Study On Preparation And Photoactivity Of TiO₂ Hollow Spheres And Its Composites

Over the years,with the rapid development of the global economy,the problem of environmental pollution has become increasingly serious.As a typical photocatalytic semiconductor material,titanium dioxide?TiO₂?has a great application prospect in pollution treatment due to its stable physical and chemical properties and high catalytic performance.At the same time,TiO₂ has a lot of disadvantages,such as a wide band gap,low utilization rate of sunlight and high recombination rate of photogenerated electron-hole pairs,which limit its further application.Therefore,how to modify TiO₂nanomaterials to overcome the above shortcomings has become an important research topic.In this work,a template of SiO₂ microspheres was firstly prepared by St?ber method.The SiO₂@TiO₂ core-shell structure was obtained through the hydrolysis of tetrabutyl titanate?TBT?.Then,followed by calcination and corrosion to remove the template to give the TiO₂ hollow spheres.Finally,double-shell structural TiO₂@PANI hybrid material was successfully constructed via in situ polymerization process with polyvinylpyrrolidone?PVP?as surfactant,and ammonium persulfate as initiator.TiO₂hollow spheres have mesoporous structure,which is in favour of the coating of PANI.The synergistic effect between PANI and TiO₂ can promote the separation of the photogenerated charge carriers,and extend the absorption range,thereby enhance the photodegradation efficiency of pollutant.The photocatalytic activitiy,kinetic simulation and photocatalytic mechanism of the double–shell structural TiO₂/PANI hybrid material were also studied.The specific research results were as follows:?1?By adjusting the amount of TBT?0.25,0.5,and 0.75 mL?,we synthesized the TiO₂ hollow spheres with different shell thicknesses with SiO₂ microspheres as template.The obtained SiO₂ spheres were with the diameter of about 280 nm.After removal of the SiO₂ template,the shell thicknesses of TiO₂ hollow spheres were about 12,20,or 50nm,respectively.The crystal structure of TiO₂ was anatase phase.The photocatalytic activitiy of the TiO₂ hollow spheres with different shell thicknesses were assessed by degradation of MO under UV light irradiation.The experiment results showed that the TiO₂ hollow spheres with shell thickness of 50 nm displayed the highest photocatalytic activitiy.After 2 h under UV light,the photocatalytic degradation of MO was 55.8%.?2?The double-shell structural TiO₂@PANI hybrid material was prepared by coating a layer PANI on the surface of the TiO₂ hollow spheres with thickness of 50 nm,with polyvinylpyrrolidone?PVP?as surfactant,and ammonium persulfate as initiator.Moreover,by adjusting the amount of ANI?1,5,10 and 15?L?,we synthesized the TiO₂@PANI hybrid material with different PANI shell thicknesses.The characteration results showed that the TiO₂ hollow spheres were coated by PANI successfully,which shell thicknesses were approximately 5,8,16,or 20 nm,respectively.The TiO₂@PANI hybrid material had high specific surface area and absorption rate due to the mesoporous structure.In addition,the analysis of UV-vis diffuse reflectance spectroscopy indicated that the absorption spectrum of TiO₂@PANI hybrid material had a red shift,which extended the absorption range.Compared to TiO₂ hollow spheres,the TiO₂@PANI hybrid material possessed outstanding photocatalytic activitiy,photodegradation efficieny and reusability.The photodegradation efficienies of MO were approximately 90.9%after 2 h under UV light and 97.1%after 4 h under visible light respectively.