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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.


Schematic and images of the NT powders. (a) Schematic illustration of the fabrication process of NT powders, including (I) anodization of Ti foil to produce NT arrays and (II) ultrasonication in ethanol to disperse the as-formed NTs. (b) The amorphous NT powder obtained by collecting the dispersed NTs. (c) Crystallized NT powder after annealing.
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Fig1: Schematic and images of the NT powders. (a) Schematic illustration of the fabrication process of NT powders, including (I) anodization of Ti foil to produce NT arrays and (II) ultrasonication in ethanol to disperse the as-formed NTs. (b) The amorphous NT powder obtained by collecting the dispersed NTs. (c) Crystallized NT powder after annealing.

Mentions: It has been previously reported that for NTs grown on a Ti substrate, direct annealing to crystallinity results in severe substrate effects [24,28], resulting in the destruction of tubes and a largely decreased surface area. Herein, by ultrasonication in ethanol, the as-anodized NTs could be detached from the Ti substrate prior to usage (Figure 1a), and thus, the influence of the Ti substrate was successfully eliminated. After the removal of surface NTs, the Ti foil could be reused until the foil was completely consumed. The reaction yield each time (approximately 2 h) per cm2 area of the Ti foil was approximately 0.01 g. The as-prepared NT powder was amorphous and showed a gray color (Figure 1b). After the crystallization at 450°C, the color of the NT powder changed to white (Figure 1c). Compared to NT arrays, dispersed NT powders showed high quality, and thus, the dimension and phase of NTs could be stabilized during high-temperature crystallization, as will be discussed in the next section.Figure 1


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)

Schematic and images of the NT powders. (a) Schematic illustration of the fabrication process of NT powders, including (I) anodization of Ti foil to produce NT arrays and (II) ultrasonication in ethanol to disperse the as-formed NTs. (b) The amorphous NT powder obtained by collecting the dispersed NTs. (c) Crystallized NT powder after annealing.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig1: Schematic and images of the NT powders. (a) Schematic illustration of the fabrication process of NT powders, including (I) anodization of Ti foil to produce NT arrays and (II) ultrasonication in ethanol to disperse the as-formed NTs. (b) The amorphous NT powder obtained by collecting the dispersed NTs. (c) Crystallized NT powder after annealing.
Mentions: It has been previously reported that for NTs grown on a Ti substrate, direct annealing to crystallinity results in severe substrate effects [24,28], resulting in the destruction of tubes and a largely decreased surface area. Herein, by ultrasonication in ethanol, the as-anodized NTs could be detached from the Ti substrate prior to usage (Figure 1a), and thus, the influence of the Ti substrate was successfully eliminated. After the removal of surface NTs, the Ti foil could be reused until the foil was completely consumed. The reaction yield each time (approximately 2 h) per cm2 area of the Ti foil was approximately 0.01 g. The as-prepared NT powder was amorphous and showed a gray color (Figure 1b). After the crystallization at 450°C, the color of the NT powder changed to white (Figure 1c). Compared to NT arrays, dispersed NT powders showed high quality, and thus, the dimension and phase of NTs could be stabilized during high-temperature crystallization, as will be discussed in the next section.Figure 1

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.