Research On The Enhancement Of The Photocatalytic Property Of TiO-₂ Film On Soda-lime Glass

TiO₂ has multiple merits as a photocatalyst,including cheap price,high oxidation and reduction capability,high optical and chemical stabilities,as well non-toxicity,and it has various promising applications in the areas of environmental purification,light driven water splitting,photocatalytic CO₂ reduction,solar cell and self cleaning,etc.Compared to TiO₂ powder,TiO₂film has the advantage of being easy to recycle and reuse,thus it is more practical for large-scale application.Besides,among various substrate materials,soda-lime glass is considered as one of the ideal substrates for TiO₂ film,because of its low price,wide applications?it is widely used as window glass in architectures,wind shielding glass for vehicles,and glass containers in daily life?,and the excellent chemical and thermal stabilities.Because window glass has large area in buildings,the fabrication of TiO₂ film on soda-lime glass is beneficial for the adsorption of indoor volatile organic compounds?VOCs?,and also can promote the absorption of sunlight,to reach the goal of using sunlight to degrade VOCs and to purify indoor air.Moreover,the fabrication of TiO₂ film on soda-lime glass also bestows glass with the function of self cleaning.Under the illumination of sunlight and the wash of rain,it can keep the cleanness of surface,which can reduce the cost for human maintaining.Thus the fabrication of TiO₂ film on soda-lime glass has attracted numerous attentions of researchers for the last 3 decades.However,the currently reported TiO₂ film fabricated on soda-lime glass still has many defects,and can't meet the requirements for practical application,which includes:?1?the photocatalytic activity of the TiO₂ film fabricated on soda-lime glass is considerably low,and the reason is still unknown;?2?because the content of Na ion in soda-lime glass is very high,it will thermally diffuse into TiO₂ film during calcination,but there are many different opinions on the influences of Na ion on TiO₂ film during the processes of fabrication and application.Most researchers accepted the hypothesis that Na ion is the recombination center of photogenerated electrons and holes of TiO₂,and is detrimental to the photocatalytic activity of TiO₂ film;?3?the recombination rate of the photogenerated electrons and holes of TiO₂ is usually high,leading to the low quantum efficiency and the low use rate of light;?4?researchers rarely use natural sunlight to test the photocatalytic activity of TiO₂ film,thus its still unknown whether TiO₂ film can use sunlight to decompose VOCs or not;?5?the property of light induced hydrophilicity of the TiO₂ film fabricated on soda-lime glass is also needed to be improved.Due to the aforementioned defects and disadvantages,several works have been done in order to solve these problems:1.PVP modified sol-gel method was developed to fabricate TiO₂ film on soda-lime glass with high crystallinity and high photocatalytic activity.The photocatalytic activities of the TiO₂film fabricated through PVP modified sol-gel method were improved for 4.4 and 4.6 times than that of the TiO₂ film fabricated via traditional sol-gel method for the photodegradation of acetone and benzene,respectively.Besides,the influences of PVP content on the photocatalytic activity and the crystallographic property of TiO₂ film also had been systematically investigated,as well as the mechanisms.In addition,the properties of TiO₂ film for the photodegradation of acetone and benzene under sunlight were also tested.2.The effects of Na ion during the fabrication and application processes of TiO₂ film had been systematically studied.The location of Na ion in TiO₂ film as well as its influence on the band structure of TiO₂ also had been investigated.It was found that Na ion would influence the crystallographic properties of TiO₂,however,it was not the recombination center of photogenerated electrons and holes.3.Urea was used as the source of N element to fabricate N doped TiO₂ film on soda-lime glass through PVP modified sol-gel method.By tuning the content of interstitial N,the photocatalytic activity of TiO₂ film for the photodegradation of benzene under UV light was improved for 1.5 times.4.CaH₂ was adopted as the reduction agent for the treatment of TiO₂ film in vacuum at relatively low temperature to create oxygen vacancy on its surface.By tuning the treating temperature and duration to optimize the content of surficial O vacancy,the photocatalytic activity of TiO₂ film for the photodegradation of benzene under UV light was improved for 3.4times.In addition,the CaH₂ treated TiO₂ film has superior photocatalytic stability and high visible light transmittance,and it also has relatively high photocatalytic activity for the photodegradation of benzene under sunlight,indicating that it has the promising application on window glass for the purification of indoor VOCs.5.The light induced hydrophilicities of the TiO₂ films fabricated through different methods were measured.It was found that the TiO₂ film fabricated through PVP modified sol-gel method had light induced superhydrophilicity,after illumination under 300 W xenon lamp for 20 min,the contact angle of water on its surface was as low as 1.3°,illuminating that it has the promising application in the areas of self cleaning and anti fogging.