Nickel Doping Research Articles

First-Principles Study of Structural, Electronic and Thermoelectric Properties of Ni-Doped Bi2Se3

Direct conversion of waste heat to electrical energy could address present energy challenges. Bi2 Se3 is one of few thermoelectric materials known to operate at room temperature. Comprehensive analysis using density functional theory was conducted to explore the effect of nickel doping on structural, electronic, and thermoelectric properties of Bi2 Se3 . Local density approximation (LDA) was used with an addition of spin-orbit coupling (SOC) and van der Waals interaction scheme consideration. Analysis of the effect of SOC was elaborated. It was found that nickel has changed the crystal structure of Bi2 Se3 . Nickel has also changed band structure and density of state that alter the thermoelectric performance. The decreased band gap has decreased the thermopower. However, it gives advantages to the improvement of electrical conductivity. Higher electrical conductivity has risen thermal conductivity. Despite the decreased thermopower and increased thermal conductivity, the higher electrical conductivity has improved the overall thermoelectric performance of Bi2 Se3 when nickel is introduced.

Boosting oxygen evolution through phase and electronic modulation of highly dispersed tungsten carbide with nickel doping

Exploring efficient, stable, and earth-abundant electrocatalysts for oxygen evolution reaction (OER) is of great significance for clean and renewable energy conversion technologies. In this work, in situ uniform Ni-doped tungsten carbide (Ni/WCX) nanoparticles (~3 nm) on carbon nanofibers (Ni/WCX-CNFs) that were to function as efficient OER catalysts were developed. Both the composition and electronic state of tungsten carbide (WCX: W-WC-W2C) could be regulated through varied Ni coupling. Owing to the synergistic effect between Ni and WCX, the reaction kinetics were facilitated, resulting in improved OER activity with low overpotentials of η10 = 350 mV (modified glassy carbon electrode) and η10 = 335 mV (self-supporting electrode). This work opens a facile territory for the development of cost-effective and highly promising OER electrocatalysts for use in real life applications.

Enhanced photocatalytic activity on Vanadium-doped NiO nanostructures in natural sunlight

The contamination of water from industrial pollutants is the most significant concern for environment. Semiconductors have been at forefront of effective elimination of pollutants from waste water, with the tuning of bandgap and improving the photocatalytic activity. This work elaborates the hydrothermal synthesize of highly stable Nickel Oxide (NiO) and Vanadium-doped Nickel Oxide (V-NiO) nanoparticles. The undoped and doped Nickel Oxide nanoparticles were characterized for structural, morphological, thermal and optical properties. X-ray diffraction pattern reveals the V-NiO stabilized in cubic structure. Morphological analysis demonstrates that upon Vanadium doping NiO particles transform from network like structure to spherical nanoparticles. NiO and V-NiO nanoparticles have an average crystallite size of 42 nm and 26 nm which are well matched with particle size calculated from transmission electron micrographs. The photoluminescence study reveals that the Vanadium substitution specifically reduces the rate of recombination in NiO. The V-NiO catalysts exhibited noticeable red shift of absorption spectrum to the visible region in comparison with pure NiO. The functional groups were studied using Fourier Transform Infrared Spectroscopy (FTIR). The photocatalytic study by degradation of Xylenol Orange (XyO) under sunlight irradiation unveils that photocatalytic activity of NiO is enhanced on vanadium doping. Reaction kinetics investigation of XyO degradation revealed that the reaction obeys the pseudo-zero-order model with improved rate constant of 0.115 mol L−1S−1 and 0.225 mol L−1S−1 for NiO and V-NiO, respectively. The retention of high performance and structural stability of photocatalysts after four consecutive degradation cycles implies the reusability of the catalyst. Consequently, the V-NiO with high photocatalytic activity with improved cyclic stability is able to provide as a promising material in the field of environmental remediation.

Nickel-doped BaCo0.4Fe0.4Zr0.1Y0.1O3-δ as a new high-performance cathode for both oxygen-ion and proton conducting fuel cells

• BCFZY and Ni doped BCFZY cathodes are synthetized. • Ni doped BCFZY improves the oxygen ion and proton conductivity of the cathode. • BCFZYN has a good thermal stability and a reduced thermal expansion coefficient. • Ni doping enhances the ORR activity in both O-SOFCs and PCFCs. • BCFZYN exhibits a prominent stability in both symmetrical cell and single cell test. To develop a cathode with excellent oxygen reduction reaction (ORR) activity and durability at intermediate-to-low temperatures is significant to boost the advancement of solid oxide fuel cells (SOFCs), a fascinating energy conversion technology with low emissions and high efficiency. Perovskite oxides have been extensively developed as cathodes, and doping is an important strategy to alter the lattice diffusion and surface exchange properties of perovskites, to tailor catalytic performances for various redox reactions, including ORR for SOFCs. The reported BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3-δ (BCFZY) is a promising cathode for SOFCs. Herein, to further improve the performance of BCFZY at reduced temperatures, we systematically investigate the partial doping of B-sites with different metal elements, including Mn, Ni, Cu and Zn at a fixed content of 5%. Among them, it is found that Ba(Co 0.4 Fe 0.4 Zr 0.1 Y 0.1 ) 0.95 Ni 0.05 O 3-δ (BCFZYN) exhibits the lowest polarization impedance in both oxygen ion and proton conducting fuel cells. Based on conductivity relaxation experiments and oxygen and hydrogen permeation tests, it is found that nickel doping improves oxygen mobility, surface exchange kinetics, and bulk oxygen ion and proton conductivity. Thereby, a high ORR activity on oxygen ion and proton conducting electrolytes is achieved, reaching 0.038 and 0.607 Ω cm 2 at 550 °C, respectively. The cells with the BCFZYN electrode show outstanding operational stability (200 h of operation in a symmetrical cell and 1000 h of operation in a single cell). This suggests that the BCFZYN is a promising cathode of next-generation SOFCs.

Influence of bismuth doping on structural, electrical and dielectric properties of Ni–Zn nanoferrites

Bismuth doped Ni–Zn ferrites of the composition Ni0.5Zn0.5BixFe2-xO4 with (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.1) have been synthesized by a citrate precursor method. Bismuth was doped to tailor the properties of Ni–Zn spinel ferrite. X-Ray Diffraction (XRD) data was used to calculate lattice parameter, density, porosity and hopping length values which revealed that all annealed bismuth doped nickel zinc nanoferrites display a single phase cubic spinel structures. Average crystallite size was found to be in the range of 15–28 nm. Williamson-Hall method was used to deduce the average lattice strain experienced by the nanocrystalline. A tensile strain was observed with an increase in the bismuth concentration from x = 0.00 to x = 0.04 which leads to an expansion of lattice while a compressive lattice strain was observed for the concentration x = 0.06 due to contraction of the lattice. Fourier Transform Infra Red (FTIR) peaks confirmed the appearance of absorption bands at a wave number 405 cm−1 and at a wave number 580 cm−1 confirming tetrahedral and octahedral modes of vibrations respectively. I–V characteristics at 4 V voltage were studied at room temperature. A highly resistive behaviour of the samples of the order of 1010 Ω-cm was observed making these materials suitable for high frequency applications. The investigations on real part, imaginary part of dielectric constant and dielectric loss tangent were carried out in the frequency range 10 kHz to 10 MHz at room temperature. Dielectric behaviour showed that with an increase in concentration of bismuth, the value of real part of dielectric constant increases from 5.161 to 11.162 at 104 Hz frequency and the value of dielectric loss tangent decreases from 0.79 to 0.33. AC conductivity of all the samples was found to increase with an increase in frequency which is explained on the basis of Koop's Phenomenological theory.

Effect of Ni Doping on the Structural and Optical Properties of ZrO2 Thin Films

Transparent thin films of pure and nickel-doped ZrO2 with doping levels of 0, 1, 3 and 5 molar percentage were deposited through sol–gel dip coating and subsequently annealed at 500°C. Surface morphology and film thickness were examined through field emission scanning electron microscopy, which revealed a smooth surface morphology of the synthesized film, while elemental dot-mapping confirmed uniform distribution of nickel in the film. X-ray diffraction analysis revealed tetragonal crystalline structure of the deposited films. The structure exhibited a change in crystallite size upon varying the doping concentration. UV–Visible spectroscopy was employed for determining the optical band gap and transmittance. All the specimens were found to exhibit transmittance above 80%. Surface defects and oxygen vacancies were analyzed through photoluminescence spectroscopy. The photoluminescence peak intensities were observed to decrease upon increasing the nickel doping beyond 1% molar ratio, which was found to be in accordance with the change in optical band gap determined through UV–Visible spectroscopy. Fourier transform infrared spectroscopy revealed a strong absorption peak corresponding to Zr–O vibrational mode, while another peak corresponding to Ni–O vibrational mode was observed for nickel-doped samples, thereby implying replacement of some Zr4+ ions by Ni2+ ions in the lattice.

Nickel doping effect on structure and ac conductivity of resorcinol formaldehyde/SiO2-Ni nanocomposites synthesized by sol–gel process

The sol–gel synthesis of silica/carbon nanocomposite was modified with nickel in order to enhance the dispersion of silica nano-powder in the carbon matrix. The synthesized doped nanocomposite RF/SiO2-Ni5% (S-RF) is composed of carbon matrix based on resorcinol formaldehyde (RF) as observed in the X-ray diffraction patterns and by scanning electron microscopy characterization. The average sizes of the crystallite of the S-RF are presented in the 13–17 nm range. FTIR Spectroscopy analysis showed that the band at just about 1040 cm−1 is associated to vibrations of Si–O–Si. The addition of nickel improves the interaction between the matrix and the nanoparticles, which appears well at 1100 °C. Moreover, the influences of the doping of Ni in the S-RF nanocomposite were analyzed.

High-Temperature Hydrogen Sensing Performance of Ni-Doped TiO2 Prepared by Co-Precipitation Method.

This work deals with the substantially high-temperature hydrogen sensors required by combustion and processing technologies. It reports the synthesis of undoped and Ni-doped TiO2 (with 0, 0.5, 1 and 2 mol.% of Ni) nanoparticles by a co-precipitation method and the obtained characteristics applicable for this purpose. The effect of nickel doping on the morphological variation, as well as on the phase transition from anatase to rutile, of TiO2 was investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. The resistive sensors prepared with these powders were tested toward H2 at 600 °C. The results indicate that 0.5% Ni-doped TiO2 with almost equal amounts of anatase and rutile shows the best H2 sensor response (ΔR/R0 = 72%), response rate and selectivity. The significant improvement of the sensing performance of 0.5% Ni-doped TiO2 is mainly attributed to the formation of the highest number of n-n junctions present between anatase and rutile, which influence the quantity of adsorbed oxygen (i.e., the active reaction site) on the surface and the conductivity of the material.

Work function-tunable ZnO/Ag/ZnO film as an effective hole injection electrode prepared via nickel doping for thermally activated delayed fluorescence-based flexible blue organic light-emitting diodes

Metal-doped ZnO, as an alternative to indium tin oxide, has been extensively investigated; however, its widespread use has been limited because of its low conductivity and work function. In this study, ZnO was Ni-doped via co-sputtering to achieve work function tuning and improve its conductivity. The Ni-doped ZnO could be used as an effective hole injection electrode for organic light-emitting diodes (OLEDs). Herein, we prepared a Ni-doped ZnO/Ag/ZnO (Ni:ZAZ) electrode for thermally activated delayed fluorescence-based flexible blue OLEDs. The Ni:ZAZ electrode exhibited outstanding performance with a surface resistivity of 6.33 Ω/sq, high transmittance of 93.3% at 484 nm, and work function of up to 0.6 eV, along with a smooth surface and excellent mechanical durability. In addition, the Ni:ZAZ-based OLEDs exhibited excellent performance with a turn-on voltage of 3.0 V and a maximum current efficiency of 17.2 cd/A owing to its improved hole injection property. Furthermore, on flexible substrates, these OLEDs exhibited improved mechanical stability even after being subjected to 2000 bending cycles at a radius of curvature of 6 mm. Thus, the synthesis approach proposed in this study will pave a new pathway for the development of transparent electrodes for flexible and wearable opto-electronic devices.

Impedance analysis of charge transfer upon nickel doping in Tio2-based flexible dye-sensitized solar cell

Flexible dye-sensitized solar cells (FDSSCs) have promoted interest in plastic industries as they are lightweight, flexible, and mechanically robust to accelerate production and reduce cost. However, the plastic substrates have temperature limitations in producing the TiO2 photoanode and degrade the performance of FDSSC. The main reason for this degradation is the low charge transfer in the photoanode layer. Although there is plenty of research on low-temperature fabrication methods, they indirectly increase the operational cost. Therefore, a new approach is necessary for charge transfer improvement without affecting the temperature in a low-cost platform. In this study, we present a photoanode that improves the charge transfer by doping nickel (Ni) in the TiO2 layer. A low amount of Ni doping (15%) exhibited Rct >> Rt, indicating a high charge transport and low electron recombination rate (120.84 s−1). On the other hand, higher amount Ni doping (>> 45%) has Rct << Rt which deteriorates the performance of the cell by causing severe agglomeration issues, indicating a high electron recombination rate (369.75 s−1). Moreover, the high charge transfer in (TiO2)85-Ni15-based FDSSC facilitates the electron lifetime of the cell up to 8.28 ms. Therefore, an optimum doping of Ni in TiO2-based FDSSC is studied in this work.

Effect of nickel and manganese doping on the structure, morphology and the electrochemical performance of the silicon-carbon films

The effectiveness of “pure” silicon-carbon films and the films doped with manganese and nickel as electrode materials for supercapacitors has been investigated. The films have been obtained through the electrochemical deposition from the ethanol and hexamethyldisilazane solution with metal salts addition onto the copper foil. The Raman spectroscopy showed that the silicon-carbon films are complex heterogeneous objects. Electrodes based on the manganese and nickel-doped silicon-carbon films demonstrated the larger specific capacitance compared to “pure” silicon-carbon films (414 F/g and 90 F/g at 30 A/g, respectively). The equivalent serial resistance evaluated through the impedance spectrometry is about 0.5 Ω and 0.6 Ω for the “pure” silicon-carbon film and metal-doped films, respectively.

Synthesis, structural and physical properties of some rare-earth doped nickel chromites

A systematic investigation of structural, magnetic and transport properties of NiCr1.9R0.1O4 (R = Eu, Dy and Ho) has been undertaken. Rietveld analysis of powder X-ray diffraction data revealed that all the compounds crystallize in the cubic symmetry with space group having small volume fraction of orthorhombic phase RCrO3. Both a and V decreases with the substitution of heavier rare earth ion which is consistent with the decrease in ionic radius of rare earth ion. Temperature dependent magnetization studies showed that all our investigated compounds have negative value of Weiss constant (Θ) indicating the dominance of anti-ferromagnetic interactions in the samples. The phases are semi-conductors and the conduction mechanism was dominated by Arrhenius model in the high temperature paramagnetic semiconducting region.

Humidity sensing of thin film perovskite nanostructure for improved sensitivity and optical performance

This paper presents a humidity sensing based on perovskites nanostructured thin film for improved sensitivity and optical performance. The nickel-doped zinc thin oxide (NZTO) perovskites thin film was used as a sensing material for the humidity sensing application. The NZTO was deposited on borosilicate glass substrates via aerosol-assisted chemical vapour deposition (AACVD) and nickel (Ni) dopant with 2 %mol was added into the precursor solution. The optical performance was investigated by inserting the NZTO into the optical reflection cavity. The cavity comprises NZTO on the glass that placed in a fixed position in front of single-mode fiber (SMF) and SMF was adjusted using x-direction of the 3-axis stage to obtained different cavity lengths. The performance was evaluated from the free-spectral range (FSR) and extinction ratio (ER) of the different cavity lengths. Then, the cavity with an optimized length was placed inside the humidity chamber for sensing applications. The result shows that the optimized cavity length is 100 µm with FSR and ER of 12.05 nm and 7.247 dB. The sensitivity of the humidity sensing is 0.2657 nm/RH% indicates that the NZTO is an excellent candidate for humidity sensing application.

Nickel Doping in ZnO Nanorod Synthesis: Effects of Nickel Concentration on Physical Properties of the Nanorod

ZnO nanorods have successfully been grown on the surface of FTO. The growth of ZnO nanorods was carried out using the seed-mediated growth method, whereas the Ni doping was carried at different concentrations. The effect of nickel doping on ZnO nanorods was observed using field emission scanning electron microscope (FESEM), UV-Vis spectroscopy, and X rays diffraction (XRD). ZnO nanorods having hexagonal shape were shown by FESEM images, and overlap of ZnOnanorods forming a nanoflowers with wider rod size. UV-Vis spectra showed that strong absorption occurred at a wavelength of 390-300 nm, the highest intensity of absorption was resulted by 15mM sample. The energy gap of the sample decreased as increasing its concentration. XRD pattern of the samples showed the diffraction peaks occurred at angles of 2θ = 31.72°, 34.45°, 36.20°, 47.50°, and 56.57° that represented the crystal plane orientation of (100), (002), (101), (102), and (110).

INFLUENCE OF NICKEL DOPING CONCENTRATION ON THE CHARACTERISTICS OF NANOSTRUCTURE CuS PREPARED BY HYDROTHERMAL METHOD FOR ANTIBACTERIAL ACTIVITY

Pure and nickel doped copper sulfide (CuS) nanostructure were prepared by hydrothermal method for 5 h at [Formula: see text]C. Structural, morphological and optical properties of the CuS nanostructure were studied for different Ni-doping concentration of 1%, 2%, 3%, 4%, and 5 %. X-ray diffraction studies showed the polycrystalline nature with hexagonal phase structure of CuS and Ni: CuS nanostructure. FE-SEM image showed that nickel doping concentration affected the nanostructure morphology. The absorbance spectra were then recorded at wavelengths ranging from 350 nm to 1000 nm, where the CuS nanostructures have strong absorbance in the NIR. The optical band gap energy of the samples increased as nickel concentration increasing. In particular, their optical band gap energies were 3.25, 3.48, 3.49, 3.49, 3.45 and 3.44 eV for undoped and Ni-doped CuS nanostructure with concentrations (1%, 2%, 3%, 4% and 5%), respectively. The antibacterial activity of Copper sulfide nanostructure against P. aeruginosa, E. coli, and S. aureus was evaluated by zone of inhibition. The test revealed that copper sulfide nanostructure have a strong antibacterial activity against gram-positive than for gram-negative with low concentration of CuS.

Effect of doping (with cobalt or nickel) and UV exposure on the antibacterial, anticancer, and ROS generation activities of zinc oxide nanoparticles

ABSTRACT We describe the synthesis, structural and morphological characteristics of cobalt and nickel doped zinc oxide nanoparticles (ZnO NPs) by solution combustion technique by utilizing lemon juice as bio-fuel. Structural parameters were confirmed by the X-ray Rietveld refinement method, all the compounds were crystallized in the wurtzite hexagonal structure with space group P63mc (No. 186). Field emission scanning electron microscopy coupled with energy dispersive X-ray elemental mapping results revealed agglomerated spherical shaped particles and dopant ions were homogeneously distributed. Antibacterial, anticancer, and reactive oxygen species (ROS) generation activities were studied on undoped ZnO-, Co-, and Ni-doped ZnO nanoparticles upon un-exposed/exposed to ultraviolet radiations at 300 nm for 1 h. Antibacterial studies were performed against Salmonella enterica and Clostridium perfringens. Anticancer activity was tested on HeLa and MCF-7 cell lines. Generation of ROS was studied in J744 mouse macrophage cells. Doping of cobalt or nickel in the ZnO lattice enhanced antibacterial, anticancer, and oxidative response generation activities compared to undoped ZnO NPs. These activities were further improved upon exposure to ultraviolet radiations. Together, data indicate a direct activity of ZnO NPs against bacteria, cancer cells and simultaneously boosting host’s immunity via inducing activation of immune cells (mouse macrophage cells).

Electrical properties of Ni-doped Sm2O3 electrolyte

Nowadays, semiconductor ionic materials have drawn significant attention for developing new electrolytes in low temperature solid oxide fuel cells (LT-SOFCs). Here we investigate the effect of nickel doping on ionic conductivity of Sm2O3 as an electrolyte material for low temperature SOFCs. The amount of Ni ion doping has an intense effect on the electrochemical properties and power generation. An optimized composition of 10 mol% nickel doped samarium oxide (10NSO) as an electrolyte in the fuel cell has a high open circuit voltage (OCV) of 1.09 V and a notable power output of 1080 mW cm−2 at 520 °C. Further investigation revealed that the 10NSO displays a superior ionic conduction up to 0.26 S cm−1 at 520 °C. Moreover, the cell demonstrates high stability up to 80 h. The high electrochemical property and good stability recommend that the NSO is a favorable candidate for symmetrical SOFC electrolyte.

Rare-Earth Metals-Doped Nickel Aluminate Spinels for Photocatalytic Degradation of Organic Pollutants

Visible-light-activated photocatalysts based on samarium-doped, europium-doped, and gadolinium-doped nickel aluminates (SmNA, EuNA, GdNA) were synthesized. The spinel crystalline structures of the doped mixed metal oxides were demonstrated by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. The presence of the rare-earth metals (REMs) was confirmed by the energy-dispersive X-ray (EDX) studies. Ultraviolet-visible-near-infrared (UV-Vis-NIR) spectra revealed that the REMs-doped catalysts absorb in the full solar spectrum range covering both visible and near infrared wavelengths. Scanning electron microscopy (SEM) visualized the profound morphological alterations of the doped nickel aluminate samples. Consequently, the pore volume and the Brunauer-Emmett-Teller (BET) surface area decreased, while nanoparticles sizes increased. Fourier-transform infrared spectroscopy (FTIR) exposed that surfaces of REMs-doped nickel aluminates are rich in hydroxyl groups. Finally, the photocatalytic performance was notably increased through doping nickel aluminate (NA) with REMs; the highest activity was observed for EuNA.

NEXAFS–Spectra and Magnetic Susceptibility of Nickel and Chromium Doped of Bismuth Niobate

The electronic state and character of exchange interactions of nickel and chromium atoms in solid solutions of Bi5Nb3-3xМ3xO15-δ (М-Cr,Ni) was researched by methods of magnetic susceptibility and NEXAFS-spectroscopy. NEXAFS spectra of nickel and chromium oxides were obtained. According to X-ray spectroscopy in solid solutions, chromium atoms are mainly in the charge state of Cr(III), and nickel atoms in the high-spin state of Ni(II) in octahedral coordination. In solid solutions, paramagnetic chromium and nickel atoms are present in the form of monomers and clusters with a common antiferromagnetic type of exchange

Effects of the alloying elements ratio in the Ni–Al–Cr–W–Mo–Ta system on the thermal fatigue resistance of the deposited metal

The article presents an analysis of the influence of the alloying elements ratio in the Ni-Al-Cr-WMo-Ta system on the resistance of the deposited metal against thermal fatigue. The combined effect of alloying elements on the crack resistance of weld metal under cyclic temperature changes in the range of 20–1150°C is established. It is shown that in the alloying system, the sensitivity of a metal to the formation of thermal fatigue cracks mainly depends on the number of refractory elements that cause the formation of topologically closepacked (TCP) phases. The content in the deposited metal of 3.5 wt.% tungsten, 3.0 wt.% molybdenum, 2.5 wt.% tantalum does not cause the appearance of fatigue cracks. The developed deposited metal provides high level of thermal and oxidation wear resistance compared to highly doped nickel and cobalt industrial alloys.