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1.
Nanomaterials (Basel) ; 9(7)2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31295969

RESUMO

The spherical-graphite/Fe3O4 composite has been successfully fabricated by a simple two-step synthesis strategy. The oxygenous functional groups between spherical-graphite and Fe3O4 benefit the loading of hollow Fe3O4 nanospheres. All of the composites as anodes for half cells show higher lithium storage capacities and better rate performances in comparison with spherical-graphite. The composite containing 39 wt% of hollow Fe3O4 nanospheres exhibits a high reversible capacity of 806 mAh g-1 up to 200 cycles at 0.5 A g-1. When cycled at a higher current density of 2 A g-1, a high charge capacity of 510 mAh g-1 can be sustained, even after 1000 long cycles. Meanwhile, its electrochemical performance for full cells was investigated. When matching with LiCoO2 cathode, its specific capacity can remain at 137 mAh g-1 after 100 cycles. The outstanding lithium storage performance of the spherical-graphite/Fe3O4 composite may depend on the surface modification of high capacity hollow Fe3O4 nanospheres. This work indicates that the spherical-graphite/Fe3O4 composite is one kind of prospective anode material in future energy storage fields.

2.
Angew Chem Int Ed Engl ; 57(29): 8865-8870, 2018 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-29859011

RESUMO

Classical organic anode materials for Na-ion batteries are mostly based on conjugated carboxylate compounds, which can stabilize added electrons by the double-bond reformation mechanism. Now, 1,4-cyclohexanedicarboxylic acid (C8 H12 O4 , CHDA) with a non-conjugated ring (-C6 H10 -) connected with carboxylates is shown to undergo electrochemical reactions with two Na ions, delivering a high charge specific capacity of 284 mA h g-1 (249 mA h g-1 after 100 cycles), and good rate performance. First-principles calculations indicate that hydrogen-transfer-mediated orbital conversion from antibonding π* to bonding σ stabilize two added electrons, and reactive intermediate with unpaired electron is suppressed by localization of σ-bonds and steric hindrance. An advantage of CHDA as an anode material is good reversibility and relatively constant voltage. A large variety of organic non-conjugated compounds are predicted to be promising anode materials for sodium-ion batteries.

3.
Polymers (Basel) ; 10(10)2018 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-30961077

RESUMO

The exploration of multifunctional electrode materials has been a hotspot for the development of high-performance supercapacitors. We have used carbon fiber plates recovered from construction waste to prepare high-quality flexible carbon fiber materials by pyrolysis of epoxy resin. The as-prepared recycled carbon fiber has a diameter of 8 µm and is the perfect substrate material for flexible electrode materials. Furthermore, polyaniline and manganese dioxide are uniformly deposited on the recycled carbon fiber by one-step electrodeposition to form an active film. The recycled carbon fiber/polyaniline/MnO2 composite shows an excellent specific capacitance of 475.1 F·g-1 and capacitance retention of 86.1% after 5000 GCD cycles at 1 A·g-1 in 1 M Na2SO4 electrolyte. The composites optimized for electrodeposition time have more electroactive sites, faster ions and electron transfer, structural stability and higher conductivity, endowing the composites promising application prospect.

4.
ACS Appl Mater Interfaces ; 10(3): 2496-2503, 2018 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-29285932

RESUMO

Even though many organic cathodes have been developed and have made a significant improvement in energy density and reversibility, some organic materials always generate relatively low voltage and limited discharge capacity because their energy storage mechanism is solely based on redox reactions of limited functional groups [N-O, C═X (X = O, N, S)] linking to aromatic rings. Here, a series of cyclooctatetraene-based (C8H8) organic molecules were demonstrated to have electrochemical activity of high-capacity and high-voltage from carbon rings by means of first-principles calculations and electronic structure analysis. Fused molecules of C8-C4-C8 (C16H12) and C8-C4-C8-C4-C8 (C24H16) contain, respectively, four and eight electron-deficient carbons, generating high-capacity by their multiple redox reactions. Our sodiation calculations predict that C16H12 and C24H16 exhibit discharge capacities of 525.3 and 357.2 mA h g-1 at the voltage change from 3.5 to 1.0 V and 3.7 to 1.3 V versus Na+/Na, respectively. Electronic structure analysis reveals that the high voltages are attributed to superposed electron stabilization mechanisms, including double-bond reformation and aromatization from carbon rings. High thermodynamic stability of these C24H16-based systems strongly suggests feasibility of experimental realization. The present work provides evidence that cyclooctatetraene-based organic molecules fused with the C4 ring are promising in designing high-capacity and high-voltage organic rechargeable cathodes.

5.
ACS Appl Mater Interfaces ; 6(22): 20025-34, 2014 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-25365660

RESUMO

Through a facile and effective seeding polymerization reaction via a one-step redox/complexation process, which took place in aqueous medium at ambient temperature, silver nanoparticles (Ag NPs) embedded polyaniline nanofiber (PANI NF) networks were synthesized as antibacterial agents. During the reaction, not only NF morphology formation of the resulting conducting polymers (CPs) but also amplification of the aqueous silver nitrate (AgNO3) solutions' oxidative potentials were managed by vanadium pentoxide (V2O5) sol-gel nanofibers, which acted as well-known nanofibrous seeding agents and the auxiliary oxidative agent at the same time. The PANI/Ag nanocomposites were proven to exhibit excellent antibacterial property against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Antibacterial property performance and average life span of the nanocomposite network were optimized through the homogeneous distribution/embedment of Ag NPs within one-dimensional (1-D) PANI NF matrix. The antibacterial efficacy tests and nanocomposite material characterization results further indicated that the sole components of PANI/Ag have a synergistic effect to each other in terms of antibacterial property. Thus, this well-known catalytic seeding approach via a one-step oxidative polymerization reaction can be considered as a general methodology and a substantial fabrication tool to synthesize Ag NP decorated nanofibrillar PANI networks as advanced antibacterial agents.


Assuntos
Compostos de Anilina/química , Antibacterianos/síntese química , Nanopartículas Metálicas/química , Nanocompostos/química , Nanofibras/química , Prata/química , Antibacterianos/química , Antibacterianos/farmacologia , Escherichia coli/efeitos dos fármacos , Oxirredução , Polimerização , Staphylococcus aureus/efeitos dos fármacos , Compostos de Vanádio/química
6.
ACS Appl Mater Interfaces ; 3(2): 135-8, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21268632

RESUMO

Nanoporous thermochromic VO(2) films with low optical constants and tunable thicknesses have been prepared by polymer-assisted deposition. The film porosity and thickness change the interference relationship of light reflected from the film-substrate and the air-film interfaces, strongly influencing the optical properties of these VO(2) films. Our optimized single-layered VO(2) films exhibit high integrated luminous transmittance (T(lum,l) = 43.3%, T(lum,h) = 39.9%) and solar modulation (ΔT(sol) = 14.1%, from T(sol,l) = 42.9% to T(sol,h) = 28.8%), which are comparable to those of five-layered TiO(2)/VO(2)/TiO(2)/VO(2)/TiO(2) films (T(lum,l) = 45%, T(lum,h) = 42% and ΔT(sol) = 12%, from T(sol,l) = 52% to T(sol,h) = 40%, from Phys. Status Solidi A2009, 206, 2155-2160.). Optical calculations suggest that the performance could be further improved by increasing the porosity.

7.
Langmuir ; 26(13): 10738-44, 2010 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-20329789

RESUMO

This paper describes a solution-phase synthesis of high-quality vanadium dioxide thermochromic thin films. The films obtained showed excellent visible transparency and a large change in transmittance at near-infrared (NIR) wavelengths before and after the metal-insulator phase transition (MIPT). For a 59 nm thick single-layer VO(2) thin film, the integral values of visible transmittance (T(int)) for metallic (M) and semiconductive (S) states were 54.1% and 49.1%, respectively, while the NIR switching efficiencies (DeltaT) were as high as 50% at 2000 nm. Thinner films can provide much higher transmittance of visible light, but they suffer from an attenuation of the switching efficiency in the near-infrared region. By varying the film thickness, ultrahigh T(int) values of 75.2% and 75.7% for the M and S states, respectively, were obtained, while the DeltaT at 2000 nm remained high. These results represent the best data for VO(2) to date. Thicker films in an optimized range can give enhanced NIR switching efficiencies and excellent NIR blocking abilities; in a particularly impressive experiment, one film provided near-zero NIR transmittance in the switched state. The thickness-dependent performance suggests that VO(2) will be of great use in the objective-specific applications. The reflectance and emissivity at the wavelength range of 2.5-25 microm before and after the MIPT were dependent on the film thickness; large contrasts were observed for relatively thick films. This work also showed that the MIPT temperature can be reduced simply by selecting the annealing temperature that induces local nonstoichiometry; a MIPT temperature as low as 42.7 degrees C was obtained by annealing the film at 440 degrees C. These properties (the high visible transmittance, the large change in infrared transmittance, and the near room-temperature MIPT) suggest that the current method is a landmark in the development of this interesting material toward applications in energy-saving smart windows.

8.
ACS Appl Mater Interfaces ; 1(10): 2211-8, 2009 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20355855

RESUMO

This article describes a novel and simple route to preparing VO(2) thermochromic films by using a VOCl(2) solution with poly(vinylpyrrolidone) (PVP). X-ray diffraction and Raman spectra showed that the VO(2) films deposited with PVP consisted of a nearly pure monoclinic/rutile (M/R) phase. Conversely, films prepared without PVP contained obviously impure crystalline phases. The as-prepared films with PVP showed excellent optical properties compared to those prepared by common gas-phase methods: an integral visible transmittance of 54.5% and an IR reduction (change in transmittance) of 41.5% at 2000 nm. The phase-transition temperatures were adjusted from 69 to 54 degrees C by tungsten doping. Equipment analyses revealed that PVP plays two roles in the film formation. First, it fundamentally acts as a film-forming promoter to improve physical gelation via interactions among oppositely charged carbonyl groups and amine groups of the polymer. Second, the negatively charged carbonyl groups can interact with VO(2+) to form a uniform mixed-gel film after solvent evaporation. Thus, the addition of PVP can stabilize the solution and improve the as-prepared film quality and phase purity. The current study suggests that the process has promise in applications of smart windows.

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