Preparation Of Novel Bismuth-based Visible-light Photocatalysts And Study On Their Environmental Catalytic Activity

Photocatalytic technology can take advantage of solar energy directly.Great progress has been made in water pollution control in recent decades.There is also a perfect application prospects in sterilization,photolysis of hydrogen,dye-sensitized solar cells and other directions.The main advantages of photocatalysis include:the efficiently degrading of highly difficult and highly toxic pollutants in water,the pollutants were degraded into CO₂,H₂O,and need no additional electron acceptors;photocatalysts are inexpensive,non-toxic,stable and reusable,etc.advantage.In recent years,visible-light-active Bi₂O₃ has aroused more and more concern due to its facile preparation and easily adjustable band gap.However,the photocatalytic activity of pure Bi₂O₃ was still low.In order to meet the requirement of future environmental application and,it is important to develop novel and more efficient bismuth-based photocatalysts.In this paper,the Bi@BiOI-Bi₂O₃ photocatalyst was prepared by using UV reduction method.Morphology,surface properties,crystallization characteristics and electrochemical properties were investigated.It was found that Bi@BiOI-Bi₂O₃ exhibited many advantages compared with BiOI-Bi₂O₃:?1?the photocurrent under visible light was significantly improved,the bandgap was reduced,the electron transport impedance decreased,the photogenerated electron transfer rate was accelerated;?2?The degradation rate of phenol was significantly faster.When the reduction reaction time was 3 h in the preparation conditions,the photocatalytic activity of Bi@BiOI-Bi₂O₃ was the highest.After repeated use,the catalyst still maintained a good activity,indicating that the catalyst has a good stability.The mechanism study shows that hole?h+?plays a major role in the photocatalytic degradation of phenol by Bi@BiOI-Bi₂O₃,and hydroxyl radical?·OH?and superoxide radical?O2·-?play a supporting role.The Bi@BiOI-Bi₂O₃ thin films were prepared by UV-reduction and impregnation method.And was also characterized with similar means.The results show that:?1?BiOI-Bi₂O₃ is well compounded together;?2?Bi particles have been successfully formed after UV reduction,which has a significant change in the color and ultraviolet spectrum of the catalyst,and 35 min is the best reduction reaction time;?3?Bi@BiOI-Bi₂O₃ visible light absorption increased significantly.The photocatalytic activity of Cr?VI?-phenol wastewater was investigated.The degradation rate was about 3.2 times?phenol?and 16.8 times?Cr?VI??of that of Bi₂O₃ thin film.Furthermore,Bi@BiOI-Bi₂O₃/C₃N₄ thin films were prepared by in situ UV reduction and ultrasonic stripping.The results shown that:?1?The addition of C3N4 stripping liquid significantly enhanced the visible light photocurrent?3.3 times than Bi@BiOI-Bi₂O₃ at 0.35 V vs.Ag/AgCl?;?2?the best ultrasonic stripping time of 6 h;?3?Bi@BIOI-Bi₂O₃/C₃N₄ films have a better effect on the simultaneous reduction of Cr?VI?and phenol,which is about 1.3 times?phenol?and 3.9 times?Cr????than that of Bi@BiOI-Bi₂O₃.