Preparation And Photocatalytic Properties Of Bi₂WO₆ Based Composite

Dye wastewater has the characteristics of complex composition,high toxicity,and difficulty in degradation,causing serious environmental pollution and has been widely concerned.Photocatalytic technology is a low-cost,sustainable Advanced oxidation process,which has broad prospects in the degradation of dye wastewater.The core of photocatalytic technology is photocatalyst.Bismuth tungstate（Bi₂WO₆）is widely used in the field of photocatalytic degradation of organic pollutants due to its narrow bandgap,good visible light absorption performance,and stability.This paper is based on Bi₂WO₆ and introduces graphite nitride carbon（g-C₃N₄）to construct Bi₂WO₆/g-C₃N₄（BWC）composite materials.On this basis,molybdenum carbide（Mo₂C）and indium zinc sulfide（Zn In₂S₄）are respectively composite to prepare Bi₂WO₆/g-C₃N₄/Mo₂C（BWCM）and Bi₂WO₆/g-C₃N₄/Zn In₂S₄（BWC/ZIS）composite materials,and their morphology,structure,and properties are characterized.The photocatalytic performance of the composite materials is studied,and the mechanism of their photocatalytic degradation of RhB is explored.（1）BWC composite materials were prepared by hydrothermal method,and the performance and mechanism of BWC activated persulfate（PS）degradation of RhB under visible light irradiation were studied.The results showed that the composite material with a mass ratio of Bi₂WO₆ to g-C₃N₄ of 6:4 had higher photocatalytic activity.Under the conditions of 0.5 g/L BWC of 6:4,0.5 g/L PS,and 30℃,10 mg/L RhB degradation rate reaches 98.66%in 60 min.Bi₂WO₆ and g-C₃N₄ in BWC 6:4 are both sheet like structures.Bi₂WO₆ grows on the surface of g-C₃N₄,forming a solid heterostructure.The light absorption edge of BWC 6:4 redshifts to 472 nm,and the band gap decreases to 2.50 e V.The main active substances present in this system are holes（h⁺）and superoxide radicals（·O₂^-）.The photo-generated carriers transfer in BWC6:4 follows the Z-type heterojunction mechanism.（2）The BWCM composite material was prepared by electrostatic self-assembly,and its photocatalytic degradation performance and mechanism of RhB were studied.The results showed that the composite material with a Mo₂C mass fraction of 3%in BWCM had the best photocatalytic performance.Under the conditions of 1 g/L BWCM-3%and 30℃,10 mg/L RhB degradation rate reaches 97.64%in 120 min.In BWCM-3%,Bi₂WO₆ and Mo₂C are staggered on the surface of g-C₃N₄,forming a solid heterostructure.The light absorption edge of BWCM-3%is redshifted to 483 nm,the band gap is reduced to 2.23 e V,and the visible light response ability is significantly enhanced.The main active substances present in this system are h⁺and·O₂^-.It is proposed that the transfer of photo-generated carriers in BWCM-3%follows an indirect Z-type heterojunction mechanism,and it is inferred that the photocatalytic degradation of RhB by BWCM-3%mainly involves processes such as N-deethylation,chromophore cleavage,ring opening,and mineralization.（3）The BWC/ZIS composite material was prepared by the solvothermal method,and its photocatalytic degradation performance and mechanism of RhB were studied.The results showed that the composite material with a 50%mass fraction of Zn In₂S₄ in BWC/ZIS exhibited good photocatalytic performance.Under the conditions of 0.4 g/L BWC/ZIS-50%and 30℃,20 mg/L RhB degradation rate reaches 96.20%in 90 min.Zn In₂S₄ in BWC/ZIS-50%was uniformly modified on the surface of Bi₂WO₆ and g-C₃N₄,forming a solid heterostructure.The absorption edge of BWC/ZIS-50%light shifted red to 564 nm,and the band gap decreased to 1.13 e V,significantly enhancing the visible light response ability.The main active substance present in this system is·O₂^-.The transfer of photo-generated carriers in BWC/ZIS-50%is proposed to follow a dual Z-type heterojunction mechanism.