Significance of crystallinity on the photoelectrochemical and photocatalytic activity of TiO2 nanotube arrays

We report the significance of crystallinity on photoelectrochemical and the photocatalytic degradation of methyl orange of titanium dioxide (TiO2) nanotube arrays. The TiO2 nanotube arrays are fabricated by electrochemical anodization of titanium substrates in fluoride based aqueous electrolyte for various anodization time. The degree of crystallinity and phase purity (anatase) is confirmed from X-ray diffraction and Raman spectra. High resolution scanning electron microscope is used to analyze the surface morphology of forming nanotubes. The UV-vis absorption spectrum shows the enhanced absorption in the visible region which is further confirmed using photoluminescence spectra. The photoelectrochemical properties of the prepared samples are studied from linear sweep photovoltammetry measurements and a maximum photocurrent density of 1.32 mA/cm2 is observed. The enhanced photoelectrochemical activity is attributed to the higher crystallinity which increases the charge carrier separation and extends its light absorption from ultraviolet to visible region owing to lower band gap of 2.751(7) eV.