In-situ Construction And Photocatalytic Performance Enhancement Mechanism Of High-performance Conjugated Carbon Materials/BiOX (X=Cl, Br, I)

Photocatalytic technology has become one of the effective means to control environmental pollution because of the advantages of green environmental protection,low energy consumption and easy operation.Among various photocatalysts,BiOX(X=Cl,Br,I)has attracted much attention due to its unique structure and good photocatalytic performance.However,the high photogenerated electrons and holes recombination rate restricted its further application.In this paper,the strategy of surface modification was carried out by using several conjugated carbon materials with transfer electron ability to obtain the BiOX(X=Cl,Br,I)based photocatalytic material with better photocatalytic performance.Several new conjugated carbon materials/BiOX(X=Cl,Br,I)composite photocatalysts were designed and prepared.Their crystal structure,micro-morphology and optics were characterized and analyzed by various testing methods.The separation and transfer of photogenerated charges were studied by surface photovoltaic(SPS)technology and electron spin resonance(ESR)technology.Based on the experimental and characterization results,the separation and transfer of photogenerated charge and the enhancement mechanism of photocatalytic performance were proposed.The specific research contents of this paper are as follows:(1)The new C60/BiOX(X=Cl,Br)composites were successfully prepared by hydrothermal method,microwave method,reflux method and physical mixing method,respectively.The photocatalytic activity of the prepared photocatalyst was investigated using RhB as a simulated pollutant.The results showed that the C60/BiOX(X=Cl,Br)composites prepared by hydrothermal method had the best photocatalytic activity.Through experimental and theoretical analysis,the photocatalytic mechanism was studied and proposed.The results show that pure BiOX(X=Cl,Br)are lamellar structure,while C60/BiOX(X=Cl,Br)are microspheric structure,C60has the role of hard template to induce morphological changes;there are electron transfer and possible chemical interaction between C60and BiOX(X=Cl,Br);the capture experiments reveal that·O2-and h+play a major role in the photodegradation of RhB and phenol by C60/BiOX(X=Cl,Br).The photocatalytic results show C60/BiOX(X=Cl,Br)have excellent photocatalytic activity and cycle stability towards the RhB and phenol.The main reason for the improved photocatalyst performance is the remarkable enhanced separation efficiency of photogenerated electron and hole,due to the ability to transfer electrons from BiOX(X=C1,Br)of C60.(2)C70/BiOX(X=Cl,Br)photocatalytic materials with three-dimensional structure were fabricated in situ by hydrothermal method.C70 also changed the morphology of BiOX(X=Cl,Br),enhanced the absorption intensity and range of BiOX(X=Cl,Br),which was conducive to the improvement of photocatalytic performance.The effective separation of photogenerated charges was the main reasons for the significant improvement of photocatalytic activity of C70/BiOX(X=Cl,Br).(3)3D MWCNTs/BiOCl photocatalysts were successfully prepared by solvent method.The photocatalytic activities of 3D MWCNTs/BiOCl were better than that of BiOCl.When the mass ratio of 3D MWCNT/BiOCl was 3%,the photocatalytic performance was the best.The existence of MWCNT improved the separation efficiency of photogenerated electrons and holes and prolongs the lifetime of photogenerated carriers.The morphology of 3D 3%MWCNT/BiOCl(3MWCNT)was optimized.The formation of microsphere structure and the role of ethylene glycol in the formation of microspheres were discussed.The results show that ethylene glycol acts as both solvent and template in the reaction process.When the temperature of solvothermal reaction is 180? and the reaction time is 12 h,3D 3MWCNT has regular microsphere morphology and the highest photocatalytic activity.(4)BiOCl1-xIx and 1%C60/BiOCl0.8I0.2 photocatalysts were prepared using glacial acetic acid as solvent in situ by hydrothermal method.BiOCl1-xIx and 1%C60/BiOCl0.8I0.2 were characterized and analyzed by XRD,SEM,BET,SPS and UV-vis DRS.The results show that the prepared BiOCl1-xIxare solid solution rather than a simple mixture of BiOCl and BiOI.When n(Cl)/n(I+Cl)=0.8,the BiOCl0.8I0.2 solid solution exhibited the best photocatalytic activity for phenol degradation.The degradation of phenol reached 80%after 12 hours of illumination with 500 W xenon lamp.The photocatalytic activity and stability of BiOCl0.8I0.2 were further enhanced by modification with C60.The degradation rate constants of 1%C60/BiOCl0.8I0.2 photocatalyst were 2.1 times higher than BiOCl0.8I0.2(0.1243 h-1).