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We have established a novel and solvent-free synthesis of superior performance Sn/C anode derived from binary metal oxides which initiated the outward growth of ZIF-8 approach. The obtained anode has highly dispersed Sn nanoparticles wrapped in nitrogen-rich carbon with a 3D continuous conductive framework and a high Sn content of 82.3wt% Binary metal oxide (ZnSnO3) is chosen together with imidazole to direct ZIF-8 growing around tin oxides according to the theory of hard and soft acids and bases. This ensures an encapsulation of tin oxides with high dispersion into ZIF-8. Subsequent pyrolysis allows the outward growth of ZIF-8 convert into a continuous and nitrogen-rich (5.3wt%) carbon network with good conductivity. Meanwhile, tin oxides are reduced to Sn nanoparticles by carbothermal reduction and the reduced zinc consequently evaporates to create open pores which contribute to fast transportation of lithium-ions and electrons. Consequently, the Sn/C anode presents an initial discharge capacity of 1321mAhg−1 with superior coulombic efficiency of 80.1% at 0.2Ag−1. Reversible capacities of 901mAhg−1 at 0.2Ag−1 and 690mAhg−1 at 1Ag−1 are reserved after 150 cycles. Importantly, this designed synthesis suggests a new approach to produce other materials such as MnO/C anode exhibiting good performance.
Two types of double-layer capacitors, based on carbon materials, were analysed: (1) an imaginary nano-capacitor assembled from single graphene sheets, separated by electrolyte layers (thickness of nanometers) and (2) a capacitor based on porous carbons. It has been shown that the maximum specific surface of a porous carbon material which may be used for the construction of a capacitor is ca. 2600m2 g−1. The maximum energy density of an imaginary double-layer ‘nano-capacitor’, is close to 10kJkg−1 at a voltage of U =1V (aqueous electrolyte) of ca. 40–45kJkg−1 at U ≈2.3–2.5V (organic electrolytes), and at the order of 100kJkg−1 at voltages close to 4V (ionic liquids as electrolytes). The real device consists of porous electrodes and a separator, both soaked with the electrolyte, as well as current collectors. Consequently, the maximum electric capacity expressed versus the mass of the device (ca. 20–30Fg−1), is much smaller than the corresponding value expressed versus the mass of the carbon material (ca. 300Fg−1). In order to obtain the energy density of the device at a level of 100kJkg−1 (characteristic for the lead-acid battery), the capacitor with porous carbon electrodes should operate at voltages of ca. 4V (ionic liquids as electrolytes). However, the specific power density of such a capacitor having an acceptable energy density (ca. 100kJkg−1) is relatively low (ca. 1kWkg−1).
This paper summarises the safety assessments of eleven smoke flavouring primary products evaluated by the European Food Safety Authority (EFSA). Data on chemical composition, content of polyaromatic hydrocarbons and results of genotoxicity tests and subchronic toxicity studies are presented and discussed. The smoke flavourings vary in their contents of identified constituents; none of them exceeded the legal limit for benzo[a]pyrene and benzo[a]anthracene. Ten smoke flavourings proved not to be genotoxic in vivo, whereas this could not be ruled out for another smoke flavouring. Results from animal testing and proposed dietary exposure indicate that only three smoke flavourings would not be of safety concern for humans.
Rechargeable aluminum-ion batteries (RAIBs) are regarded as the next generation of low-cost and high-capacity electrical energy storage systems. Compared to graphene-based cathodes, metal dichalcogenide cathodes can potentially provide RAIBs with higher capacities. However, metal dichalcogenides suffer from poor cycling performance, hindering the further development of high-capacity RAIBs. Thus, to further improve the performance of RAIBs, it is imperative to gain a deep understanding of the mechanisms behind the energy-storage and capacity-deterioration characteristics of these materials. In this work, we conducted detailed characterization to acquire a deep understanding of the energy storage mechanism of a CoSe2-based cathode. The characterization results revealed that energy storage involved incorporation of Al3+ into CoSe2 to generate AlmConSe2 (i.e., partial substitution of Co2+ by Al3+) and elemental Co, while capacity deterioration resulted from the dissolution of active cobalt species into the electrolyte and the pulverization of the CoSe2 phase. The understanding of the capacity-deterioration mechanism allowed us to design a two-step concept for a new type of RAIB composite cathode material. Thus, we employed a conductive wrapping layer of reduced graphene oxide (rGO) to protect CoSe2/carbon nanodice composites from cobalt dissolution and CoSe2 pulverization while also improving the conductivity of the materials. This novel design resulted in a CoSe2/carbon nanodice@rGO composite material with an outstanding cycling performance (after 500 cycles) of 143 mA h g−1 at 1000 mA g−1, which is one of the best performances for a metal-based RAIB cathode material reported to date. These findings are of great significance for the further development of high-capacity RAIBs.
Electrochemical deposition of magnesium (Mg) has been successfully achieved from an ionic liquid (IL) solution based on quaternary ammonium salt containing lithium (Li) salt. Irreversible electrochemical behavior was generally observed in the IL-based electrolytes containing simple Mg salt. In the IL-based electrolyte dissolving both Mg and Li salts, electrochemical reduction and oxidation of magnesium cation (Mg2+) have become detectable. Such reversible processes correspond respectively to cathodic deposition and anodic dissolution of metallic Mg, which are accompanied by the co-deposition/co-dissolution of Li. Potentiostatic electrolysis of IL dissolving binary Mg and Li salts gave metallic deposit consisting of both elements with total current efficiency of ca. 52%.
In this work flexible composite nanogenerators were prepared aiming to identify and optimize the exploitation of the piezoelectric effect in mechanical energy harvesting. A novel shape-controlled synthesis of ZnO microstructures through hydrothermal route was achieved resulting in different morphologies and aspect-ratio particles, microwires, multipods, and desert-roses. The three different microparticles and round-shaped commercial nanoparticles were incorporated into a polydimethylsiloxane matrix and a comparative study on the piezoelectric output power dependence on the filler morphology was carried out. The highest performances, i.e. output voltage of 10V and a maximum power of 55µW, were obtained with the highest aspect-ratio ZnO filler, the microwires, dispersed in the PDMS matrix at a 40wt% concentration. Considering the generated voltage dependence on the size and aspect-ratio of the fillers, a working mechanism was formulated. The nanogenerators were then exploited to charge a homemade carbon-based supercapacitor. The voltage charging curves confirm the voltage generation trend based on the high aspect-ratio particles, showing that the best performances are obtained by the microwires-based composite nanogenerator. This work thus contributes to clarify the piezoelectric mechanism in composite nanogenerators and to maximize the output power generation in view of self-powered nanodevices able to recover and store waste environmental energy.
Composites Li[Li x Ni0.34−x Mn0.47Co0.19]O2 (0.18≤ x ≤0.21) were prepared by a solid state reaction method assisted with co-precipitating. The chemical composition, structure, morphology, and specific surface area of as-prepared composites were systematically characterized by ICP, XRD, SEM, and BET, respectively. The electrochemical performances of the composites were evaluated as high-voltage cathode for lithium-ion batteries. Among all the composites, sample SN exhibited a best electrochemical performance. Except for the initial decay, no obvious capacity fading was observed after cycling 30 cycles at different rates. The discharge capacities were maintained steadily as the current density increased up to 500mAg−1. The improved electrochemical performance of sample SN was attributed to the compromise effect between the increased Li2MnO3 phase and the enhanced Li/Ni disorder.
The effect of reduction conditions on a Pt28Ni36Cr36/C catalyst was investigated by using two different reduction methods: hydrogen reduction and NaBH4 reduction. In hydrogen reduced catalysts, dissolution of metallic Ni and Cr was observed during cyclic voltammetry (CV) tests, and a larger amount of Ni and Cr was dissolved when reduced at higher temperatures. For methanol electro-oxidation, the highest specific current density of 1.70Am−2 at 600s of the chronoamperometry tests was observed in the catalyst reduced at 300°C, which was ∼24 times that of a Pt/C catalyst (0.0685Am−2). In NaBH4 reduced catalysts, formation of an amorphous phase and a more Pt-rich surface was observed in X-ray diffraction and CV results, respectively, with increasing amounts of NaBH4. When reduced by 50 times of the stoichiometric amount of NaBH4, the PtNiCr/C catalyst (PtNiCr-50t) showed a current density of 34.1Agnoble metal −1, which was 81% higher than the 18.8Agnoble metal −1 value of a PtRu/C catalyst at 600s of the chronoamperometry tests. After 13h of chronoamperometry testing, the activity of the PtNiCr-50t (15.0Agnoble metal −1) was 110% higher than the PtRu/C catalyst (7.15Agnoble metal −1). The PtNiCr/C catalyst shows promise as a Ru-free methanol oxidation catalyst.
A novel water-dispersible polyaniline (PANI)/graphene composite was prepared by the in situ polymerization of aniline on the surface of poly(styrenesulfonic acid) (PSS) coated graphene nanosheets (PSS-GR). The characterization of atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy confirmed the successful synthesis of PANI/PSS-GR composites and strong interaction between PANI and PSS-GR. The as-synthesized PANI/PSS-GR composite is readily dispersible in water and forms a homogeneous aqueous dispersion which is stable for more than one month. More interestingly, PSS-GR can dope PANI effectively and shift its electroactivity to a neutral or even alkaline environment, making them promising candidates for biological application. In addition, the PANI/PSS-GR composite shows improved electrical conductivity and electrochemical stability compared to the neat polyaniline. Furthermore, the potential use of this composite for detection of ascorbic acid (AA) was investigated. A low detection limit of 5×10−6 M and a linear detection range between 1×10−4 M and 1×10−3 M was attained, indicating the high electrocatalytic ability of this composite. Anticipatedly, the synthesized composite will find promising applications as a novel electrode material in sensors and other devices in virtue of their outstanding characteristics of water-dispersibility, good cycle stability, electroactivity in neutral solution and excellent electrocatalytic ability.
Immunosenescence contributes to cognitive impairment and neurodegeneration, and those conditions could be attenuated by non-pharmacological anti-inflammatory strategies, such as exercise and supplementation with the amino acid taurine. Since taurine body content decreases with aging, we investigated the effects of supplementation (alone and combined with exercise) on oxidative stress, extracellular matrix degradation, white blood cells, neurotrophins, cognition and physical fitness of elderly women. Forty-eight women (83.58 ± 6.98 years) were enrolled into exercise training only (EO: n = 13), taurine supplementation (TS: n = 12), exercise training + taurine supplementation (ETTS: n = 11), and control group (CG: n = 12). All interventions lasted 14 weeks. Exercise was applied twice a week, and taurine was given once a day (1.5 g). Data collection occurred before and after interventions with the determination of myeloperoxidase (MPO), matrix metalloproteinase-9 (MMP-9), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF) levels, and white blood cell counts (WBC). Montreal cognitive assessment (MoCA) and physical fitness tests were also evaluated. Concentration of MPO and MMP-9 decreased after intervention in TS (p < 0.05). No effect of time or time × group was observed for WBC parameters; however, univariate analysis showed a significant decrease in lymphocytes for TS, while an increase in monocytes occurred in the CG (p < 0.05). MoCA scores decreased over time in the CG (p < 0.05). Improvements in physical fitness occurred in ETTS (better agility and aerobic capacity), mostly likely due to exercise and boosted by taurine supplementation. No changes in BDNF levels were observed (p > 0.05), while NGF concentration were undetectable in almost subjects. Exercise together with taurine supplementation appears to be a valuable strategy to enhance health-related outcomes in older persons.
Attempts to utilise LiCoO2 as the cathode when the electrolyte is based on an ionic liquid, e.g. 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, have been severely limited by significant capacity fade. Given that some form of instability of this material in ionic liquids is widely suspected as the principal cause, the aim of the current work is to determine the efficacy of using the scanning electrochemical microscope (SECM), to detect solubilisation of species leaving the LiCoO2 electrode during charging and/or discharging. The SECM microelectrode probe tip was lowered to within 10–20μm of the platinum substrate electrode, onto which solid LiCoO2 had been coated. This substrate material was charged and discharged to different voltages, whilst probing any solubilised species at the microelectrode tip. The detection of solubilised Co2+ and oxygen during over-charge and more so under deep discharge was observed. Possible mechanisms for degradation of the electrode are proposed. From these preliminary results, strategies are suggested for mitigating the degradation of LiCoO2 when used in a room temperature ionic liquid electrolyte.
Résumé Introduction L’objectif de ce travail est d’établir des normes diagnostiques pour les tests de la batterie RAPID, dans la détection des troubles cognitifs liés à la maladie d’Alzheimer. Population et méthodes L’échantillon comprenait 352 sujets témoins (MMSE moyen : 27,3±2,5) et 676 patients atteints de maladie d’Alzheimer (MMSE moyen : 22,9±2,6) répartis selon trois classes d’âge (60–69ans, 70–79ans, 80–89ans) et trois niveaux scolaires. Des valeurs seuil « optimales » et « spécifiques », ajustées selon l’âge et le niveau scolaire, ont été calculées afin d’évaluer le pouvoir discriminant de chaque test de la batterie RAPID. Résultats Le RL/RI-16 explorant les fonctions mnésiques possédait une bonne sensibilité (de 87 % à 100 % pour le rappel libre et de 85 % à 98 % pour le rappel total) et spécificité (de 85 % à 96 % pour le rappel libre et de 86 % à 100 % pour le rappel total), quels que soient l’âge et le niveau scolaire. Pour l’épreuve d’appariement catégoriel, les sensibilités étaient faibles. Conclusion L’utilisation de ces deux types de valeurs seuil apporte au clinicien une aide au diagnostic de la maladie d’Alzheimer en fonction du contexte clinique, permettant de limiter les risques de faux positifs et de faux négatifs.
Here an Li ion conductive oxysulfide of LiSnOS with a layered structure, grown from a layered SnOS phase by reacting with different amounts of LiNO3 to form the Li-ion intercalation compound, is developed in order to find the best LiSnOS with the highest Li ion conductivity for assembling a totally solid LiCoO2/(LiSnOS + gel polymer)/Li lithium ion battery (LIB). With this approach, there is no need for utilizing the moisture-sensitive Li2S precursor. The variations of crystal parameter, morphology, and Li ion conductivity of LiSnOS with the Li/Sn precursor ratio are investigated in terms of its composition and lattice defect. The LiSnOS with the Li/Sn molar ratio of 2 or LiSnOS-2 is expected to have the Li vacancy-free Li[Li1/3Sn2/3(O,S)2] or Li2Sn(O,S)3 layered structure and show the highest Li ion conductivity of 1.92 × 10−4 S cm−1. The hybrid electrolytes with different amounts of LiSnOS-2 in poly(vinylidene fluoride-hexafluoropropylene) or PVDF-HFP gel are studied. The battery with the 30 wt% LiSnOS-2/70% gel electrolyte performs the enhanced discharge capacity of 134.6 mA h g−1 and behaves well for the 30 charge-discharge cycles. A schematic mechanism in terms of the LiSnOS content in gel electrolyte is proposed to explain the performance enhancement of LIB.
In this paper, aqueous solution of reduced graphene oxide has been prepared assisted by the graphene quantum dot, which is then mixed with aqueous polyaniline solution to form water-borne reduced graphene oxide/polyaniline composite powder. The resultant graphene quantum dot-reduced graphene oxide/polyaniline shows a specific morphology of nanosized polyaniline firmly attached on reduced graphene oxide layer, due to the good dispersion of reduced graphene oxide and polyaniline in water. The monodispersion leads to the close contact between reduced graphene oxide sheets and polyaniline particles, significantly depressing the accumulation. It leads to the enhanced conductivity, supercapacitance and cycling stability for graphene quantum dot-reduced graphene oxide/polyaniline, with capacitance as high as 648 F g−1. After 5000 charge-discharge cycles, the capacitance of as-prepared reduced graphene oxide/polyaniline composite shows just 3.7% decay while it reaches 68% for polyaniline. Furthermore, driven by the strong electrostatic forces between the electropositive polyaniline and the electronegative graphene quantum dot-reduced graphene oxide as well as the π−π interactions, the obtained nanosized graphene quantum dot-reduced graphene oxide/polyaniline films from the controllable layer-by-layer method show the morphology of interconnected-layer networks and exhibit good electrochemical activity on H2O2 in the range of 5.0 × 10−7–3.5 × 10−5 M. The detection limit is as low as 1.1 μM.
In recent years, surface engineering has acquired a greater importance in the field of materials technology, particularly in aerospace, automotive, bio-medical and engineering applications. Surface engineering enables enhancing the performance of the materials at an affordable cost to induce functional properties, which otherwise cannot be provided by the substrate material. The degradation of materials properties due to wear and corrosion is estimated to be very high. Since surface engineering can increase the performance of the given materials at a reduced cost, it has enormous potential for providing technological solutions to various engineering problems. Conventionally, several wet-chemical and spray-based processes have been used for the surface modification of engineering materials. These include: electroplating, electroless plating, anodization and various other electrochemical processes, and organic paint coatings. However, environmental issues demand the development of cost-effective eco-friendly surface modification processes. Towards this, in recent times, a lot of superior process techniques such as: chemical vapor deposition, physical vapor deposition, thermal spray, diffusion processes, sol–gel, etc. have been developed. In spite of this, there is still great scope for research in establishing a relationship between the process parameters of the used surface engineering processes and the resulting properties of the modified surface. Further, recent developments in surface engineering using nanostructured coatings/nano-surfaces are expected to carve a niche in many industrial applications. Nevertheless, there is an urgent need to fill the gaps between the research done at the lab level and the plethora of problems faced by the industry. In this article, some of these issues will be addressed with emphasis to the aerospace, automotive and engineering sectors. A glimpse of futuristic surface modification technologies will also be presented, in brief, which will enable in providing cost-effective solutions to a variety of industrial problems.
Large-scale energy storage represents a key challenge for renewable energy and new systems with low cost, high energy density and long cycle life are desired. In this article, we develop a new lithium/polysulfide (Li/PS) semi-liquid battery for large-scale energy storage, with lithium polysulfide (Li2S8) in ether solvent as a catholyte and metallic lithium as an anode. Unlike previous work on Li/S batteries with discharge products such as solid state Li2S2 and Li2S, the catholyte is designed to cycle only in the range between sulfur and Li2S4. Consequently all detrimental effects due to the formation and volume expansion of solid Li2S2/Li2S are avoided. This novel strategy results in excellent cycle life and compatibility with flow battery design. The proof-of-concept Li/PS battery could reach a high energy density of 170 W h kg−1 and 190 W h L−1 for large scale storage at the solubility limit, while keeping the advantages of hybrid flow batteries. We demonstrated that, with a 5 M Li2S8 catholyte, energy densities of 97 W h kg−1 and 108 W h L−1 can be achieved. As the lithium surface is well passivated by LiNO3 additive in ether solvent, internal shuttle effect is largely eliminated and thus excellent performance over 2000 cycles is achieved with a constant capacity of 200 mA h g−1. This new system can operate without the expensive ion-selective membrane, and it is attractive for large-scale energy storage.
Lithium-sulfur (Li-S) batteries are technologically significant for sulfur is cheap, and offers high gravimetric capacity and a large energy density. But achieving long term cyclability with moderate capacity loss, and scalability pose formidable challenges. A solution phase approach for the preparation of a composite of sulfur with hydroxyl groups functionalized multiwalled carbon nanotubes (MWCNTols) and coated with poly(3,4-ethylenedioxypyrrole) (PEDOP) is presented for the first time. Comparison of the Li-S performances at 0.1 C current-rate show that the S based cell with a S-loading of 80% retains a low capacity of 122 mAh gsulfur −1 after 100 cycles, whereas cells with S/MWCNTols and S/MWCNTols/PEDOP composites with sulfur loadings of 73 and 70% respectively, retain capacities of 384 and 624 mAh gsulfur −1 after 200 charge-discharge cycles, with Coulombic efficiencies of 96 and 98.7% respectively. This performance differential illustrates the role of PEDOP in inhibiting sulfur loss and in maximizing cell response. The polymer provides electrical interconnects between the insulating sulfur clusters and facilitates Li+ transfer at the interface. The ease of the synthesis, coupled with the remarkable cycling performance delivered by this composite at a high sulfur-loading, demonstrate the promise that this S/CNT/conducting polymer composite has for practical Li-S batteries.