Co3O4 Nanowires Research Articles

Constructing Co3O4 Nanowire@NiCo2O4 Nanosheet Hierarchical Array as Electrode Material for High-Performance Supercapacitor

The Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array was constructed on Ni foam using hydrothermal and annealing approaches in turn, from which a NiCo2O4 nanosheet could self-assemble on the Co3O4 nanowire. The structure and morphology of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array were characterized via XRD, EDS, SEM, and FESEM, respectively. The electrochemical performance of the composite array was measured via a cyclic voltammetry curve, galvanostatic current charge–discharge, charge–discharge cycle, and electrochemical impedance and then compared with the Co3O4 nanowire. The results show that the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could reach a high value of 2034 F g−1 at a current density of 2.5 A g−1. After 5000 galvanostatic charge–discharge cycles, the specific capacitance of the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array could still maintain 94.7% of the original value. Therefore, the Co3O4 nanowire@NiCo2O4 nanosheet hierarchical array would be a desirable electrode material for a high-performance supercapacitor.

Fabrication of polyoxometalate dispersed cobalt oxide nanowires for electrochemically monitoring superoxide radicals from Hela cell mitochondria

An ultrasensitive electrochemical sensor is constructed by electrostatically adsorbing negatively charged hourglass-shape Cu-Polyoxometalate (POM) onto a positively charged CoO nanowires modified carbon cloth. The petaloid CoO nanowires have a large specific surface area that can well disperse open-structured Cu-POM to form Cu-POM@CoONWs@CC, which can maximumly expose catalytic active centers (Co2+ and Cu2+) and accelerate mass/charge transfer. In addition to the above advantages, the excellent electron exchange ability of Cu-POM and good conductivity of CoONWs@CC endow the sensor with good detection capability to H2O2 including a linear detection range of 0.05–1.4 μA μM−1, a low detection limit of 0.022 μM, high sensitivity of 110.48 μA μM−1, good selectivity and long-term stability. Due to the fast transformation of superoxide anion (O2∙‐) to H2O2, the sensor can indirectly monitor the electron leakage resulting in the formation of O2∙‐ via detecting H2O2. Afterwards, Hela cell mitochondria were extracted from the living cells that cultured with different mitochondrial inhibitors and the release of O2∙‐ from the corresponding mitochondrial complexes was monitored by the sensor. Through comparing the current signals, we determined that complex I is probably the main electron leakage site. This work could provide meaningful information for the diagnosis of certain oxidative stress diseases.

Oxygen-coordinated cobalt single atom steered by doped-O and CoO for efficient hydrogen evolution at industrial current densities

The exploration and design of highly active, low-cost, transition metal-based electrocatalysts are crucial for large-scale green hydrogen production. Here, the heterostructure of oxygen-coordinated cobalt single atoms with O-doped carbon and CoO nanowires (Co-O-C-O/CoO/CF) is constructed for efficient and stable HER at industrial current densities. Benefiting from the synergistic effect of O doping and CoO nanowires, Co-O-C-O/CoO/CF exhibits extremely low overpotentials of 24.8, 229, and 239 mV to achieve current densities of 10, 500, and 1000 mA cm−2 in 1.0 M KOH solution, respectively, and operates stably for 1000 h at 1000 mA cm−2. Additionally, when coupled with NiFe-LDH in a self-assembled electrolyzer, it delivers a high current density of 1000 mA cm−2 at 1.97 V, along with outstanding stability, outperforming Pt/C||NiFe-LDH and most reported electrolyzers. Density functional theory (DFT) calculations reveal that the optimized d-band center and binding strength of H* and OH* intermediates for Co-O-C-O/CoO/CF lower the energy barrier of the rate-determining step. This work provides a new pathway for engineering Co-based catalysts for green hydrogen production at industrial current densities.

An electrochemical sensor based on Fe2O3 quantum dot-decorated Co3O4 nanowires for cannabis detection in food

An electrochemical sensor based on Fe2O3 quantum dot-decorated Co3O4 nanowires for cannabis detection in food

Constructing core-shell structured Co3O4–MnWO4 composite photoelectrode with superior PEC water purification performance

Semiconductor photoelectrocatalytic (PEC) technology is one of the most effective methods for removing organic pollutants from wastewater in advanced oxidation processes(AOPs). The selection of suitable semiconductor materials as photoanodes is a crucial factor for achieving superior PEC performance. Here, a core-shell structured Co3O4–MnWO4 architecture is created by enveloping MnWO4 nanoparticles onto the surface of Co3O4 nanowires through a two-step hydrothermal process. The optimized Co3O4–MnWO4-5 photoelectrode showed superior PEC degradation efficiency for KN-R (∼91.2% in 2 h) and durable stability (the accelerated lifetime reached ∼9100 s at a current density of 50 mA cm−2). Three actual wastewaters were also collected to verify the practical applicability of the photoelectrode.The energy consumption was measured at 4.48 kWhm−3, with a COD removal efficiency of 83% and a decolorization rate of 98%. These results demonstrate the excellent performance and promising application of the photoelectrode. The enhancement of PEC performance for the core-shell structured Co3O4–MnWO4 architecture can be attributed to the suitable energy band structure of the Co3O4–MnWO4 composite, higher OEP, larger electrochemical active surface area, accelerated transport of interface carriers, and lower charge transfer resistance. The energy band structure of the Co3O4–MnWO4 composite showed a strong redox ability to induce electrons/holes (e−/h+), which enhances the generation of intermediate active species (hydroxyl radical ·OH and superoxide radicals ·O2-). Therefore, the rationally designed core-shell structured Co3O4–MnWO4 architecture exhibited excellent practical applicability in the degradation of organic pollutants.

Nanostructured Co3O4@NiFe-LDH heterojunction catalysts for improving oxygen evolution reaction in alkaline environment

Constructing nano-heterojunction catalysts is a highly efficient method for enhancing the thermodynamics and kinetics towards oxygen evolution reaction. In the present study, NiFe-LDH nanoparticles in-situ grown on Co3O4 nanowires bring about abundant heterogeneous interfaces, which productively increase specific surface area and tune electron density distribution. The as-obtained composite comprises rich unsaturated Co sites on Co3O4 and hybrid crystalline/amorphous NiFe-LDH phase, both of which expedite the flow of charge and expose large amounts of active sites. The Co-Ni-Fe electron transport channels are established at the core-shell heterojunction with the transmission of electrons from Co3O4 to NiFe-LDH. The resultant optimal Co3O4 @NiFe-LDH/NF-100 catalyst displayed attractive OER activity with low overpotential of 270 mV at 50 mA cm−2, along with excellent durability in alkaline media. This typical core-shell heterojunction promotes H2O dissociation and strengthens the adsorption of intermediates, thereby enhancing oxygen evolution reaction.

The p-n heterojunction with multi-parallel built-in electric fields forms localized "electron sink" for directional non-uniform transfer of photogenerated carriers

The internal electric field can induce photogenerated carrier migration. Nevertheless, the spatial arrangement of internal electric fields (independent, series, and parallel) is intricate, which poses a challenge in determining the charge dynamics and process mechanisms. Here, we propose a strategy for in-situ growth of Co1−xS nanosheets and Co3O4 nanowires on the surface of cobalt foam (CoF). Each nanosheet is tightly connected to multiple nanowires to form multiple parallel circuits. Notably, DFT and in-situ characterization demonstrate that Co1−xS, with its low Fermi level, can act as an electron "pump" to spontaneously transfer interface electrons to multiple contacting nanowires, forming a multi-parallel built-in electric field (MPBIEF) and generating localized "electron sink". Remarkably, this unique structure promotes the directional asymmetric dispersion movement of carriers under illumination conditions, effectively reducing the recombination probability. Moreover, TDOS electronic state analysis reveals the interface enhancement mechanism of CoF@CS@CO, and a fixed-bed photocatalytic flow treatment system is developed.

Mechanism of ferrous ions reversibly inhibiting of oxidase-Like activity of Co3O4 nanowires and its application in horticultural fertilizer analysis

Nanozymes are becoming substitutes of some natural enzymes due to their excellent properties, however, little attention has been paid to the catalytic mechanisms and especially inhibition mechanism of nanozymes, which impeded advancement in nanozymes and their wide application including bioanalysis. Herein, non-toxic filamentous virus, M13 phage templated Co3O4 nanowires (NWs) was facilely prepared, which exhibits excellent oxidase (OXD)-like activity and catalytic efficiency. The catalytic mechanism of OXD-like is oxygen vacancies, confirmed by high resolution X-ray photoelectron spectrum of O 1 s, electron paramagnetic resonance spectra and reactive oxygen species scavenging experiments. The substrate of 3,3′,5,5′-tetramethylbenzidine (TMB) for OXD-like is oxidized into blue ox-TMB, and then turned to yellow diimine, depending on TMB concentration and incubation time. Then the mechanism of ferrous ions (Fe2+) inhibition of the oxidase-like activity of Co3O4 NWs was uncovered that Fe2+ competes with TMB for oxygen vacancies. The inhibition is reversible with the type of hybrid of competitive inhibition and non-competitive inhibition with the inhibition constants (KI and KI') of 0.134 mM and 1.012 mM, respectively. Finally, on the basis of the inhibitory effect, a fast, selective and sensitive Fe2+ colorimetric analysis was proposed with two linear parts and a limit of detection of 0.21 μM Fe2+ (S/N = 3), which is applicable to detect Fe2+ in horticultural fertilizers. This study may offer a new strategy for the in-depth study of inhibition mechanism of other nanozymes, which would extend the scope of nanozyme-based biosensing.

Localized photothermal effect of Co3O4 nanowires boosts its catalytic performance in glucose electrochemical detection

Co3O4 has been explored extensively for glucose electrochemical detection, while it suffers from limited performance, due to the poor electrical conductivity originated from its semiconductor nature. Photethermal effect (PE) localized...

3D integrated non-noble metal oxides nano arrays for enhanced nitrate electroreduction to ammonia

The electrochemical nitrate reduction reaction (eNO3RR) to ammonia (NH3) is a promising alternative method to the Haber-Bosch process that requires high temperature and pressure. In this contribution, the integrated Co3O4 nanowire arrays on Ni foam (Co3O4/NF) are reported to exhibit the outstanding performance with a high NH3 yield rate of 117.01 mg h−1cm−2, a superior NH3 Faradaic efficiency of 99.28 %, a high effective current density of 1475.71 mA cm−2, and a good operation durability during 40 consecutive recycling tests (40 h) in 1.0 M NaOH (0.1 M NaNO3). The high-valence metal cations as electron-deficient centers can act as Lewis-acid sites, favorably interacting with the Lewis base NO3−, and accordingly boosting the NO3− adsorption and activation. Moreover, the in-situ growth array configuration provides the substantial active sites and constructs a fast electron-transport channel, thus facilitating the conversion of NO3−-to-NH3. Density functional theory (DFT) calculations also reveal that the Co atoms as the active sites are preferred to adsorb NO3−, implying that the NO3− electroreduction dominates the cathodic reaction rather than hydrogen evolution reaction. This study provides a viable method to design integrated electrodes with enhanced eNO3RR activity and selectivity, which might have broad prospects in the application of renewable energy.

Enhanced •Cl generation by introducing electrophilic Cu(II) in Co3O4 anode for efficient total nitrogen removal with hydrogen recovery in urine treatment

Urine is a nitrogen-containing waste, but can be used as an attractive alternative substrate for H2 recovery. However, conventional urea oxidation reaction is subject to complex six-electron transfer kinetics and requires alkaline conditions. Herein, an efficient method of enhancing •Cl generation by introducing electrophilic Cu(II) into Co3O4 nanowires anode was proposed, which realized the highly efficient TN removal and H2 production in urine treatment under neutral conditions. The key mechanism is that the electrophilic effect of Cu(II) attracts electrons from the oxygen atom, which causes the oxygen atom to further attract electrons from Co(II), reducing the charge density of Co(II). Electrophilic Cu(II) accelerates the difficult conversion step of Co(II) to Co(III), which enhances the generation of •Cl. The generated •Cl efficiently converts urea to N2, while the electron transport promotes H2 production on the CuO@CF nanowires cathode. Results showed that the steady-state concentration of •Cl was increased to about 1.5 times by the Cu(II) introduction. TN removal and H2 production reached 94.7% and 642.1 μmol after 50 min, which was 1.6 times and 1.5 times that of Co3O4 system, respectively. It was also 2.3 times and 2.1 times of RuO2, and 3.3 times and 2.5 times of Pt, respectively. Moreover, TN removal was 11.0 times higher than that of without •Cl mediation, and H2 production was 4.3 times higher. More importantly, excellent TN removal and H2 production were also observed in the actual urine treatment. This work provides a practical possibility for efficient total nitrogen removal and hydrogen recovery in urine wastewater treatment.

Construction of Co/Mn-based nanowires with adjustable surface state for boosting lean methane catalytic oxidation

In this paper, CoMn based nanowires were in-situ grown on foam nickel by hydrothermal method combined with calcination treatment, and a monolithic methane oxidation catalyst was obtained. The effects of hydrothermal temperature and calcination temperature on the crystal structure, micro morphology and catalytic performance of the catalysts were systematically studied. The results indicated that when the hydrothermal temperature was 160 °C and the calcination temperature was 350 °C, Mn doped Co3O4 nanowires with uniform morphology can be obtained, accompanied by the appearance of CoMn2O4. The introduction of Mn ions caused lattice distortion of Co3O4, achieving the regulation of adsorbed oxygen and lattice oxygen. The monolithic MnCoO/NF–H-160 °C catalyst showed the best catalytic activity (T90 = 414 °C) for lean methane catalytic oxidation, which even surpassed the noble metal based catalyst. Its excellent catalytic activity was due to the fact that the catalyst can expose more active sites, rich active oxygen and good mass transfer characteristics. This study provides a new approach for designing efficient monolithic catalysts and has significant potential for application and development in the field of organic waste gas treatment.

Unveiling an S-scheme F–Co3O4@Bi2WO6 heterojunction for robust water purification

Devising a desirable nano-heterostructured photoelectrode based on the charge transfer kinetics mechanism is a pivotal strategy for implementing efficient photoelectrocatalytic (PEC) technology, since the charge separation and utilization efficiency of a photoelectrode is critical to its PEC performance. Herein, we fabricate a F–Co3O4@Bi2WO6 core–shell hetero-array photoanode by coupling Bi2WO6 nanosheets with F–Co3O4 nanowires using a simple solvothermal solution method. The three-dimensional hierarchical heterostructure has a homogeneous chemical interface, helping it to promote an S-scheme-based carrier transport kinetics and maintain excellent cycling stability. Charge density difference calculations verify the electron migration trend from F–Co3O4 to Bi2WO6 upon hybridization and the formation of an internal electric field in the heterojunction, consistent with the S-scheme mechanism, which is identified by in situ irradiation X-ray photoelectron spectroscopy and by ultraviolet photoelectron spectroscopy. The optimized F–Co3O4@Bi2WO6-2 photoelectrode achieves high carrier utilization efficiency and exhibits superior PEC degradation performance for various organic pollutants, including reactive brilliant blue KN-R, rhodamine B, sulfamethoxazole, and bisphenol A. This work not only reveals that F–Co3O4@Bi2WO6-2 is effective for PEC water remediation but also provides a strategy to enhance carrier transport kinetics by designing binary oxides.

Fe-doped Co3O4 nanowire strutted 3D pinewood-derived carbon: A highly selective electrocatalyst for ammonia production via nitrate reduction

Fe-doped Co3O4 nanowire strutted 3D pinewood-derived carbon: A highly selective electrocatalyst for ammonia production via nitrate reduction

A bifunctional heterostructured membrane for efficient emulsion separation and photocatalytic degradation of waterborne organic pollutants

Oily wastewater discharge from industrial activities and oil spills constitutes a crucial environmental issue exacerbated by the presence of water-soluble organic pollutants. Developing efficient superwetting membrane materials capable of separating oil and water while degrading water-soluble organic pollutants is therefore highly desirable. In this study, we prepared I-doped Bi2O2CO3/g-C3N4 heterojunction structures using a hydrothermal method utilizing graphitic carbon nitride (g-C3N4) as the carbon source, which were uniformly distributed on the mesh of Co3O4 nanowire clusters to obtain the heterojunction membrane. The heterojunction membrane demonstrates superhydrophilicity and underwater superoleophobicity, with excellent separation efficiency and outstanding permeability for oil-in-water emulsions. Additionally, the membrane exhibits good stability, superior anti-corrosive property, remarkable reusability, and near-complete degradation of several water-soluble organic dyes under visible-light irradiation. Therefore, this study provides a novel design strategy for multifunctional membranes that achieve effective treatment of complex oil-containing wastewater.

Unidirectional growth of polyaniline on 3D CoO nanowires for aqueous asymmetric supercapacitors

Metal oxide-based binary nanohybrids are a new class of binder-free supercapacitor electrodes. This paper reports the enhanced electrochemical performance of polyaniline (PANI)/CoO nanowires grown on Ni foam for use in aqueous asymmetric supercapacitors (SCs). Several synthetic parameters were optimized for the unidirectional growth of PANI on CoO nanowires. The rationally designed core-shell structured electrode exhibited a high specific capacity of 1113C g−1 (specific capacitance of 2473 F g−1) at a current density of 3 A g−1 and good cycling stability of 86.3 % over 10,000 charge/discharge cycles in a 1 M KOH electrolyte through a substantial synergistic contribution from each component. In addition, an aqueous asymmetric supercapacitor based on these PANI/CoO nanowire arrays exhibited a high specific energy of 35.8 Wh kg−1 and high cycling stability (89.1 % after 5000 cycles). Two aqueous asymmetric supercapacitors connected in series could light up 19 red light-emitting diodes (LEDs). Therefore, this electrode can be considered a superior candidate for the next-generation SC electrodes.

Self‐Assembled Asymmetric Electrodes for High‐Efficiency Thermogalvanic Cells

AbstractThe thermogalvanic cell (TGC) is considered a promising thermoelectric device for directly converting low‐grade waste heat into electricity due to its low‐cost and scalable properties. However, the low output and conversion efficiency limit its practical application. Herein, record‐high thermoelectric conversion performances are achieved in the aqueous ferri/ferrocyanide ([Fe(CN)6]3−/[Fe(CN)6]4−) based TGC by using the electrode of cobaltous oxide nanowires array on carbon cloth fiber. Because of the temperature‐dependence reaction activity between CoO with [Fe(CN)6]4−, the asymmetric electrodes of Co2Fe(CN)6 and CoO nanowires array on carbon cloth fiber are constructed at the hot anode and cold cathode, respectively. These self‐assembled asymmetric electrodes exhibit specific catalysis toward electrode reactions at both ends of TGC, leading to a significant reduction in electronic activation energy. It is demonstrated that the electrodes have high catalytic activity and high specific surface area, enabling the construction of a high‐efficiency TGC with a Carnot‐relative efficiency (ηr) of 14.8% and a maximum output power density (Pmax) of 24.5 W m−2. This work offers an asymmetric electrode engineering pathway for the continuous evolution of TGCs.

Cationic and anionic defect decoration of CoO through Cu dopants and oxygen vacancy for a High‑Performance supercapacitor

CoO has attracted increasing attention as an electrochemical energy storage owing to its excellent redox activity and high theoretical specific capacitance. However, its low inherent electrical conductivity results in sluggish reaction kinetics, and the poor rate capability of CoO limits its widespread applications. Herein, a multiple-defect strategy of engineering oxygen vacancies and Cu-ion dopants into the low-crystalline CoO nanowires (Ov–Cu–CoO) is successfully applied. Because of the advantage of the dual defect synergetic effect, the electronic structure and charge distribution are effectively modulated, thus enhancing the electrical conductivity and enriched redox chemistry. The obtained Ov–Cu–CoO electrode exhibits a high specific capacity of 1388.6 F⋅g−1 at a current density of 1 A⋅g−1, an ultrahigh rate performance (81.2% of the capacitance retained at 20 A⋅g−1) and excellent cycling stability (101.1% after 10,000 cycles). Moreover, an asymmetric supercapacitor device with Ov–Cu–CoO as the positive electrode having a high energy density of 44.1 W⋅h⋅kg−1 at a power density of 800 W⋅kg−1, and can still remain 27.2 W⋅h⋅kg−1 at a power density of 16 kW⋅kg−1. This study demonstrates an effective strategy to enhance electrochemical performance of CoO that can be easy applied to other transition metal oxides.

Bifunctional bimetallic oxide nanowires for high-efficiency electrosynthesis of 2,5-furandicarboxylic acid and ammonia

It is an appealing avenue for electrosyntheis of high-valued chemicals at both anode and cathode by coupling 5-hydroxymethylfurfural (HMF) oxidation and nitrate reduction reactions simultaneously, while the development such bifunctional electrocatalysts is still in its infancy with dissatisfied selectivity and low yield rate. Here, we first report that Zn-doped Co3O4 nanowires array can be served as an efficient and robust dual-functional catalyst for HMF oxidation and nitrate reduction at ambient conditions. Specifically, the catalyst shows a faradaic efficiency of 91 % and a yield rate of 241.2 μmol h−1 cm−2 for 2,5-furandicarboxylic acid formation together with a high conversion of nearly 100 % at a potential of 1.40 V. It also displays good cycling stability. Besides, the catalyst is capable of catalyzing the reduction of nitrate to NH3, giving a maximal faradaic efficiency of 92 % and a peak NH3 yield rate of 4.65 mg h−1 cm−2 at a potential of –0.70 V. These results surpass those obtained using pristine Co3O4 and are comparable to those of state-of-the-art electrocatalysts. Moreover, the catalyst is further employed as the cathode catalyst to assemble a Zn–nitrate battery, giving a peak power density of 5.24 mW cm−2 and a high yield rate of 0.72 mg h−1 cm−2. Theoretical simulations further reveal that Zn-doping favors the adsorption and dissociation of nitrate and HMF species and reduces the energy barrier as well. Our work demonstrates the potential interest of Co3O4-based materials for the highly selective production of valuable feedstocks via ambient electrolysis.

Nanoarchitectonics of nest-like Co3O4 nanowires embedded nitrogen-doped graphene aerogel as electrochemical sensing platform for Pb2+ and Cd2+ trace detection

Nano Co3O4 embedded nitrogen-doped graphene aerogel (Co3O4@NGA) was directly prepared by one-pot hydrothermal synthesis method with ammonia water acting as both precipitant of Co3O4 and nitrogen source of nitrogen-doped graphene aerogel (NGA). This novel method leaved out the calcination process which was necessary for most methods to prepare Co3O4 nanomaterials. The effects of hydrothermal temperature on both morphologies and Pb2+/Cd2+ electrochemical detection performances of Co3O4@NGA were explored. As the hydrothermal temperature rising from 140 °C to 200 °C, the shapes of Co3O4 changed from nanoparticles to nanowires and then to nanoflowers, and nest-like Co3O4 nanowires were architected on NGA sheets at 180 °C. The electrochemical sensor based on the optimized Co3O4@NGA-180 exhibited low limit of detection (LOD) for Pb2+ (7.2 nM) and Cd2+ (10.06 nM) and high sensitivity for Pb2+ (10.51 μA·μM−1) and Cd2+ (8.053 μA·μM−1). The excellent performances were attributed to the synergistic effect of Co3O4 nanowires and porous NGA, which leaded to the fast electrochemical reaction rate in the detection process. Moreover, the Co3O4@NGA-180/GCE sensor had excellent selectivity, repeatability and stability, and could be used to detect traces of Pb2+ and Cd2+ in real water sample.