Fast fabrication of small pore anodic titania nanotube arrays under high voltage

Due to their unique structures and physicochemical properties, porous anodic metal oxides including Al 2 O 3 , Fe 2 O 3 , TiO 2 , Ta 2 O 5 and so on, prepared by anodization of corresponding metal substrates in appropriate electrolytes have found applications in various fields. Pore diameter plays a significant role in applications of these anodic metal oxides. It is a common knowledge that the pore diameter of porous metal oxides increases with formation voltage despite of a vast variation of anodization parameters and electrolytes used. Here, we demonstrate that the pore diameter and cell size of anodic TiO 2 nanotube arrays can decrease dramatically under high voltage accompanied by high current density. Impact factors determining the formation of small pore TiO 2 nanotubes under high voltage were discussed. Typically, with the same electrolyte used, the average pore diameter of TiO 2 nanotube arrays changes from ca 26 nm at a formation voltage of 10 V to ca 13 nm at 200 V. It is also demonstrated that at high voltage, small pore TiO 2 nanotubes could be grown with a rate orders of magnitude faster than those grown in a classic way with low voltage and current density.