Synthesis,Characterization And Visible-light Photocatalytic Activity Of High-efficient Bismuth-containing Composite Photocatalyst

Up to now,there are lots of research available in purification of wastewater,especially for toxic organic contaminants.Despite significant efforts to date,the semiconductor photocatalysis technology is still insufficient to satisfy the requirements for industrially oriented applications,due to two intrinsic shortcomings of the conventional photocatalytic systems.One is the wide band-gap,making it only possess moderate photocatalytic performance.The other shortcoming is the catalyst separation and recovery.Therefore,the research for constructing high efficiency and recyclable visible-light-driven photocatalysts has always been the focus of these endeavors under the increasing environmental pressure.The bismuth oxyiodide(BiOI)is proved to be the most promising photocatalyst candidate for wastewater treatment with the narrowest band gap(ca.1.6-1.9 eV)and strongest visible light absorption.However,the suspended particulate catalysts are difficult to be recovered,which limits the functional life-time of BiOI for photocatalysis in practical application.Given this situation,our research is devoted to the design and construction of magnetically loaded photocatalytic materials based on BiOI materials.The main researches are listed as follows:Firstly,bismuth iodide materials with different morphologies were prepared by different solvent systems,including 2D-nanosheets and 3D-microspheres.Combined with XRD,SEM,BET and other characterization methods,the influence of specific experimental conditions on the morphology of bismuth iodide was analyzed,and the formation mechanism of bismuth iodide with different morphologies was discussed.In addition,the effect of morphology on the photocatalytic activity of visible light degradation of methyl orange by bismuth iodide was also studied.This above experiment research had prepared the theoretical and experimental basis for the design and construction of magnetically loaded photocatalytic materials.Based on the above research,we designed and constructed a magnetic core-shell composite photocatalyst with ferriferrous oxide Fe3O4 as magnetic core and BiOI as the shell.The above photocatalyst was synthesized by a facile chemical precipitation with atmospheric pressure and low temperature.The composition,structure,morphology and basic properties of the composite catalyst,such as optical absorption and electrochemical properties,were characterized by a series of characterization methods.Besides,the formation mechanism of the core-shell structure was discussed in depth.The energy gap of PONs is 1.78eV,BET surface area is46.60m2g-1.The addition of Fe3O4 is beneficial to the charge transfer of the catalystinterface.When the ratio of Fe/Bi is 3,therecombination rate of photogenerated chargeis the lowest.Finally,we carried out a series of functional experiments on the above synthesized magnetic core-shell photocatalysts,analyzed their photocatalytic performance,test the cyclic stability performance,and explored their photocatalytic mechanism respectively.The degradation rate of phenol(20 mg/L)by PONs under visible light(5 h)reaches 93.7%,andthemainly active species in photocatalytic process are ·O2,-·OHand h+.The magnetic saturation value of the PONs reaches 14.1 emu/g.After five cycles,the photocatalytic degradation rate of methyl orange by PONscan still maintain over 85%.The work paves a novel way for the further design ofheteroj unction photocatalysts with fine recyclability and enhanced photocatalytic activity.