Effect Of Ni Doping Research Articles

Improving the p–type conductivity of Cu2O thin films by Ni doping and their heterojunction with n–ZnO

Cu2O is one of the few transition metal oxides which can exhibit p–type conductivity due to native acceptor defects. Further improvements in the p–type conductivity of Cu2O can be achieved via extrinsic doping and post–growth processing. In this work, we investigate the effects of Ni doping in Cu2O with Ni content up to ∼11%. A variety of analytical techniques were utilized to investigate the structural, optical and electrical properties of these alloy thin films. We find that the incorporation of Ni improves the p–type conductivity of the films without altering the Cu2O crystallographic structure and maintains a wide bandgap of ∼2.5 eV. X–ray photoelectron spectroscopy (XPS) measurements reveal that the Fermi level moves closer to the valence band with increasing x, in agreement with the increasing hole concentration. Significant improvement in the crystallinity as well as the p–type conductivity of the alloy films can be observed after rapid thermal annealing (RTA). In particular, alloys with x≥0.005 exhibit a high hole mobility µ∼12–22 cm2/V-s with low resistivity of ρ∼30–60 Ω-cm and free hole concentration N∼1×1016 cm-3 after RTA in air–N2 ambient at 700°C. Such improvement can be attributed to the formation of Cu vacancies which promotes Ni substitution in the presence of small amount O2 in the air–N2 annealing environment. Finally, we fabricated a transparent p–(NixCu1-x)2O/n–ZnO heterojunction and evaluated its junction performance. XPS measurements reveal a type II band offset of this heterojunction with valence band and conduction band offsets of 2.81 eV and 2.07 eV, respectively. The heterojunction exhibits both rectification and photovoltaic response, demonstrating its potential for p–n junction and photodetection devices.

Promotion effect of Ni doping on the oxygen resistance property of Fe/CeO2 catalyst for CO-SCR reaction: Activity test and mechanism investigation

Catalytic reduction of NO using CO, which is usually present in the flue gas of the iron and steel industry, is considered as an economical and eco-friendly de-NOx method (CO-SCR). However, the oxygen present in the flue gas will significantly inhibit the CO-SCR activity of the catalyst, thereby limiting its industrial application. Herein, catalysts based on iron and cerium oxides were prepared and modified with different metals to investigate their performance for the CO-SCR reaction in the presence of oxygen. The results show that the Fe/CeO2 catalyst can reach 99% NO conversion at 200 °C, but its activity decreased dramatically to 42.7% when the oxygen is present (0.5 vol%). By contrast, the NO conversion of Ni-doped Fe/CeO2 catalyst demonstrated significant enhanced oxygen resistance and could achieve 92% even at 150 °C in the presence of 0.5 vol% oxygen. Characterization techniques such as N2 adsorption, XRD, SEM/TEM, XPS, H2-TPR, and in situ DRIFT were employed to investigate the mechanism of the improved oxygen resistance property of Ni-doped catalyst. The results show that the doped Ni can interact with Fe species, increases the BET surface area of the catalyst and generates more surface oxygen vacancies (SOV) and surface synergetic oxygen vacancy (SSOV) in CO-SCR reaction, thereby improving the redox performance of the catalyst. In situ DRIFT results show that the better redox performance of NiFe/CeO2 catalyst is conducive to the conversion of adsorbed NOx species to the reactive intermediate NO2- species during the reaction. Meanwhile, the enhanced SOV/SSOV in the NiFe/CeO2 catalyst can remain active in the presence of oxygen. Therefore, the NiFe/CeO2 catalyst exhibits a promising catalytic activity in CO-SCR reaction when oxygen is present.

Ni-doping Cu-Prussian blue analogue/carbon nanotubes composite (Ni-CuPBA/CNTs) with 3D electronic channel-rich network structure for capacitive deionization

Intercalation materials are of considerable interest for capacitive deionization (CDI) due to the rigid open framework and energy storage ability. However, low conductivity and stability restrict its application. In this work, a redox-active intercalation cation electrode based on 3D network Ni-doping Cu-Prussian blue analogue NixCu1-x[Fe(CN)6]1-γ (NCP-2, γ < 1) interwoven with CNTs (NCP/CNT) is synthesized. Experiments illustrate that the dual strategy of Ni doping and the insert of CNTs reduce the vacancy and crystal water in the lattice, resulting in a maximum capacity of 373.6 F·g−1 and better cycling stability. NCP/CNT║active carbon (AC) cell delivers a high adsorption capacity of 41.25 mg·g−1 with less energy consumption of 0.1080 kWh·kg−1 in 500 ppm NaCl solution. The outstanding salt adsorption depends on the rapid Fe3+/Fe2+ and Cu2+/Cu+ redox cycle, shortened Na+ diffusion path and fast electron transport. The effect of Ni doping was explored by DFT calculations, which proved it enhanced the electron density of Fe atom, stabilized the skeleton structure, increased the conductivity of PBA materials and facilitated the insertion of Na+. After CNT inserting, abundant electronic conductive channels formed among PBA nanoparticles. Hence, this work provides a feasible strategy to construct highly efficient electrodes with less energy consumption for CDI applications.

Synchrotron based x-ray absorption spectroscopy investigation and temperature dependent ferroelectric properties of Ni doped BaTiO3 nanostructures

In this report, the local structure geometry of BaTi1-xNixO3 (0.0 ≤ x ≤ 0.06) ceramics has been studied through synchrotron based x-ray-absorption spectroscopy, measured at the Ti K, Ba L3 and Ni K-edges at room temperature. The x-ray absorption near edge spectroscopy (XANES) at Ti K-edge confirms the TiO6 octahedron geometry of Ti atom due hybridization between Ti(3d)-O(2p) orbitals and signifies the non-centrosymmetric nature of BaTiO3 samples. However, Ti–O off-center displacement (non-centrosymmetric) is disturbed under the effect of Ni doping as a result of oxygen vacancies formation. More interestingly, XANES studies at Ni K-edge ensure successful substitution of Ni in BaTiO3 as Ni2+ ions. Extended x-ray absorption fine structure (EXAFS) data at Ni K-edge have been fitted to estimate pertinent local structural parameters of the Ni–O, Ni–Ba, Ni–Ti and Ni–Ni shells (viz. bond lengths and disorder parameters) and it also reveal that the structural disorders around the Ti sites in the doped BaTiO3 expand with Ni doping. The mixed-valence states of titanium ion, i.e., Ti4+ and Ti3+ in the doped samples were established with the x-ray photoelectron spectroscopy (XPS). Moreover, XPS divulges the creation of oxygen vacancies due to Ni doping in BaTiO3 matrix. The complementary information about the lattice vibration is analyzed through Raman studies that approve the softening of the transverse optical (TO) mode present at 515 cm−1. The temperature dependent ferroelectric studies affirm that the ferroelectricity vanishes in the doped samples due to the decrement in the off-center displacement between the Ti4+ and O2− ions in the TiO6 octahedral geometry. Differential thermal analysis (DTA) exhibits a ferroelectric tetragonal to para-electric cubic phase transition in the pristine as well as Ni doped BaTiO3 samples.

Promotion effects of Ni-doping on H2S removal and ZnO initial sulfuration over ZnO nanowire by first-principle study

H2S removal and ZnO initial sulfuration over ZnO nanowire are investigated using density functional theory (DFT) calculations, and the promotion effects of Ni-doping are discussed in detail. H2S can molecularly and dissociatively adsorb on pure and Ni-doped ZnO. Our results suggest that H2S prefers to adsorb dissociatively at Ni atom, mirrored by lower dissociated adsorption energies. For H2S removal, H2O formation is generally difficult on ZnO with a high energy barrier of approximately 2 eV. In contrast, we demonstrate that Ni could significantly promote H2O formation. The SH group at Ni site directly serves as hydrogen source for OH hydrogenation to form H2O, with much lower energy barriers of less than 1 eV. The retained S atom nearby Ni more easily penetrates toward inner sites of ZnO bulk. The present work clearly indicates that H2S removal and ZnO initial sulfuration preferentially occur in the vicinity of Ni dopant.

Investigation of The Effects of Ni-Doping on The Structural Properties of Fe2O3

Sunulan çalışmada, Ni katkısının yaş kimyasal yöntemle hazırlanan Fe2O3’ün yapısal özellikleri üzerine etkileri X-ışını kırınımı (XRD), Fourier dönüşümlü kızılötesi (FTIR), diferansiyel termal analiz (DTA), termogravimetrik analiz (TGA) ve taramalı elektron mikroskopisi (SEM) teknikleri kullanılarak araştırıldı. XRD ve FTIR sonuçları her bir numune için Fe2O3 yapının oluşumunu destekledi. 4at.%Ni katkısına kadar yeni bir faz oluşumu gözlenmedi ve bu numune için NiO ikincil fazının oluşumu tespit edildi. Kristal yapı ilişkili parametreler ve morfoloji, Ni içeriğinden etkilendi. Özetle Ni, Fe2O3 yapının bazı özelliklerini kontrol etmek için kullanılabilir.

Construction of Ni doped MoO3 nanostructures and their application as counter electrode in dye-sensitized solar cells

In this research, we propose to develop a sustainable, affordable and non-toxic material in dye sensitized solar cells for counter-electrodes (DSSCs). As a low-cost equivalent to platinum, we describe a facile aqueous hydrothermal solution-processed nickel (Ni) doped molybdenum oxide (MoO3) counter electrode. The Ni concentration in to MoO3 was varied from 0 to 10 mol.%. The effect of Ni dopant on the microstructure, particle size and optical behavior of MoO3 was systematically investigated. The 10% Ni incorporated MoO3 showed high absorption in the visible light with optical band gap energy is close to 2.98 eV. The optimized CE with 10% Ni-MoO3 (NMO10) showed outstanding photo conversion efficiency (8.39%), long term stability and higher electrocatalytic activity. The order of the photovoltaic and electrocatalytic properties are NMO10 > NMO5 > NMO2 > MoO3. In addition, the Rct value of this electrode is lower and shows a lower resistance to charge transfer and higher electrocatalytic activity. The improved photoconversion mechanism of Ni in to MoO3 was also described in detail.

Surface-modified ultra-thin indium tin oxide electrodes for efficient perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) are promising lighting sources owing to their unique optical and electrical properties, such as high color purity and charge carrier mobility. Various material strategies have been reported to increase the radiative recombination rate and alleviate the non-radiative recombination rate of PeLEDs. However, PeLEDs are prone to low device efficiencies owing to the metal-induced exciton quenching caused by the diffusion of metal species from the indium tin oxide (ITO) electrodes into the emissive layer. Herein, we demonstrate that surface modification of ITO by means of electric-field-induced Ni doping treatment prevents the diffusion of metal species and helps tune the work function. The effects of Ni doping on ITO (Ni-ITO) are clarified by conducting X-ray photoelectron spectroscopy, time of flight-secondary ion mass spectrometry, and energy level investigations. A PeLED fabricated using Ni-ITO as the anode exhibited a maximum current efficiency of 91.11 cdA-1 and external quantum efficiency of 20.48%, which are 13.5% and 13.9% higher than those of the PeLED fabricated using a commercially available ITO film (with a thickness of 180 nm), respectively. The results of this study can be used as guidelines to increase the quantum efficiencies of ITO-based organic/inorganic emitter devices and PeLEDs.

Synergistic doping and tailoring: Realizing in depth modulation on valence state of CoFe spinel oxide for high-efficiency water oxidation

Modifying the valence of metal active center to the favorable configuration offers a promising strategy to promote the electrocatalytic performance of water splitting. For example, Co2+ is reported to show better performance of water oxidation than Co3+ in the Co-based spinel oxide, but its adjustment degree is small due to the geometrical occupation and the uniform synthetic environment. In this work, on the basis of chemical tailoring for the Ni-doped CoFe Prussia blue precursor, we demonstrate an inverse spinel NiCoFe oxide with dominant Co2+ (NiCoII(5)Fe-ONC). Interestingly, the introduction of Ni can promote the valence modulation in depth, which suggests the superior oxygen evolution reaction (OER) performance of the well-balanced and Co2+-rich CoFe oxide. Electrochemical measurements show that NiCoII(5)Fe-ONC can afford a current density of 10 mA cm−2 at a low overpotential of only 220 mV in alkali, which is much better than that of RuO2. The robust catalytic performance results from the increased active sites, facile electron transfer and favorable adsorption/desorption of intermediate products. The synergistic effect of Ni-doping and chemical tailoring on valence configuration has been studied in detail. This work provides a potential method to develop high-efficiency electrocatalysts and expands researchers’ access to the 3d transition-metal catalysts in favor of valence engineering.

Effect of Ni-doping on the structural, magnetic, and electronic properties of La0.2Sr0.8MnO3 perovskite

Effect of Ni-doping on the structural, magnetic, and electronic properties of La0.2Sr0.8MnO3 perovskite

A systematic investigation on structural and optical properties of sol–gel spin coating fabricated CdS nanocrystalline thin films: effect of Ni doping

In the present work, we have successfully fabricated undoped and Ni-doped nanocrystalline CdS thin film on an ultrasonically cleaned glass substrate employing the sol–gel spin coating technique. The structural and spectroscopic properties of the films were investigated using XRD spectra, UV–Vis spectroscopy and photoluminescence spectra, respectively. The X-ray diffraction spectra revealed the polycrystalline nature of films with cubic structure and (111) as preferred orientation. The average crystallite size evaluated by the Debye–Scherrer formula lying in the range of 6–12 nm for the deposited films. According to UV–VIS Spectroscopy, the average transmittance of films in the visible region varies between 70–90%. The optical band gap of CdS thin film was evaluated from absorption spectra. The bandgap of the deposited films is in the range of 2.48–2.70 eV which is higher than that of bulk CdS (2.42 eV). This verifies the blue shifting in band edge of CdS nanocrystalline thin films due to the quantum confinement effect. Photoluminescence spectra of the thin film showed that the fundamental band edge emission peak centred at 485 nm also called blue band emission. It is observed that the low temperature resistivity of the films was in the range of 107–103 Ω cm and also found to decrease with increasing Ni concentration, as a result from dc two probe measurements.

Effect of Ni substitution on structural, dielectric and magnetic properties of Zn ferrite nanoparticles

Effect of Ni doping on ZnFe2O4 samples was prepared by a sol-gel auto-combustion method. The obtained samples were calcinated at 6000C. Then, the samples were characterized by powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, dielectric and magnetic properties. XRD results confirm the formation of a cubic spinel-type structure with an average crystallite size decreased with Ni concentration from 33.68 to 31 nm. Lattice parameter decreases with increasing Ni concentration, due to the small ionic radius of the Ni2+ ion. The SEM images show the morphology of the samples as spherical shaped particles in agglomeration. The dielectric constant and magnetization showed an increasing trend with increasing Ni concentration due to the rearrangement of cations at tetrahedral and octahedral sites.

Magnetic and superconducting phase diagram of Eu(Fe1−xNix)As2

We report the Ni-doping effect on magnetism and superconductivity (SC) in an Eu-containing 112-type system $\mathrm{Eu}({\mathrm{Fe}}_{1\ensuremath{-}x}{\mathrm{Ni}}_{x}){\mathrm{As}}_{2}$ ($0\ensuremath{\le}x\ensuremath{\le}0.15$) by the measurements of resistivity, magnetization, and specific heat. The undoped ${\mathrm{EuFeAs}}_{2}$ undergoes a spin-density-wave (SDW) transition at ${T}_{\mathrm{SDW}}\ensuremath{\sim}105\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ in the Fe sublattice and a magnetic ordering at ${T}_{\mathrm{m}}\ensuremath{\sim}40\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ in the Eu sublattice. Complex Eu-spin magnetism is manifested by a spin-glass reentrance at ${T}_{\mathrm{SG}}\ensuremath{\sim}15\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and an additional spin reorientation at ${T}_{\mathrm{SR}}\ensuremath{\sim}7\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. With Ni doping, the SDW order is rapidly suppressed, and SC emerges in the Ni-doping range of 0.01 $\ensuremath{\le}x\ensuremath{\le}$ 0.1 where a maximum of the superconducting transition temperature ${T}_{\mathrm{c}}^{\mathrm{max}}=17.6\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ shows up at $x=0.04$. On the other hand, ${T}_{\mathrm{m}}$ decreases very slowly, yet ${T}_{\mathrm{SG}}$ and ${T}_{\mathrm{SR}}$ hardly change with the Ni doping. The phase diagram has been established, which suggests a very weak coupling between SC and Eu spins. The complex Eu-spin magnetism is discussed in terms of the Ruderman-Kittel-Kasuya-Yosida interactions mediated by the conduction electrons from both layers of FeAs and As surrounding ${\mathrm{Eu}}^{2+}$ ions.

Structural and morphological optimization of Ni doped ZnO decorated silicon nanowires for photocatalytic degradation of methylene blue

In the current work, nickel doped zinc oxide decorated silicon nanowires (SiNWs) were elaborated and applied for photocatalytic degradation of organic dyes. Nickel doped zinc oxide (Ni-ZnO) was synthesized via a facile sol-gel process of metal acetates by varying Ni content from 0 to 5% followed by the annealing process. As-prepared Ni-ZnO was subsequently spin-coated on to silicon nanowires to get ZnO-Ni/SiNWs nanohybrids. The effect of Ni doping on structural, morphological and photocatalytic properties of ZnO-Ni/SiNWs was investigated. Fourier Transform InfraRed spectroscopy (FTIR) analysis confirms the complete removal of organic moieties from as-prepared Ni-ZnO after annealing at 300˚ C. X-ray diffraction studies proved the presence of pure phase hexagonal wurtzite structure while showing a decrease of crystalline size with the increase in Ni dopant. Further, SEM and Raman mapping confirm homogeneous distribution of Ni-ZnO on Si nanowires. Photocatalysis studies showed that Ni doping enhances slightly the photocatalytic degradation of methylene blue. Highest degradation efficiency of 97% with best kinetic rate constant value was obtained for Ni-ZnO (5%)/SiNWs with hydrogen peroxide addition. The developed structure stands as promising candidates as efficient, cost-effective and reusable photocatalytic systems for organic dye decomposition.

Effect of Ni doping on the characterization of TiO2 nanoparticles for DSSC applications

Effect of Ni doping on the characterization of TiO2 nanoparticles for DSSC applications

Ni-doping effects on the c-BN structural and electronic properties from density functional theory calculations

Cubic boron nitride (c-BN) is known for its hardness parameter and wide range of electronic applications due to its band gap value. Here we investigated the doping effect of Ni atom on the c-BN system within the framework of density functional theory calculation. Generalized gradient approximation (GGA) is utilized as the exchange-correlation energy to estimate bulk modulus and band gap parameters. Supercell structure is consists of 8-unit cells in the formation of 2 × 2 × 2, with a single Ni atom replacing either B or N atoms. We observed that the bulk modulus of the c-BN type structure is slightly decreased followed by an increase of the lattice constants with the addition of Ni atoms to either B or N atoms. The mid-gap state introduced by Ni atom is apparent in both cases which effectively reduces the band gap of the c-BN system.

Effect of Ni doping on structural, optical and magnetic characteristics of ZrO2 nanoparticles with efficient visible light driven photocatalytic activity

Pure ZrO2 and Ni-doped ZrO2 (NZ) based effective photocatalysts have been synthesized by a robust, swift, low-cost co-precipitation method. XRD and Raman analyses confirmed the tetragonal structure of all prepared nanoparticles (NPs), the successful replacement of Ni ions in the zirconia matrix and the presence of O vacancies. SEM images showed highly dispersed particles with spherical morphology. DRS spectra show an extended absorption band to the visible range and a significant reduction of the band gap energy in NZ NPs. The photoluminescence results confirmed efficient delay in the charge carrier recombination owing to the defect states. Interestingly, NZ NPs showed remarkable visible light-driven efficiency against textile dye methylene blue (MB). Meanwhile, 10% NZ NPs have presented the highest degradation efficiency of 94.1% in 120 min, which signified an efficient charge separation due to the more active site on the surface of a photocatalyst. In addition, ferromagnetic behaviour at room temperature is seen in all prepared samples. These concomitant analyses provide new insight into the dual functionality of NZ NPs in waste water treatment technologies and spintronics devices.

Investigation of the effects of Ni-doping on the structural and thermal properties of ZnAl2O4 spinels prepared by wet chemical method

Investigation of the effects of Ni-doping on the structural and thermal properties of ZnAl2O4 spinels prepared by wet chemical method

Luminescence and Stability Enhancement of CsPbBr3 Perovskite Quantum Dots through Surface Sacrificial Coating

AbstractAll‐inorganic perovskite quantum dots (QDs) have emerged as a new category of low‐cost semiconducting luminescent materials for optoelectronic applications. However, their poor stability has become the main challenge that impedes their potential applications. Herein, Ni‐doped CsPbBr3 QDs with lead phosphate (Pb3(PO4)2) shell through surface sacrificial coating (c‐Ni‐CsPbBr3) have been developed based on a modified thermal injection approach. The synergistic effect of Ni doping and Pb3(PO4)2 coating effectively improves the stability and optical performances of CsPbBr3 QDs, including photoluminescence (PL) intensity, the average lifetime, and PL quantum yield (QY). Thus, the c‐Ni‐CsPbBr3 QDs demonstrate the full width at half maxima (FWHM) and PLQY being 18.42 nm and 90.77%, respectively. The PL intensity of c‐Ni‐CsPbBr3 can be maintained at 81% of its original value after being heated at 100 °C for 1 h. No phase transformation can be observed after being stored under ambient conditions (25 °C, 60% relative humidity (RH)) for 21 days. In addition, by combining green c‐Ni‐CsPbBr3 QDs, red CdSe‐based QDs and the blue GaN chip, a QD enhancement film (QDEF) is fabricated to form a liquid crystal display (LCD) backlit with a wide color gamut covering cover 121% of the National Television System Committee (NTSC) standard.

Preparation and Characterization of Nickel-Doped Zinc Sulphide Thin Films for Solar Cell Applications

This study presents the production of pure and different amounts of Ni-doped (4, 8, 12%) ZnS films on microscope glass substrate at 4005°C substrate temperature with Ultrasonic Spray Pyrolysis Technique and the effect of Ni doping on some physical properties of pure films. X-ray diffractometer (XRD), UV-Vis spectrophotometer, two-probe method and atomic force microscope (AFM) were used to analyze the structural, optical, electrical and surface properties of all films, respectively. XRD patterns contains broad peaks showing a low crystallinity level for the films. Ni doping caused ZnS films to have high absorbance values through the visible spectrum. Optical band gap energy values of ZnS:Ni thin films were determined to be between 3.71-3.96 eV. Two-probe measurements revealed that the electrical conductivity values of ZnS films increased significantly depending on the Ni doping. AFM results showed that the films have an almost homogeneous distribution with a rough surface. No significant change was observed for the surface properties of the films due to the Ni doping. As a result of all analyzes; it was seen that Ni doping has an important effect on the optical and electrical properties of ZnS films, without modifying the crystalline structure or surface texture. Keywords: Zinc sulphide films; Nickel doping; Ultrasonic spray pyrolysis; Optical and electrical properties; XRD; AFM. DOI: 10.7176/JSTR/7-04-03