Activities of δ-Al2O3-supported bimetallic Pt?NiO and Co?NiO catalysts for methane autoreforming: Oxidation studies

The methane oxidation activities of Pt−NiO and Co−NiO bimetallic catalysts have been investigated as part of a larger research program on the autothermal reforming of methane (combined methane oxidation and steam reforming) in a fluidized bed reactor. Experiments at atmospheric pressure and 783–1023 K for both catalysts showed that the reaction was more selective towards H₂ production at CH₄∶O₂ ratios greater than unity. Light-off temperature increased with decreasing CH₄∶O₂ ratios, but increase in gas velocity (beyond minimum fluidization) increased the light-off temperature. Co−NiO was as promising as the more expensive Pt−NiO catalyst for the oxidation.     

Characterization of the active phase of NiMo/Al2O3 hydrodesulfurization catalysts

The active phase of the NiMo/Al₂O₃ catalyst for hydrodesulfurization reactions has been investigated in this work. Special attention has been focused on the effect of the order of metal impregnation on the formation of the active phase in the reaction. The Mo and Ni oxides and their sulfides on the alumina were investigated by XPS and DRS analyses. The Ni-Mo oxides or precursor of the active phase which are chemically bonded between Mo and Ni were also confirmed from the binding energy shifts of the XPS peaks. The amount of Ni-Mo oxides was determined after the formation of metal oxides during calcination. The Ni-Mo sulfide (active phase) was then induced through sulfidation. It was important that Mo should be located at the tetrahedral sites on the alumina with a high Mo dispersion. These results indicated that there are two important factors in preparing highly efficient Ni-Mo catalysts; one is that Mo should be located at the tetrahedral coordination on Al₂O₃ in high dispersion (Mo/Al₂O₃) and the other is that the Ni species should be supported on MoAl₂O₄ to form Ni-Mo oxides which change into the Ni-Mo sulfide active sites by sulfidation.     

Nanostructured NiO based all solid state electrochromic device

A nickel oxide film with a thickness of 445 nm was deposited from nickel acetate precursor using the sol–gel dip coating method. The NiO films exhibit optical transmission of 84% at 550 nm and direct energy gap (E _gd) value is 3.64 eV. The FTIR spectrum of the films confirms the formation of Ni–O bond. XRD spectrum reveals the formation of nano crystallites along (111) and (200) planes with a particle size of 17 nm. The electrochromic properties have been studied using cyclic voltammetric (CV) technique. The optical transmission of a glass/FTO/NiO/ZrO₂/FTO/glass EC device is reported.     

Dependence of NO<Subscript>2</Subscript> sensitivity on thickness of oxide-sensing electrodes for mixed-potential-type sensor using stabilized zirconia

The effect of thickness of oxide-sensing electrode (SE) on NO₂ sensitivity of the planar sensor based on yttria-stabilized zirconia (YSZ) was examined at high temperatures. The sensitivity of the sensor increased with decreasing thickness of SE, and the highest sensitivity was obtained by using the thinnest layer of Cr₂O₃–SE (2.7 μm) at 700 °C. In the case of NiO–SE, the highest sensitivity was observed for the sensor using the 4 μm-thick SE even at high temperature of 850 °C. Based on the results of the measurements for the complex impedances, the polarization curves, and the gas-phase NO₂ decomposition catalysis, it was confirmed that the catalytic activity to the gas-phase NO₂ decomposition on the oxide–SE matrix played an important role in determining the NO₂ sensitivity of the present sensors. This artice was accidentally published twice. This is the second publication, please cite only the authoritative first one which is available at . An additional erratum is available at . An erratum to this article can be found at     

镍基气凝胶催化CH_4-CO_2重整制取合成气反应的研究 Ⅰ.制备方法对NiO-CeO_2-Al_2O_3催化剂物化性质的影响

采用浸渍法、溶胶 凝胶过程与普通干燥、超临界干燥过程相结合的方法制备了具有不同结构特点的NiO CeO2 Al2 O3催化剂 ,分别为浸渍型催化剂 (iNCA)、干凝胶催化剂 (xNCA)和气凝胶催化剂 (aNCA) ,利用BET、TEM、XRD、TPR、NH3 TPD、H2 TPD等方法对各催化剂样品的物化性质进行了考察。研究结果表明 ,经 82 3K焙烧后 ,镍含量为 9%的各催化剂样品中镍物种均分散良好 ;与iNCA相比 ,以溶胶 凝胶法为基础制备的xNCA和aNCA中镍物种与载体的相互作用强并且存在状态均一 ;三种催化剂中 ,气凝胶样品具有比表面积高、堆密度低、表面酸中心数多及表面镍分散度高的特点。     

纳米氧化镍的固相合成

纳米氧化镍的固相合成;NiO;纳米粒子;固相反应;合成机理     

High‐performance gas‐sensing properties of octahedral NiO crystals prepared via one‐step controllable synthesis route

Octahedrally shaped NiO powders have been synthesized via a one‐step composite‐hydroxide‐mediated method without any surfactant. The synthesized materials are characterized by XRD, EDS, TEM and FESEM techniques. Each particle exhibited a nearly perfect octahedron shape with sharp edges and corners as well as smooth surfaces. The octahedral NiO particles performed better gas‐sensitivity toward ethanol than that of NiO nanopowders, which was attributed to the exposed ｛111｝ facets of octahedron. The result was confirmed by the first‐principle calculation which indicated that the (111) facet was more active than (100) and (110) facet.     

Optical and electrochemical properties of Cu-doped NiO films prepared by electrochemical deposition

Cu-doped nickel oxide (NiO) thin films were prepared by electrochemial deposition (cathodic deposition) technique onto the fluorine doped tin oxide (F: SnO₂; FTO) coated glass substrates from organic solutions. Effects of Cu content on the morphology, structure, optical and electrochromic properties of NiO films were investigated by means of scanning electron microscope (SEM), X-ray diffraction (XRD), ultraviolet-visible spectrophotometer (UV-vis) and cyclic voltammetry (CV), respectively. SEM images indicated the formation of nanorods after Cu was added. The films were formed with amorphous or short-range ordered NiO grains and a trace of face-centered cubic Ni_xCu_1−xO confirmed by XRD. The transmittances of both bleached state and colored state were significantly lowered when Cu was added. The NiO films doped with Cu (the molar ratio was 1/8) exhibited the optimum electrochromic behavior with a variation of transmittance (ΔT) up to ∼80% at the wavelength range of 350-600 nm. Cu doping reduces the response time for both the coloring and bleaching states, and the reversibility of the redox reaction was increased as well.     

Nanoporous nickel oxide thin films and its improved electrochromic performance: Effect of thickness

Electrochromic properties of chemically bath deposited nanoporous NiO thin films were investigated as a function of film thickness using Ni sulphate precursor, aqueous ammonia and potassium persulphate as complexing and oxidizing agents respectively. The films were characterized for their structural, morphological, optical and electrochromic properties using X-ray diffraction, scanning electron microscopy, FT-IR spectroscopy, cyclic voltammetry, chronoamperometry and optical transmittance studies. X-ray diffraction patterns show that the films are polycrystalline, consisting of NiO cubic phase. Infrared spectroscopy results show the presence of free hydroxyl ion and water in NiO thin films. SEM micrographs revealed nanoporous nature composed of interconnected nanoporous network, forming well defined 3D nano envelopes. The optical band gap energy was found to be decreased from 3.22 to 2.80 eV with increasing film thickness. The electrochromic properties of all the films were investigated in aqueous (KOH) and non aqueous (LiClO₄-PC) electrolyte by means of cyclic voltammetry (CV), chronocoulometry (CC) and optical studies. The transmittance modulations or optical density differences during the coloring/bleaching process were found to be increased with the film thickness. This increment in optical differences led to an increase in coloration efficiency (CE) to about 95 cm²/C, which is two times more than that observed in KOH and response time of 2.9 s for bleaching (reduction) and 3.5 s for coloration (oxidation) observed for the film deposited at 60 min with excellent electrochemical stability up to 3000 c/b cycles in LiClO₄-PC electrolyte.