Study On The Photocatalytic Properties Of Ion Doped BiFeO₃ And KNbO₃

With the rapid development of industry and economy of our country, challenges in environment protection and energy preservation have emerged. Sustainable development has become the new goal of our development. Solar energy is a green, renewable energy. The utilization of solar energy is a hotspot of scientific study. In this dissertation, sol-gel method was applied for the synthesis of Zn, Mn co-doped perovskite BiFeO3 nano powders. The photocatalytic and magnetic properties of were investigated. Same method was also adopted in the synthesis of Ba, Ni modified perovskite KNbO3 nano powders. And the photocatalytic behaviors of these nano powders were studied.BiFeO3 is a typical room temperature multi-ferroelectric material. It has already been applied in electronic device and ferroelectric storage. Since BiFeO3 has a relatively low bandgap and is responsive to visible light, its applications as photo catalysts and solar energy absorbers are also reported. However, due to the high electron-hole recombination rate of pure BiFeO3, it shows a low photocatalytic efficiency. n this dissertation, with Zn, Mn ion doping, visible light absorption of BiFeO3 were enhanced. The visible light photocatalytic properties were greatly improved with H2O2 as sacrificial agent. XRD measurement shows that the synthesized BiFeO3 powders are well crystallized. SEM shows that the nano powder has particle size ranging from 30nm to 50nm It is also observed that with the doping of Mn. The saturation magnetizationof BiFeO3 increases. While Zn doping tends to decrease the saturation magnetization BiFeO3.Ordinary perovskite materials have the limit of large bandgap. In order to reduce the bandgap value, Ni, Ba modified KNbO3 was synthesized. With Ni, Ba ion doping, sub bandgaps were introduced into KNbO3. The overall visible light absorption of KNbO3 was enhanced. Sub bandgaps introduced in the system were about 1.1～1.35eV depending on the doping ration. XRD and Raman spectra shows that the Ba, Ni co-modified KNbO3 powders were well crystallized. Compared with solid reaction method, the sintering temperature was lowered about 400℃. UV-Vis spectra shows the Ni, Ba co-modified KNbO3 has an indirect bandgap about 2.4eV, which 1 eV lower than pure KNbO3. Photocatalytic measurements show that the Ni, Ba co-modified KNbO3 with the doping ratio of 20% exhibits the best photocatalytic properties. It can degrade 91.8% of MB in 210min.