Preparation And Photocatalytic Properties Of Two-dimensional Ti₃C₂-doped TiO₂ Nanofibers

In recent years,environmental problems caused by dye wastewater have attracted wide attention.This kind of wastewater is an important source of eutrophication.It not only has toxicity,but also weakens photosynthesis,makes microorganisms in water unable to degrade,destroys the ecological environment and seriously threatens the living environment of human beings.Traditional treatment methods,such as physical adsorption,chemical oxidation and biodegradation,can remove dyes,but they are costly and easy to cause secondary pollution.The unstable metabolites produced will have adverse effects on human health.Photocatalytic degradation technology is an environmentally friendly green degradation technology,which uses photon energy and ensures mild reaction conditions by using an appropriate photocatalyst.As a semiconductor photocatalyst,TiO₂has good photocatalytic activity,excellent chemical stability and environmental friendliness,and has been widely used in environmental remediation,water decomposition,artificial photosynthesis and other fields.However,there are two shortcomings in the photocatalytic process based on TiO₂.On the one hand,TiO₂ has large bandgap and fast recombination of photogenerated carriers.On the other hand,the commonly used nanoparticles of TiO₂ have the disadvantages of easy agglomeration and small specific surface area,which make its photocatalytic activity not fully developed,and it is difficult to separate and recover TiO₂ nanoparticles from dye wastewater.Therefore,the preparation of a new type of TiO₂-based functional material with high photocatalytic activity and good recyclability will have broad prospects.As a new way of producing one-dimensional nanomaterials,electrospinning has the characteristics of low cost,wide application and simple operation.The prepared nanofibers have the advantages of large specific surface area,high porosity and large aspect ratio.Therefore,one-dimensional inorganic TiO₂ nanofibers prepared by electrospinning can promote charge transfer and enhance photocatalytic activity.In recent years,a new two-dimensional material,MXene,has unique structure and excellent conductivity.Ti₃C₂,as the most widely studied MXene,is considered to be a good platform for the preparation of carbon materials and TiO₂ composites,in which carbon materials can prolong the lifetime of electron-hole pairs,adjust the bandgap and adsorb pollutants.Therefore,two-dimensional Ti₃C₂ was doped into inorganic TiO₂ nanofibers to explore the structural characteristics and photocatalytic properties of doped nanofibers.In this study,inorganic TiO₂ nanofibrous membranes were firstly prepared by sol-gel method combined with electrospinning.Secondly,two-dimensional Ti₃C₂ was obtained by chemical etching of Ti₃AlC₂ with HCl/LiF,and a small amount of two-dimensional Ti₃C₂ with different contents was doped into the precursor solution of TiO₂.Ti₃C₂@TiO₂ nanofibrous membranes with different doping contents were prepared by electrospinning.In this experiment,the morphology and structure of nanofibrous membranes before and after doping were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and X-ray diffraction?XRD?.The elemental valences of the nanofibrous membranes were analyzed by X-ray photoelectron spectroscopy?XPS?,and the mechanical properties of the material were characterized by a tensile tester.The ultraviolet photocatalytic activities of the nanofibrous membranes were characterized by the degradation rates of 10 mg/L methylene blue?MB?and Rhodamine B?RhB?.The results showed that the degradation of different dyes by Ti₃C₂@TiO₂ nanofibrous membranes with different doping contents had the same trend.The optimal photocatalytic activity was achieved when two-dimensional Ti₃C₂ was doped with 12 mg,and the photocatalytic efficiency of two-dimensional Ti₃C₂-doped nanofibrous membrane was significantly improved compared with that of neat TiO₂nanofibrous membrane.It was shown that two-dimensional Ti₃C₂ could form a good interfacial heterostructure with the nanofibers,and form a good conductive network,which was advantageous to the transmission of photoelectrons.In addition,the good recycling performance of Ti₃C₂@TiO₂nanofibrous membranes for dye degradation showed its broad prospects in wastewater treatment applications.