Fabrication of high aspect ratio and open-ended TiO₂ nanotube photocatalytic arrays through electrochemical anodization

Well-aligned, high aspect-ratio and open-ended TiO₂ nanotube arrays secured within a Ti foil (TiO₂ nanotubes cartridge) were successfully prepared through the double-sided anodization method. With ∼210 μm of nanotube length, the anodic growth of TiO₂ was accelerated and stabilized by the lactic acid-containing ethylene glycol electrolyte. In the absence of lactic acid, the anodization led to detachment of nanotubes from the Ti foil after 5-6 h of high voltage (80 V) anodization. Transmission electron microscope image and Raman spectrum revealed that the as-anodized TiO₂ nanotube arrays without annealing treatment were partially crystalline anatase and demonstrated photocatalytic activity in the mineralization of formic acid.