The morphology, structure and crystalline phase of TiO2 nanotube array were characterized by the scanning electron microscopy and X-ray diffractometer
Some critical structure factors of titanium oxide nanotube array in its photocatalytic activity.
Environmental science & technology, no. 13 (2007): 4735-4740
A highly ordered TiO2 nanotube array on Ti substrate was fabricated by using an electrochemical anodic oxidation method. The morphology, crystalline phase, and photoelectrochemical property of the nanotube array were characterized. The photocatalytic activity of the nanotube array was evaluated by the decolorization of methyl orange in aq...更多
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- The heterogeneous photocatalysis of titanium oxide (TiO2) has become a hot subject in recent years as it is an attractive technique for completely eliminating perpetual chemical pollutants in the environment by using solar or artificial light illumination.
- For comparison with the short nanotube array film, the 400 nm-thick TiO2 nanoparticle film on titanium substrate was prepared by using sol-gel method.
- The heterogeneous photocatalysis of titanium oxide (TiO2) has become a hot subject in recent years as it is an attractive technique for completely eliminating perpetual chemical pollutants in the environment by using solar or artificial light illumination
- The highly ordered TiO2 nanotube array films with various morphologies were fabricated by the anodic oxidation method
- The morphology, structure and crystalline phase of TiO2 nanotube array were characterized by the scanning electron microscopy (SEM) and X-ray diffractometer (XRD)
- The photocatalytic activity of the TiO2 nanotube array in methyl orange (MO) aqueous solution, as a typical pollutant in the textile industries, was evaluated and compared with that of the TiO2 nanoparticle film prepared by the sol-gel method
- For comparison with the short nanotube array film, the 400 nm-thick TiO2 nanoparticle film on titanium substrate was prepared by using sol-gel method
- At the same anodization voltage (20 V), the nanotubes grown for anodization time of 1, 2, 5, 9 h have average lengths of 1.5, 2.5, 3.1, 3.5 μm, respectively, with almost the same tube diameter as the 0.4 μm length nanotubes
- The photogenerated charge carriers in the TiO2 nanotube structure might be separated more efficiently than the TiO2 nanoparticle film because of the short diffusion distance in the tube wall and the high contact area between the photocatalyst and electrolyte (29-31).
- Photocatalytic Degradation of MO Using TiO2 Nanotube Array Film.
- The apparent first-order rate constant of the photocatalytic degradation of MO with the assistance of TiO2 photocatalyst is significantly higher than that of MO self-photolysis.
- From the plot of absorption vs wavelength (Figure 5), a decrease in the absorbance at 508 nm reflects the degradation of MO on the TiO2 photocatalyst, thereby it can be used as a measure of the photocatalytic activity.
- Under the high-pressure mercury lamp illumination, the photocatalytic degradation rate of MO initially increases with increasing of the thickness of TiO2 nanotube array film, and has a down trend with an optimized efficiency of the MO photodegradation at the thickness of 2.5 μm in the experiments.
- Using the tungstenhalogen lamp as the light source, the apparent rate constant k increases from 0.0178 to 0.0222 min-1 as the thickness of TiO2 nanotube film increases from 0.4 to 2.5 μm, and reaches an almost steady value at approximately 0.02 min-1.
- The species have a longer diffusion path to the interior TiO2 photocatalyst in the longer nanotube array film, and this may cause a decrease in photocatalytic degradation rate.
- The possible reason may be on the one hand that the specific surface area of TiO2 nanotubes array is decreased with increasing of the diameter of nanotubes, resulting in a negative effect on photocatalytic activity.
- Table1: Effect of the Thickness of TiO2 Nanotube Array Film on the First-Order Rate Constant k of Photocatalytic Degradation thickness of TiO2 nanotubes film (μm)
- Table2: The Effect of the Diameter of TiO2 Nanotubes on the First-Order Rate Constant k of Photocatalytic Degradation diameter of TiO2 nanotubes (nm) under high-pressure mercury lamp illumination apparent rate constant k (min-1) correlation coefficient R2 under tungsten-halogen lamp illumination apparent rate constant k (min-1) correlation coefficient R2. It is worth noting that the k values are not remarkably different from each other while using the same light source. This result suggests that for a given nanotube length, the influence of the tube diameter on the photocatalytic efficiency of nanotube array film is slight. The possible reason may be on the one hand that the specific surface area of TiO2 nanotubes array is decreased with increasing of the diameter of nanotubes, resulting in a negative effect on photocatalytic activity. On the other hand, the increase of light transmittance with the increasing of pore size may have a positive effect on photocatalytic activity (40). Thus, the apparent rate constants are slightly affected by the diameter of nanotubes, if the thickness of the TiO2 film is kept the same
- We gratefully acknowledge the financial support from the National Natural Science Foundation of China (50571085), and Technical Program of Fujian Province (2005HZ01-3)
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