Cobalt Oxide Research Articles

Synthesis of Cobalt Oxide Nanoparticles by Atmospheric Pressure Microplasma and Their Structural, Optical, Antifungal and Antibacterial Properties

Synthesis of Cobalt Oxide Nanoparticles by Atmospheric Pressure Microplasma and Their Structural, Optical, Antifungal and Antibacterial Properties

Integrating Pt-free dye-sensitized solar cell and symmetric supercapacitor employing common electrode quaternary nanocomposite

Energy demand is increasing day by day globally due to the increase of population in a drastic manner. Solar energy a renewable, abundant, eco-friendly energy is the best solution to meet the energy demand of the world. The dye-sensitized solar cells (DSSC) are the most reliable of the photovoltaics (PV) on account of their facile fabrication and pricing. Here a novel quaternary hybrid nanocomposite was substituted in the place of platinum (Pt) as a counter electrode and yielded exceptional results. The reduced graphene oxide/ manganese dioxide/ copper oxide/ cobalt oxide (rGO/MnO2/CuO/Co3O4 (RMCC)) was prepared and employed as a counter electrode of the DSSC under varied photoanodes (PA) like as-synthesized titanium dioxide (TiO2), zinc Oxide (ZnO) and titanium dioxide/zinc oxide TiO2/ZnO with N-719 as dye medium, all coated over Fluorine doped tin oxide (FTO) glass as substrate. The DSSC constructed with RMCC as counter electrode (CE) was discovered to have a reliable photoconversion efficiency of 7.67 % which is 98.83 % of the Platinum substituted DSSC. The result was also testified by developing 60 such devices in total, under different photoanode material and was proved to be consistent, enabling the nanocomposite to develop into a positive example for CE in DSSC. Later this DSSC was integrated with a symmetric supercapacitor made of the same electrode material and gave a photovoltage of 0.828 V with areal-specific capacitance, energy and power density of 264.73 mF cm−2, 25.208 μW h cm−2 and 0.1656 mW cm−2, respectively. The photo-supercapacitor device self-discharged at 548 s with an overall conversion efficiency of the photosupercapacitor is 8.98 % resulting in a self-charged energy device.

Ternary metal oxide carbon composite as high-performance electrode material for supercapacitor applications

Recently, ternary metal oxides carbon composites recognized as metal organic frameworks (MOFs) have gained striking attention for supercapacitor electrode material due to high surface area, porosity, chemical stability, tunable properties, redox activity, and eco-friendly material. ZIF-67 is a novel MOF possessing these characteristics. Therefore, the present work reports the development of ternary iron-nickel–cobalt ZIF-67 composites (FeNiCo ZIF-67) using co-precipitation method with the variation in molar concentration of iron oxide, nickel oxide, and cobalt oxide. Physico-chemical characterizations of developed materials were investigated through X-ray diffraction (XRD), Raman spectroscopy, energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) to confirm the successful formation of composites and structure, morphology. Then, the electrodes were fabricated for all three synthesized composites and electrochemical analyses such as cyclic voltammetry (CV), galvanic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed. The results revealed the porous polyhedral structure of FeNiCo ZIF-67 with different compositions consisting of interconnected nanoparticles played an important role in increasing the charge storage capacity of the material. Among the composites, FeNiCo ZIF-67 (1:2:1) electrode material achieved the highest specific capacitance of 532.7 F/g at a current density of 1 A/g. FeNiCo ZIF-67 (1:2:1) exhibited maximum electrochemical active surface area 89.12. Electrochemical impedance spectroscopy (EIS) demonstrated the minimal resistance of 7.8 Ω by FeNiCo ZIF-67 (1:2:1) composite electrode compared to the other two electrode materials. Cyclic stability study revealed the capacitance retention of 91 % after 10,000 continuous charge discharge cycles at a current density of 10 A/g. Electrode material demonstrated an outstanding electrochemical performance, and this work could provide a simple strategy to fabricate FeNiCo ZIF-67 nanostructured electrode materials for supercapacitors.

Manganese cobalt oxide-polythiophene composite for asymmetric supercapacitor

In this work, the synthesis of manganese cobalt oxide (MCO) and polythiophene (PTh) composite on Ni-foam is carried out using two step chemical methods. The MCO/PTh films are analyzed by various characterization techniques to study its structural, morphological and electrochemical aspects. The polycrystalline nature of MCO in MCO/PTh composite is confirmed from XRD analysis while presence of various functional groups in MCO/PTh is validated by FT-IR study. Oxidation state of manganese, cobalt and sulfur in the MCO/PTh composite are confirmed from EDAX and XPS analysis. The highest specific surface of the MCO/PTh sample is found about 63.3 m2/g from BET analysis. The deposition of fibrous polythiophene on the MCO nanoflakes is revealed by FE-SEM images while it is further validated by TEM analysis. The electrochemical characterizations of the MCO/PTh composite are carried out by different techniques. The specific capacitance of 1643.08F/g (6386.01 mF/cm2) at 20 mA/cm2 is showed by MCO/PTh electrode at optimized conditions. The electrochemical kinetics of the optimized sample is carried out to understand the charge storage dynamics for the MCO/PTh composite. The capacitance retention of 98 % is exhibited by MCO/PTh electrode after 5000 cycles. Additionally, the aqueous asymmetric supercapacitor, having 1.7 V potential window is tested. The device MCO/PTh//AC exhibited a specific capacitance of 133.47F/g with energy and power density of 53.5 Wh/kg, 13.3 kW/kg at 50 mA/cm2. The obtained results showed that utilization of this synergy of metal oxide with polymer composite can be a potential candidate for supercapacitors.

Unveiling the influence of open metal sites in quasi ZIF-67 for eco-friendly catalysis of solvent-free aldehyde cyanosilylation

Quasi metal–organic frameworks (Q-MOFs) containing a high density of open metal centers are considered as an effective method of expanding the effectiveness of defective MOF-based catalysts. To achieve this, quasi ZIF-67 (Q-ZIF-67), having large scale structural defects in the framework, is produced through partial deligandation of ZIF-67 under controlled thermal treatment at 310 °C in air. This generates many unsaturated cobalt centers as Lewis acid sites, and results in the coexistence of micro and meso-pores within the Q-ZIF-67 network. Subsequently Q-ZIF-67 was employed in the catalytic cyanosilylation of benzaldehyde with trimethylsilyl cyanide, resulting in the corresponding cyanohydrin within 30 min under solvent free-conditions in air at 40 °C and room temperature with TOF values of 1.62, 1.53 min−1, respectively. The related cyanohydrin product was identified via 1H NMR. Importantly, Q-ZIF-67 displayed a highly efficient heterogeneous Lewis acid catalyst for the cyanosilylation of benzaldehyde compared to the pristine ZIF-67 and related cobalt oxide. Furthermore, investigating the impact of the electron-donating and electron-withdrawing para-substitutions on benzaldehyde revealed that electron-withdrawing groups are suitable for nucleophilic reactions. It was also observed that there was no significant decrease in catalytic activity after five catalytic runs. Thus, the Q-ZIF-67 has considerable potential as environmentally friendly catalyst for wide range of practical application in aldehyde cyanosilylation reactions.

Effect of support on the catalytic performance of Au-Co3O4 catalysts: An operando DRIFTS-MS study of the propane total oxidation

This study investigates the effect of different supports on the catalytic performance of Au-Co3O4 nanoparticles in the total oxidation of propane, aiming to understand the interaction between the supported gold and cobalt oxide particles and the role of the support in enhancing the catalytic activity. Catalysts were prepared via the sequential deposition–precipitation with urea method, with TiO2 and Al2O3 as supports. We found that the AuCo3O4/TiO2 system exhibited higher catalytic activity and lower activation energy, compared to AuCo3O4/Al2O3. The enhanced performance of the AuCo3O4/TiO2 catalyst was attributed to the high mobility of surface oxygen species and the presence of oxygen vacancies. Operando DRIFTS-MS was used to characterize the intermediate species formed during the reaction. This technique revealed the presence of different intermediate species on the catalyst surfaces, with TiO2-supported catalysts showing enolate and carbonate adsorbed species at lower temperatures, enhancing the propane oxidation efficiency. In contrast, Al2O3-supported catalysts predominantly formed acetate adsorbed species at higher temperatures, indicating a less efficient oxidation process. The results demonstrated that the choice of support significantly affects the catalytic performance of Au-Co3O4 nanoparticles, with TiO2 providing superior oxyphility due to its reducibility and ability to promote the formation of active oxygen species. The study highlights the importance of the support material in the design of effective catalysts for volatile organic compounds (VOCs) oxidation.

Pt-Doped Co3O4 Nanowires as High-Efficiency Cathodic Catalysts for Improved Lithium-Oxygen Batteries and Insights into The Electrochemical Reaction Pathway

Lithium-oxygen batteries (LOBs) have garnered considerable interest as promising energy storage solutions owing to their exceptional theoretical energy density. Nevertheless, their practical implementation is impeded by notable obstacles, involving suboptimal energy efficiency, excessive overpotential and limited cycle life. Tricobalt tetra-oxide (Co3O4) is a promising cathodic bifunctional catalyst for LOBs. With deliberate alien-atom doping, their catalytic performance can even be further improved due to the resulted structural adjustment. In this work, platinum-doped cobalt oxide nanowires have been hydrothermally synthesized on the acid-treated carbon paper substrates. These nanowires, with a thickness of about 150 nm and a length of approximately 1.5 μm, are closely stacked and display an urchin-like morphology. As employed as the cathode for the LOBs, an excellent performance is delivered, including a discharge capacity of 17079.4 mAh g−1, an overpotential of 0.88 V, a cycle stability of over 75 cycles, and an initial coulombic efficiency of 95.71%, which is superior to the batteries based on pure Co3O4 nanowires. Combined with the results of density functional theory (DFT) calculations, it can be deduced from the experimental observation that the nanowires’ adsorption affinity toward the discharge/charge intermediates of lithium superoxide (LiO2), as well as the morphologies and formation/decomposition pathways of the discharge products, are all governed by Pt-doping. The Pt-doping-improved adsorption induces a transition of the discharge products from the solution-pathway grown flake-like morphologies which are randomly stacked in the voids between pure Co3O4 nanowires to the surface-pathway grown film-like morphologies which are tightly wrapped around the Pt-doped Co3O4 nanowires. The close contact between the film-like discharge products and the Pt-doped Co3O4 nanowires is facile for fast oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, hence the lowered overpotential and enlengthened cycle durability of the batteries. Furthermore, the increased amount of the film-like discharge products results in the enhancement of the capacity of the batteries. This work may shed light on approaches for boosting the electrochemical performance of the transition-metal-oxide-based LOBs through the strategy of alien-atom doping.

Lattice-Engineering modulated band structure facilitates enhanced stability of high-voltage LiCoO2 at 4.6 V

Lithium cobalt oxide (LCO) cathode materials could exceed 210 mAh g−1 with excellent volumetric energy density, when operated at voltages above 4.5 V. However, the progress in the advancement of high-voltage LCO cathodes is impeded by unstable lattice oxygen loss and rapid structural degradation. Herein, we propose a modification strategy to modulate the band structure and stabilize the crystal structure of LCO through Zr/Ti dual-doping. The modified Zr/Ti-LCO demonstrates stable cycling performance at elevated cut-off voltage of 4.6 V. Uniform co-doping with zirconium and titanium suppresses the severe H1-3/O1 deleterious phase transition of LCO. By fine-tuning TM-O interactions and modulated band structure mitigate oxygen release reactivity at high voltage, achieving a delicate balance between structural integrity and electrochemical stability. Consequently, the modified Zr/Ti-LCO half-cell achieves superb capacity retention of 87.7 % after 300 cycles at 3.0–4.6 V, while the Zr/Ti-LCO||graphite pouch full-cell retains up to 85.8 % capacity after 500 cycles at 3.0–4.5 V. This study offers critical perspectives for advancing the design of high-voltage LCO cathodes.

Rational design of cobalt oxide nanocubes arrays on Ni foam as durable and robust electrocatalyst for urea electro-oxidation

BackgroundCobalt oxide (Co3O4) is a promising electrocatalyst for efficient urea electro-oxidation, tackling power consumption and environmental challenges. The controllable design of free-standing Co3O4 nanostructures grown on Ni foam (NF) substrates was achieved using a green and facile hydrothermal approach. Different reducing agents were applied to synthesize various morphological structures of Co3O4, including nanoparticles, nanowires, and nanocubes (NCs) morphologies.ResultsThe as-fabricated electrodes were investigated as electrocatalysts for enhanced urea electro-oxidation. Because of its 3D nanostructure with minimal agglomeration and a large interfacial surface area with adequate electroactive sites, the Co3O4 NCs/NF had the best energy conversion efficiency of any electrode toward the urea oxidation process. These distinctive features facilitated the electron and urea routes used in the urea electro-oxidation process. It had a low-onset potential of 194.2 mV (vs. Hg/HgO) and a current density of 90.2 mA cm−2 in a 1 M KOH electrolyte. The electrocatalyst demonstrated excellent anodic activity for urea electro-oxidation with an onset potential of 196.7 mV and a current density of 256.1 mA cm−2 in 1 M KOH + 0.3 M urea concentration. Furthermore, the Co3O4 NCs/NF exhibited long-term stability, as shown by chronoamperometry and stepwise tests after 3600 s in the presence of urea under various operating conditions.ConclusionsCompared to all the fabricated Co3O4 nanostructures, the Co3O4 nanocubes revealed the highest electrocatalytic performance toward urea electro-oxidation in all concentrations. Therefore, Co3O4 NCs/NF is a promising, robust, and efficient electrocatalyst for direct urea fuel cell applications.

Evaluation of the electrical behavior of tungsten trioxide and cobalt oxide nanoparticles filled poly (ɛ-caprolactone) composite for optoelectronic devices

This study obtains the electrical characterization of nanocomposites comprising Poly(ɛ-caprolactone) (PCL), tungsten trioxide (WO3), and cobalt oxide (Co3O4) nanoparticles. The fabrication of these nanocomposites through a casting method aimed to enhance their electrical conductivity and dielectric properties. The AC conductivity (σac) was analyzed across varying frequencies, revealing a notable increase with the addition of Co3O4 nanoparticles, particularly up to the high content of Co3O4 nanoparticles. This enhancement is attributed to the formation of ion transport pathways and the increased amorphous regions within the PCL matrix. Dielectric properties were assessed through ε′ and ε'') measurements, which exhibited a decrease with increasing frequency, indicating the dielectric relaxation processes of the composite. The complex electric modulus analysis demonstrated a significant relationship between the real and imaginary components, suggesting potential ionic conductivity in the nanocomposites. Additionally, the Argand plot revealed a depressed semicircle, indicating a distribution of relaxation times, which further confirmed the enhancement of conductivity with raising laser ablation time. Overall, the results indicate that the addition of WO3 and Co3O4 nanoparticles significantly improves the electrical properties of PCL, making these nanocomposites suitable for various electrical applications.

Synthesis of Co3O4 Nanoparticles Using Ananas Comosus Peel Extract for Cr6+ Ion Adsorption and Antibacterial Applications

AbstractWater contamination, caused by both point and nonpoint sources, alongside the prevalence of diseases caused by bacteria, represents a significant global challenge. In this work, cobalt oxide nanoparticles (Co3O4 NPs) were synthesized using various volume ratios such as 1:1, 1:2, and 2:1 of cobalt nitrate hexahydrate as salt precursor solution and Ananas comosus peel extract. The synthesized NPs were used as a high surface area nanoadsorbent for removal of Cr6+ from aqueous solution and antibacterial activity against drug‐resistant bacterial strains applications. The TGA–DTA analysis confirms that Co3O4 NPs were thermally stable above 500 °C. The calculated average sizes were found to be 12.58, 13.40, and 22.05 nm for the 1:1, 1:2, and 2:1 ratios, respectively. The SEM–EDS analysis with TEM–HRTEM and SAED validated that Co3O4 NPs were spherical‐shaped without impurities. The band gap energy and the specific surface area of the 1:1, 1:2, and 2:1 Co3O4 NPs were calculated as 3.33, 2.95, and 2.70 eV and 24.7, 23.7, and 22.5 m2/g, respectively. Functional group analysis confirms the presence of numerous secondary metabolites within the peel extract. Cyclic voltammetry coupled with EIS proves the enhanced electrochemical properties of synthesized Co3O4. The Co3O4 (1:1) NPs exhibited higher adsorption efficiency (95%) toward Cr6+ removal and were found to be fit with pseudo‐second‐order kinetics and also with both the Langmuir and Freundlich adsorption isotherm. The maximum (13 mm) zone of inhibition was achieved against Staphylococcus aureus and Streptococcus pyogenes by Co3O4 (1:2) NPs.

Synthesis of urchin-like MnCo2O4 nanospheres as electrode material for supercapacitors

The morphology of MnCo2O4 has a significant effect on the electrochemical performance. In this paper, urchin-like MnCo2O4 nanospheres was successfully fabricated by a simple hydrothermal process and post-annealing treatment. The effects of addition of surfactant (Hexadecy ltrimethyl ammonium bromide) on the crystal structure, surface morphology and electrochemical performance of MnCo2O4 have been investigated. The results show that all the synthesized manganese cobalt oxides are composed of cubic spinel MnCo2O4. The addition of surfactant leads to the change of the morphology of MnCo2O4 from nanoarray to urchin-like nanospheres and increases the specific surface area, which is beneficial to improve the electrochemical performance of the MnCo2O4 electrode. The electrochemical test reveals that the urchin-like MnCo2O4 nanospheres delivered a high specific capacity of 2019 F/g at a 1 A/g and 1144 F/g at 5 A/g, respectively. The specific capacity of MnCo2O4 electrode reaches 512 F/g at 10 A/g and retains 96 % of the initial capacity after 2000 cycles at 10 A/g, which maintains an extraordinary cycling performance. In addition, an asymmetric supercapacitor (MnCo2O4//AC) with urchin-like MnCo2O4 nanospheres as a cathode and activated carbon (AC) as an anode was also assembled. Impressively, the assembled MnCo2O4//AC asymmetric supercapacitor exhibits a high energy density of 69 Wh/kg at a power density of 793 W/kg. The above research shows that the urchin-like MnCo2O4 nanospheres synthesized by adding surfactants are expected to be excellent high-performance energy storage electrode materials, which provides a new strategy for the synthesis of high-capacity nanoelectrode materials.

NdCoO3 nanoparticles grown on reduced graphene oxide sheets as an efficient electrocatalyst for hydrogen evolution reaction

To meet the huge energy crisis due to the limitation of fossil fuel, hydrogen has been considered the most promising clean energy source due to its high efficiency, non-toxic, and clean emission products. Therefore, over the past few years, researchers have been trying to find an effective route for bulk production of hydrogen energy from water splitting. Many efforts have already been made to use suitable electrocatalysts such as transition metal-based oxides, hydroxide alloys, and carbides for hydrogen production from water splitting but these electrocatalysts are hindered due to instability over prolonged usages in alkaline solution. To overcome this issue, rare-earth perovskite oxide materials are being focussed as an efficient electrocatalyst for electrocatalytic hydrogen evolution reaction (HER) through water splitting in an alkaline medium. In the present work, we have explored to synthesize the rare-earth perovskite neodymium cobalt oxide (NdCoO3) nanoparticles grown on reduced graphene oxide (rGO) sheet, via a hydrothermal route for electrochemical hydrogen evolution in an alkaline medium. The NdCoO3/rGO nanocomposite shows a remarkably low overpotential of 84mV at the desired current density of 10 mA/cm2, compared to pristine NdCoO3 and rGO. The synergistic impact between NdCoO3 and the rGO backbone, resulting in enhanced efficiency in the HER. The nanocomposite also shows high stability and durability even more than 100 h of electrolysis under an inert atmosphere.

Superionic conducting vacancy-rich β-Li3N electrolyte for stable cycling of all-solid-state lithium metal batteries.

The advancement of all-solid-state lithium metal batteries requires breakthroughs in solid-state electrolytes (SSEs) for the suppression of lithium dendrite growth at high current densities and high capacities (>3 mAh cm-2) and innovation of SSEs in terms of crystal structure, ionic conductivity and rigidness. Here we report a superionic conducting, highly lithium-compatible and air-stable vacancy-rich β-Li3N SSE. This vacancy-rich β-Li3N SSE shows a high ionic conductivity of 2.14 × 10-3 S cm-1 at 25 °C and surpasses almost all the reported nitride-based SSEs. A Li- and N-vacancy-mediated fast lithium-ion migration mechanism is unravelled regarding vacancy-triggered reduced activation energy and increased mobile lithium-ion population. All-solid-state lithium symmetric cells using vacancy-rich β-Li3N achieve breakthroughs in high critical current densities up to 45 mA cm-2 and high capacities up to 7.5 mAh cm-2, and ultra-stable lithium stripping and plating processes over 2,000 cycles. The high lithium compatibility mechanism of vacancy-rich β-Li3N is unveiled as intrinsic stability to lithium metal. In addition, β-Li3N possesses excellent air stability through the formation of protection surfaces. All-solid-state lithium metal batteries using the vacancy-rich β-Li3N as SSE interlayers and lithium cobalt oxide (LCO) and Ni-rich LiNi0.83Co0.11Mn0.06O2 (NCM83) cathodes exhibit excellent battery performance. Extremely stable cycling performance is demonstrated with high capacity retentions of 82.05% with 95.2 mAh g-1 over 5,000 cycles at 1.0 C for LCO and 92.5% with 153.6 mAh g-1 over 3,500 cycles at 1.0 C for NCM83. Utilizing the vacancy-rich β-Li3N SSE and NCM83 cathodes, the all-solid-state lithium metal batteries successfully accomplished mild rapid charge and discharge rates up to 5.0 C, retaining 60.47% of the capacity. Notably, these batteries exhibited a high areal capacity, registering approximately 5.0 mAh cm-2 for the compact pellet-type cells and around 2.2 mAh cm-2 for the all-solid-state lithium metal pouch cells.

Facile and ecofriendly green synthesis of Co3O4/MgO-SiO2 composites towards efficient asymmetric supercapacitor and oxygen evolution reaction applications.

The development of low-cost, eco-friendly, and earth-friendly electrode materials for energy storage and conversion applications is a highly desirable but challenging task for strengthening the existing renewable energy systems. As part of this study, orange peel extract was utilized to synthesize a magnesium oxide-silicon dioxide hybrid substrate system (MgO-SiO2) for coating cobalt oxide nanostructures (Co3O4) via hydrothermal methods. A variety of MgO-SiO2 compositions were used to produce Co3O4 nanostructures. The purpose of using MgO-SiO2 substrates was to increase the porosity of the final hybrid material and enhance its compatibility with the electrode material. This study investigated the morphology, chemical composition, optical properties, and functional group properties. In hybrid materials, the shape structure is inherited from nanoparticles with uniform size distributions that are well compacted. A relative decrease in the optical band was observed for Co3O4 when deposited onto an MgO-SiO2 substrate. An improvement in the electrochemical properties of Co3O4/MgO-SiO2 composites was observed during the measurements of supercapacitors and oxygen evolution reaction (OER) in alkaline solutions. The Co3O4/MgO-SiO2 composite prepared on 0.4 g of the MgO-SiO2 substrate (sample 2) demonstrated excellent specific capacitance, high energy density, and recycling stability for 40 000 galvanic charge-discharge cycles. The assembled asymmetric supercapacitor (ASC) device demonstrated a specific capacitance of 243.94 F g-1 at a current density of 2 A g-1. Co3O4/MgO-SiO2 composites were found to be highly active towards the OER in 1 M KOH aqueous solution with an overpotential of 340 mV at 10 mA cm-2 and a Tafel slope of 88 mV dc-1. It was found that the stability and durability were highly satisfactory. Based on the use of orange peel extract, a roadmap was developed for the synthesis of porous hybrid substrates for the development of efficient electrode materials for energy storage and conversion.

CHARACTERIZATION SUBSOLIDUS SYSTEM STRUCTURE CaO - Al2O3 - CoO – NiO

The paper presents the results of calculations characterizing the elements of the subsolidus structure of the CaO– Al2O3 – CoO – NiO system, which is promising for the production of modified aluminous cements and heterophase materials with a complex of unique properties. Insufficient information about the structure of the four-component phase diagram of a certain multicomponent system makes it difficult to obtain such materials. To predict the phase composition of materials, theoretical studies of the structure of the system were carried out. An analysis of the features of the coexistence of heterophase combinations was carried out, taking into account geometric-topological and statistical characteristics. The technological risks of predicting the phase composition of materials that arise in certain concentration regions of the system under study are shown. Calculations were carried out over the entire temperature range, both up to the melting point of the ternary oxide compound Ca3CoAl4O10 at 1439 K, and in a higher temperature region. Using known methods, the characteristics of eutectics in some sections of the system under study, which is of interest for the technological design of materials, were calculated. The results of calculations of the characteristics of eutectics show that among the analyzed tetrahedra, the minimum eutectic temperature (1367 K) is observed between the oxides of cobalt, nickel, calcium-cobalt aluminate and calcium monoaluminate, which can be realized for the synthesis of heterophase materials with a high content of Ca3CoAl4O10. Such materials have practical application in various industries: lime production; lime binders; corundum abrasives and refractories; high temperature catalysts; ceramics with special electromagnetic properties.

Fabrication of 4-methoxyphenol chemical sensor with graphene oxide conjugated binary Co3O4/Y2O3 nanocomposite by linear sweep voltammetry

Combining binary metal nanoparticles (MNPs) with two-dimensional materials can create innovative nanocomposites with unique physical and chemical properties, which are particularly useful for developing efficient electro-chemical sensing systems. This study presents a unique approach for detecting and validating the hazardous substance 4-Methoxyphenol (4-MP) electrochemical approach with conjugated nanocomposite (NC). This approach utilizes an electrochemical sensor constructed on a glassy carbon electrode (GCE), modified with hybrid composite material including graphene oxide (GO) conjugated binary yttrium oxide (Y2O3) and cobalt oxide (Co3O4) as GO@Co3O4/Y2O3 NCs. After preparing the NCs using the solid-state chemical method, various techniques were used to characterize the materials by using various techniques including Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Ultraviolet–Visible Spectroscopy (UV/Vis), Brunauer–Emmett–Teller Surface Area Analysis (BET), and Transmission Electron Microscopy (TEM). Cyclic voltammetry (CV), linear sweep voltammetry (LSV), and impedance spectroscopy (EIS) were used to examine the electrochemical characterization and sensing application of the fabricated electrodes. Under standard laboratory circumstances, we used LSV to measure the 4-MP detection limit, which linear dynamic range (LDR) from 0.67 to 2.08 M. Based on the calibration curve’s slope, the sensor’s sensitivity was found to be 2.9 µAµM−1cm−2. It was calculated the limit of quantification (LOQ) of 0.19 M and a lower limit of detection (LOD) of 0.057 M. Compared to other modified electrodes for 4-MP detection, the composite electrode demonstrated superior electrocatalytic performance. The GO@Co3O4/Y2O3 NCs sensor demonstrates excellent selectivity, even among several interfering substances and metal ions. For optimization, different phosphate buffered saline (PBS) solutions with pH values ranging from 5.7 to 8.0 were used to evaluate the sensor activity. The sensor’s effectiveness in detecting unknown 4-MP concentrations was tested in various real-samples, including seawater, industrial wastewater, tap water, and well water, using a standard addition method. This study introduces a new approach for developing an electrochemical sensor aimed at monitoring environmental chemicals. The sensor incorporates cobalt nanoparticles on carbon materials to introduce the inorganic-carbon composite materials for the safety in environmental and healthcare applications on a large scale.

Unravelling cobalt incorporation in Ca- and Sr-rich perovskites: How symmetry shapes the phases

The Ca-rich and Sr-rich stoichiometric and non-stoichiometric materials were obtained by the modified citrate method. After calcination at 900 °C, materials were characterized in terms of structure, microstructure and reducibility in an H2-containing atmosphere. The diffractometric data did not confirm the presence of Co-originated phases. Co K-edge and Ti K-edge were recorded and analyzed for a deeper description of the structural properties of materials, mainly the influence of non-stoichiometry on the effectiveness of Co incorporation into the perovskite systems. The X-ray absorption near edge structure study combined with temperature programmed reduction results indicated the presence of CoTiO3 and cobalt oxides phases for Ca-rich and Sr-rich. This approach also allowed to observe that non-stoichiometry in Sr-rich materials results in a lower amount of cobalt incorporated into the perovskite structure and a higher amount of Co3O4 formed. Additionally, for Ca-rich materials, XANES spectra indicated a higher amount of Co in the Ti sublattice and confirmed the higher Co2+/Co3+ ratio than in the case of Sr-rich materials.

Microwave-assisted synthesis of graphene oxide–cobalt ferrite magnetic nanocomposite for water remediation

Microwave-assisted synthesis of graphene oxide–cobalt ferrite magnetic nanocomposite for water remediation

Cyclooctatetrathiophene Based MOF-Derived Porous Materials as High-Performance Anode for Lithium-Ion Batteries

Extensive research on anodes with higher capacity than carbon-based materials is driven by the great demand for lithium-ion batteries with higher energy density. However, the cycling stability of high-capacity anodes is usually hindered by significant volumetric changes and structural collapse during the cycling process. Metal-organic frameworks (MOFs) are an emerging class of crystalline materials, and their derivatives are expected as alternative high-capacity anodes, resulting from the merits of easy functionalization and pore engineering. In this study, a novel porous Co-MOF-derived composite anode was prepared by the pyrolysis of a nonporous Co-cyclooctatetrathiophene tetrapyridine (Co-COTTTP) template. X-ray absorption spectroscopy and high-resolution transmission electron microscopy revealed that the precise composition of Co-COTTTP-derived composite anodes with exposed rich redox cobalt oxides active sites, appropriate degree of graphitization, and N, S-doping, which effectively enhanced the electrochemical performance of the composite anodes. Thus, the resulting porous MOF-derived composite anode demonstrated high specific capacity and long cycling stability in the assembled batteries. Specifically, the cells assembled with Co-COTTTP-500 anodes delivered a high reversible specific capacity of 1005.7 mAh/g after 100 cycles at 0.1 A/g and can be cycled steady for 800 cycles at 1 A/g, indicating the structure stability during cell operation. In summary, this study provides a feasible strategy to prepare high-performance MOF-derived anodes and deep understanding for the structure–activity relationship, contributing to the fabrication of high-energy–density lithium-ion batteries.