Preparation And Photocatalytic Degradation Performance Study Of Barium Titanate Coupled α/γ-bismuth Oxide Heterojunction

Barium titanate（BaTiO₃）and bismuth oxide（Bi₂O₃）are two important photocatalytic semiconductor materials.Due to the recombination of photogenerated electron and holes in intrinsic semiconductors,the photo-conversion efficiency is limited.In this paper,the photocatalysis degradation efficiencies of rhodamine B,tetracycline and norfloxacin were greatly improved by constructing single Z-type BaTiO₃/γ-Bi₂O₃ heterojunction and double Z-type BaTiO₃/α-Bi₂O₃/γ-Bi₂O₃ heterojunction.BaTiO₃/γ-Bi₂O₃ heterojunction samples with different raw material ratios,different calcination temperatures and duration were prepared by hydrothermal method,co-precipitation method and solid-state method.X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray photoelectron spectroscopy,and Raman spectroscopy were utilized to characterize the crystal structure,microscopic morphology,element species,valence,and vibrational information of functional groups.These characterizations further verified the formation of the heterojunction.Under 90 minutes of ultraviolet light irradiation,the removal efficiency of tetracycline was higher than 93%for all heterojunctions.The variation of catalyst quality,water solvents and pH value had a little effect on the final degradation efficiency of tetracycline.Under the same test conditions,the degradation efficiency of Rhodamine B of the optimal sample was 100%.BaTiO₃/γ-Bi₂O₃ has a good photocatalytic retention property and structural stability via cyclic tests.Based on the analysis of work function and differential charge density,the photocatalytic enhancement mechanism of BaTiO_3/γ-Bi₂O₃ is originated from the Z-type energy band to promote the recombination ofγ-Bi₂O₃ conduction band electrons and BaTiO₃valence band holes and to elevate the separation efficiency of photogenerated charges.Finally,the degradation pathways of these two pollutants were obtained by HPLC-MS analysis.Based on hydrothermal method,α-Bi₂O₃ coupled BaTiO₃ heterojunction was insitu grown.During the preparation process of the sample,partialα-Bi₂O₃ was transformed intoγ-Bi₂O₃ to form a BaTiO₃/α-Bi₂O₃/γ-Bi₂O₃ triphase heterojunction.The characterization of crystal structure,crystal plane distance,and vibrational information of functional groups confirm the formation of the ternary heterojunction.Under 90 minutes of ultraviolet light irradiation,the degradation efficiency of norfloxacin reached 92.97%.The catalyst quality had a weak effect on the final efficiency while light source,initial concentration and pH value had different effects on the final degradation efficiency of norfloxacin.BaTiO₃/α-Bi₂O₃/γ-Bi₂O₃ has a good retention properties and structural stability using cyclic tests.The increase of specific surface area and the formation of double Z-type energy band configuration byγ-Bi₂O₃,α-Bi₂O₃ and BaTiO₃ are the key factors for photocatalytic activity enhancement through the analysis of BET specific surface area,sacrificial agent,diffuse reflection,Mott-Schottky,photocurrent and impedance.Finally,the degradation pathway of norfloxacin was given by charge-to-mass ratio analysis.