Enhancement of the electrochemical capacitance of TiOF2 obtained via control of the crystal structure

TiOF2 was successfully prepared as an electrochemical capacitor electrode material by novel method, which is NF3 treatment of a TiO2 precursor at controlled reaction temperatures to modulate its structure and surface properties. The crystal phase of TiOF2 changed to fluorine-doped anatase TiO2 upon increasing the NF3 treatment temperature. This structural change was induced to reduce the Ti3+ ratio of the TiOF2 surface. The specific capacitance of the TiOF2 phase treated by fluorination with NF3 gas at 580 degrees C was sevenfold higher than that of anatase TiO2 in this study. The enhanced capacitance of TiOF2 is expected to lead to a higher conductivity and charge transfer of the TiOF2 phase in comparison to anatase TiO2, which is primarily attributed to the higher Ti3+ ratio. (C) 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.