Enhanced visible photocatalytic activity of nitrogen doped single-crystal-like TiO 2 by synergistic treatment with urea
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Zengying Zhaoa) and Hamukwaya Shindume Lomboleni School of Science, China University of Geosciences, Beijing 100083, People’s Republic of China
Hongwei Huang School of Materials Science and Technology, China University of Geosciences, Beijing 100083, People’s Republic of China
Zhijian Peng School of Engineering and Technology, China University of Geosciences, Beijing 100083, People’s Republic of China (Received 8 August 2016; accepted 8 November 2016)
N-doped single-crystal-like TiO2 is claimed to be a very promising material among various catalytic. In this paper, N-doped single-crystal-like TiO2 (N-S-TiO2) samples were firstly prepared by molten salt method with urea and mixed nitrates as synergistic doping agents, therein, the mixed nitrates works also as a morphology modifier to form a single-crystal-like structure in the sample. The nitrogen content in the N-S-TiO2 sample could be improved because of the adding of NaNO3 and KNO3 mixed nitrates compared with using urea as a single nitrogen source. UV–Vis absorption spectroscopy analysis indicated that the nitrogen doped TiO2 has a red shift of the light absorption edge. The presence of N–O bonds on the surface of the N-S-TiO2 samples could be confirmed by x-ray photoelectron spectroscopy. The degradation efficiency of N-S-TiO2 to methylene blue under visible light is the best compared with different TiO2 samples without the treatment of mixed nitrates.
I. INTRODUCTION
Photocatalysis technology has been considered as one of the best selections to solve the issues of energy source and environmental pollution.1,2 In literature, titanium dioxide (TiO2) was found to display photocatalytic activities under UV light by Fujishima and Honda in 1972.3 Now it becomes one of the most efficient and widely used materials in this field.4 TiO2 has many advantages including low cost, nontoxicity, long-term stability, and high photoactivity.5–10 However, there are still some obstacles toward its practical applications in photocatalysis. One of the difficulties to use TiO2 in practice is that the most TiO2 photocatalysts are polyporous, and usually composed of building units with different crystallographic orientations, the majority of which exhibit polycrystalline structure.11 The interparticle boundaries related to defects generally may act as recombination centers of the formed electron–hole pairs Contributing Editor: Xiaobo Chen a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.448
during photocatalysis, leading to the decrease of the activity of polycrystalline structure photocatalysts. Therefore, single-crystal-like structure TiO2 can effectively reduce the amount of defects of internal crystal, and enhance transfer and separation ability of charge carriers, finally improving photocatalytic activity of photocatalysts.12,13 Another shortcoming of TiO2 is its wide band gap of 3.2 eV, which means that it can only be activated by ultraviolet (UV) radiation (with wave length below 380 nm), and lavish most part of solar energy. On the whole
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