Preparation and electrochemical studies of electrospun TiO2 nanofibers and molten salt method nanoparticles

The TiO₂ nanofibers and nanoparticles are prepared by electrospinning and molten salt method, respectively. The materials are characterized by X-ray diffraction scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and a thermal analysis. The SEM and TEM studies showed that fibers were of average diameter ∼100 nm and composed of nanocrystallites of size 10-20 nm. Electrochemical properties of the materials are evaluated using cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy. Cyclic voltammetric studies show a hysteresis (ΔV) between the cathodic and the anodic peak potentials for TiO₂ nanofibers and nanoparticles (sizes ∼15-30 nm) are in the range, 0.23-0.30 V and a redox couple Ti^4+/3+ around ∼1.74/2.0 V. Electrochemical cycling results revealed that the TiO₂ nanofibers have lower capacity fading compared to that of the nanoparticles. The capacity fading for 2-50 cycles was ∼23% for nanofibers, which was nearly one-third of that of corresponding nanoparticles (∼63%). We discussed the effect of particle size on hysteresis and cycling performance of TiO₂ nanoparticles. Impedance analysis of TiO₂ nanofibers and nanoparticles during first discharge cycle is analyzed and interpreted.