Pure Co3O4 Nanoparticles Research Articles

Effect of Ce-doping on the structural, morphological, and electrochemical features of Co3O4 nanoparticles synthesized by solution combustion method for battery-type supercapacitors

This study investigates the potential of cerium (Ce) doping to improve the performance of cobalt oxide (Co₃O₄) nanoparticles as battery-type supercapacitor electrodes. Pure Co₃O₄ nanoparticles were synthesized via a solution combustion method and then doped with 2.5 % (Ce-Co3O4) and 5 % Ce (CeO2-Co3O4). Comprehensive characterization, including X-ray diffraction (XRD), Raman spectroscopy, and field emission scanning electron microscopy (FESEM), was used to analyze the impact of Ce doping on the material properties. XRD analysis confirmed the successful incorporation of Ce into the Co₃O₄ structure, with distinct CeO2 phases forming at higher doping levels. Ce doping resulted in decreased crystallite size and peak intensity, indicating reduced crystallinity and increased defect concentration. Raman spectroscopy corroborated these findings, showing a redshift that suggests weakened metal-oxygen bonds and smaller grain sizes due to Ce³⁺ incorporation. FESEM images demonstrated that Ce doping effectively reduced nanoparticle agglomeration, with 2.5 % doping leading to smaller particles and 5 % doping promoting a 2D flake-like morphology with increased porosity. Nitrogen adsorption-desorption measurements revealed a significant increase in surface area and pore volume for CeO2-Co₃O₄, facilitating improved electrolyte diffusion and reduced resistance, thereby enhancing electrochemical performance. Evaluation of the electrochemical properties of undoped and Ce-doped Co₃O₄ materials revealed a battery-like response in a three-electrode configuration. Notably, the CeO2-Co3O4 exhibited a superior specific capacity of 603.3 C g−1 at a current density of 1 A g−1, significantly exceeding the values of 368.5 C g−1 and 127.1 C g−1 achieved by Ce-Co3O4 and undoped Co3O4, respectively. Furthermore, the CeO2-doped Co3O4 demonstrated exceptional cyclic stability, retaining 87 % of its initial capacity after undergoing 5000 charge-discharge cycles at a high current density of 10 A g−1. These results suggest that Ce doping is a promising strategy for optimizing Co₃O₄-based battery-type electrode materials, potentially leading to the development of high-performance and cost-effective energy storage systems.

Preparation and characterization of carbon quantum dots grafted Co3O4 nanocomposite for supercapacitors application

A pure Co3O4 nanoparticles and a carbon quantum dots (CQDs) anchored cobalt oxide (Co3O4/CQD) nanocomposite were synthesized by a simple hydrothermal method for supercapacitor application. The powder XRD measurement confirms the formation cubic phase of Co3O4. More HR-TEM measurements. The beneficial surface and electronic properties of CQDs were used for the refinement of the electrochemical accomplishments of Co3O4. The Co3O4/CQD and Co3O4 manifest half-cell specific capacitances of 193.8 F g−1 and 123.6 F g−1 @ current density of 4 A g−1, respectively. The introduction of CQDs into the Co3O4 matrix increased the charge-transfer process, which is primarily responsible for the improved electrochemical capabilities of the nanocomposite. The hybrid asymmetric supercapacitor delivers an energy density of 2.49 W h kg−1 @ a power density of 426 W kg−2 with a capacitance retention of 81.8%.

Investigation on the substituent effects of homodinuclear cobalt(II) complexes of tetraiminediphenol macrocycle on the synthesis of pure Co3O4 nanoparticles

Investigation on the substituent effects of homodinuclear cobalt(II) complexes of tetraiminediphenol macrocycle on the synthesis of pure Co3O4 nanoparticles

Mesoporous SiO2‐Encapsulated Nano‐Co3O4 Catalyst for Efficient CO Oxidation

AbstractTo meet the increasing demand for efficient and durable catalysts for exhaust aftertreatment system, a mesoporous SiO2‐encapsulated nano‐Co3O4 catalyst was synthesized, which possesses a unique pitaya‐like structure with high CO oxidation activity and thermal stability. Though the silica matrix is inert, the encapsulated Co3O4 exhibits increased oxygen storage capacity, enhanced CO2 desorption behavior and high lattice oxygen reactivity. Additionally, the SiO2‐encapsulated Co3O4 catalyst can be effectively regenerated rather than the supported Co3O4/SiO2 and pure Co3O4. The kinetic results demonstrate that the L−H mechanism is followed over the pure Co3O4 nanoparticles catalyst, while the CO oxidation over the silica‐supported Co3O4 catalysts obey to both L−H and MVK mechanism. The encapsulation structure of the as‐prepared catalyst can effectively restrain the aggregation of Co3O4 during high temperature operations and improves the utilization efficiency of cobalt resources, as well, which would be suitable for practical applications.

Silica‐Templated Metal Organic Framework‐Derived Hierarchically Porous Cobalt Oxide in Nitrogen‐Doped Carbon Nanomaterials for Electrochemical Glucose Sensing

AbstractAs glucose molecules are well recognized to supplement the main energy source of living cells as the intermediate product of metabolism in human body, it is of great importance to develop a convenient and quantitative glucose sensor with high selectivity, high sensitivity, and high accuracy. In this work, a simple and novel strategy has been developed to obtain a high‐performance non‐enzymatic glucose sensor by constructing hierarchically porous Co3O4 embedded into the metal organic framework (MOF)‐derived N‐doped carbon matrix based on a SiO2 template, denoted as ST‐Co3O4. The removal of the SiO2 template creates abundant voids and a large specific surface for the obtained layered mesoporous ST‐Co3O4 composite, which enhances the electron transfer kinetics and the ability to adsorb biomolecules, further greatly improving the surface reaction efficiency and promoting the improvement of its catalytic performance. Compared with pure Co3O4 nanoparticles from ZIF‐67 without a silica template, as‐obtained ST‐Co3O4 shows a good mesoporous environment, provides more active sites, and makes the non‐enzymatic glucose sensor exhibit high sensitivity (2860 μA mM−1 cm−2) and fast response time (<1 s) over a wide linear glucose concentration range of 1.0–1300.0 μM. Additionally, the ST‐Co3O4/CC electrode demonstrates good anti‐interference, high repeatability, and robust stability (>3000 s), which can repeatedly detect the glucose species in real human serum (RSD<9.69 %, n=3), and shows broad prospects in non‐enzymatic sensors.

Synthesis, characterization, and NH3 gas sensing application of Zn doped cobalt oxide nanoparticles

Metal oxide semiconductor gas sensors have a wide level of applications. They have the benefits of being powerful, fast, lightweight, dependable, safe and durable. In the current investigation, Cobalt oxide (Co3O4) nanoparticles were prepared using hydrothermal method. So as to build the productivity, the synthesized Co3O4 nanoparticles were doped with ZnO. X-ray diffraction (XRD) technique was used to examine the structure of the synthesized Co3O4nanoparticles. The surface morphology of the nanoparticles was studied by Scanning Electron Microscopy and the elemental analysis done by EDX. FTIR was used to confirm the molecular constituents of the Co3O4 nanoparticles. Optical characterization was done by analyzing the UV absorption spectrum. The gas sensing properties of pure nanocrystalline cobalt oxide have been researched and compared with that of Zn doped cobalt oxide nanoparticles. The response of the Zinc doped Co3O4nanoparticles to ammonia gas was found to be better than that of pureCo3O4 nanoparticles, exhibiting their potential for application in nanosensors.

Template-free Synthesis of Mesoporous and Crystalline Transition Metal Oxide Nanoplates with Abundant Surface Defects

Summary Mesoporous transition metal oxides with crystalline walls show promising applications in catalysis and energy storage. Syntheses of those crystalline mesoporous oxides, however, currently remain as an unmet challenge because of the large volume shrinkage during crystallization in a sol-gel process. Here, we demonstrate a facile and general template-free method to prepare six mesoporous transition metal oxides, e.g., CuO, CoO, and spinel MCo2O4 (M = Co, Cu, Mn, Zn), with highly crystalline walls and continuous mesopores in the forms of two-dimensional nanoplates or nanosheets. The method is based on the thermal crystalline transformation from basic carbonates to mesoporous metal oxides. The crystal interconversion not only endows the crystallinity and mesoporosity of oxides but also generates abundant surface-step defects that show remarkable enhancement of the catalytic activity of porous oxides. Our method likely provides an alternative paradigm for cost-effective and universal synthesis of crystalline mesoporous oxides beyond the traditional templating methods.

Waste eggshells to valuable Co3O4/CaCO3 materials as efficient catalysts for VOCs oxidation

Transition metal oxides have excellent catalytic activities for the oxidation of VOCs, in which it is necessary to find new catalysts/supports with cheap and environmentally-friendly properties. Herein, Co3O4 nanoparticles decorated eggshell catalysts were firstly synthesized via impregnation method, where the waste eggshell is used as an effective hard template and an excellent support with porous structure. A series of Co3O4/Eggshell catalysts were synthesized by changing the different concentration of precursors (different Co3O4 loadings), which were defined as Co3O4/Eggshell-1 (33.1 %), Co3O4/Eggshell-2 (16.7 %) and Co3O4/Eggshell-3 (9.1 %) catalysts. Among of them, the Co3O4/Eggshell-2 exhibited the best activity with the temperature T90 % = 256 ℃, which is about 90 °C lower than Co3O4/oyster shell-2 (benzene catalytic oxidation). And the catalytic activity of Co3O4/Eggshell is remarkably improved as compared to commercially pure Co3O4 nanoparticles and commercially CaCO3. The excellent activity can be attributed to the unique structure of the eggshell and the interaction of CaCO3 and Co3O4. In addition, the catalyst has also showed long-term stability. Moreover, the reaction mechanism of benzene catalytic oxidation was further revealed by in-situ FTIR studies.

Tailoring oxygen sensing characteristics of Co3O4 nanostructures through Gd doping

Detection of oxygen plays an important role in food industry, medicine and controlling automotive exhaust. Here, we have developed a Co3O4 nanoparticle-based oxygen gas sensor. Effect of Gadolinium (Gd) doping on oxygen sensing is investigated using the variation in electrical resistance method which clearly reveals improvement in the sensitivity with the increase in Gadolinium doping in Co3O4. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) studies were systematically performed, to understand the effect of the morphology and crystallographic phase on the level of sensitivity with Gadolinium doping. XRD studies reveal a distortion in the Co3O4 lattice as the lattice parameters increase with increasing Gd doping. SEM and TEM show a change in particle shape and size with Gd doping. Presence of both Co+2 and Co+3 oxidation states were confirmed by XPS. Gd doping, up to 6%, improved the gas sensing response of Co3O4 nanoparticles which is attributed to the decrease in particle size and an increase in oxygen adsorption with Gd doping. Minimum response time of 4 s, 6 s, 10 s and 14 s were observed for pure Co3O4 in 1%, 2%, 3% and 4% oxygen environment respectively. Pure Co3O4 nanoparticles also showed minimum recovery time which was 6 s, 7 s, 9 s and 11 s in 1%, 2%, 3% and 4% oxygen environment respectively. All the prepared compositions were selective to oxygen at 240 °C.

Comparative study of Co-rich and Ce-rich oxide nanocatalysts (CoxCe1−xOy) for low-temperature total oxidation of methanol

Two different nanoparticle oxide systems are obtained depended on Co:Ce atomic ratio (R) using the same reverse nanoemulsion method. The single-phase solid solutions (SPhSS) are formed up to the ratio 1:4 < R < 1:5. The higher Co concentration results in segregation of Co3O4 phase forming nanocomposite of 2 types of nanoparticles (SPhSS and Co3O4). These nanomaterials were characterized using X-ray and electron diffraction, transmission electron microscopy together with linescan EDX analysis of individual nanoparticles, high-resolution XPS, TPR of preoxidized or pre-reduced samples, and testing activity in methanol total oxidation. The catalytic activity increases with increase of Co concentration in SPhSS and is preserved after deposition on alumina support. The catalytic activity of pure Co3O4 nanoparticles is comparable with the Co0.15Ce0.8O2-y solution and is increasing with Ce doping in the Co-rich 2-phase nanoparticle systems. Such a coexistence seems to be responsible for the highest catalytic activity in methanol oxidation.

Magnetic properties of Co3O4 nanoparticles on graphene substrate

Antiferromagnetic nanoparticles have attracted tremendous research interests due to the exhibiting magnetization reversal by quantum tunneling. However, the magnetic properties vary with the inter-particle separation owing to the strong magnetostatic interaction. Thus, a suitable synthetic method is needed to make the antiferromagnetic nanoparticles well-dispersed. Here a facile low-temperature hydrothermal method was used to fabricate the graphene-Co3O4 nanocomposites. The Co3O4 antiferromagnetic nanoparticles have a monodispersed grain size and anchor uniformly on the graphene surface. Compared with the pure Co3O4 nanoparticles with the similar size distribution, the graphene-Co3O4 nanocomposites present different magnetic properties, including the higher magnetization and the lower blocking temperature. It is deduced that the graphene matrix prevents the aggregation of Co3O4 nanoparticles which leads to the differences of magnetic properties.

In-situ synthesis of Co3O4/graphite nanocomposite for high-performance supercapacitor electrode applications

In this work, a low cost and pollution free in-situ synthesis of phase pure Co3O4 nanoparticles and Co3O4/graphite nanocomposite have been successfully developed via co-precipitation method followed by the thermal treatment process. The prepared samples were characterized by powder X-ray diffraction, scanning electron microscope, high resolution transmission electron microscope, Fourier Transform Infrared Spectroscopy and electrochemical measurements. Electrochemical measurements such as cyclic voltammetry, galvanostatic charge–discharge, electrochemical impedance spectroscopy were carried out in 6M KOH aqueous electrolytic solution. The results show the excellent maximum specific capacitive behavior of 239.5Fg−1 for pure and 395.04Fg−1 for Co3O4/graphite nanocomposite at a current density of 0.5Ag−1. This composite exhibits a good cyclic stability, with a small loss of 2.68% of maximum capacitance over a consecutive 1000 cycles. The investigation indicates that the prepared electrode material could be a potential and promising candidate for electrochemical supercapacitors.

Nanocomposite of ultrasmall Co3O4 nanoparticles deposited on ultrathin MoS2 surfaces for excellent performance anode materials in lithium ion batteries

A novel nanocomposite, ultrasmall Co3O4 nanoparticles decorated on ultrathin surface of MoS2 nanosheets, namely MoS2/Co3O4, was synthesized as an anode material for lithium ion battery. The discharge capacity of MoS2/Co3O4 nanocomposite reached 1100.0mAhg−1 after 50 cycles at 200mAg−1, much higher than the pure Co3O4 nanoparticles. Moreover, it could maintain reversible capacity of 946.6mAhg−1 even after 50 cycles at a high current density of 500mAg−1. While increasing the current densities step by step from 100 to 200, 500, and 800mAg−1, the capacities of MoS2/Co3O4 nanocomposite are 1474.9, 1209.9, 952.6 and 801.9mAhg−1, respectively. The excellent electrochemical performance resulted from the designed nanocomposite composed of uniformly distributed ultrasmall Co3O4 nanoparticles and ultrathin MoS2 nanosheets, which maximally utilized electrochemical active MoS2 nanosheets and Co3O4 nanoparticles for lithium ion batteries. Moreover, this composite structure may provide more extra spaces for the storage of lithium ions and help to accommodate the volume change through a synergistic interaction between two active materials.

Synthesis of p-Co₃O₄/n-TiO₂ Nanoparticles for Overall Water Splitting under Visible Light Irradiation.

p-Co3O4/n-TiO2 nanoparticles (~400 nm) for photocatalysis were prepared via carbon assisted method and sol-gel method in this work. The paper also studied the application of visible light illuminated p-Co3O4/n-TiO2 nanocomposites cocatalyst to the overall pure water splitting into H2 and O2. In addition, the H2 evolution rate of the p-Co3O4/n-TiO2 nanocomposites is 25% higher than that of the pure Co3O4 nanoparticles. Besides, according to the results of the characterizations, the scheme of visible light photocatalytic water splitting is proposed, the Co3O4 of the nanocomposites is excited by visible light, and the photo-generated electrons and holes existing on the conduction band of Co3O4 and valence band of TiO2 have endowed the photocatalytic evolution of H2 and O2 with higher efficiency. The optimal evolution rate of H2 and O2 is 8.16 μmol/h·g and 4.0 μmol/h·g, respectively.

Optical and Electrochemical Properties of Co&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt;/SiO&lt;sub&gt;2&lt;/sub&gt; Nanocomposite

Co3O4/SiO2 nanocomposite was obtained via citrate-gel method. 22 nm in size Co3O4 particles in an amorphous SiO2 matrix were obtained. Co3O4:SiO2 wt. ratio was verified using EDX and found to be close to the 80 % nominal ratio. The UV-Vis measurements showed broad absorption bands at around 440 and 790 nm. The optical band gap values were 1.95 and 1.35 eV respectively, being close to those observed for pure Co3O4 nanoparticles. The electrochemical measurements in 5 M KOH solution were performed using a three-electrode type system. Co3O4/SiO2 nanocomposite exhibited high specific capacitance reaching 758 F g-1 at 2.5 mV s-1. Very small solution and electrode-electrolyte interfacial charge transfer resistances were obtained when impedance spectra were analysed.

Higher catalytic activity of porphyrin functionalized Co3O4 nanostructures for visual and colorimetric detection of H2O2 and glucose

5,10,15,20-Tetrakis(4-carboxyl pheyl)-porphyrin (H2TCPP) functionalized chain-like Co3O4 nanoparticles (NPs) were prepared by a facile two-step method. The H2TCPP–Co3O4 nanocomposites were demonstrated to display enhanced peroxidase-like activity than that of pure Co3O4 nanoparticles without modification with H2TCPP molecules, catalyzing oxidation of peroxidase substrate 3,3′,5,5′-tetramethyl-benzidine (TMB) in the presence of H2O2 to produce a blue color reaction. Furthermore, H2TCPP–Co3O4 nanocomposites showed typical Michaelis–Menten kinetics and higher affinity to H2O2 and TMB than that of pure Co3O4 NPs alone. Based on H2TCPP–Co3O4 nanocomposites, a simple, sensitive and selective colorimetric method with TMB as the substrate for the detection of H2O2 and glucose was successfully established. This colorimetric method can be used for the colorimetric detection of H2O2 with a low detection limit of 4×10−7mol·L−1 and a dynamic range of 1×10−6mol·L−1 to 75×10−6mol·L−1. This method was designed to detect glucose when combined with glucose oxidase at a low detection limit of 8.6×10−7mol·L−1 and a dynamic range of 1×10−6mol·L−1 to 10×10−6mol·L−1. Results of a fluorescent probe suggested that the peroxidase-mimic activity of the H2TCPP–Co3O4 nanocomposites effectively catalyzed the decomposition of H2O2 into [OH] radicals.

Facile electrostatic coprecipitation of f-SWCNT/Co3O4 nanocomposite as supercapacitor material

A facile electrostatic co-precipitation route has been employed to prepare f-SWCNT/Co3O4 nano-composite. The prepared samples have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and BET. Application of the prepared samples has been evaluated as supercapacitor material in 6 M KOH solution using cyclic voltammetry in different potential scan rates, ranging from 5 to 50 mV s−1, and electrochemical impedance spectroscopy (EIS). The specific capacitance of f-SWCNT/Co3O4 has been calculated to be as high as 343 F g−1, much higher than that of obtained for pure Co3O4 nanoparticles (77 F g−1). Moreover, the composite material has shown better rate capability (55 % capacitance retention) in various scan rates in comparison with the pure oxide (40 % retention). The composite material also showed excellent cycling performance (92 % capacitance retention) over 5,000 continuous cycles. EIS results show that the composite material benefits form much lower charge transfer resistance, compared with Co3O4 nanoparticles.

Hydrothermal preparation of Co3O4/graphene composite as anode material for lithium-ion batteries

We report a facile hydrothermal strategy to synthesize the Co3O4/graphene composite as anode material for high-performance lithium-ion batteries. The polyhedral Co3O4 particles are homogeneously anchored on graphene sheets, and the growth mechanism has been discussed. The obtained Co3O4/graphene composite displays large reversible capacity (∼840mAh/g after 50 cycles), excellent cyclic stability, and good rate capability in comparison to pure Co3O4 nanoparticles. The flexible structure of graphene sheets and the strong interaction between graphene and Co3O4 particles are beneficial for providing excellent electronic conductivity, short transportation length for Li+ ions, and elastomeric space to accommodate volume varies upon Li+ insertion/extraction.

Partially reduced Co3O4/graphene nanocomposite as an anode material for secondary lithium ion battery

A simple urea-assisted, auto-combustion synthesis was used to fabricate pure Co3O4 nanoparticles and their nanocomposite with 10wt% reduced graphene nanosheets. Samples were annealed at 500°C for 5h under nitrogen atmosphere and their structures and morphologies were characterized by X-ray diffraction, field-emission scanning electron microscopy, field-emission transmission electron microscopy, Raman spectroscopy and BET surface area analysis. The process led to a nanocomposite containing small (25–50nm) Co3O4 nanoparticles deposited on the graphene nanosheets. CHN analysis determined the carbon content in pure Co3O4 nanoparticles and Co3O4/CoO/graphene nanocomposite and found to be very low such as 0.091% and 2.41% respectively. In addition, to know the precise amount of CoO in the designed nanocomposite sample, phase fraction Le Bail's technique was used and found to be 20±0.5%. Using the Co3O4/CoO/graphene nanocomposite as an anode in lithium ion battery led to a higher lithium storage capacity than using pure Co3O4 nanoparticles electrode. The Co3O4/CoO/graphene nanocomposite electrode delivered an initial charge capacity of 890.44mAhg−1 and Exhibit 90% of good capacity retention (801.31mAhg−1) after 30 cycles. While pure Co3O4 nanoparticles electrode (877.98mAhg−1) fades quickly, retains only 60% (523.94mAhg−1) after 30 cycles. The improved electrochemical performance of nanocomposite was attributed to higher electron and Li+ ion conductivity and the larger surface area and mechanical flexibility afforded by the graphene nanosheets. At high current densities, both electrodes showed comparable reversible capacities, demonstrating the suitability of the present synthetic technique.