Metal Oxides NiO Research Articles

Understanding solid phase diffusion-bonding process of Ni (000)/α-Al2O3 (0001) interface

The dynamic processes and characteristics of solid phase diffusion-bonding of interfacial atoms at high temperatures and the effect of that on bonding strength of Ni (111)/α-Al2O3 (0001) interface were investigated through molecular dynamics. It is shown that atomic diffusion occurs at the Ni/Al2O3 interface in the temperature range from 698 K to 1,098 K, and proceeds mainly from the Ni side to the Al2O3 side. The interface was previously reconstructed by solid bonding below the melting temperature, leading to the amorphization of the interface. Besides, the intermetallic complexes such as AlmNin (e.g., AlNi3), metal oxide NiO and Ni-Al-O bonds were formed gradually during the diffusion process of atoms. The formation mechanisms of the Ni-Al, Ni-O, and Ni-Al-O bonds are revealed. Based on the reconstructed structure, the adhesion effort at the interface is compared. The higher the temperature, the larger the bond number and the higher the interfacial bonding strength.

Performance study of proton conducting electrolytes based on BaZr1−xYxO3-δ for solid oxide electrolysis cell

For the purpose of realizing the high-performance BaZr1−xYxO3-δ (BZY) proton electrolyte materials for solid oxide electrolysis cell (SOEC), the influence of different contents of the transition metal oxide NiO on the performance of proton electrolyte BZY was studied. Specifically, BZY-x mol. % NiO (x = 0, 0.5, 1, 2 and 3, named as BZY, BZY+0.5NiO, BZY+1NiO, BZY+2NiO and BZY+3NiO, respectively) composite electrolyte materials were prepared, as well as and their crystal structure, morphology and electrochemical properties were characterized. The results demonstrate that the composite NiO contributes to the effective improvement of the density of BZY prepared at 1400 ℃, significantly improving the proton conductivity of BZY, and facilitating the performance of BZY-based SOECs. Among them, 2 mol. % NiO-BZY has the optimal performance, the highest density, and the lowest electrochemical impedance. The SOEC based on BZY+ 2NiO electrolyte possesses the most satisfying electrochemical performance, indicating the optimum content of 2 mol. % NiO in this case.

Performance of BaCe0.8Y0.2O3-δ Proton Electrolyte Materials for Solid Oxide Fuel Cells by Compositing the Transition Metal Oxide NiO

Since the conduction activation energy of a proton is low, proton-conducting solid oxide fuel cells (H-SOFCs) can work at low temperatures (around 600 °C), which is conductive to maintaining the long-term stability of SOFCs. Proton conductor BaCe1-xYxO3-δ is the most commonly used electrolyte material for H-SOFCs, which directly affects the performance of SOFCs. For the purpose of realizing the high-performance BaCe0.8Y0.2O3-δ (BCY) proton electrolyte materials for SOFC, the effect of different contents of the transition metal oxide NiO on the performance of proton electrolyte BCY was studied. Specifically, BCY-x mol% NiO (named BCY, BCY + 0.5NiO, BCY + 1NiO, BCY + 2NiO, and BCY + 3NiO, when x = 0, 0.5, 1, 2, and 3, respectively) composite electrolyte materials were prepared, and their crystal structures, morphologies, and electrochemical properties were explored. The results showed that NiO could effectively improve the density of BCY prepared at 1400 °C and enhance the proton conductivity of BCY and the performance of BCY-based SOFCs. Among them, the BCY + 2NiO electrolyte had good density and the highest proton conductivity, and the SOFC based on the BCY + 2NiO electrolyte had the best electrochemical performance, indicating that the optimal content of the NiO additive was 2 mol% in this case. The results reported in this work are conductive to the realization of high-performance proton electrolyte materials for the SOFC.

Routes to increase performance for antimony selenide solar cells using inorganic hole transport layers

Simple compound antimony selenide (Sb2Se3) is a promising emergent light absorber for photovoltaic applications benefiting from its outstanding photoelectric properties. Antimony selenide thin film solar cells however, are limited by low open circuit voltage due to carrier recombination at the metallic back contact interface. In this work, solar cell capacitance simulator (SCAPS) is used to interpret the effect of hole transport layers (HTL), i.e., transition metal oxides NiO and MoO x thin films on Sb2Se3 device characteristics. This reveals the critical role of NiO and MoO x in altering the energy band alignment and increasing device performance by the introduction of a high energy barrier to electrons at the rear absorber/metal interface. Close-space sublimation (CSS) and thermal evaporation (TE) techniques are applied to deposit Sb2Se3 layers in both substrate and superstrate thin film solar cells with NiO and MoO x HTLs incorporated into the device structure. The effect of the HTLs on Sb2Se3 crystallinity and solar cell performance is comprehensively studied. In superstrate device configuration, CSS-based Sb2Se3 solar cells with NiO HTL showed average improvements in open circuit voltage, short circuit current density and power conversion efficiency of 12%, 41%, and 42%, respectively, over the standard devices. Similarly, using a NiO HTL in TE-based Sb2Se3 devices improved open circuit voltage, short circuit current density and power conversion efficiency by 39%, 68%, and 92%, respectively.

Highly efficient and simultaneous catalytic reduction of multiple toxic dyes and nitrophenols waste water using highly active bimetallic PdO\u2013NiO nanocomposite

Azo dyes and nitrophenols have been widely used in the various industry which are highly toxic and affecting the photosynthetic cycle of aquatic organism. The industry disposals increase the accumulation of azo compounds in the environment. In the present study, we synthesized the low cost, PdO-doped NiO hetero-mixture via simple hydrothermal combined calcination process. The morphology results proved that, the spherical PdO nanoparticles are evenly doped with NiO nanoparticles. The band gap values of metal oxides NiO, PdO and PdO–NiO composite were found to be 4.05 eV, 3.84 eV and 4.24 eV, respectively. The high optical bandgap (Eg) value for composite suggests that the PdO interface and NiO interface are closely combined in the composite. The catalytic activity of the PdO–NiO was analyzed for the reduction of different toxic azo compounds namely, 4-nitrophenol (NP), 2,4-dinitrophenol (DNP), 2,4,6-trinitrophenol (TNP), methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) separately and their mixture with the presence of a NaBH4. For the first time, the large volume of the toxic azo compounds was reduced into non-toxic compounds with high reduction rate. The proposed PdO–NiO catalyst exhibit excellent rate constant 0.1667, 0.0997, 0.0686 min−1 for NP, DNP and TNT and 0.099, 0.0416 and 0.0896 min−1 for MB, RhB and MO dyes respectively which is higher rate constant than the previously reported catalysts. Mainly, PdO–NiO completes the reduction of mixture of azo compounds within 8 min. Further, PdO–NiO exhibit stable reduction rate of azo compounds over five cycles with no significant loss. Hence, the proposed low cost and high efficient PdO–NiO catalyst could be the promising catalyst for degradation of azo compounds.

Study of Pb(II) removal ZIF@NiTiO3 nanocomposite from aqueous solutions

Zeolitic imidazolate frameworks (ZIFs) are a subclass of metal-organic frameworks (MOFs). In this work, the nickel titanate (NiTiO3) nanoparticles and ZIF based nickel titanate (ZIF@NiTiO3) were prepared by sol-gel method and were characterized by powder X-Ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), Scanning Electron Microscopy (SEM) and BET(Brunauer-Emmett-Teller) methods. The NiTiO3 had rhombohedral crystal structure and crystallite size of 40−50 nm. FTIR confirmed of composite and metal-oxide NiO and TiO bands. BET analysis showed ZIF@NiTiO3 nanocomposite had higher surface area (345 m2 g−1) than NiTiO3 (31 m2 g−1). The adsorption studies of Pb(II) by NiTiO3 and ZIF@NiTiO3 nanocomposite were carried out by batch method. The effects of varying parameters like contact time; pH and mass of sorbent on Pb(II) were investigated. The ZIF@NiTiO3 was found to follow by pseudo second order kinetic model better than the pseudo-first order (k2 = 1.3 × 10 -2), since the adsorption isotherm experimental data was fitted better by Langmuir model than Freundlich and Temkin models. The maximum adsorption capacity of Pb(II) for NiTiO3 and ZIF@NiTiO3 was observed 72 and 155 mg g−1, respectively at pH 5. ZIF@NiTiO3 acts as sufficient reusable sorbent for Pb(II).

Pyrochlore doped Pr2Sn2O7 ceramics: Electronic transport properties and high NO2 sensitivity

This work proposed pyrochlore doped-Pr2Sn2O7 ceramics with electronic transport and NO2 sensitivity through molecular insights into sensing mechanism by DFT. NO2 adsorbed on the p-type semiconductor metal oxide NiO(100) can be decomposed into three stable adsorbed states NO2, NO and O that will obtain electrons from the NiO valence band to form N2 (or N2O) and O2−, resulting in an increase of the holes concentration. The results suggest that the response current value of the sensor based on Pr2Sn2O7 doped by Ca2+ at A site is 53.5 times higher than that of commercial YSZ, indicating high sensitivity with 420 nA/ ppm at mild temperature 550 °C. Besides the creation of oxygen-defect sites, the electronic transport is responsible for the improved sensing properties. The electrons on doped Pr2Sn2O7 ceramics can complement the hole-accumulation layer and make NO2, NO, O accept electrons quickly to accelerate the rate of the electrochemical cyclic reaction.

Electrical and magnetic properties of NiTiO3 nanoparticles synthesized by the sol-gel synthesis method and microwave sintering

The microwave sintered NiTiO3 nanoparticles were synthesized by sol-gel method. The synthesized compound is found to be rhombohedral crystal structure and crystallite size of 46 nm from X-ray powder diffraction technique. The metal-oxide Ni-O and Ti-O bands were analyzed by Fourier Transform Infra-Red analysis. The average particle size is found to be 56 nm from High Resolution Scanning Electron Microscope analysis. The activation energy calculated from Arrhenius plot, the value is found to be 0.04 μeV. The Mr value is found to be 0.22 emu/g. At room temperature NiTiO3 exhibited superparamagnetic nature.

Hierarchical NiCo2O4 Micro-/Nanostructures with Tunable Morphologies As Anode Materials for Li-Ion and Na-Ion Batteries

Binary metal oxide NiCo2O4 is a promising anode material for future Li-ion batteries (LIBs) and Na-ion batteries (SIBs) owing to its inherited characteristics of high theoretical capacity and low cost.1,2 In particular, NiCo2O4 possesses high electrical conductivity, reversible capacity and mechanical stability than single-component metal oxides NiO and Co3O4. 3,4 However, the large volume change and sluggish kinetics during the charge/discharge process result in a short cycling life and poor rate performance, which limits its practical application.5 The electrochemical performance of an active material highly depends on its structure (both primary and secondary structures).6 Therefore, tailored architecture design and surface engineering of NiCo2O4 are highly desirable to secure both the high transport kinetics and sustain the structure integrity for high rate and long life. In this study, one-dimensional (1D) porous NiCo2O4 microrods and microspheres are successfully synthesized by a simple solvothermal method using different solvents followed by calcination. The solvothermal process and solvents employed in the synthesis play crucial role in determining the final morphologies of NiCo2O4. Compared with NiCo2O4 microspheres, the porous microrods exhibit much better Li- and Na-ion storage properties owing to the 1D geometry to facilitate fast ion transport and the porous structure to accommodate volume expansion of NiCo2O4 during ion insertion. The porous NiCo2O4 microrods display high initial charge capacity (1046.1 mAh g-1 at 100 mA g-1), long cycling stability (719 mAh g-1 after 600 cycles at 500 mA g-1), and rate capability for lithium-ion batteries. They also show better performance in sodium-ion batteries. This work may provide a facile way for fabricating novel structured metal oxide anode materials for batteries. Figure 1. (Left) SEM images of the 1D porous NiCo2O4 microrods and microspheres for LIBs and SIBs respectively. (Right) Rate performances at various current densities of LIBs and SIBs. References Zheng, F. C.; Zhu, D. Q.; Chen, Q. W. ACS Applied Materials & Interfaces 2014, 6, (12), 9256-9264.Lee, Y.; Kim, M. G.; Cho, J. Nano letters 2008, 8, (3), 957-961.Li, B.; Feng, J.; Qian, Y.; Xiong, S. Journal of Materials Chemistry A 2015, 3, (19), 10336-10344.Jadhav, H. S.; Kalubarme, R. S.; Park, C. N.; Kim, J.; Park, C. J. Nanoscale 2014, 6, (17), 10071-10076.Chen, J.; Ru, Q.; Mo, Y.; Hu, S. RSC Advances 2015, 5, (90), 73783-73792.Ye, J.; Liu, W.; Cai, J.; Chen, S.; Zhao, X.; Zhou, H.; Qi, L. Journal of the American Chemical Society 2010, 133, (4), 933-940. Figure 1

Application of Oxide Copper Chromium Catalysts for the Purification of Exhaust Gases

Results of the development of multicomponent oxide catalysts based on Ni, Cu, and Cr supported on 2 % Ce/?-Al2O3 by varying the concentration of the active phase of catalyst are presented in paper. It was found that the highest degree of toluene conversion (up to 98.8 %) is observed on the three- component Ni-Cu-Cr/2% Ce/?-Al2O3 catalyst with optimal metal ratio Ni : Cu : Cr = 1.0 : 3.0 : 0.1 at GHSV = 5×103 h-1 and a temperature of 723 - 773 K. The presence of CeO2 crystals, X-ray amorphous clusters (d = 20 – 100 A) of variable valence metal oxides NiO and CuO as well as solid metal solutions CuO (NiO) was detected on the surface of optimum catalyst calcined at 873 K using XRD and electron microscopy methods.

Spectrum for nonmagnetic mott insulators from power functional within reduced density matrix functional theory.

We demonstrate that reduced density matrix functional theory (RDMFT), in conjunction with the power functional, can successfully treat the nonmagnetic insulating state of the transition metal oxides NiO and MnO, finding for both a gapped single particle spectrum. While long-range spin order is thus not necessary for qualitative agreement with experiment, we find that it is required for good agreement with the X-ray photoemission spectroscopy and Bremsstrahlung isochromat spectroscopy data. We further examine the nature of the natural orbitals in the materials, finding that they display significant Hubbard localization and are, as a consequence, very far from the corresponding Kohn-Sham orbitals. This contrasts with the case of the band insulator Si, in which the Kohn-Sham orbitals are found to be very close to the RDMFT natural orbitals.

Gold nanoparticles on metal oxide surfaces derived from n-alkanethiolate-stabilized gold nanoparticles; investigations of the adsorption mechanism and sulfate formation during subsequent thermolysis

n-Alkanethiolate-stabilized gold (n-CnSAu) nanoparticles (n=6, 12, 16) have been studied as the source of gold nanoparticles supported on the metal oxides NiO, TiO2 (anatase and rutile), CeO2, and γ-Al2O3 following adsorption from n-hexane and thermolysis in air at 340°C. Adsorption times increase with an increase in length of the carbon chain and vary with the metal oxide, particularly with specific surface area. Evidence of oxidation of some of the thiolate sulfur to give sulfoxide- and sulfone-type species has been established. TG/DTA studies and FT-IR (attenuated total reflectance) spectroscopy show that the adsorbed n-CnSAu nanoparticles thermally decompose at about 210–340°C depending on the metal oxide, with some decomposition products, particularly those containing sulfur, adsorbing onto the metal oxide surface. Following thermolysis at 340°C, XPS and the FT-IR studies, combined with laser-ablation mass spectrometry, show that all organic material decomposition products are generally lost, and that the residual sulfur exists as sulfate at about 0.2wt% or lower. TEM/STEM studies have shown that the n-CnSAu nanoparticles, originally about 2nm in diameter, produce gold nanoparticles with a range of 2–4nm in size on the oxide surface following thermolysis at 340°C. The final average size of the gold nanoparticles depends on the metal oxide. For NiO, HRSTEM images shows little evidence of preferred orientation following immediate adsorption of n-C6SAu nanoparticles, indicating weak interaction with the oxide surface, while a preferred orientation occurs on thermolysis at 340°C, indicating a much stronger interaction. The total oxidation of a representative alkane, isobutane, over TiO2 (both anatase and rutile) and NiO, together with the addition of 5wt% Au nanoparticles has been studied. Anatase and rutile are initially inactive but addition of the gold nanoparticles generates active oxidation catalysts, with anatase slightly more active than rutile. For NiO and 5wt% Au/NiO reaction begins at 205–215°C and complete oxidation occurs by 430–440°C. The presence of the gold nanoparticles reduces the apparent activation energy from 89 to 51kJ/mol. All active catalysts show formation of CO as well as CO2 at about 20% conversion of isobutane, but at 100% oxidation the main product is almost exclusively CO2 (>99.0%). The presence of the sulfate from the decomposition of the n-CnS− ligands has minimal apparent poisoning effect on the oxidation of isobutane for anatase, rutile, or NiO.

Study of structuring of surface-modified technical-grade carbon particles with metal oxides in oligo(divinyl-isoprene)

Effect of a nanosize coating of technical-grade carbon particles with metal oxides NiO, CuO, PbO, and Bi2O3 on processes in which continuous carbon structures are formed in an oligomer formulation was studied. The elastic and dissipative constituents of rheological properties of the 3D carbon structures being formed were determined. An optical method and computerized data processing yielded data on structuring of a filled oligomer system under various testing conditions.

Thermal behavior of Co(II) and Ni(II) hydroxycarboxylate complexes obtained by two original synthesis methods

This paper presents a facile and rapid synthesis route of metallic Ni and Co nanocrystallites at ~150 °C in the mixture composed of the corresponding metal nitrates and 1,3-propanediol, as reducing agent. The metal oxides NiO, CoO, Co3O4 nanocrystallites were, also, successfully synthesized by thermal decomposition at 300 °C of the hydroxycarboxylate coordination products, obtained in the redox reaction between 1,3-propanediol and Ni(II) and Co(II) nitrates. The formation of the Ni(II) and Co(II) hydroxycarboxylate complexes depends on the diol which generates the carboxylate anion, the transition metal and the process parameters. Ni(II) and Co(II) nanocomposites were also synthesized by thermal decomposition of the complex combinations formed within the pores of the hybrid silica gels. One of the purposes of the present study was to investigate the phase constitution of the composites obtained in similar synthesis conditions, from Ni(II) and Co(II) complex combinations embedded in silica gels. These gels were submitted to various thermal treatments and the changes occurring during these treatments were described by X-ray diffraction. Thermal analysis is an excellent tool for the study of the processes implied in the formation and decomposition of the Co(II) and Ni(II) carboxylate complexes. X-ray diffraction evidenced the nanometer sized metal and/or metal oxide phases.

Characterization of Pt Catalysts for PEM Fuel Cells

Carbon-supported platinum (Pt\\C) was combined with Ru metal or the transition metal oxide NiO, or both NiO and Co3O4 to obtain binary and ternary catalyst mixtures respectively. The electrochemical performance of these electrocatalysts for the hydrogen oxidation reaction was investigated using cyclic voltammetry in an in-house three electrode half cell. The physical characterization of the electrode catalysts was analyzed by scanning electron microscopy, energy dispersive X-ray analysis and Brunner-Emmet-Teller adsorption analysis. It was found that it did not matter if NiO was used on its own as an additive or in conjunction with Co3O4 in a mixture; the electrical activity improved notably when compared to pure Pt or Pt (40%)\\C used in the absence of NiO. The overall metal loading was 0.3 mg.cm−2 for both.

Surface structure and bonding in the strongly correlated metal oxides NiO and UO2

We show atomic resolution elevated temperature scanning tunneling microscope images of the NiO (001) and UO2 (111) surfaces. When imaging the empty states structure of NiO, a fourfold symmetric hole state is observed around defects and step edges which influences the second nearest neighbor Ni ions. A similar effect is not observed on the UO2 (111) surface. We explain this difference in terms of the degree of covalent coupling that is involved in the bonding of these oxides. Modeling of the electronic structure through the local spin density approximation incorporating the Hubbard U is used to create charge density maps which show that there is a significant element of nonsphericity of charge distribution around the Ni ions in NiO, but that the distribution is spherical in UO2.