复合半导体光催化材料ZnFe_2O_4-TiO_2／SiO_2结构与光响应性能研究

Structure and Photo Absorption Property of Coupled Semiconductor ZnFe_2O_4-TiO_2/SiO_2

采用溶胶-凝胶法制备了负载型复合半导体光催化材料ZnFe2O4-TiO2／SiO2,并通过DTA—TG、XRD、XPS、Raman、TPR,及UV-Vis DRS等实验技术对复合材料的晶体结构、表面组成及光响应性能进行了表征和评价．结果表明: ZnFe2O4晶相以高分散状态存在于光催化材料的表面; ZnFe2O4与TiO2复合可使部分Fe3+进入体相TiO2的晶格中,促进其由锐钛矿向金红石的相转变,同时表面剩余的少量Zn2+聚集形成ZnO物相;TiO2的相变由体相开始,随着ZnFe2O4含量的增加逐渐向表面扩展;SiO2的加入使活性组分更加分散, TiO2平均粒径<10nm;ZnFe2O4的加入明显拓宽了TiO2的吸光域,并增强了对可见光的吸收．

ZnFe2O4-TiO2/SiO2 photocatalysts were prepared by a sol-gel method. Their crystal structure, surface compositions and photo absorption properties were investigated by techniques of differential thermal-thermal gravimetric analysis （DTA-TG）, X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, Raman spectroscopy, temperature programmed reduction （TPR） and ultraviolet-visible diffuse reflectance spectroscopy （UV-Vis DRS）. The results show that ZnFe204 crystallites are highly dispersed on the surface of photocatalysts; a few of Fe^3＋ ions are embedded in the lattice of TiO2 through the couple of TiO2 and ZnFe2O4. Simultaneously, the excess Zn^2＋ ions on the surface are gathered to form ZnO. The phase transition of TiO2 starts from bulk and extends to surface with the increase in content of ZnFe2O4. The dispersity of active species, such as TiO2 and ZnFe2O4, is enhanced for the addition of SiO2 and the crystal sizes of TiO2 are smaller than 10nm. The UV absorption limit of photocatalyst tends to bathochromic shift and the percent absorption of visible light is obviously increased by the coupling effect of TiO2 and ZnFe204.