7 research outputs found

    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

    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

    Hollow Structured Silicon Anodes with Stabilized Solid Electrolyte Interphase Film for Lithium-Ion Batteries

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    Silicon has been considered as a promising anode material for the next generation of lithium-ion batteries due to its high specific capacity. Its huge volume expansion during the alloying reaction with lithium spoils the stability of the interface between electrode and electrolyte, resulting in capacity degradation. Herein, we synthesized a novel hollow structured silicon material with interior space for accumulating the volume change during the lithiation. The as-prepared material shows excellent cycling stability, with a reversible capacity of ∼1650 m Ah g<sup>–1</sup> after 100 cycles, corresponding to 92% retention. The electrochemical impedance spectroscopy and differential scanning calorimetry were carried out to monitor the growth of SEI film, and the results confirm the stable solid electrolyte interphase film on the surface of hollow structured silicon

    Polysulfides Capture-Copper Additive for Long Cycle Life Lithium Sulfur Batteries

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    Copper powder was introduced into the lithium sulfur battery system to capture intermediate polysulfides and Cu<sub><i>x</i></sub>S (<i>x</i> = 1 or 2) species was generated depending on the chain length of polysulfides. This phenomenon was verified by X-ray absorption near edge structure technique. The results indicated that copper can be oxidized to CuS by Li<sub>2</sub>S<sub><i>x</i></sub> (<i>x</i> ≥ 6), and a mixture of Cu<sub>2</sub>S and CuS was obtained when <i>x</i> ranges from 3 to 6. While Cu<sub>2</sub>S is eventually formed in the presence of Li<sub>2</sub>S<sub>3</sub>. After several cycles activation, the polysulfide-shuttle effect and self-discharge phenomenon which hinder the application of lithium sulfur batteries are found nearly eliminated Further experiments demonstrated that in the case of Cu<sub>2</sub>S generation, a high specific sulfur capacity of 1300 mAh g<sup>–1</sup> could be delivered, corresponding to 77.6% sulfur utilization, while the Coulombic efficiency approximates around 100%. Self-discharge experiment further demonstrated that polysulfides almost disappear in the electrolyte, which verified the polysulfide-capture capability of copper

    Hierarchical Mesoporous Iron Fluoride with Superior Rate Performance for Lithium-Ion Batteries

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    Monodispersed mesoporous iron fluorides were synthesized by a low-cost reversed micelle method. The as-prepared materials with hierarchical mesoporous structure exhibit excellent rate capability (115.6 mAh g<sup>–1</sup> at 2000 mA g<sup>–1</sup>) which is superior to many other carbon-free iron fluorides. In addition, a high reversible capacity of 143.2 mAh g<sup>–1</sup> can be retained after 100 cycles at 1000 mA g<sup>–1</sup>. The outstanding electrochemical features can be attributed to the particular hierarchical mesoporous structure, facilitating electrolyte penetration as well as rapid electronic and ionic transportation

    Confined Solid Electrolyte Interphase Growth Space with Solid Polymer Electrolyte in Hollow Structured Silicon Anode for Li-Ion Batteries

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    Silicon anodes for lithium-ion batteries are of much interest owing to their extremely high specific capacity but still face some challenges, especially the tremendous volume change which occurs in cycling and further leads to the disintegration of electrode structure and excessive growth of solid electrolyte interphase (SEI). Here, we designed a novel approach to confine the inward growth of SEI by filling solid polymer electrolyte (SPE) into pores of hollow silicon spheres. The as-prepared composite delivers a high specific capacity of more than 2100 mAh g<sup>–1</sup> and a long-term cycle stability with a reversible capacity of 1350 mAh g<sup>–1</sup> over 500 cycles. The growing behavior of SEI was investigated by electrochemical impedance spectroscopy and differential scanning calorimetry, and the results revealed that SPE occupies the major space of SEI growth and thus confines its excessive growth, which significantly improves cycle performance and Coulombic efficiency of cells embracing hollow silicon spheres

    High Volumetric Capacity of Hollow Structured SnO<sub>2</sub>@Si Nanospheres for Lithium-Ion Batteries

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    A novel design of hollow structured SnO<sub>2</sub>@Si nanospheres was presented, which not only demonstrates high volumetric capacity as anode of LIBs, but also prevents aggregation of Sn and confines solid electrolyte interphase thickening. An impressive volumetric specific capacity of 1030 mAh cm<sup>–3</sup> was maintained after 500 cycles. The electrochemical impedance spectroscopy and differential scanning calorimetry indicated that solid electrolyte interphase can be confined in pores of as-prepared hollow structured SnO<sub>2</sub>@Si
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