| Hematite (Fe2O3) is the semiconductor with the band gap about2.1eV that allows for utilizing a significant visible portion of the solar spectrum. Furthermore, it is environmental friendliness, nontoxic, abundant, also capable of withstanding neutral and alkaline conditions. Fe2O3is considered as a promising semiconductor material that has many desirable properties for photocatalysts and used as a photoanode in a solar cell, a photoelectrochemical cell and so on.In this thesis, the films of Zn-doped Fe2O3/Fe3O4microrods and Zn-doped Fe2O3/Fe3O4nano wires were prepared on the surface of carbon steel foils using a method of direct thermal decomposition of oxalate conversion coatings. The photocatalytic activities of the films were tested by using photodegradation performance of rhodamine B (RhB) under visible light irradiation (>400nm) in aqueous, and the photoelectrochemical properties were characterized with photocurrent tests. The films were characterized with scanning electron microscope (SEM), X-ray diffractometer (XRD), transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The effect of the preparation conditions on the morphologies, compositions, structures, photocatalytic performances and photoelectrochemical properties of the films were discussed in detail. The main research works and results are as follows:1. The preparation of Zn-doped Fe2O3/Fe3O4microrods. The precursors were obtained by dipping the carbon steel foils in the oxalic acid aqueous solution containing5.0×10-4mol/L Zn2+for90min,. The films of Zn-doped Fe2O3/Fe3O4microrods were prepared by direct thermal oxidation the precursors at350℃for2h in air in the muffle furnace. The results revealed that the films constituted with microrod structures of Fe2O3. The photocatalytic properties of the Zn-doped Fe2O3Fe3O4composite oxide films were tested by photodegradation of10mL3mg/L RhB illuminated with visible light. The photodegradation ratio of RhB on the Zn-doped Fe2O3/Fe3O4composite film is74.9%under visible light irradiation for3h. The results showed that the Zn-doped Fe2O3/Fe3O4composite film exhibited favorable photocatalytic properties towards RhB.2. The preparation of the Fe2O3nanowire oxide films. The precursors were prepared by dipping the carbon steel foils in the oxalic acid ethanol solution containing5.0×10-4mol/L Zn2+for90min. The films of Zn-doped Fe2O3/Fe3O4nanowires were obtained by direct thermal oxidation the precursors at350℃for2h in air in the muffle furnace. The results showed that the nanowire was well-crystalline and could be indexed as hexagonal Fe2O3. TEM and XPS analysis results showed that the amount of Zn incorporated was2.2at%and Zn doping in Fe2O3nanowires mainly. The crystal structure of hexagonal Fe2O3was influenced because of Zn-treatment. The photocurrent of the Zn-doped Fe2O3/Fe3O4composite film was considerably enhanced compared to that of the undpoed Fe2O3/Fe3O4film.3. The influence of the concentration of the oxalic acid ethanol solution on the formation of the Zn-doped Fe2O3/Fe3O4composite oxide films. At the constant concentration of Zn2+5.0×10-4mol/L, the effects of the oxalic acid concentration on the morphologies of the oxide films were studied. The results revealed that the morphologies of the composite oxide films depended on the concentration of the oxalic acid. As increasing the concentration of the oxalic acid, the atomic percent of Zn firstly increased then reduced. The nanowire films could be prepared in the conditions of1.5M oxalic acid ethanol solution.Under the concentration of0.1mol/L oxalic acid in ethanol, the Zn-doped Fe2O3/Fe3O4composite oxide films haved the highest photocurrent. A photocurrent density of1.5μA/cm2at zero bias was obtained. |
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