Co3O4 Nanocrystals Research Articles

CoO nanocrystals dispersed in N-doped carbon networks as enhanced anode for lithium storage

CoO emerges as a promising anode material for lithium-ion batteries (LIBs) because of high theoretical specific capacity and rich resource. However, its practical application is impeded by significant volume expansion and poor electrical conductivity during the charging and discharging cycles. Herein, we construct a nanocomposite of CoO nanocrystals and N-doped carbon serving as an enhanced anode for LIBs by a facile strategy. In the nanocomposite, CoO nanocrystals with average size of 60 nm uniformly were dispersed in N-doped carbon networks. The synergy effects of CoO nanocrystals and N-doped carbon networks can extremely enhance electronic conductivity, relieve volume expansion, and effectively protect CoO nanocrystals from aggregating. Hence, the composite anode delivers large reversible capacity (1190 mAh g−1 at 0.3 A g−1 after 100 cycles), remarkable rate capability (592 mAh g−1 at 5 A g−1), and long cycling ability. This offers a simple approach for designing high-performance anodes for LIBs.

Controllable synthesis of carbon supported cobalt monoxide anode and high-voltage lithium cobalt oxide cathode with enhanced lithium-ion storage

Natural macromolecule amylose (AM) is employed to deoxygenate few-layered graphene oxide (GO) and modulate the surface interaction between GO sheets and Co2+ ions under mild hydrothermal conditions. The obtained Co2+ ions and AM molecule jointly decorated reduced graphene oxide (Co-AM/RGO) sample is further utilized to synthesize both anode and cathode materials with controlled microstructures. To synthesize anode material, the Co-AM/RGO can be directly converted to a hierarchical AM pyrolyzed carbon and RGO supported cobalt monoxide nanocomposite (CoO@AMC/RGO) after a simple inert gas protected thermal treatment. To synthesize cathode material, a carbon coated nano-sized lithium cobalt oxide sample (LiCoO2/C, LCO/C) can be obtained after a solid-state reaction in air by mixing lithium salt with the Co-AM/RGO. The CoO and LCO nanocrystals with significantly controlled sizes are well dispersed in the carbon matrices. The CoO@AMC/RGO anode shows a high reversible capacity of 785.25 mAh·g−1 after 500 cycles at 200 mA·g−1 and 608.25 mAh·g−1 after 700 cycles at 1000 mA·g−1, while the LCO/C cathode delivers a superior reversible capacity of 140.91 mAh·g−1 after 1000 cycles at 1000 mA·g−1 with a high cut-off voltage of 4.6 V. This work provides a new perspective for controllable engineering of electrode materials with enhanced lithium-ion storage performances.

Activation of peroxymonosulfate (PMS) by rGO supported Co3O4 catalyst for iohexol degradation

Sulphate radical (SO4·-) -based advanced oxidation process (SR-AOP) is a promising sewage treatment technology. Reduced graphene oxide (rGO) supported Co3O4 composites were synthesized by a hydrothermal method for the degradation of iohexol (IOH) in the rGO/Co3O4/peroxymonosulfate (PMS) system. Experimental results show that rGO/Co3O4 possessed much better PMS activated ability than pure GO or Co3O4, which is ascribed to the summation of rGO and Co3O4. The efficiency of rGO/Co3O4 composite, single GO and Co3O4 nanocrystals for the degradation of IOH were 98.7%, 15.8% and 79.8% at 15 min, and their corresponding reaction rate constants (kapp) were 0.21 min−1, 0.0077 min−1 and 0.080 min−1, respectively. The results of active species capture experiment and electron paramagnetic resonance (EPR) experiment, showed that singlet oxygen is the main active species, which is non-radical degradation. rGO is conducive to the electron conduction of Co3O4, thus improving the efficiency of PMS activation. The system is simple and efficient, which is an effective technology to remove IOH.

Invariable Simultaneous Emergence of Antiferromagnetic Order and Tetragonal Deformation in CoO Nanocrystals

Invariable Simultaneous Emergence of Antiferromagnetic Order and Tetragonal Deformation in CoO Nanocrystals

In-situ reconstruction of LaCoO3-Co3O4 hetero-interface over lanthanum modified Co3O4 nanocatalyst for improved catalytic activity and sintering resistance in methane combustion

Nanoparticles-based catalysts still suffer from deactivation due to sintering and structural collapse through long-time running at high reaction temperature. Developing simple strategy for improving the sintering resistance of nanoparticles is of great importance for fabrication of durable heterogeneous catalysts. In this work, lanthanum was used to prevent Co3O4 nanoparticles from sintering with restricting growth of nanocrystals by in-situ generation of LaCoO3 perovskite phase during thermal ageing process, further building LaCoO3-Co3O4 hetero-interface with strong interfacial effect. Specifically, the Co3O4 nanocatalyst was loaded with different amount of La by traditional impregnation method and a series of characterizations were carried out to explore the physical and chemical properties of the as-prepared catalysts, including XRD, Raman, BET, SEM, HRTEM, XPS, H2-TPR and O2-TPD. It was found that 5 wt% La-Co3O4 has the highest catalytic activity in CH4 combustion and the value of T90 (temperature of 90% methane conversion) between fresh and aged was only 9 ºC, while this value was 108 ºC over pure Co3O4 sample. The Raman, XPS, H2-TPR and O2-TPD results exhibited that the synergistic effect between Co3O4 and LaCoO3 could not only induce lattice distortion in Co3O4 with more defects and adsorbed oxygen species, enhanced oxygen mobility and reducibility, but also significantly suppress the growth of Co3O4 nanocrystals during thermal ageing treatment.

In Situ Reconstruction of Active Heterointerface for Hydrocarbon Combustion through Thermal Aging over Strontium-Modified Co3O4 Nanocatalyst with Good Sintering Resistance.

The issue of catalyst deactivation due to sintering has gained significant attention alongside the rapid advancement of thermal catalysts. In this work, a simple Sr modification strategy was applied to achieve highly active Co3O4-based nanocatalyst for catalytic combustion of hydrocarbons with excellent antisintering feature. With the Co1Sr0.3 catalyst achieving a 90% propane conversion temperature (T90) of only 289 °C at a w8 hly space velocity of 60,000 mL·g-1·h-1, 24 °C lower than that of pure Co3O4. Moreover, the sintering resistance of Co3O4 catalysts was greatly improved by SrCO3 modification, and the T90 over Co1Sr0.3 just increased from 289 to 337 °C after thermal aging at 750 °C for 100 h, while that over pure Co3O4 catalysts increased from 313 to 412 °C. Through strontium modification, a certain amount of SrCO3 was introduced on the Co3O4 catalyst, which can serve as a physical barrier during the thermal aging process and further formation of Sr-Co perovskite nanocrystals, thus preventing the aggregation growth of Co3O4 nanocrystals and generating new active SrCoO2.52-Co3O4 heterointerface. In addition, propane durability tests of the Co1Sr0.3 catalysts showed strong water vapor resistance and stability, as well as excellent low-temperature activity and resistance to sintering in the oxidation reactions of other typical hydrocarbons such as toluene and propylene. This study provides a general strategy for achieving thermal catalysts by perfectly combining both highly low-temperature activity and sintering resistance, which will have great significance in practical applications for replacing precious materials with comparative features.

Double pyramid stacked CoO nano-crystals induced by graphene at low temperatures as highly efficient Fenton-like catalysts.

Transition metal oxides are widely used as Fenton-like catalysts in the treatment of organic pollutants, but their synthesis usually requires a high temperature. Herein, an all-solid-state synthesis method controlled by graphene was used to prepare a double pyramid stacked CoO nano-crystal at a low temperature. The preparation temperature decreased by 200 °C (over 30% reduction) due to the introduction of graphene, largely reducing the reaction energy barrier. Interestingly, the corresponding degradation rate constants (kobs) of this graphene-supported pyramid CoO nano-crystals for organic molecules after their adsorption were over 2.5 and 35 times higher than that before adsorption and that of free CoO, respectively. This high catalytic efficiency is attributed to the adsorption of pollutants at the surface by supporting graphene layers, while free radicals activated by CoO can directly and rapidly contact and degrade them. These findings provide a new strategy to prepare low carbon-consuming transition metal oxides for highly efficient Fenton-like catalysts.

Correction: Copper and iron co-doping effects on the structure, optical energy band gap, and catalytic behaviour of Co3O4 nanocrystals towards low-temperature total oxidation of toluene

Correction for ‘Copper and iron co-doping effects on the structure, optical energy band gap, and catalytic behaviour of Co3O4 nanocrystals towards low-temperature total oxidation of toluene’ by Hippolyte Todou Assaouka et al., Energy Adv., 2023, 2, 829–842, https://doi.org/10.1039/D3YA00082F.

Enhanced efficiency and long-term stability of all inorganic CsPbBr3 perovskite solar cells via regulation of charge separation and extraction by band engineered-Co3O4 nanocrystals as a hole transport material layer

Insertion of an inorganic HTM intermediate at the CsPbBr3/Carbon interface can significantly improve photo-generated holes extraction efficiency without sacrificing advantages in device stability. Herein, low-cost and eco-friendly Co3O4 nanocrystals were synthesized by precipitation method and utilized as efficient inorganic HTM for CsPbBr3 PSCs. By regulating the hole quasi-fermi level (Ef, HTL) of the perovskite film with Co3O4 nanocrystals possessing a lower conduction band (CB), the built-in electric field (BEF) inside the CsPbBr3 can be reinforced, for which the Co3O4-induced energy level reconstruction facilitates fast charge separation and extraction because of the intensified driving force. In addition, the charge recombination behavior can be effectively inhibited. Finally, all inorganic CsPbBr3 PSCs with an architecture of FTO/c-TiO2/m-TiO2/CsPbBr3/Co3O4/carbon PSC realizes efficiency of 8.92% with an open-circuit voltage (Voc) of 1.531 V. Furthermore, the unencapsulated Co3O4-based PSC exhibits excellent stability in ambient air, keeping 98% of its initial efficiency after 90 days in 80% high humidity condition, and 97% of initial efficiency after 40 days in a high-temperature atmosphere of ∼80 °C.

Shape selective studies on different morphological spinel-structured cobalt oxide loaded rGO nanocomposites: A comprehensive, potential and low-temperature coupling reactions

Morphologically controlled four different catalysts namely nanosphere, caterpillar, pseudo octahedron, and cube-shaped cobalt oxide (Co3O4) are prepared via a facile hydrothermal method. Reduced graphene oxide (rGO) as a support for the nanocatalysts due to the high surface area and efficiency. So, the differently shaped Co3O4 is supported on rGO, and catalytic properties are analyzed. Further, the structurally different Co3O4 nanocrystals are used to catalyze the Ullmann C–O and C–S coupling reactions. In the present work, the catalytic activities of different shaped Co3O4 are compared, and the order of activity of the catalysts is caterpillar > pseudo octahedron > cube > sphere. Besides, the high catalytic efficacy of caterpillar-shaped Co3O4 loaded on rGO enhances the activity further. Interestingly, 20 wt% of Co3O4/rGO exhibits high catalytic activity in the coupling reactions. Hence, this study explains the effect of the catalyst shapes and support material on superior conversions in organic reactions.

Facile synthesis of Co3O4 nanocrystals with superior lithium storage properties from bis (8–hydroxyquinoline) cobalt complex as anode materials for lithium–ion batteries

A simple and facile approach to synthesis Co3O4 nanocrystals by a two–step pyrolysis process of bis (8–hydroxyquinoline) cobalt complex under Ar and air atmospheres successively. The structures and physical properties of the complex, Co@C intermediate and the Co3O4 nanocrystals are characterized by the following techniques: FTIR, XRD, TGA–DTG, Raman, FESEM, HRTEM, N2 adsorption/desorption measurement and XPS. As anode materials in lithium ion batteries, the Co3O4 nanocrystals exhibit high charge/discharge specific capacity, excellent rate performance and remarkable cycle stability. The superior electrochemical properties of the Co3O4 nanocrystals could be attributed to the nanoscaled particle size, high crystallinity and high specific surface area, which is helpful to increase the number of active sites, shorten the diffusion path of lithium ions and electrons, alleviate the volume expansion effect as well as improve the dynamic characteristics during cycling.

Microwave-assisted dry synthesis of hybrid electrode materials for supercapacitors: Nitrogen-doped rGO with homogeneously dispersed CoO nanocrystals

In this research work, we have applied a dry microwave (MW) strategy to synthesize uniformly sized CoO nanocrystals homogeneously dispersed on the basal plane of nitrogen-doped reduced graphene oxide nanosheets (N-rGO NSs). The MW treatment is an ultra-fast process for exfoliation and in-situ reduction of graphite oxide and simultaneous decomposition of the cobalt precursor. The results show that during the MW-assisted synthesis process, the graphite oxide is exfoliated, reduced and combined with the available nitrogen from the precursor to form N-rGO NSs. Simultaneously; the Co ions react with oxygen functionalities on surface of N-rGO NSs to form CoO ([email protected]) nanocrystals. These processes, when combined, effectively prevented the aggregation of the CoO nanocrystals and the re-stacking of the N-rGO layers. The resulting [email protected] nanocomposites exhibited unique surface morphology and electrochemical performance for supercapacitor (SC) applications. As the SC electrode, the nanocomposite delivered high specific capacitance (744.1 F/g at 5 mV/s) and excellent cyclic stability (91.3 % over 5000 cycles). Thus, the MW-processing method proved to be a rapid, effective, and simple approach for single step synthesis of doped rGO-metal oxide electrodes for SC applications.

Purity and properties of spherical shaped Co3O4 nanocrystals prepared by a polyol route using a domestic microwave oven

Obtaining spherical shaped Co3O4 nanocrystals/nanoparticles (considered to be a very promising functional material) at low-cost with chemical purity, reduced crystallite size and useful physicochemical properties has been considered to be challenging. The present work (an attempt in this direction) involves the preparation of spherical shaped Co3O4 nanocrystals from cobalt acetate (dissolved in ethylene glycol) by a polyol synthesis route using a domestic microwave oven along with calcination at a suitable temperature (100/200/300/400 °C used to understand the phase evolution). X-ray diffraction (XRD, including Rietveld), infrared spectral, Raman spectral, energy dispersive X-ray absorption spectral and electron microscopic (SEM/TEM, including SAED) analyses have shown good crystallinity, chemical phase purity, spherical shape, reduced crystallite/particle size and narrow size distribution for the Co3O4 nanocrystal sample calcined at 400 °C. UV-Vis-NIR spectral analysis has shown the existence of multiple bandgap energies (1.51–1.98, 2.44–2.61 and 2.81–3.43 eV). Magnetic measurements have confirmed the antiferromagnetic nature possessing considerable magnetization below and above Neel temperature (TN), which indicates the presence of weak ferromagnetic ordering. The crystallite/particle sizes obtained for the sample calcined at 400 °C through XRD analysis, TEM analysis and using TN value (37.3 K) are 32.0, 33.6 and 31.3 nm, respectively. The method of preparation used is highly yielding, low-cost and more advantageous than many other methods used in the past.

Structure sensitivity in the photocatalytic reduction of CO2 with Co3O4 catalysts

Transition metal oxides (TMOs) have been proposed as potential candidates for CO2 photoreduction (CO2RR). Nonetheless, they often exhibit low efficiency and poor selectivity. Understanding how structural surface features influence photocatalytic reactions is crucial for the development of efficient catalysts. Unfortunately, the intricate structure of TMOs often hinders the thorough understanding of their structure–activity relationships. In this study, three spinel Co3O4 nanocrystals with different planes are used as model catalysts to systematically investigate the structure sensitivity for CO2RR. According to both experimental results and theoretical calculations, Co3O4 with a higher exposure of Co2+ is more effective in the photoreduction of CO2 to CO. This can be attributed to a combination of factors including improved separation of charge carriers, O-defects that promote CO2 activation and the Co2+ sites that facilitate the desorption of CO product. Moreover, the CO2RR performance over Co3O4 catalysts can be controlled by the surface atomic arrangement of Co2+ and Co3+, which through affecting a tradeoff between activating the CO2 reactant and releasing the CO product. Therefore, the proper control of Co2+/Co3+ ratio on the surface of Co3O4 can optimize the reaction performance. This study provides guidance for designing highly active and cost-effective TMO-based catalysts for CO2RR.

Probing the crystal plane effect of Co3O4 for non-enzymatic electrochemistry sensing performance toward hydrogen peroxide

The crystalline structure of catalyst surfaces has an important effect on the catalytic activity. However, the crystal plane effects of Co3O4 catalysts towards H2O2 activation are rarely reported. In this work, Co3O4 hexagon nanosheets, nanosheets, nanorods and nanocubes with respective {111}, {112}, {110} and {001} dominant exposed facets were synthesized by hydrothermal synthesis, and the crystal plane effects of these Co3O4 nanocrystals were compared with respect to their viability as potential for non-enzymatic H2O2 sensors. Co3O4 as a hexagonal nanosheet with a {111} crystal plane exhibited the best performance for H2O2 detection, and exhibited a fast response of 3 s, a wide linear range from 0.0005 ∼ 8.5 mM with sensitivity of 1160.2 μA·mM-1cm-2, and detection limit of 0.049 μM. Overall, the H2O2 detection performance of Co3O4 with different exposed facets was ranked as {111} > {112} > {110} > {001}, which is consistent with the proportion of surface Co3+, indicating that the surface Co3+ exhibit higher activity for H2O2 oxidation. This study indicates that tuning of thecrystal plane of nanocrystals is important to enhancement of non-enzymatic H2O2 detection, and provides an important constraint when developing high efficiency catalysts for non-enzymatic electrochemical H2O2 sensors.

Synthesis of MoS2-loaded Co3O4 nanocrystals for endorsed photocatalytic reduction of mercury (II) ions under visible light

Heavy metal ions in water can cause significant hazards to all living organisms in the ecosystems. This work employs a sol-gel-based process to synthesize a highly photoactive heterojunction composed of molybdenum disulfide (MoS2) and cobalt oxide (Co3O4) nanocrystals. The MoS2/Co3O4 heterojunctions exhibited mesoporous surfaces and high surface areas of 137–161 m2 g−1. Also, the absorption of visible light improved by introducing MoS2 due to the lessening of the bandgap to 1.66 eV for 15% MoS2/Co3O4.The amended photocatalytic reduction of mercury ions (Hg2+) is realized within 50 min of light irradiation over 2.4 gL‒1 of 15% MoS2/Co3O4 at a rate of 36.27 μM min−1 in 30 min and five-times recyclability. The superb action of MoS2/Co3O4 is attributed to the upgraded light absorption and effective separation of carriers.

Lithiophilic Magnetic Host Facilitates Target‐Deposited Lithium for Practical Lithium‐Metal Batteries

Lithium-metal shows promising prospects in constructing various high-energy-density lithium-metal batteries (LMBs) while long-lasting tricky issues including the uncontrolled dendritic lithium growth and infinite lithium volume expansion seriously impede the application of LMBs. In this work, it is originally found that a unique lithiophilic magnetic host matrix (Co3 O4 -CCNFs) can simultaneously eliminate the uncontrolled dendritic lithium growth and huge lithium volume expansion that commonly occur in typical LMBs. The magnetic Co3 O4 nanocrystals which inherently embed on the host matrix act as nucleation sites and can also induce micromagnetic field and facilitate a targeted and ordered lithium deposition behavior thus, eliminating the formation of dendritic Li. Meanwhile, the conductive host can effectively homogenize the current distribution and Li-ion flux, thus, further relieving the volume expansion during cycling. Benefiting from this, the featured electrodes demonstrate ultra-high coulombic efficiency of 99.1% under 1mA cm-2 and 1 mAh cm-2 . Symmetric cell under limited Li (10 mAh cm-2 ) inspiringly delivers ultralong cycle life of 1600 h (under 2mA cm-2 , 1 mAh cm-2 ). Moreover, LiFePO4 ||Co3 O4 -CCNFs@Li full-cell under practical condition of limited negative/positive capacity ratio (2.3:1) can deliver remarkably improved cycling stability (with 86.6% capacity retention over 440 cycles).

Correction: Systematic shape evolution of Co3O4 nanocrystals from octahedra to spheres under the influence of C2O42− and PVP

Correction for ‘Systematic shape evolution of Co3O4 nanocrystals from octahedra to spheres under the influence of C2O42− and PVP’ by Min Kang et al., CrystEngComm, 2016, 18, 9299–9306, https://doi.org/10.1039/C6CE02106A.

Property and Reactivity Relationships of Co3O4 with Diverse Nanostructures for Soot Oxidation.

Cobalt oxide (Co3O4) nanostructures with different morphologies (nanocubes, nanoplates, and nanoflowers) were synthesized by a simple hydrothermal method and used for catalytic oxidation of soot particles. Through the study of the physicochemical properties of the catalysts, the key factors affecting the performance of soot oxidation were investigated. The results showed that all three kinds of Co3O4 nanocrystals exhibited excellent low-temperature activity in catalytic oxidation of soot, and the Co3O4 nanoflowers showed higher oxidation activity of soot compared with Co3O4 nanocubes and Co3O4 nanoplates, whose T m was only 370 °C. The excellent activity of Co3O4 nanoflowers was due to the large amount of Co3+ and lattice oxygen on their surface and highly defective structure, which promoted the adsorption and activation of oxygen species. The large crystallite size and few surface defects were the main reasons for the poor catalytic performance of Co3O4 nanocubes. During soot oxidation, the crystallite size of the catalysts and the contact between the catalysts and soot played a significant role in the catalytic performance.

Enhanced Electrocatalytic Properties of Co3O4 Nanocrystals Derived from Hydrolyzed Polyethyleneimines in Water/Ethanol Solvents for Electrochemical Detection of Cholesterol

The present study describes the effect of hydrolysis of polyethyleneimines in water/ethanol mixture on the morphology of the cobalt oxide (Co3O4), used as the main sensor component. The structure of the generated Co3O4 nanocrystals is consistent with a well-defined cubic phase crystallography, having only cobalt and oxygen elements. Developing simple, low-cost, sensitive, and selective cholesterol biosensors is essential for accurate monitoring of cholesterol to avoid cardiovascular diseases. These nanocrystals exhibit large surfaces suitable for facile and high loading of cholesterol oxidase enzyme through the physical adsorption method. Then, the fabricated cholesterol oxidase/ Co3O4 nanocrystals composite was implemented for potentiometric detection of cholesterol in 10 mM phosphate buffer of pH 7.3. Importantly, the presented cholesterol biosensor revealed a wide linear range of 0.005 mM to 3.0 mM with a limit of detection (LOD) of 0.001 mM. Additionally, the sensitivity of biosensor was estimated around 60 mVdec−1. The selectivity, stability, reproducibility, and repeatability were also observed as satisfactory. The dynamic response of the proposed method demonstrated a fast response time of less than 1 s. Furthermore, the successive addition method confirmed a remarkably stable response towards various cholesterol concentrations. Thus, the developed cholesterol oxidase/ Co3O4 nanocomposite may be used as an efficient alternative method to monitor low cholesterol concentrations form real samples.