Preparation Of Bismuth-based Semiconductor Composite Photocatalysts And Study On Its Photocatalytic Properties

In recent years,environmental pollution problems have become the focus of world attention.Semiconductor photocatalysis is attracting more and more attention as one of the most promising solutions to these problems.As a’green’technology,it can be used to remove various pollutants by visible light.Bismuth（Bi）-based semiconductors,an emerging class of photocatalysts with layered structures,typically with visible light responsiveness,suitable band gaps and well-dispersed valence bands,have been widely demonstrated to exhibit excellent photo-oxidation capabilities in the removal of organic pollutants.However,there are two inherent limitations in the use of Bi-based semiconductors.One is that single-component Bi-based semiconductors cannot simultaneously have a high redox capacity and good solar energy utilisation.Secondly,the photocatalytic activity of Bi-based semiconductors is affected by the compounding efficiency of photogenerated electron-hole pairs.The construction of heterojunction composite photocatalysts by compounding with other semiconductors is an effective way to improve the photocatalytic activity of Bi-based semiconductors.In this study,Z scheme heterojunction photocatalysts with visible light response were prepared by using Bi-based semiconductors（Bi OCl,BiOBr,and Bi₂O₂CO₃）as the research objects.The main studies are as follows.Firstly,a novel Z scheme heterojunction FeIn₂S₄/Bi OCl composite photocatalyst was successfully synthesized by a facile hydrothermal method using FeIn₂S₄（FIS）microspheres as the precursor.At 8 wt%of FIS content,the FIS/Bi OCl composite photocatalyst degraded rhodamine B（Rh B）more efficiently than pure FIS and Bi OCl,with 93%degradation efficiency of Rh B within 50 min.The broadening of the visible light absorption range and the reduction of the electron-hole complexation efficiency originated from the complexation of FIS and Bi OCl to form a Z scheme heterojunction,which ultimately improved the photocatalytic activity.Sencondly,a novel Z scheme heterojunction FeIn₂S₄/BiOBr composite photocatalyst was synthesized by a simple solvothermal method using FIS microspheres as the precursor.In the photocatalytic degradation of Rh B,the composite photocatalyst FIS10/BiOBr showed excellent photocatalytic activity and stability,exhibiting a degradation efficiency of 96%within 60 min,which was about 5.33 and 2.59 times higher than that of pure FIS and BiOBr,respectively.The Z scheme heterojunction photocatalytic degradation mechanism was applied to the FeIn₂S₄/BiOBr composite photocatalyst.Finally,the double Z scheme heterojunction BiOBr/g-C₃N₄/Bi₂O₂CO₃（CN）composite photocatalyst was rationally designed and successfully synthesized by hydrothermal method.Compared with pure BiOBr,g-C₃N₄ and Bi₂O₂CO₃,the resulting sample 0.025CN exhibited higher photocatalytic activity for Rh B degradation,with 98%efficiency for Rh B degradation within 60 min.The composite photocatalyst CN promotes the photocatalytic activity due to the formation of a double Z scheme heterojunction for efficient charge separation and enhanced visible light absorption.In summary,Bi-based semiconductor composite photocatalysts have potential applications in the field of removal of organic pollutants from wastewater.The research results in this paper provide a reference for the study of improving the photocatalytic activity of single-component Bi-based semiconductors and lay a good foundation for their further practical applications.