Preparation And Performance Study Of Sn/Fe Doped TiO₂ Nanopowders

TiO₂ has been widely used in the fields of catalytic degradation of organic matter,wastewater treatment,air purification and solar cells due to its advantages of environmental protection,non-toxic,stable chemical properties and simple preparation methods.In order to further improve their overall photocatalytic activity,people have devoted themselves to preparing TiO₂-based photocatalysts with high photocatalytic performance in the past few decades.On the basis of developing a new preparation method,this paper aims to improve the photocatalytic activity of TiO₂ nano-powders by single doping and co-doping of Sn and Fe,supplemented by different additives,namely poloxam（F-127）and polyvinylpyrrolidone（K-30）.At the same time,the internal relations among the structure,morphology,composition and properties of the powder were studied.The specific content of the section is as follows:（1）In order to explore the influence of Sn doping on photocatalytic performance of TiO₂ nanopowders,the related properties of Sn O2 were investigated first.The crystals tructure,morphology and gas-sensitive performance of Sn O2 to ethanol gas was controlled by a novel one-pot evaporation combustion method and by adjusting the type of tin salt and the calcination temperature.Subsequently,the effect of Sn doping on the photocatalytic activity of TiO₂ nanoparticles was investigated by a novel volatile solid solution method.It was found that Sn doping could promote grain refinement and facilitate the transformation of anatase to rutile structure.The photocatalytic degradation of methyl orange using 17.7 at.%Sn doped TiO₂ nanopowders calcined at 380 ℃ was greatly improved to 61693.75 μg/g,being higher than that of other powders.（2）Fe-doped TiO₂ nanoparticles were successfully prepared by co-precipitation method.The results show that the photocatalytic efficiency of TiO₂ nanoparticles increased first and then decreased with the increase of calcination temperature.The formation of rutile TiO₂ can be inhibited by Fe doping,and the highest photocatalytic efficiency can be obtained when the Fe doping concentration was 0.1 at.%.On the basis of this study,Fe doped TiO₂ nanopowders were prepared by a modified sol-gel method supplemented with different additives,namely F-127 and K-30.The results show that the Fe-doped TiO₂ nanoparticles modified by F-127 can inhibit the transformation of anatase to rutile phase,and K-30 can act as the accelerator for this transformation.Under UV and visible light irradiation,Fe-doped TiO₂ nano-powders with F-127 and K-30 as additives showed higher photocatalytic degradation for methyl orange than those without additives.（3）Pure TiO₂ and Sn/Fe co-doped TiO₂ nanoparticles with different（Sn,Fe）: Ti molar ratio and calcination temperature were prepared by a sol-gel method.It is found that Sn/Fe co-doping can reduce the energy band gap of TiO₂ nanoparticles and increase the light absorption range correspondingly.It was observed that the inhibition behavior of anatase to rutile phase made the conversion temperature of anatase to pure rutile phase as high as750 ℃,being higher than that of pure TiO₂.After calcination at 650 ℃,0.6 at.% Fe and 0.2at.% Sn co-doped TiO₂ nanoparticles showed the best photocatalytic performance,which may be related to the decrease of the energy band gap and the formed mixed-phase of anatase and rutile.