the most promising new energy storage systems because they provide much higher energy densities than lithium-ion batteries. Nevertheless, Li-air batteries have several issues to be solved before the commercialization. One of them is side reaction attributed to the reaction between carbon, a general component of the air electrode, and electrolyte/Li2O2. Actually, carbon with high surface area provides a large reaction sites to form and store the reaction products. And it compensates for the low electronic conductivity of oxide catalysts such as MnO2 and Co3O4. However, some studies have suggested that the carbon promotes side reaction such as electrolyte decomposition and formation of Li2CO3. The unwanted reaction products formed from side reaction is hardly decomposed on charging process. This results in the accumulation of reaction products on the surface of electrode during cycling, which leads to limited cycle life and high over-potential. As a new approach to address these issues, nano-sized cobalt oxide (Co3O4) particles were composited with carbon nanotube (CNT) to enhance the catalytic activity, and the surface of carbon nanotube was selectively wrapped with polyaniline, a conducting polymer, to suppress the side reaction between carbon (CNT) and electrolyte/Li2O2. CNT/Co3O4 based air electrode selectively wrapped by polyaniline is expected enhanced cyclic performance and low over-potential due to synergic effect of nano-sized Co3O4 catalyst composited with CNT and polyaniline coating layer on the surface of carbon.

Thermolysis Synthesis of Pure Phase Nano-Sized Cobalt(II) Oxide from Novel Cobalt(II)-Pyrazole Discrete Nano Coordination Compound

Nano-structures of a new discrete coordination compound of divalent cobalt with the pyrazol (pzH) containing the terminal isothiocyanate anions, [Co(pzH)2(NCS)2] (1), with discrete molecular architecture in solid state was synthesized by a sonochemical method. The new nanostructure was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray powder diffraction, IR, and elemental analysis. The supramolecular features in these complexes are guided and controlled by weak directional intermolecular interactions. The discrete molecules interact with each other through labile interactions creating a 3D supramolecular framework. The CoO nanoparticles were obtained by thermolysis of 1 at 180 °C with oleic acid as a surfactant.

Cobalt oxide-carbon nanosheet nanoarchitecture as an anode for high-performance lithium-ion battery.

To improve the electrochemical performance of cobalt oxide owing to its inherent poor electrical conductivity and large volume expansion/contraction, Co3O4-carbon nanosheet hybrid nanoarchitectures were synthesized by a facile and scalable chemical process. However, it is still a challenge to control the size of Co3O4 particles down to ∼5 nm. Herein, we created nanosized cobalt oxide anchored 3D arrays of carbon nanosheets by the control of calcination condition. The uniformly dispersed Co3O4 nanocrystals on carbon nanosheets held a diameter down to ∼5 nm. When tested as anode materials for lithium-ion batteries, high lithium storage over 1200 mAh g(-1) is achieved, whereas high rate capability with capacity of about 390 mAh g(-1) at 10 A g(-1) is maintained through nanoscale diffusion distances and interconnected porous structure. After 500 cycles, the cobalt oxide-carbon nansheets hybrid display a reversible capacity of about 970 mAh g(-1) at 1 A g(-1). The synergistic effect between nanosized cobalt oxide and sheetlike interconnected carbon nanosheets lead to the greatly improved specific capacity and the initial Coulombic efficiency of the hybrids.

Effect of the Concentration of Cobalt Chloride Solution for the Preparation of Nano-Sized Cobalt Oxide Powder by Spray Pyrolysis Process

Effect of the Concentration of Cobalt Chloride Solution for the Preparation of Nano-Sized Cobalt Oxide Powder by Spray Pyrolysis Process

Application of Spray Pyrolysis Process for the Preparation of Nano Sized Cobalt Oxide Powder

In this study, nano-sized cobalt oxide powder with an average particle size below 50 nm was prepared from a cobalt chloride solution by the spray pyrolysis process. The influences of reaction temperature on the properties of the generated powder were examined. The average particle size of the particles formed based on the spray pyrolysis process at a reaction temperature of <TEX>$700^{\circ}C$</TEX> is roughly 20 nm. Moreover, most of these particles cannot appear with an independent type, thereby coexisting in a droplet type. When the reaction temperature increases to <TEX>$800^{\circ}C$</TEX>, the average particle size not only increases to roughly 40 nm but also shows a more dense structure while the ratio of particles which shows a polygonal form significantly increases. As the reaction temperature increases to <TEX>$900^{\circ}C$</TEX>, the distribution of the particles is from roughly 70 nm to 100 nm, while most of the particle surface is more intricately close and forms a polygonal shape. When the reaction temperature increases to <TEX>$1000^{\circ}C$</TEX>, the particle size distribution of the powder shows an existing form from 80 nm to at least 150 nm in an uneven form. As the reaction temperature increases, the XRD peak intensity gradually increases, yet the specific surface area gradually decreases.

Co3O4 doped over SBA 15: excellent adsorbent materials for the removal of methyleneblue dye Pollutant

Nanosized cobalt oxide particles are incorporated into SBA 15 mesoporous silica materials and are effectively used for the first time as adsorbent materials for aquatic dye pollutant removal. Cobalt is found to exist in its Co3O4 spinel structure as evident from FTIR and X-ray diffraction studies. The best weight ratio of metal loading to show excellent adsorption of methyleneblue is found to be 10 wt% Co over the support. There, Co3O4 spinel nanoparticles lie inside the pores of mesoporous silica. Further increase in the percentage of metal loading decreases the adsorption capacity which may be due to the agglomeration of nanoparticles over the silica support as evident from TEM photographs. Cobalt-doped systems of the present study, having good adsorption capacity of methyleneblue, are prepared via impregnation of cobalt nitrate over SBA 15 in aqueous medium. Here, we introduce a new SBA 15-based system for the fast removal of aquatic dye pollutants which is highly economical for industrial applications.

Surface-modified cobalt oxide nanoparticles: new opportunities for anti-cancer drug development.

The development of smart nanoparticles that can exhibit the anti-cancer activity, introduces better efficacy and lower toxicity for treatment. The present study was aimed to evaluate the anti-cancer activity of surface functionalized CoO nanoparticles against Jurkat (T-cell lymphoma) and KB (oral carcinoma) cell lines. The nano-sized cobalt oxide nanoparticles (CoO) was prepared by thermal decomposition method followed by surface modification using phosphonomethyl iminodiacetic acid (PMIDA). The PMIDA-coated CoO nanoparticle was characterized by X-ray diffraction, dynamic light scattering, and transmission electron microscopy; and the conjugation was analyzed by Fourier transform infrared spectroscopy. The resultant nanoparticles with an average size less than 100 nm measured by dynamic light scattering and transmission electron microscopy. Cytotoxicity study, flow cytometric analysis and scanning electron micrographs have been revealed that PMIDA-coated nanoparticles significantly enhances the cellular uptake of the nanoparticle and thus facilitates apoptosis of cancer cell (Jurkat and KB). For the application of PMIDA-coated CoO nanoparticles in the medical field, doxorubicin, a potent anti-cancer drug, has been used in similar fashion in this experimental design and all these effects or patterns were observed.

열분해 공정을 통해 합성된 산화 코발트 나노입자의 리튬 전기화학반응성

Nano-sized cobalt (II) oxide nanoparticles with a high crystallinity were synthesized using thermolysis of a Co 2+ -oleate precursor at 310℃. The phase and morphology of as-prepared cobalt oxide nanoparticles were characterized using X-ray diffraction, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller surface area measurements. The cobalt oxide nanoparticles were found to be spherical nanoclusters with an average diameter of approximately 200 nm, consisting of tiny nanocrystals (10-20 nm). Furthermore, the Li electroactivites of the cobalt oxide nanoparticles were investigated using cyclic voltammetry and galvanostatic cycling. The cobalt oxide nanoparticles could deliver high capacities over 420 mA h g -1 at a C/5 current rate.

Hydrothermal synthesis of cobalt carbonates using different counter ions: An efficient precursor to nano-sized cobalt oxide (Co 3O 4)

Synthesis of submicrometer crystalline particles of cobalt carbonate was achieved hydrothermally using different cobalt salts and urea with a molar ratio from 1:3 to 1:20 (cobalt salt:urea) in aqueous solutions at 160 °C for 24–36 h, in the presence of cetyltrimethylammonium bromide (CTAB) as a surfactant. Nanoparticles of Co 3O 4, with an average size from 30 to 39 nm, were obtained by thermal decomposition of CoCO 3 samples at 500 °C for 3 h in an electrical furnace. The as-synthesized products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–Vis spectra and thermal analysis. Studying the optical properties of the as-prepared cobalt oxide nanoparticles showed the presence of two band gaps, the values of which confirmed the semiconducting properties of the prepared Co 3O 4.

Preparation of supported nano-sized cobalt oxide and fcc cobalt crystallites

In order to study the role of the crystallite size of an active phase in a catalytic reaction it is of utmost importance to be able to synthesise pure phases of crystallites in the desired size range with a narrow size distribution. In this paper we describe a new method to produce Co 3O 4 crystallites in the nanometer size range (average sizes: 3–10 nm) utilising reverse micelles as nano reactors. To prepare suitable model catalysts for studies on effects of crystallite size these crystallites can be deposited onto a variety of carriers, in this work an alumina support was used. It is further shown that the supported cobalt oxide crystallites prepared in this study do not undergo extensive sintering under reductive conditions (H 2 flow and temperatures between 375 and 450 °C) so that also a series of model catalysts with metallic cobalt crystallites of varied size could be prepared. The resulting metal phase only shows the diffraction pattern of a face-centred cubic (fcc) crystal phase, while normally mixtures of fcc an hcp cobalt were obtained in previous studies. Furthermore, almost complete reduction of the catalyst could be obtained for all crystallite sizes and no Co-aluminate formation was observed. These model catalyst systems allow the study of structure sensitive reactions with an industrially relevant catalyst system in the absence of the commonly encountered difficulties like the formation of strong metal support interactions, co-existence of different metal crystallite phases, an incomplete reducibility and crystallite growth upon exposure to reduction/reaction conditions.

Nano-sized cobalt oxide/mesoporous carbon sphere composites as negative electrode material for lithium-ion batteries

Abstract A new type of nano-sized cobalt oxide compounded with mesoporous carbon spheres (MCS) as negative electrode material for lithium-ion batteries was synthesized. The composite containing about 20 wt.% cobalt oxide exhibits a reversible capacity of 703 mAh/g at a constant current density of 70 mA/g between 0.01 and 3.0 V (vs. Li+/Li), and remains a capacity retention of 77% after the 30th cycle. The improvement could be attributed to that the MCS had a good electronic conductivity and severed as dispersing medium to prevent cobalt oxide nanoparticles from aggregating, and the mesopores (cobalt oxide not fully occupied) can provide the enough space to buffer the volume change during the Li-ion insertion and extraction reactions in cobalt oxide nanoparticles.