Preparation And Photocatalytic Activity Of Bi₂Fe 4O₉ And Bi₄Ti₃O₁2 Nanoparticles

In the 21st century, photocatalytic technology has attracted more and more attentions as a kind of"ideal green"technology for solving energy and environmental problems. This thesis mainly focuses on two kinds of nano-photocatalyst: Bi₂Fe₄O₉ and Bi₄Ti₃O₁₂. The properties of photocatalysts depend highly on their morphologies and sizes, especially at the nanoscale, the photocatalyst is expected to display enhanced photocatalytic efficiency.The main points are summarized as follows:(1) In this thesis, a polyacrylamide gel route is introduced to prepare the Bi₂Fe₄O₉ nanoparticles, and the grain size of nanoparticles is controlled by using different chelating agents. It is demonstrated that the phase-pure Bi₂Fe₄O₉ nanoparticles can be prepared at a calcining temperature of 750 oC using citric acid and ethylenediamine-tetraacetic acid (EDTA) as the chelating agents. The SEM observations show that the particle size of EDTA-resulted product is smaller than that of citric acid-resulted product. It is found that the Bi₂Fe₄O₉ nanoparticles reveal weak ferromagnetism at room temperature, and the ferromagnetism increases with the decrease of particle size. The UV-vis diffuse reflectance spectrum displays that the bandgap of Bi₂Fe₄O₉ nanoparticles is around 2.08eV. The photocatalytic properties of prepared Bi₂Fe₄O₉ nanoparticles are investigatied by the degratadation of methyl red. The results of photocatalytic experiment reveal that the photocatalyst activites increase with decreasing the particle size. The influence of catalyst loading on the degradation of methyl orange is also investigated. In the present experiments, the optimum loading of Bi₂Fe₄O₉ nanoparticles is obtained to be ¹.5 g L–1.(2) The Bi₄Ti₃O₁₂ nanoparticles are successfully prepared by the polyacrylamide gel route using different chelating agents. The XRD analysise indicate that the high-phase-purity Bi₄Ti₃O₁₂ nanoparticles can be obtained at the relatively low sintering tempreture (500oC) using citric acid and acetic acid as chelating agents. The SEM observations show that the use of citric acid as the chelating agent allows the production of Bi₄Ti₃O₁₂ nanoparticles with a relatively smaller particle size. The UV-vis diffuse reflectance spectra exhibit that the bandgaps of citric acid- and acetic acid-resulted products are 3.18 and 3.14 eV, respectively. The photocatalytic activity of Bi₄Ti₃O₁₂ nanoparticles is evaluated by the degradation of Methyl orange, Acid magenta, Rhodamine B and Congo red under ultraviolet light irradiation. The results show that Bi₄Ti₃O₁₂ nanoparticles have pronounced photocatalytic performance for the above dyes degradation, and the highest degradation efficiency is observed for CR.