Preparation and visible-light photocatalyst activity of nanometric-sized TiO 2-x N y powders from a two-microemulsion pr
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Wen-Chung Lin Department of Environmental Engineering, Kun Shan University, Tainan 710, Taiwan, Republic of China
Chunhui Yang Department of Applied Chemistry, Harbin Institute of Technology, Harbin 150001, People’s Republic of China
Zen-Ja Chung Chemical Engineering Division, Institute of Nuclear Energy Research, Lungtan, Taoyuan 325, Taiwan, Republic of China
I-Lun Huang Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 807, Taiwan, Republic of China (Received 8 January 2009; accepted 22 April 2009)
Nanometric-sized nitrogen-doped titanium oxide (TiO2-xNy) powders were synthesized by the two-microemulsion technology. The dried precursor precipitate was characterized by differential thermal analysis/thermogravimetric analysis, Raman spectroscopy, transmission electron microscopy, Brunauer-Emmet-Teller surface area analyzer, and x-ray photoelectron spectrometer (XPS), and the mechanisms for the evolution of TiO2-xNy powders in this process were proposed and discussed in the context of the microstructure. It shows that a higher pH value solution results in obtaining a small size and much more homogeneous TiO2-xNy powder after calcinations. The powder prepared from a solution of pH 10–11 and calcined at 500 C has a particle size of 4–6 nm with a specific surface area of 160 m2/g and exhibits a pure phase of anatase containing 5 mol% of N evidenced by XPS. However, the nanometric-sized TiO2-xNy powder shows the photocatalytic degradation of methylene blue solution effectively by exposing the powders in aqueous solution under visible light. I. INTRODUCTION
Anatase TiO2 nanometric-sized materials have been applied in green environmental applications, such as the photoelectrochemical solar cell,1 photocatalyst for water splitting,2 and wastewater degradation.3 Recently, there has been an increased interest in studies of treating the suspension system of nanometric-sized anatase TiO2 powders, because of its relatively wider band gap property and high activity.4 Preparation of nanometric-sized powders is much more difficult than that of micrometric-sized particles. Among the various suggested techniques, the precipitation of precursor from the solution is one of the most realizable techniques because of its simplicity, safety, and low cost.5 Nevertheless, the conventional aqueous precipitation a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2009.0301
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J. Mater. Res., Vol. 24, No. 8, Aug 2009 Downloaded: 16 Mar 2015
method often produces irregular-shaped powders with a wide size distribution. In recent years, the microemulsion method6 has been studied and used widely as a key technique to synthesize oxide nanometric-sized powders. Chhabra et al.7 produced a monodispersed high-purity TiO2 particle using monodispersed aqueous droplets of water-in-oil microemulsions as microreactors. The most popular methods for the preparation of TiO2 particles reported in literature are based
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