查看更多>>摘要：The lithium-sulfur (Li-S) battery is considered as an appealing choice for the next-generation secondary battery due to its high theoretical energy density and low cost. However, the safety concerns and poor cycling performance caused by lithium dendrites seriously restrict its commercialization. A composite protective film with high lithium ionic conductivity has exhibited excellent inhibiting effect on the formation of lithium dendrites. Herein, Li-Nafion/Li2CO3 (LNL) composite film is developed to achieve a stable Li anode in Li-S batteries by redistributing Li+ flux. The Li-S batteries with LNL-5 film show an improved remaining discharge capacity of 730 mAh g?1 at 0.1 C after 100 cycles and rate performance of 425.4 mAh g?1 at 2 C. This work provides a rational design to suppress the formation of lithium dendrite for the stable Li anode in Li-S batteries.
查看更多>>摘要：In the present study, the role of Fe/Ca partial replacement in Bi1.8Pb0.35Sr1.9Ca2.2?xFexCu3Oy (Bi-2223) superconducting material on the crystallinity, electrical, structural morphology and superconducting properties is studied by way of the electrical resistivity (ρ-T), powder X-ray diffraction (XRD), electron dispersive X-ray (EDX) and scanning electron microscopy (SEM) measurements. According to the experimental results, the Fe additives are effectively replaced by the Ca sites in the bulk Bi-2223 superconducting system, verified by evidenced by the ρ-T and EDX results. Further, the SEM images show that the crystallinity quality and surface morphology view undermine considerably with the enhancement in the Fe/Ca partial substitution level in the Bi-2223 system because of nonuniform surface appearance with new induced permeant structural deformations, impurity residues, misorientations of grains and systematic problems in the grain boundary couplings in the superconducting system. Additionally, the disappearance or appearance of some diffraction peaks in the XRD pattern as well as the decrease in the c-axis length and increase a-axis length provides the deviation of the Bi-2223 materials from stabilization in the system because of the degradation in the crystal structure quality. Besides, the dc electrical results represent that the electrical and fundamental superconducting characteristics decrease with the increase of Fe/Ca replacement owing to the increment of inhomogeneities in the oxidation state, structural problems and mobile hole carrier concentration in the bulk Bi-2223 materials.
查看更多>>摘要：High capacity anode materials with long cycle life are required for next-generation high energy density lithium-ion batteries. Herein, SnF2/C nanocomposite is prepared using facile ball-milling method with the advantages of high capacity and stable cycling. The nanocomposite is prepared with significant particle size reduction and wrapped with a thick carbon layer as confirmed from scanning and transmission electron microscopies. The SnF2/C nanocomposite electrode demonstrates 768 mA h g?1 in the 100th cycles with a good retention of 90%. The prepared SnF2/C nanocomposite exhibits specific capacities of 974, 798, 743, 693, 632, and 565 mA h g?1 at rates of 0.1, 0.2, 0.5, 1.0, 2.0, and 5.0 C, respectively, demonstrating high rate capability. SnF2/C anode recovers a specific capacity of 765 mA h g?1 at 0.1 C after testing at high rates. Lithium diffusivity into SnF2/C nanocomposite is calculated to be 1.2 × 10?15 cm2 s?1 at the pristine state and 7.6 × 10?15 cm2 s?1 after 100 cycles using electrochemical impedance spectroscopy. The high performance of the nanocomposite is investigated using ex-situ X-ray diffraction and transmission electron microscopy. The obtained ex-situ results indicate that the nanocomposite undergoes both conversion and alloying reactions during the discharge-charge process.
查看更多>>摘要：Powders press technique is considered as a universal means for preparing cathode of thermal battery. In this work, the flexible NiS2 film cathode with thickness of 120 μm was prepared by tape-casting method. It overcame the issue of organic adhesive failure at high temperature. The NiS2 film retains comparable ductility after heat treatment at 350 °C. And no crack occurs on the surface of the film after 100 times bending. Its density is similar to NiS2 tablets. Assembled in a single thermal battery, an ultrahigh specific capacity of 648 mA h g?1 at 250 mA cm?2 can be achieved with cut-off voltage of 1.5 V. Due to its short lithium ionic transmission distance, the specific capacity increases 13% compared with NiS2 tablets. This work affords a reference significance for the research on full-component flexible thermal battery.
查看更多>>摘要：An antibiotic ampicillin was introduced in InP/ZnSexS1–x/ZnS-based quantum dot light-emitting diodes (QLEDs) to achieve charge balance via band alignment. The charge distribution on ampicillin facilitates the generation of an interfacial dipole, and the polarity of ampicillin is controlled by varying the pH of the charge transport layers of the QLEDs. In ZnO electron transport layers (ETLs), ampicillin is anionic at pH ～7.5, and the weak interfacial dipole reduces the conductivity of the ETL. The anionic ampicillin in ZnO ETL also increases the energy of the lowest unoccupied molecular orbital of ZnO from 3.55 to 3.80 eV. In PEDOT:PSS hole injection layers (HILs), ampicillin is cationic at pH ～4, and a strong interfacial dipole increases the conductivity of the HIL. The cationic ampicillin in PEDOT:PSS HIL also decreases the energy of the highest occupied molecular orbital of PEDOT:PSS from 5.25 to 5.30 eV. The improved charge balance achieved through energy band alignment enhanced the external quantum efficiency from 0.9% to 4.7%. This is the first report of a QLED in which same antibiotic material was applied to both the ETLs and HILs to enhance the band alignment, which resulted in charge balance.
查看更多>>摘要：A novel (BiO)2CO3/ZnFe-LDH photocatalyst was fabricated via a simple hydrothermal method for degradation of tetracycline aqueous solution. Due to the unique band structures of (BiO)2CO3 and ZnFe-LDH, the combination of these two materials formed a Z-scheme heterojunction, which was conducive to the separation of photo-generated carriers. Through measuring the absorbance, it was found that the composite with 5% ZnFe-LDH has the optimal photocatalytic performance among all the samples. 98.09% of tetracycline (TC) was degraded after adsorption for 30 min and light irradiation for 90 min. In addition, the (BiO)2CO3/ZnFe-LDH composite displayed a remarkable reusability and stability in five successive runs. Based on the results of characterization and performance, a possible photocatalytic mechanism was proposed. This work would be helpful for the application of composites in the field of photocatalysis.
查看更多>>摘要：MXene/CoS heterostructures were synthesized by using an electrostatic self-assembly strategy, as an electromagnetic wave (EMW) absorber to deal with EMW pollution. MXene (Ti3C2Tx) layered-structure was naturally obtained by using the typical etching method. Modified CoS hollow microspheres were deposited on the surface MXene through layer by layer electrostatic interaction. Eventually, the heterostructures exhibited significantly enhanced EMW absorption performance owing to the synergistic effect of multiple loss mechanisms. Furthermore, EMW absorption performance can be optimized by simply adjusting the mass ratio of Ti3C2Tx to CoS. Specifically, the minimum reflection loss (RLmin) was ?60.28 dB at 12.24 GHz, with an effective absorption bandwidth of 3.04 GHz, at the thickness of 1.81 mm. Accordingly, it is reasonable to believe that this structural design strategy offers a new direction for the next-generation of EMW absorbers.
查看更多>>摘要：Carbide/carbon composites are new types of electromagnetic (EM) wave absorbing materials because of their good stability, light weight, easy synthesis and excellent performance. In this work, monodisperse branched nickel carbide (Ni3C) nanoparticles with controlled morphology were fabricated through high-temperature pyrolysis of nickel acetylacetonate under anhydrous and oxygen-free conditions. Then Ni3C nanoparticles were uniformly in situ grown on the surface of reduced graphene oxide (rGO) to form nickel carbide/reduced graphene oxide (Ni3C/rGO) nanocomposite. Series of characterization and performance tests were conducted, and the results showed that the EM wave absorption performance of Ni3C/rGO composite was greatly enhanced compared with that of pure phase Ni3C nanoparticles. Due to the combined effects of interfacial polarization loss, conductivity loss and surface defects, Ni3C/rGO nanocomposite exhibited strong reflection loss in 2–18 GHz band, which could attenuate the EM waves incident to the internal loss to a greater extent. When the Ni3C/rGO composite is at 3.5 mm thickness, the maximum effective absorption bandwidth can reach 3.6 GHz, and at 3.0 mm thickness, the lowest reflection loss value can reach ? 42.8 dB. This high-performance nanocomposite can be a new candidate material for EM wave absorption.
查看更多>>摘要：By exploiting the benefit of the half-Heusler (HH) structure, the nanocomposite strategy has been an effective mechanism for most HH-based thermoelectric materials. We have successfully developed HH-based nanocomposites by economically feasible solid-state reaction (SSR) route followed by Spark Plasma Sintering (SPS). X-ray diffraction (XRD) analysis confirms the single HH phase for Zr0.66Hf0.34NiSn composition, and full-Heusler (FH) as an inclusion phase in HH matrix for Zr0.66Hf0.34Ni1+xSn (x = 0.01, 0.03, 0.05, 0.10) alloys. Energy Dispersive Spectroscopy (EDS) also reveals the nominal stoichiometric compositions to be in close matching with experimental compositions. Thermoelectric measurements have been performed for all the compositions Zr0.66Hf0.34Ni1+xSn (x = 0, 0.01, 0.03, 0.05, 0.10) from 323 to 773 K. Interestingly, increasing FH concentration in the HH matrix (up to Zr0.66Hf0.34Ni1.03Sn) leads to the simultaneous increase in Seebeck coefficient due to optimization of carrier concentration and increase in electrical conductivity due to increased mobility of carriers. Therefore, an optimized power factor of 35.31 μW K?2 cm?1 at 773 K was obtained for Zr0.66Hf0.34Ni1.03Sn alloy. In addition to this, a reduced lattice thermal conductivity of 1.26 Wm?1 K?1 was optimized for Zr0.66Hf0.34Ni1.1Sn composition at 773 K. Thus, enhanced power factor and reduced thermal conductivity have finally resulted in an increased figure of merit of 0.93 at 773 K for the optimized composition Zr0.66Hf0.34Ni1.03Sn, which is nearly 260% more as compared to the pristine HH composition Zr0.66Hf0.34NiSn.
查看更多>>摘要：Highly efficient oxygen evolution reaction (OER) electrocatalysts have been well developed over the past decades, but their large-scale preparation with good performance-to-cost ratio remains a critical challenge. Here we report a simple one-step fabrication method of catalytic electrode using ultra-fast laser scanning. SEM results demonstrate that the samples have a regular porous array microstructure; XRD shows that Cu2O was formed on the surface of Cu substrate, which is in agreement with the large amount of Cu+ detected from XPS. The as-prepared Cu2O-Cu catalyst exhibits excellent OER activity in 1 M NaOH with an over-potential of 384 mV at the current density of 10 mA cm?2 (without iR compensation). During this process, thin Cu(OH)2 passivation layer could be formed with weak crystallinity, which could be easily removed by reduction reactions using cyclic voltammetry and it has minimum side effect on the OER performance of the sample. This approach is ultra-fast, simple, and environmentally friendly, and thus holds great potential in large-scale practical applications of electrocatalysts.
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