Preparation And Morphology Control Of Single-joint And Multi-joint Titania Nanotube Arrays

TiO2 is a popular photocatalyst because of its activity, stability and biompatibility advantages. Compared with granular TiO2, TiO2 nanotubes have a larger surface area, higher catalytic activity and higher adhesion.They have high research and application value in photocatalytic hydrogen evolution, sewage treatment, sensitized solar cell, etc. However, due to a wide band gap of TiO2 (3.2～3.6eV), photocatalysis processes can only absorb the sun’s ultraviolet light, can not absorb visible light,, resulting in low photoelectric conversion efficiency. To reduce the band gap of TiO2,the nanotube structures need to be improved to increase the surface area.In this paper, the glycol electrolyte solution of NH4F is used to prepare TiO2 nanotube arrays with different morphologies by anodic oxidation; Discuss the impact of various factors on the morphology of nanotube arrays to determine the best preparation process; Research the formation mechanism of the different morphology nanotube arrays. Using scanning electron microscopy and X-ray diffraction to characterized the morphology and phase of nanotube arrays.The results show that:the formation of nanotube morphology is because voltage breakdown titanium surface oxide film. Anodic oxidation occurs in the pores of between titanium substrate and electrolyte. The oxidation reaction is continued as the voltage, laterally microporous expanded to tubular shape,longitudinal grew perpendicular to the titanium substrate, eventually forming a homogeneous nanotube regular array structure;Compared with the low-voltage of direct-current, nanotube arrays are more uniform and higher growth efficiency under high pressure pulse conditions. After several orthogonal experiment to determine the optimal preparation process. Multi-joint TiO2 nanotube arrays with larger surface arear can be prepared under high pulse voltage through several anodizing, due to the presence of F-ion concentration gradient leads to a layered morphology of nanotubes.Pulse voltage condition, the high and low voltage was alternated to perpare bamboo-joint nanotube arrays, the arrays have larger surface area than the multi-joint nanotube arrays; Bamboo-joint nanotube arrays are firmer just because up and down through morphology.It also can help improve photocatalytic properties because of electrons’circulatio.Alternating high and low voltage can be applied to ensure the orderly anodic oxidation, nanotubes grown under high voltage conditions and bamboo-joint oxide formed under low voltage conditions.