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Open AccessArticle

Enhanced Photocatalytic Performance of Nitrogen-Doped TiO2 Nanotube Arrays Using a Simple Annealing Process

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Ceramics and Biomaterials Research Group, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
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Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
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Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30049, Taiwan
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Faculty of Natural Sciences, Thu Dau Mot University, 6 Tran Van On Street, Thu Dau Mot City 820000, Vietnam
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Faculty of Fundamental Sciences, Thai Nguyen University of Technology, Thai Nguyen 24000, Vietnam
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Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
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Authors to whom correspondence should be addressed.
Micromachines 2018, 9(12), 618; https://doi.org/10.3390/mi9120618
Received: 10 September 2018 / Revised: 8 November 2018 / Accepted: 20 November 2018 / Published: 24 November 2018
Nitrogen-doped TiO2 nanotube arrays (N-TNAs) were successfully fabricated by a simple thermal annealing process in ambient N2 gas at 450 °C for 3 h. TNAs with modified morphologies were prepared by a two-step anodization using an aqueous NH4F/ethylene glycol solution. The N-doping concentration (0–9.47 at %) can be varied by controlling N2 gas flow rates between 0 and 500 cc/min during the annealing process. Photocatalytic performance of as-prepared TNAs and N-TNAs was studied by monitoring the methylene blue degradation under visible light (λ ≥ 400 nm) illumination at 120 mW·cm−2. N-TNAs exhibited appreciably enhanced photocatalytic activity as compared to TNAs. The reaction rate constant for N-TNAs (9.47 at % N) reached 0.26 h−1, which was a 125% improvement over that of TNAs (0.115 h−1). The significant enhanced photocatalytic activity of N-TNAs over TNAs is attributed to the synergistic effects of (1) a reduced band gap associated with the introduction of N-doping states to serve as carrier reservoir, and (2) a reduced electron‒hole recombination rate. View Full-Text
Keywords: N-doped TNAs; two-step anodization; photocatalytic activity; thermal annealing; modified TiO2; band gap N-doped TNAs; two-step anodization; photocatalytic activity; thermal annealing; modified TiO2; band gap
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MDPI and ACS Style

Le, P.H.; Hieu, L.T.; Lam, T.-N.; Hang, N.T.N.; Truong, N.V.; Tuyen, L.T.C.; Phong, P.T.; Leu, J. Enhanced Photocatalytic Performance of Nitrogen-Doped TiO2 Nanotube Arrays Using a Simple Annealing Process. Micromachines 2018, 9, 618.

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