Ti₃C₂ MXene Layered Composite And Its Photocatalytic Properties

Semiconductor-based photocatalytic technology not only can effectively solve the resource crisis and environmental pollution,but also the technology is green,driven by solar energy and can be performed at room temperature and pressure,so it has attracted much attention.Conventional photocatalysts are usually metal oxides or metal sulfides,however,single metal oxide/sulfide photocatalysts cannot combine light energy utilization and strong redox ability,such as CdS,Bi₂MoO₆,g-C₃N₄,and photogenerated carriers and holes are easy to recombine,leading to reduced photocatalytic performance,so finding co-catalysts that can improve catalytic performance is the key of photocatalysis technology.Two-dimensional layered transition metal Carbides/Nitrides（MXene）are considered as promising alternatives to noble metal co-catalysts due to their high specific surface area,excellent electronic properties and abundant surface active sites,among which the most representative one is Ti₃C₂ MXene,which can significantly reduce the charge migration distance and improve the separation effect of electron-hole pairs due to the typical lamellar structure,and effectively improve the photocatalytic catalytic activity.In this paper,CdS/Ti₃C₂,PAN/Bi₂MoO₆/Ti₃C₂,g-C₃N₄/Ti₃C₂ composites with high photocatalytic activity were prepared by in situ growth method,electrostatic spinning method and thermal expansion method,respectively,with the aim of obtaining highly active photocatalysts,and their photovoltaic and photocatalytic properties were tested experimentally.The main research of this thesis is as follows:（1）CdS/Ti₃C₂ MXene layered composite photocatalysts were successfully synthesized by hydrothermal in situ growth method.the doping of Ti₃C₂ MXene resulted in the effective separation of electron-hole pairs and greatly improved the photocatalytic hydrogen production performance of CdS under visible light,in which the best ratio sample CM-0.06 layered composite photocatalyst achieved a hydrogen production efficiency of 1295μmolg^-1h^-1,which is about 6.7 times that of pure CdS.The experimental results show that a small amount of Ti₃C₂ MXene can significantly enhance the visible light absorption of the composites,compared CdS with CdS/Ti₃C₂layered composite photocatalysts have better visible light response and smaller electron transfer impedance,more photogenerated carriers and faster electron mobility lead to increased photocatalytic activity.（2）PAN/Bi₂MoO₆/Ti₃C₂ fibrous membranes were prepared by electrostatic spinning method.Compared with the powder sample,the fiber membrane has a high efficiency（90%）in photocatalytic degradation of tetracycline and also has a very good cycling stability.Firstly,the Bi₂MoO₆/Ti₃C₂ powder-like layered composite photocatalyst was prepared,and it was found that the photocatalytic efficiency showed a parabolic change with the increase of the co-catalyst Ti₃C₂ MXene,so the best performance of BT-0.05 layered composite photocatalyst was selected to prepare the fiber membrane,in which the tetracycline photocatalytic efficiency of PAN/BT（0.2）fiber membrane reached 90.3%.The tetracycline photocatalytic efficiency of the PAN/BT（0.2）fiber membrane reached 90.3%,and the fiber membrane material can be used as a photocatalytic device and easily recycled.The experimental results show that the prepared PAN/Bi₂MoO₆/Ti₃C₂ fiber membrane has good photocatalytic activity,good regeneration performance,and low cost for exploration,which opens up a new way for efficient degradation of tetracycline in water.（3）2D/2D g-C₃N₄/Ti₃C₂ layered composite photocatalysts were synthesized by direct calcination of a mixture of multilayer Ti₃C₂ particles and urea by thermal expansion method.In this thermal expansion method for the preparation of composite photocatalysts,urea can be used not only as a gas template to exfoliate the multilayer Ti₃C₂into thin layers,but also as a raw material to generate g-C₃N₄ for the in-situ preparation of g-C₃N₄/Ti₃C₂ composites.The obtained composite photocatalysts exhibited excellent photocatalytic degradation performance of tetracycline under visible light,in which the 5TC composite photocatalysts achieved 90.1%degradation efficiency,which was significantly higher than that of pure g-C₃N₄,attributed to the formation of 2D/2D g-C₃N₄/Ti₃C₂ heterojunctions with close interfacial contact between the two lamellar structures,which facilitated the rapid electron transfer between the bulk phases,thus improves the effective separation of photogenerated charge carriers,which in turn enhances the photocatalytic activity.This work provides an idea for the facile construction of two-dimensional composite photocatalysts.Figure[33]table[6]reference[141]...