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Hydrothermal Preparation and Modification of BiVO4and Their Photocatalytic Performance under Visible Light

Author: GongZuo
Tutor: ZhangXiuFang
School: Dalian University of Technology
Course: Environmental Science
Keywords: BiVO4particle hydrothermal method heterojunction visible light RhB
CLC: X505
Type: Master's thesis
Year: 2011
Downloads: 78
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Abstract


Environment pollution is the great problem and challenge for the entire world. More andmore scientists are concentrating on how to use solar light to photocatalyze poisonousmaterials, decompose the harmful contaminations, purify the water and eliminate the airpollution and so on, because the photocatalysts with the visible light response can transformsolar energy into chemical energy directly. In recent years, BiVO4has been recognized as aphotocatalyst for water splitting and pollutant degradation under visible light irradiation.Bi2WO6/BiVO4with heterojunction structure has been synthesized and the compositewere characterized by X-ray diffraction （XRD） and UV-Visible diffuse reflectance spectra.RhB, which is a common pollutant in industry effluent, was chosen as a probe to testphotocatalytic activities of the photocatalysts. In this dissertation, the following several partsof work have been done:（1） Nanometer BiVO4particles were synthesized by hydrothermal method by usingBi（NO3）35H42O and NH44VO3as raw materials. The influence of various parameters such asthe hydrothermal temperature, the pH4of the precursor and the reaction time has been studied,and the obtained optimum fabrication technical conditions were180oC of hydrothermaltemperature, the pH4=7of the precursor, and the reaction time of hydrothermal is24h. TheXRD patterns revealed that the BiVO4sample was monoclinic scheelite structure. UV-visiblediffuse reflection spectra indicated that the BiVO4had a great absorption in the visible lightregion. The band gap of BiVO4was2.46eV. When the quantity of BiVO4is3g·L-1and theoriginal concertration of Rhodamine B is10mg·L-1, the RhB degradation rate with the BiVO4is about92.2%for5h under visible light irradiation.（2） The Bi2WO6was coated on the BiVO4particles and a couple Bi2WO6/BiVO4photocatalyst with heterojunction structure was synthesized. The XRD result indicated thatthe Bi2WO6was loaded on the BiVO4, and there was no obvious difference between the bandgap absorption edges of the BiVO4and Bi2WO6/BiVO4. It was found that the RhBdegradation rate of the Bi2WO6/BiVO4with the3.0%loading rate was2.7times as great asthat of the BiVO4by the photocatalytic measurements.The enhanced photocatalytic performance could be attributed to the heterojunction structure of the Bi2WO6/BiVO4. Whenthe composite was illuminated, the photogenerated electrons in the BiVO4transfer from theconduction band of BiVO4to the Bi2WO6due to the lower conduction band level of Bi2WO6.Meanwhile, the photogenerated holes in the Bi2WO6transfer from the Bi2WO6to BiVO4because of the higher valence level of BiVO4. Therefore the recombination of electron-holepairs is restrained and more electrons and holes can transfer to the surface of the compositeand join in the surface reaction. So the photocatalytic activity can be enhanced.Herein, the Bi2WO6/BiVO4photocatalyst with heterojunction structure was preformedhigh photocatalytic activities under visible light irradiation. And it has potential in purificationof the pollutants by its great photocatalytic activities.

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CLC: > Environmental science, safety science > Environmental pollution and its prevention > General issues > Environmental pollution control methods and equipment
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