Research On Properties Of Degradation MB And Hydrogen Production Based On Modified TiO₂ Photocatalytic Materials

At present,every country is facing the problems of environmental pollution and the lack of energy.Therefore,developing clean energy,promoting environmental protection,creating sustainable and energy-efficient technologies are the most pressing challenges which scientists face today.The discovery of semiconductor photocatalysis provides a new idea for environmental pollution control and new energy technology development.TiO₂ has been studied intensively in the field of semiconductor photocatalysis due to the advantages of good chemical stability,low price and non-toxicity.However,due to the bandgap width of TiO₂ materials（3.2eV）,it can only absorb a small part of the sunlight.At the same time,electrons and holes produced in photocatalytic reactions are easily compounded,which greatly reduces their quantum conversion efficiency and thus limits their production application.Therefore,in order to improve the practicability of TiO₂,various methods need to be explored to solve the above problems.In recent years,in allusion to adjust of the absorption spectrum range of TiO₂ and reduce of photoelectron and hole recombination efficiency,many researchers at domestic and abroad through the noble metal deposition,semiconductor composite,Ion doped and other methods to modify it.In this paper,the materials with high photocatalytic performance were prepared that applying three methods to modifying TiO₂ by selecting several materials.The main research contents and results are as follows:1、Ag-TiO₂ coated TpTa-COF（Ag-TiO₂@COF）photocatalystAg-TiO₂@COF composite materials were prepared by hydrothermal method.TiO₂was supported to grow on the surface of TpTa-COF,and then the noble metal Ag was deposited on the surface.After eight hours of photolysis,hydrogen production efficiency of the prepared photocatalyst was reached to 2967.25μmol g^-1 h^-1.Moreover,due to the support of COF,TiO₂ and Ag-TiO₂@COF have smaller particle size（2.3nm,6.39nm）.2、Mo,Yb and Tm ions were doped with TiO₂（Mo-TiO₂,Yb-TiO₂,Tm-TiO₂）photocatalystMo-TiO₂,Yb-TiO₂,Tm-TiO₂ photocatalysts were prepared by microwave-assisted hydrothermal method.By degradation the methyl blue,the sample of the optimum doping ratio was selected,and then the hydrogen was produced by photolysis water for eight hours.Draw three hydrogen production efficiency are 260.75μmol g^-1 h^-1、50μmol g^-1 h^-1、67.5μmol g^-1 h^-1 respectively.The absorption spectrum of the doped catalyst was redshifted obviously,and the fluorescence intensity was greatly reduced,so it is a kind of photocatalyst with great potential.3、Fe₂O₃ is coated with TiO₂（Fe₂O₃@TiO₂）photocatalystFe₂O₃@TiO₂ nanoellipsoid photocatalyst was prepared by microwave-assisted hydrothermal method.The prepared sample has an ellipsoidal core-shell structure,and the heterogeneous structure of Fe₂O₃ and TiO₂ formed at the core-shell junction can effectively improve the carrier migration rate.The photocatalytic degradation rate of methylene blue by Fe₂O₃@TiO₂ reaches 87.5%within 45min under visible light.4、TiO₂ nanoflower composite graphene（TiO₂-G）photocatalystTiO₂-G composite materials were prepared by hydrothermal method.Under visible light,photocatalytic degradation of methylene blue solution was significantly better than that of P25 photocatalytic material from Germany.Using the characteristics that the Fermi energy level of graphene was significantly lower than that of the conduct band of TiO₂,in the photocatalytic process,graphene can quickly receive the photogenerated electrons of TiO₂,thus effectively reducing the recombination of electrons and holes.In this paper,four methods of TiO₂ modification were proposed,all of which could improve the photocatalytic activity of TiO₂.Ag-TiO₂@COF,Mo-TiO₂,Yb-TiO₂,Tm-TiO₂ photocatalysts were prepared by means of noble metal deposition and ion doping,which had the hydrogen production rate of millimolar magnitude,and provided a good reference value for the design of efficient TiO₂ photocatalyst.Fe₂O₃@TiO₂core-shell structure and the self-assembled nanoflower structure of TiO₂-G were obtained by adjusting the micro morphology of TiO₂,which have excellent photocatalytic degradation activity to MB under visible light.