NiCo2O4 Nanowires Research Articles

Plasma-engineering of Pt-decorated NiCo2O4 nanowires with rich oxygen vacancies for enhanced oxygen electrocatalysis and zinc-air battery performance

The development of low-cost and efficient bifunctional catalysts is of great importance for the advancement of high-performance rechargeable zinc-air batteries. In this study, we present a composite material comprising Pt-decorated NiCo2O4 nanowires enriched with abundant oxygen vacancies, designed as an excellent bifunctional electrocatalyst for both the oxygen evolution reaction and the oxygen reduction reaction. The introduction of Pt atoms and oxygen vacancies onto the NiCo2O4 nanowires was achieved with the assistance of plasma treatment. This approach resulted in a catalyst with a greater number of active sites, enhanced surface conductivity and significantly improved electrocatalytic activity compared to the original NiCo2O4 nanowires. Moreover, the zinc-air battery based on this composite catalyst exhibits a narrow charge/discharge voltage gap and superior stability, which is better than batteries employing commercial noble-metal-based catalysts. This work provides a rational strategy for the construction of high-active and cost-effective Pt-based electrocatalysts.

Remarkable chemical adsorption and catalysis of 3D self-supporting Zn-doped NiCo2O4 nanowires for high-performance lithium-sulfur batteries

Lithium-sulfur batteries are one of the most potential next-generation energy storage systems with high theoretical energy density and low cost. However, the lithium polysulfides (LiPSs) dissolution and shuttle effect limit their commercial application. Herein, the Zn-doped NiCo2O4 nanowires grown on carbon cloth (ZNCOCC) are prepared by hydrothermal method and as sulfur host. ZNCO nanowires consisting of stacked nanoparticles and abundant mesopores were grown vertically on carbon fibers. The mesoporous structure of ZNCOCC provides more space to accommodate sulfur and its volume change during charging and discharging, is conducive to electrolyte infiltration and maintains strong adsorption of LiPSs to ensure fast ion transport kinetics. The ZNCOCC displays higher Co3+/Co2+ and Ni3+/Ni2+ ratio compared to NCOCC, and the high-valent metal cations can provide more unsaturated electron orbitals for S binding, causing high adsorption of LiPSs. Density functional theory calculations demonstrate that the Zn doping significantly reduces the band gap, improves the conductivity and increases the LiPSs adsorption energy of NCO. The ZNCOCC/Li2S8 displays a high specific capacity of 1184 mAh g−1 (0.1 C) and a low decay of 0.07 %/cycle after 500 cycles (2 C). This research reveals the rational design of a doped bimetal oxide nanostructure for the improvement of lithium-sulfur batteries.

Oxygen Vacancy-Induced Low-Valence reactive species enabling High-Efficient nonenzymatic glucose detection

NiCo2O4 (NCO), a typical spinel-type transition metal oxide, emerges as a promising candidate for non-electroenzymatic glucose sensors because of its stable structure and low overpotential. However, the practical applications of NCO are hindered by its limited intrinsic activity for glucose detection. Herein, we intentionally incorporated low-valence redox species into NCO nanowires by modulating the oxygen vacancies (VO-NCO NWs), thereby facilitating glucose oxidation reactivity. The concentration of low-valence species increases with the generated oxygen vacancies, which enriches the reactive redox species and enhances the intrinsic electrical conductivity, thereby improving the catalytic activity. Consequently, the optimized VO-NCO NWs exhibit highly efficient glucose detection with high sensitivity up to 19.65 mA·mM−1·cm−2, which is 4.6 times higher than that of the pristine NCO NWs, as well as a low limit of detection (LOD) of 0.15 μM. Furthermore, a flexible miniaturized three electrode (FMTE) assembled with optimized VO-NCO NWs provides a high sensitivity of 15.89 mA·mM−1·cm−2 and a low LOD of 0.18 μM in synthetic sweat. Under various bending conditions, the FMTE demonstrates good mechanical flexibility, with no discernible alterations in the response current. These findings provide a promising protocol for the dynamic monitoring of sweat composition to reveal human physiological health status.

Electron-interactive 1D porous vertical NiCo2O4 nanowire and 3D N-doped graphene aerogel enable high hydroxyl-ion adsorption capacity for superior energy storage

Supercapacitors are a kind of highly efficient energy-storage device with long cycle life and high power density, however, their specific capacitance is insufficient for further application and development. In this work, a novel composite with one-dimensional (1D) NiCo2O4 nanowire arrays (NiCo2O4-NWA) vertically supported on three-dimensional (3D) nitrogen-doped graphene aerogel (NGA) is designed and facilely realized by hydrothermal reaction and thermal treatment. The NiCo2O4 nanowires, with length of ∼1 μm and diameter of ∼25 nm, display a porous structure and are regularly arranged on both sides of the sheets in nitrogen-doped graphene aerogel. The aerogel-supporting NiCo2O4 nanowires demonstrate a remarkably high specific capacitance of 2742 F g−1 at 1 A g−1, and an outstanding cyclic stability with capacitance retention of 90% even after 10,000 cycles at 80 A g−1. The density functional theory calculation shows the narrow band gap (0.32 eV) and strong electronic interaction and hydroxyl-ion adsorption effect of NiCo2O4 supported on NGA, resulting in superior specific capacitance and energy storage performance. The 3D nitrogen-doped graphene aerogel supporting 1D nanowire arrays represent a promising high-performance electrode material for application in the supercapacitors and other electrochemical energy-conversion and storage equipment.

NiCo2O4 Nanowires Immobilized on Nitrogen-Doped Ti3C2Tx for High-Performance Wearable Magnesium-Air Batteries.

Flexible magnesium (Mg)-air batteries provide an ideal platform for developing efficient energy-storage devices toward wearable electronics and bio-integrated power sources. However, high-capacity bio-adaptable Mg-air batteries still face the challenges in low discharge potential and inefficient oxygen electrodes, with poor kinetics property toward oxygen reduction reaction (ORR). Herein, spinel nickel cobalt oxides (NiCo2O4) nanowires immobilized on nitrogen-doped Ti3C2Tx (NiCo2O4/N-Ti3C2Tx) are reported via surface chemical-bonded effect as oxygen electrodes, wherein surface-doped pyridinic-N-C and Co-pyridinic-N moieties accounted for efficient ORR owing to increased interlayer spacing and changed surrounding environment around Co metals in NiCo2O4. Importantly, in polyethylene glycol (PVA)-NaCl neutral gel electrolytes, the NiCo2O4/N-Ti3C2Tx-assembled quasi-solid wearable Mg-air batteries delivered high open-circuit potential of 1.5V, good flexibility under various bent angles, high power density of 9.8mW cm-2, and stable discharge duration to 12h without obvious voltage drop at 5mA cm-2, which can power a blue flexible light-emitting diode (LED) array and red smart rollable wearable device. The present study stimulates studies to investigate Mg-air batteries involving human-body adaptable neutral electrolytes, which will facilitate the application of Mg-air batteries in portable, flexible, and wearable power sources for electronic devices.

Facile synthesis of NiCo2 O4/rGO nanowire array electrodes for supercapacitor cathodes

In this study, NiCo2O4/rGO nanowire arrays (NWAs) were effectively synthesized, and these arrays were subsequently employed as components in supercapacitors. The phase structure of the materials was analyzed using X-ray diffraction spectroscopy, and the morphology of the materials was observed by scanning and transmission electron microscopy. By comparing with NiCo2O4 nanowire arrays without graphene oxide, it was found that the surface of NiCo2O4 arrays grown directly on nickel foams had a large number of accumulations, whereas the surface agglomerations of NiCo2O4/rGO nanowire arrays complexed with reduced graphene oxide were significantly improved. The NiCo2O4/rGO electrode with improved agglomeration phenomenon shows better performance. The specific capacitance of NiCo2O4/rGO NWAs is 2311 F·g-1 at 1 A·g-1 and remains at 1211 F·g-1 even at 50 A·g-1. In addition, the capacitance retention of this material could reach 83.5 % after 3,000 cycles at 10 A·g-1, demonstrating excellent multiplicative performance and cycling stability.

Dual efficiency enhancement in overall water splitting with defect-rich and Ru atom-doped NiFe LDH nanosheets on NiCo2O4 nanowires

The development of layered double hydroxides (LDHs) as bifunctional catalysts for efficient overall water splitting by controlling the composition and structure of the material remains challenging. In this study, defect-rich and Ru-doped NiFe LDH nanosheet shells on NiCo2O4 (NCO) nanowires were successfully synthesized using a hydrothermal method, followed by alkaline etching. The resulting def-Ru-NiFe LDH/NCO (def = defects) catalyst exhibited remarkable catalytic activity with overpotentials of 122 and 225 mV for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, at a current density of 10 mA cm−2. Density functional theory calculations demonstrated that atomic vacancy defects and the rational incorporation of Ru single atoms in def-Ru-NiFe LDH/NCO induced the regulation of the electronic structure and optimized the adsorption energies, thus enhancing the OER and HER performances. Particularly, an electrolyzer utilizing def-Ru-NiFe LDH/NCO exhibited exceptional performance, achieving cell voltages of 1.58 and 1.46 V in 1 M KOH at 25 and 75 °C, respectively. Moreover, the catalyst exhibited outstanding stability during 60 h of operation at a high applied voltage and temperature (75 °C). These results highlight the potential of def-Ru-NiFe LDH/NCO for hydrogen production.

Multi‐Hierarchical Heterostructure NiCo2O4/ZnCo2O4/CC Anode for Fast and Stable Lithium Storage

AbstractTransition metal oxides, especially bimetal oxides, are considered as one of the most promising anode materials for high‐performance lithium‐ion batteries (LIBs) due to their ultra‐high theoretical capacity. However, it is difficult to achieve fast charging at high rates due to the issues of poor electrical conductivity, large volume expansion, and poor reaction kinetics. The design of advanced nanostructured anode materials is very important to boost lithium storage performance. Herein, the multi‐hierarchical heterostructure material NiCo2O4/ZnCo2O4/Carbon Cloth (NCO/ZCO/CC) including carbon cloth substrate, ZnCo2O4 nanosheets, and NiCo2O4 nanowires is prepared as a binder‐free anode for LIBs. Benefiting from the special hierarchical nanostructure and the synergistic interaction of the component, the as‐prepared NCO/ZCO/CC anode material exhibits good electrical conductivity, structural stability, and electrochemical kinetics, which can provide a high reversible areal capacity of 2.55 mAh cm−2 at 2 mA cm−2 after 200 cycles. At a high current density of 5 mA cm−2, the NCO/ZCO/CC electrode only takes about 20 min to fully charge and it can still reach a capacity of 1.50 mAh cm−2 with a capacity retention of 86.2% after 400 cycles, revealing the potential for fast charging at high rates.

Plasma-Engineering of Oxygen Vacancies on NiCo2O4 Nanowires with Enhanced Bifunctional Electrocatalytic Performance for Rechargeable Zinc-air Battery.

Designing an efficient, durable, and inexpensive bifunctional electrocatalyst toward oxygen evolution reactions (OER) and oxygen reduction reactions (ORR) remains a significant challenge for the development of rechargeable zinc-air batteries (ZABs). The generation of oxygen vacancies plays a vital role in modifying the surface properties of transition-metal-oxides (TMOs) and thus optimizing their electrocatalytic performances. Herein, a H2/Ar plasma is employed to generate abundant oxygen vacancies at the surfaces of NiCo2O4 nanowires. Compared with the Ar plasma, the H2/Ar plasma generated more oxygen vacancies at the catalyst surface owing to the synergic effect of the Ar-related ions and H-radicals in the plasma. As a result, the NiCo2O4 catalyst treated for 7.5min in H2/Ar plasma exhibited the best bifunctional electrocatalytic activities and its gap potential between Ej = 10 for OER and E1/2 for ORR is even smaller than that of the noble-metal-based catalyst. In situ electrochemical experiments are also conducted to reveal the proposed mechanisms for the enhanced electrocatalytic performance. The rechargeable ZABs, when equipped with cathodes utilizing the aforementioned catalyst, achieved an outstanding charge-discharge gap, as well as superior cycling stability, outperforming batteries employing noble-metal catalyst counterparts.

Fabrication and Electrochemical Analysis of NiCo2O4@Ni-MOF Nanoarchitectonics Composites on Ni-Foam Substrate for Supercapacitor Electrodes

To produce the free-standing electrodes, a binder-free direct growth method was employed for electrode fabrication. A NiCo2O4@Ni-MOF (metal–organic framework) composite was synthesized using a one-pot hydrothermal method. Initially, a NiCo2O4 nanowire array was cultivated on Ni foam, serving as a connecting bridge to ensure robust adherence of the Ni-MOF to the substrate. The structures of NiCo2O4 nanowire arrays exhibit the capacity for numerous redox reactions. Hybridizing MOF with transition metal oxide (TMO) nanoarchitectures can significantly alleviate the small specific surface area and aggregation tendency of TMOs. The highest energy storage capacity was obtained when the ratio of nickel to terephthalic acid (TPA) was 4:1. NiCo2O4@Ni-MOF (Ni:[Formula: see text]:1) exhibited a high storage capacitance of 1700[Formula: see text]F/g. The integration of MOF with TMO nanoarchitectonics as materials for supercapacitor electrodes can enhance porous structure and facilitate diffusion during both charging and discharging processes.

Research on 3D network in-situ grown NiCo2O4 nanowire arrays construction and its energy storage performance

In this paper, NiCo2O4 nanowire arrays are synthesized on 3D NF skeleton by a one-step hydrothermal method and used as anode materials for lithium-ion batteries (LIBs). Dense nanowire arrays are grown in situ on NF skeleton, cross-linked and constructed into 3D network structure. As an anode, it exhibits excellent electrochemical properties. The initial discharge capacity of NiCo2O4/NF is as high as 1316 mAh g−1 at a current density of 0.2 A g−1, and the specific capacity of 790 mAh g−1 can be maintained after 200 cycles. And NiCo2O4/NF can also maintain a specific capacity of 580.37 mAh g−1 at a current density of 1 A g−1 in the rating performance. And transfer resistance after 200 cycles reduced by 53.5%,which shows a tendency to decrease during the reaction process and accelerates the rate of Li+ transfer, improved battery cycling performance. The excellent lithium storage performance is attributed to the high aspect ratio of the nanowires themselves and the stable 3D network structure, which not only facilitates the rapid transfer of substances and diffusion of Li+, but also alleviates the volume change during the charge/discharge cycle. The band gap of NiCo2O4 can be obtained as 0.671 eV by first nature principle calculation, the electrons readily jump from the valence band to the conduction band and have good conductivity. And the diffusion potential barrier is 0.4 eV, which is easily overcome in the experiment and facilitates the transport of lithium ions.

Electrochemical non-enzymatic urea sensing using polyvinylpyrrolidine derived highly electrocatalytic NiCo2O4 nanowires

Electrochemical non-enzymatic urea sensing using polyvinylpyrrolidine derived highly electrocatalytic NiCo2O4 nanowires

Self-sacrifice-template epitaxial growth of hierarchical MnO2@NiCo2O4 heterojunction electrode for high-performance asymmetric supercapacitor

Constructing three-dimensional (3D) hierarchical bimetallic pseudocapacitive materials with abundant opening channel and heterojunction structures is rather promising but still challenging for high-performance supercapacitors. Herein, a self-sacrifice-template epitaxial growth strategy was proposed for the first time to construct 3D hierarchical bimetallic pseudocapacitive material. By using this strategy, NiCo2O4 nanowires (NiCo2O4NW) arrayed randomly to form a porous shell via in-situ epitaxial growth fully enclosing a MnO2 tube core, forming multiple transport channels and nano-heterojunctions between MnO2 and NiCo2O4NW, which facilitates electron transfer, i.e. exhibiting high electronic conductivity than any single component. As a result of the self-sacrifice-template epitaxial growth method, special hollow tectorum-like 3D hierarchical structure with considerable inter-nanowire space and hollow interior space enables easy access of electrolyte to NiCo2O4NW surface and MnO2 core, thereby resulting in highly exposed redox active sites of MnO2 core and NiCo2O4NW shell for energy storage. Comprehensive evaluations confirmed MnO2@NiCo2O4NW was a supercapacitor electrode candidate, delivering a superior energy density of 106.37 Wh kg−1. Such performance can be ascribed to the synergistic coupling effect of 3D hierarchical tube and nano-heterojunction structures. The proposed self-sacrifice-template epitaxial growth strategy provides important guidance for designing high-performance energy storage materials.

Synthesis and Pseudocapacitive Performance of Ordered Mesoporous NiCo2O4 Nanowires

Synthesis and Pseudocapacitive Performance of Ordered Mesoporous NiCo2O4 Nanowires

MOFs-derived core-shell structured NiCo2O4NWs@Co3O4NPs for non-enzymatic glucose detection

Metal-organic frameworks (MOFs) exhibit many structural advantages, such as large specific surface area and abundant active sites, which make them promising candidates as electrode materials for non-enzymatic glucose sensors. In this work, using MOFs as templates, MOFs derived Co3O4 nanoparticles (NPs) were in-situ synthesized on the surface of NiCo2O4 nanowires (NWs), forming a self-supporting electrode based on nickel foam (NF), which was directly used for the detection of glucose. Because of the presence of MOFs derivatives and self-supporting structures, NF/NiCo2O4NWs@Co3O4NPs electrode exhibits good structural stability and high conductivity, which ensure the excellent electrocatalytic performance. The NF/NiCo2O4NWs@Co3O4NPs electrode shows prominent electrocatalytic performance toward glucose with a wide testing range (0.001–1.7 mmol/L), high sensitivity (8163.2 μA cm−2 mM−1), fast response time (within 1 s), high anti-interference ability and long-term stability. Further, the electrode was used to test different glucose levels in live mouse serum samples, showing acceptable reliability and high accuracy comparing with blood glucose meter test (medical test method). Thus, NF/NiCo2O4NWs@Co3O4NPs electrode with self-supporting core-shell nanostructure will be a promising candidate applied in non-enzymatic glucose sensors.

Nitrogen-doped NiCo2O4 nanowires on carbon paper as a self-supported air cathode for rechargeable Zn-air batteries

A noble-metal-free bifunctional electrocatalyst with outstanding activity and stability is of great importance for the development of rechargeable zinc-air batteries (ZABs). Herein, we employed a facile strategy to fabricate nitrogen-doped NiCo2O4 nanostructures on carbon paper as a binder-free air cathode for rechargeable ZABs. An optimized process of nitrogen plasma treatment has enhanced the electrical conductivity of the metal oxide and induced abundant active sites into the crystal structures, resulting in enhanced electrocatalytic activities toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Notably, mild plasma treatment leads to efficient N doping while the morphology and specific surface area of the catalyst both remain unchanged. The air cathode with NiCo2O4 doped with nitrogen in 2 min plasma treatment and integrated into a zinc-air battery with liquid electrolyte provided a small charge-discharge voltage gap and distinguished cycling stability superior to the air cathode with noble-metal catalyst counterparts. Furthermore, the solid-state zinc-air battery with this material displays excellent stability with just a small increase of the charge-discharge voltage gap over 20 h of operation. This work illustrates the promising potential of plasma treatment in the fabrication of high-performance catalysts.

Free-standing nanowires growing on ginkgo biloba as high areal capacity Li-ion battery anode at high and low temperatures

The low cost and special structure of biomass materials enable them to be applicable for many energy-storage systems. Here, we develop NiCo2O4 nanowires growing on carbonized ginkgo biloba to form free-standing anodes of Li-ion battery. The porous NiCo2O4 nanowires have a high capacity, and they are able to accommodate the expansion of volume in cycling. Low surface reaction barrier of the NiCo2O4/ginkgo biloba anode is confirmed by galvanostatic intermittent titration technique analysis. The NiCo2O4/ginkgo biloba anode displays recoverable rate-performance and good stability when cycling at different current densities, which remains 2.6 mAh cm−2 after 350 cycles at room temperature. The Coulombic efficiency is about 99 % under −10 °C at 1 mA cm−2, and the capacity remains 1.28 mAh cm−2 after cycling 200 times. Capacity keeps 1.83 mA cm−2 under 45 °C, exhibiting a good Li-storage performance. The NiCo2O4/ginkgo biloba anode displays a better cycling performance than NiCo2O4/nickel foam and NiCo2O4/carbon cloth. The cost-effective synthesis strategy provides extensible applications for metal oxide/ginkgo biloba-based composites. Growing other binary metal oxides on the carbonized ginkgo biloba is also achievable such as ZnCo2O4, indicating the developed composite system is promising for preparing other free-standing energy-storage composites.

The fabrication and characterization of ZnO/NiCO2O4 nanowires synthesized by a hydrothermal method

The main functional part of the supercapacitors and nanogenerators made up of various types of nanostructured materials. The contemporary devices have been manufactured employing different kinds of nanomaterials based on nanoflake and nanowire structures. These hierarchical materials show high efficiency on engineering electrodes for supercapacitors as well as piezoelectric for nanogenerators. Here, we have successfully synthesized NiCo2O4 nanowires on ZnO nanoflakes by applying two-step hydrothermal method which is absent similar analogous to date. The microscopic analysis has shown the uniform growth of NiCo2O4 nanowires on ZnO nanoflakes. This fabricated material might be used in above mentioned purposes in the future.

Au Nanoparticles-Modified NiCo₂O₄ Nanowires-Supporting Co₃O₄ Dodecahedron as High-Performance Nonenzymatic Glucose Sensor

A hierarchically nanostructured active material composed of nanoparticles, microsized dodecahedron, and nanowires (NWs) has been successfully fabricated and used for glucose oxidation, in which the NiCo2O4 NWs were grown in situ on the carbon paper (CP) and used for supporting the zeolitic imidazolate framework (ZIF-67)-derived Co3O4 dodecahedron, with the Au nanoparticles (Au-Np) being further electrodeposited on their surface (Au-Np/Co3O4/NiCo2O4 NWs/CP). The NWs effectively avoid the agglomeration of Co3O4, thus providing greater surface area for loading the Au nanoparticles. The introduction of Au can decrease the oxidation potential and enhance the catalytic current, which is beneficial for the electrocatalytic oxidation of glucose. The Au-Np/Co3O4/NiCo2O4 NWs/CP-based nonenzymatic glucose sensor exhibits good sensing performance, including high sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15.3~\mu \text{A}/\mu \text{M}$ </tex-math></inline-formula> /cm2, outstanding response/recovery times of 2.5/4.0 s (toward 180- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{M}$ </tex-math></inline-formula> glucose), good reproducibility, and excellent selectivity. Therefore, constructing a hierarchical nanocomposite is a promising strategy to develop a nonenzymatic electrochemical glucose sensor.

Responsive Ag@NiCo2O4 Nanowires Anchored on N-Doped Carbon Cloth as Array Electrodes for Nonenzymatic Glucose Sensing.

The development of responsive materials in a predictable manner is high on the list of the material industry's trends. In this work, responsive Ag@NiCo2O4 nanowires were, firstly, anchored on N-doped carbon cloth (NC) and, then, employed as array electrodes for a nonenzymatic glucose-sensing application. The results showed that the highly conductive NiCo2O4 nanowires supported Ag nanoparticles and exhibited high conductivity and electrocatalytic properties. The fully exposed crystalline planes of Ag nanoparticles provided more active surface sites. As a result, the assembled Ag@NiCo2O4-NC electrodes for the glucose-sensing evaluation delivered a selectivity of 2803 μA mM-1 cm-2 and a detection limit of 1.065 μM, which outperformed the literature-reported Ag- and NiCo2O4-based glucose-sensing catalysts.