MgAl-LDHs/TiO_(2)复合光催化剂的制备及光催化性能

Preparation and Photocatalytic Performance of MgAl-LDHs/TiO_(2) Composite Photocatalyst

基于水滑石(LDHs)的记忆效应,合成了MgAl-LDHs/TiO_(2)复合材料。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、光致发光光谱(PL)等研究手段对材料进行表征。以亚甲基蓝(MB)为降解物,研究MgAl-LDHs/TiO_(2)在模拟太阳光下的光催化性能并优化了反应条件;基于第一性原理,从原子尺度出发计算复合体系的能带结构和态密度;探究了光催化过程中的主要活性基团并提出了可能的光催化反应机理。结果表明:MgAl-LDHs/TiO_(2)中TiO_(2)组分的团聚现象有所改善,与单一TiO_(2)相比,复合材料吸附能力极大增强,光催化活性明显提高。当LDHs质量占比为50%、焙烧温度为400℃时,催化剂在40 min内对亚甲基蓝的降解率达到95.3%。光催化反应过程中的主要活性基团为h+和·OH,MgAl-LDHs/TiO_(2)为间接带隙半导体,模拟计算所得的禁带宽度为1.67 eV,光响应原理是电子从VB中的O 2p转移到CB中杂化的Ti 3d和Al 3p中。

Based on the memory effect of hydrotalcite(LDHs),MgAl-LDHs/TiO_(2) composites were synthesized.The materials were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM)and photoluminescence spectroscopy(PL).Using methylene blue(MB)as degradation material,the photocatalytic performance of MgAl-LDHs/TiO_(2) under simulated sunlight was studied and the reaction conditions were optimized.Based on first principles theory,the band structure and state density of the composite system were calculated at atomic scale.The main active groups in the photocatalytic process were investigated and the possible photocatalytic reaction mechanism was proposed.The results showed that the agglomeration phenomenon of TiO_(2)in MgAl-LDHs/TiO_(2) composites was improved,the adsorption capacity of the composite was greatly enhanced,and the photocatalytic activity of the composite was significantly improved compared with that of TiO_(2).The degradation rate of methylene blue reached 95.3%within 40 min when the mass ratio of LDHs was 50%and the calcination temperature was 400℃.The main active groups in the photocatalytic reaction process are h+and·OH.The bandgap obtained by MgAl-LDHs/TiO_(2) simulation calculation is 1.67 eV which is an indirect bandgap semiconductor.The photoresponse principle is transferred from O 2p in VB to hybrid Ti 3d and Al 3p in CB.