Effects of Synthesis Conditions on the Crystalline Phases and Photocatalytic Activities of Silver Vanadates via Hydrothe
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1171-S01-08
Effects of Synthesis Conditions on the Crystalline Phases and Photocatalytic Activities of Silver Vanadates via Hydrothermal Method Chao M. Huang1, Guan T. Pan2, Lung C. Chen3, Thomas C.K. Yang2, and Wen S. Chang4 1
Department of Environmental Engineering, Kun Shan University, Yung Kang City, Taiwan
2
Department of Chemical Engineering, National Taipei University of Technology, Taipei, Taiwan
3
Department of Polymer Materials, Kun Shan University, Yung Kang City, Taiwan
4
Energy and Environmental Laboratory, Industrial Technology Research Institute, Hsinchu, Taiwan
ABSTRACT Visible-light-driven Ag3VO4 photocatalysts were successfully synthesized using low-temperature hydrothermal synthesis method. Under various hydrothermal conditions, the structures of silver vanadates were tuned by manipulating the hydrothermal time and the molar ration of silver to vanadium. X-ray diffraction (XRD) results reveal that the powders prepared in a stoichiometric ratio consisted of pure α-Ag3VO4 or mixed phases of Ag4V2O7 and α-Ag3VO4. With increasing the Ag-to-V mole ratio to 6:1, the resulting samples were identified as pure monoclinic structure α-Ag3VO4. UV-vis spectroscopy indicated that silver vanadate particles had strong visible light absorption with associated band gaps in the range of 2.2-2.5 eV. The sample synthesized in the excess silver exhibited higher photocatalytic activity than that synthesized in a stoichiometric ratio. The powder synthesized at silver-rich at 140℃ for 4 h (SHT4) exhibited the highest photocatalytic activity among all samples. The reactivity of SHT4 (surface area, 3.52 m2 g-1) on the decomposition of gaseous benzene was about 16 times higher than that of P25 (surface area, 49.04 m2 g-1) under visible light irradiation. A well developed crystallinity of Ag3VO4 of SHT 4 was considered to enhance the photocatalytic efficiency. INTRODUCTION Silver vanadates, prepared by precipitation and solid-state reactions, have been investigated to be the photocatalysts for O2 evolution [1]. Among the silver vanadates, only Ag3VO4 possessed the high visible-light photoactivity for O2 evolution from an aqueous silver nitrate solution. With a strong oxidizing potential, Ag3VO4 is expected to be good candidate in the field of photodecomposition of organic compounds. However, the high temperature and long time reaction of solid-state reaction restricts further development in industrial production [2-4]. To reduce energy consumption, exploiting low cost metal oxide catalysts with high visible-light photocatalytic activity is desirable. Hence, the synthesis of
silver vanadates using a one-step hydrothermal synthesis method is proposed in this study. The influences of the ratio of silver to vanadium as well as the hydrothermal times on the photocatalytic activities of Ag3VO4 were investigated. EXPERIMENTAL DETAILS In a typical experiment, first, 0.006 mol AgNO3 was dissolved into 60 ml of de-ionized water under stirring; an appropriate NH4VO3 was dissolved in de-ionized water to form a transparent solu
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