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1.
LiFePO4/C composite nanobelts were synthesized by calcination of the [LiOH + Fe(NO3)3 + H3PO4]/polyvinyl pyrrolidone (PVP) electrospun nanobelts. PVP was used as the electrospinning template and carbon source. During the calcination, [LiOH + Fe(NO3)3 + H3PO4] were transformed to lithium iron phosphate (LiFePO4) and PVP was decomposed into carbon. The morphology and properties of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller (BET) specific surface area analysis, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. The results indicate that the mean width of LiFePO4/C composite nanobelts is 2.50 ± 0.33 μm, the average thickness is about 162 nm and the BET specific surface area is 19.4 mg?1. The addition of carbon does not affect the structure of LiFePO4, but improves its electrochemical performances. At the current density of 0.2 C, the initial discharge capacity of LiFePO4/C electrode is 123.38 mAh g?1 and there is no obvious capacity fading after 50 cycles. The formation mechanism of LiFePO4/C composite nanobelts was also proposed.  相似文献   

2.
In this paper, we report on the high electrical storage capacity of composite electrodes made from nanoscale activated carbon combined with either poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) or PEDOT doped with multiple dopants such as ammonium persulfate (APS) and dimethyl sulfoxide (DMSO). The composites were fabricated by electropolymerization of the conducting polymers (PEDOT:PSS, doped PEDOT) onto the nanoscale activated carbon backbone, wherein the nanoscale activated carbon was produced by ball-milling followed by chemical and thermal treatments. Activated carbon/PEDOT:PSS yielded capacitance values of 640 F g?1 and 26 mF cm?2, while activated carbon/doped PEDOT yielded capacitances of 1183 F g?1 and 42 mF cm?2 at 10 mV s?1. This is more than five times the storage capacity previously reported for activated carbon–PEDOT composites. Further, use of multiple dopants in PEDOT improved the storage performance of the composite electrode well over that of PEDOT:PSS. The composite electrodes were characterized for their electrochemical behaviour, structural and morphological details and electronic conductivity and showed promise as high-performance energy storage systems.  相似文献   

3.
Porous carbon nitride (CN) spheres with partially crystalline frameworks have been successfully synthesized via a nanocasting approach by using spherical mesoporous cellular silica foams (MCFs) as a hard template, and ethylenediamine and carbon tetrachloride as precursors. The resulting spherical CN materials have uniform diameters of ca. 4 μm, hierarchical three-dimensional (3-D) mesostructures with small and large mesopores with pore diameters centered at ca. 4.0 and 43 nm, respectively, a relatively high BET surface area of ∼550 m2/g, and a pore volume of 0.90 cm3/g. High-resolution transmission electron microscope (HRTEM) images, wide-angle X-ray diffraction (XRD) patterns, and Raman spectra demonstrate that the porous CN material has a partly graphitized structure. In addition, elemental analyses, X-ray photoelectron spectra (XPS), Fourier transform infrared spectra (FT-IR), and CO2 temperature-programmed desorption (CO2-TPD) show that the material has a high nitrogen content (17.8 wt%) with nitrogen-containing groups and abundant basic sites. The hierarchical porous CN spheres have excellent CO2 capture properties with a capacity of 2.90 mmol/g at 25 °C and 0.97 mmol/g at 75 °C, superior to those of the pure carbon materials with analogous mesostructures. This can be mainly attributed to the abundant nitrogen-containing basic groups, hierarchical mesostructure, relatively high BET surface area and stable framework. Furthermore, the presence of a large number of micropores and small mesopores also enhance the CO2 capture performance, owing to the capillary condensation effect.  相似文献   

4.
The ordered ultrathin films based on the fabrication of Mg/Fe-LDHs ([Mg6Fe2(OH)16CO3·(H2O)4.5]0.375) nanosheets and hexacyanoferrate(III) anions via the self-assembly procedure were prepared. The electrodes modified by the films demonstrated a couple of well-defined reversible redox peaks attributed to [Fe(CN)6]3?/4? and Fe2+/3+ couples. The effects of cycle number, scan rate and Mg/Fe molar ratio on the CV performance of the thin-film electrodes were observed in K3[Fe(CN)6] electrolyte. The [Fe(CN)6]3? pillared Mg/Fe-LDHs with Mg/Fe molar ratio of 3 (LDH-(CN)-3) demonstrated an excellent electrochemical behavior with a potential window between ??0.2 and 1.0 V, high specific capacitance and sensitivity, indicating that the high crystallinity, large specific surface area and plentiful [Fe(CN)6]3? anions in interlayer spaces were necessary. Especially, the interlayer [Fe(CN)6]3? anions significantly affected the electrochemical behavior of the electrode, where the electrode reaction was controlled by the diffusion of [Fe(CN)6]3?/4? and Fe2+/3+ couples. Under current density of 2.5 A g?1, the optimized LDH-(CN)-3 electrode exhibited high specific capacitance of 250.81 F g?1 with good cycling stability. This facile synthesis strategy and the good electrochemical properties indicated that the LDH-(CN)-3 was a potential economical alternative material for supercapacitor application.  相似文献   

5.
LiFePO4/C/Ag composite hollow nanofibers were synthesized by calcination of the coaxial electrospun nanofibers with polyvinyl pyrrolidone (PVP) as core and [LiOH + Fe(NO3)3 + H3PO4]/PVP/AgNO3 as shell. PVP was used as the electrospinning template and carbon source. During the calcination, LiFePO4 precursor was transformed to LiFePO4 while AgNO3 and PVP were decomposed into silver and carbon. The morphology and properties of the as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, BET specific surface area analysis, electrochemical impedance spectroscopy and galvanostatic charge–discharge measurements. The results indicate that the mean diameter of as-prepared LiFePO4/C/Ag composite hollow nanofibers is 154.5 ± 18.6 nm and the BET specific surface area is 119.14 m2 g?1. The addition of silver and carbon does not affect the structure of LiFePO4, but improves its electrochemical performances. At the current density of 0.2 C, the initial discharge capacity of LiFePO4/C/Ag hollow nanofibers electrode is 138.71 mAh g?1, which is higher than that of LiFePO4/C nanofibers electrode. The improved specific capacity may be attributed to increase electrode conductivity after the introduction of silver. The formation mechanism of the LiFePO4/C/Ag composite hollow nanofibers was also proposed.  相似文献   

6.
The aim of the study was to use carbon fibers and carbon blacks to improve the thermal conductivity, mechanical and dielectric properties of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO3) composites. It was found that 7.5 vol% carbon blacks, with high specific surface area, can make complex viscosity of EPDM/BaTiO3 compound to become non-sensitive to varying shear. Due to the sulfuric atom and C=C groups on surface of carbon blacks, 10 vol% carbon blacks can enhance the tensile strength and tear strength of EPDM/BaTiO3 (70/30) from 9.00 MPa and 21.06 kN m?1 to 14.32 MPa (59% increase) and 30.02 kN m?1 (43% increase). It was found that the 10 vol% spherical carbon blacks with high specific area can partially contact BaTiO3 and fill the gap between BaTiO3 particles to increase thermal conductivity and dielectric constant of EPDM/BaTiO3(70/30) from 0.323 W m?1 K?1and 7 at 5 MHz to 0.632 W m?1 K?1 (95% increase) and 746 (106 times increase) at 5 MHz, respectively. When the filler content was 10 vol%, carbon blacks and carbon fibers can decrease the volume resistivity of EPDM/BaTiO3 (70/30) from 2.23?×?1013 to 6.37?×?105 Ω m (eight order of magnitude drop) and 4.25?×?1011 Ω m (two order of magnitude drop), respectively.  相似文献   

7.
The concept of electrical probe memory using phase-change media has recently received considerable attention due to its promising potential for next-generation data storage device. However, the physical performances of the conventional electrical probe memory are strongly limited by its diamond-like carbon capping layer ascribed to its large contact resistance and sharp difference between the theoretically optimized properties values and the experimentally measured values. Therefore, the diamond-like carbon capping layer is replaced by a titanium nitride layer here, and the modified device architecture is re-optimized by a newly developed three-dimensional model, resulting in a media stack consisting of a 2-nm Ge2Sb2Te5 layer sandwiched by 2-nm titanium nitride layer with an electrical conductivity of 2?×?105 Ω?1 m?1 and a thermal conductivity of 12 W m?1 K?1, and a 40-nm titanium nitride bottom layer with an electrical conductivity of 2?×?106 Ω?1 m?1 and a thermal conductivity of 12 W m?1 K?1. The advantageous features of such a device on the writing of both crystalline and amorphous bits are also demonstrated according to the developed model.  相似文献   

8.
The UV–visible spectrophotometric method has been described the study of raw carbon nanotubes (R-MWCNTs) and functionalized multiwall carbon nanotubes (F-MWCNTs) for the control of bacterial growth by using validated analytical techniques. The absorption spectra of functionalized carbon nanotubes (F-MWCNTs) and raw carbon nanotubes (R-MWCNTs) show maximum absorbance at λ max 600 nm. The linear relationship was found between absorbance and concentration of R-MWCNTs and F-MWCNTs in the range of 0.25–2.0 μg mL?1. The linear regression equation was evaluated by statistical treatment of calibration data and gives the value of correlation coefficient for F-MWCNTs (0.9999) and R-MWCNTs (0.9993), which indicate excellent linearity. The Optical and regression characteristics of the proposed method were found apparent molar absorptivity, limits of detection (LOD), and limit of quantitation (LOQ) for R-MWCNTs and F-MWCNTs (5.75 × 102: 8.25 × 102 L mol?1 cm?1), (0.052: 0.018 μg mL?1), and (0.055: 0.158 μg mL?1), respectively. The validity of the proposed method was checked by precision, accuracy, linearity, limits of detection (LOD), and limit of quantitation (LOQ). The RSD (%) and quantitative recoveries (%) were obtained (0.026–0.0086) and (100.34 and 100.71) for R-MWCNTs: for F-MWCNTs by UV–visible spectrophotometric, respectively.  相似文献   

9.
In this work, we synthesized p-phenylenediamine modified carbon nanotubes (P-CNTs) by diazotization reaction. The resulting material shows a BET surface area of 285 m2 g?1 and a total volume of 0.65 cm3 g?1 with abundant mesopores. Also, the P-CNTs exhibit good surface hydrophobicity with water contact angle of 140.8°, which should be attributed to the cooperation of both surface roughness and hydrophobic chemical compositions (aromatic rings linkages) of P-CNTs. Taking advantages of the intrinsic porosity and surface hydrophobicity, the resulting P-CNTs exhibit a notably selective absorbing ability and good recyclability for removal of organics and oils from water, which makes them the promising candidates for liquid–liquid separation and waste oil treatment.  相似文献   

10.
Nowadays, carbon nanotubes with differences in specific surface area, dopants, or functional groups are used in a number of applications, electrolysis not excluding. Various types of carbon nanotubes could improve bare graphite electrode properties by different way and so result in obtaining the different records for the same analyte. The automobile catalysts represent mobile sources of palladium. Levels of palladium in environment are continuously increasing and they need to be monitored. Electrochemistry is a useful and inexpensive component of the field of environment monitoring. For Pd(II) electrochemical determination, six types of carbon nanotubes were used as paraffin impregnated graphite electrode (PIGE) surface modifiers. Voltammetric determination brought interesting results of LOD, LOQ, standard and relative precisions of the method. These parameters as well as prediction intervals were calculated according to the technical procedure DIN 32 645 for the six electrodes and three pH values. Modification of PIGE with nitrogen doped carbon nanotubes (LOD = 1.91 × 10?5 mol L?1 or 3.14 × 10?5 mol L?1 for pH 3 and pH 4.5, respectively) seems very promising. In laboratory, functionalized carbon nanotubes, with specific surface area 200 m2 g?1, provided LOD = 1.49 × 10?5 mol L?1 (pH = 3) and 1.42 × 10?5 mol L?1 (pH = 4.5)  相似文献   

11.
We prepare the hollow carbon nanospheres (HCNs) by employing SiO2 nanospheres as hard template, 5-Hydroxymethylfurfural (HMF) as carbon precursor under hydrothermal conditions. The HCNs show uniform spherical morphology copied from SiO2 nanospheres and exhibit large cavity, thin shell structure with the surface area of 790 m2 g?1 and pore volume of 2.23 cm3 g?1. Owing to their large internal voids and high surface area, the HCNs exhibit a promising prospect for CO2 capture with the capacity of 3.04 mmol g?1 at 1.0 bar and 298 K, as well as good recyclability for CO2 after ten adsorption-desorption cycles.  相似文献   

12.
Conjugated polymers are promising light harvesters for water reduction/oxidation due to their simple synthesis and adjustable bandgap. Herein, both cyanamide and triazole functional groups are first incorporated into a heptazine‐based carbon nitride (CN) polymer, resulting in a mesoporous conjugated cyanamide‐triazole‐heptazine polymer (CTHP) with different compositions by increasing the quantity of cyanamide/triazole units in the CN backbone. Varying the compositions of CTHP modulates its electronic structures, mesoporous morphologies, and redox energies, resulting in a significantly improved photocatalytic performance for both H2 and O2 evolution under visible light irradiation. A remarkable H2 evolution rate of 12723 µmol h?1 g?1 is observed, resulting in a high apparent quantum yield of 11.97% at 400 nm. In parallel, the optimized photocatalyst also exhibits an O2 evolution rate of 221 µmol h?1 g?1, 9.6 times higher than the CN counterpart, with the value being the highest among the reported CN‐based bifunctional photocatalysts. This work provides an efficient molecular engineering approach for the rational design of functional polymeric photocatalysts.  相似文献   

13.
The effect of the nonstoichiometric compound terbium dioxide (Tb4O7) on the thermoelectric properties of tungsten trioxide (WO3) ceramics was investigated. Among the sintered ceramics, the sample doped with 0.1 mol% Tb4O7 showed the maximum grain size and density. Doping with Tb4O7 also increased the electrical conductivity (σ) of the ceramics by about two orders of magnitude, and the sample doped with 0.1 mol% Tb4O7 showed the highest electrical conductivity. The absolute value of Seebeck coefficient (|S|) of the doped samples increased as well. Consequently, the power factor (σs 2) markedly increased. The sample doped with 2.0 mol% Tb4O7 demonstrated the maximum σs 2 of 2.88 μW m?1 K?2 at 973 K, which was larger than the highest recorded σs 2 for WO3 ceramics (2.71 μW m?1 K?2 at 1,023 K). In addition, the low-doped sample (0.1 mol%) exhibited excellent thermoelectric properties.  相似文献   

14.
The reaction mechanism of V2O5 xerogel and the electrode properties of V2O5/carbon composites in an aqueous electrolyte solution were examined to obtain high-performance electrodes for rechargeable proton batteries. Based on the results of the chemical analysis of the electrode, proton intercalation is suggested to be the dominant reaction mechanism. By using the relationship between the capacity and current density of a thin-film electrode consisting of V2O5 xerogel, the diffusion coefficient in the V2O5 xerogel was determined to be 8 ± 1 × 10?11 cm2 s?1. The V2O5/carbon composite electrode was prepared by drying a homogeneous dispersion of carbon particles in the V2O5 sol. The composite electrodes showed a large capacity of 460 mAh g?1 at a current density of 1 A g?1 and maintained a relatively large capacity of 160 mAh g?1 at 100 A g?1. These properties were attributed to the homogeneous microstructure of the V2O5/carbon composites. The V2O5/carbon composite electrodes were thus revealed as high-performance electrodes with large capacities and excellent high-rate capabilities.  相似文献   

15.
Multilayer super-short carbon nanotubes (SSCNTs) could be synthesized by tailoring the raw multiwalled carbon nanotubes with a simple ultrasonic oxidation-cut method. Nanostructured layered nickel hydroxide and SSCNTs have been successfully assembled to form Ni(OH)2/SSCNTs composite by electrostatic force. Compared with pure Ni(OH)2 (665 F g?1), the Ni(OH)2/SSCNTs composite exhibits the much better electrochemical performance with a specific capacitance of 1887 F g?1 at 1 A g?1, and demonstrates a good rate capability and excellent long-term cyclic stability (92 % capacity retention after 3000 cycles). It is the reason that the SSCNTs can form a conductive network onto the surface of Ni(OH)2 nanoflakes, and their excellent electric conductivity is advantaged to the charge transport on the electrode in discharge process and charge process. Therefore, the greatly enhanced capacitive performance of Ni(OH)2/SSCNTs can be attributed to a synergetic effect of Ni(OH)2 and SSCNTs.  相似文献   

16.
In this paper, bamboo-like, O-doped carbon tubes with hierarchical pore structure have been fabricated by the direct pyrolysis of dual cross-linked polydivinylbenzene (PDVB) tubes. The bamboo-like, cross-linked PDVB tubes are firstly synthesized by cationic polymerization of divinylbenzene in cyclohexane using BF3/Et2O complex as the initiator. After a secondary cross-linking being imposed by Friedel–Crafts reaction in CCl4 using anhydrous AlCl3 as the catalyst, the obtained dual cross-linked, carboxylic acid functionalized PDVB tubes are directly subjected to pyrolysis, yielding bamboo-like, O-doped porous carbons. The resultant O-doped porous carbon tubes (BCTF-900, pyrolyzed at 900 °C) exhibit a trimodal pore structure (micro-, meso-, and macropores) with a relatively high specific surface area of 595 m2 g?1 and a low total pore volume of 0.37 cm3 g?1. Such bamboo-like carbon tubes display good volumetric capacitive performance (254 F cm?3 at 0.5 A g?1), moderate volumetric energy density (12.9 Wh L?1 at 428 W L?1), and excellent cycling stability (the capacitance retention has remained at 96.9% after 10000 cycles at 2 A g?1). Due to their unique bamboo-like architecture and trimodal pore structure, the PDVB-derived carbon tubes should have widely application prospect.  相似文献   

17.
This paper reports results of a research project which attempts to produce low-cost activated carbon from agro-residue wastes. The ground coffee residue which is a by-product of coffee making was collected from coffee shops, prepared, and converted to activated carbon by a chemical activation method. The objective of this work is to investigate the effects of preparation conditions on properties of the activated carbon obtained. The preparation condition is defined by pyrolysis rate, concentration of ZnCl2, impregnation time, and carbonization temperature. The pyrolysis rate was fixed at 10 °C min?1 for 4 h with three concentrations of ZnCl2 (5, 10, and 15 wt%), three durations of impregnation time (8, 12, and 24 h), and three carbonization temperatures (400, 450, and 500 °C). The morphology and specific surface area were, respectively, determined using SEM and BET techniques. It was found in this study that the activated carbon with the best properties was obtained at the preparation condition given by 15 wt% of ZnCl2, impregnation time of 24 h, and 500 °C carbonization temperature. On average, the activated carbon had a pore diameter of 0.61 nm, specific surface area of 831 m2 g?1, and a total pore volume of 0.44 cm3 g?1. It was also found that the adsorption isotherm of Cu (II) fitted well with Freundlich isotherm.  相似文献   

18.
In this work, we have employed melamine, cyanuric acid and thymine to fabricate triazine-based carbon nitrides (CNs) by supramolecular approach. The resultant CNs possess large specific surface area, hierarchical porous structure, better light absorption capacity and high separation rate of photoinduced carriers. Then, the photocatalytic reduction and oxidation performance has been evaluated. The obtained CNs exhibit enhanced photocatalytic reduction performance on water splitting to H2, the largest hydrogen evolution rate can reach 8466.3 μmol g?1 h?1, which is 81.9 times as high as that of bulk CN. Simultaneously, the porous CNs show excellent photocatalytic reduction ability on the conversion of CO2 to H2, CO and CH4. Of particular interest is that they have high selectivity for CO. It’s worth noting that the porous CNs also possess outstanding photocatalytic oxidation ability on high concentration nitric oxide (NO), and the highest NO conversion rate can reach 79.3% under visible light. The enhanced photocatalytic performance for the multifunctional porous CN can be ascribed to the synergic effect of large specific surface area, strong light absorption capacity and fast separation of photoinduced electron–hole pairs. Finally, the photocatalytic reduction and oxidation mechanism of the porous CN is also proposed and discussed.  相似文献   

19.
In this work, a functionalized mesoporous carbon (CMK-3-O) was synthesized after oxidation with nitric acid and was used to adsorb dibenzothiophene (DBT) from model oil for the first time. Then, its performance was compared with that of CMK-3. The functionalized mesoporous carbon, CMK-3-O, showed better a capacitance performance for DBT adsorption than that of CMK-3. The maximum adsorption capacity was obtained for functionalized mesoporous carbon at optimum conditions with 6 M HNO3 aqueous solution and 30 min contact time. The physical and structural properties of CMK-3-O and CMK-3 were investigated with X-ray diffraction method (XRD), N2 adsorption–desorption isotherm, FT-IR, and elemental analysis (CHNO). Results of the elemental analysis showed that the oxygen and nitrogen content has increased and the carbon content has decreased through oxidation treatment. The effects of various factors on the adsorption process (such as temperature, amount of adsorbent, contact time, and concentration) of DBT were studied. CMK-3-O showed a maximum adsorption capacity of 86.96 mg DBT g?1 of CMK-3-O at optimized conditions (temperature, 25°C; adsorbent dosage, 20 g L?1; contact time, 60 min), which was a higher adsorption capacity of that observed for CMK-3 (57.47 mg DBT g?1 of CMK-3). Kinetic studies have revealed that the adsorption of DBT can be described by a pseudo-second-order rate equation. Equilibrium data showed that adsorption process was best represented by the Langmuir model. The results also illustrated the fact that the regenerated adsorbent afforded 64.3% of the initial adsorption capacity after the two regeneration cycles.  相似文献   

20.
V doped SnO2 and SnO2:F thin films were successfully deposited on glass substrates at 500 °C with spray pyrolysis. It was observed that all films had SnO2 tetragonal rutile structure and the preferential orientation depended on spray solution chemistry (doping element and solvent type) by X-ray diffraction measurements. The lowest sheet resistance and the highest optical band gap, figure of merit, infrared (IR) reflectivity values of V doped SnO2 for ethanol and propane-2-ol solvents and V doped SnO2:F films were found to be 88.62 Ω–3.947 eV–1.02 × 10?4 Ω?1–65.49 %, 65.35 Ω–3.955 eV–8.54 × 10?4 Ω?1–72.58 %, 5.15 Ω–4.076 eV–6.15 × 10?2 Ω?1–97.32 %, respectively, with the electrical and optical measurements. Morphological properties of the films were investigated by atomic force microscope and scanning electron microscope measurements. From these analysis, the films consisted of nanoparticles and the film morphology depended on doping ratio/type and solvent type. It was observed pyramidal, polyhedron, needle-shaped and spherical grains on the films’ surfaces. The films obtained in present study with these properties can be used as front contact for solar cells and it can be also one of appealing materials for other optoelectronic and IR coating applications.  相似文献   

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