Weilin Xu

Cotton fabrics coated with lignosulfonate-doped polypyrrole for flexible supercapacitor electrodes

Polypyrrole/lignosulfonate (PPy/LGS) coated cotton fabrics have been prepared via in situ oxidation polymerization of pyrrole in the presence of lignosulfonate as both template and dopant. The mass loading on the fabric samples decreases dramatically with the increased LGS content. The electrical conductivity of the coated fabrics achieved 3.03 S cm−1 under the optimized conditions. The electrochemical properties of the coated fabrics were investigated using cyclic voltammetry and galvanostatic charge–discharge measurements. The specific capacitance of the coated fabrics can be as high as 304 F g−1 at a current density of 0.1 A g−1 in aqueous electrolyte. These novel fabrics are desirable for applications in wearable supercapacitors.

Photocatalytic degradation in aqueous solution using quantum-sized ZnO particles supported on sepiolite.

Quantum-sized ZnO particles supported on sepiolite (ZnO/sepiolite) was prepared by sol-gel method using the sepiolite of acid activation as carrier, zinc acetate dihydrate (Zn(CH(3)COO)(2).2H(2)O) and lithium hydroxide monohydrate (LiOH.H(2)O) as raw material. The size of ZnO which supported on fibrous sepiolite is about 5 nm when calcined at 200 degrees C. The behavior of ZnO/sepiolite composites in the degradation of C.I. Reactive Blue 4 was investigated. Under the optimal preparation conditions, when the content of ZnO was about 70 wt.% in the nanocomposites, the photocatalytic property of the ZnO/sepiolite was excellent. The degradation rate of 20 mg/L C.I. Reactive Blue 4 could get to 98% in 120 min at room temperature when the concentration of catalyst was 0.2 g/L. The photocatalytic decomposition of organic pollutants accords with a pseudo first-order kinetic. The pH and H(2)O(2) influence the degradation rate of the ZnO/sepiolite. The experiment indicated that after the catalyst had been used 5 times repeatedly, the degradation rate had been still above 80%.

Uniform Nickel Vanadate (Ni3V2O8) Nanowire Arrays Organized by Ultrathin Nanosheets with Enhanced Lithium Storage Properties.

Development of three-dimensional nano-architectures on current collectors has emerged as an effective strategy for enhancing rate capability and cycling stability of the electrodes. Herein, a novel type of Ni3V2O8 nanowires, organized by ultrathin hierarchical nanosheets (less than 5 nm) on Ti foil, has been obtained by a two-step hydrothermal synthesis method. Studies on structural and thermal properties of the as-prepared Ni3V2O8 nanowire arrays are carried out and their morphology has changed obviously in the following heat treatment at 300 and 500 °C. As an electrode material for lithium ion batteries, the unique configuration of Ni3V2O8 nanowires presents enhanced capacitance, satisfying rate capability and good cycling stability. The reversible capacity of the as-prepared Ni3V2O8 nanowire arrays reaches 969.72 mAh·g−1 with a coulombic efficiency over 99% at 500 mA·g−1 after 500 cycles.

Highly efficient unsymmetrical squaraines for panchromatic dye-sensitized solar cells: A computational study

The geometries, electronic structures and absorption spectra of two unsymmetrical squaraine dyes (SQ1 and SQ2) were theoretically investigated by using density functional theory (DFT) and time-dependent DFT (TD-DFT). The dye-(TiO2)9 nanocluster systems were also simulated to show the electronic coupling at the interface. The results reveal that compared to SQ1, SQ2 with an electron-rich thiophene spacer and a strongly π-accepting carboxycyanovinyl group could cause a red shift of the absorption spectrum, increase the oscillator strength and improve the light harvesting efficiency, thus leading to the larger short-circuit photocurrent density (JSC) in dye-sensitized solar cells (DSSCs), in good agreement with experimental data. While the larger normal dipole moment pointing outward from the semiconductor surface of SQ2 is the major factor resulting in the higher open-circuit photovoltage (VOC). Then, we designed another six dyes with different π-spacers to screen dyes with improved performance. The results indicate that SQ6, SQ7 and SQ8 with benzathiadiazole, bithiophene and thienothiophene spacer, respectively, will be more efficient squaraine dyes used in DSSCs. This study is expected to assist the design and synthesis of novel squaraine dyes.

Polypyrrole-encapsulated vanadium pentoxide nanowires on a conductive substrate for electrode in aqueous rechargeable lithium battery.

Precursors of ammonium vanadium bronze (NH4V4O10) nanowires assembled on a conductive substrate were prepared by a hydrothermal method. After calcination at 360°C, the NH4V4O10 precursor transformed to vanadium pentoxide (V2O5) nanowires, which presented a high initial capacity of 135.0mA h g(-1) at a current density of 50mA g(-1) in 5M LiNO3 aqueous solution; while the specific capacity faded quickly over 50 cycles. By coating the surface of V2O5 nanowires with water-insoluble polypyrrole (PPy), the formed nanocomposite electrode exhibited a specific discharge capacity of 89.9mA h g(-1) at 50mA g(-1) (after 100 cycles). A V2O5@PPy //LiMn2O4 rechargeable lithium battery exhibited an initial discharge capacity of 95.2mA h g(-1); and after 100 cycles, a specific discharge capacity of 81.5mA h g(-1) could retain at 100mA g(-1).

Self-assembled hairy ball-like V2O5 nanostructures for lithium ion batteries

Hairy ball-like nanostructures assembled from nanowires, are synthesized by a hydrothermal method. The reaction time has a significant effect on the morphologies of the products. After calcination at 360 °C, the precursor can be transformed to hairy ball-like V2O5 nanostructures, which present an excellent electrochemical performance for lithium ion batteries.

Three-Dimensional Porous Iron Vanadate Nanowire Arrays as a High-Performance Lithium-Ion Battery

Development of three-dimensional nanoarchitectures on current collectors has emerged as an effective strategy for enhancing rate capability and cycling stability of the electrodes. Herein, a new type of three-dimensional porous iron vanadate (Fe0.12V2O5) nanowire arrays on a Ti foil has been synthesized by a hydrothermal method. The as-prepared Fe0.12V2O5 nanowires are about 30 nm in diameter and several micrometers in length. The effect of reaction time on the resulting morphology is investigated and the mechanism for the nanowire formation is proposed. As an electrode material used in lithium-ion batteries, the unique configuration of the Fe0.12V2O5 nanowire arrays presents enhanced capacitance, satisfying rate capability and good cycling stability, as evaluated by cyclic voltammetry and galvanostatic discharge-charge cycling. It delivers a high discharge capacity of 293 mAh·g(-1) at 2.0-3.6 V or 382.2 mAh·g(-1) at 1.0-4.0 V after 50 cycles at 30 mA·g(-1).

Novel aligned sodium vanadate nanowire arrays for high-performance lithium-ion battery electrodes

Sodium vanadate (Na5V12O32 or Na1.25V3O8) nanowire arrays were successfully prepared using a facile hydrothermal method with subsequent calcination. The length of the Na5V12O32 nanowire arrays on titanium foil were about 10.5 μm. The unique architecture renders a high-rate transportation of lithium ions that is attributed to their nanosized structure, active materials connected to the current collector and the high specific surface area. The Na5V12O32 nanowire arrays on titanium foil annealed at 250 °C as electrodes for lithium-ion batteries exhibit a significant capacity stability with a capacity from 339.3 to 289.7 mA h g−1 in 50 cycles at 50 mA g−1. The superior electrochemical performance demonstrated that the Na5V12O32 nanowire arrays are promising electrodes for secondary organic lithium-ion batteries.

Lithium vanadate nanowires@reduced graphene oxide nanocomposites on titanium foil with super high capacities for lithium-ion batteries.

With a theoretically high capacity and suitable discharge/charge plateaus, lithium vanadates (such as Li0.04V2O5) can be used as cathode material for lithium ion batteries. Herein, Li0.04V2O5 nanowires are densely anchored onto reduced graphene oxide (rGO) nanosheets to form a Li0.04V2O5@rGO nanocomposite by a hydrothermal method with subsequent thermal treatment. Due to this unique structure, the Li0.04V2O5@rGO exhibits remarkable rate performance and excellent cycling stability. Specifically, it delivers a reversible discharge capacity of 738.09mAhg-1 at a current density of 100mAg-1 in the voltage range of 2.0-4.0V. After 500 cycles, it still maintains a high capacity of 731.70mAhg-1, which represents 95.01% retention of the original reversible capacity. These results indicate that the Li0.04V2O5@rGO could be a promising candidate as cathode active material for long-term cycling performance in lithium-ion batteries.

Hollow SnO2-ZnO hybrid nanofibers as anode materials for lithium-ion battery

Hollow SnO2–ZnO hybrid nanofibers are prepared by a single-nozzle electrospinning technique followed with subsequent heat treatment. The structure and morphology of the samples are characterized by x-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and transmission electron microscopy. The as-prepared nanofibers are solid, which maintain after annealing up to 400 °C; while they turn to tubular morphology after annealing at 500 °C. After annealing at 700–900 °C, some of the tubular nanofibers combine together. The FTIR results show that poly (vinylpyrrolidone) is completely removed after annealing at 500 °C. The electrode of hollow SnO2–ZnO nanofibers obtained by calcination at 500 °C delivers a high discharge capacity of 546.5 mAh g−1 after 100 cycles at a current density of 100 mA g−1.