TiO2 Fibers: Tunable Polymorphic Phase Transformation and Electrochemical Properties

A series of one-dimensional (1D) nanoparticle-assembled TiO2 fibers with tunable polymorphs were prepared via a novel and large scale ForceSpinning (R) process of titanium tetraisopropoxide (TTIP)/polyvinylpyrrolidone (PVP) precursor fibers followed with a thermal treatment at various calcination temperatures. The thermal and structural transformations were characterized by thermogravimetric analysis/differential scanning calorimetry, scanning electron microscopy, and X-ray diffraction. The influence of polymorphic phase of the TiO2 fibers on the electrochemical performance in neutral aqueous 1 M Na2SO4 electrolyte was investigated. The polymorphic amorphous/anatase/rutile TiO2 fibers prepared at 450 degrees C achieved a highest capacitance of 21.2 F g(-1) (6.61 mF cm(-2)) at a current density of 200 mA g(-1), for which the improved electronic conductivity and activated pseudo-capacitance mechanism may be responsible. This work helps bridge the gap between nanoscience and manufacturing. It also makes polymorphism control of functional materials a potential strategy for further improving supercapacitive output of metal oxides.