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Anatase TiO2 nanotube powder film with high crystallinity for enhanced photocatalytic performance.

Lin J, Liu X, Zhu S, Liu Y, Chen X - Nanoscale Res Lett (2015)

Bottom Line: Compared to free-standing NT array films, the powder-type NTs can be easily fabricated in a cost-effective way.The results showed that with increasing annealing temperature, the photocatalytic decomposition rate was gradually enhanced, and the NT powder electrode annealed at 650°C showed the highest photoactivity.These findings indicate that the better photocatalytic activity was due to the significantly improved crystallinity of anatase anodic NTs in powder form, resulting in a low density of crystalline defects.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Shanghai University of Electric Power, 2103 Pingliang Road, Shanghai, 200090 China.

ABSTRACT
We report on the synthesis of TiO2 nanotube (NT) powders using anodic oxidation and ultrasonication. Compared to free-standing NT array films, the powder-type NTs can be easily fabricated in a cost-effective way. Particularly, without the substrate effect arising from underlying Ti metals, highly crystallized NT powders with intact tube structures and pure anatase phase can be obtained using high-temperature heat treatment. The application of NTs with different crystallinity for the photocatalytic decomposition of methylene blue (MB) was then demonstrated. The results showed that with increasing annealing temperature, the photocatalytic decomposition rate was gradually enhanced, and the NT powder electrode annealed at 650°C showed the highest photoactivity. Compared to typical NTs annealed at 450°C, the rate constant increased by 2.7-fold, although the surface area was 21% lower. These findings indicate that the better photocatalytic activity was due to the significantly improved crystallinity of anatase anodic NTs in powder form, resulting in a low density of crystalline defects. This simple and efficient approach is applicable for scaled-up water purification and other light utilization applications.

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Photocatalytic performance and rate constant. (a) Time-dependent MB concentration showing the photocatalytic decomposition kinetic behavior of the NT powders obtained at various annealing temperatures of 450°C, 550°C, 650°C, and 750°C. (b) The photocatalytic rate constant.
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Fig5: Photocatalytic performance and rate constant. (a) Time-dependent MB concentration showing the photocatalytic decomposition kinetic behavior of the NT powders obtained at various annealing temperatures of 450°C, 550°C, 650°C, and 750°C. (b) The photocatalytic rate constant.

Mentions: To investigate the photodegradation of MB solution by the annealed NT powder electrodes, variations in MB concentration as a function of illumination time were monitored (Figure 5a). In the absence of the NT photocatalyst, the MB solution showed negligible self-degradation. MB molecules decomposed faster with increasing annealing temperatures within the specific range of 450°C to 650°C, indicating that NTs of higher crystallization possessed better photocatalytic activity. In addition, the 750°C sample showed a lower photocatalytic activity. The linear plot in Figure 5a indicates that the photocatalysis process followed a quasi-first-order kinetics and thereby can be presented as ln(C0/C) = ln(A0/A) = kt. Here, C0 is the initial MB concentration, and C is the concentration after irradiation for time t. A0 and A are the corresponding absorbances. k is a first-order rate kinetic constant, which well represents the photocatalytic activity. A comparison of the rate constant values at different temperatures is presented in Figure 5b.Figure 5


Anatase TiO2 nanotube powder film with high crystallinity for enhanced photocatalytic performance.

Lin J, Liu X, Zhu S, Liu Y, Chen X - Nanoscale Res Lett (2015)

Photocatalytic performance and rate constant. (a) Time-dependent MB concentration showing the photocatalytic decomposition kinetic behavior of the NT powders obtained at various annealing temperatures of 450°C, 550°C, 650°C, and 750°C. (b) The photocatalytic rate constant.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385124&req=5

Fig5: Photocatalytic performance and rate constant. (a) Time-dependent MB concentration showing the photocatalytic decomposition kinetic behavior of the NT powders obtained at various annealing temperatures of 450°C, 550°C, 650°C, and 750°C. (b) The photocatalytic rate constant.
Mentions: To investigate the photodegradation of MB solution by the annealed NT powder electrodes, variations in MB concentration as a function of illumination time were monitored (Figure 5a). In the absence of the NT photocatalyst, the MB solution showed negligible self-degradation. MB molecules decomposed faster with increasing annealing temperatures within the specific range of 450°C to 650°C, indicating that NTs of higher crystallization possessed better photocatalytic activity. In addition, the 750°C sample showed a lower photocatalytic activity. The linear plot in Figure 5a indicates that the photocatalysis process followed a quasi-first-order kinetics and thereby can be presented as ln(C0/C) = ln(A0/A) = kt. Here, C0 is the initial MB concentration, and C is the concentration after irradiation for time t. A0 and A are the corresponding absorbances. k is a first-order rate kinetic constant, which well represents the photocatalytic activity. A comparison of the rate constant values at different temperatures is presented in Figure 5b.Figure 5

Bottom Line: Compared to free-standing NT array films, the powder-type NTs can be easily fabricated in a cost-effective way.The results showed that with increasing annealing temperature, the photocatalytic decomposition rate was gradually enhanced, and the NT powder electrode annealed at 650°C showed the highest photoactivity.These findings indicate that the better photocatalytic activity was due to the significantly improved crystallinity of anatase anodic NTs in powder form, resulting in a low density of crystalline defects.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Shanghai University of Electric Power, 2103 Pingliang Road, Shanghai, 200090 China.

ABSTRACT
We report on the synthesis of TiO2 nanotube (NT) powders using anodic oxidation and ultrasonication. Compared to free-standing NT array films, the powder-type NTs can be easily fabricated in a cost-effective way. Particularly, without the substrate effect arising from underlying Ti metals, highly crystallized NT powders with intact tube structures and pure anatase phase can be obtained using high-temperature heat treatment. The application of NTs with different crystallinity for the photocatalytic decomposition of methylene blue (MB) was then demonstrated. The results showed that with increasing annealing temperature, the photocatalytic decomposition rate was gradually enhanced, and the NT powder electrode annealed at 650°C showed the highest photoactivity. Compared to typical NTs annealed at 450°C, the rate constant increased by 2.7-fold, although the surface area was 21% lower. These findings indicate that the better photocatalytic activity was due to the significantly improved crystallinity of anatase anodic NTs in powder form, resulting in a low density of crystalline defects. This simple and efficient approach is applicable for scaled-up water purification and other light utilization applications.

No MeSH data available.


Related in: MedlinePlus