Morphology control of anodic TiO₂ nanomaterials via cold work pretreatment of Ti foils

Self-organized TiO₂ nanostructures fabricated using the convenient method of anodizing Ti foils have attracted much attention for various applications. Properties and performance of the anodic TiO₂ nanostructures have proven largely dependent on their morphology. Here we report that the simple cold work pretreatment of Ti foils has a strong impact on the morphology of the subsequently generated anodic TiO₂ nanostructures. By increasing the amount of cold work applied to the Ti foil, the morphology of the subsequently generated anodic TiO₂ can be converted from self-organized nanotube arrays to an exotic type of nanoporous structures. This exotic type of nanoporous structures features throughout the entire film thickness interwoven tiny tubes whose opening is approximately 30 nm wide. Formation mechanism of the exotic nanoporous structures is proposed. The exotic TiO₂ nanoporous materials enabled by the cold-work pretreatment of Ti substrates show higher photocatalytic efficiency than their nanotube counterparts. © 2011 The Electrochemical Society.