Summary
Lithium‐sulfur (Li‐S) battery based on sulfur cathodes is of great interest because of high capacity and abundant sulfur source. But the shuttling effect of polysulfides caused by ...charge‐discharge process results in low sulfur utilization and poor reversibility. Here, we demonstrate a good approach to improve the utility of sulfur and cycle life by synthesizing carbon nanofibers decorated with MoO2 nanoparticles (MoO2‐CNFs membrane), which plays a role of multiinterlayer inserting between the separator and the cathode for Li‐S battery. The S/MoO2‐CNFs/Li battery showed a discharge capacity of 6.93 mAh cm−2 (1366 mAh g−1) in the first cycle at a current density of 0.42 mA cm−2 and 1006 mAh g−1 over 150 cycles. Moreover, even at the highest current density (8.4 mA cm−2), the battery achieved 865 mAh g−1. The stable electrochemical behaviors of the battery has achieved because of the mesoporous and interconnecting structure of MoO2‐CNFs, proving high effect for ion transfer and electron conductive. Furthermore, this MoO2‐CNFs interlayer could trap the polysulfides through strong polar surface interaction and increases the utilization of sulfur by confining the redox reaction to the cathode.
The molybdenum dioxide‐carbon nanofibers, inserting between the separator and the cathode, are synthesized by the electrospinning method and followed by subsequent thermal treatment, which is used as an interlayer of Lithium‐Sulfur batteries. The enhanced electrochemical performance can be ascribed to its network structure and high electrical conductivity, which facilitates electron‐ion transport and effectively suppresses the shuttle effect.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Fossil fuel resources are decreasing daily. As a renewable energy, biodiesel has been receiving increasing attention because of the relevance it gains from the rising petroleum price and its ...environmental advantages. This review highlights some of the perspectives for the biodiesel industry to thrive as an alternative fuel, while discussing opportunities and challenges of biodiesel. This review is divided in three parts. First overview is given on developments of biodiesel in past and present, especially for the different feedstocks and the conversion technologies of biodiesel industry. More specifically, an overview is given on possible environmental and social impacts associated with biodiesel production, such as food security, land change and water source. Further emphasis is given on the need for government’s incentives and public awareness for the use and benefits of biodiesel, while promoting policies that will not only endorse the industry, but also promote effective land management.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Carbon nanofibers with ferromagnetic metal nanoparticles (CNF-M, M = Fe, Co, and Ni) have been synthesized by carbonizing electrospun polyacrylonitrile nanofibers including metal acetylacetonate in ...an argon atmosphere, and their phase composition, microstructure, magnetic properties and electromagnetic (EM)-wave absorbability have been studied. The microstructure analysis shows that the in situformed metal nanoparticles are well distributed along carbon-based nanofibers and encapsulated by ordered graphite layers. The investigation of magnetic properties and EM-wave absorbability reveals that the as-synthesized CNF-M has typical characteristics of ferromagnetic materials and exhibits excellent EM-wave absorption properties (reflection loss exceeding -20 dB) from the C-band to the Ku-band (4-18 GHz) over an absorber thickness of 1.1-5.0 mm due to the efficient complementarities of complex permeability and permittivity resulting from the magnetic metal nanoparticles and lightweight carbon, as well as the particular particle/graphite core/shell microstructures in CNF-M. Moreover, a minimum reflection loss value of -67.5, -63.1, and -61.0 dB is achieved at 16.6, 12.9, and 13.1 GHz with a matching thickness of 1.3, 1.6, and 1.7 mm for CNF-Fe, CNF-Co, and CNF-Ni, respectively. These magnetic carbon nanofibers are attractive candidates for the new type of high performance EM-wave absorbing materials.
Lithium-sulfur (Li-S) batteries have attracted many attentions due to their high energy density and low-cost. However, the insulation and volume change of sulfur and high solubility of polysulfides ...lead to the fast decay of capacity and short cycle life. In order to solve these issues, we synthesized a novel multifunctional TiO2@C composite nanofibers (TiO2@C CNs) interlayer by electrospinning technique and subsequent heat treatment. It can significantly improve the specific capacity and long cycling stability of Li-S batteries, attributed to the effective restriction of “shuttle effect” and high reutilization of trapped active materials. Using TiO2@C CNs as a multifunctional interlayer, the BP2000/sulfur cathode with a high sulfur content (70 wt %) shows an initial capacity of 852 mAh g−1 at a high current rate of 4C and cycled over 2000 cycles with a fade rate of only 0.028% per cycle. The combination of metal oxides and carbon materials is facile and feasible way to archive high performance Li-S batteries.
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•The TiO2@C CNs was fabricated by electrospinning technique.•The mesoporous structure of TiO2@C CNs was used as the interlayer in Li-S cell.•TiO2@C CNs acts as polysulfide reservoirs to alleviate the shuttle effect.•TiO2@C CNs accelerates the electrochemical reaction kinetic during cycle process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Herein, an intrinsic porous light biomass is utilized as an environmentally friendly precursor to prepare high value-added porous carbon as the interlayer material for advanced lithium sulfur (Li–S) ...batteries. Various material characterization methods are utilized to investigate the obtained porous carbon and found that it exhibits three-dimensional interconnected porous structures with the characteristics of defective graphite structure. Its specific surface calculated by BET method is 300.4 m
2
g
−1
. It can productively curb polysulfide shuttle and boost the cycling performance and rate capability of the battery. The first capacity of Li–S battery with this porous carbon is 905.6 mAh g
−1
at 1 C, and it maintains 464.8 mAh g
−1
even over 500 cycles. More significantly, special microstructures derived from natural growth avoid complicated preparation processes, and it opens up new alternatives for Li–S batteries.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
SrFe12O19 (SFO)/Ni0.5Zn0.5Fe2O4 (NZFO) composite ferrite nanofibers with diameters about 120nm have been prepared by the electrospinning and calcination process. The SFO/NZFO composite ferrites are ...formed after calcined at 700°C for 2h and the composite nanofibers with various mass ratios obtained at 900°C are fabricated from NZFO grains about 16–40nm and SFO grains of 19–45nm with a uniform phase distribution. With the SFO ferrite content increasing, the coercivity (Hc) and remanence (Mr) for the composite ferrite nanofibers initially increase, reaching maximum values of 379.8kA/m (297K) and 242.2kA/m (77K), 39.1Am2/kg (297K) and 53.5Am2/kg (77K), respectively, at a mass ratio (SFO:NZFO) of 4, and then show a reduction tendency with a further increase of the mass ratio. This enhancement in magnetic properties is attributed to the competition of the exchange–coupling interaction and the dipolar interaction in the composite nanofibers.
SrFe12O19 (SFO)/Ni0.5Zn0.5Fe2O4 (NZFO) composite ferrite nanofibers with a uniform phase distribution show competition of the exchange–coupling interaction and the dipolar interaction in the composite nanofibers. Display omitted
► Composite ferrite nanofibers have been prepared by the electrospinning. ► Magnetic exchange–coupling interaction for these nanofibers were analyzed. ► Nanofibers magnetic properties measured at 297K and 77K were discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Here we report a facile approach to synthesize a series of pure Ti4O7 nanostructures via solvothermal process and subsequent thermal treatment. The one-dimensional of Ti4O7 nanorods (1D Ti4O7 NRs) ...and three-dimensional of Ti4O7 nanoparticles (3D Ti4O7 NPs) were successfully achieved and investigated well by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HR-TEM), and Brunauer-Emmett-Teller analysis (BET). The as-prepared Ti4O7 nanostructures were used as additive to prepare Ti4O7/sulfur composite cathodes. The initial discharge capacity of the sulfur cathode with the added Ti4O7 NRs was 1050 mAh g−1, and remaining capacity was 580 mAh g−1 after 300 cycles at 1C. Even at a high current density of 2C, it also kept at a high discharge capacity of 590 mAh g−1. Compared with Ti4O7 NPs/sulfur electrode, the electrodes containing Ti4O7 NRs show the excellent cycling and rate performance, confirming that the morphology of Ti4O7 could effectively influence its electrochemical performance for lithium sulfur batteries. The good electrochemical properties of Ti4O7 NRs can be attributed to the higher catalytic activity in the lithium-sulfur redox reaction, the lower charge-transfer resistance and larger lithium ion diffusion coefficient.
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•1D and 3D nanostructures of electrically-conductive oxide Ti4O7 are constructed as sulfur hosts.•The morphology of Ti4O7 effectively influences its electrochemical performance for Li-S battery.•The Ti4O7 NRs/sulfur keeps a discharge capacity of 580 mAh g−1 after 300 cycles at 1C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Hydrogen (H
) has been considered an ideal alternative energy source for solving energy supply security and greenhouse gas reduction. Although platinum group metal (PGM) catalysts have excellent ...performance in hydrogen electrocatalysis, their scarcity and high cost limit their industrial application. Therefore, it is necessary to develop low-cost and efficient non-PGM catalysts. Transition metal nitrides (TMNs) have attracted much attention because of their excellent catalytic performance in hydrogen electrochemistry, including hydrogen evolution reaction (HER)/hydrogen oxidation reaction (HOR). In this paper, we review and discuss the mechanism of HER/HOR in alkaline media. We compare and evaluate electrocatalytic performance for the HER/HOR TMN catalysts recently reported. Finally, we propose the prospects and research trends in sustainable alkaline hydrogen electrocatalysis.
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► Uniform Co1−xNixFe2O4 nanofibers have been prepared by electrospinning combined with sol–gel process. ► The average diameter of the obtained nanofibers is about 110nm, and the ...length can reach millimeters. ► The structural characteristics and magnetic properties can be conveniently tuned by changing the Co/Ni ratio. ► The coercivity of the nanofibers is superior to that of the corresponding nanoparticle counterparts.
Uniform Co1−xNixFe2O4 (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanofibers with average diameter of 110nm and length up to several millimeters were prepared by calcination of electrospun precursor nanofibers containing polymer and inorganic salts. The as-spun and calcined nanofibers were characterized in detail by TG–DTA, XRD, FE-SEM, TEM, SAED and VSM, respectively. The effect of composition of the nanofibers on the structure and magnetic properties were investigated. The nanofibers are formed through assembling magnetic nanoparticles with poly(vinyl pyrrolidone) as the structure-directing template. The structural characteristics and magnetic properties of the resultant nanofibers vary with chemical composition and can be tuned by adjusting the Co/Ni ratio. Both lattice parameter and particle size decrease gradually with increasing nickel concentration. The saturation magnetization and coercivity lie in the range 29.3–56.4emu/g and 210–1255 Oe, respectively, and both show a monotonously decreasing behavior with the increase in nickel concentration. Such changes in magnetic properties can mainly be attributed to the lower magnetocrystalline anisotropy and the smaller magnetic moment of Ni2+ ions compared to Co2+ ions. Furthermore, the coercivity of Co–Ni ferrite nanofibers is found to be superior to that of the corresponding nanoparticle counterparts, presumably due to their large shape anisotropy. These novel one-dimensional Co–Ni ferrite magnetic nanofibers can potentially be used in micro-/nanoelectronic devices, microwave absorbers and sensing devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
