Study On Preparation And Photocatalytic Degradation Of Organic Pollutants Of Cu₂O And Bi₂WO₆

Cu₂O and Bi₂WO₆ are two visible light responsive photocatalysts with promising applications in wastewater treatment and VOCs degradation.In order to find photocatalysts with simple process,low price,excellent catalytic activity and commercial scale.In this paper,Cu₂O,Bi₂WO₆ and Bi OCl/Bi₂WO₆ composites were prepared for the degradation of methyl orange（MO）and VOCs,respectively,using two modification methods:morphology modulation and semiconductor compounding.The effects of different reaction conditions on the material phase structure,surface morphology and photocatalytic performance were investigated,and the possible photocatalytic mechanisms were preliminarily explored,mainly as follows:（1）In this chapter,a simple water bath reduction method was used to achieve controlled preparation of Cu₂O morphology and size.The experimental results exhibited that the concentration of glucose in the reaction system is the key factor affecting the morphology of Cu₂O,and the amount of glucose could be adjusted to obtain octahedral,truncated octahedral,sphere-like and spherical Cu₂O with different particle sizes.The degradation rate of MO after 120 min of visible light irradiation was 94.6%.In addition,reducing the grain size of Cu₂O significantly enhanced its photocatalytic activity,and the spherical Cu₂O with the smallest grain size showed a removal rate of 99.9%for high MO concentration within 30 min.The growth mechanism and catalytic mechanism were also preliminarily investigated.This work provides a new strategy for the synthesis of Cu₂O with excellent photocatalytic activity.（2）Bi₂WO₆ and Bi_3.84W_0.16O_6.24 materials with different morphologies were prepared by a simple hydrothermal method.The results showed that the products gradually change from the orthorhombic structure of Bi₂WO₆ to the cubic crystalline phase Bi_3.84W_0.16O_6.24 with increasing p H in the reaction system.In addition,the morphology gradually changes from 3D flower-like microspheres composed of two-dimensional nanoflakes to nanoparticles.The complete and dense flower-like Bi₂WO₆microspheres obtained under acidic conditions were found to have excellent photocatalytic performance,while the Bi_3.84W_0.16O_6.24 nanoparticles obtained under alkaline conditions hardly degraded gaseous toluene.77.8%removal of gaseous toluene was maintained after four cycles of S1 samples.（3）Due to the similar structure and synthesis conditions of Bi OCl and Bi₂WO₆,UV-driven Bi OCl and visible-light-driven Bi₂WO₆ were successfully combined by a one-pot hydrothermal method to obtain tightly bound,active site-rich Z-scheme Bi OCl/Bi₂WO₆ photocatalysts.The results presented that the best ratio of Bi OCl/Bi₂WO₆composite（BWOCl-2）was obtained by tailoring the amount of hydrochloric acid（HCl）,which exhibited nearly 100%degradation activity and good durability for gaseous toluene,with 49.33%degradation rate even after 24 h of continuous light exposure（for 8 cycles）.In addition,BWOCl-2 also showed excellent photocatalytic activity for mixed benzenes,with 100%degradation of all benzenes except benzene（ethylbenzene,toluene,and o-/m-/p xylene）after 7 h of continuous illumination.Based on ESR and gaseous radical capture experiments,we confirmed that cavities play a major role in the degradation of gaseous toluene,and revealed a possible toluene degradation pathway using in-situ DRIFTS:toluene→benzaldehyde→benzoic acid→aliphatic compounds→carbon chain→CO₂+H₂O.The catalyst has excellent visible light response for VOCs degradation,and this work provides a new way to design an efficient homogeneous heterojunction photocatalyst.