Nano NiO Research Articles

Synthesis of Bimetallic Ni-Cr Nano-Oxides as Catalysts for Methanol Oxidation in NaOH Solution.

Bimetallic Ni-Cr nano-oxide catalysts were synthesized by thermal decomposition method and were investigated as the anode electrocatalysts for the oxidation of methanol. The catalysts were characterized by X-ray diffraction and transmission electron microscopy. The electroactivity of the catalysts towards methanol oxidation in a solution containing 0.25 M NaOH and 1.0 M MeOH was examined using cyclic voltammetry and chronoamperometry. The results indicate that a mixture of rhombohedral-structured NiO and Cr2O3 nanocrystals generated at the calcination temperature of 500-700 degrees C while octahedral-structured spinel NiCr2O4 formed at higher temperature. The influence of metallic molar ratio on the electrocatalytic performance of the catalysts was studied. The Ni-Cr nano-oxides prepared at comparatively low temperature displayed significantly higher catalytic activity and durability in alkaline solution toward electrooxidation of methanol compared with the pure nano NiO. The results indicate a synergy effect between NiO and Cr2O3 enhancing the electrocatalytic properties of the bimetallic Ni-Cr nano-oxide catalysts. Meanwhile, NiCr2O4 hardly increased the activity and durability of the catalyst. In addition, the Ni-Cr catalyst also exhibited excellent stability and good reproducibility. Therefore, Ni-Cr nano-oxide catalyst may be a suitable and cheap electrocatalyst for methanol oxidation in alkaline medium.

Adsorption of heavy metal ion from aqueous solution by nickel oxide nano catalyst prepared by different methods

Environmental pollution by heavy metal is arising as the most endangering tasks to both water sources and atmosphere quality today. The treatment of heavy metals is of special concern due to their recalcitrance and persistence in the environment. To limit the spread of the heavy metals within water sources, nickel oxide nanoparticles adsorbents were synthesized and characterized with the aim of removal of one of the aggressive heavy elements, namely; lead ions. Nano nickel oxide adsorbents were prepared using NaOH and oxalic acid dissolved in ethanol as precursors. The results indicated that adsorption capacity of Pb(II) ion by NiO-org catalyst is favored than that prepared using NaOH as a precipitant. Nickel oxide nanoparticles prepared by the two methods were characterized structurally and chemically through XRD, DTA, TGA, BET and FT-IR. Affinity and efficiency sorption parameters of the solid nano NiO particles, such as; contact time, initial concentration of lead ions and the dosage of NiO nano catalyst and competitive adsorption behaviors were studied. The results showed that the first-order reaction law fit the reduction of lead ion, also showed good linear relationship with a correlation coefficient (R2) larger than 0.9.

Development of nano NiO incorporated nickel–phosphorus coatings for electrocatalytic applications

Nano NiO particles, prepared by wet chemical precipitation method using nickel nitrate as precursor, were characterized using different techniques including XRD, UV spectroscopy, HRTEM, FTIR spectroscopy and Micro Raman spectroscopy. The effects of nano NiO incorporation on enhancement of electrocatalytic efficiency of the electroless Ni–P coatings for hydrogen evolution reactions (HERs) in alkaline medium were systematically investigated in this paper with respect to both metallurgical and electrochemical characteristics. An improvement in the hardness and thickness of electroless coatings along with a mirostructural surface grain refinement was achieved by the incorporation of the nano NiO into the Ni–P matrix. The long term stability of nano NiO incorporated coatings in alkaline medium was ensured by open circuit potential (OCP) analysis. The composite incorporated coatings exhibited a substantial reduction in overpotential during HER studies in 32% NaOH medium. The role of nano NiO on enhancement of electrocatalytic efficiency of the coatings for catalytic HER is evident from the results of potentiodynamic polarization and cyclic voltammetric studies.

SYNTHESIS AND NANO STRUCTURAL STUDY ON TIO2-NIO-SIO2 COMPOSITE

We report on the synthesis, morphology, chemically and structurally of TiO2-NiO-SiO2 nanostructure. The TiO2-NiO-SiO2 nanostructure was synthesized by a method based on the sol-gel method, by the simultaneous gelation of all cations. The coatings were deposited on dried soda-lime glass slides by spin coating. Composite powders and coating on glass have been characterized by XRD, SEM, EDAX, and FTIR. X-ray diffraction showed the formation of nano crystalline, anatase, TiO, NiO and NiTiO3 phases. Scanning electron microscopy revealed that nanostructure formed by increasing the calcinations temperatures. EDX spectroscopy confirmed the composition of the ternary powders and coating, which were formed during the gelation process. The effects of chemical compositions and calcinations temperature on the surface topography and the crystallization of phases were studied. The activation energy (E) of nanoparticles formation during thermal treatment was calculated.

Production of hydrogen by steam reforming of ethanol over alumina supported nano-NiO/SiO2 catalyst

The production of hydrogen by catalytic steam reforming of ethanol was carried out over alumina supported nano NiO catalyst in silica synthesized using sol–gel method. The catalyst was characterized using SEM, TEM and BET surface area analyzer. The performance of the catalyst in ethanol reforming was investigated using three important operating parameters such as reaction temperature, feed steam to ethanol ratio and space-time. The activity tests were performed in the steam to ethanol molar ratio range of 2:1 to 9:1 and space-time from 2.78 to 9.25kgcatalysthkmol−1 of ethanol fed and in the temperature range of 550 to 700°C. A maximum yield of 4.2mol of hydrogen per mole of ethanol reacted were produced at 650°C. A favorable operating condition was established at 650°C using 8:1 steam to ethanol molar ratio and a space-time of 9.25kgcatalysthkmol−1 of ethanol fed. Under these operating conditions, ethanol conversion, product composition and H2 yield were studied to see the contributions of water–gas shift reaction, ethanol cracking, methane steam reforming and also reverse water–gas shift reaction towards the yield of hydrogen. The kinetic study was performed over a wide range of space-time at different temperatures under negligible diffusional resistance. A power-law model rate equation was derived with acquired experimental data. The kinetic parameter and order of reaction were estimated by non-linear regression method. The activation energy was calculated to be 27kJmol−1. A good agreement was obtained between experimental and model predicted results.

The Electrochemical Capacitive Behaviors of NiO Nanoparticles

The NiO nanoparticles were synthesized at different temperatures using a simple hydrothermal precipitation method and then calcined at 400°C for 2h. The morphology, crystalline structures and functional groups of nano NiO materials were investigated by SEM, XRD and FT-IR, respectively. Electrochemical properties were examined by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and cyclic charge-discharge tests. The results showed that the particle size of nano NiO was around 10nm and dependent of temperature in the range of 120-180°C. Their specific capacitance achieved to 630 F/g at the scan rate of 5mV/s (vs. Hg/HgO). The cycling test results showed that nano NiO exhibited good cycling performance after 500 cycles.

Investigation of nano NiO, supported and metal ion substituted NiO for selective hydration of aromatic nitriles to amides

Freshly prepared nano NiO, NiO supported HAP, TiO2, ZrO2 and γ-Al2O3 and metal ion substituted nickel oxide (Ni1−xMxO, M=Co, Cu and Mn) have been tested for hydration of aromatic nitriles. Mn substituted compound of nominal composition, Ni0.7Mn0.3O was found to be the highly active catalyst. The reaction was carried out in autoclave using water as a solvent and the reaction time varied between 2 and 24h for heterocyclic cyano nitriles to methyl benzonitriles.

Highly active and stable nano NiO–MgO catalyst encapsulated by silica with a core–shell structure for CO2 methanation

Ni–MgO nanoparticles (NPs) encapsulated by porous silica shell for CO2 methanation were synthesized.

Chemical-looping combustion of syngas with nano CuO–NiO on chabazite

To enhance CO2 capture, nanostructured bimetal oxide (i.e., CuO–NiO) dispersed on chabazite were used as an oxygen carrier for the chemical-looping combustion (CLC) of a syngas (CO (35%) and H2 (25%) balanced with N2). At the temperature range of 973–1173K, desired contact times (<4min) for CLC of the syngas with the CuO–NiO/chabazite oxygen carrier can be obtained. Notably, the oxygen carrier possesses a high reactivity in the 5-cycle CLC test. Mainly nano CuO and NiO on chabazite are observed by component-fitted X-ray absorption near edge structure (XANES) spectroscopy. The refined X-ray absorption fine structure (EXAFS) spectra also indicate that during CLC, bond distances of CuO and NiO in the bimetal oxide oxygen carrier are increased by 0.04 and 0.02Å, respectively, suggesting an effective oxygen transfer for the syngas combustion. About 96% of NiO on chabazite are in the nano scale, which can be reduced with the syngas to form nanosize Ni (95%) at 1073K. Notably, about 5% of oxygen are transferred from NiO to Cu, and leads to form Cu2O during CLC. The effective oxygen transport with the bimetal oxide oxygen carries during CLC gives better combustion efficiency than the individual metal oxide at the high temperature range of 973–1073K.

Production of hydrogen by steam reforming of methane over alumina supported nano-NiO/SiO2 catalyst

Steam reforming of methane (SRM) was carried out over alumina supported nano NiO catalyst in silica synthesized using sol–gel method. The crystallite size of NiO in NiO–SiO2 catalysts was found to vary with the calcination temperature and the extent of Ni loading in the catalyst. The NiO crystallite size was found to be 9–15nm in the Ni loading range of 5–15% and calcinations temperature range of 350–500°C studied. Catalyst containing 10% Ni was found to be the best one for steam reforming reaction in terms of methane conversion. The catalyst was found to be very active and stable in the temperature range of 500–700°C. The most favorable reaction condition was established at a temperature of 700°C, steam to methane molar ratio of 3.5 and a space–time of 11.31kgcath/kmol of inlet methane. At this optimum condition, the conversion of methane was 95.7% and the yield of hydrogen was about 3.8moles of hydrogen per mole of methane reacted.

Preparation for Nano-NiO by Electrolysis of Nickel in HOCH2CH2OH Solution

A method to prepare nickel oxide material which has a high purity and nano-sized particle was developed. nano NiO was synthesized by sol-gel method using nickel alkoxide as precursors. The structural characterization of the obtained materials was performed by thermal analysis TG-DTA, X-ray diffraction (XRD), Laser Raman spectra and Transmission Electron Microscopy (TEM). The characterization results indicated that NiO nano-particles (size 25–35 nm) are obtained by hydrolyzing of metal alkoxide of Ni(OCH2CH2OH)2 and possess high purity.

Synthesis and Structures Characterization of Nano NiO by PDCG Technology

Nano NiO is prepared by Parallel Dropping Concentration Gradient method(PDCG)with nickel nitrate hexahydrate,ammonia and Tween-80.The structures and morphology of Ni(OH)2•nH2O and NiO are characterized by DSC,XRD,SEM and FTIR.The results shows that because of the desorption of solvent and physical adsorbed water, the weight of precursor changes slowly during 40-280°C, while the weight of compound material changes quickly during 280-480°C because of the loss of chemical adsorbed water and the decomposition of Ni(OH)2. Above 480°C,the weight of sample changes unobviously. SEM shows that nano NiO soft gathered to form particles under the effection of surfactant. XRD shows that nano NiO prepared by PDCG was cubic crystal and with an average particle size of 3.8 nm.

Interpretation of the Ni K-edge EXAFS in nanocrystalline nickel oxide using molecular dynamics simulations

Analysis of atomic structure at the nanoscale is a challenging task, complicated by relaxation phenomena and thermal disorder. In this work, the x-ray absorption spectroscopy at the Ni K-edge was used to address this problem in nanocrystalline NiO (nano-NiO) at 300 K. The analysis of the first two coordination shells using conventional two-shell single-scattering approximation allowed us to determine the expansion of the average lattice but contraction of the Ni―O bonds in the first coordination shell in nano-NiO in comparison with the bulk nickel oxide. The EXAFS signal generated within the first six coordination shells (up to ~ 6.5 Å) was successfully interpreted using classical molecular dynamics and ab initio multiple-scattering EXAFS theory. We found that simple rigid-ion force-field model is able to describe the structure relaxation and dynamics in both bulk and nano-NiO. Such approach requires less parameters than conventional EXAFS analysis and allows accounting explicitly for thermal effects and many-atom distribution functions. Finally, we showed that the EXAFS signal is rather sensitive to small variations of the force-field model and, thus, the agreement between the experimental and calculated EXAFS signals can be used for the force-field model optimization.

Catalytic Upgrading of Biomass Fast Pyrolysis Vapors with Nano Metal Oxides: An Analytical Py-GC/MS Study

Fast pyrolysis of poplar wood followed with catalytic cracking of the pyrolysis vapors was performed using analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The catalysts applied in this study were nano MgO, CaO, TiO2, Fe2O3, NiO and ZnO. These catalysts displayed different catalytic capabilities towards the pyrolytic products. The catalysis by CaO significantly reduced the levels of phenols and anhydrosugars, and eliminated the acids, while it increased the formation of cyclopentanones, hydrocarbons and several light compounds. ZnO was a mild catalyst, as it only slightly altered the pyrolytic products. The other four catalysts all decreased the linear aldehydes dramatically, while the increased the ketones and cyclopentanones. They also reduced the anhydrosugars, except for NiO. Moreover, the catalysis by Fe2O3 resulted in the formation of various hydrocarbons. However, none of these catalysts except CaO were able to greatly reduce the acids.

Synthesis and characterization of nano‐sized NiO and its surface catalytic effect on poly(vinyl alcohol)

AbstractNickel oxide (NiO) nano particle is synthesized by Ultrasound assisted one pot method and thus synthesized nano NiO is mixed with poly(vinyl alcohol) (PVA) to prepare the PVA/NiO nanocomposite. The influence of the composition on the structural modification on the composite is evaluated. The particle size and morphology of NiO nano material is confirmed by HRTEM. The structure and properties of the PVA/NiO nanocomposite material are characterized by FTIR, XRD, UV–Visible spectroscopy, DSC, TGA, and HRTEM. The synthesized PVA nanocomposite underwent hydrolytic oxidation reaction assisted by the effect of nano‐sized NiO. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Formation of In-Situ Dispersion Strengthening Particles in Cast FeCrAl Alloy

In order to fabricate dispersion strengthened alloys strengthened by submicron-sized or nano-sized stable particles through casting routes, understanding of the formation process of dispersion strengthening particles in metal melt is of significance. Thus, nano NiO and TiO 2 particles were selected as reactant to form in-situ dispersion strengthening oxide particles in Fe20Cr5Al alloy. Nano NiO and TiO 2 particle powder was separately dispersed into nano Ni powder first. The loose mixed nano powder was added in Fe20Cr5Al alloy melt when pouring the melt into mold. The study shows that nano NiO particles were not as effective as nano TiO 2 particles in forming dispersion strengthening Al 2O 3 particles. The final diameters of dispersion strengthening oxide particles arose from nano TiO 2 particles were of submicron. The Brownian collision of particles had caused this coarsening.