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Efficient Charge Carrier Separation in l-Alanine Acids Derived N-TiO2 Nanospheres: The Role of Oxygen Vacancies in Tetrahedral Ti4+ Sites

School of Chemical Sciences & Technology, National Center for International Research on Photoelectric and Energy Materials, Yunnan Provincial Collaborative Innovation Center of Green Chemistry for Lignite Energy, Yunnan Province Engineering Research Center of Photocatalytic Treatment of Industrial Wastewater, The Universities’ Center for Photocatalytic Treatment of Pollutants in Yunnan Province, Yunnan University, Kunming 650091, China
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Nanomaterials 2019, 9(5), 698; https://doi.org/10.3390/nano9050698
Received: 25 March 2019 / Revised: 29 April 2019 / Accepted: 29 April 2019 / Published: 5 May 2019
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Abstract

N-doped TiO2 with oxygen vacancies exhibits many advantages for photocatalysis, such as enhanced visible light absorbency, inhibition of the photogenerated charge carrier recombination, etc. However, preparation of N-doped TiO2 with oxygen vacancies under mild conditions is still a challenge. Herein, N-doped TiO2 nanospheres with tetrahedral Ti4+ sites were synthesized by using dodecylamine as template and assisted by l-alanine acids. The obtained samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis diffuse reflectance spectra (UV–Vis DRS). It was found that the dodecylamine as a neutral surfactant controlled the structure of TiO2 spherical, while l-alanine acids provided a nitrogen source. The existence of tetrahedral Ti4+ sites in N-doped TiO2 was also confirmed. The N-doped TiO2 sample with tetrahedral Ti4+ sites exhibited significantly improved photocatalytic performance for degradation of methylene blue solution under UV light or visible light irradiation. A combined time-resolved infrared (IR) spectroscopy study reveals that the enhanced photocatalytic performance could be attributed to a large amount of photogenerated charge carriers and efficient charge separation. It is demonstrated that the shallow donor state produced by oxygen vacancies of tetrahedral Ti4+ sites can effectively promote separation of charge carriers besides capturing electrons. View Full-Text
Keywords: N-doped TiO2; tetrahedral Ti4+ sites; photocatalytic; l-alanine acids; time-resolved IR spectroscopy N-doped TiO2; tetrahedral Ti4+ sites; photocatalytic; l-alanine acids; time-resolved IR spectroscopy
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Chen, Y.; Luo, X.; Luo, Y.; Xu, P.; He, J.; Jiang, L.; Li, J.; Yan, Z.; Wang, J. Efficient Charge Carrier Separation in l-Alanine Acids Derived N-TiO2 Nanospheres: The Role of Oxygen Vacancies in Tetrahedral Ti4+ Sites. Nanomaterials 2019, 9, 698.

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