Preparation And Properties Of ?-Bi₂O₃-based Composites Photocatalysts

Bismuth oxide?Bi₂O₃?is the simplest and most important semiconductor material of bismuth.Bi₂O₃ is very suitable used as photocatalyst,because its absorption of visible light,the high oxidation ability of its valence band hole and completely non-toxic.Bi₂O₃ possesses 4 main polymorphs,monoclinic a-Bi₂O₃,tetragonal ?-Bi₂O₃,body centered cubic ?-Bi₂O₃,cubic ?-Bi₂O₃,and ?-Bi₂O₃ exhibit narrowest bandgap and highest photocatalytic efficiency among them.The photocatalytic efficiency of ?-Bi₂O₃ should be modified better due to its quick recombination of electron-hole and poor adsorptive performance.Combining Bi₂O₃ with the other semiconductor photocatalysts in one system would suppress the recombination of photoinduced electron-hole pairs,thus enhance the photocatalystic property.In this study,bismuth oxybromide?BiOBr?,monoclinic phase bismuth oxide??-Bi₂O₃?,cerium oxide?CeO₂?were selected to modify ?-Bi₂O₃ respectively,and prepared ?-Bi₂O₃ based composite photocatalysts.Dyes and antibiotic wastewater pollutants were selected to test the photocatalytic activities of the composite photocatalysts.The specific research contents are as following:1.In this work,core-shell ?-Bi₂O₃/BiOBr hollow heterostructures with flower-like microspheres morphology were successfully synthesized by a simple chemical etching method using situ reaction between HBr with ?-Bi₂O₃ hollow microspheres.The structure,chemical composition of P-Bi₂O₃/BiOBr was studied by XRD,Raman spectroscopy and XPS.The morphologies of prepared samples were characterized by FESEM,TEM and the optical absorption was detected by UV-vis DRS.The suppression of the electron-hole pair recombination was studied by PL analysis.Lanasol Red 5B and Ciprofloxacin were selected to test the photocatalytic activities of the ?-Bi₂O₃/BiOBr heterostructures.At the same time,we studied the appropriate concentration of wastewater,the influence of catalyst dose and the reuse capacity of catalyst Compared with the degradation efficiency of LR5B and CIP by pure Bi₂O₃ and different mole percentage of the photocatalytic materials,the results show that core-shell ?-Bi₂O₃/BiOBr hollow heterostructure photocatalysts possess higher photocatalytic efficiency and ?-Bi₂O₃/BiOBr?50%?composite showed the best photocatalytic effect.The degradation rate of Lanasol Red 5B was 90%in 40 min,and the degradation rate of ciprofloxacin was 90%in 50 min.2.A simple solvent thermal method was used to synthesize hollow sphere ?/?-Bi₂O₃ composite photocatalyst.The structure,morphology and optical properties of the as-prepared samples were analyzed by XRD,SEM,TEM EDS,FTIR,DRS and PL,respectively.And the photocatalytic degradation performance of the composite photocatalyst was tested by using Lanasol Red 5B and metronidazole as target pollutants.Combining two kinds crystal type of bismuth oxide would significantly improve the photocatalystic property.The ?/?-Bi₂O₃?400??composite photocatalyst showed the best photocatalytic in simulated sunlight,and the degradation rate of Lanasol Red 5B and metronidazole were respectively 2.40 and 2.49 times that of pure ?-Bi₂O₃.In this experiment,the mechanism of improving the photocatalytic performance of the hybrid crystal was discussed.3.In this paper,a simple solvent thermal method was used to successfully synthesize different proportions of ?-Bi₂O₃/CeO₂ photocatalyst by changing the proportion of bismuth source and cerium source.The structure,morphology,chemical composition and state,optical properties of the as-prepared samples were analyzed,respectively.The photocatalytic degradation performance of the composite photocatalyst was tested by using Lanasol Red 5B and methylimidazole as target pollutants.The ?-Bi₂O₃/CeO₂?0.5:1?composite photocatalyst showed the best photocatalytic in simulated sunlight,the degradation rate of Lanasol Red 5B and methylimidazole were respectively 3.26 and 3.02 times that of pure ?-Bi₂O₃.