As-prepared Nickel Oxide Research Articles

Facile Growth, Physical Characterization, and Dielectric Response of As-Grown NiO Nanostructures

Nickel Oxide (NiO) nanostructures were prepared via the hydrothermal technique to examine the structure, optical, and dielectric properties. Various structural, and optical parameters: such as crystal structure, lattice parameter, average crystallite size, average micro-strain, peaks of stretching vibrations, and optical band gap, have been evaluated. Furthermore, the as-prepared NiO nanostructures were used as a dielectric material in a capacitor. Comparatively, the obtained high values of dielectric constant, and low values of dielectric loss show the potential applications of NiO nanostructures as a dielectric material. A possible mechanism has also been illustrated to explain the dielectric behaviour of the as-grown nanostructures.

Large coloration efficiency and fast response NiO electrochromic thin film electrode based on NiO nanocrystals

Nickel oxide (NiO) nanocrystals were fabricated by one-pot synthesis under the atmosphere of O2. Transmission Electron Microscope (TEM) test show that the average diameter was ca. 3 nm. X-Ray Diffraction (XRD) reveal the NiO nanocrystals were cubic structure. The as-prepared NiO nanocrystals were then surface-modified by pyridine to enhance their electrochromic (EC) performances. Measurement of EC properties of NiO nanocrystals was performed by testing NiO thin film electrode based on NiO nanocrystals in LiClO4/PC electrolyte with applied voltages of ±1.5 V, 50 s respectively. The results show that nanocrystals based NiO electrode have good EC performances. Optical modulation rate (ΔT) was 41.5% at the wavelength of 550 nm. Coloration switching time was 1.77 s and coloration efficiency (CE) was 114.7 cm2·C−1.

Dual-energy application of NiO: Electrochemical and photovoltaic properties

In the present work, we report the synthesis of Nickel oxide (NiO) nanoparticles employing hydrothermal technique. The surface morphology, crystal structure, porosity and vibrational response were characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), surface area and pore size analyzer, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. FESEM images confirm flower-like morphology of as-synthesized sample. XRD result reveal its polycrystalline nature and cubic structure of as-prepared NiO nanoparticles. FTIR results identified the surface functional groups attached with the molecules while Raman peaks show the characteristic vibrational mode and magnon excitation. Pore size and surface area analysis reveal the porosity in the synthesized sample and indicates its suitability use for electrochemical and photovoltaic devices. It was found that the NiO sample offered specific capacitance as high as 47.6 F g−1 (at scan rate of 10 mV s−1), when employed as working electrode in two-electrode assembly. Also, the synthesized sample provided efficiency of 0.92%, when employed to fabricate dye-sensitized solar cell. It is therefore a worthy candidate for further research.

Efficient microwave enhanced degradation of 4-nitrophenol in water over coupled nickel oxide and solid acid catalysts

An efficient and controllable abatement of 4-nitrophenol based on series of catalysts and auxiliary reagents, the as-prepared nickel oxide and solid acid tabloid, was reported as resulting by microwave degradation. In regard to the effects of microwave power, various kinds of nickel oxide and solid acid, at auxiliary reagent dosage, and in various concentrations were evaluated in relation to their removal efficiency. The results showed that the addition of solid acid can delicately tune the reaction pH and enhance the degradation of 4-nitrophenol over nickel oxide. The performance was apparently affected according to the kinds of solid acid and the as-prepared nickel oxide. The reducibility and amount of high valence of Ni3+ over the as-prepared NiOx can influence the resultant reaction. The lower reduction temperature and higher NH2/NNi ratio can weaken the bond strength of NiOx and readily releases partial oxygen to assist with the degradation of 4-NP within a microwave system. Both 300 and 500 ppm 4-nitrophenol can be completely degraded within 25 min under low power of 7 W over 0.12 g of as-prepared nickel oxide coupled with 0.24 g zirconium sulfate tabloid to adjust the reaction pH below 3 via the combined effect of nickel oxide and solid acid.

Single‐crystalline porous NiO nanobiscuits with prompt adsorption activity for Congo red

Single-crystalline two-dimensional (2D) nickel oxide (NiO) porous nanobiscuits with diameters of 100–210 nm, thicknesses of 10–20 nm and pore sizes of <20 nm are fabricated through a low-cost water bath combined with calcination treatment approach. The composition and morphology of the products are characterised by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, selected area electronic diffraction and N2 adsorption/desorption. The possible formation mechanism of single-crystalline porous NiO nanobiscuits is simply discussed. Served as adsorbent, the as-prepared single-crystalline porous NiO nanobiscuits exhibited excellent performance for the fast removal of Congo red from water, which is far beyond the adsorption rate of activated carbon. The results show that the adsorption isotherm fits well with Langmuir adsorption model. The maximum adsorption capacity is calculated to be 193.2 mg g−1, which is larger than that of other reported 2D NiO architectures.

Supersensitive and superselective formaldehyde gas sensor based on NiO nanowires

In this work, nickel oxide (NiO) nanowires were synthesized by a simple hydrothermal route using NiCl2·6H2O, Na2C2O4 and ethylene glycol (EG) as precursors at 220 °C for 12 h. The products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmittance electron microscopy (TEM), scanning electron microscopy (SEM). The crystal structure of prepared NiO nanowires is cubic phase polycrystalline. The average nanowires diameter is ∼120 nm. The gas sensing properties of the as-prepared NiO nanowires toward formaldehyde were investigated.

Electrochemical Properties of Nickel Oxide Nanoplates As Electrode for Lithium Ion Battery

Nanostructure transition metal oxides (MO-type M = Fe, Co, Ni, Cu, . ) with rock-salt structure are promising anode materials for lithium ion batteries. These types of materials can store two to three times the capacity of graphite anode (372 mAh g-1) which is the state-of-the-art technology. Here we focus on the growth of Nickel oxide (NiO) prepared by chemical vapor deposition (CVD) directly on current collectors and understanding of the origin of the excess capacity. The synthesis of the NiO nanoplates by CVD directly on the current collectors is ideal for studying the electrochemical properties because they are no interferences from additives. In addition, the direct growth of the materials onto current collectors provides faster mass and electron transport due to the improvement in conductivity across the interfaces and through the materials due to its nanosize. The microstructural characteristics of the as-prepared NiO nanoplates were examined by high resolution transmission electron microscopy which showed that they were arranged randomly on the current collector. Selected area electron diffraction showed that the NiO is polycrystalline with the face-centered cubic crystal structure. The X-ray photoelectron spectroscopy showed that the as-prepared materials are pure NiO. We studied the galvanostatic discharge-charge of the NiO electrode. During the first discharge process from 3.0 V to 0.1 V, a plateau at approximately 0.70 V followed by a gradual decrease to 0.1 V, is observed. This is due to the reduction of Ni2+ to Ni0 and the formation of Li containing organic and solid electrolyte interface (SEI). The first discharge corresponds to approximately 1100 mAh/g which is equivalent to 3 mol of Li per mol of NiO which is more than the expected capacity of according to the conversion reaction: NiIIO + Li0 +2e- ß à LiI 2O + Ni0 (718 mAh/g). The excess capacity of the NiO nanoplates and the cyclic voltammetry will be discussed.

Synthesis and Characterization of Nio Nanocrystals by using Sol-Gel Method with Various Precursors

Nickel oxide (NiO) nanocrystals were synthesized by simple sol-gel method at low temperature by using methanol as the solvent and NaOH 5M as the precipitation agent. Nickel nitrate hexahydrate, nickel acetate tetrahydrate and nickel sulfate hexahydrate were used as the precursors. The crystals were formed by drying at 100-110 ° C for ± 1 hour, after which they were heated at ± 450 ° C for 1 hour. The resulting products were black powders. The as-prepared NiO nanocrystals were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns of the NiO nanocrystals showed that they are mostly cubic. The sizes of the NiO particles produced with nickel nitrate hexahydrate, nickel acetate tetrahydrate and nickel sulfate hexahydrate were 72.16, 38.63 and 32.84 nm, respectively. SEM images showed that the nanopowders produced by the precursors are spherical, rod-shaped and hexagonal shape with hollow , respectively.

Solution-processed quantum dot light-emitting diodes based on NiO nanocrystals hole injection layer

Nickel oxide (NiO), as a kind of p-type transition metal oxide (TMO) has shown promising applications in photoelectric devices. In our work, the NiO nanocrystals (NCs) are fabricated by a simple solvothermal method using tert-butyl alcohol and nickel acetylacetonate as precursors at 200 °C for different reaction times. The diameters and valence band edge of the prepared NiO NCs are increased with the increase reaction time from 12 h, 24 h–36 h. The band gaps of the NiO NCs were decreased with the increase time. Selected area electron diffraction (SAED) shows that the NiO NCs is polycrystalline structure. X-ray diffraction (XRD) indicates that the NiO NCs is cubic crystal form. X-ray photoelectron spectroscopy (XPS) shows that the as-prepared NiO NCs have a core of NiO and some form of Ni2O3 and NiOOH states on its surface. Further, the obtained NiO NCs is applied on quantum dot light-emitting diode (QLED) as hole injection layer (HILs), showing excellent hole injection properties. Particularly, the NiO NCs for 24 h obtains the best results due to its high band gap and pure cubic crystal phase. Highly bright orange-red QLED with peak luminance up to ∼25580 cd m−2, and current efficiency (CE) of 5.38 cd A−1 are achieved successfully based on the high performance NiO HIL, further, the device obtained relative long operational lifetime of 11491 h, which has been improved by more than 6- fold as compared to 1839 h for the device based on PEDOT.

MICROWAVE ASSISTED SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF NICKEL OXIDE NANOPARTICLES

Nickel oxide (NiO) nano-particles were produced via a simple microwave method from the Ni(OH)2 precursor, which was obtained by slow drop-wise addition of 0.1M sodium hydroxide to 0.1M nickel nitrate. The mixture was vigorously stirred until the pH reached 7.2. The mixture was then irradiated with microwave to deposit Ni(OH)2 at a better precipitation rate. Drying the precipitate at 320°C resulted in formation of NiO nanoparticles. High Resolution Transmission Electron Microscope (HRTEM), Scanning Electron Microscope (SEM) and X-ray diffraction (XRD), employed for the structural characterization of the as-prepared NiO nanoparticles, revealed their good crystallinity and high-purity. Microwave irradiation increased homogeneity and decreased the mean particle size of the produced NiO particles.

A Versatile Combustion Synthesis and Properties of Nickel Oxide (NiO) Nanoparticles

We report here a simple solution combustion synthesis of nickel oxide (NiO) nanoparticles by using urea as a fuel and nickel nitrate as an oxidizer. The structural, morphological, optical, and magnetic properties of NiO nanoparticles were investigated by X-ray diffraction (XRD); highresolution scanning electron microscopy (HRSEM); Fourier transform infrared (FT-IR), nearinfrared (NIR), and UV-vis spectroscopic techniques; and vibrating sample magnetometer. The combustion-synthesized NiO nanoparticles have a cubic structure with an average crystalline size of ∼8 nm without any impurity. The agglomeration of fine particles with particle sizes in the range of 19.5 ∼22.4 nm is seen by HRSEM images. The FT-IR spectrum of NiO nanoparticles reveals that an absorption band at ∼493 cm −1 is due to the bending vibration of NiO phase. The NIR spectrum exhibits poor NIR reflectivity of the combustion product, NiO. The as-prepared combustion product was black in color in contrast to the usual light green color. The room-temperature magnetization of the as-prepared NiO nanoparticles reveals an antiferromagnetic behavior.

Morphology well-controlled synthesis of NiO by solvothermal reaction time and their morphology-dependent pseudocapacitive performances

Synthesis of nickel oxide (NiO) nanomaterials with well-controlled morphologies is crucial to obtain superior electrochemical properties. Herein, we present a facile solvothermal route for the fabrication of three different morphologies NiO containing particles, honeycomb and three-dimensional (3D) nanoflower by adjusting the solvothermal reaction time. The possible mechanism for the formation process of the hierarchical 3D nanoflower architecture is investigated and proposed. The morphology and crystal structure of the as-prepared NiO were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TG), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and the Brunauer–Emmett–Teller method (BET). The effects of morphologies on the electrochemical performances were systematically studied. It was found that NiO with flower-like structure exhibited the highest specific capacitance (364 F g−1 at 1 A g−1), excellent rate capability (64% capacitance retention from 1 A g−1 to 10 A g−1) and excellent cycling stability (no decrease in specific capacitance after 1200 test cycles).

Synthesis of nickel oxide nanospheres by a facile spray drying method and their application as anode materials for lithium ion batteries

Fabrication of advanced anode materials is indispensable for construction of high-performance lithium ion batteries. In this work, nickel oxide (NiO) nanospheres are fabricated by a facial one-step spray drying method. The as-prepared NiO nanospheres show diameters ranging from 100 to 600nm and are composed of nanoparticles of 30–50nm. As an anode for lithium ion batteries, the electrochemical properties of the NiO nanospheres are investigated by cyclic voltammetry (CV) and galvanostatic charge/discharge tests. The specific reversible capacity of NiO nanospheres is 656mAhg−1 at 0.1C, and 476mAhg−1 at 1C. The improvement of electrochemical properties is attributed to nanosphere structure with large surface area and short ion/electron transfer path.

Properties of NiOx and its influence upon all-thin-film ITO/NiOx/LiTaO3/WO3/ITO electrochromic devices prepared by magnetron sputtering

Nickel oxides (NiOx) thin films were magnetron sputtered in Ar/O2 mixing gases with the relative O2 concentration varied from 4.5% to 20%. Subsequently, each NiOx film was used to fabricate an all-thin-film glass/ITO/NiOx/LiTaO3/WO3/ITO electrochromic device (ECD). All the ECDs were fabricated monolithically in a same vacuum chamber layer by layer using dc reactive sputtering for NiOx, WO3 and ITO, and radio frequency (rf) sputtering for LiTaO3. Influence of oxygen concentration upon properties of NiOx as well as their corresponding ECDs was focused on and studied through grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible spectrometry. The results show that the as-prepared nickel oxide films can be represented as NiOx with 1.10 ≤ x ≤ 1.21 when O2 concentration in sputtering gas changes. With increasing x, the preferred crystalline orientation (100) of NiOx thin films vanished, and (111) and (220) plane appeared. Owing to the poor crystalline structure in favor of ion transportation in the NiOx layer and less proportion of Ni3+, the device with NiOx film deposited at 6% O2 concentration displayed high transmittance at bleached state and subsequently an excellent transmittance modulation of more than 67%. Coloring and bleaching response time of this device was 85 s and 42 s, respectively. The results confirm that the magnetron-sputtered technical parameters proposed in this work is promising for all-thin-film ECDs with excellent electrochromic performance.

Single-crystal-like NiO colloidal nanocrystal-aggregated microspheres with mesoporous structure: Synthesis and enhanced electrochemistry, photocatalysis and water treatment properties

Abstract A new microwave-assisted hydrothermal synthetic route based on the self-assembly and subsequently controlled thermal decomposition process is proposed to fabricate nickel oxide colloidal nanocrystal aggregated microspheres (CNAMs) with mesoporous structure. XRD, EDS, SEM, TEM. FTIR, and N2 adsorption and desorption isotherm techniques are employed for morphology and structure characterizations. The as-prepared nickel oxide CNAMs, which has a high surface area (234 m2/g) with narrow pore distribution at around 3.25 nm, are composed of numerous hexagonal mesoporous nanocrystals of approximately 50–60 nm in size, and present a single-crystal-like characteristic. The experimental results also demonstrated that the CNAMs showed outstanding performance in electrochemistry, photocatalysis and waste water treatment due to their special hierarchical and mesoporous structure, presenting the promising candidate for catalysis and catalysis support materials.

Preparation and electrochemical properties of multiwalled carbon nanotubes–nickel oxide porous composite for supercapacitors

Porous nickel oxide/multiwalled carbon nanotubes (NiO/MWNTs) composite material was synthesized using sodium dodecyl phenyl sulfate as a soft template and urea as hydrolysis-controlling agent. Scanning electron microscopy (SEM) results show that the as-prepared nickel oxide nanoflakes aggregate to form a submicron ball shape with a porous structure, and the MWNTs with entangled and cross-linked morphology are well dispersed in the porous nickel oxide. The composite shows an excellent cycle performance at a high current of 2 A g −1 and keeps a capacitance retention of about 89% over 200 charge/discharge cycles. A specific capacitance approximate to 206 F g −1 has been achieved with NiO/MWNTs (10 wt.%) in 2 M KOH electrolyte. The electrical conductivity and the active sites for redox reaction of nickel oxide are significantly improved due to the connection of nickel nanoflakes by the long entangled MWNTs.