Growth mechanism and photocatalytic performance of double-walled and bamboo-type TiO2 nanotube arrays

Abstract

Double-walled and bamboo-type TiO₂ nanotube arrays on titanium can be grown by a self-organized electrochemical anodization in viscous organic electrolytes. In order to better understand the growth process of this novel structure, anodized samples under alternating voltage (AV) conditions at different stages were systematically studied. Field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy were used to investigate the morphology, structure, and crystalline and chemical components of the resulting TiO₂ nanotubes. Meanwhile, the corresponding current versus time curves were recorded to monitor the process. Based on the results obtained, the possible formation mechanism of these novel nanotubes was explored. It was noted that the formation of double-walled and bamboo-type structure has a close relationship with the current density and ion-diffusion gradient inside the TiO₂ nanotubes. In our experiment, the double-walled and bamboo-type TiO₂ nanotube arrays can be repeatedly and successfully synthesized via AV anodization. In addition, the solar-light induced photocatalytic decomposition of stearic acid of the nanotube arrays obtained was presented. Double-walled and bamboo-type TiO₂ nanotube arrays showed higher efficiencies than those based on smooth-walled nanotubes with the same tube length because of enhanced specific surface area.