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为了探索影响Bi2WO6光催化性能的内在机制，采用密度泛函理论（DFT）计算和实验研究了非化学计量和氧空位对Bi2WO6晶体结构、电子结构和显微结构的影响.采用溶剂热法合成了具有氧空位的非化学计量BixWO6（x=1.81，1.87，1.89，1.92，2.01）光催化剂.DFT计算结果表明，氧空位的存在可显著减小Bi2WO6的带隙，有利于光生电子的生成.实验结果表明，当Bi元素的含量小于化学计量比时，Bi2WO6的晶体结构发生了微小变形，Bi元素含量对Bi2WO6的显微结构影响不大，但会影响产品氧空位的含量和光吸收性能，并有效抑制电子空穴的复合.Bi1.89WO6产品的光催化性能最佳，可见光照射180 min后，可降解98%的罗丹明B.采用适当方法，使产品具有氧空位和非化学计量是获得高光催化活性材料的一种有效方法.Semiconductor photocatalyst Bi2WO6 has an extensive application prospect in organic contaminant degradation.But its energy band is relatively large and the recombination rate of photon-generated carriers is high,which prohibit its rapid development and applications.Many methods such as ion doping,non-stoichiometry,semiconductor heterojunction have been used to improve the photocatalytic activity of Bi2WO6.But the improvement mechanism is still not very clear.In this paper,by using first principle density functional theory (DFT) calculation,we study the influences of oxygen vacancy on the bond length,charge population,band structure,defect formation energy,and density of states of Bi2WO6.On the basis of DFT calculation results,different non-stoichiometric BixWO6 (x=1.81,1.87,1.89,1.92,2.01) products with oxygen vacancies are synthesized through the solvothermal method.The products are characterized by X-ray diffraction,scanning electron microscopy,X-ray photoelectron spectroscopy,UV-vis diffuse reflectance spectra photoluminescence spectroscopy,and X-ray Fluorescence.The effects of non-stoichiometric Bi element on crystal structure,chemical composition,the number of oxygen vacancies,microstructure,and photocatalytic properties are investigated and the improvement mechanism of the photocatalytic property is explored.The DFT calculation results reveal that the formation energies of Bi16W8O48 are different for the three kinds of oxygen vacancies and the bond lengths of Bi–O and W–O with one oxygen vacancy decrease a little and the bond populations decrease significantly for the Bi and W atoms adjacent to oxygen vacancy.The existence of oxygen vacancies forms O 2p impurity energy level and significantly reduces the band gap of Bi2WO6. The absorption spectra indicate that the absorption intensities in the visible light increase for the Bi16W8O48 cell with oxygen vacancy defects increasing.The DFT calculation results show that oxygen vacancy defects promote the formation of photoelectrons and enhance the photocatalytic performance of Bi2WO6.The experimental results show that non-stoichiometric Bi element makes the crystal structure slightly deformed and significantly affects the number of oxygen vacancies,photoabsorption capacity and the electron-hole recombination of Bi2WO6.The Bi1.89WO6 product has the best photocatalytic performance,and the rhodamine B is degraded by 98% after being irradiated for 180 min by visible light.Therefore,non-stoichiometric semiconductor with oxygen vacancy is testified to be an efficient method of obtaining high activity photocatalyst.
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Keywords:
- Bi2WO6 /
- oxygen vacancy /
- crystal structure /
- photocatalyst materials
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[1] Fujishima A, Honda K 1972 Nature 238 37
[2] Jing L, Sun X 2003 Sol. Energy Mater. Sol. Cells 79 133
[3] Liu Y, Yu L, Wei Z G, Pan Z C, Zou Y D, Xie Y H 2013 Chem. J. Chin. Univ. (in Chinese) [刘月, 余林, 魏志钢, 潘湛昌, 邹燕娣, 谢英豪 2013 高等学校化学学报 34 434]
[4] Carp O, Huisman C L, Reller A 2004 Prog. Solid State Chem. 32 33
[5] Yang K, Dai Y, Huang B 2008 Chem. Phys. Lett. 456 71
[6] Wang P, Huang B, Lou Z 2010 Chem. Eur. J. 16 538
[7] Kubacka A, Fern Ndezgarc A M, Col N G 2012 Chem. Rev. 112 1555
[8] Kudo A, Omori K, Kato H 1999 J. Am. Chem. Soc. 121 11459
[9] Fu H, Pan C, Yao W 2005 J. Phys. Chem. B 109 22432
[10] Zhang L, Wang W, Yang 2006 J. Appl. Catal. A 308 105
[11] Lai K, Zhu Y, Lu J 2013 Comput. Mater. Sci. 67 88
[12] Zeng D W, Xie C S, Zhu B L 2003 Mater. Sci. Eng. B 104 68
[13] Zhang L, Wang W, Zhou L 2007 Small 3 1618
[14] Zhang Z, Wang W, Gao E 2012 J. Phys. Chem. C 116 25898
[15] Bhattacharya C, Lee H C, Bard A J 2013 J. Phys. Chem. C 117 9633
[16] Sun Z X, Li X F, Guo S, Wang H Q, Wu Z B 2013 J. Colloid Interf. Sci. 412 31
[17] Kuo T J, Lin C N, Kuo C L, Huang M H 2007 Chem. Mater. 19 5143
[18] Wang J C, Liu P, Fu X Z, Li Z H, Han W, Wang X X 2009 Langmuir. 25 1218
[19] Zheng Y H, Chen C Q, Zhan Y Y, Lin X Y, Zheng Q, Wei K M, Zhu J F, Zhu Y J 2007 Inorg. Chem. 46 6675
[20] Gong X Q, Selloni A, Batzil M 2006 Nat. Mater. 5 665
[21] Zhang Z, Wang W, Gao E, Shang M, Xu J 2011 J. Hazard Mater. 196 255
[22] Nie Z, Ma D, Fang G Y, Chen W, Huang S M 2016 J. Mater. Chem. A 4 2438
[23] Mcdowell N A, Knight K S 2006 Chem. Eur. J. 12 1493
[24] Perdew J P, Ruzsinszky A, Csonka G I 2008 Phys. Rev. Lett. 101 136406
[25] Lu Q, Hua L G, Chen Y L 2015 J. Inorg. Mater. 30 413 (in Chinese) [卢青, 华罗光, 陈亦琳 2015 无机材料学报 30 413]
[26] Zhou B, Zhao X, Liu H 2010 Appl. Catal. B 99 214
[27] Sun S B, Chang X T, Li Z J 2012 Mater. Charact. 73 130
[28] Lin Z, Wang W, Liu S 2006 J. Mol. Catal. A 252 120
[29] Wu J, Duan F, Zheng Y 2007 J. Phys. Chem. C 111 12866
[30] Ding X, Zhao K, Zhang L 2014 Environ. Sci. Technol. 48 5823
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