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电化学法研究La-F两步共掺杂纳米TiO2的催化机理
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1.内蒙古科技大学材料与冶金学院;2.北京科技大学冶金与生态工程学院

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国家自然科学基金资助(项目号51474133), 内蒙古自然科学基金(项目号2015MS0571)


Study on the catalytic mechanism of La-F two-step co-doping TiO2 by electrochemical method
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School of Materials and Metallurgy,Inner Mongolia University of Science and Technology

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    摘要:

    以钛酸四丁酯、硝酸镧和氟化钠等为原料,采用原位掺杂的方式制备了La-F两步共掺杂TiO2光催化剂。通过XRD、SEM、XPS和UV-Vis对样品进行了表征,并对样品进行了光催化性能及电化学交流阻抗的测试。结果表明所制样品均为锐钛矿型TiO2,La-F共掺杂使TiO2的晶格发生了较大畸变且晶粒得到了细化,两步共掺杂会加剧样品颗粒间的团聚,同时两步共掺杂也使TiO2的吸收带边发生红移,禁带宽度降低。两步共掺杂样品中TiO2与Lax-Fy-TiO2之间形成的n-n异质结,由于二者费米能级不同而形成的内建电场,对半导体内部电子起到定向的迁移作用,从而有效降低光生电子-空穴的复合,提高载流子浓度。当La和F的掺杂比例分别为1.5%和10%时,两步共掺杂样品的载流子浓度为1.5×1020/cm-3,对亚甲基蓝表现出优异的可见光降解效果,120min降解率达到96%,为同等条件下纯TiO2的2.6倍。

    Abstract:

    La-F two-step co-doping TiO2 photocatalysts have been prepared by the means of in-situ doping method using tetrabutyl titanate, lanthanum nitrate, and sodium fluoride as the main materials. The prepared samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). The photocatalytic property under visible light was evaluated by the photo degradation of Methylene blue (MB). In addition, by means of electrochemical impedance spectroscopy (EIS), the carriers concentrations of co-doping samples were calculated through Mott-schottky equation to discuss the mechanism of two-step co-doping. The results demonstrated that all the samples exhibit homogeneous anatase TiO2, La-F co-doping led to larger lattice distortion and refined the grain size of TiO2. SEM results showed that the morphology of samples were spherical in shape but the aggregation degree was different with each other, and the two-step co-doping could aggravate the reunion of the sample particles compared with that of the co-doping samples because of the difference of their preparation process. The La-F co-doping also could cause the absorption band of samples shifted towards the longer wavelength side and the band gap decreased accordingly at the same time. Simultaneously, n-n heterojunction was formed between TiO2 and Lax-Fy-TiO2 in the two-step co-doping TiO2 samples. The build-in internal electric field caused by the different Fermi level of TiO2 and Lax-Fy-TiO2 played an important role in the directional migration of charges in the two-step co-doping samples, and reduced its recombination of photo-generated electron and hole effectively, and then enhanced the charge carrier concentration. As showed in the electrochemical impedance results, when the doping ratio of La and F in the two-step La-F co-doping sample were 1.5% and 10% respectively, the carrier concentration reached 1.5×1020/cm-3, and it’s degradation rate of methylene blue under visible light is 96% at 120min, which was 2.6 times of pure TiO2 on the same condition.

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王瑞芬,宋金玲,李裕,安胜利,王福明.电化学法研究La-F两步共掺杂纳米TiO2的催化机理[J].稀有金属材料与工程,2019,48(8):2562~2567.[Wang Ruifen, Song Jinling, Li Yu, An Shengli, Wang Fuming. Study on the catalytic mechanism of La-F two-step co-doping TiO2 by electrochemical method[J]. Rare Metal Materials and Engineering,2019,48(8):2562~2567.]
DOI:10.12442/j. issn.1002-185X.20180230

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  • 收稿日期:2018-03-14
  • 最后修改日期:2018-04-20
  • 录用日期:2018-04-26
  • 在线发布日期: 2019-09-05
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