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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.

No MeSH data available.


SEM images of the NT powders. (a) SEM morphology of the as-prepared NT powders. SEM images of the NT powders annealed at (b) 450°C and (c) 750°C.
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Fig2: SEM images of the NT powders. (a) SEM morphology of the as-prepared NT powders. SEM images of the NT powders annealed at (b) 450°C and (c) 750°C.

Mentions: The SEM images of the as-formed NT powders showed a tubular morphology. The tube arrays were separated into isolated tubes, and the entire tube was broken into several segments. Figure 2a shows that the tube wall consisted of TiO2 nanocrystallites. After annealing at 450°C, loosely packed tube agglomerates were observed (Figure 2b). By further increasing the crystallization temperature of the NT powders, the tubular structure was well preserved, with slight structure changes. The SEM image of the samples annealed at 750°C is shown in Figure 2c. However, when NTs were dispersed in DI water, changes in structural integrity were more apparent. Heat treatment at 750°C resulted in the collapse of the NT structure (Additional file 1: Figure S1). The tubes were severely sintered and consolidated, and the tubular architecture gradually disappeared. The changes might probably be due to the water-induced tube wall modification as has been previously reported, leading to a hybrid structure [29]. In addition, to recycle NT powder as a photocatalyst, it was immobilized onto an FTO substrate. From the cross-sectional view in Additional file 1: Figure S2, a uniform, dense, and randomly packed TiO2 film was tightly connected to the substrate, promising for use in photocatalytic reactions.Figure 2


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)

SEM images of the NT powders. (a) SEM morphology of the as-prepared NT powders. SEM images of the NT powders annealed at (b) 450°C and (c) 750°C.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4385124&req=5

Fig2: SEM images of the NT powders. (a) SEM morphology of the as-prepared NT powders. SEM images of the NT powders annealed at (b) 450°C and (c) 750°C.
Mentions: The SEM images of the as-formed NT powders showed a tubular morphology. The tube arrays were separated into isolated tubes, and the entire tube was broken into several segments. Figure 2a shows that the tube wall consisted of TiO2 nanocrystallites. After annealing at 450°C, loosely packed tube agglomerates were observed (Figure 2b). By further increasing the crystallization temperature of the NT powders, the tubular structure was well preserved, with slight structure changes. The SEM image of the samples annealed at 750°C is shown in Figure 2c. However, when NTs were dispersed in DI water, changes in structural integrity were more apparent. Heat treatment at 750°C resulted in the collapse of the NT structure (Additional file 1: Figure S1). The tubes were severely sintered and consolidated, and the tubular architecture gradually disappeared. The changes might probably be due to the water-induced tube wall modification as has been previously reported, leading to a hybrid structure [29]. In addition, to recycle NT powder as a photocatalyst, it was immobilized onto an FTO substrate. From the cross-sectional view in Additional file 1: Figure S2, a uniform, dense, and randomly packed TiO2 film was tightly connected to the substrate, promising for use in photocatalytic reactions.Figure 2

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.