Preparation And Photocatalytic Performance Of Bi₂Fe₄O₉@ZnIn₂S₄

It is well known that hydrogen is a carbon-free clean energy source with high energy density,which can effectively solve the energy crisis and greenhouse effect problems caused by the excessive use of fossil fuels.Among various technologies,the photocatalytic reaction using solar energy is an ideal way to produce hydrogen.At the same time,people’s health and quality of life are threatened by the increasingly serious environmental pollution problem.Among numerous pollutants,the presence of organic pollutants such as tetracycline（TC）and bisphenol A（BPA）poses a great threat to human health and ecosystems due to their bioaccumulation and long-term persistence.There are many technologies used to treat pollutants in the environment,such as adsorption,biological treatment,piezoelectric catalysis,etc.Experts and scholars favor the use of photocatalysis technology to treat refractory organic pollutants,which can be attributed to its important advantages in terms of process economy and sustainability.The subject of this paper is the layered structure of Bi₂Fe₄O₉,which is one of the effective photocatalysts for the degradation of organic pollutants,which can be attributed to its strong oxidation ability due to its more positive valence band potential.However,individual photocatalysts face severe recombination of photogenerated carriers,which makes the photocatalytic performance of Bi₂Fe₄O₉ still unsatisfactory.In this paper,Bi₂Fe₄O₉ with layered structure was firstly prepared by hydrothermal method and annealing strategy.And then ZnIn₂S₄ with layered structure was grown on the surface of Bi₂Fe₄O₉ by hydrothermal method,thus forming Bi₂Fe₄O₉@ZnIn₂S₄ composite photocatalyst.Firstly,a series of characterization analysis as well as photoelectric performance analysis of Bi₂Fe₄O₉ and its composites were carried out.Then TC and BPA were selected as the target pollutants to test their photocatalytic degradation performance,and then their photocatalytic hydrogen production performance was continued to be explored.Finally,the photocatalytic mechanism of Bi₂Fe₄O₉@ZnIn₂S₄ heterojunction photocatalyst was investigated.The specific studies in this paper are shown as follows:（1）Bi₂Fe₄O₉ with layered structure was prepared by hydrothermal method and annealing strategy.Bi₂Fe₄O₉ with different sizes and thicknesses were prepared by controlling the hydrothermal time.After a series of characterization analysis and performance tests of photocatalytic degradation of TC and BPA,the optimum hydrothermal synthesis time of Bi₂Fe₄O₉ was obtained as 6 h.This can be attributed to the higher dispersion and smaller thickness of Bi₂Fe₄O₉ with a hydrothermal synthesis time of 6 h,which inhibits the recombination of photogenerated carriers to a greater extent.（2）To further improve the photocatalytic performance,Bi₂Fe₄O₉@ZnIn₂S₄ heterojunction photocatalysts were prepared by hydrothermal method.It was demonstrated by a series of characterizations that the charge transfer pathways in the Bi₂Fe₄O₉@ZnIn₂S₄ composite photocatalyst conform to the S-scheme mechanism.The highest charge separation efficiency of the composite photocatalyst was demonstrated by the photoelectric conversion performance analysis.The test results of the degradation experiments were analyzed,and the results showed that the photocatalytic degradation efficiency of TC and BPA reached 99.9%and 98.7%,respectively,within 105 min,and the hydrogen production rate reached 3964.26 μmol h^-1 g^-1,which was 12.1 times higher than that of pure ZnIn₂S₄.The construction of S-scheme heterojunctions leads to the improvement of photocatalytic performance.In addition,the fabricated Bi₂Fe₄O₉@ZnIn₂S₄ heterojunction photocatalyst has higher stability.