Preparation And Photocatalytic Properties Of Brookite TiO₂ Based Nano-structured Materials

Nanostructured titanita?TiO₂?has attracted considerable interest due to its superior optical and electrical properties and has been found applications in many promising areas ranging from photovoltaics,photocatalysis,to sensors.In nature,TiO₂ exists mainly in three crystal phases: anatase?tetragonal?,rutile?tetragonal?,and brookite?orthorhombic?.Among the three main crystallographic forms of TiO₂,naturally metastable brookite is the least investigated in comparison with the comprehensively studied anatase and rutile phases because of the difficulties encountered in acquiring its pure form.Theoretical studies have demonstrated that brookite TiO₂ exhibits superior photocatalytic performance to anatase and rutile TiO₂ due to its unique orthorhombic crystalline structure.Recently,pure brookite TiO₂ has attracted more and more interests as an excellent candidate in photocatalytic applications.In this paper,photocatalytic activity and visible light response ability of brookite TiO₂ photocatalyst were improved by controlling the exposed crystal surface,morphology and band gap,which will providing a new way to develop novel TiO₂ photocatalytic materials.Main contents are shown as follows:Brookite TiO₂ nanosheets were synthesized via hydrothermal method using TiCl₄ and urea as reaction sources.The results showed that weakly basic environment was important for the formation of brookite,and increasing urea dosing facilitated crystal growth along?121?crystal plane.The as-synthesized brookite TiO₂ showed high photocatalytic activity and the decolorization rate of methylene blue?MB?was about 94.5% under UV light irradiation for 40 min,higher than commercial grade P25?86.7%?.Brookite TiO₂ with flower-like structures were prepared via hydrothermal method using TiCl₄ as titanium source and cetyltrimethylammonium bromide?CTAB?as a structure-directing agent.Na OH was introduced to control solution pH value.The morphology of products changed from spindle-like structures to flower-like structures with the increase of CTAB dosing.Brookite TiO₂ with quasi-spherical nanostructures were synthesized via solvothermal method using tetrabutyl titanate?Ti?OC₄H₉?₄,TBOT?as Ti source in the presence of oxalic acid.The results indicated that the formation of porous brookite TiO₂ was ascribed to the combined action of oxalic acid and pH value adjusted by sodium hydroxide.The sample synthesized at 200 ? for 12 h and followed by calcination at 500? for 2 h,showed the highest photocatalytic activity.The degradation rate of MB(10 mg·L^-1)reached to 96.7% under UV light irradiation for 90 min.Cu doped brookite TiO₂ was synthesized via solvothermal method,using tetrabutyl titanate and copper nitrate as reaction sources.The results showed that the sample doped by 7 wt% Cu showed the highest photodegradation rate to MB?about 87.0% under visible light irradiation for 90 min?,nearly 10% higher than that of pure brookite TiO₂ synthesized under the same conditions?78.0%?.