Characterization and Induced Photocurrent of TiO2 Nanotube Arrays Fabricated by Anodization

The fabrication of TiO2 nanotube arrays (TNTs) by the anodization of titanium foil in electrolyte containing fluoride was carried out in this study. The surface dimension, phase formation, and lattice parameters of TNTs were determined by the field-emission-scanning electron microscopy and X-ray diffractometer, respectively. The induced photocurrent intensity of TNTs was measured by a potentiostat/galvanostat. The well-defined and highly ordered TNTs were formed in glycerol electrolyte with a water content of 20%. The inner diameter of the TNTs was mainly determined by the anodization voltage, while the length of the TNTs was affected by both anodization voltage and anodization time. The length of the nanotube was continually increased with anodization time until the rates of the electrochemical oxidization of Ti foil and the chemical dissolution of the TiO2 film reached a dynamic equilibrium. The TNTs annealed at 600 degrees C demonstrated the highest induced photocurrent because of the crystallization of anatase and rutile phases. The increase in the tube length and the decrease in the inner diameter induced higher photocurrents under specific conditions of UV illumination because of a higher illuminated area. However, the enhancement of the induced photocurrent was retarded when the length of the TNTs reached 2000 nm due to the limited penetration of incident UV light penetrated through the nanotube. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3384659] All rights reserved.