Preparation Of Modified TiO₂ Nanotube Materials And Its Photocatalytic Properties

With the development of photocatalytic technology and nanotechnology,TiO₂ has been widely studied for environment pollution control.TiO₂ nanotube array not only has the essential attributes of TiO₂,but also has a large surface area and stronger adsorption capacity.It is widely used in various fields such as photocatalysis,photolysis of water into hydrogen,dye-sensitized solar cells.But TiO₂ has shortcomings,such as the low utilization of sunlight,the fast recombination rate of photo-generated electrons and holes,and so on.Therefore,it is important to expand the spectral response range of TiO₂ nanotube photocatalyst,reduce the recombination rate of photo-induced carriers and increase the photocatalytic activity.In this paper,TiO₂ nanotube array films were prepared by anodization on the surface of titanium in three different electrolytes.The morphology of the nanotubes was investigated by scanning electron microscopy?SEM?.And the results show that the surface topography of the nanotubes prepared in the electrolyte of 0.3 wt%HF concentration is better than 0.1 and 0.5 wt%HF.In NH₄F/ethylene glycol system,although the nanotubes prepared by one step anodization have uniform diameter,ordered arrangement,but the nanotubes are easy to gather together.And nanotube films by ultrasound are easily peeled from the substrate.Two steps anodization can get a better morphology bilayer nanotube structure,but its disadvantages are obvious,preparation process is complicated,and it costs long time.In NH₄F/glycerol system the prepared nanotubes are highly ordered and have uniform diameter.Highly ordered TiO₂ nanotube arrays were prepared in NH₄F/glycerol system by an electrochemical anodic oxidation,and prepared ZnO/TiO₂ nanotube array composites were obtained by chemical bath deposition method.The morphology structure,crystal structure and light absorption spectrum of samples were characterized by SEM,X-ray diffraction?XRD?,UV-visible absorption spectroscopy?UV-Vis DRS?respectively.The chemical bath deposition method allows ZnO successfully deposited onto the surface of TiO₂ nanotubes.The as synthesised ZnO/TiO₂ nanotube array composites remain the complete structure of nanotubes which can provides a larger surface area for photocatalytic reaction.The absorption intensity of the composites in the visible region also has significantly improvement and the absorption band edge exhibit redshift.By testing its photocurrent and photocatalytic properties,and both the visible light response and the degradation rate of methylene blue have significantly enhanced.The degradation rate of methylene blue increased from 50%to 83%.Fe₂O₃/TiO₂ nanotube array composite was prepared by anodic oxidation method and chemical bath method on the titanium substrate.The properties were characterized and the photoelectrochemical properties and the performance of photocatalytic degradation of methylene blue was investigated.The results showed that Fe₂O₃nanoparticles were successfully deposited on TiO₂ nanotube array.The modification not only broadened the absorption spectrum of TiO₂nanotube arrays to the visible light region,but also increased the photocurrent.The photocurrent response of Fe₂O₃ modified TiO₂nanotube arrays was 9 times higher than undecorated TiO₂ nanotube arrays.In the photocatalytic reaction,the highest methylene blue degradation rate can reach 80%,which was 30%higher than the bare TiO₂ nanotube arrays.