Preparation Of Bi₂WO₆-based Photocatalyst And Study On Its Performance In The Degradation Of Toluene Under Visible Light

When Bi₂WO₆ was applied to catalysis under visible light,it was limited due to its low light utilization and poor efficiency of charge separation.So in this project,Bi₂WO₆ was used as main catalyst to expand the range of light response and improve the efficieny of charge specration,Bi₂WO₆compounded with Ag₃PO₄,rGO and modified itself.It is helpful to improve the degration performance of VOCs under visible light.The relationship between catalyst and catalytic performance was analyzed by a series of characterization.And major results are as follows:（1）Z-type Ag₃PO₄/Bi₂WO₆ was prepared to broaden the range of light.Bi₂WO₆ was synthesized by a facile hydrothermal reaction.Ag₃PO₄ was loaded on Bi₂WO₆ by silver ammonia precipitation method,and the photocatalytic activity of Ag₃PO₄/Bi₂WO₆to toluene was investigated under different molar ratios.XRD characterization showed that there was no other impurity peaks in it.Which indicated the Ag₃PO₄/Bi₂WO₆ with high purity.UV-vis DRS and PL analyzed the optical properties of Ag₃PO₄/Bi₂WO₆and Bi₂WO₆.The optical photoresponse range of Ag₃PO₄/Bi₂WO₆had been expanded and the separation of electron-hole had been accelerated,so then the separation of charges had been efficiently improved.The activity was significantly improved when tolene was degraded under visible light because of the introduction of Ag₃PO₄.The activity of toluene was best when the molar is 1 to 2 between Ag₃PO₄and Bi₂WO₆,which could reach to 80%.And CO₂mineralization rate reached to36.2%in 180 min under visible light.（2）Ag₃PO₄/Bi₂WO₆/rGO was synthesized to improve the separation of charges.On the basis of the optimal molar ratio of Ag₃PO₄/Bi₂WO₆,the GO is reduced to rGO by using hytrazine hydrate as the reducing agent and heating it in a water bath.And a ternary Ag₃PO₄/Bi₂WO₆/rGO catalyst was prepared by immersion and stirring.The photocatalytic activity of Ag₃PO₄/Bi₂WO₆/rGO to toluene was investigated under different mass ratios.XRD showed that the introduction of rGO did not change the crystal of Ag₃PO₄/Bi₂WO₆.It could be seen from TEM that there was a close contact interface between Ag₃PO₄,Bi₂WO₆ and rGO.The optical properties of Ag₃PO₄/Bi₂WO₆/rGO was characterized by PL.And the results showed that the current carrier of Ag₃PO₄/Bi₂WO₆/rGO was significantly separated when rGO was dropped into it.Also the electron-hole pairs was effectively departed.The activity performance showed that the degradation effect of ternary Ag₃PO₄/Bi₂WO₆/rGO on toluene is significantly improved.When the mass ratio of rGO was 5%,The degradation of toluene reached to 90%and CO₂mineralization rate reached to 41.2%in 180 min under visible light.（3）Bi₂WO₆ with Bi defect was synthesized to improve the separation of electron-hole pairs.Monolayer Bi₂WO₆ was prepared by adjusting the hydrothermal temperature of Bi₂WO₆ synthesis process.Bi₂WO₆ with Bi defect was prepared by secondary hydrohermal reaction with H₂SO₄solvent.Taking toluene as the test project,the performance of Bi₂WO₆ with Bi defect was invesigated.XRD showed that the crystal form of Bi₂WO₆ did not change after treating with H₂SO₄.The lamellar structure of Bi₂WO₆ treated with H₂SO₄ still remained which were characterized by SEM and TEM.AFM showed that Bi₂WO₆ treated with H₂SO₄ was still a single layer,which ensured that surface defects later.XPS element content analysis showed that Bi atoms of Bi₂WO₆were lost after H₂SO₄ treatment.EDS mapping reached a consistent conclusion,combineing with ESR characterization to prove the existence of Bi defects.UV-vis DRS and VB-XPS showed that compared with Bi₂WO₆,the forbidden band width of Bi-defective Bi₂WO₆ has not changed much,but its conduction band and valence band are both shifted to the negative direction.The PL results showed that the existence of Bi defects significantly improves the electron-hole separation.After performance testing,it was found that Bi-defective Bi₂WO₆effectively improved the photocatalytic efficiency.Among them,1M-mBWO had the best degradation effect,and the degradation rate reached to 82%and CO₂mineralization rate reached to 40%in 180 min under visible light.（4）With the increase of light intensity,1M-mBWO promoted the degradation of toluene to some extent.When the lamp dietance was more than15 cm,the degradation effect decreased.The increase in oxygen concentration also promotes the degradation process,but too high concentration will inhibit the reaction from proceeding.With the increase of initial concentration of toluene,the degradation effect of 1M-mBWO decreased.