Copper nanodot-embedded nitrogen and fluorine co-doped porous carbon nanofibers as advanced electrocatalysts for rechargeable zinc-air batteries.

Porous carbon-based electrocatalysts for cathodes in zinc-air batteries (ZABs) are limited by their low catalytic activity and poor electronic conductivity, making it difficult for them to be quickly commercialized. To solve these problems of ZABs, copper nanodot-embedded N, F co-doped porous carbon nanofibers (CuNDs@NFPCNFs) are prepared to enhance the electronic conductivity and catalytic activity in this study. The CuNDs@NFPCNFs exhibit excellent oxygen reduction reaction (ORR) performance based on experimental and density functional theory (DFT) simulation results. The copper nanodots (CuNDs) and N, F co-doped carbon nanofibers (NFPCNFs) synergistically enhance the electrocatalytic activity. The CuNDs in the NFPCNFs also enhance the electronic conductivity to facilitate electron transfer during the ORR. The open porous structure of the NFPCNFs promotes the fast diffusion of dissolved oxygen and the formation of abundant gas-liquid-solid interfaces, leading to enhanced ORR activity. Finally, the CuNDs@NFPCNFs show excellent ORR performance, maintaining 92.5% of the catalytic activity after a long-term ORR test of 20000 s. The CuNDs@NFPCNFs also demonstrate super stable charge-discharge cycling for over 400 h, a high specific capacity of 771.3 mAh g-1 and an excellent power density of 204.9 mW cm-2 as a cathode electrode in ZABs. This work is expected to provide reference and guidance for research on the mechanism of action of metal nanodot-enhanced carbon materials for ORR electrocatalyst design.

Novel colorimetric membranes based on polylactic acid-grafted-citrated methacrylated urethane (PLA-CMU) to monitor cod freshness.

Halochromic agent is easy to fall off from the surface of colorimetric membranes during fish freshness monitoring, which would decay the test accuracy. In order to increase its anchoring, citrated methacrylated urethane (CMU) synthesized by using tributyl citrate, ß-hydroxyethyl methacrylate and diphenyl-methane-diisocyanate as a halochromic agent was grafted on polylactic acid (PLA). The CMU grafted PLA (PLA-CMU) together with tetrabutylammonium chloride (TBAC) prepared colorimetric membranes via electrospinning. 1H NMR and FTIR analysis showed successful bonding between CMU and PLA, and PLA-CMU grafting efficiency reached to the maximum value of 11.15%. Moreover, DSC confirmed that PLA-CMU existed low cold-crystallization temperature due to the excellent compatibility of CMU with PLA, which enhanced the anchoring of CMU effectively. Nanofiber-based PLA-CMU/TBAC colorimetric membrane enhanced the probability of molecules being captured due to its porous structure and large specific surface area. In addition, the increase in hydrophilicity of the membrane can provide a microenvironment for liquid phase reaction, exhibiting obvious color-changing sensitivity during cod freshness monitoring, from white color to light orange or pink with the deterioration of cod at 25 °C and 4 °C respectively. The results demonstrate PLA-CMU/TBAC colorimetric membranes would provide a simple and promising strategy for monitoring fish freshness.

Controlled Design of a Robust Hierarchically Porous and Hollow Carbon Fiber Textile for High-Performance Freestanding Electrodes.

For most carbon-based materials, hierarchical porous structure including well-defined macropores, mesopores, and micropores is commonly seen in 3D aerogels, monoliths, or some carbothermic natural biomass. However, because of the filiform character and long draw ratio, it is difficult to achieve such pore network as well as attain excellent mechanical performance in a 1D single carbon fiber system. To address this issue, an innovative hierarchical porous and hollow carbon textile (HPHCT) is developed via the "dynamic template (KOH, SiO2, and Al2O3) calcination" strategy. Unlike conventional one-step activated carbonized fiber simply with meso or micropores, the fabricated textile generates honeycomb-like macropores uniformly spreading on fiber surface. More importantly, the ultra-lightweight yet flexible HPHCT is mechanically robust, superior to ordinary carbonized one. In addition, it delivers high capacitance of maximum 220 F g-1 as well as keeping long term stability with 100% retention after 10 000 cycles as freestanding electrodes in supercapacitor. Meanwhile, the all-solid integrated symmetric HPHCT supercapacitors demonstrates its high potential in powering electronics for wearable energy storage application.

A Hydrothermal-Assisted Ball Milling Approach for Scalable Production of High-Quality Functionalized MoS2 Nanosheets for Polymer Nanocomposites.

The most known analogue of graphene, molybdenum disulfide (MoS2) nanosheet, has recently captured great interest because it can present properties beyond graphene in several high technological applications. Nonetheless, the lack of a feasible, sustainable, and scalable approach, in which synthesizing and functionalization of 2H-MoS2 nanosheets occur simultaneously, is still a challenge. Herein, a hydrothermal treatment has been utilised to reduce the effect of breaking mechanisms on the lateral size of produced nanosheets during the ball milling process. It was demonstrated that the hydrothermal pre-treatment led to the initial intercalation of an organic molecule such as 4,4'-diaminodiphenyl sulfone (DDS) within the stacked MoS2 sheets. Such a phenomenon can promote the horizontal shear forces and cause sliding and peeling mechanisms to be the dominated ones during low energy ball milling. Such combined methods can result in the production of 2H functionalized MoS2 nanosheets. The resultant few layers showed an average lateral dimension of more than 640 nm with the thickness as low as 6 nm and a surface area as high as 121.8 m2/g. These features of the synthesised MoS2 nanosheets, alongside their functional groups, can result in fully harnessing the reinforcing potential of MoS2 nanosheets for improvement of mechanical properties in different types of polymeric matrices.

Designing of a Phosphorus, Nitrogen, and Sulfur Three-Flame Retardant Applied in a Gel Poly-m-phenyleneisophthalamide Nanofiber Membrane for Advanced Safety Lithium-Sulfur Batteries.

Based on the urgent demand of non-flammable electrospun nanofiber separators and the strong adsorption to polysulfides through chemical doping in separators for Li-S cell, in this study, a phosphorus, nitrogen, and sulfur three-flame retardant (di-(2-(5,5-dimethyl-2-sulfido-1,3,2-dioxaphosphinan-2-yl)hydrazineyl)-P-ethylphosphinic) was synthesized and a high-performance flame-retarding poly-m-phenyleneisophthalamide (PMIA) membrane was successfully prepared through blend electrospinning with the flame retardant, it is regarded as a promising gel nanofiber membrane with advanced safety for the lithium-sulfur (Li-S) cell, and it was systematically explored and analyzed. It was presented that the modified PMIA electrospun membrane with the synthesized flame retardant possessed excellent flame retardation, outstanding thermal stability, and good mechanical strength. Meanwhile, the prepared membrane showed extraordinarily high uptake and preserving retention of the liquid electrolyte and enhanced ionic conductivity. More importantly, the assembled Li-S cells using the obtained membrane exhibited excellent cycling retention and outstanding rate capability because of its fast ion transportation and good interfacial compatibility. The assembled batteries with the novel membrane exhibited a high first-cycle discharge capacity of 1121.50 mA h g-1, superior discharge capacity retention of 713.41 mA h g-1, and high Coulombic efficiency of 98.46% after 600 cycles at the 0.5 C rate. In addition, the limiting oxygen index of the obtained nanofiber membrane with flame retardancy was as high as ∼30.0%, which could greatly enhance the safety of the electrospun nanofiber separator. The excellent electrochemical performances and safety for the battery assembled with the prepared gel PMIA nanofiber membrane were attributed to the significantly prevented "shuttle effect" of lithium polysulfides based on the physical capturing of lithium polysulfides through the obtained jelly-like gel state and chemical binding of polysulfide intermediates through the tridoped phosphorus, nitrogen, and sulfur elements in the PMIA and the flame retardant. All of these excellent properties will promote the great development of the Li-S battery with high performance and satisfactory safety.

Lightweight, Superelastic Yet Thermoconductive Boron Nitride Nanocomposite Aerogel for Thermal Energy Regulation.

Conventional three-dimensional (3D) thermal conductors or heat sinks are normally bulky solids with high density, which is cumbersome and not portable to satisfy current demands for soft and flexible electronic devices. To address this issue, here, a lightweight, superelastic yet thermally conductive boron nitride (BN) nanocomposite aerogel is designed by a facile freeze-drying method. The attained aerogel constituting of tailored interconnected binary inorganic-organic network structure exhibits low bulk density (6.5 mg cm-3) and outstanding mechanical performances for compression, clotting, and stretching. Meanwhile, the aerogel has promising thermal stability and high thermal conductivity over wide temperature ranges (30-300 °C), validating the application even in extremely hot environments. Moreover, the aerogel can serve as a lightweight and elastic heat conductor for the enhancement of thermal energy harvest. Interestingly, during alternate strain loading/unloading under heating, the superelasticity and the anisotropy of thermal conductive transduction make the aerogel enable the elastic thermal energy capture and dynamic regulation. Therefore, our findings provide a potential use for the thermally conductive aerogel in future green energy applications.

On the detection of carbon fibre storage contamination and its effect on the fibre-matrix interface.

Contamination caused by inappropriate carbon fibre (CF) storage may have an impact on their end use in reinforced composite materials. Due to the chemical complexity of CFs it is not easy to detect potential contaminants, especially at the early stage during manufacturing and handling. In this paper, X-ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared (FTIR) spectroscopy and Surface Energy Analysis (IGC-SEA) were used to assess the surfaces of CFs stored in polyolefin zip-lock bags for possible contamination. Only after over 2 months in-bag storage, was XPS capable of detecting a minor increase in nitrogen on the CF surface while FTIR revealed the presence of fatty acid amides and fatty acids, both associated with the storage media. However neither of these techniques were sensitive enough to show significant evolution of the amount of contamination as a function of storage time. In contrast, IGC-SEA distinguished surface energy differences between CFs before and after storage. These differences were found to change as a function of storage time, which were attributed to increases in contamination amounts. Single fibre fragmentation tests indicated that the surface contamination had potential to disrupt the fibre-matrix interface. These findings provide a new method for assessing the surface contamination of CFs with potential application to other materials.

High temperature thermally conductive nanocomposite textile by "green" electrospinning.

Recently, thermally regulating textiles have attracted wide interest owing to their ability to realize personal cooling and provide thermal comfort. However, most of the thermally conductive textiles cannot afford higher temperatures (>200 °C), which restricts their further applications in aviation, fire extinguishing or military requiring high temperature heat spreaders. Here, we report a high temperature thermally conductive nanocomposite textile consisting of amino functional boron nitride (FBN) nanosheets and polyimide (PI) nanofibers. Notably, the textile is "green" electrospun from aqueous solution without any toxic organic solvents, which is facile, economical and environmently friendly. Moreover, both FBN and the precursor of PI are modified to be water soluble and exhibit good compatibility in the spinning solution even under high concentrations. The "green" method obtained FBN-PI textile shows high thermal conductivity (13.1 W m-1 K-1) at a high temperature (300 °C), filling in the gap of thermally conductive polymer nanocomposite fibers for high temperature thermal regulation. Furthermore, it also provides efficient cooling capability as a thermal spreader. The good performance is ascribed to the weaving of the aligned FBN filament in a thermally stable PI fiber, which constructs an effective thermally conductive network. In addition, the nanocomposite textile is light weight, soft and hydrophobic, which is promising for electronic packaging or space suits for special high temperature thermal management.

CeF3-Doped Porous Carbon Nanofibers as Sulfur Immobilizers in Cathode Material for High-Performance Lithium-Sulfur Batteries.

In this study, the CeF3-doped porous carbon nanofibers (PCNFs), prepared via electroblown spinning technique and carbonization process, are used as sulfur immobilizers in cathodes for lithium-sulfur (Li-S) batteries for the first time. The cathode composed of CeF3-doped PCNFs, carbon nanotubes (CNTs), and S is successfully prepared through the ball-milling and heating method. The formed porous structure in the PCNFs and CNTs facilitates the construction of highly electrically conductive pathways and effectively alleviates volume changes, which can maintain the stability of the cathode structure and make them in close contact between the electrodes. Meanwhile, the intermediate polysulfide dissolved and lost in the electrolyte can also be suppressed because of the hierarchical porous carbon nanofibers and CeF3. The Li-S battery using the cathode can display excellent electrochemical properties and stable capacity retention, presenting an initial discharge capacity of 1395.0 mAh g-1 and retaining a capacity of 901.2 mAh g-1 after 500 cycles at 0.5C. During the rate capability tests of battery, the discharge capacity of Li-S battery with the electrode slowed down from the discharge capacity of 1284.6 mAh g-1 at 0.5C to 1038.6 mAh g-1 at 1C and 819.3 mAh g-1 at 2C, respectively. It is noteworthy that the battery can still endow an outstanding discharge capacity of 1269.73 mAh g-1 with a high retention of 99.2% when the current density returns to 0.5C.

A review of recent developments in rechargeable lithium-sulfur batteries.

The research and development of advanced energy-storage systems must meet a large number of requirements, including high energy density, natural abundance of the raw material, low cost and environmental friendliness, and particularly reasonable safety. As the demands of high-performance batteries are continuously increasing, with large-scale energy storage systems and electric mobility equipment, lithium-sulfur batteries have become an attractive candidate for the new generation of high-performance batteries due to their high theoretical capacity (1675 mA h g-1) and energy density (2600 Wh kg-1). However, rapid capacity attenuation with poor cycle and rate performances make the batteries far from ideal with respect to real commercial applications. Outstanding breakthroughs and achievements have been made to alleviate these problems in the past ten years. This paper presents an overview of recent advances in lithium-sulfur battery research. We cover the research and development to date on various components of lithium-sulfur batteries, including cathodes, binders, separators, electrolytes, anodes, collectors, and some novel cell configurations. The current trends in materials selection for batteries are reviewed and various choices of cathode, binder, electrolyte, separator, anode, and collector materials are discussed. The current challenges associated with the use of batteries and their materials selection are listed and future perspectives for this class of battery are also discussed.