Co3O4 Nanostructures Research Articles

Synergistic effect of morphology and Co+2/Co+3 ratio on supercapacitor performance of Co3O4/vertical graphene nanosheets binder-free hybrid electrodes

Cobalt oxide (Co3O4) nanostructures decorated vertical graphene nanosheets (VGN) based hybrid electrodes are synthesized to fabricate binder-free high-performance supercapacitors. Tuning of microstructure, morphology, and stoichiometry of Co3O4 nanostructures is endeavoured by growing them in an oxygen medium using the pulsed laser deposition (PLD) technique. The variation in background oxygen pressure transformed the growth morphology of Co3O4 nanostructures from smooth film to nano-particulate caterpillar, flower, and cloud-like. Additionally, the variation in background oxygen pressure significantly influences the Co+2/Co+3 ratio. Moreover, the morphology variation led to a significant change in electrochemical active surface area (ECSA), and the electrochemical impedance characteristics varied from highly capacitive to nearly diffusive nature. These Co3O4/VGN hybrid electrodes exhibited an areal capacitance value of 32 mF/cm2 (1900 F/g) @ 20 mV/s with cyclic stability of 87 % after 3000 charge-discharge (CD) cycles in 1 M KOH electrolyte. Herein, a correlation between morphology, ECSA, and Co+2/Co+3 ratio with areal capacitance values is established. Finally, an asymmetric coin-cell device is fabricated using the Co3O4/VGN as a positive electrode and oxygenated VGN as a negative electrode, respectively. The coin-cell device exhibited a 4 mF/cm2 capacitance with energy and power densities of about 1.8 μWh/cm2 and 218.8 μW/cm2, respectively. Additionally, the coin-cell device displayed excellent cyclic stability of 92% after 5000 CD cycles. The potential utilization of this device is demonstrated by lighting an LED.

Cobalt Oxide 2D Nanosheets Formed at a Polarized Liquid|Liquid Interface toward High-Performance Li-Ion and Na-Ion Battery Anodes.

Cobalt oxide (Co3O4)-based nanostructures have the potential as low-cost materials for lithium-ion (Li-ion) and sodium-ion (Na-ion) battery anodes with a theoretical capacity of 890 mAh/g. Here, we demonstrate a novel method for the production of Co3O4 nanoplatelets. This involves the growth of flower-like cobalt oxyhydroxide (CoOOH) nanostructures at a polarized liquid|liquid interface, followed by conversion to flower-like Co3O4 via calcination. Finally, sonication is used to break up the flower-like Co3O4 nanostructures into two-dimensional (2D) nanoplatelets with lateral sizes of 20-100 nm. Nanoplatelets of Co3O4 can be easily mixed with carbon nanotubes to create nanocomposite anodes, which can be used for Li-ion and Na-ion battery anodes without any additional binder or conductive additive. The resultant electrodes display impressive low-rate capacities (at 125 mA/g) of 1108 and 1083 mAh/g, for Li-ion and Na-ion anodes, respectively, and stable cycling ability over >200 cycles. Detailed quantitative rate analysis clearly shows that Li-ion-storing anodes charge roughly five times faster than Na-ion-storing anodes.

Morphology control and capacitive performance of Co3O4 nanostructures synthesized by NH4F-assisted hydrothermal on Ni foam

Morphology control and capacitive performance of Co3O4 nanostructures synthesized by NH4F-assisted hydrothermal on Ni foam

A review on Co3O4 nanostructures as the electrodes of supercapacitors

Usage of supercapacitors in energy storage applications has now become a new trend due to their auspicious features. The introduction of pseudocapacitance has increased its weightage to be used in a greater number of practical applications. Electrodes are the major constituents of a supercapacitor, based on which the electrochemical performance of the supercapacitor is decided. Among the varieties of electrode materials available, transition metal oxides are the most suitable ones to fulfill the required criteria. Due to the occurrence of faradic redox reactions on the surface of electrodes, the selection of efficient and favorable electrode material plays a major role. Co3O4 (cobalt (III) oxide) is one of the most desirable electrode materials due to its various peculiar features. This paper reviews briefly several factors of Co3O4 as electrode material in supercapacitor applications. It includes comparative discussions towards different synthesize methodologies and the influence of its dimensional morphology on the electrochemical outputs like specific capacitance, energy density, and power density.

Influence of Co3O4 Nanostructure Morphology on the Catalytic Degradation of p-Nitrophenol.

The design and fabrication of nanomaterials with controllable morphology and size is of critical importance to achieve excellent catalytic performance in heterogeneous catalysis. In this work, cobalt oxide (Co3O4) nanostructures with different morphologies (nanoplates, microflowers, nanorods and nanocubes) were successfully constructed in order to establish the morphology-property-performance relationship of the catalysts. The morphology and structure of the nanostructured Co3O4 were characterized by various techniques, and the catalytic performance of the as-prepared nanostructures was studied by monitoring the reduction of p-nitrophenol to p-aminophenol in the presence of excess NaBH4. The catalytic performance was found to be strongly dependent on their morphologies. The experimental results show that the pseudo-first-order reaction rate constants for Co3O4 nanostructures with various shapes are, respectively, 1.49 min-1 (nanoplates), 1.40 min-1 (microflowers), 0.78 min-1 (nanorods) and 0.23 min-1 (nanocubes). The Co3O4 nanoplates exhibited the highest catalytic activity among the four nanostructures, due to their largest specific surface area, relatively high total pore volume, best redox properties and abundance of defect sites. The established correlation between morphology, property and catalytic performance in this work will offer valuable insight into the design and application of nanostructured Co3O4 as a potential non-noble metal catalyst for p-nitrophenol reduction.

Assessment of Oxidative Stress by Detection of H2O2 in Rye Samples Using a CuO- and Co3O4-Nanostructure-Based Electrochemical Sensor

Hydrogen peroxide is essential for biological processes and normally occurs in low concentrations in living organisms. However, exposure of plants to biotic and abiotic stressors can disrupt their defense mechanisms, resulting in oxidative stress with elevated H2O2 levels. This oxidative stress can damage cell membranes, impair photosynthesis, and hinder crucial plant functions. The primary focus of this article is to investigate the effects of salt and herbicide stress factors on the growth of rye samples. For precise quantification of the released H2O2 concentration caused by these stress factors, a non-enzymatic electrochemical sensor was developed, employing nanostructured CuO and Co3O4 oxides. Nanostructured electrodes exhibit high sensitivity and selectivity towards H2O2, making them suitable for detecting H2O2 in real samples with complex compositions. Rye samples exposed to NaCl- and glyphosate-induced stress demonstrated notable concentrations of released H2O2, displaying an increase of up to 30% compared to the control sample. Moreover, optical absorption measurements revealed a substantial decrease in chlorophyll concentration (up to 35% compared to the control group) in rye samples where elevated H2O2 levels were detected through electrochemical methods. These findings provide further evidence of the harmful effects of elevated H2O2 concentrations on plant vital functions.

Enhancing pseudo-capacitive behavior in Mn-doped Co3O4 nanostructures for supercapacitor applications

The study focused on Mn-doped Co3O4 samples, which were synthesized successfully using the coprecipitation method and subsequently annealed at 600 °C. The X-ray diffraction (XRD) patterns displayed distinct peaks corresponding to the spinel-cubic structure of Co3O4. Notably, these patterns indicated a preference for (311) plane orientations, which shifted toward lower diffraction angles as the concentration of Mn increased. The analysis of crystallite sizes for the Mn-doped Co3O4 nanoparticles revealed values of 40 nm, 38 nm, and 38 nm for Co3O4:3%Mn, Co3O4:5%Mn, and Co3O4:7%Mn, respectively. Employing X-ray photoelectron spectroscopy (XPS), the study provided insights into the chemical constituents and valence states of the samples. It revealed the presence of both Co2+ and Co3+ ions, along with different oxygen states. The investigation into the electrochemical behavior of the Mn-doped Co3O4 nanostructures highlighted their pseudo-capacitive nature. The specific capacitance and cyclic stability of these structures were found to be contingent on the concentration of Mn doping. Electrochemical impedance spectroscopy (EIS) data unveiled low interfacial charge resistance and enhanced ion diffusion rates. Notably, the most striking results were observed with the 7 wt% Mn-doped Co3O4 nanomaterials. These materials exhibited an outstanding specific capacitance of 537 F/g at a current density of 1.5 A/g. Additionally, they demonstrated remarkable capacity retention of 94% over a span of 1500 cycles. In conclusion, the Mn-doped Co3O4 nanostructures showcased promising electrochemical performance, which could render them suitable for potential applications in supercapacitors.

Interface Oxygen Vacancy‐Enhanced Co3O4/WO3 Nanorod Heterojunction for Sub‐ppm Level Detection of NOx

Herein, a cobalt oxide/tungsten oxide (Co3O4/WO3) p–n heterojunction for NOx detection is developed and optimized. Field‐emission scanning electron microscopy shows that the WO3 nanorods are embellished with Co3O4 nanostructure. X‐ray photoelectron spectroscopy reveals the presence of oxygen vacancy on the Co3O4 coupled with WO3 heterojunction. Compared to bare WO3 and pure Co3O4, the Co3O4/WO3 heterojunction sensor shows significant sensitivity to NOx at 200 °C. The sensor exhibits higher linearity from 0.4 to 10 ppm of NOx, with a sensing response of 4.4–93%. The NOx sensitivity of the Co3O4/WO3 heterojunction sensor is ninefold higher than that of the pure WO3 sensor. Even in a high humidity (84%) environment, the Co3O4/WO3 heterojunction sensor demonstrates high NOx sensitivity. The sensor maintains remarkable stability measured for up to 4 weeks. The possible NOx sensing mechanism of the Co3O4/WO3 heterojunction is additionally discussed.

Hirshfeld surface analyses, NCI–RDG and effect of surfactant on the size of Co3O4 nanostructures obtained from cobalt(II) nano-complex

Nanostructures of the compound [Co(O2CCH3)2(2-apy)2] (1) (2-apy = 2-Aminopyridine) have been synthesized by a sonochemical process at different of concentrations cobalt acetate tetrahydrate and 2-aminopyridine ligand. The smallest nanostructures of compound 1 are produced in low concentrations of initial reagents. Co3O4 nanoparticles were prepared from thermal decomposition in oleic acid as a surfactant and direct calcination of compound 1 at different temperatures. The effect of calcination temperature and oleic acid, as a surfactant, was investigated on the particle size distribution of the products. The compounds were studied by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), UV–vis, FT-IR spectroscopy, thermal analyses (TGA and DTA) and elemental analyses. Hirshfeld surface analyses and Noncovalent interaction reduced density gradient (NCI-RDG) calculations of compound 1 were illustrated and discussed in order to quantify the order and nature of intermolecular interactions in the crystal network. Hirshfeld surface analysis indicated that there are other types of intermolecular contacts in Crystal, including H…H, H…O, C…H, H…N, C…C and C…N interactions, and the contributions of these interactions are 55.4%, 19.7%, 19.2%, 4.1%, 1.4% and 0.2%, respectively.

Hollow-architected Co3O4 for enhancing Oxone activation to eliminate an anesthetic, benzocaine, from water: A structure-property investigation with degradation pathway and eco-toxicity

BackgroundAs the most widely-used oral anesthetic, benzocaine (BZC), is increasingly detected in municipal wastewater and regarded as an emerging contaminant. Thus, it would be highly imperative to develop useful methods to eliminate BZC from water. However, very few studies have been ever reported, and only photocatalysis of BZC was attempted. Therefore, this present study aims to be the first study of developing the sulfate-radical-based chemical oxidation technology (SR-COT) for degrading BZC. MethodsFor establishing a useful SR-COT, the oxidant, Oxone, is then adopted and a facile nanostructured Co3O4 is then developed for maximizing catalytic activities of Oxone activation by creating a hollow fluffy Co3O4 nanostructure using CoMOF as a template, followed by a carving-architected treatment to afford the hollow fluffy Co3O4 (HFCC). Significant findingsIn comparison to the solid (non-hollow) Co3O4 (SCC), HFCC possesses not only the excellent textural properties, but also superior electrochemical properties and highly reactive surfaces, making HFCC exhibit the significantly higher catalytic activity than SCC as well as traditional Co3O4 nanoparticle in activating Oxone to degrade BZC. The density function theory calculation is performed to investigate the degradation pathway, and the corresponding eco-toxicity is also studied to realize the degradation implication of BZC by HFCC-activated Oxone.

Development of Co3O4/TiO2/rGO photocatalyst for efficient degradation of pharmaceutical pollutants with effective charge carrier recombination suppression

Pharmaceutical contaminations in the water resources becomes very serious global environmental issue. Therefore, these pharmaceutical molecules should be removed from the water resources. In the current work, 3D/3D/2D-Co3O4/TiO2/rGO nanostructures were synthesized through a facile self-assembly-assisted solvothermal method for an effective removal of pharmaceutical contaminations. The nanocomposite was finely optimized through the response surface methodology (RSM) technique with different initial reaction parameters and different molar ratios. Various characterization techniques were used to understand the physical and chemical properties of 3D/3D/2D heterojunction and its photocatalytic performance. The degradation performance of ternary nanostructure was rapidly increased owing formation of 3D/3D/2D heterojunction nanochannels. The 2D-rGO nanosheets play an essential role in trapping photoexcited charge carriers to reduce the recombination process rapidly as confirmed by photoluminescence analysis. Tetracycline and ibuprofen were used as model carcinogen molecules to examine the degradation efficiency of Co3O4/TiO2/rGO under visible light irradiation using halogen lamp. The intermediates produced during the degradation process were studied using LC-TOF/MS analysis. The pharmaceutical molecules tetracycline and ibuprofen follows pseudo first order kinetics model. The photodegradation results show that the 6:4 M ratio of Co3O4:TiO2 with 5% rGO exhibits 12.4 times and 12.3 higher degradation ability than pristine Co3O4 nanostructures against tetracycline and ibuprofen, respectively. These results shows high efficiency of Co3O4/TiO2/rGO composite against the degradation of tetracycline and ibuprofen.

In-situ growth of nonstoichiometric CrO0.87 and Co3O4 hybrid system for the enhanced electrocatalytic water splitting in alkaline media

The development of electrocatalysts for electrochemical water splitting has received considerable attention in response to the growing demand for renewable energy sources and environmental concerns. In this study, a simple hydrothermal growth approach was developed for the in-situ growth of non-stoichiometric CrO0.87 and Co3O4 hybrid materials. It is apparent that the morphology of the prepared material shows a heterogeneous aggregate of irregularly shaped nanoparticles. Both CrO0.87 and Co3O4 have cubic crystal structures. Its chemical composition was governed by the presence of Co, Cr, and O as its main constituents. For understanding the role CrO0.87 plays in the half-cell oxygen evolution reaction (OER) in alkaline conditions, CrO0.87 was optimized into Co3O4 nanostructures. The hybrid material with the highest concentration of CrO0.87 was found to be highly efficient at driving OER reactions at 255 mV and 20 mA cm−2. The optimized material demonstrated excellent durability for 45 h and a Tafel slope of 56 mV dec−1. Several factors may explain the outstanding performance of CrO0.87 and Co3O4 hybrid materials, including multiple metallic oxidation states, tailored surface properties, fast charge transport, and surface defects. An alternative method is proposed for the preparation of new generations of electrocatalysts for the conversion and storage of energy.

Au-decorated Co3O4 nanostructures for plasmonic enhanced PEC sensing of cancer biomarkers

Au-decorated Co3O4 nanostructures for plasmonic enhanced PEC sensing of cancer biomarkers

Tubular nanostructured Co3O4@N-containing carbon nanofibers to tune the surface structure for efficient electrochemical capacitors

BackgroundAlthough N-rich electrode materials have good capacitive performance, further exploration of more efficient and straightforward methods to produce nanoporous carbon materials with a high heteroatom content remains challenging. MethodsTubular nanostructured Co3O4@N containing carbon nanofibers (PPMCoU(10)) are fabricated by coaxial electrospinning to improve the overall electrochemical performance. Significant findingsThe PPMCoU(10) electrode shows a high specific capacitance (193 Fg−1 at 1 mAcm−2), good rate capability (88% capacity retention at 20 mAcm−2), high energy density (24.5 Whkg−1 at 400 Wkg−1), and good cycling stability (only 8.0% loss after 10,000 cycles at 1 mAcm−2). The enhanced stored charge capacity of the PPMCoU(10) electrode is attributed to the synergy of high microporosity with a high surface area, tubular nanostructure, low crystallinity of Co3O4, many oxygen vacancies, and electrochemically active nitrogen atoms.

Revealing the influence of conversion-type Co3O4 dimensionality on cyclic and rate performance for lithium storage

Cobalt tetraoxide (Co3O4) is regarded as a promising anode material for Li-ion batteries owing to its high theoretical capacity (890 mAh g−1), simple preparation, and controllable morphology. Nanoengineering has been proven to be an effective method for producing high-performance electrode materials. However, systematic research on the influence of material dimensionality on battery performance is lacking. Herein, we prepared Co3O4 with various dimensionalities (one-dimensional (1D) Co3O4 nanorod (NR), two-dimensional (2D) Co3O4 nanosheet (NS), three-dimensional (3D) Co3O4 nanocluster (NC), and 3D Co3O4 nanoflower (NF)) using a simple solvothermal heat treatment method, and their morphologies were controlled by varying the precipitator type and solvent composition. The 1D Co3O4 NR and 3D samples (3D Co3O4 NC and 3D Co3O4 NF) exhibited poor cyclic and rate performances, respectively, while the 2D Co3O4 NS exhibited the best electrochemical performance. The mechanism analysis revealed that the cyclic stability and rate performance of the Co3O4 nanostructures are closely related to their intrinsic stability and interfacial contact performance, respectively, and the 2D thin-sheet structure can achieve an optimal balance between the two, resulting in the best performance. This work presents a comprehensive study on the effect of dimensionality on the electrochemical performance of Co3O4 anodes, providing a new concept for the nanostructure design of conversion-type materials.

Fe-doped Co3O4 nanostructures prepared via hard-template method and used for the oxygen evolution reaction in alkaline media

Low-cost and highly efficient anode catalysts are required for the oxygen evolution reaction (OER), which is integral to the commercialization of alkaline-based water electrolysis. Herein, pore size-controlled Fe-doped Co3O4 nanostructures are prepared as non-precious metal anode catalysts using a hard-template method with silica beads of different sizes, ranging from 20 to 1000 nm in diameter. The pore size distribution and specific surface area of the catalysts are measured by nitrogen adsorption/desorption analysis and mercury intrusion porosimetry. The electrochemical properties and OER performances of the catalysts are evaluated in half and unit cells, respectively. Among the catalysts studied, FCO-T-500 synthesized using 500 nm-sized silica beads exhibits the best OER activity and stability, given by a high current density of 847 mA cm−2 at 1.8 V and superior 100 h-stability during single cell test of anion exchange membrane water electrolysis. The improved OER performance of FCO-T-500 can be attributed to the optimal pore size favorable for gas diffusion and mass transport, sufficient surface OH and H2O groups produced via KOH leaching, the largest number of electrocatalytic active sites, and the fastest charge-transfer reaction.

Enhanced xylene sensing performance of hierarchical flower-like Co3O4 via In doping

Metal ions doping is a typical approach for tuning sensing properties of metal oxide semiconductors based gas sensors. Herein, hierarchical flower-like pure and In-doped Co3O4 nanostructures assembled by porous two-dimensional (2D) nanosheets are synthesized via a solvothermal method and annealing process. The sensing measurements display that the In@Co3O4-4 based sensor possesses high response value of 55.9 toward 100 ppm xylene at 150 °C, which is nearly 3.8 times larger than that of pure Co3O4 sensor. Furthermore, it possesses good selectivity and anti-humidity properties. Combined with the results of DFT calculations, the mechanism of enhanced gas sensing performance is analyzed systematically.

Dopant-induced photodegradation of organic water pollutants using cobalt oxide nanostructures of low cytotoxicity

Metal oxides are the simplest and most approachable solutions for attaining multifunctional properties applicable to modern-day technology. With growing concern over environmental conservation, an evaluation of the cytotoxicity of the metal oxides becomes necessary. The present work focuses on the photocatalytic and cytocompatibility behavior of Co3O4 nanomaterial. It has been observed that the addition of Li to the Co3O4 nanostructure generates a positive impact on the photodegradation of cationic dyes under UV light. The photocatalyst with 1 wt% Li-doped Co3O4 was found to be the most competent among the synthesized samples. Further, the sample has been employed for photocatalytic removal of the hazardous pollutant, pyrocatechol (PyC), in the presence of visible light. A photocatalytic efficiency of 84.5% (after 9 h) and high stability (86% after 5 cycles) is observed. A noteworthy revelation is the lower toxicity observed for Li-doped samples when compared to the pristine Co3O4. The (3-(4,5-dimethylthiazolyl-2)− 2,5-diphenyltetrazolium bromide) (MTT) assay carried out on mouse skin fibroblast cell lines reveals cytotoxicity inhibition by the doped nanostructures for up to 10 μg mL−1 concentration and excellent cell proliferation up to 24 h. The superior catalytic behavior and non-toxic nature of the Li-doped Co3O4 nanostructures provide ample opportunity for their integration into water remediation and effluent treatment systems.

Surface modification of Co3O4 nanostructures using wide range of natural compounds from rotten apple juice for the efficient oxygen evolution reaction

In this study, a new strategy has been produced to use a rotten apple juice as a source for the surface modification of Co3O4 nanostructures, giving rise to efficient electro-catalysts for driving oxygen evolution reaction (OER) at relatively low over potential. We have studied the morphology, chemical composition, and crystalline aspects of Co3O4 nanostructures using different analytical techniques. The Co3O4 nanostructures grown with rotten apple juice were observed with low impurity of Fe and P, surface modification, reduced particle size, high concentration of oxygen vacancies, defects and cubic phase of Co3O4. Furthermore, we have used the surface modified Co3O4 nanostructures for water electrolysis and noticed the significant performance towards OER in alkaline conditions. The electrochemical characterization revealed that the Co3O4 nanostructure prepared with 20 mL of rotten apple juice exhibits an overpotential value of 269 mV at 20 mA/cm2 current density. The charge transport resistance (Rct) at the interface was estimated around 118.9 Ω, confirming an excellent reaction kinetics on the Co3O4 nanostructures and highly supported efficient performance towards OER. The Co3O4 nanostructures prepared with 20 mL of rotten apple juice has shown an acceptable durability for 40 h, verifying the long-term use. The performance of Co3O4 nanostructures with apple juice could be attributed to high oxygen vacancies due to high density of Co2+ ions on the surface, impurities of Fe and P, reduced nanoparticle size, defects in the structures, and favorable chemical composition. At the end, surface modified Co3O4 nanostructures was observed as an outperformed electrocatalyst when prepared with rotten apple juice. Therefore, this can be used in diverse purposes including energy conversion and storage applications.

Highly Heterogeneous Morphology of Cobalt Oxide Nanostructures for the Development of Sensitive and Selective Ascorbic Acid Non-Enzymatic Sensor

The surface tailored metal oxide nanostructures for the development of non-enzymatic sensors are highly demanded, but it is a big task due to the wide range of complexities during the growth process. The presented study focused on the surface modification of the heterogeneous morphology of cobalt oxide (Co3O4) prepared by the hydrothermal method. Further surface modification was conducted with the use of sodium citrate as a reducing and surface modifying agent for the Co3O4 nanostructures through the high density of oxygenated terminal groups from the citrate ions. The citrate ions enabled a significant surface modification of the Co3O4 nanostructures, which further improved the electrochemical properties of the Co3O4 material toward the design of the non-enzymatic ascorbic acid sensor in a phosphate buffer solution of pH 7.4. The morphology and crystal arrays of the Co3O4 nanostructures were studied by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD) techniques. These physical characterizations showed the highly tailored surface features of Co3O4 nanostructures and a significant impact on the crystal properties. The electrochemical activity of Co3O4 was studied by chronoamperometry, linear sweep voltammetry, and cyclic voltammetry (CV) for the detection of ascorbic acid. The linear range of the proposed sensor was measured from 0.5 mM to 6.5 mM and a low limit of detection of 0.001 mM was also estimated. The presented Co3O4 nanostructures exhibited significant surface roughness and surface area, consequently playing a vital role toward the selective, sensitive, and stable detection of ascorbic acid. The use of a low cost surface modifying agent such as sodium citrate could be of great interest for the surface roughness and high surface area of nanostructured materials for the improved electrochemical properties for the biomedical, energy storage, and conversion systems.