Preparation Of TiO₂-based Superhydrophobic Material And Research On Its Photocatalytic Performance

Since the beginning of the 21st Century,dust pollution on building wall in modern city is becoming increasingly severe.With the general evoking awareness of environmental protection,people have taken various ways to deal with this problem,for example,manual cleaning.However,among these methods heavy workload and high cost are also the trouble.So building wall material with self-cleaning function stands out.The core of self-cleaning lies in superhydrophobicity and photocatalytic activity,superhydrophobicity refers to contact angle between water and sueface greater than 150° and rolling angle less than 10°.The excellent hydrophobicity makes it possible in applications of self-cleaning,fluid drag reduction,oil-water separation and so on.Photocatalytic means that organic matter can be decomposed when under a specific light source,and TiO₂ is a kind of semiconductor material with certain photocatalytic performance.However,the narrow spectral absorption range and low separation efficiency of electron-hole pairs limit its further development.In this thesis,TiO₂-SiO₂?TS?was prepared by sol-gel method and mixed with PDMS of a certain percentage.The mixture was then coated on the surface of glass slides by a strategy known as "impregnation-pulling".A rough surface structure is constructed and the surface energy can be reduced by adding PDMS.The properties of microstructure,photocatalytic activity and hydrophobicity of the as-obtained material have been investigated and analyzed:?1?TiO₂ was prepared by hydrolysis of the amorphous,meta-titanate agglomerated particles with tetrabutyl titanate,and the sol-gel method was used to functionalize the TiO₂ sol.After the samples had been annealed at different temperatures,the TS composites were obtained?n?Si?:n?Ti?=0.3?.The results show that the surface of the composites is fluffy presenting porous structure.After annealing,the surface porous structure is denser and more uniform.The results of SEM and XRD also show that when the annealing temperature is set above 600?,the large fraction of the microstructures of material surface resembles to that of a lotus leaf,in which TiO₂ is mainly anatase-type.?2?The above composite material TiO₂-SiO₂ was mixed with PDMS and toluene at ratio of 4:1:5.The mixture was coated on the glass slides,dried at room temperature or in an oven.The result of contact angle measurements shows that TiO₂-SiO₂@PDMS based on TS at different annealing temperatures has different contact angles.Among them,the 600?-annealed,TS-600@PDMS has the largest contact angle up to 157°.Besides,the super-hydrophobic surface of the sample endows physically self-cleaning property,meaning that the dust scattered on the surface can be carried away by water droplets;?3?The TiO₂-SiO₂ and TiO₂-SiO₂@PDMS have been applied in photocatalytic degradation of methylene blue solution,formaldehyde steam and benzene steam.The results showed that TS annealed at 500? has the highest degradation rate,and the degradation rate was 99.9%when irradiated under UV for 2h,slightly higher than that of TS-600.When it comes to the degradation rate of formaldehyde and benzene exposed to UV for 3h,the degradation rate is 95.5%and 95.7%,respectively.According to these results,it is natural to conclude that TS@PDMS coated on glass slides possess both super-hydrophobicity and photocatalytic activity,which is promising to have wide application prospects which require self-cleaning.