Preparation and characterization of heterojunction semiconductor YFeO 3 /TiO 2 with an enhanced photocatalytic activity
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FeO3/TiO2 heterojunction semiconductors were prepared by the milling–annealing method. Effects of structure and surface phase by annealing temperature and TiO2 weight content were investigated. The physical and photophysical properties of heterojunction semiconductors were characterized by x-ray diffraction (XRD), UV-visible diffraction (UV-vis/DRS), and x-ray photoelectron spectroscopy (XPS), N2 adsorption. YFeO3 is presented as p-type semiconductor and disperses on the surface of n-type TiO2 to constitute a heterojunction composite. Results show that the presence of p–n junction not only has visible light harvesting but potential force for hole–electron pair separation. A preliminary investigation of photodegradation effect on Orange II showed that YFeO3/TiO2 heterojunction semiconductors exhibited better photocatalytic properties than the single phase of YFeO3 or TiO2. The ideal heterojunction semiconductor composition was o (TiO2) = 0.9 sample annealed at 600 C. The mechanism of the electric-field-driven electron–hole separation initiated by the chemically bonded p–n heterojunction and enhanced photocatalytic activity were discussed.
I. INTRODUCTION
It is known that the p–n junction has been widely used as a basic element in various semiconductor devices, such as photovoltaic cells and photocatalyst. The formation of p–n composite photocatalyst could lead to an efficient electron–hole separation that minimizes the energy-wasteful electron–hole recombination. There are papers about the heterojunctions composed of Cu2O,1 Co3O4,2 and NiO3 as p-type semiconductor and TiO2,4 ZnO,5 CdS,6 and SrTiO37 as n-type semiconductor. In fact, the behavior of p–n junctions made of perovskite oxides that experience a complex process is also an interesting issue. Perovskite oxides is a kind of novel photocatalyst and has been widely studied.8,9 YFeO3 is an important p-type perovskite semiconductor and has a direct band gap of 2.6 eV,10 which makes it a promising material for the conversion of solar energy into electrical or chemical energy. So, n-TiO2 coupled with p-YFeO3 will probably make the adsorption spectrum extend to longer wavelength and photocatalytic activity more improved. In the present work, p-YFeO3/n-TiO2 heterojunction semiconductors have been prepared by direct physical mixture of two components and then annealed at different temperature. The influence of annealing temperature, TiO2 weight content on surface structure, a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0016
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http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 1, Jan 2010 Downloaded: 21 Feb 2015
and photocatalytic activity of p-YFeO3/n-TiO2 heterojunction semiconductors, along with the detailed discussion on their characteristics and roles in the photocatalysis process were investigated. II. EXPERIMENTAL A. Preparation of YFeO3/TiO2 composite catalysts
All chemicals used in this work were analytical grade and were used without further purification. Distilled water was used in all experi
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