Synthesis, Characterization, and Effects of Morphology on the Magnetic Application Base Properties of Pure Nickel Oxide (NiO) and Cobalt-Doped Nickel Oxide/Nickel Hydroxide (CoxNi1-xO/Ni(OH)2) Nanocomposites

Nano particle (NP) morphology is one of the material properties at the origin of potential application base properties exploited in several engineering and technology domains, such as fuel cell, electrodes, catalysis, sensing, electric, thermal, magnetic, and photovoltaic applications. The general properties and particle morphology of nickel oxide/Nickel hydroxide NPs can be modified by the introduction of impurity atoms or ions. Nano sized nickel oxide/nickel hydroxide nanocomposites were obtained from the thermal decomposition of single molecular precursors synthesized by a modified oxalate route using Carambola fruit juice as a precipitating agent. The compositional and morphological variations were studied by introducing cobalt as an impurity ion at different w/w% fractions (0%, 0.1%, 0.3%, 0.5%, 1%, 3%, 5.0%, 40.0% and 50.0%) into the microstructure of the nickel oxide/hydroxide. The precursors were characterized by FT-IR, while TGA/DTG analysis was carried out to decompose the precursors. The precursors decomposed at 400°C and were characterized by PXRD and SEM/TEM. The results revealed that Pure Nickel Oxide (NiO) and, Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have been synthesized and the synthesized samples have exhibited three distinct morphologies (porous face-centered cubic nano rods, rough and discontinuous CoxNi1-xO/Ni(OH)2) composite and, smooth and continuous mix spherical/cuboidal mixed morphological phase of (NiO/CoO). The morphology of the NPs varied with the introduction of the dopant atoms and with increase in the concentration of dopant atoms in the composite. Magnetic studies using vibrating sample magnetometry revealed superparamagnetic properties which correlated strongly with particle size, shape and morphology. Observed values of retention (4.50 × 10-3 emu/g) and coercivity (65.321 Oe) were found for 0.5 w/w% corresponding to impregnated porous nanorods of Co-doped NiO, and retention (9.03 × 10-3 emu/g) and coercivity (64.341 Oe), for X = 50.0%, corresponding to an aggregate network of a Nano spherical/cubic CoO/NiO mixed phase. Magnetic properties within this range are known to improve the magnetic memory and hardness of the magnetic materials. Therefore, the synthesized Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have potential applications in Magnetic memories and hardness of magnetic materials.

Synthesis, Characterization, and Effects of Morphology on the Magnetic Application Base Properties of Pure Nickel Oxide (NiO) and Cobalt-Doped Nickel Oxide/Nickel Hydroxide (CoxNi1-xO/Ni(OH)2) Nanocomposites

Nano particle (NP) morphology is one of the material properties at the origin of potential application base properties exploited in several engineering and technology domains, such as fuel cell, electrodes, catalysis, sensing, electric, thermal, magnetic, and photovoltaic applications. The general properties and particle morphology of nickel oxide/Nickel hydroxide NPs can be modified by the introduction of impurity atoms or ions. Nano sized nickel oxide/nickel hydroxide nanocomposites were obtained from the thermal decomposition of single molecular precursors synthesized by a modified oxalate route using Carambola fruit juice as a precipitating agent. The compositional and morphological variations were studied by introducing cobalt as an impurity ion at different w/w% fractions (0%, 0.1%, 0.3%, 0.5%, 1%, 3%, 5.0%, 40.0% and 50.0%) into the microstructure of the nickel oxide/hydroxide. The precursors were characterized by FT-IR, while TGA/DTG analysis was carried out to decompose the precursors. The precursors decomposed at 400°C and were characterized by PXRD and SEM/TEM. The results revealed that Pure Nickel Oxide (NiO) and, Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have been synthesized and the synthesized samples have exhibited three distinct morphologies (porous face-centered cubic nano rods, rough and discontinuous CoxNi1-xO/Ni(OH)2) composite and, smooth and continuous mix spherical/cuboidal mixed morphological phase of (NiO/CoO). The morphology of the NPs varied with the introduction of the dopant atoms and with increase in the concentration of dopant atoms in the composite. Magnetic studies using vibrating sample magnetometry revealed superparamagnetic properties which correlated strongly with particle size, shape and morphology. Observed values of retention (4.50 × 10-3 emu/g) and coercivity (65.321 Oe) were found for 0.5 w/w% corresponding to impregnated porous nanorods of Co-doped NiO, and retention (9.03 × 10-3 emu/g) and coercivity (64.341 Oe), for X = 50.0%, corresponding to an aggregate network of a Nano spherical/cubic CoO/NiO mixed phase. Magnetic properties within this range are known to improve the magnetic memory and hardness of the magnetic materials. Therefore, the synthesized Cobalt-doped Nickel Oxide/nickel hydroxide (CoxNi1-xO/Ni(OH)2) Nano composites have potential applications in Magnetic memories and hardness of magnetic materials.

Environmentally Friendly Room Temperature Synthesis of 1-Tetralone over Layered Double Hydroxide-Hosted Sulphonato-Salen-Nickel(II) Complex

1-Tetralone, a useful synthetic intermediate in the manufacture of pharmaceuticals, agrochemicals and dyes, can be prepared by liquid phase catalytic oxidation of tetralin. Selective oxidation of tetralin to 1-tetralone is still a big challenge with low-temperature processes using environmentally friendly routes even after decades of research. Herein, we demonstrate room-temperature oxidation of tetralin to 1-tetralone over layered double hydroxide-hosted sulphonato-salen-nickel(II) complex, LDH-[Ni-salen]. The layered double hydroxide-hosted sulphonato-salen-nickel(II) compound was characterized by powder X-ray diffraction, Fourier transform infrared spectrometer (FTIR), UV-Visible diffuse reflectance spectra, scanning electron microscopy (SEM) and elemental analysis. The theoretical calculations of free sulphonato-salen-nickel(II) complex using Density Functional Theory/CAM-B3LYP at the 6-311++ G(d,p) level of theory were also used to determine the orientation of the Ni-salen compound within the layered structure. The immobilized compound, LDH-[Ni-salen] was found to be an effective reusable catalyst for the oxidation of tetralin to 1-tetralone using a combination of trimethylacetaldehyde and molecular oxygen (14.5 psi) and at 25°C. At 45.5% conversion, tetralin was converted to 1-tetralone with 77.2% selectivity at room temperature and atmospheric pressure after 24 h. The catalyst recycles test and hot filtration experiment showed that oxidation proceeded through Ni(II) sites in LDH-[Ni-salen]. The catalysts were reused several times without losing their catalytic activity and selectivity. The present results may provide a convenient strategy for the preparation of 1-tetralone using layered double hydroxide-based heterogeneous catalyst at ambient temperature for industrial application in near future.

Determination of Proton Diffusion Coefficient in Spherical Nickel Hydroxide Using Potential Step Measurement on Single Beads

The Potential step measurements are carried out on single beads of nickel hydroxide and the results are interpreted with a dual structure model featuring fast and slow diffusing components. The intrinsic diffusion coefficients for the two components are found to be in the order of magnitude 10-7 and 10-13~10-14 cm2s-1, respectively, with an apparent value for the slow component in the order of 10-10cm2s-1.

Influence of TiO_2 on the electrochemical performance of pasted typeβ-nickel hydroxide electrode in alkaline electrolyte

Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide（β-Ni（OH）2 ） was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni（OH）2 electrode performance are examined. The structure and property of the TiO2 added β-Ni（OH）2 were characterized by XRD, TG-DTA and SEM analysis. A pasted–type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni（OH）2 and TiO2 added β-Ni（OH）2 electrodes in 6 M KOH electrolyte. Anodic（Epa） and cathodic（Epc）peak potentials are found to decrease after the addition of TiO 2 into β-Ni（OH）2 electrode material. Further,addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni（OH）2 lectrode,TiO2 added β-Ni（OH）2 electrode is found to exhibit higher proton diffusion coefficient（D） and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni（OH）2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.

Synthesis of high-performance nickel hydroxide nanosheets/gadolinium doped-α-MnO_(2) composite nanorods as cathode and Fe_(3)O_(4)/GO nanospheres as anode for an all-solid-state asymmetric supercapacitor

The wide use of manganese dioxide(MnO_(2))as an electrode in all-solid-state asymmetric supercapacitors(ASCs)remains challenging because of its low electrical conductivity.This complication can be circumvented by introducing trivalent gadolinium(Gd)ions into the MnO_(2).Herein,we describe the successful hydrothermal synthesis of crystalline Gd-doped MnO_(2) nanorods with Ni(OH)_(2) nanosheets as cathode,which we combined with Fe_(3)O_(4)/GO nanospheres as anode for all-solid-state ASCs.Electrochemical tests dem on strate that Gd dopi ng sign ifica ntly affected the electrochemical activities of the MnO_(2),which was further enhanced by introducing Ni(OH)_(2).The GdMnO_(2)/Ni(OH)_(2) electrode offers sufficient surface electrochemical activity and exhibits excellent specific capacity of 121.8 mA h g^(-1),at 1A g^(-1),appealing rate performance,and ultralong lifetime stability(99.3%retention after 10,000 discharge tests).Furthermore,the GdMnO_(2)/Ni(OH)_(2)//PVA/KOH//Fe_(3)O_(4)/GO solid-state ASC device offers an impressive specific energy density(60.25 W h kg^(-1))at a high power density(2332 W kg^(-1)).This investigation thus shows its large potential in developing novel approaches to energy storage devices.

Experimental study by online measurement of the precipitation of nickel hydroxide: Effects of operating conditions

The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter of D = 240 mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution(PSD) were investigated. d43 and PSD were measured online using a Malvern Insitec Liquid Process Sizer every 20 s. It was found that d43 varied between 13 μm and 26 μm under different operating conditions,and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.

Effect of the amount of zinc-doped on the electrochemical performance of nickel hydroxide

The nickel hydroxide prepared by micro-emulsion method was doped by coprecipitated Zn. The effect of the amount of zinc-doped on the properties of Ni(OH)2 such as the reversibility of the electrode reaction, the charge efficiency and active material utilization ratio of nickel electrode, and discharge specific capacity was studied by cyclic voltammetry and constant current charge-discharge tests. The results indicate that the specific discharge capacity of nickel hydroxide obtained by micro-emulsion method is much less than its theoretical value because the transfer of electrons and the diffusion of protons H+ are hindered owing to its crystal grain size in a nanometer range and thus possessing higher crystal interface resistance. The crystal cells are swelled and the crystal defects increased in prepared material due to part of Ni2+ substituted by Zn2+ when zinc and nickel hydroxide are coprecipitated. Hence, the electrons and protons H+ in the electrode reaction are transferred easily, the electrochemical behavior of nickel electrode is improved and discharge specific capacity is promoted. However, the performance of Ni(OH)2 is gradually enhanced with the addition of zinc-doped at first, while slowly decreased after the content of zinc is added to a certain value. The best electrode reaction reversibility, the highest electrode charge efficiency, the highest active material utilization ratio and the largest specific capacity on discharge are available when the mass fraction of Zn doped in nickel hydroxide by coprecipitation reaches 2.5 %.

The Influence of Transmutation Conditions on the Adulteration Performance of Nano-scale Nickel Hydroxide

Spherical Nano-scale nickel hydroxide was prepared through precipitation transmutation method by controlling the transmutation conditions in this paper. The measurement results of XRD and TEM indicate that the crystallization of the nano-scale nickel hydroxide isβ-style and its shape is spherical with a diameter of 40～70 nanometer. The adulteration experiment shows that the adulteration ratio of nano- scale Ni(OH) 2 in common spherical micrometer-scale Ni(OH) 2 exists a optimal value (1∶9). And at this point, the utilization ratio of Ni(OH) 2 in electrodes can be raised by 10%, and the nano-scale nickel hydroxide with sphericity shape shows a better adulteration performance than that with needle shape.

Voltammetric Response and Electrocatalysis of Glasy Carbon Electrode Modified with Monolayer Nickel Hydroxide

The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scanning in 0.20 mol/L KOH. Similarly, GC/Co(OH) 2 electrode was prepared too. The experiments showed that the voltammetric behavior of GC/Ni(OH) 2 electrode in 0.20 mol/L KOH is more stable than that of GC/ Co(OH) 2. It was found that the GC/Ni(OH) 2 electrode acts as an effective electrocatalysis for the oxidation of hydrazine.

The Deactivation of Nickel Hydroxide to Hypophosphite Electrooxidation on a Nickel Electrode

The deactivation of nickel hydroxide to the electrooxidation of hypophosphite on anickel electrode was studied by means of in situ UV-Vis subtractive reflectance spectroscopy. Theexperimental results show that when the potential is lower than-1.0 V (SCE), the surfacc on nickelelectrode is free of nickel hydroxide, on which hypophosphite is active. When the potential movespositively to about-0.75V, two absorbency bands around 300 nm and 550 nm, which were ascribedto the formation of α-nickel hydroxide, were observed, nickel is oxidized to α-nickel hydroxide.Severe deactivation of the surface occurs when the nickel surface is covered with nickel hydroxide,which separates the hypophosphite ion from nickel substrate.

EFFECT OF ELECTROLESS PLATING COBALT UPON CHARACTERISTICS OF NICKEL HYDROXIDE ELECTRODEFORRECHARGEABLEALKALINEBATTERIES

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Electrochemical performance of nickel hydroxide doped with multi-wall carbon nanotubes

Nickel hydroxide doped with multi-wall carbon nanotubes(MCNTs)was synthesized by chemical coprecipitation method. The MCNTs doped nickel hydroxide was used as the electrochemical active material in the positive electrodes of rechargeable alkaline batteries.The powder X-ray diffraction(XRD)analysis shows that the addition of MCNTs induces more structural defect within the crystal lattice of the nickel hydroxide.The cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS) tests demonstrate the better reaction reversibility and lower electrochemical impedance of MCNTs doped nickel hydroxide as compared with the pure nickel hydroxide.The charge/discharge tests show that MCNTs addition can improve the specific discharge capacity and increase the discharge voltage of the nickel hydroxide electrode.

Effect of Lu_2O_3 on Charge/discharge Performances of Spherical Nickel Hydroxide at High Temperature

Nickel-metal hydride （Ni/MH） batteries are one of promising batteries for electric vehicle applications, but at high temperature the charge efficiency of nickel electrode is very low. In order to improve the high-temperature-efficiency of nickel electrode, spherical nickel hydroxide mixed with various ratios of Lu2O3 was used as active material of pasted nickel electrodes. The results of charge/discharge experiments, cyclic voltammetric measurements and XRD characterizations have shown that after addition of Lu2O3, the oxygen evolution overpotcntial is elevated much, the charge efficiency of nickel electrode at high temperature is greatly improved and the content of β-NiOOH phase increases in charged electrodes. In addition, the mixed ratio of Lu2O3 has different effects on high temperature performances of nickel electrode at different charge/discharge currents, 3.5 % is the optimum mixed ratio, and the action of Lu2O3 on high temperature electrochemical behaviors is more apparent when nickel electrodes are charged at small current than large current.

Porous Cobalt Oxide@Layered Double Hydroxide Core-Shell Architectures on Nickel Foam as Electrode for Supercapacitor

The high performance of an electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of electroactive materials.A porous core-shell architecture in which one-dimensional cobalt oxide(Co_3O_4)nanowire cores are grown on nickel foam prior to the growth of layered double hydroxide(LDH)shells is fabricated.Hydrothermal precipitation and thermal treatment result in homogeneous forests of 70-nm diameter Co_3O_4 nanowire,which are wrapped in LDH-nanosheet-built porous covers through a liquid phase deposition method.Due to the unique core-shell architecture and the synergetic effects of Co_3O_4and NiAl-LDH,the obtained Co_3O_4@LDH electrode exhibits a capacitance of 1 133.3F/g at a current density of 2A/g and 688.8F/g at 20A/g(5.3F/cm^(2 )at 9.4mA/cm^(2 )and 3.2F/cm^(2 )at 94mA/cm^2),which are better than those of the individual Co_3O_4nanowire.Moreover,the electrode shows excellent cycling performance with a retention rate of 90.4%after 3 000cycles at a current density of 20A/g.

Influence of Sodium Carbonate Amount on Crystalline Phase and Structure Stability for Doping Nickel Hydroxide

Alpha nickel hydroxide has better performances than commercial beta nickel hydroxide. However, the main defect is that α-phase is difficult to synthesize and easily transformed to β-phase Ni（OH）2 upon aging in a strong alkaline solution. In this study, the Al-Co, Al-Yb, Yb-Co and Al-Yb-Co multiple doping was used respectively. By controlling the amount of sodium carbonate, the α-Ni（OH）2 was prepared by ultrasonic-assisted precipitation. And the influence of sodium carbonate on the crystalline phase and structure stability for alpha nickel hydroxide was studied. The results demonstrate that, with increasing amount, the biphase nickel hydroxide transforms to pure alpha nickel hydroxide gradually, and the structure stability is also improved. When the amount of sodium carbonate is 2 g, the sample still keeps α-Ni（OH）2 after being aged for 30 days, for Al-Yb-Co-Ni（OH）2. And when the amount is less than 2 g, the phase transformations exist in the samples with different extents. These results demonstrated that the amount of sodium carbonate is a critical factor to maintain the structural stability of α-Ni（OH）2.

Electroless Co-Zn Surface-Modified Nickel Hydroxide as an Active Material for Pasted Nickel Electrodes

Chemically precipitated β type nickel hydroxide powder was surface modified by electroless deposition of Co Zn coatings,and physical properties of both the modified and unmodified nickel hydroxide were characterized by scanning electron microscopy (SEM), specific surface area (BET), X ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS). It has been found that Co and Zn components of the surface electroless coatings exist in the oxidized state. Electrochemical performances of pasted nickel electrodes using the modified nickel hydroxide as an active material were investigated, and compared with those of the electrodes prepared with the unmodified nickel hydroxide. Charge/discharge tests show that the modified nickel hydroxide electrodes exhibit better performances in the charge efficiency, specific discharge capacity and active material utilization. Their resistance to swelling with cycling is also superior to that of the unmodified nickel hydroxide electrodes. Cyclic voltammetric (CV) studies indicate that the modified electrodes have a higher electrochemical activity, and the porous pasted nickel electrodes have some distinguished CV characteristics in comparison with those of the thin film nickel electrodes.

An improved analysis method of constant-current charge/discharge curves and its application to nickel hydroxide electrode

The derivative of charge and discharge curves (d t /d E vs E plot) can be used to describe the charge and discharge process more exactly. The d t /d E ? 獷 plots of nickel hydroxide electrode at different charge/discharge rates and intermittent discharge experiment are discussed. Though the d t /d E ? 獷 plot is affected by many factors, it clearly has intrinsic relation with the nature of active material such as conductivity and thermodynamic potential of active material, which changes with the state of charge. The d t /d E—E plot can also be applied to other electrochemical active materials, especially to those having several phases during charge or discharge.

Electrochemical performance of multiphase nickel hydroxide

The high density nano-crystalline multiphase nickel hydroxide containing at least three doping elements was synthesized and its electrochemical characteristics were studied. The electrochemical behavior of the high density spherical multiphases α-Ni(OH)2 were also investigated. The results show that the structure of the material is a mixed phase of α-Ni(OH)2 and β-Ni(OH)2, which has a the same stabilized structure as α-Ni(OH)2 during long-term charge/discharge process. High density spherical multiphases α-Ni(OH)2 have a much better redox reversibility, a much lower oxidation potential of Ni(Ⅱ) than the corresponding oxidation state in the case of β-Ni(OH)2, and a much higher reduction potential. They exchange one electron during electrochemical reaction and have a higher proton diffusion coefficient. The mechanism of the electrode reaction is proton diffusion, and the proton diffusion coefficient is 5.67×10?10 cm2/s. Moreover, they reveal a higher discharge capacity than β-Ni(OH)2/β-NiOOH because they exchange one electron per nickel atom during charge/discharge process.