化石燃料的迅速消耗导致环境污染与能源危机日益加剧.太阳能高效利用与转换是解决该难题的有效途径之一.在众多光催化剂中,TiO2因其高催化活性、高稳定性、低毒性以及低成本等优势而普遍受到关注,但TiO2存在着带隙过宽而无法利用可见光的缺陷,严重制约了其在光催化方向的实际应用.核壳型复合纳米材料具有较大的比表面积、较高的光吸收能力以及所吸附的污染物分子易于从吸附面扩散到光致降解面等特点,而表现出较强的有机污染物吸附性能以及良好的光催化活性.以磁体材料为核将TiO2包覆于磁体表面,可以制备具有磁分离特性的磁载光催化剂.而铁酸铋作为一种在室温下同时具有铁电性和铁磁性的钙钛矿型材料,由于其较窄的带宽(2.1 eV)在可见光催化氧化方面也受到了极大的关注.本文首先通过柠檬酸自燃烧法制备了可磁性分离的BiFeO3粉体,再以水解沉淀法将TiO2包裹在BiFeO3前驱体上形成了不同质量比(1:1,1:2,2:1)的核壳结构的BiFeO3@TiO2复合粉体,并以甲基紫为例,对其在紫外光和可见光照射下的光催化性能分别展开了研究.结果表明,BiFeO3@TiO2复合粉体的光催化性能较单独的BiFeO3或TiO2均有所提升.其中质量比为1:1的BiFeO3@TiO2复合粉体(TiO2壳层厚度为50–100 nm)展现出最强的光催化氧化活性,且在可见光下有更高的光催化效率.经表征分析,该复合粉体光催化性能高的原因可能归结于BiFeO3与TiO2两者之间形成了p-n异质结界面,有效地提高了电荷载流子的传输分离效率,同时BiFeO3较窄的禁带宽度拓展了纳米TiO2的光谱吸收范围,增强其光吸收能力.光电化学Mott-Schottky测试结果进一步证实:BiFeO3粉体在与TiO2复合之后,其电荷载流子传输与供体密度均有显著提升.自由基猝灭实验表明,在甲基紫光催化降解中起主要作用的为羟基自由基与光生电子,并结合能带理论与自建电场理论对降解机理进行了阐述.进一步研究表明,甲基紫降解效果最优条件为:复合粉体的投加量为1 g/L,甲基紫初始浓度为10 mg/L,初始pH为5.另外,质量比1:1的BiFeO3@TiO2对甲基橙和刚果红染料废水也具有较好的降解效果,表现出良好的工业应用前景.
Magnetically separable bismuth ferrite (BiFeO3) nanoparticles were fabricated by a citrate self-combustion method and coated with titanium dioxide (TiO2) by hydrolysis of titanium butoxide (Ti(OBu)4) to form BiFeO3@TiO2 core–shell nanocomposites with different mass ratios of TiO2 to BiFeO3. The photocatalytic performance of the catalysts was comprehensively investigated via pho-tocatalytic oxidation of methyl violet (MV) under both ultraviolet and visible-light irradiation. The BiFeO3@TiO2 samples exhibited better photocatalytic performance than either BiFeO3 or TiO2 alone, and a BiFeO3@TiO2 sample with a mass ratio of 1:1 and TiO2 shell thickness of 50–100 nm showed the highest photo-oxidation activity of the catalysts. The enhanced photocatalytic activity was as-cribed to the formation of a p-n junction of BiFeO3 and TiO2 with high charge separation efficiency as well as strong light absorption ability. Photoelectrochemical Mott–Schottky (MS) measurements revealed that both the charge carrier transportation and donor density of BiFeO3 were markedly enhanced after introduction of TiO2. The mechanism of MV degradation is mainly attributed to hy-droxyl radicals and photogenerated electrons based on energy band theory and the formation of an internal electrostatic field. In addition, the unique core–shell structure of BiFeO3@TiO2 also pro-motes charge transfer at the BiFeO3/TiO2 interface by increasing the contact area between BiFeO3 and TiO2. Finally, the photocatalytic activity of BiFeO3@TiO2 was further confirmed by degradation of other industrial dyes under visible-light irradiation.
参考文献
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%