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 similar to 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 (Delta V) between the cathodic and the anodic peak potentials for TiO2 nanofibers and nanoparticles (sizes similar to 15-30 nm) are in the range, 0.23-0.30 V and a redox couple Ti4+/3+ around similar to 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 similar to 23% for nanofibers, which was nearly one-third of that of corresponding nanoparticles (similar to 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. (C) 2010 Elsevier Ltd. All rights reserved.