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

Abstract Due to their unique structures and physicochemical properties, porous anodic metal oxides including Al2O3, Fe2O3, TiO2, Ta2O5 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 TiO2 nanotube arrays can decrease dramatically under high voltage accompanied by high current density. Impact factors determining the formation of small pore TiO2 nanotubes under high voltage were discussed. Typically, with the same electrolyte used, the average pore diameter of TiO2 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 TiO2 nanotubes could be grown with a rate orders of magnitude faster than those grown in a classic way with low voltage and current density.