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排序方式: 共有4182条查询结果,搜索用时 15 毫秒
41.
Jana Mikulova Francois Gérard Danielle Mesnard Charles Kappenstein Daniel Duprez 《Journal of solid state chemistry》2006,179(8):2511-2520
CeO2 doped with praseodymium, neodymium and/or zirconium atoms were prepared by coprecipitation and by the sol-gel method. Structural properties were investigated by in situ XRD and Raman spectroscopy while oxygen storage capacity (OSC) was measured by transient CO oxidation. All the compounds, except pure Nd2O3, have a fluorite-type structure as well as a Raman band at 560 cm−1 characteristic of the oxygen vacancies involving non-stoichiometric oxides. The lattice parameter under hydrogen, being dependent on the temperature, revealed two reduction mechanisms: one at a low temperature at the surface and another at a high temperature in the bulk. Ce-Nd binary oxides show a strong tendency towards crystallite aggregation, which reduces accessibility to gases and OSC properties. Zirconium improves the thermal resistance to sintering of both Ce-Nd and Ce-Pr oxides. The Zr-Ce-Pr-O followed by Zr-Ce-Nd-O compounds displaying high oxygen mobility at a low temperature, appear to be very promising for practical applications such as OSC materials. 相似文献
42.
Laura León-Reina 《Journal of solid state chemistry》2007,180(4):1250-1258
La9.75□0.25(Ge6O24)O2.62 oxy-apatite shows a phase transition from triclinic to hexagonal symmetry at approximately 1020 K that has been characterised by high-temperature synchrotron X-ray and neutron powder diffraction, and ionic conductivity measurements. The crystal structure at 1073 K has been determined from joint Rietveld refinements of synchrotron X-ray and neutron powder diffraction data. The study shows that hexagonal-La9.75□0.25(Ge6O24)O2.62 contains interstitial oxygen at the position previously reported for other oxy-germanates. Changes in the oxide conductivity associated with this structural transition are discussed. The thermal analyses showed a weight loss on heating close to 600 K very likely due to water release. The synchrotron thermodiffractometric study shows an anomaly in the cell parameters evolution at that temperature, which indicates that this residual water is located into the apatite channels. The electrical characterisation under different atmospheres (dry and wet synthetic air) indicates that there is a significant proton contribution to the overall conductivity below 600 K, mainly under wet atmosphere. 相似文献
43.
《中国化学快报》2020,31(5):1207-1212
Developing high efficiency and low cost electrocatalysts is critical for the enhancement of oxygen reduction reaction (ORR), which is the fundamental for the development and commercialization of renewable energy conversion technology. Herein, zinc-nitrogen-carbon (Zn-N-C) was prepared by using biomass resource chitosan via a facile carbon bath method. The obtained Zn-N-C delivered a high specific surface area (794.7 cm2/g) together with pore volume (0.49 cm3/g). During the electrochemical evaluation of oxygen reduction reaction (ORR), Zn-N-C displayed high activity for ORR with an onset potential E0 = 0.96 VRHE and a half wave potential E1/2 = 0.86 VRHE, which were more positive than those of the commercial 20 wt% Pt/C benchmark catalyst (E0 = 0.96 VRHE and E1/2 = 0.81 VRHE). In addition, the Zn-N-C catalyst also had a better stability and methanol tolerance than those of the Pt/C catalyst. 相似文献
44.
《Electroanalysis》2003,15(21):1713-1718
The effect of oxygen on the mediated electrocatalytic oxidation of nicotinamide adenine dinucleotide (NADH) by diaphorase from Clostridium kluveri (DI) was studied using cyclic voltammetry, UV‐vis spectrophotometry and NMR spectrometry. The enzyme was found to be able to use molecular oxygen as an electron acceptor. NADH could therefore be oxidized by two competitive electron acceptors: a redox mediator, for istance p‐methylamino‐phenolsulfate (MAP) or ferrocene monocarboxylic acid (FMCA) properly added to the solution, and molecular oxygen. Some considerations on the consequence of the use of diaphorase from Clostridium kluveri in amperometric biosensors were also reported. 相似文献
45.
46.
As bio‐inspired chemical model of the oxygen‐evolving complex (OEC) in photosystem II, a new tyrosine‐modified corrole ligand 3 and its high‐valent copper and manganese complexes 3a and 3b were synthesized and characterized. The copper complexes 1a and 2a of corrole 1 and 2 were also prepared for comparison. The emission property indicates that the emission of ligands 2 and 3 is located at 670 nm, but no emission is observed for their metal complexes due to its suppression by the metal center. The electrochemical study shows that 3a might dimerize at the first two reversible oxidations, a behavior which was not observed in the case of 1a and 2a . The corrolato manganese(IV) complex 3b shows one reversible reduction and one quasireversible oxidation at ?0.17 and 0.77 V vs. Ag/Ag+, respectively. 相似文献
47.
应用改进了的旋转全电极上的电势阶跃计时库仑法,分别测定了不同电极电势下氧还原过程中电极吸附中间物和溶解中间物氧化所需的电量,实验证明,在此过程中电极上确有吸附中间物存在,而且是电极电势的函数,但其分子属性尚需进一步鉴别。 相似文献
48.
49.
LaxBa1—xCoO3系导电陶瓷导电性研究 总被引:1,自引:1,他引:1
对LaxBa1-xCoO导电陶瓷的导电性及其导电机制进行了研究,在x=0.5mol处,导电陶瓷具有金属态导是性,在La0.5Ba0.5CoO3陶瓷中,存在着氧缺位和导电电子,并且此种导电陶瓷具有较高的电子和氧离子混合导电特性。 相似文献
50.
A novel series of the formula NdSrNi1−xCuxO4−δ were synthesized for various values of x ranging from 0 to 1 in 1 atm of O2 gas flow using conventional solid-state methods and were characterized by powder X-ray diffraction and electrical resistivity measurements. The compounds have been shown to adopt the K2NiF4-type structure. The oxygen stoichiometry of the compounds was determined from thermo-gravimetric analysis (TGA). An analysis of the micro-structure of the neodymium strontium nickel copper oxide is described. All the samples were semi-conducting from room temperature down to 77 K. The effect of Cu2+ incorporation on the structural and electrical properties of NdSrNi1−xCuxO4−δ, 0?x?1, are discussed in terms of Jahn-Teller distortion of the (Ni/Cu)O6 octahedra and mixed valence character of copper. 相似文献