Study Of Microstructure Controlling And Property Of TiO₂ Photocatalytic Materials With Exposed （001） Facets

In this thesis,a series of different morphologies of TiO₂ with exposed（001）facets have been fabricated using hydrofluoric acid as capping agent,such as nanosheets,carambola-like and hexagonal prisms.The growth mechanism and influencing factors on morphologies were carefully explored.The photocatalytic performance by degradating methyl orange of all samples were studied and the influence factors were also analysed.The main contents could be summarized as follows:1.Anatase TiO₂ with exposed（001）facets were synthesized via solvothermal method by using titanium（IV）butoxide as Ti source,hydrofluoric acid as capping agent and alcohol as solvent.Different alcohols such as methanol,ethanol,isopropyl alcohol,and n-butanol were investigated systematically.The results indicated that samples obtained in methanol exhibite irregular morphologies,and TiO₂ nanosheets were created from ethanol,isopropanol alcohol and n-butanol.The effect of solvent on the morphology and properties of Ti O₂ crystals exposed（001）facets have been discussed.The photocatalysis investigation of samples was carried out by degradating methyl orange under ultraviolet light irradiation.TiO₂ nanosheets obtained in ethanol solvent exhibited superior photocatalytic performance compared with other samples.The reasons could attribute to TiO₂ nanosheets obtained in ethanol solvent with higher specific surface area and appropriate ratio of exposed highly active（001）facets.2.Carambola-like TiO₂ consisted of nanosheets with exposed（001）facet was synthesized via a one-step solvothermal method for the first time.The formation mechanism of the carambola-like TiO₂ was discussed by investigating the effect of reaction time,temperature and the volume of hydrofluoric acid.The results from different growth stages demonstrated that the formation of carambola-like TiO₂ included alcoholysis of precursor to nucleation,nuclei growth,dissolution-recrystallization growth and further growth.Reaction temperatures affected the morphologies and surface areas of carambola-like Ti O₂ samples.The photocatalytic performances of samples prepared at different temperature were tested.The carambola-like TiO₂ sample prepared at 160 oC exhibited the best photocatalytic activity.Such enhanced photocatalytic performance ascribed to the large surface area and the exposed（001）facets with high active.3.Anatase hexagonal prism TiO₂ with highly thermal stablity were prepared through the decomposition of precursors（HTi OF3）.HTiOF3 was firstly synthesized by a solvothermal method from n-octanol,tetrabutyl titanate and hydrofluoric acid.The obtained precipitates were then calcined at different temperature（200–900 oC）for 2 h.The formation process of hexagonal prism HTiOF3 precursors included three steps: nuclei,dissolution-recrystallization and further growth.The morphologies of precursors depended strongly on reaction time,reaction temperature and the amount of solvent.The precursors were transformed into TiO₂ after calcination and the effect of calcination temperature on the morphology and phase composition of hexagonal prism TiO₂ were investigated.The results indicated that anatase hexagonal prism TiO₂ exhibited a rather high thermal stability,maintaining both the anatase structure and hexagonal prism shape up to 800 oC.The sample calcined at 550 oC revealed superior photocatalytic performance.