NiO Microspheres Research Articles

Dual Role of Multiroom-Structured Sn-Doped NiO Microspheres for Ultrasensitive and Highly Selective Detection of Xylene.

Sn-doped NiO multiroom spheres with unique microreactor morphology were prepared by facile ultrasonic spray pyrolysis of a solution containing tin oxalate, nickel nitrate, and dextrin and subsequent heat treatment. The multiroom structure was formed by phase segregation between the molten metal source and liquidlike dextrin and sequent decomposition of dextrin during spray pyrolysis, which played the dual roles of enhancing gas response and selectivity. The response (resistance ratio) of the Sn-doped NiO multiroom spheres to 1 ppm p-xylene was as high as 65.4 at 300 °C, which was 50.3 and 9.0 times higher than those of pure NiO multiroom spheres and Sn-doped NiO dense spheres, respectively. In addition, the Sn-doped NiO multiroom sensors showed a high selectivity to xylene. The unprecedented high response that enables the sensing of sub-ppm xylene was explained by the high gas accessibility of the multiroom structures and the Sn-doping-induced change in oxygen adsorption as well as the charge carrier concentration, whereas the high xylene selectivity was attributed to the decomposition/re-forming of xylene into smaller or more active species within the unique multiroom structure of Sn-doped NiO microreactors characterized by high catalytic activities. The multiroom oxide spheres can be used as a new and generalized platform to design high-performance gas sensors.

Functionalized Graphene Quantum Dot Modification of Yolk-Shell NiO Microspheres for Superior Lithium Storage.

Yolk-shell NiO microspheres are modified by two types of functionalized graphene quantum dots (denoted as NiO/GQDs) via a facile solvothermal treatment. The modification of GQDs on the surface of NiO greatly boosts the stability of the NiO/GQD electrode during long-term cycling. Specifically, the NiO with carboxyl-functionalized GQDs (NiO/GQDsCOOH) exhibits better performances than NiO with amino-functionalized GQDs (NiO/GQDsNH2 ). It delivers a capacity of ≈1081 mAh g-1 (NiO contribution: ≈1182 mAh g-1 ) after 250 cycles at 0.1 A g-1 . In comparison, NiO/GQDsNH2 electrode holds ≈834 mAh g-1 of capacity, while the bald NiO exhibits an obvious decline in capacity with ≈396 mAh g-1 retained after cycling. Except for the yolk-shell and mesoporous merits, the superior performances of the NiO/GQD electrode are mainly ascribed to the assistance of GQDs. The GQD modification can support as a buffer alleviating the volume change, improve the electronic conductivity, and act as a reservoir for electrolytes to facilitate the transportation of Li+ . Moreover, the enrichment of carboxyl/amino groups on GQDs can further donate more active sites for the diffusion of Li+ and facilitate the electrochemical redox kinetics of the electrode, thus together leading to the superior lithium storage performance.

Preparation and Electrochemical Application of Porous Yttrium-Doped NiO Microspheres

Using NiCl[Formula: see text]O and Y(NO)3 solution as raw material and urea as the precipitating agent, Yttrium-doped NiO hollow spheres (Y-NiOHS) were prepared through homogeneous precipitation method with melamine–formaldehyde polymer microspheres (MF) as templates. The electrochemical performances of Y-NiOHS with difference Y-doped mole ratios (Y:[Formula: see text]%, 0.5%, 1%Y-NiOHS) were characterized by cyclic voltammetry (CV), constant current charge–discharge test (GCD) and AC impedance test (EIS). The results of CV show that 0.5%Y-NiOHS in 5[Formula: see text]mV/s scan rate can achieve the maximum capacity of 320.92[Formula: see text]F/g. The results of GCD show that the capacity of 0.5%Y-NiOHS is 226.2[Formula: see text]F/g at 0.5[Formula: see text]A/g discharge current density and the 1000 charge–discharge cycles after the capacitance retention rate is 85%. The electrochemical performance of 0.5%Y-NiOHS are better than NiOHS and NiO powder.

Core–shell structured hierarchically porous NiO microspheres with enhanced electrocatalytic activity for oxygen evolution reaction

We present a one-pot synthetic strategy to synthesize hierarchically porous NiO microspheres with enhanced activity for OER.

Bio-template synthesized NiO/C hollow microspheres with enhanced Li-ion battery electrochemical performance

NiO microspheres with well-defined hollow structure were successfully obtained using spherical yeast as a natural bio-template. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The morphologically uniform NiO hollow microspheres prepared with yeast template after calcination had an averaged diameter of 1.5–2 μm and the shell thickness of ∼500 nm. The concentration of Ni(NO3)2, calcination temperature and aging time play important roles on the crystal phase and morphologies of the NiO hollow microspheres. Meanwhile, the NiO/C hollow microspheres were successfully fabricated via a simple hydrothermal method using glucose as carbon source. A possible formation mechanism of forming NiO/C hollow microspheres was proposed and the electrochemical performance of the NiO/C hollow microspheres as anode material for Li-ion batteries was investigated. Compared with the samples prepared without template or without carbon coating, the as-prepared NiO/C hollow microspheres show higher discharge capacity and better cycle performance as an anode material in Li-ion batteries.

Self-assembly of dandelion-like NiCo2O4 hierarchical microspheres for non-enzymatic glucose sensor

ABSTRACTThe dandelion-like NiCo2O4 hierarchical microspheres were successfully prepared and used as the nonenzymatic glucose sensing materials. The characterization showed that the as prepared hierarchical dandelion-like NiCo2O4 microspheres are composed of closely connected outstretched nanowires with the average diameter about 50 nm and length about 1–1.5 μm with the substructured nanowires made up of nanoparticles with the diameters less than 10 nm. The dandelion-like NiCo2O4 hierarchical microspheres exhibited superior electrochemical activity towards oxidation of glucose, which is much higher than that of pure NiO microspheres. The amperometric responses are linear with glucose in the concentration range of 10–10480 μM a sensitivity of 430.86 μA cm−2 mM−1. Moreover, the interference from the commonly interfering species such as L-valine, urea, L-proline, NaCl and L-lysine can be effectively avoided. The good electrochemical performance of materials may be due to its complex chemical compositions, hierarchical structure and the synergetic effect of both individual components. The high sensitivity, wide glucose detection range and good selectivity indicated that the newly developed sensor based on the dandelion-like NiCo2O4 hierarchical microspheres is a promising sensor for practical application.

NiO/CNTs derived from metal-organic frameworks as superior anode material for lithium-ion batteries

In this work, porous NiO microspheres interconnected by carbon nanotubes (NiO/CNTs) were successfully fabricated by the pyrolysis of nickel metal-organic framework precursors with CNTs and evaluated as anode materials for lithium-ion batteries (LIBs). The structures, morphologies, and electrochemical performances of the samples were characterized by X-ray diffraction, N2 adsorption-desorption, field emission scanning electron microscopy, cyclic voltammetry, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy, respectively. The results show that the introduction of CNTs can improve the lithium-ion storage performance of NiO/CNT composites. Especially, NiO/CNTs-10 exhibits the highest reversible capacity of 812 mAh g−1 at 100 mA g−1 after 100 cycles. Even cycled at 2 A g−1, it still maintains a stable capacity of 502 mAh g−1 after 300 cycles. The excellent electrochemical performance of NiO/CNT composites should be attributed to the formation of 3D conductive network structure with porous NiO microspheres linked by CNTs, which benefits the electron transfer ability and the buffering of the volume expansion during the cycling process.

NiO hierarchical hollow microspheres doped Fe to enhance triethylamine sensing properties

The NiO nanosheets assembled hollow spheres have been synthesized by a facile precipitation method using SiO2 spheres as hard template, and the Fe was doped into NiO to improve the sensing properties of triethylamine (TEA). The structure, morphology and gas sensing properties of undoped and doped NiO were characterized by various analysis methods. The results show that the NiO microspheres have large specific surface, and excellent sensing response to 10ppm triethylamine, so, it is a promising sensing material for detection of TEA.

High saturation magnetization superparamagnetic Fe/Ni core/shell microparticles for chromium removal

In this paper, the Fe/Ni microparticles are synthesized by two reactions which directly utilize H2 to reduce NiO and Fe3O4 microspheres.

A new general approach to synthesizing filled and yolk-shell structured metal oxide microspheres by applying a carbonaceous template.

New mechanisms were found for the formation of metal oxide microspheres with yolk-shell and filled structures by applying carbonaceous template microspheres with high porosity. Repeated impregnation first adopted to achieve a high loading rate of metal precursor in the carbonaceous template provided the breakthrough. The carbonaceous template with an appropriate loading rate of the metal precursor produced metal oxide microspheres with filled and yolk-shell structure depending on the ramping rate and oxygen concentration during the post-treatment process. Combustion of the carbonaceous template-which occurs during the moderate post-treatment process in air with a high oxygen concentration-must occur to form yolk-shell structured microspheres. On the other hand, the decomposition of carbon by post-treatment at a slow ramping rate in an atmosphere with a low oxygen concentration without burning produced filled-structured metal oxide microspheres. The carbonaceous template with a high loading rate of the metal precursor produced metal oxide microspheres with filled structures even at a fast ramping rate and high oxygen concentration during the post-treatment process. The new strategy was applied to synthesize various metal oxide microspheres including SnO2, Fe2O3, NiO, and Mn2O3 microspheres.

Facile synthesis of self-assembled biporous NiO and its electrochemical properties

In this article, we report the synthesis of self-assembled bi-porous nickel oxide on a large scale without using any templates or matrix. Porous NiO microspheres composed of particles were obtained by thermal decomposition of nickel oxalate, which was prepared using nickel salt and oxalic acid as precursors. The as-obtained nickel oxalate and nickel oxide were characterized using X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), thermogravimetric analysis (TGA), and nitrogen adsorption-desorption analysis. The influence of various experimental conditions on the formation nickel oxalate and NiO were studied. The nitrogen adsorption-desorption analysis showed that the synthesized NiO possesses a biporous (both mesoporous and macroporous) surface structur. The NiO microspheres showed a discharge capacity of 2929 mAh g−1. A plausible mechanism for the NiO self-assembly was proposed.

NiO hollow microspheres interconnected by carbon nanotubes as an anode for lithium ion batteries

In this work, NiO hollow microspheres interconnected by multi-walled carbon nanotubes (MWCNTs) were prepared, characterized, and evaluated in terms of lithium ion storage properties. Characterization results showed that the NiO hollow microspheres were formed by self assembly of NiO nanoparticles promoted by MWCNTs, which connected the NiO microspheres to form a long-range network. Electrochemical measurement results showed a charge capacity as high as 597.2mAhg−1 when cycling at the rate 2C and maintained 85.3% capacity of 0.1C. After cycling for 100 times at 1C, it maintained a capacity of 692.3mAhg−1 with retention 89.3% of the initial capacity. The observed excellent electrochemical performance is attributed to the presence of MWCNTs interconnecting the NiO microspheres of the composite material, of which electronic conductivity was improved, and the mesoporous hollow structure effectively alleviated the volume changes to maintain the structural stability during cycling.

Low Dimensional Materials for Lithium-Ion Batteries

Along with social progress, the popularity of portable electronic products, the development of new energy such as solar energy and wind energy technology, and the utilization of hybrid electric and electric vehicles all rely heavily on high-performance energy storage devices. Lithium ion batteries are promising storage devices to satisfy these needs due to their advantages of high open circuit voltage, large energy density, long cycle life, no memory effect, less pollution and small self-discharge rate. In fact, the capabilities of electrodes materials show significant effects on the performance of lithium-ion batteries. Nanostructured materials possess reduced sizes, enlarged surfaces, increased boundaries and gaps, which could lead to improved diffusion kinetics, more ion insert channels and release strain for volume changes compared to normal bulk materials. As electrode materials for lithium batteries, nanostructured materials could offer high reversible capacity, fine rate performance and good cycling stability. In this talk, we introduce the design and synthesis of several nanostructured materials, including MoS2-based nanocomposite, NiO porous nanostructure,Hierarchical TiO2 microstructure, and Zn2GeO4/g-C3N4 hybrids, discuss their application for lithium-ion batteries. Reference Lihua Chu, Meicheng Li, ZiPei Wan, Lei Ding, Dandan Song, Shangyi Dou, Jiewei Chen and Yu Wang. Morphology control and fabrication of multi-shelled NiO spheres by tuning pH value via hydrothermal process. CrystEngComm , 2014, 16, 11096 Xiaodan Li, Wei Li, Meicheng Li,* Peng Cui, Dehong Chen, Thomas Gengenbach, Huiyuan Liu, and Guangsheng Song. Glucose-assisted synthesis of the hierarchical TiO2 nanowires @ MoS2 nanosheets nanocomposite and its synergistic lithium storage performance. Journal of Materials Chemistry A , 2015, 3:2762-2769 Lihua Chu, Meicheng Li*, Xiaodan Li, Yu Wang, Zipei Wan, Shangyi Dou, Dandan Song, Yingfeng Li and Bing Jiang. High performance NiO microsphere anode assembled from porous nanosheets for lithium-ion batteries. RSC Advances , 2015, 5, 49765 - 49770, Peng Cui, Bixia Xie, Xiaodan Li, Meicheng Li,* Yaoyao Li, Yu Wang, Zhuohai Liu, Xin Liu, Jing Huang, Dandan Song, Joseph Michel Mbengue. Anatase/TiO2-B hybrid microspheres constructed by ultrathin nanosheets: facile synthesis and application for fast lithium ion storage. CrystEngComm , 2015, 17:7930-7937 Xiaodan Li, Yi Feng, Meicheng Li* , Wei Li, Hao Wei, and Dandan Song. Smart Hybrids of Zn2GeO4 Nanoparticles and Ultrathin g-C3N4 Layers: Synergistic Lithium Storage and Excellent Electrochemical Performance. Advanced Functional Materials. 2015, 25(44): 6858-6866

Monodispersed plum candy-like MnO2 nanosheets-decorated NiO nanostructures for supercapacitors

A simple, template-free strategy without organic dispersant or capping agent is developed to synthesize a novel monodispersed NiO@MnO2 nanostructure as powdery electrode for supercapacitors. The first step in the synthesis involves the NaOH mediated evolution of Ni(OH)2 nanosheets, further leading to the formation of NiO structure with different features. After calcination in air, via self-decomposition of KMnO4 solution in a lower concentration, MnO2 nanoflakes are elaborately grafted along the petal of NiO microspheres to form core–shell nanostructures, enhancing specific surface area and homogenizing pore-size distribution of NiO@MnO2. Owing to the hierarchical core–shell heterostructure configuration with rich mesoporous and synergetic contribution from the NiO core and MnO2 shell, NiO@MnO2 exhibits relatively high specific capacitance and good rate capability, which are better than those of the individual NiO structure. The enhanced performance of the NiO@MnO2 core–shell structure demonstrates that integrated spherical structure constructed by two high capacitance materials is a rational design, which holds definite potential in supercapacitors and other kinds of energy storage systems.

Lotus pollen derived 3-dimensional hierarchically porous NiO microspheres for NO2 gas sensing

Hierarchically porous NiO microspheres with interconnected nano-pores were prepared with chemical bath deposition by using lotus pollens as bio-templates. The NiO microspheres thus derived have a specific surface area of 95.58m2/g and the average pore size is 20.98nm, such a nanostructure is ideal for gas sensing. To enhance the performances, the NiO microspheres were further decorated with Pd/PdO, and the sensor based on the Pd-decorated NiO microspheres demonstrated a high sensitivity (S=203), fast response/recovery (73s/169s) and excellent selectivity to 1.8ppm NO2 gas at 250°C. Compared with the other NO2 gas sensors based on NiO reported in previous works, the sensitivity of the NO2 sensor of this work is the highest and the response/recovery is among the fastest.

Facile fabrication of hierarchically porous NiO microspheres as anode materials for lithium ion batteries

In this work, we report a novel and facile route for the large-scale fabrication of hierarchically porous NiO microspheres, which involves the thermal decomposition of β-Ni(OH)2 precursor at 450 °C in air for 2 h. The superstructures exhibit high specific surface area, large porous volume, and broad pore size distribution. The electrochemical properties of the hierarchically porous NiO microspheres were examined by cyclic voltammetry and galvanostatic charge/discharge studies. The results demonstrate that the hierarchically porous NiO microspheres are promising anode materials with enhanced lithium storage capacity and excellent cycling stability. The hierarchically porous NiO microspheres can retain a reversible capacity of 612 mA h g−1 after 50 cycles at a current density of 100 mA g−1. The improved electrochemical performance is attributed to their hierarchical structure and large amounts of mesopores within the nanosheets, which can effectively improve structural stability, reduce the diffusion length for lithium ions and electrons, and buffer volume expansion during the charge/discharge processes.

Optimizing the Charge Transfer Process by Synthesizing NiO Microspheres on Ni Foam through Microwave-assisted Method

The porous nickel oxide microsphere on Ni foam was adopted to optimize the charge transfer process to improve electrochemical performance by a microwave-assisted method. Microstructure and morphologies of the re- sulting materials were investigated by X-ray diffraction, scanning electron microscope, transmission electron micro- scope. Results showed that the as-prepared NiO microspheres with nickel sulfate had average diameter of ~2 µm. The ultrathin secondary nanoflakes composed of nanowire building blocks were interconnected with each other forming a highly open net-structure. Because of enhanced electron transfer capability, charge transfer resistances of the porous microsphere were reduced and the electrochemical performances were improved, the charge-discharge measurements tested at a discharge current of 0.5 A/g showed higher rate specific capacitance (455 F/g). The impedance characteriza- tion illustrated lower electronic and ionic resistance of porous NiO due to its superior surface properties for enhanced electrode electrolyte contact during the faradaic redox reactions.

Template-free synthesis of 3D hierarchical nanostructured NiCo2O4mesoporous ultrathin nanosheet hollow microspheres for excellent methanol electrooxidation and supercapacitors

Novel 3D hierarchical NiCo2O4mesoporous ultrathin nanosheets hollow microspheres upon a facile template-free solvothermal method followed air-annealing shows excellent methanol electrooxidation and supercapacitors performance.

Multishelled NiO Hollow Spheres Decorated by Graphene Nanosheets as Anodes for Lithium-Ion Batteries with Improved Reversible Capacity and Cycling Stability

Graphene-based nanocomposites attract many attentions because of holding promise for many applications. In this work, multishelled NiO hollow spheres decorated by graphene nanosheets nanocomposite are successfully fabricated. The multishelled NiO microspheres are uniformly distributed on the surface of graphene, which is helpful for preventing aggregation of as-reduced graphene sheets. Furthermore, the NiO/graphene nanocomposite shows much higher electrochemical performance with a reversible capacity of 261.5 mAh g−1at a current density of 200 mA g−1after 100 cycles tripled compared with that of pristine multishelled NiO hollow spheres, implying the potential application in modern science and technology.

Porous and hollow NiO microspheres for high capacity and long-life anode materials of Li-ion batteries

Hollow NiO microspheres with porous shell are synthesized through the ion exchange of a facile zinc citrate template with the subsequent chemical etching. As an anode material for LIBs, the porous hollow NiO electrode shows much higher reversible capacity and better cycling stability in comparison with the ZnO–NiO composite. After 400cycles under a high current rate of 1C, the discharge capacity of the NiO electrode is steadily maintained around 700mAg−1. This excellent high power performance is attributed to the unique hollow and porous nanostructure, which not only increases the speed of mass transport but also accommodates the drastic volume change during the cycling process.