Enhanced Photocatalytic Performance of Nitrogen-Doped TiO2 Nanotube Arrays Using a Simple Annealing Process
by
Phuoc Huu Le 1,2,*, Le Trung Hieu 3
, Tu-Ngoc Lam 3, Nguyen Thi Nhat Hang 4, Nguyen Van Truong 5, Le Thi Cam Tuyen 1,2, Pham Thanh Phong 2,6 and Jihperng Leu 3,*
Phuoc Huu Le 1,2,*, Le Trung Hieu 3, Tu-Ngoc Lam 3, Nguyen Thi Nhat Hang 4, Nguyen Van Truong 5, Le Thi Cam Tuyen 1,2, Pham Thanh Phong 2,6 and Jihperng Leu 3,*
1
Ceramics and Biomaterials Research Group, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
2
Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
3
Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30049, Taiwan
4
Faculty of Natural Sciences, Thu Dau Mot University, 6 Tran Van On Street, Thu Dau Mot City 820000, Vietnam
5
Faculty of Fundamental Sciences, Thai Nguyen University of Technology, Thai Nguyen 24000, Vietnam
6
Laboratory of Magnetism and Magnetic Materials, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City 700000, Vietnam
*
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.
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Keywords:
N-doped TNAs; two-step anodization; photocatalytic activity; thermal annealing; modified TiO2; band gap
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited
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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