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

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 ZnFe2O4 crystallites are highly dispersed on the surface of photocatalysts; a few of Fe3+ ions are embedded in the lattice of TiO2 through the couple of TiO2 and ZnFe2O4. Simultaneously, the excess Zn2+ 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 ZnFe2O4.