Study On Preparation And Photocatalytic Properties Of BiVo₄-based Composites

In recent years,the rapid development of the textile industry has caused a large number of organic pollutants(such as MB,TC,etc.)in dye wastewater to pollute the water.BiVO₄-based composites were used to photocatalytically degrade organic pollutants such as MB and TC,so as to achieve the purpose of purifying water.BiVO₄ is a visible light catalyst with narrow band gap.Due to the rapid recombination of photogenerated electrons and holes,its application in the field of photocatalytic degradation is limited.In this paper,semiconductor heterojunctions are constructed by combining BiVO₄ with Zn₂SnO₄ and Ag₃PO₄,respectively,BiVO₄/Zn₂SnO₄ and BiVO₄/Ag₃PO₄ composites are synthesized to improve the separation efficiency of photogenerated electrons and holes in BiVO₄,thereby improving the photocatalytic activity of BiVO₄.The composition,morphology and optical properties of BiVO₄/Zn₂SnO₄ and BiVO₄/Ag₃PO₄ composites were characterized by XRD,FT-IR,XPS,SEM,DRS,PL,EIS and transient photocurrent response.Under visible light irradiation conditions(300W xenon lamp,?>400 nm),the photocatalytic degradation efficiency of BiVO₄-based composites on MB and TC in water was tested,and the photocatalytic degradation cycle stability of BiVO₄-based composites was determined.The photocatalytic degradation effects of BiVO₄/Zn₂SnO₄ and BiVO₄/Ag₃PO₄composite materials on MB and TC are as follows:(1)The BiVO₄/Zn₂SnO₄ photocatalysts was prepared by hydrothermal method to degrade MB.When visible light irradiates the BiVO₄/Zn₂SnO₄ composite material,the electrons in the CB of BiVO₄ will transition to the CB of Zn₂SnO₄,while the holes on the VB of Zn₂SnO₄ will transition to the VB of BiVO₄.The electrons on the CB of Zn₂SnO₄ can reduce O₂ to·O₂^-,h⁺and·O₂^-can oxidatively degrade MB.When the percentage of Zn₂SnO₄ to BiVO₄ is 7%(BZ7),the photocatalytic degradation efficiency of MB is 99.3%after 80 min of visible light irradiation.The kinetic constants of BZ7(0.0473 min^-1)are 2.2 times that of BiVO₄(0.0215 min^-1)and 10.3 times that of Zn₂SnO₄(0.0046 min^-1),respectively.The degradation efficiency of MB by BZ7 was90.3%after five cycles in a light time of 80 min,which indicated that BZ7 composite had good photocatalytic degradation stability.The BZ7 active species capture experiment confirmed that h⁺and·O₂^-are the main active species for the degradation of MB in the photocatalytic process.(2)The BiVO₄/Ag₃PO₄ composite photocatalysts was prepared by hydrothermal method and chemical precipitation method to degrade TC.when visible light is irradiated the BiVO₄/Ag₃PO₄ composite material,while the electrons on the CB of Ag₃PO₄ will transition to the CB of BiVO₄,and the holes on the VB of BiVO₄ will transition to the VB of Ag₃PO₄.The electrons on the CB of BiVO₄ reduce O₂ to·O₂^-,h⁺and·O₂^-can oxidatively degrade TC.When 10%Ag₃PO₄ is combined with BiVO₄(BA10),the photocatalytic degradation efficiency of TC is 89.9%after being irradiated with visible light for 60 min.The kinetic constant of BA10(0.0276 min^-1)was higher than that of BiVO₄(0.0154 min^-1)and Ag₃PO₄(0.0081 min^-1).BA10 degrades TC five times in 60 min,and its efficiency is 80.2%.The results of the active species capture experiment of BA10 show that the h⁺and·O₂^-are the main activity factors for photocatalytic degradation of TC.In short,the photocatalysis of BiVO₄-based composites effectively degrades MB and TC,which provides a theoretical basis for the practical application of BiVO₄-based composites to degrade MB and TC.