Co3O4 Powders Research Articles

Facile Synthesis and Li-Electroactivity of Cobalt Oxide Based on Resources Recovered from Waste Lithium-Ion Batteries

In this study, cobalt oxide (Co3O4) powder was prepared by simple precipitation and heat-treatment process of cobalt sulfate that is recovered from waste lithium-ion batteries (LIBs), and the effect of heat-treatment on surface properties of as-synthesized Co(OH)2 powder was systematically investigated. With different heat-treatment conditions, a phase of Co(OH)2 is transformed into CoOOH and Co3O4. The result showed that the porous and large BET surface area (ca. 116 m2/g) of Co3O4 powder was prepared at 200°C for 12 h. In addition, the lithium electroactivity of Co3O4 powder was investigated. When evaluated as an anode material for LIB, it exhibited good electrochemical performance with a specific capacity of about 500 mAh g–1 at a current density of C/5 after 50 cycles, which indicates better than those of commercial graphite anode material.

Sensitivity Enhancement of CO2 Sensors at Room Temperature Based on the CZO Nanorod Architecture.

Cobalt-doped ZnO (CZO) thin films were deposited on glass substrates at room temperature by radio frequency (RF) magnetron sputtering of a single target prepared with ZnO and Co3O4 powders. Changes in the crystallinity, morphology, optical properties, and chemical composition of the CZO thin films were investigated at various sputtering powers of 45, 60, and 75 W. All samples presented a hexagonal wurtzite-type structure with a preferential c-axis at the (002) plane, along with a distinct change in the strain values through X-ray diffraction patterns. Scanning electron and atomic force microscopy revealed uniform and dense deposition of nanorod CZO samples with a high surface roughness (RMS). The Hall mobility and carrier concentration increased with the introduction of Co+ ions into the ZnO matrix, as seen from the Hall effect study. The gradual increase of the power applied on the target source significantly affected the morphology of the CZO thin film, which is reflected in the CO2-sensing performance. The best gas response to CO2 was recorded for CZO-60 W with a response of 1.45 for 500 ppm CO2, and the response/recovery times were 72 and 35 s, respectively. The distinguishing feature of the CZO sensor is its ability to effectively and rapidly detect the CO2 target gas at room temperature (∼27 °C, RT).

Recovery of cobalt based materials from spent Li-ion batteries and their use as electrode material for supercapacitor

In this work, Co(OH)2 and Co3O4 were obtained to be used in coin cell-type supercapacitors from a lithium-ion battery whose cathode material is LiCoO2 for the first time in the literature. Firstly, LiCoO2 cathode material was taken from the dismantled li-ion battery, and leaching of cathode material was carried out using HNO3 and H2O2. Leaching was performed with a maximum yield of approximately 94 %. Then Co(OH)2 was precipitated in a basic medium by using a NaOH solution. Thermal analysis was applied to the produced Co(OH)2 to determine the behavior for conversion from Co(OH)2 to Co3O4. Two different Co3O4 powders were obtained as Co3O4-450 and Co3O4-1000 by calcination of precipitated Co(OH)2 at 450 and 1000 °C. Produced powders were characterized by lots of characterization methods such as XRD, Raman, SEM and BET. Three different electrode material for the coin cell type asymmetric supercapacitor cathode was made from produced powders by mixing with carbon black and PVDF. GCD, CV and EIS measurements were used evaluate the electrochemical properties of the supercapacitors. The maximum areal capacitance value of 98 mF.cm−2 was obtained at 10 mV/s scan rate in Co3O4-450 based supercapacitor.

Reduction Kinetics of Co3O4 Powders by Hydrogen Plasma and Hydrogen Gas at Low Temperatures

Reduction Kinetics of Co3O4 Powders by Hydrogen Plasma and Hydrogen Gas at Low Temperatures

Bendable & twistable oxide-polymer based hybrid electrochromic device: Flexible and multi-wavelength color modulation

Flexible electrochromic (EC) technology has made huge progress in electronic industry for their applications in flexible displays, e-papers, e-curtains etc. The performance of device is the main concern while fabricating a flexible electrochromic device. In this paper, a solid state flexible electrochromic device (flex-ECD) has been demonstrated by combining the excellent EC performance of organic polymer and excellent stability of metal oxides which exhibits fast color switching and excellent stability after bending and twisting it for several times. For the fabrication of device, first Co3O4 and WO3 powders have been synthesised and utilised as dopants in the two electrochromic active materials namely polythiophene (P3HT) and ethyl viologen (EV), respectively. Due to the doping of these nanomaterials the performance of the flex-ECD has been enhanced as measured in terms of coloration efficiency, switching time and stability. Additionally, the device shows color switching in their different wavelength regions between visible and NIR. The flex-ECD shows high stability with a few seconds of switching time and high coloration efficiency of 420 cm2/C. The device was first bent and subsequently twisted for several more times. After bending, the performance has been checked, exhibiting minimal change in switching time at 515 nm and 665 nm without compromising the coloration efficiency much. The device shows excellent stability after bending and twisting moments making it a good design for future wearable electronics.

Effect of Co3O4 powder on the explosion characteristics and CO products of methane-air mixture

Rapid removing toxic CO for methane-air mixture explosions is essential in reducing casualties, but relevant research is rare. This paper proposed a novel approach for efficient CO removal and explosion suppression for methane-air mixture explosions using Co3O4 powder. The effect of Co3O4 powder on the explosion characteristics and basic parameters to quantify the CO removal performance have been studied, mainly including maximum explosion pressure (Pm), combustion time (tc), flame propagation velocity, and average CO removal rate (Rave.). Results indicated that explosion intensity and CO concentration decreased significantly with Co3O4 powder, due to increased heat absorption capacity and the active site of CO catalytic oxidation. However, the average CO removal rate decreased as the Co3O4 powder usage and CH4 partial pressure increased, which could reduce the dispersion degree of the Co3O4 dust cloud. The CO removal was achieved through the CH4 catalytic combustion and CO catalytic oxidation, which could reduce the CO generation and oxidize the generated CO to harmless CO2, respectively. This work provides a novel routine to lessen the explosion hazards and has promising applications in emergency rescue.

Disentangling Local Interfacial Confinement and Remote Spillover Effects in Oxide-Oxide Interactions.

Supported oxides are widely used in many important catalytic reactions, in which the interaction between the oxide catalyst and oxide support is critical but still remains elusive. Here, we construct a chemically bonded oxide-oxide interface by chemical deposition of Co3O4 onto ZnO powder (Co3O4/ZnO), in which complete reduction of Co3O4 to Co0 has been strongly impeded. It was revealed that the local interfacial confinement effect between Co oxide and the ZnO support helps to maintain a metastable CoOx state in CO2 hydrogenation reaction, producing 93% CO. In contrast, a physically contacted oxide-oxide interface was formed by mechanically mixing Co3O4 and ZnO powders (Co3O4-ZnO), in which reduction of Co3O4 to Co0 was significantly promoted, demonstrating a quick increase of CO2 conversion to 45% and a high selectivity toward CH4 (92%) in the CO2 hydrogenation reaction. This interface effect is ascribed to unusual remote spillover of dissociated hydrogen species from ZnO nanoparticles to the neighboring Co oxide nanoparticles. This work clearly illustrates the equally important but opposite local and remote effects at the oxide-oxide interfaces. The distinct oxide-oxide interactions contribute to many diverse interface phenomena in oxide-oxide catalytic systems.

Thermal atomic layer etching of CoO using acetylacetone and ozone: Evidence for changes in oxidation state and crystal structure during sequential exposures

Thermal atomic layer etching (ALE) of CoO was demonstrated using sequential exposures of acetylacetone (Hacac) and ozone (O3). During the surface reactions, Hacac can remove CoO according to: CoO + 2Hacac → Co(acac)2 + H2O. Ozone was employed to eliminate carbon residue resulting from Hacac adsorption. In situ spectroscopic ellipsometry observed a linear decrease in CoO film thickness versus Hacac and O3 exposures with an etch rate of 0.43 Å/cycle at 250 °C. The surface of the CoO film was also observed to undergo changes in oxidation state and crystal structure with each reactant exposure. Ex situ grazing incidence X-ray diffraction (GIXRD) studies revealed that the initial h-CoO thin films were oxidized to c-Co3O4 by O3. Subsequently, the GIXRD analysis showed that the c-Co3O4 thin films were reduced to c-CoO by Hacac. X-ray photoelectron spectroscopy investigations confirmed the oxidation state of the various cobalt oxides. Quadrupole mass spectrometry measurements observed Co(acac)2 etch products during Hacac exposures on Co3O4 and CoO powder. Atomic force microscopy measurements also monitored a reduction in surface roughness during CoO ALE. These studies reveal that alternating changes in oxidation state and crystal structure occur during the sequential Hacac and O3 exposures that define CoO thermal ALE.

Modification of calcium orthovanadate single crystal due to cobalt doping

Activation of calcium orthovanadate crystals by cobalt ions was carried out by introducing cobalt oxide into the melt during Czochralski growth process or during high-temperature annealing of nominally pure Ca3(VO4)2 single-crystal using Co3O4 powder as a solid-phase diffusant. The maximum concentration of the Co ions in the matrix is achieved in the case of the diffusion doping process. For the concentration series of Ca3(VO4)2:nCo crystals, the local structure was investigated and the crystal chemical composition was determined. Polarized absorption spectra of doped crystals are obtained. The influence of the atmosphere and the annealing temperature on the redistribution of the intensities of the characteristic absorption bands in the visible and near-IR spectral regions is shown. Luminescence parameters of the doped crystals were studied.

Green synthesis of Co3O4 nanoparticles using psyllium husk (Plantago Ovata) and application as electrocatalyst for oxygen evolution reaction

The continuous supply of hydrogen from renewable sources through water electrolysis technology is a key issue for the development of humanity. To meet this purpose, catalysts based on transition metals (Ni, Fe and Co) are promising candidates for the hydrogen and oxygen evolution reactions. Therefore, in this work, nanocrystalline Co3O4 with a spinel-like cubic structure was prepared by a proteic sol–gel synthesis using psyllium husk as a polymerizing agent, and later tested as an electrocatalyst for the oxygen evolution reaction (OER). The purity of the Co3O4 phase was confirmed by several characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The size of crystallites and particles obtained from Rietveld refinement of X-ray diffraction patterns ranged from 16.5 nm to 25.3 nm for powders calcinated at 400 °C and 600 °C, respectively, confirming nanometric Co3O4 powders. Scanning electron microscopy shows nanostructures with predominantly spherical morphology. From the electrocatalytic point of view, it was observed that the larger particle size impairs the oxygen evolution reaction. The Co3O4 calcined at 400 °C showed superior electrocatalytic performance, with an overpotential of 328 mV at 10 mA cm−2, Tafel slope of 71 mV dec-1, CDL of 5.46 mF cm−2, ECSA of 91 cm2, specific activity of 4.73 mA cm−2 and mass activity of 718 A g−1.

The effects of sintering atmospheres on piezoelectric performances of Co‐doped Ba0.88Ca0.12Zr0.12Ti0.88O3 ceramics

AbstractThis work investigates the effects of content ratio Co3+/Co2+ on piezoelectric properties of lead‐free Ba0.88Ca0.12Zr0.12Ti0.88O3 (BCZT) ceramics. For this purpose, 0.10 wt% Co ions using a CoO powder doped BCZT ceramics were sintered under various atmospheres (ranging from pure nitrogen to 100 vol% oxygen concentration) to vary the ratio value Co3+/Co2+. X‐ray photoelectron spectroscopy analysis revealed the coexistence of Co3+ and Co2+ for oxygen concentration below 40 vol% and the single oxidation state of Co3+ for oxygen concentration over 50 vol%. Co2+ substitution could induce more oxygen vacancy to accelerate densification and grain growth, whereas Co3+ substitution usually leads to larger lattice distortion to generate a stable asymmetric structure. When oxygen concentration was 30 vol% and Co3+/Co2+ near to 1.0, the respective superiority of Co3+ and Co2+ is brought into full play, and the ceramic showed the highest piezoelectric constant d33* ∼ 518 pm/V (380 pm/V for undoped BCZT) and the relatively high Curie temperature Tc ∼ 105°C (95°C for undoped BCZT). This study suggests that optimizing sintering atmosphere might be an effective way to enhance the piezoelectric properties for some composition‐modified piezoelectric BCZT ceramics.

Study on the Formation of (Co,Ni)O Solid Solution and Metallic Ni Phases During Suspension Plasma Spraying of CoO and NiO Powders

Study on the Formation of (Co,Ni)O Solid Solution and Metallic Ni Phases During Suspension Plasma Spraying of CoO and NiO Powders

Co3O4 Nanopetals Grown on the Porous CuO Network for the Photocatalytic Degradation.

Designing a novel photocatalytic composite for the efficient degradation of organic dyes remains a serious challenge. Herein, the multi-layered Co3O4@NP-CuO photocatalyst with unique features, i.e., the self-supporting, hierarchical porous network as well as the construction of heterojunction between Co3O4 and CuO, are synthesized by dealloying-electrodeposition and subsequent thermal treatment techniques. It is found that the interwoven ultrathin Co3O4 nanopetals evenly grow on the nanoporous CuO network (Co3O4@NP-CuO). The three-dimensional (3D) hierarchical porous structure for the catalyst provides more surface area to act as active sites and facilitates the absorption of visible light in the photodegradation reaction. Compared with the commercial CuO and Co3O4 powders, the newly designed Co3O4@NP-CuO composite exhibits superior photodegradation performance for RhB. The enhanced performance is mainly due to the construction of heterojunction of Co3O4/CuO, greatly promoting the efficient carrier separation for photocatalysis. Furthermore, the possible photocatalytic mechanism is analyzed in detail. This work provides a promising strategy for the fabrication of a new controllable heterojunction to improve photocatalytic activity.

Photocatalytic degradation of methyl orange in the presence of transition metals (Mn, Ni, Co) modified TiO2 coatings formed by plasma electrolytic oxidation

The effect of selected transition metals (Mn, Ni, Co) modified TiO2 coatings formed by plasma electrolytic oxidation of titanium on their surface morphology, phase and chemical composition, optical absorption, and photocatalytic degradation of methyl orange (MO) was investigated. Coatings were formed in an alkaline electrolyte with varying concentrations of MnO, NiO, or Co3O4 powders. The morphology, thickness and phase structure of all formed coatings are nearly identical and independent of the content of transition metal ions embedded in TiO2. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that anatase TiO2 coatings were loaded with MnO, NiO, or Co3O4 from electrolytes. When up to 2.0 g/L of MnO, NiO, or Co3O4 is added to the electrolyte, the photocatalytic activity (PA) of the forming coatings is higher than for pure TiO2. The coatings formed in electrolyte with the addition of 0.75 g/L MnO, 1.5 g/L NiO, or 2.0 g/L Co3O4 had the highest PA. Increased PA is associated with a decrease in photogenerated electron/hole recombination rate, according to UV–Vis diffuse reflectance spectroscopy and photoluminescence measurements.

A Friendly Environmental Route for the Fabrication of Spinel Co3O4 Nanorods, Using Inorganic Precursor Salt and Aqueous Extracts of Moringa oleifera Leaves

Nowadays many researchers are focused on the sytnhesis of nanoscale tricobalt tetraoxide (Co3O4) particles, owing to their unique properties. These particles have indeed many potential technological applications. The present investigation deals with the fabrication of this spinel oxide: it was successfully synthesized through a friendly environmental method, using cobalt (II) chloride as cobalt precursor and aqueous extract of Moringa oleifera leaves. The latter contains alkaloids as a base source while flavonoids present in the leaves acted as capping agent to prevent the particles agglomeration. Alkaloids present in the leaves were hydrolyzed in water and consequently, hydroxilated Co2+ leads to the formation of Co3O4 powder via calcination. The electronic transmission microscopy has revealed the single crystalline nanorods morphology of the synthetised materials. These nanorods are about several hundred nanometers long and several tens of nanometers in diameter. The bulk Co3O4 is known to be antiferromagnetic, the vibrating sample magnetometer data (at room temperature) of the prepared powder exhibited the lower coercivity and remanence, signaling that the produced spinel was pure and was constituted of superparamagnetic particles made of Co3O4. The UV–visible spectrum exhibited a photoluminescence peak in the visible light range positioned at about 538nm, suggesting this spinel as a visible light emitting material and as photocatalyst under visible light.

Sensing of oxidizing and reducing gases by sensors prepared using nanoscale Co3O4 powders: A study through Cu substitution

We demonstrate the sensing-mechanism of both oxidising and reducing gases by nanoscale Co3O4 powders through a strategy of Cu-doping in Co3O4. The sensitivity towards both types of gases arises due to presence of Co2+ and Co3+ cations in the (nearly) normal spinel structure of Co3O4. Pellets made up of nanopowders were employed for the detection of ∼6.5 ppm CO gas present in either pure N2 or in a mixture of synthetic air as carrier gas (which represents the O2 sensing-gas too). The high sensitivity of Co3O4 nanoparticles to detect ∼6 ppm CO (in N2) arises due to the high surface area of nanopowders exposing a higher number of octahedral Co3+ cations as adsorption sites, whereas the sensitivity towards O2 arises due to partial presence (less number) of octahedral Co2+. To support this mechanism, octahedrally Cu2+ substituted Co3O4 specimens are investigated. The inactive Cu2+ at the octahedral site changes the unexposed tetrahedral Co2+ into Co3+. The presence of inactive Cu2+ at the octahedral site and the burial of the Co3+ at the tetrahedral sites reduce the adsorption sites for O2, thereby drastically reducing the overall O2-gas sensitivity shown by the Cu-substituted sample, although they have higher surface-area (nanoparticles).

A simple process to resynthesize the LiCoO2 and LiNi1/3Co1/3Mn1/3O2 compounds from the cathode material extracted from a batch of spent LCO batteries

A low-cost and straightforward resynthesis process based on the complete thermal decomposition of the cathode material extracted from a batch of discarded LiCoO2 (LCO) batteries is described. After leaching the thermally decomposed products, the residue and the filtered solution were employed as feedstock for the resyntheses. The Co3O4 powder residue, filtered from the leached solution, and commercial Li2CO3 were employed to resynthesize the LiCoO2 compound by solid-state reaction. The filtered leached solution containing Li+ and Co2+ ions was used to resynthesize the LiCoO2 and LiNi1/3Co1/3Mn1/3O2 compounds by the sol-gel technique. In these resyntheses, commercial Li, Ni, and Mn acetates were used for compositional adjustments. The charge capacity of electrodes manufactured with the resynthesized compounds was measured by charge and discharge curves in a Li-metal oxide/LiClO4-EC:DMC/Li° electrochemical cell.

Effect of Cobalt Oxides on the Catalytic Combustion of Odor.

The catalytic combustion of acetaldehyde was studied using various types of Co oxides and Co-PC. The Co oxides and Co-PC were characterized using an X-ray diffractometer (XRD), X-ray photo-electron spectroscopy (XPS), and a particle sizing analyzer. The Co-PC and CoO were converted into Co₃O₄ under an air atmosphere at 450 °C, and the results were confirmed using the XRD and XPS. According to the pretreatment of the Co-PC and Co oxides, the conversion of acetaldehyde increased. The order of particle size for both fresh and pretreated samples is summarized as follows: CoO < Co-PC < Co3O4 powder < Co₃O₄ (99.995%). For all samples, acetaldehyde was not observed at temperatures above 320 °C owing to complete combustion. The conversion of acetaldehyde in the samples was affected by the fresh state of the Co oxides and the space velocity. The catalytic activity depended on the chemical state of the Co oxides and the surface concentrations of Co, O, and N.

Synthesis and characterization of Co3O4 nanoparticles for use as pigments in solar absorbing paints

This aim of this research is to produce Co3O4 oxide by means of one-step solution novel combustion methods using aspatic acid (C4H7NO4); lysine (C6H14N2O2); tris (hydroximethyl) aminomethane (NH2C (CH2OH)3) and ethylene diamine tetra-acetic acid (C10H16N2O8) as fuels. The pigments were characterized using X-ray diffraction, scanning and transmission electron microscopy, infrared spectroscopy with Fourier transform and UV-VIS-IR Spectrophotometry. The paint based on alkyd resin was made from pigments obtained (Co3O4 oxide). In order to make a comparison of the thermal emittance of the paint, two different formulations were prepared and these coating are named "absorbent paint coating": one that included 1% by weight of aluminum in metallic powder and another, with 1% of copper in metallic powder, respectively. The solar absorbance for the Co3O4 powders, plus quartz cuvette, gave a value of 0.9 in all cases. An extraordinary value of absorption on the coatings between 95 and 96% was noted. These results suggested that the synthesis of combustion in solution makes it possible to obtain a Co3O4 absorbent pigment with different fuels. These syntheses have a low environmental impact because they are one-step processes. All use low amounts of reactive ash obtained at a calcination of about 500 °C. These results suggest the possibility of utilizing this oxide in absorbent solar paints.

Solution combustion synthesis of a nanometer-scale Co3O4 anode material for Li-ion batteries.

A novel solution combustion synthesis of nanoscale spinel-structured Co3O4 powder was proposed in this work. The obtained material was composed of loosely arranged nanoparticles whose average diameter was about 36 nm. The as-prepared cobalt oxide powder was also tested as the anode material for Li-ion batteries and revealed specific capacities of 1060 and 533 mAh·g−1 after 100 cycles at charge–discharge current densities of 100 and 500 mA·g−1, respectively. Moreover, electrochemical measurements indicate that even though the synthesized nanomaterial possesses a low active surface area, it exhibits a relatively high specific capacity measured at 100 mA·g−1 after 100 cycles and a quite good rate capability at current densities between 50 and 5000 mA·g−1.