Study On Preparation And Photocatalytic Activity Of MXene-derived TiO₂ Matrix Composites

Photocatalysis technology has the advantages of mild reaction conditions,simple reaction principle,clean raw materials,no secondary pollution,simple operation and so on.Additionally,there are efficient degradation materials for most organic and dye pollutants.Therefore,it is considered to be one of the most potential technologies.Ti₃C₂is a new type of two-dimensional nano-layered material,which has metal-like properties,excellent electrical conductivity,mechanical properties,photoelectric properties,thermal conductivity,adsorption properties and so on.On the basis of Ti₃C₂,in-situ growth of TiO₂can not only give full play to the performance advantages of Ti₃C₂,but also take into account the advantages of high chemical stability,hydrophilicity and good catalytic activity of TiO₂,and overcome the shortcomings of titanium dioxide application process,such as low electron-hole separation efficiency,wide band gap,narrow visible light absorption boundary and poor adsorption of pollutants.Therefore,this subject is mainly based on TiO₂derived from Ti₃C₂and combined r GO and Zn-Bi₂Mo O₆to achieve the modification of TiO₂and Ti₃C₂/TiO₂.Through the tests of crystal phase morphology,surface composition,optical absorption and electrochemical properties,preparation conditions and composite ratios,and the mechanism of action of new composites Ti₃C₂/TiO₂/r GO and Zn-Bi₂Mo O₆/Ti₃C₂/TiO₂were explored and analyzed.The details of the study are outlined below:（1）In this work,Ti₃C₂/TiO₂photocatalyst was prepared by etching and calcination.TiO₂was derived on the surface of Ti₃C₂to improve the photocatalytic efficiency of pure Ti₃C₂and TiO₂.Subsequently,the TiO₂derived from Ti₃C₂formeds a solid contact surface,and the TiO₂embedded in Ti₃C₂could transfer and separate charges rapidly,which improved the degradation efficiency of the photocatalyst.Additionally,an increase in the calcination temperature,resulted in the photodegradation efficiency increasing until the calcination temperature reached 350℃.Hence,at Ti₃C₂/TiO₂the best photocatalytic performance was obtained,and the degradation efficiency irradiated by simulated sunlight was 75.35%at 60 min,which is 5.5 times higher than that of pure TiO₂（13.3%）.（2）Inspired by the excellent photocatalytic performance of Ti₃C₂/TiO₂in the previous study,Ti₃C₂/TiO₂/r GO heterojunction nanocomposites were successfully prepared via calcination and hydrothermal method to improve the morphology and modify the structure of the nanocomposite.TiO₂was uniformly dispersed on the surface of Ti₃C₂,which made the in-situ load firm,at 71.8%,indicating the successful intercalation of r GO composites.The test and comparison of specific surface area and optoelectronic performance,further confirmed that the improvement in the photocatalytic performance of Ti₃C₂/TiO₂/r GO is due to enhancement in the specific surface area,visible light absorption,photocurrent,charge resistance and photogenerated electron-hole recombination efficiency.Interestingly,the hydrogen production results showed that when the compound ratio of rGO was 12%,the maximum hydrogen production in 4 h was 1671.85μg^-1,and the maximum hydrogen production rate in the first hour was 808.11μg^-1h^-1,which was 3.08 times higher than that of pure Ti₃C₂/TiO₂catalyst(262.66μg^-1h^-1).（3）In this chapter,Zn-MXene/TiO₂/Bi₂MoO₆composites were prepared by self-assembly physical composite method.Through electrochemical tests,UV-vis absorption spectra and photocatalytic performance tests,it was found that the separation efficiency of photogenerated electrons,holes and the charge transfer efficiency of Zn-MXene/TiO₂/Bi₂Mo O₆composites were enhanced,and the resistance of charge transfer became smaller.Besides,the recombination of Bi₂Mo O₆reduced the band gap of the material,which improved the transition of more electrons.When the doping amount of Zn was less than or equal to 4%,Zn ions basically entered into the lattice of Bi₂Mo O₆.Moreover,when the doping amount was also equal to 4%,the best photocatalytic performance of 4ZBMT was obtained after 60 minutes of simulated illumination,and the highest degradation efficiency was 92.0%,which is 6.9 times that of pure TiO₂.