Composites Of BiFeO₃ And TiO₂:Preparation And Their Photocatalytic Properties

Photocatalytic technology has broad application prospects in the field of environmental pollution control because of its advantages of mild reaction condition,clean and high efficiency,low cost and environmentally friendly.TiO₂ has became a hotspot in the field of photocatalysis due to its low non-toxic,excellent redox capacity and resistance to chemical attack,but its intrinsic two defects?low utilization of sunlight,high recombination rate of the photogenerated electron-hole pairs?limit its practical application.BiFeO₃ has small bandgaps and interesting ferroelectricity which helps to improve the efficiency of photocatalytic carrier separation so as to improve the catalytic activity of the materials.In this work,BiFeO₃/TiO₂ nanotube array composite electrode and BiFeO₃/TiO₂ flower-like composites were prepared.Then,the composite materials were utilized for degrading the typical pollutants of methylene blue and odichlorobenzene and evaluated their photocatalytic performance.The main work and research results are as follows:Firstly,the BiFeO₃/TiO₂ nanotube arrays electrode was prepared by combining inorganic phase of anodic oxidation and ultrasonic assisted continuous ion adsorption reaction methods.The electrodes were studied by morphology,chemical composition and crystal structure characterization.Also,we studied thier optical properties and performance.Results showed that the BiFeO₃ nanoparticles not only widened optical response of TiO₂ nanotube arrays but also promoted the photogenerated electronic-hole pairs separation.Under visible light irradiation,photocatalytic degradation efficiency over the BiFeO₃/TiO₂ nanotube array composite electrode was 3.2 times as high as that of TiO₂ nanotube arrays electrode and the cycle experiments showed the excellent stability.Secondly,the TiO₂ flowers and BiFeO₃ nanoparticles were prepared via the hydrothermal method and sol-gel method,respectively.Then,a wet chemical strategy was adopted to fabricate the BiFeO₃/TiO₂ flower-like composites.Results of scanning electron microscopy and transmission electron microscopy characterization showed BiFeO₃ nanoparticles were uniformly dispersed on the surface of TiO₂ nanoflowers and formed the heterogeneous structure;Ultraviolet-visible diffuse reflectance spectroscopy,photoluminescence spectroscopy,and surface photovoltage characterization analysis results indicated that the loaded BiFeO₃ nanoparticles widened optical response of TiO₂ flowers and improved significantly the photoinduced charge separation efficiency.Finally,o-dichlorobenzene was studied as the target pollutant to analyze photocatalytic performance of BiFeO₃/TiO₂ flower-like composites.After 8 h,the degradation efficiency over the BiFeO₃/TiO₂ flower-like composites was 68.72% and 1.7 times as high as pure TiO₂ flowers.The o-DCB generated intermediate products of photocatalytic degradation and reactive oxygen species were detected combining with in-situ infrared spectra and electron paramagnetic resonance spectroscopy.The main reactive oxygen radicals were the · OH and · O₂^-in the catalytic reaction.The path of o-DCB photocatalytic degradation also was speculated.Firstly,benzene ring was subjected to hydroxylation process.Secondly,the chlorines of benzene ring were replaced by the hydroxy to generate benzoquinone,generating inorganic acid.Finally,these intermediate products could be completely mineralized to small molecules,such as CO₂ and H₂O.