Preparation And Modification Of Micro-Nano Structure Dendritic Zinc Ferrite And The Photocatalytic Activity

There is much interest about spinel zinc ferrite(Zn Fe2O4) semiconductor in the field of photocatalysis due to the narrow bandgap, response to visible light, the stability under chemical and photo-chemical condition. Hierarchical dendritic micro-nano structure Zn Fe2O4 had been prepared by electrochemical reduction and thermal oxidation method in this work, and modification was applied to the Zn Fe2O4. X-ray diffractometry, Raman spectra, field-emission scanning electron microscopy and transmission electron microscopy were used to characterize the crystal structure, size and morphology. UV-Vis diffuse reflectance spectra were acquired by a spectrophotometer to analysize the optical absorption properties. Photocatalytic activities for water splitting were investigated under 300 W Xe light irradiationHierarchical dendritic micro-nano structure Zn Fe2O4 have been prepared when the propotion of Zn2+ is 0.35(Zn2+ and Fe2+are total 1mol/L) in the electrolyte through the process of electrochemical reduction. The main crystal face of Zn Fe2O4 is(311), and its BET specific surface area is 22.0197m2·g-1. The absorption edge of Zn Fe2O4 is in the range of visible light and a relatively high photocatalytic activity with 1.41μmol·h-1·0.02g-1 was achieved by Zn Fe2O4. Increasing or reducing the propotion of Zn2+, the sample is composed of Zn O and Zn Fe2O4 or α-Fe2O3 and Zn Fe2O4. And the absorption edge are blue shift and red shift, respectively. The sample with α-Fe2O3, the conduction band is not according with the H2 energy, and the impurity energy levels of the sample with Zn O can leads to the recombination centers of the excited electrons and holes to worsen photocatalytic activity.Coupled semiconductor of Zn Fe2O4-Ti O2 was prepared by sol-gel method. When the TBOT is an appropriate amount of 8.6m L, the product is hierarchical dendritic micro-nano structure, and Zn Fe2O4-Ti O2 are core-shell structure. However, the amount of TBOT is less, the products are still hierarchical dendritic micro-nano structure, but there are no Ti element and Ti O2 are detected, the properities of light absorbance of the samples are the same with Zn Fe2O4. When the amount of TBOT is more, the products are bulk in black. Ti O2 in the samples is antase and the absorption edge does not exist. Enhancing the sintering temperature, coupled Ti O2 transfers from anatase into ruitile, while the phase of Zn Fe2O4 does’ nt change. And in this condition, the absorption edge is blue shift slightly. The sample prepared under 450℃ has the best photocatalytic activity, which is the mixture of anatase and rutile about Ti O2.The Zn Fe2O4 was modification using sulfourea as the source of S with solvothermal. Fe3S4 emerged in the product, and the amount of Fe3S4 increasing with the temperature rises. The product is debris, which is composed of nano particles and micro rod. When the temperature of solvothermal increased to 160℃, the absorption edge disappeared, the photocatalytic activity is worse than pure Zn Fe2O4.