电化学法研究La-F两步共掺杂纳米TiO2的催化机理

Catalytic Mechanism of La-F Two-Step Co-Doping TiO2 by Electrochemical Method

以钛酸四丁酯、硝酸镧和氟化钠等为原料,采用原位掺杂方式制备了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,也使TiO2的禁带宽度降低。两步共掺杂样品中TiO2与Lax-Fy-TiO2间形成异质结,可有效降低光生电子-空穴的复合,提高载流子浓度。当La和F的掺杂比为1.5%和10%时,两步共掺杂样品的载流子浓度为1.5×10^20 cm^-3,120min时可见光下对亚甲基蓝降解率达到96%,为同等条件下纯TiO2的2.6倍。

La-F two-step co-doping TiO2 photocatalysts were prepared by in-situ doping method using tetrabutyl titanate, lanthanum nitrate, and sodium fluoride as the main materials. The prepared samples were characterized by XRD, SEM, XPS and UV-Vis DRS. The photocatalytic property under visible light was evaluated by the photo degradation of methylene blue. The results show that all the samples exhibit homogeneous anatase TiO2. La-F co-doping leads to larger lattice distortion and refines the grain size of TiO2. The morphology of samples are spherical in shape but the aggregation degree is different, and the two-step co-doping could aggravate the reunion of the sample particles because of the difference of their preparation process. The La-F co-doping also could cause the band gap decreasing accordingly. Simultaneously, n-n heterojunction forms between TiO2 and Lax-Fy-TiO2 in the two-step co-doping TiO2 samples, and reduces the recombination of photo-generated electron and hole effectively, and then enhances the charge carrier concentration. When the doping ratio of La and F in the two-step La-F co-doping sample are 1.5% and 10%, the carrier concentration reaches 1.5×10^20 cm^-3, and the degradation rate of methylene blue under visible light is 96% at 120 min, which is 2.6 times of that of pure TiO2 under the same condition.