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1.
Nanocrystalline LiNi1/3Co1/3Mn1/3O2 cathode materials are synthesized by sol–gel method using polyacrylic acid as a chelating agent. The effects of the calcination temperature and calcination time on the structure, morphology, and electrochemical performances of the LiNi1/3Co1/3Mn1/3O2 electrode materials are investigated by X-ray diffraction, scanning electron microscopy and charge–discharge cycling test, respectively. All experiments show that the microscopic structural features and the morphology properties are deeply related with the electrochemical performance. The results show that the nanocrystalline LiNi1/3Co1/3Mn1/3O2 with a particle size of 80 nm sintered at 700 °C for 2 h presents good α-NaFeO2 layer structure and the best electrochemical performance. When it is discharged between 4.4 and 2.8 V at 20 mAg?1, the initial specific capacity of the LiNi1/3Co1/3Mn1/3O2 obtained at 700 °C for 2 h is 169.2 mAhg?1. The investigated electrode materials retain 151 mAhg?1 after 30 cycles when cycled at 20 mAg?1.  相似文献   

2.
Lithium-rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template and studied as a positive electrode material. The as-prepared sample possesses good crystalline structure with a broadly distributed mesoporosity but low surface area. As expected, cyclic voltammetry and charge–discharge data indicate poor electrochemical activity. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g?1 is obtained. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g?1. The rate capability study suggests that the sample provides about 150 mAh g?1 at a specific discharge current of 1.25 A g?1. Although the cycling stability is poor, the high rate capability is attributed to porous nature of the material.  相似文献   

3.
In this project, we synthesized TiO2 compounds through the molten salt method (MSM) using Ti(IV) oxysulfate, as the Ti source. Molten salts in the ratio of 0.375 M LiNO3:0.180 M NaNO3:0.445 M KNO3 were added and heated at temperatures of 145, 280, 380, and 480 °C for 2 h in air, respectively. A part of the sample prepared at 145 °C was further reheated to 850 °C for 2 h in air. X-ray diffraction studies showed that the amorphous phase was obtained when the sample was prepared at 145 °C, and polycrystalline to crystalline anatase phase was formed when heated from 280 to 850 °C, which is complementary to the results of selected area electron diffraction studies. Electrochemical properties were studied using galvanostatic cycling, cyclic voltammetry, and electrochemical impedance spectroscopy at a current density of 33 mA g?1 (0.1 C rate) and a scan rate of 0.058 mV s?1, in the voltage range 1.0–2.8 V vs. Li. Electrochemical cycling profiles for the amorphous TiO2 samples prepared at 145 °C showed single-phase reaction with a low reversible capacity of 65 mAh g?1, whereas compounds prepared at 280 °C and above showed a two-phase reaction of Li-poor and Li-rich regions with a reversible capacity of 200 mAh g?1. TiO2 produced at 280 °C showed the lowest capacity fading and the lowest impedance value among the investigated samples.  相似文献   

4.
LaSr3Fe3O10 ? δ powders were synthesized by hydrothermal method and characterized by XRD and SEM. The XRD patterns showed that the sample calcined at 1000 °C was single phase and the sample calcined at 900 °C had tiny amount of LaSrFeO4 phase. The single-phase LaSr3Fe3O10 ? δ powders were used to prepare test electrode. The capacitive behaviors of LaSr3Fe3O10 ? δ electrode were analyzed by cyclic voltammetry, galvanostatic charge-discharge techniques, and electrochemical impedance spectroscopy. The electrochemical results showed a capacity as high as 470 F g?1 at a scan rate of 1 mV s?1 and 380 F g?1 at a charge-discharge current density of 0.1 A g?1 in 6 M KOH solution. The electrode showed good cyclic stability since its capacitive retention is 87.1% after 1000 charge-discharge cycles. The electrochemical performances suggest that LaSr3Fe3O10 ? δ could be a potential candidate as a capacitive electrode material.  相似文献   

5.
LiNi0.80Co0.15Al0.05O2 (NCA) is explored to be applied in a hybrid Li+/Na+ battery for the first time. The cell is constructed with NCA as the positive electrode, sodium metal as the negative electrode, and 1 M NaClO4 solution as the electrolyte. It is found that during electrochemical cycling both Na+ and Li+ ions are reversibly intercalated into/de-intercalated from NCA crystal lattice. The detailed electrochemical process is systematically investigated by inductively coupled plasma-optical emission spectrometry, ex situ X-ray diffraction, scanning electron microscopy, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy. The NCA cathode can deliver initially a high capacity up to 174 mAh g?1 and 95% coulombic efficiency under 0.1 C (1 C?=?120 mA g?1) current rate between 1.5–4.1 V. It also shows excellent rate capability that reaches 92 mAh g?1 at 10 C. Furthermore, this hybrid battery displays superior long-term cycle life with a capacity retention of 81% after 300 cycles in the voltage range from 2.0 to 4.0 V, offering a promising application in energy storage.  相似文献   

6.
Cysteamine core polyamidoamine G-4 dendron branched with β-cyclodextrins was chemisorbed on the surface of Au electrodes and further coated with Pt nanoparticles. Adamantane-modified glucose oxidase was subsequently immobilized on the nanostructured electrode surface by supramolecular association. This enzyme electrode was used to construct a reagentless amperometric biosensor for glucose, making use of the electrochemical oxidation of H2O2 generated in the enzyme reaction. The amperometric response of the biosensor was rapid (6 s) and a linear function of glucose concentration between 5 and 705 μmol?L?1. The biosensor had a low detection limit of 2.0 μmol?L?1, sensitivity of 197 mA?mol?1?L?cm?2, and retained 94 % of its initial response after storage for nine days at 4 °C.  相似文献   

7.
Micro- and mesoporous carbide-derived carbons (CDCs) were synthesised from TiC powder via a gas-phase reaction using HCl and Cl2 within the temperature range of 700–1,100 °C. Analysis of X-ray diffraction results show that TiC-CDCs consist mainly of graphitic crystallites. The first-order Raman spectra showed the graphite-like absorption peaks at ~1,577 cm?1 and the disorder-induced peaks at ~1,338 cm?1. The low-temperature N2 sorption experiments were performed, and specific surface areas up to 1,214 and 1,544 m2?g?1 were obtained for TiC-CDC (HCl) synthesised at T?=?800 °C and TiC-CDC (Cl2) synthesised at T?=?900 °C, respectively. For the TiC-CDC powders synthesised, a bimodal pore size distribution has been established with the first maximum in the region up to 1.5 nm and the second maximum from 2 to 4 nm. The energy-related properties of supercapacitors based on 1 M (C2H5)3CH3NBF4 in acetonitrile and TiC-CDC (Cl2) and TiC-CDC (HCl) as electrode materials were also investigated by cyclic voltammetry, impedance spectroscopy, galvanostatic charge/discharge and constant power methods. The specific energy, calculated at U?=?3.0 V, are maximal for TiC-CDC (Cl2 800 °C) and TiC-CDC (HCl 900 °C), which are 43.1 and 31.1 W?h?kg?1, respectively. The specific power, calculated at cell potential U?=?3.0 V, are maximal for TiC-CDC (Cl2 1,000 °C) and TiC-CDC (HCl 1,000 °C), which are 805.2 and 847.5 kW?kg?1, respectively. The Ragone plots for CDCs prepared by using Cl2 or HCl are quite similar, and at high power loads, the TiC-CDC material synthesised using Cl2 at 900 °C, i.e. the material with optimal pore structure, delivers the highest power at constant energy.  相似文献   

8.
A new electrode was developed by one-step potentiostatic electrodeposition (at ?2.0 V for 20 s) of Au/SiO2 nanoparticles on a glassy carbon electrode. The resulting electrode (nano-Au/SiO2/GCE) was characterized by scanning electronic microscopy, X-ray photoelectron spectroscopy and electrochemical techniques. The electrochemical behavior of dihydronicotinamide adenine dinucleotide (NADH) at the nano-Au/SiO2/GCE were thoroughly investigated. Compared to the unmodified electrode, the overpotential decreased by about 300 mV, and the current response significantly increased. These changes indicated that the modified electrode showed excellent catalytic activity in the oxidation of NADH. A linear relationship was obtained in the NADH concentration range from 1.0?×?10?6 to 1.0?×?10?4 mol?L?1. In addition, amperometric sensing of ethanol at the nano-Au/SiO2/GCE in combination with alcohol dehydrogenase and nicotinamide adenine dinucleotide was successfully demonstrated. A wide linear response was also found for ethanol in the range from 5.0?×?10?5 to 1.0?×?10?3 mol?L?1 and 1.0?×?10?3 to 1.0?×?10?2 mol?L?1, respectively. The method was successfully applied to determine ethanol in beer and biological samples.  相似文献   

9.
Calcium carbide-derived carbons (CCDCs) produced by chlorination of CaC2 at various temperatures (400–800 °C) possess highly controllable microstructure and porosity, allowing them to serve as excellent electrode materials for the application of supercapacitor. This paper focused on the effect of pore size and specific surface area (SSA) of CCDC on its electrochemical behavior. Microstructure and micropore characteristics of CCDC were characterized by N2 adsorption/desorption isotherms, X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that SSA and average pore size increased with the increase of synthesis temperature from 400 °C to 600 °C, and then decreased when temperature reached to 800 °C. Meanwhile, a correlation between specific capacitance and SSA of micropores (less than 2 nm in diameter) has been studied. It has been found that the supercapacitor using the CCDC prepared at 600 °C as electrode material in 6 M KOH showed the maximum specific capacitance and energy density (53.61 F g?1 and 7.08 W h kg?1), outstanding rate capability, lower IR drop and 96 % retention of initial capacity over 5,000 cycles.  相似文献   

10.
La4Ni3O10 oxide was synthesized as a cathode material for intermediate-temperature solid oxide fuel cells by a facile sol–gel method using a nonionic surfactant (EO)106(PO)70(EO)106 tri-block copolymer (F127) as the chelating agent. The crystal structure, electrical conductivity, and electrochemical properties of La4Ni3O10 were investigated by X-ray diffraction, DC four-probe method, electrochemical impedance spectra, and I–V measurements. The La4Ni3O10 cathode showed a significantly low polarization resistance (0.26 Ω cm2) and cathodic overpotential value (0.037 V at the current density of 0.1 A cm?2) at 750 °C. The results measured suggest that the diffusion process was the rate-limiting step for the oxygen reduction reaction. The La4Ni3O10 cathode revealed a high exchange current density value of 62.4 mA cm?2 at 750 °C. Furthermore, an anode-supported single cell with La4Ni3O10 cathode was fabricated and tested from 650 to 800 °C with humidified hydrogen (~3 vol% H2O) as the fuel and the static air as the oxidant. The maximum power density of 900 mW cm?2 was achieved at 750 °C.  相似文献   

11.
In this study, we demonstrated a highly sensitive electrochemical sensor for the determination of glucose in alkaline aqueous solution by using nickel oxide single-walled carbon nanotube hybrid nanobelts (NiO–SWCNTs) modified glassy carbon electrode (GCE). The hybrid nanobelts were prepared by the deposition of SWCNTs onto the Ni(SO4)0.3(OH)1.4 nanobelt surface, followed by heat treatment at different temperatures ranging from 400 °C to 600 °C. The NiO–SWCNTs hybrid nanobelts modified electrode prepared at 500 °C displays enhanced electrocatalytic activity towards glucose oxidation, revealing a synergistic effect between the NiO and the deposited SWCNTs. The as-fabricated nonenzymatic glucose sensor exhibits excellent glucose sensitivity (2,980 μA cm?2 mM?1), lower detection limit (0.056 μM, signal/noise [S/N] ratio?=?3), and wider linear range (0.5–1,300 μM). Moreover, the sensor has been successfully used for the assay of glucose in serum samples with good recovery, ranging from 96.4 % to 102.4 %.  相似文献   

12.
ZnO nanoparticles (NPs) with tunable morphologies were synthesized by a hybrid electrochemical–thermal method at different calcination temperatures without the use of any surfactant or template. The NPs were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, dynamic light scattering, thermogravimetry–differential thermal analysis, scanning electron microscope and N2 gas adsorption–desorption studies. The FT-IR spectra of ZnO NPs showed a band at 450 cm?1, a characteristic of ZnO, which remained fairly unchanged at calcination temperatures even above 300 °C, indicating complete conversion of the precursor to ZnO. The products were thermally stable above 300 °C. The ZnO NPs were present in a hexagonal wurtzite phase and the crystallinity of ZnO increased with an increasing calcination temperature. The ZnO NPs calcined at lower temperature were mesoporous in nature. The surface areas of ZnO NPs calcined at 300 and 400 °C were 51.10 and 40.60 m2 g?1, respectively, which are significantly larger than commercial ZnO nanopowder. Surface diffusion has been found to be the key mechanism of sintering during heating from 300 to 700 °C with the activation energy of sintering as 8.33 kJ mol?1. The photocatalytic activity of ZnO NPs calcined at different temperatures evaluated by photocatalytic degradation of methylene blue under sunlight showed strong dependence on the surface area of ZnO NPs. The ZnO NPs with high surface area showed enhanced photocatalytic activity.  相似文献   

13.
A white calcium bentonite (CaB) taken from Çaml?dere (Ankara, Turkey) region was heated at various temperatures between 100 and 1100 °C for 2 h. The mineralogy of the CaB was determined as calcium smectite (CaS), metahalloysite (MH), opal-A (OA), opal-CT (OCT), quartz (Q), feldspar (F), and calcite (C) using the X-ray diffraction patterns of the natural CaB and its heated samples. Besides the XRD patterns, the thermogravimetry, differential thermal analysis, and low-temperature nitrogen adsorption (N2-AD) data show that the CaS lose adsorbed and hydration water up to 300 °C, dehydroxylation takes place between 300 and 750 °C, and then the 2:1 layer structure completely collapses above 900 °C. The activation energies for the dehydration and dehydroxylation were calculated as 7636 and 48838 J mol?1, respectively, from the TG data using Coats and Redfern method. The specific surface area (S) and specific micro–mesopore volume (V) obtained from N2-AD data were 44 m2 g?1 and 0.100 cm3 g?1 for the natural CaB. S and V reach their maxima of 105 m2 g?1 and 0.155 cm3 g?1, respectively, at 300 °C, remain approximately constant as the temperature increases up to 700 °C and then decrease almost in parallel with each other, reaching their minima at 900 °C. This indicates that the S and V values increase gradually during dehydration and dehydroxylation of the CaS.  相似文献   

14.
In this study, NiS2 nanocubes were successfully synthesized by a novel facile solvothermal method using NiC2O4·2H2O microstructures and used as an electrode for high-performance supercapacitors. The electrochemical properties of the prepared NiS2 electrode were studied using galvanostatic charge–discharge analysis, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) studies. Its maximum specific capacitance was 2077 F g?1 at a constant current density of about 0.65 A g?1. Further, the EIS results confirmed the pseudocapacitive nature of the NiS2 electrode. The experimental results suggested that the NiS2 electro-active material demonstrates excellent electrochemical performance with high specific capacitance, low resistance, and excellent cycling stability.  相似文献   

15.
Two kinds of electrode materials Ni(OH)2 and Ni(OH)2@Zn(OH)2 composite are fabricated on nickel foam. Electrochemical experiments indicate Ni(OH)2@Zn(OH)2 composite deserves further study due to high specific capacitance and good cycle stability, so that it can achieve energy storage and conversion as much as possible. When the hydrothermal time is different, the electrochemical performance of the sample is also different. Accurately, samples can obtain better electrochemical performance at 15 h, and the maximum specific capacitance of Ni(OH)2@Zn(OH)2 is 7.87 F cm?2 compared to Ni(OH)2 (0.61 F cm?2) at 5 mA cm?2. Even at 50 mA cm?2, specific capacitance is 5.24 F cm?2 and rate capability is 66.6%. Furthermore, Ni(OH)2@Zn(OH)2-15 h loses 19.8% after 1000 cycles, revealing the composite has an outstanding stable cycle. These properties also indicate Ni(OH)2@Zn(OH)2-15 h is a promising electrode material.  相似文献   

16.
Four nanoporous carbons obtained from different polymers: polypyrrole, polyvinylidene fluoride, sulfonated styrene–divinylbenzene resin, and phenol–formaldehyde resin, were investigated as potential adsorbents for carbon dioxide. CO2 adsorption isotherms measured at eight temperatures between 0 and 60 °C were used to study adsorption properties of these polymer-derived carbons, especially CO2 uptakes at ambient pressure and different temperatures, working capacity, and isosteric heat of adsorption. The specific surface areas and the volumes of micropores and ultramicropores estimated for these materials by using the density functional theory-based software for pore size analysis ranged from 840 to 1990 m2 g?1, from 0.22 to 1.47 cm3 g?1, and from 0.18 to 0.64 cm3 g?1, respectively. The observed differences in the nanoporosity of these carbons had a pronounced effect on the CO2 adsorption properties. The highest CO2 uptakes, 6.92 mmol g?1 (0 °C, 1 atm) and 1.89 mmol g?1 (60 °C, 1 atm), were obtained for the polypyrrole-derived activated carbon prepared through a single carbonization-KOH activation step. The working capacity for this adsorbent was estimated to be 3.70 mmol g?1. Depending on the adsorbent, the CO2 isosteric heats of adsorption varied from 32.9 to 16.3 kJ mol?1 in 0–2.5 mmol g?1 range. Overall, the carbons studied showed well-developed microporosity and exceptional CO2 adsorption, which make them viable candidates for CO2 capture, and for other adsorption and environmental-related applications.  相似文献   

17.
Crosslinked-polyaniline (CPA) nano-pillar arrays adsorbed on the surface of reduced graphene oxide (RGO) sheets were synthesized by in situ solution polymerization through two steps of reduction. The electrochemical analyses demonstrated that the befittingly reduced CPA/RGO composite exhibited high performance as electrode materials for supercapacitors. The CPA/RGO composite showed very high specific capacitance of 1532 F g?1 at a scan rate of 10 mV s?1 or 694 F g?1 at a current density of 2 A g?1 in 1 M H2SO4 electrolyte, as well as great energy density of 61.4 W h kg?1 at a current density of 2 A g?1. The electrode material also had decent power density of 4 kW kg?1 at a current density of 10 A g?1, and good cycling stability of 92.5 % capacitance retained after 500 cycles of cyclic voltammetry at 500 mV s?1. The neat microstructures and super electrochemical properties suggest the potential use of the composites in supercapacitors.  相似文献   

18.
Single-crystal magnesium-doped spinel lithium manganate cathode materials are prepared by the hydrothermal method followed by the heat treatment. XRD patterns reveal that Mg2+ions have already diffused into the Li1.088Mn1.912O4 crystal structure and not affect the Fd3m space group. SEM images demonstrate that the magnesium-doped spinel lithium manganates show uniform polyhedral single crystals with 2–4 μm. Electrochemical performance demonstrates that the optimized composition of Li1.088Mg0.070Mn1.842O4 electrode exhibits the best electrochemical properties. It delivers 92.0 mAh g?1 at 8C rates and corresponds to 90.8% capacity retention (vs. 1C), far higher than those of the pristine electrode (70.4 mAh g?1 and 69.2%). In addition, the Li1.088Mg0.070Mn1.842O4 electrode also shows 95.5% capacity retention after 100 cycles at 1C, while the pristine electrode only shows 91.0% capacity retention. The excellent electrochemical performances of Li1.088Mg0.070Mn1.842O4 electrode are ascribed to the suppressed polarization, more stable crystal structure, and better kinetic characteristics.  相似文献   

19.
The effect of different membranes and aluminum current collectors on the initial coulombic efficiency of LiNi0.5Mn1.5O4/Li was investigated, and the cycling performance at different rates and temperatures and the storage performance at 60 °C for a week are discussed for LiNi0.5Mn1.5O4/Li. The results show that the lower initial coulombic efficiency is associated with the lower decomposition voltage of the commercial membrane and electrolyte, and the instability of aluminum current collector under the higher voltage. In addition, both versions of LiNi0.5Mn1.5O4 can deliver about 115 mA?h g?1 of initial discharge capacity at 1 C at 25 °C and 60 °C; however, it retains only 61.57 % of its initial capacity after the 130th cycles at 60 °C, which is much lower than the 94.46 % rate observed for LiNi0.5Mn1.5O4 at 25 °C, and the cycling performance of the material at 1 C is better than that at 0.5 C. Meanwhile, the initial discharge capacity at 0.1 C after storing at 60 °C is 119.3 mA?h g?1, which is only a little lower than 121.5 mA?h g?1 recorded before storing; moreover, the spinel structure and surface state of LiNi0.5Mn1.5O4 after storing at 60 °C has not been changed basically. These results indicate that the electrochemical stability of electrolyte is also related to the temperature. The serious capacity fading of LiNi0.5Mn1.5O4 at 60 °C is attributed to the severe oxidation decomposition and the thermal decomposition in the range of cut-off voltage of the materials, and then the decomposition products interact with active materials to form a solid interface phase, leading to the larger electrode polarization and irreversible capacity loss. Meanwhile, the worse cycling performance at 0.5 C than that at 1 C is attributed to the longer interaction time between the electrolyte and the active materials. However, the storage performance of LiNi0.5Mn1.5O4 corresponds to the thermal stability of electrolyte to a certain extent.  相似文献   

20.
Eucalyptus wood can be utilized as a biomass feedstock for conversion to bio-oil using a pyrolysis process. Eucalyptus wood samples were initially pyrolyzed on a laboratory-scale pyrolysis system at different values in the ranges of 300–800 °C and 0.050–0.300 L min?1 to determine the effects of operation temperature and N2 flow rate, respectively, on the yields of products. Then, the bio-oil in the highest yield (wB = 44.37 %), which was obtained at pyrolysis final temperature (450 °C), heating rate (35 °C min?1), particle size (850 μm), and sweeping flow rate (0.200 L min?1), was characterized by Fourier transform infra-red spectroscopy, gas chromatography/mass spectrometry and column chromatography. Subsequently, it was shown that the operating temperature and N2 gas flow rate parameters affected the product yields. Also, some important physico-chemical properties of the pyrolytic oil obtained in high yield were determined as a calorific value of 37.85 MJ kg?1, an empirical formula of CH1.651O0.105N0.042S0.001, a rich chemical content containing many different chemical groups, a density of 981.48 kg m?3, and a viscosity of 61.24 mm2 s?1. Based on the determined properties of the pyrolytic oil, it was concluded that the use of pyrolytic oil derived from Eucalyptus wood may be useful for the production of alternative liquid fuels and fine chemicals after the necessary improvements.  相似文献   

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