Preparation Of TiO₂-based Nanocomposites Photocatalysts And Study On Their Photodegradation Performances For Dyes

Titanium dioxide(TiO2)has become the viable choice to solve this dye pollution problem due to its characteristics of oxidative degradation for organic matter in wastewater under a specific light irradiation.However,TiO2 is unable to meet commercial applications in daily conditions,for a strong absorption peak in the ultraviolet region(λ<400 nm)and extremely low catalytic efficiency in the visible region.In this work,a series of microstructure improvement,noble metal nanoparticle deposition,surface morphology adjustment,carbon-based material doping,biphasic crystalline compounding,semiconductor compounding and reduction treatment were carried out to address the problems that TiO2 cannot effectively responding to visible light,low photogenerated carrier transport efficiency and high photogenerated electron-hole pair complexation rate.Combining gel-solvothermal method with high temperature thermal annealing technology,TiO2based nanocomposites photocatalysts with high catalytic degradation activity under different three-dimensional structures were prepared.In this study,the gel-solvothermal method was firstly applied to successfully develop Ag@TiO2 NPs composite photocatalyst through a simple and safe process.The diameter of TiO2 NPs in the synthesized Ag@TiO2 NPs was stable in the range of 30 nm-40 nm,and AgNO3 was successfully reduced to nano-Ag monomers(d<10 nm)and uniformly deposited on TiO2 NPs.Since the modification of Ag NPs can boost the catalytic activity of the photocatalyst under UV light and the response ability under visible light,to a certain extent,increasing the molar amount of Ag NPs loaded could further enhance the reaction activity of the photocatalytic system in the process.When the molar ratio of Ag to Ti was 0.5%,the optimal loading could be achieved.After 180 minutes of UV light irradiation,the prepared Ag@TiO2 NPs could catalytically degrade 79.49%MO dyes,which was 2.7 times that of pure TiO2 NPs.Besides,after 180 minutes of visible light irradiation,it could catalytically degrade 50%MO dyes.It was 2.6 times the catalytic efficiency of pure ones.Limited by its structural defects,zero-dimensional(0D)nanoparticles do not have the core competitiveness as high-efficiency photocatalysts.Therefore,in this study,by means of constructing a 1D or 2D TiO2-based composite nanomaterial system,the microstructure of TiO2 was adjusted(0D→1D/2D).GO was introduced during the growth of TiO2 nanosheets(TiO2 NST),and a 2D composite photocatalyst RGO/TiO2 NST based on RGO was formed via HF morphology modifier.Through a series of reactions,in addition to the presence of Ti4+,the composite photocatalyst RGO/TiO2 NST also formed a tight chemical bond with GO during the growth of the TiO2 NST lattice.RGO and high-activity(001)TiO2 NST produced a synergistic effect,which effectively improved the photocatalytic activity of 2D TiO2 nanomaterials.At the same time,regulating the ratio of the two could attain the optimal photocatalytic degradation performance.When the mass ratio of GO to Ti is 2%,the composite photocatalyst RGO/TiO2 NST could catalytically degrade 99.05%MO dyes with visible light for 180 min,which was 10 times the catalytic efficiency of TiO2NST.Considering the safety and productivity of the production process,this research focused on the production of green,safe and high-performance 1D TiO2 nanowires.The gel-solvothermal method was utilized to adjust the anatase/TiO2(B)two-phase 1D TiO2(AB)NWs,and then through the loading of g-C3N4 and Ti3+self-doping modification,finally successfully synthesized g-C3N4/Ti3+-TiO2(AB)NWs composite photocatalyst.The Ti element in the composite photocatalyst had both Ti4+and Ti3+valence,representing the successful formation of Ti3+self-doping and oxygen holes.The experimental results showed that when the mass ratio of raw material melamine to TiO2(AB)NWs was 5:1,the optimal addition amount could be gained.After 150 min of visible light irradiation,98.78%of MO could be catalytically degraded,which was 6.3 times of TiO2(AB)NWs.This high catalytic efficiency was supported by the synergistic effect of TiO2(AB),g-C3N4 and Ti3+self-doping.In this paper,through a series of TiO2 modification,nano TiO2-based composite photocatalysts with high catalytic degradation activity under different stereoscopic structures were prepared to realize efficient and stable photocatalytic degradation ability.To some extent,it provided a new option for TiO2 modification,and a new perspective for the construction of composite photocatalysts with various threedimensional structures.