3D Co3O4 Research Articles

0D Zn-ZIF/2D Co-ZIF Derived 0D ZnO/2D Co<sub>3</sub>O<sub>4</sub> Heterostructures for ppb-Level Acetone Detection

Detecting acetone is meaningful in industrial processes and medical fields. Herein, 0D Zn-ZIF/2D Co-ZIF derived 0D ZnO/2D Co3O4 heterostructures are originally designed to improve acetone sensing properties. It is found that when the temperature is 250 °C, the 0D ZnO/2D Co3O4 possesses the highest response (4.73) to 5 ppm acetone, which is about three times more than that of pure 0D ZnO and pure 2D Co3O4. The detection limit of 0D ZnO/2D Co3O4 sensor could be as low as 100 ppb. The response/recovery time of 0D ZnO/2D Co3O4 sensor to 100 ppm acetone is only 3 s/15 s. It is demonstrated that with the introduction of 0D ZnO, the stacking of 2D Co3O4 nanosheets is inhibited and p-n heterojunctions are formed, which could significantly enhance acetone sensing performance.

In situ transformation of 3D Co3O4 nanoparticles to 2D nanosheets with rich surface oxygen vacancies to boost hydrogen generation from NaBH4

Despite substantial progress in various application fields of polyoxometalates (POMs), the use of POMs as ligands to alter the structure of solid catalysts in heterogeneous catalysis requires additional efforts. Herein, we used the reduced α-SiW12O404- (RSTA) as an inorganic ligand to mediate Co3O4 nanoparticles that efficiently promote the hydrolysis of NaBH4 to generate hydrogen with multiple activities (4747 mL/(gcat·min)) compared with NaBH4-pretreated Co3O4 (1236 mL/(gcat·min)), pristine Co3O4 (inactive) and commercial Co3O4 (inactive) at 25℃. RSTA induced both electronic and morphology effects on Co3O4 through in situ driving 3D Co3O4 nanoparticles to 2D Co3O4 nanosheets with rich surface oxygen vacancies or Co2+ during the hydrolysis process. This modulation by RSTA allowed more active sites, including both electron-rich Co0 and electron-deficient Co2+, facilitating BH4- and H2O adsorption and thus hydrogen generation. The promoted mechanism of the RSTA on both the microstructure and the catalytic performance was further proposed.

Investigation of advanced catalytic effect of Co3O4 nanosheets modified carbon felts as vanadium flow battery electrodes

3D petal-like Co3O4 nanosheets with the mesoporous structure are produced successfully and coated firmly on carbon fibers by simply electrodepositing cobaltous acetate tetrahydrate and its subsequent calcination. The morphology of the precursor, which dominates the structure of the final product, evolves from layers of moss-like amorphous cobalt compounds to Co3O4 nanosheets with obvious lattice defects. Compared with Co3O4 nanoparticles synthesized by the traditional hydrothermal method, the nanosheet layered structure has a higher specific surface area and more active sites. The 3D Co3O4 nanosheets are further used as modification materials to fabricate electrodes with excellent electrocatalytic activity and good reversibility towards both the positive and negative vanadium redox reactions. With the Co3O4 nanosheets modified electrodes, the battery demonstrates remarkably improved performance and shows excellent long-term stability with a dischargeable capacity decay rate of only 2.9 mAh per cycle, which is 70% lower than that of the battery with unmodified electrodes.

2D Co3O4 stabilizing Rh nano composites developed for visual sensing bioactive urea and toxic p-aminophenol in practice by synergetic-reinforcing oxidase activity

To enlarge the perspective of nanozyme, 2-dimensional Co3O4 stabilizing Rh nano composite (2D Co3O4@Rh NC) was identified and developed first by one-pot surfactant-aided oxido-reduction. By virtue of the synergetic-reinforcing oxidase activity between 2D Co3O4 substrate and Rh nano particles, the obtained 2D Co3O4@Rh NC could catalyze the oxidation of chromogenic substrate 3,3′,5,5,’-tetramethylbenzidine (TMB) to blue oxTMB with quite a low Michaelis-Menten constant (Km) of 0.018 mM and a quick vmax of 6.45 × 10–8 M s–1, expressing superior oxidase-like catalysis with a wide temperature range from 20 to 60 °C. Importantly, either bioactive urea or toxic p-aminophenol (p-Ap) could exclusively alter the existed state of oxTMB with differentiable color changes. Under the optimized conditions, 2D Co3O4@Rh NC was successfully applied for ratiometric colorimetric sensing urea and p-Ap in environmental water, soil and urine samples with low detection limits (1.1 μM for urea and 0.68 μM for p-Ap) and satisfactory recoveries (96.0–105.8%). The synergetic enhanced oxidase-like activity of 2D Co3O4@Rh NC and the different reaction mechanisms of the 2D Co3O4@Rh NC-TMB system to urea and p-Ap were investigated. Not only does the work provide an efficient way for sensing organic pollution of p-Ap, it will offer an efficient potential for diagnosing urea-related diseases on clinical medical testing in future.

Sewage-free preparation of 2D metal oxides by a rapid freezing soft template method for extraordinarily activating solar-driven humidity VOC combustion

2D Co3O4 can be synthesized without producing sewage, which shows a nearly 100% ambient sunlight irradiated combustion efficiency for formaldehyde, CH4, acetone, CO, as it assisted by spectrally selective coating.

3D radial Co3O4 nanorod cluster derived from cobalt-based layered hydroxide metal salt for enhanced trace acetone detection

One-dimensional cobalt oxide (Co3O4) exhibits great potential in gas sensing, but the application is severely hindered because of the agglomeration or close packing during the normal synthesis process. Herein, 3D radial Co3O4 assembled with nanorods is fabricated by employing cobalt-based layered hydroxide metal salt (Co-LHMS) as a self-template. Meanwhile, Co3O4 with flake floral and dumbbell radial structure obtained by tuning the hydrothermal reaction time of precursors is used as a control group for gas sensing tests. The sensitivity of 3D radial Co3O4 to sub-ppm acetone is 4 times higher than other structures and the detection limit is 100 ppb at a relatively low working temperature of 200 ℃, which is excellent among intrinsic acetone sensors based on pure Co3O4. The satisfactory gas sensing performance can be ascribed to the large specific surface, numerous transmission pathways, and low grain boundary resistance of the material. Furthermore, this work provides an idea for the further improvement of one-dimensional gas sensors.

A visible-light active p-n heterojunction NiFe-LDH/Co3O4 supported on Ni foam as photoanode for photoelectrocatalytic removal of contaminants

Light and electricity are the most prevalent energy sources in natural environment. Herein, a visible-light active Ni foam@NiFe-LDH/Co3O4 composite was successfully prepared by loading 1D Co3O4 nanowires on the surface of 2D NiFe-LDH nanosheets to be a p-n heterojunction supported on the 3D Ni foam through hydrothermal method, which can be used as photoanode directly for photoelectrocatalytic (PEC) process to simultaneously remove bisphenol (BPA) and Cr(VI) from water. This unique Ni foam-based photoanode modified by NiFe-LDH/Co3O4 heterojunction can fully expose the active sites, enhance visible-light absorption and facilitate the migration and separation of photogenerated carriers, thus obtained a boosted efficiency for simultaneous removal of BPA and Cr(VI) under a low applied voltage. Furthermore, the convenient recyclability and excellent stability of the as-prepared Ni foam@NiFe-LDH/Co3O4 also show a great potential in environmental purification.

Cobalt Oxides with Various 3D Nanostructured Morphologies for Catalytic Reduction of 4-Nitrophenol: A Comparative Study

ABSTRACT Catalytic reduction processes represent a promising approach to treat the toxic nitro-aromatic pollutant, 4-nitrophenol (4-NP), via converting 4-NP to 4-aminophenol (4-AP). Many efforts have been invested into developing non-precious metal oxides for the conversion of 4-NP to 4-AP. As Co3O4 is validated as a useful non-precious metal catalyst for 4-NP reduction, it is crucial to probe into the relationship of morphology-property-reactivity of Co3O4 catalysts for optimizing design of Co3O4 for 4-NP reduction. Thus, the catalytic activity of Co3O4 for 4-NP is particularly investigated in this study through examining 3-dimensional (3D) Co3O4 catalysts (3DCoOs) with different nanostructured morphologies, including the conical-Co3O4 (CCO), stacked-Co3O4 (SCO), needled-Co3O4 (NCO) and floral-Co3O4 (FCO), for 4-NP reduction. A remarkably enhanced activity in the reduction of 4-NP is realized over all 3DCoOs than commercial Co3O4 catalysts. In particular, CCO shows the highest catalytic performance (k =0.6882 min-1 and Ea = 37.4 kJ mol-1), whereas FCO exhibits the least catalytic activity, with k =0.4709 min-1 and Ea = 47.1 kJ mol-1. These values are far more superior than those obtained by the commercial Co3O4 and the reported catalysts. All four 3DCoOs also show stable recyclability with complete 4-NP reduction over five successive cycles. These results and findings suggest that 3DCoOs are certainly advantageous Co-based catalysts for 4-NP reduction, and, through this study, the relationship between morphology, property and reactivity would be correlated to offer useful insights to design and apply 3D nanostructured Co3O4 catalysts for 4-NP reduction.

Graphene oxide induced assembly and crumpling of Co3O4 nanoplates

Cobalt (II, III) oxide (Co3O4) has been widely studied and applied in various fields, however, it suffers from slow mass and electron transfer during applications. Herein, crumpled Co3O4 and Co3O4/reduced graphene oxide (rGO) with tunable 2D-in-3D structures were prepared by combining spray pyrolysis with a graphene oxide (GO) template. The 2D Co3O4 nanoplates were interconnected with each other to form a 3D ball with many wrinkles, resulting in defect enrichment on the abundant boundaries of the nanosheets, which provided more active sites for catalytic reactions. In addition, the unique 2D-in-3D structure allowed fast mass transfer and structural stability. Furthermore, the assembled structure could be understood as being composed of uniformly distributed oxygen-containing functional groups pinning metal cations on the GO surface through electrostatic interaction, and the 2D structure of the GO enabled the in situ converted Co3O4 to grow along the GO surface with excellent dispersion. Taking advantage of the above, the Co3O4/rGO balls demonstrated an excellent oxygen evolution reaction performance, an overpotential of 298 mV at a current density of 10.0 mA cm−2 and a current density of 115.9 mA cm−2 at the overpotential of η = 500 mV.

Synthesis and Electrochemical Study of Cobalt Based Nanostructured Catalysts for Energy Applications

The development of efficient electrocatalysts for the oxygen evolution reaction (OER) is an enduring challenge toward the commercialization of electrochemical technologies such as water electrolysis and solar to fuel production. Although noble metal based electrode materials (e.g., Pt, IrO2, and RuO2 etc.) are active catalysts for the OER, their cost-effectiveness, scarcity and long-term stability have hindered the development of electrochemical commercial applications. In addition, there is a great interest in the design of cost-effective and efficient catalysts for the oxygen reduction reaction (ORR) for the creation of clean energy technologies. In this presentation, we will report on the synthesis of one-dimensional Co3O4 nanorods, two-dimensional nanosheets, and three-dimensional nanocubes. The formed 1D, 2D, and 3D Co3O4 were systematically probed using a structure sensitive electrochemical OER, revealing that the 2D nanosheets exhibited higher catalytic activities in contrast to the 1D and 3D Co3O4, due to its high electrochemically active surface area and rich oxygen deficiencies. In addition, nanostructured nickel cobalt metal oxides with different composition were synthesized and studied for oxygen reduction. The effect of the composition, morphology, and active sites of the formed cobalt based nanomaterials on their catalytic activity will be discussed.

Development of 3-dimensional Co3O4 catalysts with various morphologies for activation of Oxone to degrade 5-sulfosalicylic acid in water

Since 5-sulfosalicylic acid (SFA) has been increasingly released to the environment, SO4−-based oxidation processes using Oxone have been considered as useful methods to eliminate SFA. As Co3O4 has been a promising material for OX activation, the four 3D Co3O4 catalysts with distinct morphologies, including Co3O4-C (with cubes), Co3O4-P (with plates), Co3O4-N (with needles) and Co3O4-F (with floral structures), are fabricated for activating OX to degrade SFA. In particular, Co3O4-F not only exhibits the highest surface area but also possesses the abundant Co2+ and more reactive surface, making Co3O4-F the most advantageous 3D Co3O4 catalyst for OX activation to degrade SFA. The mechanism of SFA by this 3D Co3O4/OX is also investigated and the corresponding SFA degradation pathway has been elucidated. The catalytic activities of Co3O4 catalysts can be correlated to physical and chemical properties which were associated with particular morphologies to provide insights into design of 3D Co3O4-based catalysts for OX-based technology to degrade emerging contaminants, such as SFA.

Non‐enzymatic glucose sensor based on three‐dimensional hierarchical Co 3 O 4 nanobooks

A new non-enzymatic glucose sensor is demonstrated successfully, based on three-dimensional (3D) hierarchical Co3O4 nanobooks (Co3O4 NBs). The 3D hierarchical Co3O4 NBs are assembled with porous and high crystalline 2D Co3O4 nanosheets. The electrochemical measurements reveal that the device exhibits outstanding performance for glucose detection, achieving a maximal sensitivity of 1068.85 μA mM−1cm−2 with a high R 2 of 0.9836, a low detection limit of 7.94 μM with a signal-to-noise of 3 and wide linear range up to 6 mM. The results demonstrate that the non-enzymatic glucose sensor can respond swiftly and selectively to glucose due to the high electrocatalytic activity of the 3D hierarchical Co3O4 NBs. The sensor also shows its high sensitivity and selectivity in detecting glucose in blood serum, confirming the practical application of the device with appealing accuracy.

Unique electrochemical system for in situ SO4[rad]− generation and pollutants degradation

Sulfate-based electrochemical advanced oxidation is of rising importance for pollutant removal, however, adscititious sulfate has adverse effects on water salinity. A novel electrochemical system which could exploit the existed SO42− for in situ generation of SO4− was successfully constructed with boron doped diamond (BDD) anode and hierarchical 1D Co3O4 nanowire array cathode. The in situ electrochemical electron paramagnetic spectroscopy and titration were used to study the positive correlation between the increase of sulfate radicals (SRs) and the efficient activation of peroxydisulfate (PDS) by hierarchical 1D Co3O4 nanowire array cathode. Electrochemical impedance and X-ray photoelectron spectroscopy revealed that the efficient activation of PDS by the Co3O4 cathode was derived from the excellent electron transport capability of the 1D nanostructure, and the electric field accelerates the reduction of Co(III). The novel hierarchical 1D Co3O4 nanowire array cathode can completely degrade dibutyl phthalate in 45% less time with 38% less energy compared to a traditional graphite cathode without the requirement of extra chemicals. The possible mechanism of anodic PDS accumulation and cathodic SRs generation was firstly revealed, and this advanced electrochemical oxidation system provides a good reference for the in situ sustainable remediation in sulfate-containing water.

Controllable synthesis of 3D hierarchical Co3O4 catalysts and their excellent catalytic performance for toluene combustion

Three-dimensional (3D) hierarchical Co3O4 catalysts with different morphologies are promising materials for the catalytic oxidation of toluene due to their high activity and relatively low costs. It is widely reported that the catalytic performance of Co3O4 catalyst for VOCs abatement highly depend on its mainly exposed crystal plane. Therefore, the morphology-controlled preparation of Co3O4 with preferentially exposed highly reactive plane plays crucial role in determining the catalytic activity of Co-based catalyst. In this work, we reported a facile and morphology-controlled synthesis of 3D Co3O4 catalysts with different morphologies and preferentially exposed planes. The best catalyst, the S-160 sample with the dominantly exposed {1 1 0} planes, exhibited a high catalytic activity for the total oxidation of toluene achieving a toluene conversion of T50% at 234 °C, which was 17 °C lower than that of the U sample with the mainly exposed {1 1 1} planes. The superior catalytic performance of the S-160 sample could be attributed to its specifically exposed highly reactive {1 1 0} planes, rich Oads species, good redox property as well as highly defective structure. In addition, the S-160 sample showed a stable activity during 100 h test, indicating its great potential for practical application for toluene oxidation.

Mechanically robust 3D hierarchical electrode via one-step electro-codeposition towards molecular coupling for high-performance flexible supercapacitors

Flexible solid-state supercapacitor (FSSC) is one of the most promising energy devices for wearable and portable electronics due to the advantages of high energy/power density, outstanding flexibility, good mutual compatibility and good safety. However, the serious performance decay of FSSCs caused by the structure and shape deformation of the devices is still a remaining challenge. Here, we report a high-performance FSSC with well-designed 3D Co3O4 nanowires @ MnO2-PPy hybrid nanoflake electrode made by a facile and effective one-step electro-codeposition method. To form a 3D skeleton, Co3O4 nanowires are vertically grown on carbon fibers, which improves the surface area and mass loading of pseudocapacitive materials. More importantly, it is also beneficial to avoid structure collapse during the bending, folding or twisting. Furthermore, MnO2-PPy nanoflakes grown on Co3O4 nanowires are capable to achieve the ultra-high surface area, fast electron/ion transport pathways and high utilization efficiency of the active materials. The specific capacitance of the constructed FSSC is as high as 215 F g−1 at the current density of 0.5 A g−1. The high energy density (41.3 Wh kg−1) and power density (4348 W kg−1) with a high capacitance retention of 93.0% after 1000 bending and twisting cycles are also achieved, indicating that it has a great potential for practical application in wearable and portable electronics.

In situ growth of metal organic frameworks derived hierarchical hollow porous Co3O4/NiCo2O4 nanocomposites on nickel foam as self-supported flexible electrode for methanol electrocatalytic oxidation

Most of the metal organic frameworks (MOFs) derived metal oxides are powdery, which cannot be directly used for electrocatalysis. In this report, zeolitic imidazole framework-67 (ZIF-67) derived hollow porous Co3O4 nanospindle arrays were in situ grown on nickel foam (NF) substrate (NF/Co3O4) and used as 3D skeleton. Cobalt nickel-aspartic acid coordination precursors (CoNi-Asp) derived NiCo2O4 nanotubes were in situ grow on the NF/Co3O4 3D skeleton to formed the hierarchical hollow porous self-supported flexible NF/Co3O4/NiCo2O4 electrode, which can be directly used for methanol electrocatalytic oxidation. The 3D Co3O4 skeleton can not only afford more surface area and strong adhesion for the in situ growth of NiCo2O4 nanotubes but also enhance the activity of NiCo2O4. More strikingly, the NF/Co3O4/NiCo2O4 exhibited good flexibility, which have potential application in flexible direct methanol fuel cell (DMFC).

Silver nanoparticles entrapped cobalt oxide nanohairs/electrospun carbon nanofibers nanocomposite in apt architecture for high performance supercapacitors

The development of composite materials in designed architectures in nanoscale level has been an intriguing research approach for diverse applications. Here, we report synthesis of a ternary nanocomposite of mesoporous cobalt oxide nanohairs, silver nanoparticles and electrospun carbon nanofibers sheet (3D Co3O4–Ag@CNFs) in a novel and apt 3D architecture by cost-effective electrospinning, hydrothermal cum post modification approaches for high performance supercapacitors (SCs). Conditions for controlled growth of constituents and their electrochemical significance have been discussed. The optimized nanocomposite, as a free standing electrode, exhibits a high specific capacitance of 1880 F g−1 at a current density of 2 A g−1 which is, possibly, the highest value reported for CNFs based Co3O4 composites. The assembled asymmetric supercapacitor device exhibits a high energy density of 53.8 W h kg−1 at a high power density of 797.9 W kg−1 with notable cyclic life. The results recommend the prepared nanocomposite sheet as an efficient electrode for high performance SCs.

Self-assembled 3D NixCo3-xO4 pseudocube superstructure as potential anode material for Li-Ion batteries

Self-assembled 3D NixCo3-xO4 pseudocube superstructure was successfully synthesized through a facile solvothermal strategy followed by a calcination process. Structure analyses shows that the mesoscopic 3D pseudocube superstructures are stacked by mesoporous nanoflakes with tiny nanoparticles as basic unit, as an anode material for Li-Ion Batteries, such a hierarchical structure can greatly buffer the volume expansion and effectively shorten lithium ion diffusion distance. Comparing with the 1D NiCo2O4 nanorods and 2D Co3O4 nanoflakes synthesized via changing the synthesis parameters, it conclude that the nickel leach process plays a key role in formation of this unique morphology and a mechanism is proposed. As expected, the 3D NixCo3-xO4 pseudocube exhibits the most impressive lithium storage performance, delivering a high reversible capacity of 1225 mA h g−1 after 200 cycles at 200 mA g−1, and even at high current of 4000 mA g−1, it still delivers a specific capacity of 645 mA h g−1. These results suggest a promising application for advanced energy storage units.

Three-dimensional plasmonic photoanode of Co3O4 nanosheets coated onto TiO2 nanorod arrays for visible-light-driven water splitting

In this work, we report for the first time a plasmonic photoanode by decorating Au nanoparticles (NPs) onto two-dimensional (2D) Co3O4 nanosheets (NSs)/one-dimensional (1D) TiO2 nanorod arrays (NRAs) (Au/Co3O4/TiO2-NRAs) for enhanced visible-light photoelectrochemical (PEC) water splitting. In this plasmonic photoanode, TiO2 NRAs act as an electron acceptor, plasmonic Au NPs and hierarchical Co3O4 NSs serve as visible-light harvesters. Light absorption shows that Au/Co3O4/TiO2-NRAs heterojunction architectures exhibit greatly improved ability to harvest visible light due to the surface plasmon resonance (SPR) absorption of Au NPs and visible light harvesting ability of Co3O4 NSs. Spectroscopic measurements demonstrate that a type II band alignment is formed between Co3O4 and TiO2. Benefiting from the SPR effect, type II band alignment and novel hierarchical architecture, plasmonic Au/Co3O4/TiO2-NRAs photoanode shows remarkably enhanced visible-light PEC water splitting activity compared with Co3O4/TiO2-NRAs and pristine TiO2-NRAs photoanodes. Photocurrent density achieved by plasmonic photoanode is 37 and 1.2 times higher than those of TiO2-NRAs and Co3O4/TiO2-NRAs photoanodes, respectively. This work provides a promising strategy to highly enhance visible-light PEC water splitting activity of wide band-gap semiconductor-based photoelectrode materials.

Surfactant-assisted synthesis of ultrathin two-dimensional Co3O4 nanosheets for applications in lithium-ion batteries and ultraviolet photodetector

Ultrathin two-dimensional (2D) Co3O4 nanosheets were prepared by surfactant-assisted self-assembly method. We demonstrate a high reversible capacity and an excellent rate capability of ultrathin 2D Co3O4 nanosheets as anodes in Li ion batteries. At a current density of 100 mA g−1, the nanosheets maintain an extraordinary capacity of 1868.6 mA h g−1 after 30 discharge/charge cycles, and nearly 100% capacity retention. When the current is increased to 400 mA g−1, 112% of the capacity can be retained. With their ease of large area synthesis and superior electrochemical properties, the 2D Co3O4 nanosheets will be interesting for practical Li ion batteries. Additionally, 2D Co3O4 nanosheets also showed both high stability and reproducibility as ultraviolet photodetector.