Study On The Performance And Machanisms Of Transition Metal Oxide@g-C₃N₄ Photocatalytic Reduction Of U（Ⅵ）

In recent years,with the rapid development of modern industry,as a kind of clean energy,nuclear energy is widely concerned around the world.In the past few decades,human-centered activities,such as uranium mining and processing,improper nuclear waste management and nuclear safety accidents,have inevitably released large amounts of uranium into the natural environment.The resulting pollution is a problem facing the world.Photocatalytic technology can use solar energy to transform and degrade pollutants in the environment,and play an important role in the treatment of uranium pollution.Graphite carbon nitride（g-C₃N₄）has attracted much attention in the field of photocatalysis in recent years.Benefit from suitable band gap,wide spectral response capability and adjustable band structure,g-C₃N₄ is known as one of the most potential photocatalytic materials.However,its structural defects lead to its shortcomings of high photo-generated carrier recombination rate and low electron transport efficiency.By modifying g-C₃N₄ to improve its photocatalytic activity,it is of great significance to use it for photocatalytic reduction of U（VI）.In this paper,the advantages of transition metal oxides are used to introduce transition metal oxides into g-C₃N₄.We adjust the band structure of g-C₃N₄ and improve its photoelectric performance to improve the efficiency of photocatalytic reduction of U（Ⅵ）.The specific content is as follows:（1）The Fe₂O₃@g-C₃N₄ nanocomposite was successfully prepared by the calcination method.The nanocomposite was used it in the study of photocatalytic reduction of U（Ⅵ）.The results show that Fe-CN-S-3,which has the best photocatalytic performance,is 3.4 times higher than that of g-C₃N₄,and showed prefect repeatability and stability in five photocatalytic cycle experiments.The introduction of Fe₂O₃ enhances the light absorption capacity of the material,and provides additional electrons to increase the Fermi energy level.So that the conduction band potential of Fe-CN-S-3 is reduced by 0.15 V compared with g-C₃N₄.The photocatalytic reduction ability is enhanced.（2）The monoclinic phase WO₃ was fixed on the surface of g-C₃N₄ by chemical precipitation method,and the WO₃@g-C₃N₄ nanocomposite photocatalyst was successfully prepared.The introduction of WO₃ broadens the visible light response range.The oxygen vacancy defect of WO3 is conducive to electron conduction,can effectively inhibit the recombination of photogenerated carriers,and optimize the energy band structure of the composite material.Among them,the conduction band potential of W-CN-3 is 0.10 V lower than g-C₃N₄,the photocatalytic reduction rate is 1.8 times higher than pure g-C₃N₄.And showed prefect stability in five photocatalytic cycle experiments.（3）The nanowire-likeα-Mn O₂ was synthesized by in-situ deposition method using metal salt,connected and fixed on the surface of g-C₃N₄,and successfully prepared Mn O₂@g-C₃N₄ nanocomposite photocatalyst.the photocatalytic reduction rate of Mn-CN-3 was increased by 2.4 times compared with pure g-C₃N₄,and it showed perfect photocatalytic activity and stability in five photocatalytic cycle experiments.The introduction of Mn O₂ broadens the visible light response range of the material.The special linear structure of Mn O₂ can improve the electron transmission efficiency and optimize the electron transmission channel at the same time.The conduction band potential of Mn-CN-3is 0.05 V lower than g-C₃N₄,and the photocatalytic ability is enhanced.