Synthesis of hierarchical dendritic micro-nano structure ZnFe2O4 and photocatalytic activities for water splitting

Hierarchical dendritic micro-nano structure ZnFe2O4 have been prepared by electrochemical reduction and thermal oxidation method in this work. X-ray diffractometry, Raman spectra and field-emission scanning electron microscopy were used to characterize the crystal structure, size and morphology. The results show that the sample (S-2) is composed of pure ZnFe2O4 when the molar ratio of Zn2+/Fe2+ in the electrolyte is 0.35. Decreasing the molar ratio of Zn2+/Fe2+, the sample (S-1) is composed of ZnFe2O4 and alpha-Fe2O3, whereas increasing the molar ratio of Zn2+/Fe2+, the sample (S-3) is composed of ZnFe2O4 and ZnO. The lattice parameters of ZnFe2O4 are influenced by themolar ratio of Zn2+/Fe2+: Zn at excess decreases the cell volume where as Fe at excess increases the cell volume of ZnFe2O4. All the samples have the dendritic structure, of which S-2 has micron-sized lush branches with nano-sized leaves. UV-Vis diffuse reflectance spectra were acquired by a spectrophotometer. The absorption edges gradually blue shift with the increase of the molar ratio of Zn2+/Fe2+. Photocatalytic activities for water splitting were investigated under Xe light irradiation in an aqueous olution containing 0.1 mol.L-1 Na2S/0.02 mol.L-1 Na2SO3 in a glass reactor. The relatively highest photocatalytic activity with 1.41 mu mol.h(-1).0.02g(-1) was achieved by pure ZnFe2O4 sample (S-2). The photocatalytic activity of the mixture phase of ZnFe2O4 and alpha-Fe2O3 (S-1) is better than ZnFe2O4 and ZnO (S-3). (C) 2016 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.