Co3O4 Nanostructures Research Articles

Synthesis of novel Co3O4 nanocubes-NiO octahedral hybrids for electrochemical energy storage supercapacitors

Fabrication of novel metal oxide nanostructured composites is a proficient approach to develop efficient energy storage devices and development of cost-free and eco-friendly metal oxide nanostructures for supercapacitor applications received considerable attention in recent years. The Co3O4 nanocubes-NiO octahedral structured composite was constructed using facile and one-step calcination process. Cyclic voltammetry, charge-discharge, and electrochemical impedance spectral techniques have been employed to analyze the specific capacitance of the synthesized nanostructures and the composites. Specific capacitance and cycling stability of the composites were evaluated with the pristine Co3O4 and NiO nanostructures. The composite showed a specific capacitance of 832 F g−1 at a current density of 0.25 A g−1, which was ~1.5 and ~1.9-times higher than pristine Co3O4 nanocubes and NiO octahedral structure, respectively. On the other hand, electrode showed approximately 50 % capacity retention at a higher current density (5 Ag-1) because of the uniform morphology of Co3O4 and NiO. The charge-discharge stability measurements of the composite showed an admirable specific capacitance retention capability, which was 94.5 % after 2000 continuous charge-discharge cycles at a current density of 5 A g−1. The superior electrochemical performance of the nano-composite was ascribed to synergistic effects and uniform morphology. Efficient nanostructure development using facile and one-step calcination process and electrochemical performance make the synthesized composite a promising device for supercapacitor applications.

Nonprecious Hybrid Metal Oxide for Bifunctional Oxygen Electrodes: Endorsing the Role of Interfaces in Electrocatalytic Enhancement

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are considered as the core reactions in several alternative energy devices. Engineering the electronic structure of low-cost transition metal oxides (MOs) for the ORR and OER is highly demanding for such devices. Herein, a nonprecious mixed MO hybrid is reported that comprised of nanostructured Co3O4 and CeO2 supported on carbon (Co3O4–CeO2/C) with adequate oxygen vacancies and strong oxide/oxide and oxide/carbon heterointerfaces. The Co3O4–CeO2/C hybrid is highly active toward the ORR with values of the onset potential (−0.12 V) and Tafel slope (69 mV decade–1) comparable to that of benchmark Pt/C with a high limiting current density in alkaline medium. It can catalyze the OER efficiently at a less positive onset potential (0.23 V) and low Tafel slope (176 mV decade–1), in contrast with the standard RuO2 catalyst (0.45 V and 179 mV decade–1). The remarkable activity of the Co3O4–CeO2/C hybrid represents a promising route to replace noble metals and to develop low-cost bifunctional electrodes for energy devices.

Charge transfer complexation between some transition metal ions with azo Schiff base donor as a smart precursor for synthesis of nano oxides: An adsorption efficiency for treatment of Congo red dye in wastewater

This mentioned article aimed to synthesized of nanostructured CuO, Co3O4 and NiO oxides based on the thermal decomposition of precursors associated from the complexation between azo Schiff base chelate (2,2′-((1E,1′E)-hydrazine-1,2-diylidenebis(methaneylylidene))bis(4-((E)-phenyldiazenyl)phenol) (NNOO)) and metal chloride salts with 1:1 M ratio. The NNOO azo Schiff base chelate, and its Cu(II), Co(II) and Ni(II) complexes were synthesized and discussed using microanalytical, molar conductance, magnetic properties, FT-IR, UV–Vis, 1H NMR, mass, and TGA (thermogravimetric analysis) techniques. According to the microanalysis and spectroscopic results, the coordination mode between azo Schiff base ligand and the central metal ion was occurs through NNOO donating atoms of azo Schiff base ligand. The electronic spectra and magnetic susceptibility analyses concluded that all synthesized metal complexes have an octahedral geometrical structural. The metal oxides (CuO, Co3O4, and NiO) nanoparticles were synthesized after the calcination of azo Schiff base complexes at 800 °C in a static air. The assignments of CuO, Co3O4 and NiO nanostructured oxides were discussed based on the FTIR, XRD, and TEM analysis technique. The ability of CuO, Co3O4 and NiO was compared by catalytic degradation of Congo red azo dye. The decolorization behavioral of Congo red dye was examined using spectroscopic UV–Vis techniques. Furthermore, the rate of catalytic decolorization activity of Congo red dye using prepared metal oxides was successfully performed. The dye has been successfully decolorized by ~57% in the presence of Co3O4 NPs at room temperature.

Low-Dimensional Nanostructures Based on Cobalt Oxide (Co3O4) in Chemical-Gas Sensing

Highly sensitive, stable, low production costs, together with easy maintenance and portability, sensors are ever most demanded nowadays for monitoring and quantification of hazardous chemicals/gases in the environment. The utilization of one dimensional (1D) metal oxide nano structured chemical/gas sensors for environmental monitoring is vastly investigated because of their superior surface to volume ratio, stability, and low production costs, to provide information on the presence of chemical species. Several outstanding attempts have been pursued investigating 1D nano structures of Co3O4 over the past decades as an active material for chemical analytes detection owing to its superior catalytic effect together with its excellent stability. This article reviews the state-of-the-art of growth and characterization of Co3O4 1D nano structures and their functional characterization as chemical/gas sensors. Moreover, fundamental concepts and characteristic features, that enhance the key performances of chemical/gas sensors, are discussed. Finally, challenges and prospective for growth and fabrication of 1D Co3O4 chemical/gas sensors are discussed.

Enhanced optoelectronic properties of multifunctional MnFe2O4 nanorods decorated Co3O4 nanoheterostructure: Photocatalytic activity and antibacterial behavior

The binary heterojunction MnFe2O4–Co3O4 nano-photocatalyst (NCs) was constructed by sonochemical technique. HRTEM image indicates the attachment of MnFe2O4 nanorods on Co3O4 nanostructures. UV–vis DRS showed a shift in bandgap of MnFe2O4 (1.8 eV) and Co3O4 (2.86 eV) to 2.47 eV for MnFe2O4–Co3O4 that facilitate enhanced visible light harvesting. The efficiency of MB dye degradation by MnFe2O4–Co3O4 (kinetic rate constant 0.0033 min−1) was boosted 3.66 times than MnFe2O4 (0.0009 min−1) and 4.7 times than Co3O4 (0.0007 min−1). The boosted photocatalytic performance of prepared NCs was supported by the high surface area of NCs (66.067 m2/g). The MnFe2O4–Co3O4 poses excellent recycling ability and photo-corrosive resistance and it was verified with recycled XRD and photocatalytic performance. The ·OH and h+ played major role in degradation of MB dye. The MnFe2O4–Co3O4 showed high antibacterial activity against Escherichia coli and Bacillus subtilis. Hence, the NCs could serve as an effective candidate for photocatalytic applications including pollutant degradation and bactericidal applications.

Degradation of an imidazolium-based ionic liquid in water using monopersulfate catalyzed by Dahlia flower-like cobalt oxide

As the imidazolium-based ionic liquid (IL), 1-Butyl-3-methylimidazolium chloride (BMIMCl), is increasingly employed in various applications, release of BMIM cation into the environment has posed serious threats on aquatic ecology. Thus, it is imperative to eliminate BMIM from water, and, among various techniques for eliminating BMIM, chemical oxidation is the most effective technique. Nevertheless, studies of using SO4−-based chemical oxidation methods for degrading BMIM are still very limited; thus this study aims to develop an effective SO4−-based chemical oxidation process for degrading BMIM. As monopersulfate (MPS) is employed as a source of SO4−, a special cobalt (Co)-based catalyst is proposed and developed here by fabricating Co3O4 into a unique Dahlia flower-like morphology. Such a Dahlia flower-like Co3O4 (DFCoO) not only can exhibit the flower configuration, but also its floral petal components can consist of many filament-like Co3O4 nanostructures, making this DFCoO possess several advantageous properties over the conventional Co3O4 nanoparticle (NP), including higher redox activity, more reactive surface, higher surface area and larger pore volume. Thus, DFCoO shows a much higher catalytic activity than Co3O4 NP to activate MPS for degrading BMIM. A higher MPS dosage and reaction temperature also enhance BMIM degradation by DFCoO + MPS. DFCoO is reusable for activating MPS to degrade BMIM over multiple cycles. BMIM degradation mechanism and pathway by this DFCoO + MPS is also elucidated by identifying radical species and degradation intermediates. The findings of this study offer an useful approach for developing an advantageous catalyst for sulfate-based degradation of BMIMCl.

Mingled MnO2 and Co3O4 Binary Nanostructures on Well-Aligned Electrospun Carbon Nanofibers for Nonenzymatic Glucose Oxidation and Sensing

This work reports on uniformly mingled nanostructures of Co3O4 and MnO2 deposited on a well-aligned electrospun carbon nanofiber (WA-ECNF) mat for rapid glucose electrooxidation and sensing. The hy...

Fabrication of rationally designed CNTs supported binary nanohybrid with multiple approaches to boost electrochemical performance

Abstract An electrode with a three-dimensional spatial framework, good electrical conductivity, higher specific surface area, porous structure, and binder-free design is considered to be most ideal for supercapacitor applications. It is a major challenge for the electrochemical researchers to manufacture an electrode material with a rational design that exhibits all of the above features. In this context, we have fabricated nanostructured Co3O4 and its nanohybrid with carbon nanotubes via a single-step hydrothermal route. A binary nanohybrid sample directly decorated on the three-dimensional nickel foam was used as a binder-free electrode for supercapacitor applications. Our electrode fabricated with multiple approaches showed an excellent specific capacitance of 852 Fg−1 @ 1 Ag−1 and the best rate capability of 89.7% @ 12 Ag−1. Moreover, the nanohybrid electrode possessed outstanding cyclic stability of 91.6% retention after 7000 Galvanostatic charge–discharge cycles. The superior electrochemical activity of the binary nanohybrid is benefiting from its porous nanostructure, hybrid composition, higher specific surface area (145 m2g−1), good electrical conductivity (3.3 × 10−2 Sm−1), and binder-free design. Application study results suggested that multiple approaches for preparing the supercapacitor electrode were constructive and encouraging.

Temperature and pH effect on reaction mechanism and particle size of nanostructured Co3O4 thin films obtained by sol-gel/dip-coating

This article reports the preparation of Co3O4 phase films by sol-gel. Initially, the precursor solution was prepared by the reaction of cobalt acetate tetrahydrate with methanol. Clean glass substrates were dipped into the solution for 4 times with a speed of dipping of 2 cm per minute. Afterwards, the films deposited were thermally treated at 500 °C to produce the Co3O4 phase. FTIR, UV-Vis and XRD techniques were used to analyze the effects of temperature and pH on reaction carried out on the precursor solution. While the microstructural characterization of thermally treated films was performed through XRD and SEM techniques. In parallel, were studied the thermal decompositions of both Co(CH3COO)2 phase as precursor solution S2 powders using TGA-DTA techniques. The results show that Co3(CH3COO)5OH phase was identified as the precursor to the Co3O4 phase. It was observed that the synthesis temperature promotes the formation reaction of Co(CH3COO)5OH. While the decrease in pH by addition of citric acid had 2 effects. The first was to delay the formation reaction, and the second was to decrease the particle size of phase Co3O4 < 10 nm.

Electrochemical study of Mo-doped Co3O4 nanostructures synthesized by sol–gel method

Electrochemical study of Mo-doped Co3O4 nanostructures synthesized by sol–gel method

Morphology-dependent nanocatalysis: tricobalt tetraoxide

Tuning the shape of tricobalt tetraoxide (Co3O4) nanoparticles has been verified to significantly alter the redox feature and the catalytic property. This morphology-dependent nanocatalysis is frequently interpreted with respect to the preferential exposure of the reactive crystal facets that allowed a dense population of active sites for catalysis. In particular, the rod-shaped Co3O4 nanoparticles, typically exposing a substantial fraction of the (110) facet, are featured by the coexistence of tetrahedral Co2+ and octahedral Co3+ sites that are intimately linked to the catalytic activity toward oxidation reactions. Continuous accumulation of experimental data over various Co3O4 nanostructures has gradually clarified that identifying the active sites requires to consider the restructuring of the nanoparticles under the reaction conditions. Moreover, the synergistic effect between the reactive facet and its neighboring less-active facets could not be simply ruled out.

Silky Co3O4 nanostructures for the selective and sensitive enzyme free sensing of uric acid.

In this study, simple, new and functional silky nanostructures of Co3O4 are prepared by hydrothermal method. These nanostructures are successfully used for the enzyme free sensing of uric acid in 0.1 M phosphate buffer solution of pH 7.3. Physical characterization experiments were carried out to explore the morphology, composition and crystalline phase of the newly prepared Co3O4 nanostructures. Scanning electron microscopy (SEM) shows a silk like morphology and energy dispersive spectroscopy (EDS) revealed the presence of Co and O as the main elements. Powder X-ray diffraction (XRD) demonstrates a cubic crystallography with well resolved diffraction patterns. The electrochemical activity of these silky Co3O4 nanostructures was evaluated by cyclic voltammetry (CV) in a 0.1 M phosphate buffer solution at pH 7.3. The high purity and unique morphology of Co3O4 shows a highly sensitive and selective response towards the non-enzymatic sensing of uric acid. This uric acid sensor exhibits a linear range of 0.5 mM to 3.5 mM uric acid and a 0.1 mM limit of detection. The anti-interference capability of this uric acid sensor was monitored in the presence of common interfering species. Furthermore, electrochemical impedance spectroscopy confirms a low charge transfer resistance value of 5.11 K Ω cm2 for silky Co3O4 nanostructures which significantly supported the CV results. The proposed modified electrode is stable, selective and reproducible which confirms its possible practical use. Silky Co3O4 nanostructures can be of great importance for diverse electrochemical applications due to their excellent electrochemical activity and large surface area.

Fine-tuning the water oxidation performance of hierarchical Co3O4 nanostructures prepared from different cobalt precursors

Three different hierarchical nanostructured Co3O4 catalysts are prepared by simple alteration of the precursor. The Co3O4–S catalyst shows superior water oxidation activity due to its improved charge transfer ability and high specific surface area.

Fabrication of nickel foam supported Cu-doped Co3O4 nanostructures for electrochemical energy storage applications

In this study, we have synthesized hierarchical nano-discs of Cu doped Co3O4 (Cu·Co3O4) and decorated them directly on the 3D nickel foam (NF) via single-step urea assisted hydrothermal method. The crystal structure and elemental composition of the fabricated sample were examined using PXRD, Raman, and EDX analyses. The morphology, particle size, and structure of the fabricated sample were evaluated by FESEM analysis. I–V experiments showed that the Cu·Co3O4 samples exhibited higher conductivity (8.73 × 10−3 Sm−1) than the un-doped sample (6.42 × 10−5 Sm−1). The electrochemical investigation revealed that Cu·Co3O4@NF electrode displayed a higher specific capacitance of 728 F/g @1 A/g and exceptional cyclic activity, as after 6000 electrochemical cyclic tests it retains 98.3% of its initial specific capacitance. In comparison, the undoped Co3O4@NF electrode showed inferior electrochemical aptitude as it exhibited 566 F/g specific capacitance @1 A/g and holds just 60.2% of its initial capacitance after 6000 electrochemical tests. Additionally, on increasing the applied current density from 1 A/g to 7 A/g the Cu·Co3O4@NF electrode showed a lower capacity fade of 16%, indicating its excellent rate capability. The integrated electrochemical features (good rate capability, specific capacitance, and superior cyclic activity) of the Cu·Co3O4@NF sample were attributed to its superb electrical conductivity (8.73 × 10−3 Sm−1), binder-free design, 2D morphology, porous nature, and hierarchical structure. The synergistic effects among the acquired novel features of the doped sample not only enhanced its exposed surface area, but also buffered the Cu·Co3O4 samples from pulverization, volume expansion, and agglomeration during the electrochemical investigations.

Nanostructured Co3O4 for achieving high-performance supercapacitor

Supercapacitors with cobalt oxide (Co3O4) electrode are a kind of strong candidates for achieving high-capacity storage energy devices. However, the reported capacitances lower than the theoretical values are undesirable. In this study, a high-performance supercapacitor by using the Co3O4 electrode with a porous nanostructure is enabled by the calcination treatment of metal organic framework ZIF-67. Of note, the resulting Co3O4 electrodes shows high specific capacitance of 1015 F/g under a current density of 1 A/g. Additionally, it exhibits energy density of 36.6 Wh/kg at a power density of 189.5 W/kg and maintains capacitance retention of 78.2% after 5000 cycles at 8 A/g. The strategy proposed here provides a good way to synthesize nanostructured Co3O4, a candidate for constructing high-capacitance energy storage devices.

Drastic Improvement in Capacity-Retention and Polarization of Vanadium Redox Flow Battery with Hydrophilic Co3O4 Nanostructure Modified Activated Graphite Felt Electrodes

Metal oxides supported on carbon materials are reported as catalysts for the positive and negative electrodes of vanadium redox flow battery (VRFB). In this study, thermally activated graphite felt (TGF) is decorated with Co3O4 nanostructure by a low-temperature hydrothermal method. The functional groups on the TGF are believed to nucleate the Co3O4 particles establishing a covalent bridging between them. The bridge improves the electron tunnelling across the electrolyte/electrolyte interface, reducing the overpotential of vanadium redox reactions. The covalent bridge, coupled with the enhanced surface area of the nanostructured-Co3O4 coated TGF (TGF/Co-100–12), are responsible for improved VO2 +/VO2+ and V3+/V2+ redox kinetics in VRFB. A 25 cm2 VRFB employing TGF/Co-100–12 electrodes, compared to TGF, enhances the specific capacity from ∼ 38 Ah l−1 to ∼ 45 Ah l−1 and energy efficiency (EE) from 81 to 87.6% at 100 mA cm−2 and its capacity retention (after 50 cycles) is ∼ 100% higher than that of TGF based VRFB. Besides, a two-cell stack is demonstrated with an EE of 84% and 89% of initial capacity even after 50 cycles, and 3% loss in EE vis-à-vis single cell is mainly due to the additional contact resistance arising out of coupling the cells.

Single-Crystalline Co3O4 Nanocubes for Highly Sensitive Acetone Gas Sensors

Semiconductor metal oxide (SMO) based gas sensors have been considered a promising candidate for gas detection over the past few years due to their simplicity of use, low cost, and flexibility in production. Semiconductor metal oxide gas sensors have various application field such as non-invasive diagnosis of diseases as well as monitoring flammable and toxic gases in domestic and industrial environments. Nowadays, with the increase in interest in health care, gas sensor for early diagnosis of disease and monitoring health status are becoming the next generation of medical technology. However, it is still difficult to selective and accurate analyze only a small amount of target gas in a respiratory gas with a humidity of 95% or more. According to many studies, important detection parameters including sensitivity and selectivity of resistive SMO sensors can be improved through the synthesis of high-efficiency nanostructures.Various metal oxides are suitable for detecting oxidizing or reducing gases by measuring conductivity. Most p-type oxide semiconductors such as NiO, CuO, Cr2O3 and Co3O4 have been widely studied as excellent catalysts for promoting the selective oxidation of various volatile organic compounds (VOCs). The inherent oxygen adsorption of p-type oxide semiconductors can be used to design high-performance gas sensors with low humidity dependence and high recovery rates. Moreover, by introducing a p-type oxide semiconductor as a complex to the n-type oxide semiconductor, it can be used to change the electrical properties near the hetero interface and to change the gas sensing properties.According to the gas sensing mechanism, the operating characteristics of solid-state gas sensors are determined by the receptor and transducer functions. Therefore, it is very important to synthesize metal oxides with optimal morphology and crystal structure. The sensitivity of the sensor can be improved by using nanoparticles with a size of 1 – 100 nm as a sensing material, which is in good agreement with previously reported studies. However, since it is difficult to sufficiently increase the gas sensitivity by simply adjusting the size, it is required to form high sensitivity and selectivity to the target gas by using various types of nanostructures.Among the various p-type SMO, Co3O4 has been studied as a potential material in many applications, including catalysts, magnetism, supercapacitors, batteries, and gas sensors, with indirect band gaps in the region of 1.6-2.2 eV. In most cases, Co3O4 play an important role in strong catalytic activity for specific reactions based on their surface catalytic properties. In particular, the microstructure of Co3O4 in gas sensors is known to be an important factor in determining sensing characteristics. The shape and size of the sensing material greatly influences the sensing performance due to the exposed surface. The selectivity also can be improved by the inherent surface characteristics of p-type oxide semiconductors, and thus the synthesis and characterization of shape-related structure with controlled crystal facet exposure is very interesting research area. Recently, a lot of research has been studied on the gas sensing properties according to the crystal plane of sensing materials.For example, Zhou et al reported that the {111} plane of Co3O4 has a significant effect on ethanol gas detection performance and reacts more sensitively. Liu et al demonstrated that both p-type and n-type sensing responses are facet dependent and sensitivity increases as the exposed {001} facet of TiO2 increases.Therefore, exposing a crystal surface rich in unsaturated metal cations has been identified as the most promising approach to achieving excellent gas sensing performance.In this paper, we report facile preparation of Co3O4 nanostructures for highly active gas-sensing properties for acetone at sub-ppm levels controlling size and shape of nanoparticles. Co3O4 nanocubes shows high reactivity for 1 ppm acetone compared to Co3O4 nanospheres. These results show the potential of Co3O4 as a promising gas sensing material having a different gas response, selectivity, and response kinetics.

Corrigendum to “Effect of anions on the morphology of Co3O4 nanostructures grown by hydrothermal method and their pH sensing application” [Journal of Electroanalytical Chemistry 717–718 (2014) 78–82

Corrigendum to “Effect of anions on the morphology of Co3O4 nanostructures grown by hydrothermal method and their pH sensing application” [Journal of Electroanalytical Chemistry 717–718 (2014) 78–82

Facile one-step deposition of Co3O4-MoS2 nanocomposites using a vacuum kinetic spray process for non-enzymatic H2O2 sensing

Co3O4-MoS2 nanocomposites (NCs) were deposited on titanium sheets at room temperature using a vacuum kinetic spray process and Co3O4 and MoS2 micro powders. Co3O4-MoS2 NCs/Ti electrodes were used as electrocatalysts for non-enzymatic detection of H2O2 in 0.1 M NaOH. X-ray photoelectron spectroscopy revealed an improvement in the synergy between various cobalt-based active sites and MoS2 species in all hybrid electrodes. Analysis of the amperometric response of H2O2 oxidation in 0.1 M NaOH revealed that titanium-modified electrodes with either nanostructured Co3O4 or Co3O4-MoS2 NCs exhibited a wide linear detection range of 20 μM to 1mM. A gradual increase in the amount of Co3O4 in the modified electrodes led to a reduction in charge-transfer resistance and the evolution of more electro-active sites at the working electrode surface, accompanied by an overall enhancement in detection sensitivity to a peak of 3000 μA·mM−1·cm−2 at a Co3O4 content of 75 wt.%. Besides, the titanium modified electrodes with Co3O4-MoS2 NCs exhibited high selectivity for H2O2 oxidation in 0.1 M NaOH.

Hydrothermal synthesis of Co3O4 with different morphology: Investigation of magnetic and electrochemical properties

Co3O4 nanostructures were manufactured using hydrothermal synthesis method and then at high temperature calcinations process was performed. In the production process, the starting material remained constant and the additives were changed where urea (CO(NH2)2), polyvinylpyrrolidone (PVP), ethylenediamine (C₂H₄(NH₂)₂) and sodium hydroxide (NaOH) were used. As a result, different type of nanostructures were obtained (nanosheets, nanosphere, the poppy flowers like structures, clover field-like structures). The crystal properties and chemical composition of the products was confirmed by XRD (X-ray diffraction) technique and FTIR (Fourier-transform infrared) spectroscopy. The surface morphology of the Co3O4 nanostructures was assessed using SEM (scanning electron microscopy). The electrochemical activity of the Co3O4 nanostructures were examined by CV (cyclic voltammetry). CV curves indicate that the charge mechanisms of all samples show pseudocapacitive behaviours. Magnetic characterization of the Co3O4 nanostructures was investigated by vibrating sample magnetometry (VSM) measurements at room temperature. It was concluded that production parameters like temperature and stabilizer used in the production affect the physical and magnetic properties of Co3O4 nanostructures. Vibrating sample magnetometry results showed poor ferromagnetic and typical antiferromagnetic behaviours where typical hysteresis curve was not observed for most of the samples. Such a case attributable to shape and size of the Co3O4 nanostructures.