Flower-like NiCo2O4 Research Articles

Suppressed conductive loss of flower-like NiCo2O4-wrapped flaky FeSiAl for excellent low-frequency microwave absorption

Flaky FeSiAl is a high potential absorbent for low-frequency microwave applications. However, impedance mismatching due to its excessively high complex permittivity presents a challenge. Herein, inspired by the surface modification strategy, flaky FeSiAl wrapped with flower-like NiCo2O4 (NiCo2O4@flaky FeSiAl) was developed via a hydrothermal method. The introduction of a surface NiCo2O4 insulating layer was expected to reduce the complex permittivity and increase the high complex permeability in the NiCo2O4@flaky FeSiAl composite. Subsequently, an excellent low-frequency microwave absorption performance was achieved. The designed NiCo2O4@flaky FeSiAl displayed a robust minimum refection loss (RL min) of −33.41 dB at 6.32 GHz and increased the effective absorption bandwidth (EAB, RL < −10 dB) to 4.08 GHz when the matching thickness was 1.6 mm. The enhanced low-frequency microwave absorption performance was mainly attributed to the improvement in impedance matching, which originated from the collaborative regulation of electromagnetic parameters. This study provides a promising approach for designing flaky FeSiAl-based composites and high-performance low-frequency microwave absorbents.

Floret assembly of NiCo2O4@Tailored nanostructured carbon support for oxygen evolution reaction in alkaline medium

The oxygen evolution reaction (OER) is a bottleneck in overall water splitting due to the involvement of the four-electron process and requires a high overpotential. This hinders the stability and durability of electrocatalysts over a longer period. Herein, we report flower-like NiCo2O4 decorated on carbon nanostructures synthesized using a one-pot wet chemical method as an OER electrocatalyst in an alkaline medium. The catalytic activities were characterized by various electrochemical measurements including linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and turnover frequency (TOF). 90 % NiCo2O4@rGO/f-MWCNT demonstrated a higher OER activity compared to stand-alone NiCo2O4, 90 % NiCo2O4@rGO, 90 % NiCo2O4@f-MWCNT and 80 % NiCo2O4@rGO/f-MWCNT.

Sweat lactate biosensor based on lactate oxidase immobilized with flower-like NiCo2O4 and carbon nanotubes

We design a portable and non-invasive lactate biosensor that can conveniently monitor lactate levels in real human sweat. The proposed biosensor is constructed through the immobilization of lactate oxidase (LOx) and horseradish peroxidase (HRP) on flower-like NiCo2O4 microspheres coupled with single-walled carbon nanotubes (SWCNTs). The synergistic effect between NiCo2O4 microspheres and SWCNTs can increase the conductivity and the active surface area of the electrode. Using ferrocene–methanol (FcMeOH) as the electron transfer mediator in buffer, the developed biosensor can detect lactate in a wide linear range of 0.1 mM to 30 mM with a detection limit of 39.9 µM under optimal conditions. Additionally, the biosensor exhibits excellent selectivity and stability. As proof of concept, the biosensor was applied to monitor lactate level in real human sweat samples, and the results were in good agreement with those obtained by high-performance liquid chromatography (HPLC) analysis. The lactate biosensor is cost effective and can be as a non-invasive alternative to blood analysis, which is suitable for rapid analysis of lactate levels in the fields of fitness, health monitoring and clinical diagnosis.

Flower-like NiCo2O4 spinel microspheres for efficient chlorine evolution under neutral conditions

Dimensional stability anodes (DSA), constructed using noble metal oxides like RuO2 and IrO2, is widely used in industrial chlorine production. The DSA electrode demonstrates exceptional chlorine evolution capabilities in acidic solutions and high-chloride concentrations. However, under neutral conditions, its chlorine evolution efficiency diminishes significantly. In this paper, a low-cost, high-efficiency 3D flower-like NiCo2O4 catalyst was fabricated that exhibits high catalytic activity in neutral sodium chloride solutions. The 3D flower-like NiCo2O4 catalyst exhibits good chlorine evolution efficiency, achieving 90 % at 30 mA/cm2 in NaCl solutions. Furthermore, it's chlorine evolution efficiency of the electrocatalyst surpasses that of commercial DSA electrode at various current densities, making it a highly promising candidate for electrocatalytic applications.

Nanoflower-like NiCo2O4 Composite Graphene Oxide as a Bifunctional Catalyst for Zinc-Air Battery Cathode.

Developing efficient bifunctional catalysts for nonprecious metal-based oxygen reduction (ORR) and oxygen evolution (OER) is crucial to enhance the practical application of zinc-air batteries. The study harnessed electrostatic forces to anchor the nanoflower-like NiCo2O4 onto graphene oxide, mitigating the poor inherent conductivity in NiCo2O4 as a transition metal oxide and preventing excessive agglomeration of the nanoflower-like structures during catalysis. Consequently, the resulting composite, NiCo2O4-GO/C, exhibited notably superior ORR and OER catalytic performance compared to pure nanoflower-like NiCo2O4. Notably, it excelled in OER catalytic activity of the OER relative to the precious metal RuO2. As a bifunctional catalyst for ORR and OER, NiCo2O4-GO/C displayed a potential difference of 0.88 V between the ORR half-wave potential and the OER potential at 10 mA·cm-2, significantly lower than the 1.08 V observed for pure flower-like NiCo2O4 and comparable to the 0.88 V exhibited by precious metal catalysts Pt/C + RuO2. The NiCo2O4-GO/C-based zinc-air battery demonstrated a discharge capacity of 817.3 mA h·g-1, surpassing that of precious metal-based zinc-air batteries. Moreover, charge-discharge cycling tests indicated the superior stability of the NiCo2O4-GO/C-based zinc-air battery compared to its precious metal-based counterparts.

Binderless synthesis of hierarchical, marigold flower-like NiCo2O4 films for high-performance symmetric supercapacitor

The facile and cost-effective chemical bath deposition method is employed for the binder-free synthesis of NiCo2O4 marigold flower-like nanostructures on a flexible stainless-steel substrate. Binderless and surfactant-free synthesis of NiCo2O4 films for supercapacitor application is a crucial part of this synthesis process. The effect of reaction times on the deposition of NiCo2O4 nanostructured films has been discussed briefly based on the electrochemical performance and surface morphology of films. The reaction time is varied as 2, 4, 6, and 8 h. The prepared films were analyzed by structural and morphological characterizations. The time-dependent significant change in morphology of NiCo2O4 films is discussed in detail. The development of the Marigold-like flowers from wheat grain-like nanostructures has been observed for increasing reaction time. The film deposited at 6 h reaction time (NCO-6 electrode) showed better specific capacitance of 1277 F/g at 5 mA/cm2, which retained about 95 % after 10,000 cycles. The NiCo2O4 film exhibited a 0.7 V potential window with the maximum energy and power density of 86 Wh/kg and 2333 W/kg, respectively. The fabricated aqueous symmetric device i.e., NCO//NCO showed energy density and power density of 16.4 Wh/kg and 275.5 W/kg, respectively. The fabricated device shows 90.5 % retention in performance after 5000 cycles. These results revealed that NiCo2O4 can be a better electrode material for energy storage devices.

Facile hydrothermal synthesis and fabrication of nickel cobalt oxide as an advanced electrode for electrochemical capacitors

The surface chemistry and decent morphology of electrode materials are highly desirable for high-performance energy storage/conversion devices. Bimetallic oxides especially nickel cobalt oxide (NCO) have gained substantial attention in energy storage/conversion devices owing to their exclusive electronic properties. Herein, flower-like nickel cobalt oxide (NiCo2O4) was prepared by a facile hydrothermal method for different reaction times. The properties of obtained samples were characterized through X-ray diffraction (XRD), EDS, field-emision scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). The cyclic voltammogram (CV), Galvanostatic changing discharging (GCD), and electrochemical impedance spectroscopy (EIS) were employed for the evaluation of the electrochemical performances of the resultant product. The flower-like NiCo2O4 electrode exhibits high areal capacity (392 mF cm−2 at 0.5 mA cm−2) and the electrode shows an energy density of about 9.1 µWh cm−2 at power density 102 µW cm−2. The excellent electrochemical performance of the fabricated supercapacitor offers good areal capacitance and energy density that exceeds several carbon-based materials.

Self-template synthesis of hollow flower-like NiCo2O4 nanoparticles as an efficient bifunctional catalyst for oxygen reduction and oxygen evolution in alkaline media

Abstract A method was proposed to synthesize hollow flower-like NiCo2O4 composed of porous nanosheets using a self-template approach. The unique structure is attributed to the synergistic effect of the Kirkendall effect and the Ostwald ripening mechanism. The sheet-like and porous structure endowed the material with a specific surface area of 137.1 m2 g−1 and a pore volume of 0.418 cm3 g−1. The distinctive structure and high-density active sites imparted excellent catalytic performance in oxygen reduction (ORR) and oxygen evolution (OER) reactions. Electrochemical tests showed that the limit current density of ORR reached 5.58 mA cm−2, comparable to that of the noble metal Pt/C (20 wt%). The overpotential of OER at a current density of 10 mA cm−2 was only 380 mV, significantly lower than that of the noble metal RuO2. These results indicate that the synthesized hollow flower-like NiCo2O4 has the potential to replace noble metals in ORR and OER catalytic applications.

The electromagnetic wave absorption composite of flower-like structure NiCo2O4 and Fe3O4 derived from low-temperature preparation method

The NiCo2O4@Fe3O4 composites with excellent electromagnetic wave absorption performance was prepared by the low-temperature (50 °C) co-precipitation method, avoiding the traditional high-temperature hydrothermal synthesis method. The specific surface area of the composite material was increased due to the combination of NiCo2O4 with 3D hierarchical flower-like structure and Fe3O4 with spherical structure, which is conducive to the full reflection and scattering of electromagnetic waves. The combination of typical magnetic material and excellent dielectric material could adjust the impedance matching value of the material and thus the absorption loss performance of electromagnetic wave was improved. The ε value of the dielectric material was larger than those of magnetic materials and the maximum reflection loss value appeared at the high frequency (the thickness is small), while the μ value of magnetic materials was larger than those of dielectric materials and the maximum reflection loss value generally appeared at low frequency (the thickness is large).The results showed that the maximum RL value reached −53.35 dB at about 13 GHz with the thickness of 2.0 mm and the effective absorption bandwidth was 4.4 GHz when the weight ratio (NiCo2O4:Fe3O4) of composite samples was 6:1. The excellent EMW absorption property was mainly due to the combination of NiCo2O4 and Fe3O4, which could achieve impedance matching to loss EMW by dielectric loss and magnetic loss.

Simple Preparation and Characterization of Hierarchical Flower-like NiCo2O4 Nanoplates: Applications for Sunset Yellow Electrochemical Analysis.

The current work was performed to construct a novel electrochemical sensing system for determination of sunset yellow via the modification of screen-printed graphite electrode modified with hierarchical flower-like NiCo2O4 nanoplates (NiCo2O4/SPGE). The prepared material (hierarchical flower-like NiCo2O4 nanoplates) was analyzed by diverse microscopic and spectroscopic approaches for the crystallinity, composition, and morphology. Chronoamperometry, differential pulse voltammetry, linear sweep voltammetry, and cyclic voltammetry were used for determination of the electrochemical behavior of sunset yellow. The as-fabricated sensor had appreciable electro-catalytic performance and current sensitivity in detecting the sunset yellow. There were some advantages for NiCo2O4/SPGE under the optimized circumstances of sunset yellow determination, including a broad dynamic linear between 0.02 and 145.0 µM, high sensitivity of 0.67 μA/(μM.cm2), and a narrow limit of detection of 0.008 μM. The practical applicability of the proposed sensor was verified by determining the sunset yellow in real matrices, with satisfactory recoveries.

Flower-like NiCo2O4 nanoflake surface covered on carbon nanolayer for high-performance electro-oxidation of non-enzymatic glucose biosensor

The high porous nickel cobalt oxide flower-like nanoflake (NF) structured materials with (C/NiCo2O4-1 and C/NiCo2O4-2) and without (NiCo2O4) the presence of dopamine as a carbon source were synthesized by a simple hydrothermal method for non-enzymatic glucose sensing. The structural and morphological characteristics of as-synthesized materials were confirmed using transmission electron microscopy, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. The transmission electron microscopy analysis of C/NiCo2O4-1 NF materials reveals that a flower-like structure of NiCo2O4 NF covered over the surface of carbon in the hybrid composite. The electrochemical properties of as-synthesized material were determined from cyclic voltammetry and chronoamperometry analysis. Among the NiCo2O4 NF, C/NiCo2O4-1 NF, and C/NiCo2O4-2 NF structured materials, the C/NiCo2O4-1 NF exhibits a remarkable electrochemical performance toward glucose oxidation with a high linear range (0.0001–15.28 mM), high-sensitivity (779.35 μA mM−1 cm−2), and ultra-low detection (86 μM). Moreover, the C/NiCo2O4-1 NF electrode indicates excellent recoveries of glucose in human blood serum samples. The obtained results illustrate that the good features of C/NiCo2O4-1 NF electrode materials have the potential to be used as a non-enzymatic glucose sensor.

Achieving electromagnetic wave absorption capabilities by fabrication of flower-like structure NiCo2O4 derived from low-temperature co-precipitation

In this work, The NiCo2O4 with 3D hierarchical multilayer flower-like structure was prepared by the low-temperature (55 °C) co-precipitation method combined with the calcination process, avoiding the traditional high-temperature hydrothermal synthesis method. The prepared flower-like NiCo2O4 with a large specific surface area was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and automatic surface area and porosity analyzer (BET) and vector network analyzer (VNA). A novel evaluation approach was proposed to evaluate the electromagnetic wave (EMW) absorbing properties of various samples (different calcination temperatures), which was to defined the ΔS as the area enclosed by the curve when the reflection loss (RL) value was less than −10. In order to take the material thickness into account, and then the effective reflection loss (RLE) value was defined ΔS/d to measure the electromagnetic wave (EMW) loss capability of the different samples. The results showed that NiCo2O4 exhibited excellent EMW absorption effect when the calcination temperature was 400 °C, and the maximum RL value reached −43.17 dB at 14.32 GHz with the thickness of 1.5 mm and the effective absorption bandwidth (fe) was 4.48 GHz (12.08 GHz–16.56 GHz). The excellent EMW absorption property was mainly due to NiCo2O4 with particular porous flower-like structure, which could achieve impedance matching to loss EMW by dielectric loss and magnetic loss.

Hierarchical NiCo2O4/CuO-C nanocomposite derived from copper-based metal organic framework and Ni/Co hydroxides: Excellent electrocatalytic activity towards methanol oxidation

In this work, a metal-organic framework (Cu-MOF) and two none-precious metals (Ni and Co) are used for preparation of a highly efficient electrocatalyst for methanol oxidation reaction. Nickel/cobalt hydroxides are coprecipitated on Cu-MOF in alkaline solution. The composite is then calcinated at 350 °C to obtain a carbonaceous framework and flower-like NiCo2O4 deposits (CuO-C/NiCo2O4). The obtained composite is characterized by several methods (XRD, XPS, FT-IR, SEM, TEM, and electrochemical techniques). The presence of metal oxides CuO and NiCo2O4 in the prepared electrocatalyst is confirmed by XRD and XPS methods. CuO-C/NiCo2O4 shows excellent catalytic activity towards MOR in alkaline solution (NaOH, 1 M). The electrocatalytic activity of CuO-C/NiCo2O4 is compared to stepwise composites (CuO-C/NiO, CuO/CoO, NiCo2O4) and commercial Pt/C, which confirms the superiority of the proposed catalyst in terms of current density (208.1 mA cm−2) and amperometric stability (7000 s) in methanol oxidation reaction. The observed benefits are attributed to synergistic effects between the porous conductive carbonaceous material and multi transition-metal oxides (CuO and NiCo2O4).

NiCo2O4@PPy concurrently as cathode host material and interlayer for high-rate and long-cycle lithium sulfur batteries

The large-scale practical application of cost-efficient lithium sulfur (Li–S) battery with high energy density is impeded due to the shuttle effect and torpid kinetics of polysulfides. Hence, it is significant for Li–S battery to solve these disadvantages to boost the electrochemical performances and facilitate the popularization in various fields. Herein, we synthesized a conductive NiCo2O4@PPy micro-flower-like material via hydrothermal technique followed by subsequent in-situ vapor phase polymerization, and the material was assembled into Li–S batteries to obtain satisfactory electrochemical performances. Flower-like NiCo2O4 expedites the conversion of polysulfides through both physical adsorption and chemical anchoring. Polypyrrole can efficaciously confine polysulfides shuttling, increase the conductivity and concurrently promote lithium ions diffusion. NiCo2O4@PPy is simultaneously served as the effective cathode material and multi-functional interlayer for anchoring-catalyzing polysulfides, which can exhibit a satisfying initial capacity of 1588 mAh g−1 at 0.1C, and the average coulomb efficiency is 95.2%. The highest discharge specific capacity of 740 mAh g−1 is displayed at 2C and the capacity decay rate is 0.107% per cycle after 400 cycles. NiCo2O4@PPy composite is a favorable sulfur host material intimated by these new results, and it is also a competent candidate of interlayer in high-performance Li–S batteries.

Fabrication of the flower-like NiCo2O4 @ Ni(OH)2/NiOOH composites supported on nickel foam by the green solvent dimethyl sulfoxide with high performance in supercapacitor and hydrogen evolution reaction

Because of their low synthesis cost, large specific surface area, and good energy storage performance, microporous metal-based composites have been widely used in supercapacitors and the hydrogen evolution reaction (HER). Flower-like Ni foam@ (@, coating) NCo2O4@Ni(OH)2/NiOOH (NF@NCO@NOH) composites were synthesized through a simple solvent-controlled method and following an electrochemical deposition process. The as-synthesized composites benefit from high specific area, a hierarchical porous structure, and the synergistic effect of Ni and Co, showing a high area-specific capacitance of 23.75 F cm−2 at a continuous current of 5 mA cm−2. The assembled asymmetric supercapacitor exhibits an energy density of 125 Wh kg−1 at a power density of 6.24 kW kg−1. Furthermore, 84.1% of the capacity was retained after 10,000 cycles, suggesting the sample has excellent electrochemical stability. Moreover, an overpotential of 162 mV at a current density of 10 mA cm−2 and a Tafel slope of 95 mV dec−1 were obtained in the HER measurement, indicating that the as-synthesized flower-like electrode material possesses potential applications in the HER.

Alkaline aqueous rechargeable Ni-Fe batteries with high-performance based on flower-like hierarchical NiCo2O4 microspheres and vines-grapes-like Fe3O4-NGC composites

Aqueous rechargeable secondary Ni-Fe batteries have attracted extensive attention due to low cost, relatively outstanding safety and high energy density. However, the nickel/iron electrode materials also suffer from poor conductivity and week cycling performance. In this study, we have modified the CNT-S-PEGm as electron transport channels with methoxypolyethylene glycol (mPEG) via thiol-ene click to further provide more reactive sites, and then prepared the cathode materials of 3D flower-like hierarchical microspheres of NiCo2O4-CNT-S-PEGm composites by a solvothermal method. The as-prepared cathode materials reveal the capacity of 195.7 mAh g−1 at 0.5 A g−1. In addition, the anode materials of vines-grapes-like Fe3O4-N-rGO-CNT>N-PEGm (Fe3O4-NGC) ternary composites have been prepared in a typical hydrothermal method. Notably, the promising Fe3O4-NGC anode materials exhibit the highest capacity of 308.1 mAh g−1 at 1 A g−1. Due to such excellent attributes, the alkaline aqueous rechargeable Ni-Fe batteries of NiCo2O4-CNT-S-PEGm//Fe3O4-NGC have been successfully fabricated. Moreover, the as-assembled device displays the high capacity of 77.8 mAh g−1 at 0.5 A g−1 and the energy density of 64.4 Wh kg−1 at 414 W kg−1 for potential energy storage.

Size-controllable porous flower-like NiCo2O4 fabricated via sodium tartrate assisted hydrothermal synthesis for lightweight electromagnetic absorber

Although the performance of NiCo2O4-based absorbers with multiple components has made great progress, the property of pure NiCo2O4 is still far from the requirements of high-performance electromagnetic wave absorbers. It is recognized that morphology control is an effective strategy to improve electromagnetic absorbing capacity of absorbers. Herein, this work reported the fabrication of porous flower-like pure NiCo2O4 via simple hydrothermal reaction with the assistant of sodium tartarate in where tartaric acid served as a structure-directing agent. It was demonstrated that size distribution and electromagnetic absorbing capacity of the obtained NiCo2O4 could be modulated easily by controlling addition of sodium tartrate. It was verified that dipole polarization originated from lattice defect and oxygen vacancy as well as interfacial polarization ascribing to adjacent and interconnected flakes are responsible for the excellent electromagnetic absorbing performance. The obtained porous flower-like NiCo2O4 exhibited broad absorption bandwidth at thin thickness as well as proper dissipation ability. This work offers a new strategy to fabricate size-controllable porous flower-like NiCo2O4 electromagnetic absorber. It is believed the obtained NiCo2O4 will be a promising candidate as a lightweight electromagnetic absorbing material.

Hierarchical Architectured Dahlia Flower-Like NiCo2O4/NiCoSe2 as a Bifunctional Electrode for High-Energy Supercapacitor and Methanol Fuel Cell Application

We report unique hierarchical dahlia flower-like NiCo2O4 nanograss/NiCoSe2 nanosheets on Ni foam (NCO/NCS/NF) as bifunctional binder-free electrodes for high energy density hybrid supercapacitors and methanol electro-oxidation applications. NCO/NCS/NF is synthesized by a facile hydrothermal method followed by an electrodeposition process. As a supercapacitor electrode, NCO/NCS/NF exhibits a superior specific capacitance of 2045.5 F g-1 (227 mAh g-1 or 818 C g-1) at 1.8 A g-1. The assembly of a hybrid NCO/NCS/NF//AC device delivers impressive specific energy of 54.5 Wh kg-1 at 350 W kg-1 with durable cyclic stability of 82.5% after 10,000 charge-discharge cycles. NCO/NCS/NF as an electrocatalyst toward methanol oxidation yields a high current density of 130 mA cm-2 at 0.5 V and a low onset potential of 0.13 V, in comparison to other reported catalysts. Such high electrochemical performance of a binder-free NCO/NCS/NF electrode is attributed to the synergistic effect between the bimetallic oxides and selenides, core-shell nanostructure, hierarchically aligned architectures of nanograss/nanosheets, and conductive coatings of NCS to provide rapid charge transfer reactions. To the best of author's knowledge, this is the first report of a 3D hierarchical NCO/NCS/NF 1D/2D nanostructure toward a bifunctional binder-free electrode for energy storage and conversion technologies.

Unveiling the structural, charge density distribution and supercapacitor performance of NiCo2O4 nano flowers for asymmetric device fabrication

The flower-like nano sized nickel cobalt oxide was successfully synthesized by facial hydrothermal method. Supercapacitor [NiCo2O4)||Activated carbon] asymmetric supercapacitor device (ASC) has been fabricated. The prepared self-assembled flower-like nanostructured NiCo2O4 nanomaterials were subjected to various analytical tools such as Powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR). Furthermore, the bond length and electron cloud density between the atoms were analyzed by maximum entropy method (MEM). The electrochemical studies were probed using Cyclic Voltammetry (CV), chronopotentiometry charge-discharge (CD) and electrochemical impedance spectroscopy (EIS) using electrochemical workstation (CHI6008e) instrument. The activated carbon was used as an anode electrode material for device fabrication. The maximum specific capacitance of NiCo2O4 NFs was achieved to be 1030 Fg−1 at 1 Ag−1 with good cyclic stability. The maximum specific capacitance of ASC device is 41 Fg−1 at 1 Ag−1. More interestingly, the maximum specific energy (10 W h kg−1) and specific power (2000 W kg−1) values are achieved for asymmetric supercapacitor energy storage device.

Hierarchical flower-like NiCo2O4 applied in n-butanol detection at low temperature

In this work, hierarchical flower-like NiCo2O4 assembled by hexagonal sheets was prepared in one-step hydrothermal method, in which 2-mIM (2-Methylimidazole) acted as the structure-directing agent. The amount of 2-mIM had a great influence on the morphology and the composition of products, which further influenced the n-butanol gas-sensing performance. In addition, the systematic gas tests were carried out. It was concluded that compared with other corresponding samples, the hierarchical NiCo2O4 prepared with 18 mmol 2-mIM (NC-2) presented the highest gas sensitivity (240 %) and selectivity to 100 ppm of n-butanol at a low operation temperature 165 °C, with a response/recovery time of 68 s/107 s and an excellent long-term stability. Furthermore, the detailed analyses of the gas sensing mechanism were discussed in this paper. The best gas sensing performance of NC-2 based sensor was attributed to its unique hierarchical structure, which can provide more active sites for the process of oxygen adsorption. In addition, the content of chemical adsorbed oxygen species and the specific surface area of samples had an intimate relationship with the response for sensing materials. In summary, this research provided a simple way in designing n-butanol sensor based on hierarchical flower-like NiCo2O4 at a low operation temperature.