Cobalt-doped Nickel Research Articles

Cobalt-Doped Nickel Phosphite for High Performance of Electrochemical Energy Storage.

Compared to single metallic Ni or Co phosphides, bimetallic Ni-Co phosphides own ameliorative properties, such as high electrical conductivity, remarkable rate capability, upper specific capacity, and excellent cycle performance. Here, a simple one-step solvothermal process is proposed for the synthesis of bouquet-like cobalt-doped nickel phosphite (Ni11 (HPO3 )8 (OH)6 ), and the effect of the structure on the pseudocapacitive performance is investigated via a series of electrochemical measurements. It is found that when the cobalt content is low, the glycol/deionized water ratio is 1, and the reaction is under 200 °C for 20 h, the morphology of the sample is uniform and has the highest specific surface area. The cobalt-doped Ni11 (HPO3 )8 (OH)6 electrode presents a maximum specific capacitance of 714.8 F g-1 . More significantly, aqueous and solid-state flexible electrochemical energy storage devices are successfully assembled. The aqueous device shows a high energy density of 15.48 mWh cm-2 at the power density of 0.6 KW cm-2 . The solid-state device shows a high energy density of 14.72 mWh cm-2 at the power density of 0.6 KW cm-2 . These excellent performances confirm that the cobalt-doped Ni11 (HPO3 )8 (OH)6 are promising materials for applications in electrochemical energy storage devices.

Synthesis of cobalt-doped nickel sulfide nanomaterials with rich edge sites as high-performance supercapacitor electrode materials

Edge site enrichment enhanced the electrochemical performance of Ni0.75Co0.25S2 for supercapacitor application.

LiNi0.8Co0.15Al0.05O2 Cathode Material: New Insights via 7Li and 27Al Magic-Angle Spinning NMR Spectroscopy

Aluminum doped mixed metal oxides are popular positive electrode materials for Li-ion batteries. They are used extensively in many applications, yet their operation and limitations are not entirely understood. This work shows the advantage of using solid-state 7Li and 27Al NMR for monitoring the electrochemical properties of the doped nickel–cobalt oxide cathode material, LiNi0.8Co0.15Al0.05O2 (NCA), particularly during the first few charge/discharge cycles. The changes in the state of the material as lithium ions are intercalated and deintercalated during discharge and charge, respectively, are highlighted via the Li nuclei as a dynamic reporter and the Al nuclei as a static, material-embedded reporter. In particular, the NMR view of the cyclic change of Ni ions between paramagnetic and diamagnetic oxidation states is enhanced by monitoring both nuclei. Two protocols of cycling the NCA electrode are compared: one employing a smaller voltage window, cycled against graphite as anode, and one using a wider ...

Microwave Assisted Combustion Synthesis and Characterization of Nanocrystalline Nickel-doped Cobalt Ferrites

Nanoparticles nickel-doped cobalt ferrites [NixCo1-xFe2O4 (x = 0.0, 0.25, 0.50, 0.75 and 1.0 of Ni2+)] were prepared by the microwave combustion synthesis, using a stoichiometric mixture of metal nitrates and urea as the oxidizer and fuel to drive the reaction. The effect of microwave irradiation on the phase composition was favorable to promote the formation of fluffy foams and nanoparticles sizes. The fast internal heating with microwaves leads to a reduction in synthesis time, to only 2 min. The structural, chemical and magnetic properties of the nickel-doped cobalt ferrites were analyzed by XRD, TEM, SEM and BET. The XRD results confirmed the formation of pure and single-phase spinel structure. The crystallite size of the nanoparticles was in the range of 38 - 50 nm. SEM images show nanoparticles with spherical shape and homogenous morphology. The TEM analysis shows necked near-spherical particles with an average size of ~30 - 50 nm, reflecting the highly crystalline nature of these nanoparticles. The magnetic measurements of all the samples were recorded using vibrating sample magnetometer (VSM) at room temperature in 10 kOe. Increasing the nickel content directly affects the structural characteristics of the particles, causing a reduction in the coercive field.

ZrxCo0.8−xNi0.2−xFe2O4-graphene nanocomposite for enhanced structural, dielectric and visible light photocatalytic applications

Zirconium doped nickel cobalt ferrite (ZrxCo0.8−xNi0.2−xFe2O4) nanoparticles and ZrxCo0.8−xNi0.2−xFe2O4-graphene nanocomposites were synthesized by a cheap and facile co-precipitation method. Annealing was done at 750°C for 6.5h. Spinel cubic structure of prepared nanoparticles was confirmed by X-ray powder diffraction (XRD) technique. Crystalline size of nanoparticles was observed in the range of 18–27nm. Graphene was synthesized by Hummer's method. Formation of rGO was confirmed by UV-visible spectroscopy (UV-vis) and XRD. ZrxCo0.8−xNi0.2−xFe2O4-graphene nanocomposites were prepared by ultra-sonication route. Grain size of nanoparticles and dispersion of nanoparticles between rGO layers was determined by Scanning electron microscopy (SEM). In application studies of nanoparticles and their nanocomposites, photocatalytic efficiency of nanoparticles under visible light irradiation was observed by degradation of methylene blue. Charge transfer resistance was measured by electrochemical impedance spectroscopy (EIS) and the variation in dc electrical resistivity was analyzed by room temperature current voltage characteristics (I-V). Dielectric constant was also evaluated in frequency range from 1MHz to 3GHz. All these investigations confirmed the possible utilization of these materials for a variety of applications such as visible light photocatalysis, high frequency devices fabrication etc.

Experimental demonstration of all-optical weak magnetic field detection using beam-deflection of single-mode fiber coated with cobalt-doped nickel ferrite nanoparticles.

We experimentally demonstrate single-mode optical-fiber-beam-deflection configuration for weak magnetic-field-detection using an optimized (low coercive-field) composition of cobalt-doped nickel ferrite nanoparticles. Devising a fiber-double-slit type experiment, we measure the surrounding magnetic field through precisely measuring interference-fringe yielding a minimum detectable field ∼100 mT and we procure magnetization data of the sample that fairly predicts SQUID measurement. To improve sensitivity, we incorporate etched single-mode fiber in double-slit arrangement and recorded a minimum detectable field, ∼30 mT. To further improve, we redefine the experiment as modulating fiber-to-fiber light-transmission and demonstrate the minimum field as 2.0mT. The device will be uniquely suited for electrical or otherwise hazardous environments.

Synthesis and Characterization of Electrospun Nickel Doped Cobalt(II, III) Nanofibers with Application to Maltose Determination

Nickel doped cobalt(II, III) composite nanofibers were prepared by an electrospinning and sequential calcination process, and characterized by scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction. An electrospun nickel doped cobalt(II, III) modified carbon paste electrode was used for maltose determination using cyclic voltammetry and amperometry. Under the optimized conditions, a linear response was obtained between 0.2 and 100.0 µM, with a low detection limit of 32.5 nM.

Combination of Asymmetric Supercapacitor Utilizing Activated Carbon and Nickel Oxide with Cobalt Polypyridyl-Based Dye-Sensitized Solar Cell

A dye-sensitized solar cell (DSC) based on the metal-free organic sensitizer and the cobalt (II, III) polypyridyl electrolyte was integrated here within an asymmetric supercapacitor utilizing cobalt-doped nickel oxide and activated carbon as positive and negative electrodes, respectively. A low cost nickel foil served as intermediate (auxiliary) bifunctional electrode separating two parts of the device and permitting the DSC electrolyte regeneration at one side and charge storage within cobalt-doped nickel oxide at the other. The main purpose of the research was to develop an integrated photocapacitor system capable of both energy generation and its further storage. Following irradiation at the 100 mW cm−2 level, the solar cell generated an open-circuit voltage of 0.8V and short-circuit current of 8mAcm−2 which corresponds to energy conversion efficiency of 4.9%. It was further shown that upon integration with asymmetric supercapacitor, the photogenerated energy was directly injected into porous charge storage electrodes thus resulting in specific capacitance of 32 F g−1 and energy density of 2.3 Wh kg−1. The coulumbic and total (energy conversion and charge storage) efficiency of photocapacitor were equal to 54% and 0.6%, respectively.

Ni0.1Co0.9Fe2O4-based electrochemical sensor for the detection of paracetamol

A novel electrochemical sensor based on nickel-doped cobalt ferrite nanoparticles (Ni0.1Co0.9Fe2O4)-modified glassy carbon electrode (NCF/GCE) was presented for the sensitive detection of paracetamol. Experimental conditions such as pH, applied potentials and concentration were investigated using cyclic voltammetric and chronoamperometric techniques. The modified electrode exhibited excellent catalytic response towards the oxidation of paracetamol with good reproducibility. The overpotential for oxidation of paracetamol is decreased, and the current response enhanced significantly on the modified electrode in comparison with that of bare electrode. Linear calibration curve is obtained over the range 2 μM to 8,000 μM having a detection limit of 11 nM. The modified electrode facilitated the simultaneous detection of paracetamol, ascorbic acid, and dopamine with good reproducibility.

Effect of cobalt doping on microstructural and optical properties of nickel oxide thin films

In this study, transparent thin films of cobalt-doped nickel oxide (CoxNi1−xO; x=0, 0.005, 0.01, 0.05, 0.075 and 0.15) were deposited on to microscopic glass substrates using a spray pyrolysis technique. The effect of cobalt doping on structural, morphological and optical properties was investigated. XRD studies reveal that all the films are polycrystalline with cubic structure and exhibit (111) preferential orientation. Co is well incorporated in the host lattice, i.e. octahedrally coordinated on the Ni site without altering the structure. The effect of Co doping was observed to have a strong influence on the surface morphology of NiO films. An interesting correlation between the optical transmittance and the RMS roughness was observed. All the coatings retain high transparency throughout the visible spectral regime. The optical band gap varies from 3.44eV to 3.26eV due to the presence of Ni vacancies and/or oxygen defects. The optical reflectance spectra along with refractive index and extinction coefficients of the prepared films have also been discussed. Among all the Co-doped NiO thin films in this study, films doped with 1 at% Co concentration exhibited the best properties, namely improved crystallinity, smooth and compact surface morphology, lowest RMS roughness value of 2.26nm and highest transmittance of ~85% in the visible region.

Hierarchical nanostructured NiCo2O4 as an efficient bifunctional non-precious metal catalyst for rechargeable zinc–air batteries

A nickel-doped cobalt oxide spinel structure is a promising non-precious metal electrocatalyst for oxygen evolution and oxygen reduction in rechargeable metal-air batteries and water electrolyzers operating with alkaline electrolytes. One dimensional NiCo2O4 (NCO) nanostructures were prepared by using a simple electrospinning technique with two different metal precursors (metal nitrate/PAN and metal acetylacetonate/PAN). The effect of precursor concentration on the morphologies was investigated. Single-phase, NCO with an average diameter of 100 nm, porous interconnected fibrous morphology was revealed by FESEM and FETEM analysis. The hierarchical nanostructured 1D-spinel NiCo2O4 materials showed a remarkable electrocatalytic activity towards oxygen reduction and evolution in an aqueous alkaline medium. The extraordinary bi-functional catalytic activity towards both ORR and OER was observed by the low over potential (0.84 V), which is better than that of noble metal catalysts [Pt/C (1.16 V), Ru/C (1.01 V) and Ir/C (0.92 V)], making them promising cathode materials for metal-air batteries. Furthermore, the rechargeable zinc-air battery with NCO-A1 as a bifunctional electrocatalyst displays high activity and stability during battery discharge, charge, and cycling processes.

Nickel-doped cobalt ferrite nanoparticles: efficient catalysts for the reduction of nitroaromatic compounds and photo-oxidative degradation of toxic dyes.

This study deals with the exploration of NixCo₁-xFe₂O₄ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) ferrite nanoparticles as catalysts for reduction of 4-nitrophenol and photo-oxidative degradation of Rhodamine B. The ferrite samples with uniform size distribution were synthesized using the reverse micelle technique. The structural investigation was performed using powder X-ray diffraction, high-resolution transmission electron microscopy, energy dispersive X-ray and scanning tunneling microscopy. The spherical particles with ordered cubic spinel structure were found to have the crystallite size of 4-6 nm. Diffused UV-visible reflectance spectroscopy was employed to investigate the optical properties of the synthesized ferrite nanoparticles. The surface area calculated using BET method was found to be highest for Co₀.₄Ni₀.₆Fe₂O₄ (154.02 m(2) g(-1)). Co₀.₄Ni₀.₆Fe₂O₄ showed the best catalytic activity for reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH4 as reducing agent, whereas CoFe₂O₄ was found to be catalytically inactive. The reduction reaction followed pseudo-first order kinetics. The effect of varying the concentration of catalyst and NaBH₄ on the reaction rates was also scrutinized. The photo-oxidative degradation of Rhodamine B, enhanced oxidation efficacy was observed with the introduction of Ni(2+) in to the cobalt ferrite lattice due to octahedral site preference of Ni(2+). Almost 99% degradation was achieved in 20 min using NiFe₂O₄ nanoparticles as catalyst.

Supercapacitor behaviour of cobalt-doped nickel oxide films

Ordered nanostructured cobalt-doped nickel oxide films were prepared on a conducting glass substrate via the sol–gel dip-coating method. X-ray diffraction analysis shows the films to be amorphous. Field-emission scanning electron microscope images showed well-defined, ordered grains with pores in between them. Supercapacitor behaviour was studied using cyclic voltammetry. A maximum specific capacitance of 1982 F/g at a scan rate of 5 mV/s with 1 M KOH was obtained for 5 wt% of cobalt-doped nickel oxide films. AC impedance analysis showed that the solution resistance was R s = 27 Ω and the charge transfer resistance R ct = 20 Ω.

Synthesis and characterization of nanosize nickel-doped cobalt ferrite obtained by precursor combustion method

Nanoparticles of the spinel ferrite, Co1−x Ni x Fe2O4 (x = 0, 0.2, 0.3) have been synthesized by the precursor combustion technique. Novel precursors of metal fumarato-hydrazinate have been employed to yield the nanosized spinel ferrite. A characteristic feature of these precursors is that they decompose autocatalytically after ignition to give the monophasic nanocrystalline ferrite. This fact is corroborated by X-ray powder diffraction analysis. The thermal decomposition pattern of the precursors has been studied by isothermal thermogravimetric and differential thermal analysis. In order to fix the chemical composition, the precursors have been characterized by FTIR and chemical analysis and their chemical composition has been fixed accordingly. The Curie temperature of the “as-prepared” oxide was determined by alternating current susceptibility measurements.

Influence of Cobalt Nanoparticles’ Incorporation on the Magnetic Properties of the Nickel Nanofibers: Cobalt-Doped Nickel Nanofibers Prepared by Electrospinning

Among the common ferromagnetic metals, cobalt has distinct magnetic properties, so incorporation of cobalt nanoparticles in the nickel nanofibers, which reveals better magnetic properties compared with the bulk, might have considerable impact. In this study, we are introducing cobalt-doped nickel nanofibers prepared by electrospinning. Electrospinning of a colloidal solution rather than a sol-gel (which is widely utilized in the conventional electrospinning technique) has been invoked as a novel strategy to prepare cobalt nanoparticles/ nickel acetate/poly(vinyl alcohol) nanofiber mats. Physiochemical characterizations indicated that calcination of the dried electrospun mats in argon atmosphere at 700 °C for 5 h leads to produce cobalt-doped nickel nanofibers. Overall, magnetic properties studied pointed to improvement of the magnetic parameters of the synthesized cobalt-doped nickel nanofibers compared with the pristine ones.

Effect of cobalt substitution on structural, magnetic and electric properties of nickel ferrite

A series of cobalt-doped nickel ferrite with composition of Ni (1− x) Co x Fe 2O 4 with x ranges from 0.0 to 0.8 (in steps of 0.2) was prepared by using standard ceramic technique. The confirmation of single-phase formation and structural analysis were carried out by employing X-ray diffraction technique. The electrical DC resistivity measurement was done by using usual two probe method in the temperature range from room temperature to 600 °C. Room temperature resistivity measurements show the decrease in resistivity with increase of cobalt concentration. The studies on resistivity as a function of temperature shows that all the sample obeys the semiconducting behavior. B–H hysteresis measurement was carried out at room temperature under the field of 2.4 kOe and this measurement with the increase of Co 2+concentration yields the monotonic increase of saturation magnetization ( M s) and decrease in coercive field ( H c) at higher Co 2+concentration ( x > 0.4). Ferrites with such behavior are important for magnetic recording media. In view of this, we have studied the various properties of Co-doped Ni ferrite.

Electrochemically Imprenated Aluminum-Stabilized α-Nickel Hydroxide Electrodes

Nickel-positive electrodes obtained by electrochemical impregnation of aluminum-substituted alpha-nickel hydroxide are found to deliver a reversible discharge capacity of ca. 450 mAh/g. This is much higher than the capacity of beta-nickel hydroxide electrodes [200 mAh/g: this work; 225 mAh/g: Dixit et al., J. Power Sources, 63, 167 (1996)] prepared under identical conditions and pasted electrodes comprising cobalt-doped nickel hydroxide [345 mAh/g: Faure et al., J. Power Sources, 36, 497 (1991)]. These observations suggest that the theoretical target-capacity for high-performance nickel-positive electrodes must be revised from the currently accepted value of 289 mAh/g (le exchange) to 491 mAh/g [1.7e exchange: Corrigan and Knight, J. Electrochem. Soc., 136, 613 (1989)]. (C) 1999 The Electrochemical Society. S1099-0062(98)08-044-4. All rights reserved.

Optical fiber magnetic field sensors with ceramic magnetostrictive jackets

Optical fibers coated by magnetostrictive ceramic films were tested with a Mach-Zehnder interferometer in an open-loop mode. The sensors exhibited excellent linearity and good sensitivity. The response of ceramic-jacketed fibers was not affected by small dc fluctuations that are due to the linear behavior of tested ceramic coatings in low magnetic fields. Tested ceramic materials included magnetite, γ-Fe(2) O(3), nickel ferrite, and cobalt-doped nickel ferrite (NCF2) jackets. The latter showed the best performance. A minimum detectable field of 3.2 × 10(-3) A/m for optical fiber jacketed with 2-μm-thick and 1-m-long NCF2 material has been achieved. The capability of detecting magnetic fields as low as 2.6 × 10(-7) A/m with a 10-μm-thick cobalt-doped nickel ferrite jacket is proposed.

Sintering of cobalt-doped nickel oxide

The influence of Co additions on the sintering of nickel oxide was studied. On the basis of the density, specific surface area and Me3+ ion concentration changes, in the Co y Ni1−yO samples, having 0, 1, 5 and 10 cation % of Co, a positive effect of Co ions on the densification was assumed, during sintering at 500 to 900° C in an argon atmosphere. Using special heat-treatment, the differences in specific surface area of the investigated powders were eliminated. The differences in green densities were excluded as well and from the results, it was possible to show that dissolved Co ions enhance nickel oxide densification process.

Precision measurements of cell dimensions of certain cobalt-doped nickel ferrites

Careful experimental techniques combined with suitable mathematical corrections of the experimental data have yielded accurate values of the cell dimensions of ferrites of composition Ni 1− x Co x Fe 2 O 4. The implications of the changing cell dimensions are discussed in terms of the valuance of cobalt.