Preparation Of Modified BiOX(X=Cl、Br、I)from Microwave-assisted Method And Photocatalytic Performances

With the improvement of living standard,increasing attention has been paid to environmental pollution issue.Photocatalysis is a newly developed technology which utilizes semiconductor materials to degrade organic dyes in water and poisonous gases in air.The photocatalytic process is energetically driven by UV or visible light and the final products are CO2 and H2O,which endows the technology with green and environment-friendly characteristics,thus a great application potential in the treatment of pollution is expected.Bismuth-based photocatalyst is a class of new high-performance photocatalytic materials.we systematically investigated the preparation of microwave-assisted method and photocatalytic activity of this kind of materials,typically including BiOCl.BiOBr and BiOI,which is mainly divided into three aspects:(1)Novel BiF3/BiOBr heterojunction photocatalysts were prepared from a fast and stable microwave-assisted method,and characterized by X-ray diffractometry,X-ray photoelectron spectroscopy,scanning electron microscopy,ultraviolet-visible spectroscopy and fluorescence spectroscopy.With Rhodamine B(RhB)as the target pollutant,the photocatalytic activity of BiF3/BiOBr heterojunctions was significantly higher than pure BiOBr or BIF3,and was maximized at the Br:F molar ratio of 1:1,as the 20 mg/L RhB solution was completely degraded within 40 min.This was mainly because the unique BiF3/BiOBr heterojunction formed during photocatalytic degradation accelerated the separation between photoelectrons and holes,effectively enhanced the quantum efficiency,and thereby strengthened the photocatalytic activity.(2)The BiOI/BiOCI composites with high photocatalytic activity were prepared via a rapid and reliable microwave-assisted method.Microstructures,morphologies,and bandgaps of the as-prepared samples were determined through XRD,XPS,SEM,UV-vis and PL.The results showed that the obtained BiOI/BiOCl(S3)composite has the highest photoactivity for the degradation of Rhodamine-B.All the 20 mg/L RhB aqueous solution can be degraded in 60 min.These obvious enhancements were attributed to expanded visible light absorption and high separation performance of photoinduced charge and holes.Moreover,after three times recycling for the photodegradation of RhB solution,there was not significant decrease in the photocatalytic activity,implying that the as-prepared photocatalysts are highly stable.Finally,a possible photocatalytic mechanism has been proposed.(3)The pure BiOBr and the Ba2+ doped BiOBr photocatalysts with good photocatalytic activity were prepared via microwave-assisted method,and characterized by XRD,SEM,UV-vis and PL.The photocatalytic activity was tested by the photocatalytic degradation of Rhodamine B(RhB)solution.The results showed that the Ba2+-BiOBr has much better photocatalytic activity than pure BiOBr.And Ba2+-BiOBr catalyst could completely degrade 20 mg/L RhB aqueous solution after 55 min.The better photodegradation activity could be mainly attributed to the higher separation effieiency of photo-induced electrons and holes.After three times recycling for the photodegradation of RhB solution,there was not significant decrease in the photocatalytic activity,implying that the as-prepared photocatalysts are highly stable.The trapping experiments demonstrated that the photogenerated hole(h+)and superoxide radicals(·O2-)are the mainly oxidative species in the degradation reactions.