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1.
The development of smart structured cathode materials for supercapacitors (SCs) has sparked tremendous interest. However, the appropriate design to achieve high capacitance and energy density-based cathode materials remains a major problem for energy storage systems. This article describes the effective synthesis of self-supported 3D micro-flowers composed of ultrathin nanowires array of Co3O4 on Ni foam (NF) using hydrothermal conditions (Co3O4@NF). The mesoporous Co3O4@NF with a high surface area, providing a rich active state for the Faraday redox reaction and increasing the diffusion rate of the electrolyte ions. The optimized Co3O4@NF-16h electrode exhibited supreme electrochemical performance by delivering a high specific capacitance of 1878, (1127) and 1200 (720 C g−1) F g−1 at 1.0 and 20 A g−1, respectively. The Co3O4@NF electrode retained good capacitance stability of 91% over 10000 cycles at 20 A g−1 with excellent rate-performance of 67% at 20 folded high current values. The obtained results for the Co3O4@NF electrode are presented the enhanced pseudocapacitive performance, indicating the substantial potential for high-performance supercapacitor applications. 相似文献
2.
To improve the cycle performance of spinel LiMn2O4 as the cathode of 4-V-class lithium secondary batteries, spinel phases LiM
x
Mn2 − x
O4 (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe0.05M
y
Mn1.95 − y
O4 (M=Li, Al, Ni, Co; y = 0.05, 0.1) were successfully prepared using the sol–gel method. The spinel materials were characterized by powder X-ray
diffraction (XRD), elemental analysis, and scanning electron microscopy. All the samples exhibited a pure cubic spinel structure
without any impurities in the XRD patterns. Electrochemical studies were carried out using the Li|LiM
x
Mn2 − x
O4 (M=Li, Fe, Co; x = 0, 0.05, 0.1, 0.15) and LiFe0.05M
y
Mn1.95 − y
O4 (M=Li, Al, Ni, Co; y = 0.05, 0.1) cells. These cathodes were more tolerant to repeated lithium extraction and insertion than a standard LiMn2O4 spinel electrode in spite of a small reduction in the initial capacity. The improvement in cycling performance is attributed
to the stabilization in the spinel structure by the doped metal cations. 相似文献
3.
In this wok, a uniform layer of La2O3 is coated on the surface of LiNi0.91Co0.06Mn0.03O2 Ni-rich cathode material by using a wet coating process. The XPS and EDX analysis confirms the presence of La2O3 coating on the surface of NCM. The coated samples deliver the superior electrochemical performance, 0.2 wt % La2O3 (LaO-0.2) NCM exhibits discharge capacity of 202.7 mAh g−1 in 1st cycle and delivered the cycle stability of 87.2% after 100 cycles. Besides, the enhanced capacity retention, LaO-0.2 has delivered very high discharge capacity of 80.3 mAh g−1 at very high C-rate of 5C while the pristine sample shows very low discharge capacity (33.4 mAh g−1). CV results shows the significant suppression in the intensity of H2–H3 which indicates the superior electrochemical stability of LaO-0.2 NCM. Thus, we can confirm that La2O3 coating is promising technique to achieve superior electrochemical performance in the long term cycling process. 相似文献
4.
LiNi0.5Mn1.5O4 was synthesized as a cathode material for Li-ion batteries by a sonochemical reaction followed by annealing, and was characterized by XRD, SEM, HRTEM and Raman spectroscopy in conjunction with electrochemical measurements. Two samples were prepared by a sonochemical process, one without using glucose (sample-S1) and another with glucose (sample-S2). An initial discharge specific capacity of 130 mA h g−1 is obtained for LiNi0.5Mn1.5O4 at a relatively slow rate of C/10 in galvanostatic charge–discharge cycling. The capacity retention upon 50 cycles at this rate was around 95.4% and 98.9% for sample-S1 and sample-S2, respectively, at 30 °C. 相似文献
5.
X. Montero W. Fischer F. Tietz D. St?ver M. Cassir I. Villarreal 《Solid State Ionics》2009,180(9-10):731-737
Oxides resulting from discrete changes in composition within the quasi-ternary system La0.8Sr0.2CuO2.4 + δ–La0.8Sr0.2CoO3 ? δ–La0.8Sr0.2FeO3 ? δ were investigated under similar experimental conditions with the objective of obtaining an overview of the variation of the relevant properties for possible applications as cathode contact layer in SOFCs. Twenty-two oxide compositions within this system were systematically selected and synthesized under identical conditions by the Pechini method. The distribution of the different crystallographic phases at 1050 °C within this quasi-ternary phase diagram, the DC electrical conductivity at 800 °C and the thermal expansion coefficients are presented. Perovskites of different compositions issued from this ternary diagram were tested as cathode contact material between an La0.8Sr0.2FeO3 cathode and a Crofer22APU interconnect by resistance measurements at 800 °C. The application of a MnCo1.9Fe0.1O4 spinel protection reduced the interfacial reaction between the Crofer22APU and the cathode contact material. Electrical resistance measurements at 800 °C in air up to 1000 h and the analysis by scanning electron microscopy/energy-dispersive X-ray spectroscopy of the sample cross-sections were carried out to verify the surface stability and the electrical performance. 相似文献
6.
For the first time, a sonochemical process has been used to synthesis cobalt oxide Co3O4 nanoflowers and nanorods morphology in the presence of the ionic liquid 1-Ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF4] as reaction media and morphology template. Different sonication time periods and different molar ratios of the ionic liquid (IL) were used to investigate their effects on the structural, optical, chemical and magnetic properties of the produced Co3O4 nanoparticles. During synthesis process brown powder contains cobalt hydroxide Co(OH)2 and cobalt oxyhydroxide (Cobalt hydroxide oxide) CoO(OH) was formed, after calcination in air for 4 h at 400 °C a black powder of Co3O4 nanoparticles was produced. The produced Co3O4 nanoparticles properties were characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), transmission electron microscopy (TEM), FTIR spectroscopy, UV–vis spectroscopy, and Vibrating Sample Magnetometer (VSM). To explain the formation mechanism of Co3O4 NPs some investigations were carried on the brown powder before calcination. 相似文献
7.
In this study, the synthesis of Mn3O4 (husmannite) nanoparticles was carried out in two different alkali media under sonication by ultrasonic bath and conventional method. Manganese acetate was used as precursor, sodium hydroxide and hexamethylenetetramine (HMT) as basic reagents in this synthesis. An ultrasonic bath with low intensity was used for the preparation of nanomaterials. The as prepared samples were characterized with X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (HRTEM, TEM), energy-dispersive spectrum (EDS), and superconducting quantum interference device (SQUID) analysis. The XRD patterns exhibit the nanocrystals are in pure tetragonal phase. The chemical composition was obtained by EDS analysis and confirmed the presence of Mn and O in the sample. According to the TEM and HRTEM results, both nanorods and nanoparticles of Mn3O4 were obtained in the presence of ultrasonic irradiation. The average size of nanoparticles was 10 nm, and the size of nanorods was 12 nm in diameter and 100-900 nm in length for the samples prepared in basic medium with sodium hydroxide. In the conventional method with the same basic medium, the nanorod was not observed and the nearly cubic nanoparticles was appeared with an average size of 2.5 nm. The selected area electron diffraction (SAED) patterns revealed that the nanocrystals are polycrystalline in nature. When HMT was used as a basic reagent in the presence of ultrasonic irradiation, it was led to a higher size of nanoparticles and nanorods than when sodium hydroxide was used as a basic reagent. The average size of nanoparticles was about 15 nm and its shape was nearly cubic. The diameter for nanorods was 50 nm and the length was about a few micrometers.The magnetic measurements were carried out on the sample prepared in sodium hydroxide under ultrasonic irradiation. These measurements as a function of temperature and field strength showed a reduction in ferrimagnetic temperature (Tc = 40 K) as compared to those reported for the bulk (Tc = 43 K). The superparamagnetic behavior was observed at room temperature with no saturation magnetization and hysteresis in the region of measured field strength. 相似文献
8.
Liangbao Yang Zhiyong Bao Yucheng Wu Jinhuai Liu 《Journal of Raman spectroscopy : JRS》2012,43(7):848-856
The solid‐phase synthesis of Ag‐coated Fe3O4 microsphere was elaborated under argon atmosphere. This straightforward process utilized neither reducing agents nor electric current and involved the dry mixing of a precursor of CH3COOAg with Fe3O4 microspheres followed by heating in an inert atmosphere. Ag nanoparticles with diameters of 30–50 nm were well‐decorated on the surfaces of Fe3O4 microspheres. The as‐synthesized Ag‐coated Fe3O4 microspheres were assembled into a surface‐enhanced Raman scattering (SERS) substrate holding clean and reproducible properties under an externally exerted magnetic force. Using these nanoprobes, analyte molecules can be easily captured, magnetically concentrated, and analyzed by SERS. This clean SERS substrate was used to detect 4‐aminothiophenol, even at a concentration as low as1.0 × 10–12 M. In particular, the Ag‐coated Fe3O4 microspheres, acting as reproducible SERS substrates, were applied to detect methyl‐parathion and 4‐mercaptopyridine. Strong SERS signals were obtained with the analytes at a concentration of 1.0 × 10–6 M. The unique, clean, and reproducible properties indicate a new route in eliminating the single‐use problem of traditional SERS substrates and show promising applications for detecting other organic pollutants. Similarly, this work may provide a new model system to a series of metal–Fe3O4 decorating reactions for a reproducible utilization. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
9.
10.
N. Ben Sari-Zizi J. Demaison B. Bakri H. Bürger 《Journal of Molecular Spectroscopy》2004,228(2):511-527
The two substates v4 = 20 (A1, 983.702 cm−1) and v4 = 2±2 (E, 986.622 cm−1) of the oblate symmetric top molecule, 14NF3, have been studied by high-resolution (2.5 × 10−3 cm−1) infrared spectroscopy of the overtones and 2ν4 − ν4 hot bands. Transitions of the overtone, the hot band, and the previously measured fundamental band were combined to yield 585 ground state combination differences differing in K by ±3, with Kmax = 36. Using the “loop-method,” a fit (standard deviation σ = 0.320 × 10−3 cm−1) provided a complete set of the hitherto not experimentally known axial ground state constants. In units of cm−1 these have the following values: . Upper state parameters were determined using a vibrationally isolated model. Considering l (2, 2) and l (2, −1) interactions between the v4 = 20 and v4 = 2±2 substates and effects accounting for the l (4, −2) interactions within the kl = −2 levels, 25 upper state parameters were obtained by fitting 2747 IR data (1842 transitions, 905 deduced energies, Jmax = 42, Kmax = 39) with σIR = 0.353 × 10−3 cm−1. Moreover, millimeter-wave spectroscopy furnished 86 transitions (Jmax = 16, Kmax = 13) measured on the v4 = 2 excited state. A merged fit, refining 24 parameters using the described model gave σIR = 0.365 × 10−3 cm−1 andσMMW = 0.855 × 10−6 cm−1 (26 kHz). The anharmonicity constants (in cm−1) are x44 = −0.84174 (2) and g44 = + 0.73014 (1). In addition to this model, the D, Q, and L reductions of the rovibrational Hamiltonian were tested. Standard deviations σIR = 0.375 × 10−3 cm−1 and σMMW = 0.865 × 10−6 cm−1 were obtained for both D and L reductions, and σIR = 0.392 × 10−3 cm−1 and σMMW = 0.935 × 10−6 cm−1 for Q reduction. The unitary equivalence of the majority of the 18 tested relations between the derived parameters was satisfactorily fulfilled. This confirms that the v4 = 2 excited vibrational state can be considered in reasonable approximation to be isolated. 相似文献