9 research outputs found

    Durable and Efficient PTFE Sandwiched SPEEK Membrane for Vanadium Flow Batteries

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    To overcome the poor cycling stability of sulfonated poly­(ether ether ketone) (SPEEK) membrane in vanadium flow batteries (VFB), we demonstrate a facile and effective sandwich design by using hydrophilic porous poly­(tetrafluoroethylene) (PTFE) films as a stress protective and electrolyte buffer layer for SPEEK membrane. VFB based on this novel sandwich PTFE/SPEEK/PTFE membrane exhibits super long-life properties, which can steadily run (98.5% of Coulombic efficiency and 85.0% of energy efficiency @ 80 mA cm<sup>–2</sup>) with 2.0 M vanadium electrolyte for more than 1000 cycles. This simple and powerful strategy may also be applied to other nonfluoride membranes

    Constructing Three-Dimensional Hierarchical Architectures by Integrating Carbon Nanofibers into Graphite Felts for Water Purification

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    Developing high-performance nanostructured sorbents for water treatment is of great importance. Herein, we report a facile strategy to fabricate three-dimensional hierarchical architectures by integrating carbon nanofibers (CNFs) into macroscopic graphite felt (GF) supports. The physicochemical properties of CNF@GF monoliths including surface areas, densities, porosities, and pore structures could be conveniently tuned by varying reaction time. The CNF@GF monoliths were utilized as advanced sorbents for the removal of Pb<sup>2+</sup>, Congo red, organic solvents, and oils from aqueous solutions. The characteristics of adsorption processes including kinetics, isotherms, and regeneration were investigated. It is demonstrated that the CNF@GF exhibits outstanding performance for water treatment in terms of adsorption capacities, recovering, and recyclability. As such, the versatile CNS@GF monoliths show great application potential for water treatment

    Rice Paper Reinforced Sulfonated Poly(ether ether ketone) as Low-Cost Membrane for Vanadium Flow Batteries

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    Low-cost, highly efficient, and durable membrane is essential for practical application of vanadium flow battery (VFB). Sulfonated poly­(ether ether ketone) (SPEEK) membrane is considered as potential candidate to replace the expensive Nafion membrane because of its high proton to vanadium ion selectivity. To overcome the poor mechanical/chemical stability of SPEEK membrane in VFB, a new strategy by using commercial paper (copy paper, rice paper, and filter paper) as the scaffold of SPEEK, and subsequently self-cross-linking the SPEEK through thermal treatment was conducted. The optimized rice paper reinforced SPEEK membrane exhibits superior VFB performances to that of the benchmark Nafion 115 membrane, such as 98.3% vs 92.8% for Coulombic efficiency, 79.5% vs 75.8% for energy efficiency, and 0.13% vs 0.16% for capacity decay per cycle at a high current density of 120 mA cm<sup>–2</sup>. Besides, S@RP-C6 shows an extremely stable performance in the temperature range of 0–70 °C. Combining the outstanding battery performances with the extremely low cost (estimated at about $10 per m<sup>2</sup>), the rice paper reinforced SPEEK membrane shows a very good application prospect in VFB

    Constructing Three-Dimensional Hierarchical Architectures by Integrating Carbon Nanofibers into Graphite Felts for Water Purification

    No full text
    Developing high-performance nanostructured sorbents for water treatment is of great importance. Herein, we report a facile strategy to fabricate three-dimensional hierarchical architectures by integrating carbon nanofibers (CNFs) into macroscopic graphite felt (GF) supports. The physicochemical properties of CNF@GF monoliths including surface areas, densities, porosities, and pore structures could be conveniently tuned by varying reaction time. The CNF@GF monoliths were utilized as advanced sorbents for the removal of Pb<sup>2+</sup>, Congo red, organic solvents, and oils from aqueous solutions. The characteristics of adsorption processes including kinetics, isotherms, and regeneration were investigated. It is demonstrated that the CNF@GF exhibits outstanding performance for water treatment in terms of adsorption capacities, recovering, and recyclability. As such, the versatile CNS@GF monoliths show great application potential for water treatment

    Ternary Platinum–Copper–Nickel Nanoparticles Anchored to Hierarchical Carbon Supports as Free-Standing Hydrogen Evolution Electrodes

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    Developing cost-effective and efficient hydrogen evolution reaction (HER) electrocatalysts for hydrogen production is of paramount importance to attain a sustainable energy future. Reported herein is a novel three-dimensional hierarchical architectured electrocatalyst, consisting of platinum–copper–nickel nanoparticles-decorated carbon nanofiber arrays, which are conformally assembled on carbon felt fabrics (PtCuNi/CNF@CF) by an ambient-pressure chemical vapor deposition coupled with a spontaneous galvanic replacement reaction. The free-standing PtCuNi/CNF@CF monolith exhibits high porosities, a well-defined geometry shape, outstanding electron conductivity, and a unique characteristic of localizing platinum–copper–nickel nanoparticles in the tips of carbon nanofibers. Such features render PtCuNi/CNF@CF as an ideal binder-free HER electrode for hydrogen production. Electrochemical measurements demonstrate that the PtCuNi/CNF@CF possesses superior intrinsic activity as well as mass-specific activity in comparison with the state-of-the-art Pt/C catalysts, both in acidic and alkaline solutions. With well-tuned composition of active nanoparticles, Pt<sub>42</sub>Cu<sub>57</sub>Ni<sub>1</sub>/CNF@CF showed excellent durability. The synthesis strategy reported in this work is likely to pave a new route for fabricating free-standing hierarchical electrodes for electrochemical devices

    Toward Cheaper Vanadium Flow Batteries: Porous Polyethylene Reinforced Membrane with Superior Durability

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    Developing cheap and durable proton exchange membrane is crucial to promote the practical application of vanadium flow batteries (VFB). Here we report a simple and scalable method to fabricate a reinforced sulfonated poly­(ether ether ketone) (SPEEK) membrane using a lithium-ion battery separator, ceramic-coated porous polyethylene (CCP), as a robust scaffold. With the confinement effect of the extremely stable CCP substrate, the reinforced SPEEK membrane (S@CCP) shows significantly improved chemical/mechanical stability and reduced vanadium ion permeability compared to the control SPEEK membrane. Accordingly, the S@CCP membrane demonstrates excellent rate performance and cycling stability than those of the benchmark Nafion 212 membrane. It exhibits stable performance over 1500 cycles at 160 mA cm<sup>–2</sup> with 99% of CE, 76% of EE and 0.126% of capacity decay per cycle. Meanwhile, the S@CCP membrane is highly resistant to temperature fluctuations over a wide range of −20–60 °C. The superior durability, wide temperature adaptability, and low cost suggest that the S@CCP membrane offers great promise as an ideal membrane for VFB application

    ZrO<sub>2</sub>‑Nanoparticle-Modified Graphite Felt: Bifunctional Effects on Vanadium Flow Batteries

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    To improve the electrochemical performance of graphite felt (GF) electrodes in vanadium flow batteries (VFBs), we synthesize a series of ZrO<sub>2</sub>-modified GF (ZrO<sub>2</sub>/GF) electrodes with varying ZrO<sub>2</sub> contents via a facile immersion-precipitation approach. It is found that the uniform immobilization of ZrO<sub>2</sub> nanoparticles on the GF not only significantly promotes the accessibility of vanadium electrolyte, but also provides more active sites for the redox reactions, thereby resulting in better electrochemical activity and reversibility toward the VO<sup>2+</sup>/VO<sub>2</sub><sup>+</sup> and V<sup>2+</sup>/V<sup>3+</sup> redox reactions as compared with those of GF. In particular, The ZrO<sub>2</sub>/GF composite with 0.3 wt % ZrO<sub>2</sub> displays the best electrochemical performance with voltage and energy efficiencies of 71.9% and 67.4%, respectively, which are much higher than those of 57.3% and 53.8% as obtained from the GF electrode at 200 mA cm<sup>–2</sup>. The cycle life tests demonstrate that the ZrO<sub>2</sub>/GF electrodes exhibit outstanding stability. The ZrO<sub>2</sub>/GF-based VFB battery shows negligible activity decay after 200 cycles

    Synthesis of Ultrafine Pt Nanoparticles Stabilized by Pristine Graphene Nanosheets for Electro-oxidation of Methanol

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    In this study, the pristine graphene nanosheets (GNS) derived from chemical vapor deposition process were employed as catalyst support. In spite of the extremely hydrophobic GNS surface, ultrafine Pt nanoparticles (NPs) were successfully assembled on the GNS through a surfactant-free solution process. The evolution of Pt NPs in the GNS support was studied using transmission electron microscopy. It was found that the high-energy surface sites in the GNS, such as edges and defects, played a critical role on anchoring and stabilizing Pt nuclei, leading to the formation of Pt NPs on the GNS support. The concentration of the Pt precursor, i.e., H<sub>2</sub>PtCl<sub>6</sub> solution had significant effects on the morphology of Pt/GNS hybrids. The resulting Pt/GNS hybrids were examined as catalysts for methanol electro-oxidation. It was indicated that the electrochemical active surface area and catalytic activity of the Pt/GNS hybrids were highly dependent on Pt loadings. The superior activity of the catalysts with low Pt loadings was attributed to the presence of Pt subnanoclusters as well as the strong chemical interaction of Pt NPs with the GNS support

    Novel Organic D‑π-2A Sensitizer for Dye Sensitized Solar Cells and Its Electron Transfer Kinetics on TiO<sub>2</sub> Surface

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    Although numerous donor-π-acceptor (D-π-A) type organic dyes were investigated in order to replace the ruthenium polypyridyl complexes, there have been few reports of the D-π-2A system and the related electron transfer processes. In this work, a novel D-π-2A dye (coded as <b>B2</b>) was designed and synthesized for applications in dye-sensitized solar cells (DSSC). Obvious intramolecular charge transfer (ICT) between the donor and acceptor takes place under photoexcitation. Three frontier LUMOs (LUMO, LUMO+1, LUMO+2) of <b>B2</b> are all located on the acceptor part, which is highly favorable for intramolecular electron transfer from the donor to acceptors and enhances the electron injection into the semiconductors. DSSC based on <b>B2</b> showed a maximum monochromatic incident photon-to-current efficiency (IPCE) of 68% at 425 nm and an overall power conversion efficiency of 3.62% under simulated solar light (AM 1.5G, 100 mW cm<sup>–2</sup>) irradiation. Femtosecond and nanosecond TA, and TCSPC techniques were used to monitor the photophysical properties of <b>B2</b> and the electron transfer processes taking place between <b>B2</b> and the semiconducting nanoparticles. It is found that electrons in the delocalized π→π* transition could be further injected into the semiconductor, while such injection process hardly happens for electrons in the localized π→π* transition
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