Synthesis Of Titania-based Composite Photocatalysts And Their Properties

Titania nanomaterials, because of their unique physical and chemical properties,such as chemical stability, corrosion resistance, non-toxic, low cost, are widely used,raging from ordinary products such as paint and sunscreen agents to photovoltaics,fuel cells and other cutting-edge technology.However,TiO2has a large band gap,which means its application in the visible range is limited. In other words, only UVlight can be utilized, which is accounting for less than5%in the energy density ofsunlight. This greatly inhibits the development of TiO2nanomaterials, and itsapplication is limited. Therefore, it is essential to explore simple modificationmethods to improve the optical response range of TiO2.We start from the preparationof mesoporous TiO2nanoparticles, which has the better morphology than other TiO2nanomaterials. Then we try two methods to improve the characteristic, doping silverand compounding semiconductor CdS.We combine sol-gel and solvothermal two commonly used methods to prepare pureanatase mesoporous structure TiO2nanoparticles, which is piled by smallparticles(m-TiO2). Controlling the size of titania beads by altering the hydrolysis andcondensation rates of the titanium alkoxide. While, we vary the amount ofhexadecylamine(HDA) to keep the monodispersity of the beads. The mesoporousTiO2beads have higher specific surface area and pore volume, which make theimprovement of photocatalytic performance possible.Compared with other noble metals, silver is low cost and non-toxic, hence we use the refluxing method to load Ag nanoparticles, forming a Ag/m-TiO2heterostructure.As we all know, the size of Ag particles has great affect on the photocatalyticproperties. We control the size and amount of Ag nanoparticles by adjusting theconcentration of [Ag(NH3)2]+ions that participating in the reaction. The smallparticles are not only hard to synthesis, but also easy to reunite. The analysis byXRD,SEM and TEM have demonstrated that Ag/m-TiO2we prepared by refluxingcan avoid this problem successfully. The Ag/m-TiO2heterostructure we synthesizedcan improve the photoresponsive properties and expand light absorption threshold.The test of photo-catalytic properties of Ag/m-TiO2prove when the amount of theAg is suitable the photocatalytic activity is much higher than pure TiO2nanomaterials.Then we analyze the photocatalytic mechanism of Ag/m-TiO2.In the fourth chapter, we synthesize CdS/m-TiO2heterostructure by hydrothermalmethod. Adjusting the loading amount by changing the amount of Cd（NO3）2andcysteine, ultimately we can control the size and uniformity. The analysis ofXRD,SEM and TEM can help find which sample has the best morphology. The CdS/m-TiO2heterostructure we synthesized can improve the photoresponsive propertiesand expand light absorption threshold. The test of photocatalytic properties of CdS/m-TiO2prove its photocatalytic activity is much higher than pure TiO2nanomaterials.Then we analyze the photocatalytic mechanism of CdS/m-TiO2.We demonstrate the synthesis of two titania-based photocatalysts via faile andeffective methods, overcoming some defects in properties and optimize several ofunique properties. It is proved that both two samples have superior photocatalyticactivity under visible light irradiation, expanding the scope of application of titaniumdioxide nanomaterials. It has great value for water purification and otherenvironmental issues.