Synthesis And Photocatalytic Activity Of Iron Oxide-based Composite Photocatalysts

A serious of a-Fe2O3based heterostructure composite was prepared successfully to reduce the recombination rate of photogenerated electron-hole pairs and immobilized a-Fe2O3on Ti sheet and γ-Fe2O3respectively for the problem of recycling. The characterization of a-Fe2O3based heterostructures, such as the crystal, surface morphology and optical property, were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), FT-IR Spectrometer (FTIR), UV-Vis Spectrometer, PL(photoluminescence) Spectrometer and photoelectrochemistry analysis. The main work contents are divided into four parts, and the main research and results are as follows:Firstly, a heterojunction nanofiber material NiTiO3/a-Fe2O3was synthesized by a two-step hydrothermal and sol-gel method involving calcining process. The characteristic nature of the materials confirmed the high crystalline behavior and fiber-like heterostructures of the NiTiO3/a-Fe2O3composites. The NiTiO3/a-Fe2O3heterojunction nanofibers were observed to exhibit an enhanced performance in the photocatalytic degradation of organic dye. After the reaction time of180min, the decomposition of RhB was observed to be90.4%employing NiTiO3/a-Fe2O3composites, while it was only up to55.1%and59.0%for a-Fe2O3nanofibers and NiTiO3nanoparticles, respectively. The superior absorptive behavior of NiTiO3/a-Fe2O3heterojunction nanofibers to pure a-Fe2O3nanofibers in the longer wavelength region was confirmed by UV-vis Diffuse Reflectance Spectral (DRS) studies. The photoluminescence (PL) spectral studies indicated that the recombination of photogenerated electron-hole pairs has been decreased in the case of NiTiO3/a-Fe2O3.Secondly, a-FeOOH/a-Fe2O3composites were synthesized by a two-step solvothermal and hydrothermal method with calcining process. The characteristic of the materials confirmed the a-FeOOH/a-Fe2O3heterostructures of the composites. The a-FeOOH/a-Fe2O3nanoshperes showed an enhanced performance compared with a-Fe2O3nanoparticles and a-FeOOH nanoparticles in the photocatalytic degradation of RhB under the visible light irradiation. Furthermore, the degradation of phenol was efficient with a-FeOOH/a-Fe2O3composites that the degradation efficiency up to60%within10h under the visible light irradiation. The a-FeOOH/a-Fe2O3heterostructures showed superior absorptive behavior to pure a-Fe2O3nanoshperes in the longer wavelength region and the lower PL emission intensity center at475nm. The enhanced photocatalytic performance was mainly due to the decreased recombination of photogenerated electron-hole pairs in the case of a-FeOOH/α-Fe2O3heterostructures.Thirdly, AgCl/Fe2O3composites were synthesized by a simple chemical precipitation method and calcining process. The composition of the material and magnetic and optical properties of the composites were studied, which confirms the high crystalline and magnetic behavior of the composites. DRS studies showed that the AgCl/Fe2O3composites were of much higher absorption in longer wavelength region compared to bare iron oxide. The AgCll/Fe2O3composites showed better performance (100%) in the photodegradation of RhB under the fluorescent lamp irradiation, which is remarkably superior to the Fe2O3(18.2%) and N-TiO2(41.1%). The degradation of microcystin-LR (MC-LR, removal efficiency reached100%within75min) and phenol (removal efficiency reached76%within12h) was also found to be good owing to its effective electron-hole separation at AgCl/Fe2O3interface. The separation of AgCl/iron oxide composites from the treated water was achieved by an external magnetic field as γ-Fe2O3exhibits enough magnetic power to facilitate the separation.Forthly, Ag/AgBr/a-Fe2O3films were synthesized by hydrothermal and sequential chemical bath deposition methods with calcining process. Compared with pure a-Fe2O3film, the photoelectrocatalytic (PEC) degradation efficiency of Ag/AgBr/a-Fe2O3film was enhanced and almost twice of former. The5C sample of Ag/AgBr/a-Fe2O3films showed the highest degradation efficiency in the PEC degradation of RhB under the visible light irradiation and the PEC degradation efficiency up to83.6%within180min. while it was only up to55.1%for pure a-Fe2O3film. The effect of type of anions is studied, and the resules showed the degradation of RhB was highly promoted in NaCl electrolyte owing to the formation of chloride radical. The Ag/AgBr/a-Fe2O3films had superior current response, resistance performance and absorptive behavior to pure a-Fe2O3film that were beneficial to PEC reaction. The recombination of photogenerated electron-hole pairs has been decreased in the Ag/AgBr/α-Fe2O3heterostructures may be the main reason for the enhanced PEC activity.