TiO2 Hollow Nanofibers Research Articles

Fabrication and characterization of hollow TiO2 fibers by microemulsion electrospinning for photocatalytic reactions

We report a versatile microemulsion electrospinning method to fabricate hollow TiO2 nanofibers. A microemulsion of titanium isopropoxide (TiP)/poly(methyl methacrylate)(PMMA) solution, hexadecyl trimethyl ammonium bromide (CTAB; surfactant), and paraffin oil was used as the precursor, with an electrospinning method. The TiO2 samples were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) analyses. The specific surface areas of the TiO2 fibers and hollow TiO2 fibers were 30.01 and 59.27m2/g, respectively. The pore volumes of the TiO2 fibers and hollow TiO2 fibers were 0.10 and 0.19cm3/g, respectively. The average pore size of the samples was 3.7nm. These photocatalysts were evaluated based on the photodecomposition of methylene blue under ultraviolet light. The photocatalytic degradation rate followed a pseudo-first-order equation. The kinetic constants (k1) of the TiO2 fiber and hollow TiO2 fibers samples were 2.18×10−2 and 3.47×10−2, respectively.

Fabrication of nanostructured hollow TiO2 nanofibers with enhanced photocatalytic activity by coaxial electrospinning

Two types of hollow crystalline titanium dioxide (TiO2) nanofibers were successfully fabricated through a facile coaxial electrospinning technique, with titanium sol and titanium precursor respectively as the materials for the shell. The two types of hollow TiO2 nanofibers possessed a similar tubular feature on the nanometer scale, but different morphology on surface nanostructures and size on shell thickness. Hollow nanofibers prepared by using titanium sol demonstrated that a small amount of water in core could prevent efficiently the diffusion of the core and shell solutions. For the titanium precursor without spinnability, it could be coated on the poly(vinyl pyrrolidone) core nanofibers as shell templates during the coaxial electrospinning process and properly developed into nanostructured TiO2 wall of the hollow nanofibers. Both of hollow TiO2 nanofibers exhibited higher photocatalytic activity for degradation methylene blue in comparison with the solid TiO2 nanofibers prepared by normal electrospinning due to their unique hollow structure.

Synthesis of TiO2 hollow nanofibers by co-axial electrospinning and its superior lithium storage capability in full-cell assembly with olivine phosphate

We report the formation and extraordinary Li-storage properties of TiO2 hollow nanofibers by co-axial electrospinning in both the half-cell and full-cell configurations. Li-insertion properties are first evaluated as anodes in the half-cell configuration (Li/TiO2 hollow nanofibers) and we found that reversible insertion of ~0.45 moles is feasible at a current density of 100 mA g(-1). The half-cell displayed a good cyclability and retained 84% of its initial reversible capacity after 300 galvanostatic cycles. The full-cell is fabricated with a commercially available olivine phase LiFePO4 cathode under optimized mass loading. The LiFePO4/TiO2 hollow nanofiber cell delivered a reversible capacity of 103 mA h g(-1) at a current density of 100 mA g(-1) with an operating potential of ~1.4 V. Excellent cyclability is noted for the full-cell configuration, irrespective of the applied current densities, and it retained 88% of reversible capacity after 300 cycles in ambient conditions at a current density of 100 mA g(-1).

Multichannel hollow TiO2 nanofibers fabricated by single-nozzle electrospinning and their application for fast lithium storage

Multichannel hollow TiO2 nanofibers were synthesized via a facile single-nozzle electrospinning method based on phase-separation mechanism. Compared to normal TiO2 nanofibers, hollow TiO2 with higher surface area gave rises to a higher surface contribution and ensured a short diffusion path for ion transport. Thus hollow TiO2 demonstrated superior cyclic ability and excellent rate capability.

SnO2 encapsulated TiO2 hollow nanofibers as anode material for lithium ion batteries

Nanoparticulate SnO2 was encapsulated into TiO2 hollow nanofibers to achieve high energy density and robust electrochemical performance as an anode material for lithium ion batteries. The SnO2 encapsulated TiO2 hollow nanofibers exhibit improved electrochemical performances over the TiO2 hollow nanofibers, including a high discharge capacity of ~517mAhg−1 and doubled capacity at a 10C rate. These improvements on electrochemical performances are attributed to favorable mechanics and kinetics associated with lithium.

Synthesis of LiCl Doped Hollow TiO<sub>2</sub> Nanofibers via Electrospinning and Their Humidity-Sensing Properties

LiCl doped titania (TiO2) hollow nanofibers were prepared by using polylactide (PLA) nanofibers as templates. The morphology and crystal structure of the TiO2hollow nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The as-prepared LiCl doped TiO2hollow nanofibers exhibited a good humidity-sensing property. During the relative humidity (50%-95%) measurement, the response and recovery time is about 3 and 4 s, separately, with good linearity. The relationship between the humidity-sensing properties and the structure of the hollow nanofibers was also discussed. These distinguished and sensitive sensing performances make this material a good candidate in fabricating humidity sensors.

Nitridated TiO2 hollow nanofibers as an anode material for high power lithium ion batteries

TiO2 nanofibers, TiO2 hollow nanofibers, and nitridated TiO2 hollow nanofibers were synthesized using a simple electrospinning method and subsequent nitridation treatment. The nitridated TiO2 hollow nanofibers showed twice higher rate capability compared to that of pristine TiO2 nanofibers at 5 C. This improvement is mainly attributed to shorter lithium ion diffusion length and high electronic conductivity along the surface of nitridated hollow nanofibers.

Preparation of TiO2 hollow nanofibers by electrospining combined with sol–gel process

TiO2 hollow nanofibers have been fabricated by directly annealing electrospun polyvinylpyrrolidone (PVP)/Tetra-butyl titanate (TBT) composite nanofibers. In this approach, PVP/TBT composite fibers were first synthesized by electrospinning PVP/TBT solution, and then calcined at high temperature with an appropriate heating rate to form hollow TiO2 nanofibers. During the heat treatment, the solvent composition, the amount of TBT and the heating rate have important influences on the morphologies of the TiO2 nanofibers. Morphologies of TiO2 could be tuned from solid nanofibers to belts, hollow nanofibers and rods by controlling the appropriate preparation conditions. The crystal structure, morphology, surface composition and specific surface area of the TiO2 hollow nanofibers were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Brunauer–Emmett–Teller analysis, respectively.